Applied Surface Science (v.388, #PA)
Editorial Board (ii).
Preface by Peter Schaaf; Qiang Fu (1).
Thermal stability and chemical resistance of (Ti,Al)N-Cu and (Ti,Al)N-Ni metal-ceramic nanostructured coatings by D.S. Belov; I.V. Blinkov; A.O. Volkhonskii; D.V. Kuznetsov; F.V. Kiryukhantsev-Korneev; Yu. A. Pustov; V.S. Sergevnin (2-12).
This work represents the results of research on thermal stability, oxidation resistance at temperatures of up to 800 °C and electrochemical behaviour of (Ti,Al)N-(∼3 at.%)Cu and (Ti,Al)N-(∼8 at.%)Ni nanocrystalline coatings in acidic and alkaline media. The coatings were deposited by the arc-PVD method with a thickness of approximately 4 μm and crystallite size of less than 20 nm. It has been demonstrated that the composition and properties of the coating structures do not change when the coatings are heated in 10−4 Pa vacuum at temperatures of 600, 700 °C for 1.5 h. Heating up to 800 °C caused an increase of crystallite size and reduction microstrain in the crystal lattice of the ceramic phase. The process is accompanied by deterioration of the coating hardness from 48 to 52 to 33–36 GPa. The (Ti,Al)N-Cu and (Ti,Al)N-Ni metal-ceramic nanostructured coatings are characterized by heat resistance up to the temperatures of 700 and 800 °С respectively. The coatings under study have tendency for self-passivation and resistance to pitting corrosion.
Keywords: Nanostructured coating; Electrochemical behaviour; Metal-ceramic; Thermal stability; Heat resistance; arc-PVD;
Wear behaviour of wear-resistant adaptive nano-multilayered Ti-Al-Mo-N coatings by V.S. Sergevnin; I.V. Blinkov; A.O. Volkhonskii; D.S. Belov; D.V. Kuznetsov; M.V. Gorshenkov; E.A. Skryleva (13-23).
Coating samples in the Ti-Al-Mo-N system were obtained by arc-PVD method at variable bias voltage Ub applied to the substrate, and the partial pressure of nitrogen P(N2) used as a reaction gas. The deposited coatings were characterized by a nanocrystalline structure with an average grain size of 30–40 nm and multilayered architecture with alternating layers of (Ti,Al)N nitride and Mo-containing phases with a thickness comparable to the grain size. Coatings of (Ti,Al)N-Mo-Mo2N and (Ti,Al)N-Mo2N compositions were obtained by changing deposition parameters. The obtained coatings had hardness of 40 GPa and the relative plastic deformation under microindentation up to 60%. (Ti,Al)N-Mo2N coatings demonstrated better physicomechanical characteristics, showing high resistance to crack formation and destruction through the plastic deformation mechanism without brittle fracturing, unlike (Ti,Al)N-Mo-Mo2N. The friction coefficient of the study coatings (against Al2O3 balls under dry condition using a pin-on-disc method) reached the values of 0.35 and 0.5 at 20 °C and 500 °C respectively, without noticeable wear within this temperature range. These tribological properties were achieved by forming MoO3 acting as a solid lubricant. At higher temperatures the deterioration in the tribological properties is due to the high rate of MoO3 sublimation from friction surfaces.
Keywords: Arc-PVD; Wear resistance; Adaptive coatings; Tribology; Nanostructure;
MRI-aided tissues interface characterization: An accurate signal propagation time calculation method for UWB breast tumor imaging by Liang Wang; Xia Xiao; Takamaro Kikkawa (24-34).
Radar-based ultrawideband (UWB) microwave imaging is expected to be a safe, low-cost tool for breast cancer detection. However, since radar wave travels at different speeds in different tissues, propagation time is hard to be estimated in heterogeneous breast. Wrongly estimated propagation time leads to error of tumor location in resulting image, aka imaging error. In this paper, we develop a magnetic resonance imaging-aided (MRI-aided) propagation time calculation technique which is independent from radar imaging system but can help decrease the imaging error. The technique can eliminate the influence of the rough interface between fat layer and gland layer in breast and get relative accurate thicknesses of two layers. The propagation time in each layer is calculated and summed. The summed propagation time is used in Confocal imaging algorithm to increase the accuracy of resulting image. 25 patients’ breast models with glands of varying size are classified into four categories for imaging simulation tests. Imaging accuracy in terms of tumor location along x-direction has been improved for 21 among 25 cases, as a result, overall around 50% improvement compared to conventional UWB imaging.
Keywords: Ultrawideband (UWB) microwave imaging; Breast cancer detection; Magnetic resonance imaging-aided (MRI-aided); Propagation time; Tissues interface;
Enhanced ferroelectric and piezoelectric properties of (1-x)BaZr0.2Ti0.8O3–xBa0.7Ca0.3TiO3 thin films by sol–gel process by Ling Huang; Ying Dai; Yaxiong Wu; Xinmei Pei; Wen Chen (35-39).
Lead free (1-x)BaZr0.2Ti0.8O3–xBa0.7Ca0.3TiO3 (BZT–xBCT) thin films were successfully deposited on Pt/Ti/SiO2/(100)Si substrates via the sol–gel process. Both structural and electric properties of the thin films demonstrated the strong composition dependence. The BZT–xBCT thin film with x = 0.3 exhibited excellent electric properties with a large piezoelectric coefficient, d33 of 280 pm/V and a high remnant polarization, Pr of 12 μC/cm2. The enhanced ferroelectric and piezoelectric properties of BZT–xBCT thin films were primarily attributed to the composition close to the triple point of the morphotropic phase boundaries (MPB) system, where the coexisting of rhombohedral and tetragonal phases takes place.
Keywords: BZT-xBCT thin films; Ferroelectric; Piezoelectric; Sol–gel process;
Tribo-chemical behavior of eutectoid steel during rolling contact friction by Y. Zhou; Z.B. Cai; J.F. Peng; B.B. Cao; X.S. Jin; M.H. Zhu (40-48).
The tribo-chemical behavior of the eutectoid steel during rolling contact friction is investigated via scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and electron probe X-ray microanalysis. The worn surface is divided into three zones: matrix zone (without friction), tribo-film zone (formed during friction) and delamination zone (tribo-film spalling). The different chemical states of atoms between those three zones and the air were investigated using the XPS analysis. The results showed that the matrix zone is composed of Fe2O3, FeO and metallic Fe, while the tribo-film and delamination zones only contain Fe2O3 and FeO. Where the tribo-film is formed, the absorptive ability of O and C atoms on the top 2–3 atomic layers is probably weakened, while the exposed fresh metal in the delamination zone tends to be continuously oxidized and form tribo-film. The tribo-chemical reaction in the delamination zone is more activated than that in the other two zones. The protective nature of the tribo-film probably maintains a low friction coefficient under rolling contact friction condition.
Keywords: XPS; Tribo-chemical; Rolling contact friction; Eutectoid steel; Tribo-film;
Electrochemically enhanced surface plasticity of steels by E.M. Gutman; Ya. Unigovski; R. Shneck; F. Ye; Y. Liang (49-56).
There are serious problems with the formability of alloys which are relatively hard and brittle below ambient temperatures, e.g., in cold extrusion and drawing processes. It is known that electrochemical surface treatment can decrease residual stresses and hardness of the surface layer as a result of the chemomechanical effect (CME), and also improve the plastic deformation ability, e.g., deep drawing of high-strength alloys. Plastic deformation ability of materials can be characterized by hardness measurements. The present study shows some possibilities to improve the surface ductility of carbon steels and FeSi6.5 steel under anodic polarization depending on the current density, composition and pH of acids and chloride electrolytes. The relative Vickers hardness (RVH) amounting to a squared ratio of the penetration depth of a cone indenter in air as compared to that in a solution (hair /hsol )2 was found as a function of the current density and the electrolyte composition. A decrease in hardness of the surface layer as a result of anodic electrochemical polarization was found for different steels.
Keywords: Hardness; Surface plasticity; Anodic polarization; Electrolyte;
Questing and the application for silicon based ternary compound within ultra-thin layer of SIS intermediate region by Shumin Chen; Ming Gao; Yazhou Wan; Huiwei Du; Yong Li; Zhongquan Ma (57-63).
A silicon based ternary compound was supposed to be solid synthesized with In, Si and O elements by magnetron sputtering of indium tin oxide target (ITO) onto crystal silicon substrate at 250 °C. To make clear the configuration of the intermediate region, a potential method to obtain the chemical bonding of Si with other existing elements was exploited by X-ray photoelectron spectroscopy (XPS) instrument combined with other assisted techniques. The phase composition and solid structure of the interfacial region between ITO and Si substrate were investigated by X-ray diffraction (XRD) and high resolution cross sectional transmission electron microscope (HR-TEM). A photovoltaic device with structure of Al/Ag/ITO/SiOx/p-Si/Al was assembled by depositing ITO films onto the p-Si substrate by using magnetron sputtering. The new matter has been assumed to be a buffer layer for semiconductor-insulator-semiconductor (SIS) photovoltaic device and plays critical role for the promotion of optoelectronic conversion performance from the view point of device physics.
Keywords: XPS; Si based compound; Interface states; SIS device;
Detection and distribution of lithium in Mg-Li-Al based alloy by ToF-SIMS by Vinod Kumar (64-70).
Display OmittedTime of Flight-Secondary Ion Mass Spectrometry (ToF-SIMS) is used to investigate the surface as well as bulk microstructural features of novel Mg-Li-Al based alloy namely Mg-9Li-7Al-3Sn-1Zn (LATZ9531). ToF-SIMS study indicates that there are six multi-oxide layers present within the surface film of LATZ9531. Furthermore, The presence of Li containing phase has been qualitatively confirmed based on the high number of Li-ion counts in SIMS, and the same is verified quantitatively by using electron probe microanalysis (EPMA). The novel approach may be useful to determine the chemical composition of the phases in various alloys which has lighter alloying elements such as lithium.
Keywords: Magnesium; ToF-SIMS; Microstructure; Oxide; Mg-Li alloy;
Fabrication and sulfurization of Cu2SnS3 thin films with tuning the concentration of Cu-Sn-S precursor ink by Chi-Jie Wang; Shih-Chang Shei; Shih-Chang Chang; Shoou-Jinn Chang (71-76).
In this study, Cu-Sn-S nanoinks were synthesized by combining chelating polyetheramine to Cu, Sn, S powders of various concentrations. X-ray diffraction patterns indicate that nanoinks synthesized at low concentrations are composed almost entirely of binary phases SnS and Cu2S. Synthesizing nanoinks at higher concentrations decreased the quantity of binary phase and led to the appearance of ternary phase Cu4SnS4. Following sulfurization, single phase Cu2SnS3 (CTS) thin film was obtained from nanoinks of low concentration; however, impurities, such as Cu2S were detected in the thin film obtained from nanoinks of high concentration. This can be attributed to the fact that lower concentrations reduce the reactivity of all the elements. As a result, the SnS phase reacted more readily and more rapidly, resulting in the early formation of a stoichiometric CTS thin film during sulfurization. Under these reaction conditions, Cu2S and SnS transform into CTS and thereby prevent the formation of unwanted phases of Cu2S and Cu4SnS4. Raman spectra revealed that second phase Cu2S phase remained in the high-concentration samples, due to an increase in reactivity due to the participation of a greater proportion of the copper in the reaction. The surface microstructure of low-concentration samples display closely packed Cu2SnS3 grains with a flat morphology and an atomic composition ratio of Cu:Sn:S = 34.69:15.90:49.41, which is close to stoichiometric. Hall measurement revealed that low-concentration sample has superior electrical properties; i.e., a hole concentration of 5.23 × 1017 cm−3, mobility of 14.2 cm2/V-s, and optical band-gap energy of 1.346 eV, which are suitable for thin-film solar cells.
Keywords: Sulfurization; Cu2SnS3; Thin films; Precursor;
Effect of target density on the growth and properties of YGBCO thin films deposited by pulsed laser deposition by Linfei Liu; Yiejie Li; Xiang Wu; Yanjie Yao; Menglin Wang; Binbin Wang (77-81).
Some works found that target density had not a large effects on the superconducting or structural properties of YBa2Cu3O7-δ (YBCO) films prepared by pulsed laser deposition. However, the possible effect of target density on the Y0.5Gd0.5Ba2Cu3O7-δ (YGBCO) is not clear. In this paper, YGBCO thin films were deposited on flexible metal substrates by pulsed laser deposition using target with different densities. The density of each YGBCO target was varied from to 4.0 g/cm3 to 5.5 g/cm3. The aim of this study was to determine the relationship between the microstructure and superconducting properties of YGBCO films as a function of the target density. The film structures were examined by X-ray diffraction and field emission scanning electron microscopy. The superconducting properties of the YGBCO films were evaluated using the conventional four-probe method and PPMS. It was found that all the YGBCO films had pure c-axis orientation. The target density had effect on the surface morphology and superconducting properties of the YGBCO thin films. With increasing target density, the pore became larger and the distribution density and size of the particles became higher and larger, and the critical current Ic decreased. The YGBCO film deposited at a target density of 4.0 g/cm3 exhibited the highest critical current density Jc of 5.4 MA/cm2 at 77 K and self-field, 47.2 MA/cm2 at 0 T and 8.8 MA/cm2 at 9 T at 4.2 K and B//c.
Keywords: YGBCO; PLD; Target density; Microstructure; Superconducting properties;
Influence of different TiO2 blocking films on the photovoltaic performance of perovskite solar cells by Chenxi Zhang; Yudan Luo; Xiaohong Chen; Wei Ou-Yang; Yiwei Chen; Zhuo Sun; Sumei Huang (82-88).
Organolead trihalide perovskite materials have been successfully used as light absorbers in efficient photovoltaic (PV) cells. Cell structures based on mesoscopic metal oxides and planar heterojunctions have already demonstrated very impressive and brisk advances, holding great potential to grow into a mature PV technology. High power conversion efficiency (PCE) values have been obtained from the mesoscopic configuration in which a few hundred nano-meter thick mesoporous scaffold (e.g. TiO2 or Al2O3) infiltrated by perovskite absorber was sandwiched between the electron and hole transport layers. A uniform and compact hole-blocking layer is necessary for high efficient perovskite-based thin film solar cells. In this study, we investigated the characteristics of TiO2 compact layer using various methods and its effects on the PV performance of perovskite solar cells. TiO2 compact layer was prepared by a sol-gel method based on titanium isopropoxide and HCl, spin-coating of titanium diisopropoxide bis (acetylacetonate), screen-printing of Dyesol’s bocking layer titania paste, and a chemical bath deposition (CBD) technique via hydrolysis of TiCl4, respectively. The morphological and micro-structural properties of the formed compact TiO2 layers were characterized by scanning electronic microscopy and X-ray diffraction. The analyses of devices performance characteristics showed that surface morphologies of TiO2 compact films played a critical role in affecting the efficiencies. The nanocrystalline TiO2 film deposited via the CBD route acts as the most efficient hole-blocking layer and achieves the best performance in perovskite solar cells. The CBD-based TiO2 compact and dense layer offers a small series resistance and a large recombination resistance inside the device, and makes it possible to achieve a high power conversion efficiency of 12.80%.
Keywords: Perovskite solar cell; Compact layer; Titanium dioxide; Chemical bath deposition; Sol-gel; Spin-coating;
Preparation and photovoltaic properties of perovskite solar cell based on ZnO nanorod arrays by Yang Xu; Tian Liu; Zhaosong Li; Bingjie Feng; Siqian Li; Jinxia Duan; Cong Ye; Jun Zhang; Hao Wang (89-96).
Display OmittedA careful control of ZnO nanorod arrays with various densities and thickness were achieved by hydrothermal method. An obvious increase in the ZnO nanorod density is observed as the concentrations of zinc acetate dropped as expected through the surface SEM images. On the other hand, samples with and without TiO2 compact layer were also studied and results had been analyzed to seek for an optimized substrate structure for light absorbing layer and increase the efficiency. What’s more, a deep research for the drying temperature for perovskite layer was also conducted. As a result, SEM images discribe a promising surface appearance of perovskite layer which is finely attached onto the nanorod structure. Final power conversion efficiency (PCE) of FTO/ZnO seed layer/ZnO nanorods/perovskite/spiro-OMe-TAD/Au electrode photovoltaic device reached ∼9.15% together with open-circuit voltage of 957 mV, short-circuit current density of 17.8 mA/cm2 and fill factor of 0.537.
Keywords: ZnO nanorod; Perovskite solar cell; Drying temperature; Rod density; Rod thickness;
Surface and edge electroluminescence study of as-grown VCSEL structures by Yongming Zhao; Yurun Sun; Yang He; Shuzhen Yu; Yan Song; Jianrong Dong (97-102).
We present a simple quick evaluation method on vertical-cavity-surface-emitting laser (VCSEL) structures, which is designed for atomic clock working at high temperature (>350 K), to determine the temperature at which the wavelength of the VCSEL cavity mode (CM) aligns with that of the quantum well (QW) gain peak. The surface and edge electroluminescence (EL) measurements were performed non-destructively on pieces of as-grown VCSEL structures by employing soldered indium (In) contacts. The surface EL spectra determine the CM position, while the edge EL spectra are used to identify the wavelength of ground-state emission from the QW in the active region (QW gain peak). The room temperature EL measurements from a cleaved edge of the VCSEL structures indicate that the QW gain peak is at ∼780.5 nm, while the CM measured in the VCSEL surface emission EL peak (sample B) is at ∼793 nm. When the sample is heated up, the amount of CM shift with temperature can be fitted with Δ λ CM = T × 0.068 nm / K , also corroborated by temperature dependence surface reflectivity measurement, and the gain peak can be fitted with λ QW peak = 780.5 nm + T × 0.26 nm / K . The CM and QW gain peak of sample B will be brought into alignment at ∼365 K by fitting curve and this was confirmed by measurement. In summary, the surface and edge EL measurements using soldered In as electrodes can be very useful for post growth non-destructive characterization of VCSELs at different temperature.
Keywords: Vertical cavity surface emitting lasers; Atomic clock; Cavity mode; Quantum well;
Wear resistance of TiN(Ti2N)/Ti composite layer formed on C17200 alloy by plasma surface Ti-alloying and nitriding by L. Liu; H.H. Shen; X.Z. Liu; Q. Guo; T.X. Meng; Z.X. Wang; H.J. Yang; X.P. Liu (103-108).
The duplex treatment of plasma Ti-alloying and plasma nitriding was applied on the surface of C17200 alloy to improve its wear resistance. C17200 substrate was alloyed with Ti using double glow plasma alloying to form a Ti-alloyed layer in its surface, and then treated by plasma nitriding to make a TiN(Ti2N) alloying layer based on the Ti-alloyed surface. The microstructure and formation mechanism were studied by using GDOES, XRD and SEM. The hardness, tribological property and electrical conductivity of C17200 alloy after plasma alloying and nitriding were investigated by mean of micro-hardness tester, friction and wear testers as well as impedance analyzers. Modulus of elasticity and the adhesive strength of TiN(Ti2N)/Ti composite layer were evaluated by nano-indenter and scratch tester. The result shows that a TiN(Ti2N)-Ti-Be-Cu composite layer with a thickness of 27 μm is formed in the C17200 surface and is mainly composed of TiN, Ti2N, Cu(Ti) solid solution, etc. The composite alloying surface consists of the hard TiN(Ti2N)-rich layer on the top surface and Ti-Cu-Be diffusion layer, showing a strong adhesive strength with the C17200 substrate and a little decrease in the modulus of elasticity. A certain amount of Cu and Be together with TiN/Ti2N exists in the outmost, resulting in a better combination of wear resistance and conductive performance.
Keywords: C17200 alloy; Double glow plasma alloying; Plasma nitriding; Wear resistance; Conductivity;
Anisotropic surface hole-transport property of triphenylamine-derivative single crystal prepared by solution method by Minoru Umeda; Mitsuhiko Katagiri; Sayoko Shironita; Norio Nagayama (109-113).
This paper reports the anisotropic hole transport at the triphenylamine-derivative single crystal surface prepared by a solution method. Triphenylamine derivatives are commonly used in a hole-transport material for organic photoconductors of laser-beam printers, in which the materials are used as an amorphous form. For developing organic photovoltaics using the photoconductor’s technology, preparation of a single crystal seems to be a specific way by realizing the high mobility of an organic semiconductor. In this study, a single crystal of 4-(2,2-diphenylethenyl)-N,N-bis(4-methylphenyl)-benzenamine (TPA) was prepared and its anisotropic hole-transport property measured. First, the hole-transport property of the TPA was investigated based on its chemical structure and electrochemical redox characteristics. Next, a large-scale single crystal formation at a high rate was developed by employing a solution method based on its solubility and supersolubility curves. The grown TPA was found to be a single crystal based on the polarization micrograph observation and crystallographic analysis. For the TPA single crystal, an anisotropic surface conduction was found, which was well explained by its molecular stack structure. The measured current in the long-axis direction is one order of magnitude greater than that of amorphous TPA.
Keywords: Hole transport molecule; Organic single crystal; High-rate crystal growth; Anisotropic surface conductivity;
Structure and in vitro bioactivity of ceramic coatings on magnesium alloys by microarc oxidation by Huijun Yu; Qing Dong; Jinhe Dou; Yaokun Pan; Chuanzhong Chen (114-119).
Magnesium and its alloys have the potential to serve as lightweight, degradable, biocompatible and bioactive orthopedic implants for load-bearing applications. However, severe local corrosion attack and high corrosion rate have prevented their further clinical use. Micro-arc oxidation (MAO) is proved to be a simple, controllable and efficient electrochemistry technique that can prepare protective ceramic coatings on magnesium alloys. In this paper, electrolyte containing silicate salts was used for microarc oxidation to form ceramic bioactive coatings on the ZK61 alloy substrate. The structure characteristics and element distributions of the coating were investigated by XRD, TEM, SEM and EPMA. The MAO samples were immersed in simulated body fluid (SBF) for 7 and 14 days, respectively. The surface characteristic of the immersed coatings was investigated by Fourier-transform infrared (FTIR) spectroscopy. The results show that these MAO coatings have low crystallinity and are mainly composed of MgO, Mg2SiO4 and Mg2Si2O6. The coating surface is porous. During the SBF immersion period, the nucleation and precipitation of bone-like apatites occur on the MAO coating surface. The corrosion resistance of the substrate is improved by the MAO coatings.
Keywords: Magnesium alloy; Micro-arc oxidation; Coating structure; Bioactivity; Simulated body fluid;
Wannier–Stark electro-optical effect, quasi-guided and photonic modes in 2D macroporous silicon structures with SiO2 coatings by L. Karachevtseva; Yu. Goltviansky; O. Sapelnikova; O. Lytvynenko; O. Stronska; Wang Bo; M. Kartel (120-125).
Opportunities to enhance the properties of structured surfaces were demonstrated on 2D macroporous silicon structures with SiO2 coatings. We investigated the IR light absorption oscillations in macroporous silicon structures with SiO2 coatings 0–800 nm thick. The Wannier–Stark electro-optical effect due to strong electric field on Si-SiO2boundary and an additional electric field of quasi-guided optical modes were taken into account. The photonic modes and band gaps were also considered as peculiarities in absorbance spectra of macroporous silicon structures with a thick SiO2 coating. The photonic modes do not coincide with the quasi-guided modes in the silicon matrix and do not appear in absorption spectra of 2D macroporous silicon structures with surface nanocrystals.
Keywords: Macroporous silicon; Wannier–Stark effect; Quasi-guided and photonic modes;
Zr/ZrC modified layer formed on AISI 440B stainless steel by plasma Zr-alloying by H.H. Shen; L. Liu; X.Z. Liu; Q. Guo; T.X. Meng; Z.X. Wang; H.J. Yang; X.P. Liu (126-132).
The surface Zr/ZrC gradient alloying layer was prepared by double glow plasma surface alloying technique to increase the surface hardness and wear resistance of AISI 440B stainless steel. The microstructure of the Zr/ZrC alloying layer formed at different alloying temperatures and times as well as its formation mechanism were discussed by using scanning electron microscopy, glow discharge optical emission spectrum, X-ray diffraction and X-ray photoelectron spectroscopy. The adhesive strength, hardness and tribological property of the Zr/ZrC alloying layer were also evaluated in the paper. The alloying surface consists of the Zr-top layer and ZrC-subsurface layer which adheres strongly to the AISI 440B steel substrate. The thickness of the Zr/ZrC alloying layer increases gradually from 16 μm to 23 μm with alloying temperature elevated from 900 °C to 1000 °C. With alloying time from 0.5 h to 4 h, the alloyed depth increases from 3 μm to 30 μm, and the ZrC-rich alloyed thickness vs time is basically parabola at temperature of 1000 °C. Both the hardness and wear resistance of the Zr/ZrC alloying layer obviously increase compared with untreated AISI 440B steel.
Keywords: Plasma surface alloying; Martensitic stainless steel; ZrC; Microstructure; Hardness; Wear resistance;
Surface hydrophilic modification of acrylonitrile-butadiene-styrene terpolymer by poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate): Preparation, characterization, and properties studies by Tingting Chen; Jun Zhang (133-140).
Display OmittedSurface hydrophilic modified acrylonitrile-butadiene-styrene (ABS) terpolymer was prepared by melt blending with poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG) random copolymer as the modifier. Attenuated total reflectance-Fourier transform-infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) were used for surface analysis. Through the contact angle measurement, the relationship between surface properties of the ABS/PETG blends and PETG content was investigated. Scanning electron microscope (SEM) and dynamical mechanical thermal analysis (DMTA) were used to characterize interface morphology and compatibility of the blends. The effect of PETG content on the mechanical and rheological properties was examined. The ATR-FTIR and XPS analysis suggested that the hydrophilic groups were enriched on the surface with increasing PETG content in the blend. The decrease of the water contact angle and the increase of the polarity for the blends with increasing PETG content indicated that the hydrophilic property of the blends was enhanced with increasing PETG content. The ABS/PETG blends were partially miscible. And the blends with ≤50 wt% PETG had better compatibility than the blends with above 50 wt% PETG. It was clear that below 50 wt% PETG, the PETG phase was dispersed in spherical form and the ABS phase was continuous. Above 50 wt% PETG, the PETG phase became continuous and the ABS phase was dispersed in irregular form. Moreover, the tensile strength and flexural strength of the blends were enhanced with increasing PETG content. The flexural modulus almost remained constant. And the impact strength was decreased when the content of PETG was increasing.
Keywords: Contact angle; Surface free energy; Hydrophilic property; Morphology; Compatibility;
The compositional, structural, and magnetic properties of a Fe3O4/Ga2O3/GaN spin injecting hetero-structure grown by metal-organic chemical vapor deposition by Zhonghua Xu; Shimin Huang; Kun Tang; Shulin Gu; Shunming Zhu; Jiandong Ye; Mingxiang Xu; Wei Wang; Youdou Zheng (141-147).
In this article, the authors have designed and fabricated a Fe3O4/Ga2O3/GaN spin injecting hetero-structure by metal-organic chemical vapor deposition. The compositional, structural, and magnetic properties of the hetero-structure have been characterized and discussed. From the characterizations, the hetero-structure has been successfully grown generally. However, due to the unintentional diffusion of Ga ions from Ga2O3/GaN layers, the most part of the nominal Fe3O4 layer is actually in the form of Ga x Fe3−x O4 with gradually decreased x values from the Fe3O4/Ga2O3 interface to the Fe3O4 surface. Post-annealing process can further aggravate the diffusion. Due to the similar ionic radius of Ga and Fe, the structural configuration of the Ga x Fe3−x O4 does not differ from that of pure Fe3O4. However, the ferromagnetism has been reduced with the incorporation of Ga into Fe3O4, which has been explained by the increased Yafet-Kittel angles in presence of considerable amount of Ga incorporation. A different behavior of the magnetoresistance has been found on the as-grown and annealed samples, which could be modelled and explained by the competition between the spin-dependent and spin-independent conduction channels. This work has provided detailed information on the interfacial properties of the Fe3O4/Ga2O3/GaN spin injecting hetero-structure, which is the solid basis for further improvement and application of the structure.
Keywords: Fe3O4; Ga2O3; GaN; MOCVD; Spintronics;
Preparation of Si-containing oxide coating and biomimetic apatite induction on magnesium alloy by Huijun Yu; Qing Dong; Jinhe Dou; Yaokun Pan; Chuanzhong Chen (148-154).
Magnesium and its alloys are recently found important in the field of bone repairing for their ideal mechanical performance and excellent biocompatibility. Micro-arc oxidation (MAO) is a simple, controllable and efficient electrochemistry method that can prepare protective ceramic coatings on magnesium alloys. The properties of the MAO coating, such as thickness, microstructure, roughness and composition, can easily be controlled by adjusting the voltage, current density, duration or the electrolyte concentration. In this work, MAO coatings are prepared on ZK61 magnesium alloy at different voltages. The structure characteristics and element distributions of the coating are investigated by XRD, TEM, SEM and EPMA. The MAO samples are immersed in SBF for 7, 14 and 28 days respectively. The corrosion behaviors of the samples in SBF were also investigated by potentiodynamic polarization curves. The corrosion products were characterized by EDS and FT-IR. The MAO coated ZK61 alloy samples showed excellent corrosion resistance and bioactivity. The MAO method demonstrates a great potential in the preparation of degradable and bioactive orthopedic magnesium-based implants.
Keywords: Micro-arc oxidation; Magnesium alloy; Coating; Corrosion resistance; Bioactivity;
Investigation of optical properties of Cu/Ni multilayer nanowires embedded in etched ion-track template by Lu Xie; Huijun Yao; Jinglai Duan; Yonghui Chen; Shuangbao Lyu; Khan Maaz; Dan Mo; Jie Liu; Youmei Sun; Mingdong Hou (155-159).
The schematic diagram of measurement of extinction spectra of Cu/Ni multilayer nanowire arrays embedded in the template after removing the gold/copper substrate.For understanding the interaction between light and noble/magnetism multilayer nanowires, Cu/Ni multilayer nanowires are fabricated by a multi-potential step deposition technique in etched ion-track polycarbonate template. The component and the corresponding layer thickness of multilayer nanowire are confirmed by TEM and EDS line-scan analysis. By tailoring the nanowire diameter, the Cu layer thickness and the periodicity of the nanowire, the extinction spectral of nanowire arrays exhibit an extra sensitivity to the change of structural parameters. The resonance wavelength caused by surface plasmon resonance increases obviously with increasing the nanowire diameter, the Cu layer thickness and the periodicity. The observations in our work can be explained by the “impurity effect” and coupled effect and can also be optimized for developing optical devices based on multilayer nanowires.
Keywords: Multilayer nanowires; Surface plasmon resonance; Optical properties; Electrochemical deposition;
Corrosion studies using potentiodynamic and EIS electrochemical techniques of welded lean duplex stainless steel UNS S82441 by Z. Brytan; J. Niagaj; Ł. Reiman (160-168).
The corrosion characterisation of lean duplex stainless steel (1.4662) UNS S82441 welded joints using the potentiodynamic test and electrochemical impedance spectroscopy in 1 M NaCl solution are discussed. The influence of autogenous TIG welding parameters (amount of heat input and composition of shielding gases like Ar and Ar–N2 and an Ar–He mixture), as well as A-TIG welding was studied. The influence of welding parameters on phase balance, microstructural changes and the protective properties of passive oxide films formed at the open circuit potential or during the anodic polarisation were studied.From the results of the potentiodynamic test and electrochemical impedance spectroscopy of TIG and A-TiG, welded joints show a lower corrosion resistance compared to non-welded parent metal, but introducing heat input properly during welding and applying shielding gases rich in nitrogen or helium can increase austenitic phase content, which is beneficial for corrosion resistance, and improves surface oxide layer resistance in 1 M NaCl solution.
Keywords: Lean duplex stainless steel; Potentiodynamic test; EIS; TIG; A-TIG;
Using Ag-embedded TiO2 nanotubes array as recyclable SERS substrate by Yunhan Ling; Yuqing Zhuo; Liang Huang; Duolu Mao (169-173).
A simple strategy for synthesizing Ag-loaded TiO2 nanotube film for use as multifunctional photocatalyst and recyclable surface-enhanced Raman scattering (SERS) substrate is introduced. Highly aligned TiO2 nanotube arrays (TNTA) prepared via electrochemical anodization were used as a 3D rough host for silver nanoparticles. Ag deposits were sputtered in a vacuum, and it was found that their morphologies were mainly influenced by the diameters of nanotubes and the UV irradiation induced aging process, especially the self-migration of silver along the tubular wall. SERS and the self-cleaning effect were observed using Rhodamine 6G (R6G) as the probe molecule. The results showed that narrow nanotube and silver nanoparticles embedment contributed significantly to both the phenomenal SERS and recyclability.
Keywords: TiO2 nanotubes array; Surface-enhanced Raman scattering (SERS); Silver nanoparticle; Photocatalysis; Self-cleaning;
Computer simulation of the relationship between selected properties of laser remelted tool steel surface layer by Mirosław Bonek; Agata Śliwa; Jarosław Mikuła (174-179).
Investigations >The language in this paper has been slightly changed. Please check for clarity of thought, and that the meaning is still correct, and amend if necessary.include Finite Element Method simulation model of remelting of PMHSS6-5-3 high-speed steel surface layer using the high power diode laser (HPDL). The Finite Element Method computations were performed using ANSYS software. The scope of FEM simulation was determination of temperature distribution during laser alloying process at various process configurations regarding the laser beam power and method of powder deposition, as pre-coated past or surface with machined grooves. The Finite Element Method simulation was performed on five different 3-dimensional models. The model assumed nonlinear change of thermal conductivity, specific heat and density that were depended on temperature. The heating process was realized as heat flux corresponding to laser beam power of 1.4, 1.7 and 2.1 kW. Latent heat effects are considered during solidification. The molten pool is composed of the same material as the substrate and there is no chemical reaction. The absorptivity of laser energy was dependent on the simulated materials properties and their surface condition. The Finite Element Method simulation allows specifying the heat affected zone and the temperature distribution in the sample as a function of time and thus allows the estimation of the structural changes taking place during laser remelting process. The simulation was applied to determine the shape of molten pool and the penetration depth of remelted surface. Simulated penetration depth and molten pool profile have a good match with the experimental results. The depth values obtained in simulation are very close to experimental data. Regarding the shape of molten pool, the little differences have been noted. The heat flux input considered in simulation is only part of the mechanism for heating; thus, the final shape of solidified molten pool will depend on more variables.
Keywords: Computer simulation; Finite Element Method; Laser remelting; High-speed tool steel;
Interface chemistry of CdZnTe films studied by a peel-off approach by Jun Tao; Haitao Xu; Yuelu Zhang; Huanhuan Ji; Run Xu; Jian Huang; Jijun Zhang; Xiaoyan Liang; Ke Tang; Linjun Wang (180-184).
CdZnTe films with thickness above 50 μm were deposited at temperatures of 200–500 °C by Close Space Sublimation method. A peel-off approach has been adopted to study the interface chemistry of CdZnTe thick films. For all the CdZnTe films, the scanning electron microscopy images show the small and round-like grains formed at interface in contrast to the large ordered grains at surface. For CdZnTe films grown at a low substrate temperature of 200 °C, the interface layer between CdZnTe and substrate is mixed with Te and CdTe, as evidenced by X-ray diffraction, Raman and X-ray photoelectron spectroscopy results. The thickness of the interface layer can be estimated to be 84 nm by depth profile using X-ray photoelectron spectroscopy. In contrast, a thin interface layer less than 14 nm is found at a high substrate temperature of 500 °C. The limited reaction of Te2 and Cd (Zn) to CdZnTe at a low growth temperature is responsible for the formation of the thick interface layer and a slow deposition rate at the nucleation stage.
Keywords: CdZnTe thick film; Interface; A peel-off approach; Close Space Sublimation;
Microstructural evolution and surface properties of nanostructured Cu-based alloy by ultrasonic nanocrystalline surface modification technique by Auezhan Amanov; In-Sik Cho; Young-Sik Pyun (185-195).
A nanostructured surface layer with a thickness of about 180 μm was successfully produced in Cu-based alloy using an ultrasonic nanocrystalline surface modification (UNSM) technique. Cu-based alloy was sintered onto low carbon steel using a powder metallurgy (P/M) method. Transmission electron microscope (TEM) characterization revealed that the severe plastic deformation introduced by UNSM technique resulted in nano-sized grains in the topmost surface layer and deformation twins. It was also found by atomic force microscope (AFM) observations that the UNSM technique provides a significant reduction in number of interconnected pores. The effectiveness of nanostructured surface layer on the tribological and micro-scratch properties of Cu-based alloy specimens was investigated using a ball-on-disk tribometer and micro-scratch tester, respectively. Results exhibited that the UNSM-treated specimen led to an improvement in tribological and micro-scratch properties compared to that of the sintered specimen, which may be attributed to the presence of nanostructured surface layer having an increase in surface hardness and reduction in surface roughness. The findings from this study are expected to be implemented to the automotive industry, in particular connected rod bearings and bushings in order to increase the efficiency and performance of internal combustion engines (ICEs).
Keywords: Cu-based alloy; Nanostructured surface; Friction; Wear; UNSM;
Effects of surface tension and viscosity on the forming and transferring process of microscale droplets by Shulei Chen; Kun Liu; Cunbin Liu; Dongyang Wang; Dechun Ba; Yuanhua Xie; Guangyu Du; Yaoshuai Ba; Qiao Lin (196-202).
Surface tension and viscosity act as important roles on the fluid flow in microchannel channels. In order to understand the influencing mechanism, three dimensional numerical simulations as well as experimental investigations were carried out on the slug formation and transfer in a rectangle T-junction microchannel. The simulation showed that the increasing Capillary number (Ca) resulted in the decreasing slug volume. Due to the existence of film thickness and corner flow, the characteristic length of slug was not the same trend completely. The results also showed that the pressure of junction point fluctuated periodically in the process of slug formation, which can reflect the slug formation period and the effect of the various conditions on pressure change. Two other pressure monitoring points were located in vertical channel and main channel and they monitored the pressure of two phase flow respectively. The increasing surface tension resulted in an increasing of total pressure, the interface pressure drop of two phases and the period of slug formation. The frequency of slug formation and two phases total pressure increased with the viscosity of continuous phase.
Keywords: Numerical simulation; Liquid–liquid flow; Surface tension; Viscosity; Pressure drop; VOF method;
Improving tribological properties of Ti-5Zr-3Sn-5Mo-15Nb alloy by double glow plasma surface alloying by Lili Guo; Lin Qin; Fanyou Kong; Hong Yi; Bin Tang (203-211).
Molybdenum, an alloying element, was deposited and diffused on Ti-5Zr-3Sn-5Mo-15Nb (TLM) substrate by double glow plasma surface alloying technology at 900, 950 and 1000 °C. The microstructure, composition distribution and micro-hardness of the Mo modified layers were analyzed. Contact angles on deionized water and wear behaviors of the samples against corundum balls in simulated human body fluids were investigated. Results show that the surface microhardness is significantly enhanced after alloying and increases with treated temperature rising, and the contact angles are lowered to some extent. More importantly, compared to as-received TLM alloy, the Mo modified samples, especially the one treated at 1000 °C, exhibit the significant improvement of tribological properties in reciprocating wear tests, with lower specific wear rate and friction coefficient. To conclude, Mo alloying treatment is an effective approach to obtain excellent comprehensive properties including optimal wear resistance and improved wettability, which ensure the lasting and safety application for titanium alloys as the biomedical implants.
Keywords: Ti-5Zr-3Sn-5Mo-15Nb; Mo alloyed layer; Hardness; Tribological properties;
Electrochemical properties of the passive film on bulk Zr–Fe–Cr intermetallic fabricated by spark plasma sintering by Yakui Bai; Yunhan Ling; Wensheng Lai; Shupei Xing; Wen Ma (212-222).
Although Zr-based second phase particles (SPPs) are important factors influencing corrosion resistance of zircaloy cladding materials, the corrosion behavior of SPPs has not been investigated by means of electrochemical method so far. In order to clarify the role of SPPs commonly existed in zircaloy, bulk Zr-based intermetallics were firstly fabricated by spark plasma sintering (SPS) at temperatures 1373 K and an applied pressure of 60 MPa in this work. Both the natural passive film on surface and oxidation behavior of intermetallic has been investigated in this work. X-ray diffraction (XRD) pattern showed that as-prepared intermetallic of crystal structure belongs to Laves phase with AB2 type. Electrochemical measurement of passive film on surface of bulk Zr-based intermetallic exhibited significant difference with that of zirconium. Potentiodynamic measurements results revealed that intermetallic exhibited higher corrosion potential and lower corrosion current density than that of pure zirconium, implying that Zr-based second phase will act as cathode when they are included in zirconium matrix. Meanwhile, significant improvement of Zr–Fe–Cr intermetallic on the water chemistry corrosion resistance was demonstrated comparing with Zr–Fe and Zr–Cr binary intermetallics.
Keywords: Zirconium; Intermetallic; Second phase particle; Passive film; Electrochemical impedance spectroscopy;
Effects of scaffold surface morphology on cell adhesion and survival rate in vitreous cryopreservation of tenocyte-scaffold constructs by Zhi Wang; Quan Qing; Xi Chen; Cheng-Jun Liu; Jing-Cong Luo; Jin-Lian Hu; Ting-Wu Qin (223-227).
The purpose of this study was to investigate the effects of scaffold surface morphology on cell adhesion and survival rate in vitreous cryopreservation of tenocyte-scaffold constructs. Tenocytes were obtained from tail tendons of rats. Polydimethylsiloxane (PDMS) was used to fabricate three types of scaffolds with varying surface morphological characteristics, i.e., smooth, micro-grooved, and porous surfaces, respectively. The tenocytes were seeded on the surfaces of the scaffolds to form tenocyte-scaffold constructs. The constructs were cryopreserved in a vitreous cryoprotectant (CPA) with a multi-step protocol. The cell adhesion to scaffolds was observed with electronic scanning microscopy (SEM). The elongation index of the living tenocytes and ratio of live/dead cell number were examined based on a live/dead dual fluorescent staining technique, and the survival rate of tenocytes was studied with flow cytometry (FC). The results showed the shapes of tenocytes varied between the different groups: flat or polygonal (on smooth surface), spindle (on micro-grooved surface), and spindle or ellipse (on porous surface). After thawing, the porous surface got the most living tenocytes and a higher survival rate, suggesting its potential application for vitreous cryopreservation of engineered tendon constructs.
Keywords: Tenocyte; Scaffold; Surface morphology; Vitreous cryopreservation; Adhesion; Survival rate;
Stabilized copper plating method by programmed electroplated current: Accumulation of densely packed copper grains in the interconnect by Li-Chi Kao; Li-Hsuan Hsu; Sanjaya Brahma; Bo-Chia Huang; Chun-Chu Liu; Kuang-Yao Lo (228-233).
In this work, we programmed the plating current to stack the different size of copper (Cu) grain and analyzed the relation between the sequence of different Cu grain size and the stability of the residual stress. The residual stress was measured with varying times of annealing process in order to reach the purpose of simulating the actual Cu interconnect process. We found that varied plating strategy will make different stabilization condition of residual stress through the proof of X-ray diffraction (XRD) and optical parallel beams reflection (PBR) method. The accumulation of Cu grains, formed by Cu grain with successive variation in grain size, would enhance the packing density better than only single grain size in the finite space. The high density of the grain boundary in the electroplated Cu film will be eliminated through annealing process and it will help to suppress the void formation in further interconnect process. The electroplated Cu film with the plating current of saw tooth wave can soon reach a stable tensile stress through annealing since the Cu grains with high packing density will be quickly eliminated to approach the minimum of the strain energy which reflects to variation in the texture of Cu (2 0 0). The result of this work illustrates the importance of how to stack different size of Cu grain, for achieving a densely packed Cu film which close to the Cu bulk.
Keywords: Electroplated Cu; Residual stress; Grain boundary; Packing density; Interconnect process;
Surface composition effect of nitriding Ni-free stainless steel as bipolar plate of polymer electrolyte fuel cell by Yang Yu; Sayoko Shironita; Kunio Nakatsuyama; Kenichi Souma; Minoru Umeda (234-238).
The anodic current densities in the passive region of nitrided SUS445-N stainless steel are lower than those of a non heat-treated SUS445 stainless steel and heat-treated SUS445-Ar stainless steel under an Ar atmosphere. It shows a better corrosion resistance for the SUS445 stainless steel after the nitriding heat treatment.In order to increase the corrosion resistance of low cost Ni-free SUS445 stainless steel as the bipolar plate of a polymer electrolyte fuel cell, a nitriding surface treatment experiment was carried out in a nitrogen atmosphere under vacuum conditions, while an Ar atmosphere was used for comparison. The electrochemical performance, microstructure, surface chemical composition and morphology of the sample before and after the electrochemical measurements were investigated using linear sweep voltammetry (LSV), X-ray diffraction (XRD), glow discharge optical emission spectroscopy (GDS) and laser scanning microscopy (LSM) measurements. The results confirmed that the nitriding heat treatment not only increased the corrosion resistance, but also improved the surface conductivity of the Ni-free SUS445 stainless steel. In contrast, the corrosion resistance of the SUS445 stainless steel decreased after heat treatment in an Ar atmosphere. These results could be explained by the different surface compositions between these samples.
Keywords: Nitriding surface treatment; Stainless steel; Corrosion resistance; Bipolar plate; Polymer electrolyte fuel cell;
Proton conductive montmorillonite-Nafion composite membranes for direct ethanol fuel cells by Xiu-Wen Wu; Nan Wu; Chun-Qing Shi; Zhi-Yuan Zheng; Hong-Bin Qi; Ya-Fang Wang (239-244).
The preparation of Nafion membranes modified with montmorillonites is less studied, and most relative works mainly applied in direct methanol fuel cells, less in direct ethanol fuel cells. Organic/inorganic composite membranes are prepared with different montmorillonites (Ca-montmorillonite, Na-montmorillonite, K-montmorillonite, Mg-montmorillonite, and H-montmorillonite) and Nafion solution via casting method at 293 K in air, and with balance of their proton conductivity and ethanol permeability. The ethanol permeability and proton conductivity of the membranes are comparatively studied. The montmorillonites can well decrease the ethanol permeability of the membranes via inserted them in the membranes, while less decrease the proton conductivities of the membranes depending on the inserted amount and type of montmorillonites. The proton conductivities of the membranes are between 36.0 mS/cm and 38.5 mS/cm. The ethanol permeability of the membranes is between 0.69 × 10−6 cm2/s and 2.67 × 10−6 cm2/s.
Keywords: Organic/inorganic composites; Ethanol permeability; Water uptake; Microstructure;
Preparation of titanium dioxide films on etched aluminum foil by vacuum infiltration and anodizing by Lian Xiang; Sang-Shik Park (245-251).
Al2O3–TiO2 (Al–Ti) composite oxide films are a promising dielectric material for future use in capacitors. In this study, TiO2 films were prepared on etched Al foils by vacuum infiltration. TiO2 films prepared using a sol–gel process were annealed at various temperatures (450, 500, and 550 °C) for different time durations (10, 30, and 60 min) for 4 cycles, and then anodized at 100 V. The specimens were characterized using X-ray diffraction, field emission scanning electron microscopy, and field emission transmission electron microscopy. The results show that the tunnels of the specimens feature a multi-layer structure consisting of an Al2O3 outer layer, an Al–Ti composite oxide middle layer, and an aluminum hydrate inner layer. The electrical properties of the specimens, such as the withstanding voltage and specific capacitance, were also measured. Compared to specimens without TiO2 coating, the specific capacitances of the TiO2-coated specimens are increased. The specific capacitance of the anode Al foil with TiO2 coating increased by 42% compared to that of a specimen without TiO2 coating when annealed at 550 °C for 10 min. These composite oxide films could enhance the specific capacitance of anode Al foils used in dielectric materials.
Keywords: Vacuum infiltration method; Al–Ti composite oxide film; Al Electrolytic capacitor; Etched Al foil;
Effect of hydrogen uptake on the electrochemical corrosion of N18 zircaloy under gamma irradiation by Z.Y. Xin; Y.H. Ling; Y.K. Bai; C. Zeng; S. Wang; J.C. Clara (252-258).
It has been well recognized that dramatic hydrogen uptake occurred in zircaloy after kinetic transition and porous structure was observed subsequently due to phase transformation of tetragonal to monoclinic zirconia. Therefore, how hydrogen solute and gamma-induced capillary-embedded hydrolysis influence the corrosion of zircaloy is an intriguing issue. In this work, the effect of hydrogen uptake and gamma irradiation on corrosion of N18 zircaloy was studied. Raman spectra and atomic force microscopy (AFM) were employed to analyse phase structure and surface morphology. Potentiodynamic polarization and electrochemical impedance spectroscopy were utilized to qualitatively evaluate the electron transfer properties of the oxide film formed on the zircaloy surface after corrosion. The depth profile and surface chemical states of involving elements were analysed by auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS), respectively. It was found that hydrogen permeation can decline the integrity and impedance semicircle of the oxide films, the more the hydrogen uptake is; the smaller magnitude of impedance will be. In view of the gamma irradiation, it is demonstrated that it promotes the corrosion rate slightly. Based on the irradiation theory and existing phenomena, the underlying mechanism is proposed.
Keywords: Zircaloy; Hydrogen permeation; Gamma irradiation; Corrosion;
Experimental investigation on photoelectric properties of ZAO thin film deposited on flexible substrate by magnetron sputtering by Ming Hao; Kun Liu; Xinghua Liu; Dongyang Wang; Dechun Ba; Yuanhua Xie; Guangyu Du; Yaoshuai Ba (259-267).
Transparent conductive ZAO (Zinc Aluminum Oxide) films on flexible substrates have a great potential for low-cost mass-production solar cells. ZAO thin films were achieved on flexible PET (polyethylene terephthalate) substrates by RF magnetron sputtering technology. The surface morphology and element content, the transmittance and the sheet resistance of the films were measured to determine the optical process parameters. The results show that the ZAO thin film shows the best parameters in terms of photoelectric performance including sputtering power, working pressure, sputtering time, substrate temperature (100 W, 1.5 Pa, 60 min, 125 °C). The sheet resistance of 510 Ω and transmittance in visible region of 92% were obtained after characterization. Surface morphology was uniform and compact with a good crystal grain.
Keywords: ZAO thin films; RF; Magnetron sputtering; Flexible PET substrate; Photoelectric properties;
Design of a superhydrophobic and superoleophilic film using cured fluoropolymer@silica hybrid by Hao Yang; Pihui Pi; Zhuo-ru Yang; Zhong Lu; Rong Chen (268-273).
Recently, considerable efforts have been made on superhydrophobic–superoleophilic filter to satisfy the requirements of the applications to oil/water separation. In this work, we obtained a superhydrophobic and superoleophilic film by coating cured fluoropolymer@silica hybrid on stainless steel mesh. Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric-differential scanning calorimetry (TG-DSC) were used to determine the chemical composition and thermal stability of the sample. The effect of silica nanoparticles (NPs) concentration on the surface property of the hybrid film was analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle analyzer. The results indicate that silica NPs not only enhance the thermal stability, but also strengthen the hydrophobicity and oleophilicity of the film. When 20 wt% silica NPs was added into the thermosetting fluoropolymer, the hybrid film shows both superhydrophobicity and superoleophilicity owing to the large surface roughness factor (RMS) and porous structure. Moreover, the hybrid film could be used to separate water from different oils effectively. When the pore size of the mesh is less than 300 μm, the oil/water separation efficiency of the film reaches above 99%, which shows a great potential application to dehydrate fuel oils.
Keywords: Superhydrophobic; Superoleophilic; Fluoropolymer; Silica; Hybrid; Oil/water separation;
Synthesis and electrochemical performance of ruthenium oxide-coated carbon nanofibers as anode materials for lithium secondary batteries by Yura Hyun; Jin-Yeong Choi; Heai-Ku Park; Chang-Seop Lee (274-280).
In this study, ruthenium oxide (RuO2) coated carbon nanofibers (CNFs) were synthesized and applied as anode materials of Li secondary batteries. The CNFs were grown on Ni foam via chemical vapor deposition (CVD) method after CNFs/Ni foam was put into the 0.01 M RuCl3 solution. The ruthenium oxide-coated CNFs/Ni foam was dried in a dryer at 80 °C. The morphologies, compositions, and crystal quality of RuO2/CNFs/Ni foam were characterized by SEM, EDS, XRD, Raman spectroscopy, and XPS. The electrochemical characteristics of RuO2/CNFs/Ni foam as anode of Li secondary batteries were investigated using three-electrode cell. The RuO2/CNFs/Ni foam was directly employed as a working electrode without any binder, and lithium foil was used as the counter and reference electrodes. LiClO4 (1 M) was employed as electrolyte and dissolved in a mixture of propylene carbonate (PC): ethylene carbonate (EC) in a 1:1 volume ratio. The galvanostatic charge/discharge cycling and cyclic voltammetry measurements were carried out at room temperature by using a battery tester. In particular, synthesized RuO2/CNFs/Ni foam showed the highest retention rate (47.4%). The initial capacity (494 mAh/g) was reduced to 234 mAh/g after 30 cycles.
Keywords: Ruthenium Oxide; Carbon Nanofibers; Anode materials; Lithium secondary batteries;
Prediction of the properties of PVD/CVD coatings with the use of FEM analysis by Agata Śliwa; Jarosław Mikuła; Klaudiusz Gołombek; Tomasz Tański; Waldemar Kwaśny; Mirosław Bonek; Zbigniew Brytan (281-287).
The aim of this paper is to present the results of the prediction of the properties of PVD/CVD coatings with the use of finite element method (FEM) analysis. The possibility of employing the FEM in the evaluation of stress distribution in multilayer Ti/Ti(C,N)/CrN, Ti/Ti(C,N)/(Ti,Al)N, Ti/(Ti,Si)N/(Ti,Si)N, and Ti/DLC/DLC coatings by taking into account their deposition conditions on magnesium alloys has been discussed in the paper. The difference in internal stresses in the zone between the coating and the substrate is caused by, first of all, the difference between the mechanical and thermal properties of the substrate and the coating, and also by the structural changes that occur in these materials during the fabrication process, especially during the cooling process following PVD and CVD treatment.The experimental values of stresses were determined based on X-ray diffraction patterns that correspond to the modelled values, which in turn can be used to confirm the correctness of the accepted mathematical model for testing the problem.An FEM model was established for the purpose of building a computer simulation of the internal stresses in the coatings. The accuracy of the FEM model was verified by comparing the results of the computer simulation of the stresses with experimental results. A computer simulation of the stresses was carried out in the ANSYS environment using the FEM method.Structure observations, chemical composition measurements, and mechanical property characterisations of the investigated materials has been carried out to give a background for the discussion of the results that were recorded during the modelling process.
Keywords: Magnesium alloys; Residual stress; Computer simulation; Finite Element Method; PVD; CVD;
Light-emitting structures of CdS nanocrystals in oxidized macroporous silicon by L. Karachevtseva; S. Kuchmii; O. Stroyuk; O. Lytvynenko; O. Sapelnikova; O. Stronska; Wang Bo; M. Kartel (288-293).
Structured silicon substrates (macroporous silicon) with SiO2 nanolayers and CdS nanocrystals were proposed to reduce the flow of electrons and recombination outside the nanoparticle layer. It was found that the resonance electron scattering in samples with low concentration of Si―O―Si states transforms into ordinary scattering on ionized impurities for samples with high concentration of Si―O―Si states. The maximal intensity of photoluminescence was measured for a structure with maximum strength of the local electric field at the Si―SiO2 interface, indicating a significant decrease of non-radiative recombination in CdS nanocoating due to the flow of electrons from the silicon matrix towards the CdS nanocrystal layer. The quantum yield of photoluminescence increases with time due to evaporation of water molecules.
Keywords: Photoluminescence; CdS nanocrystals; Oxidized macroporous silicon;
Surface chemical state of Ti powders and its alloys: Effect of storage conditions and alloy composition by Eduard Hryha; Ruslan Shvab; Martin Bram; Martin Bitzer; Lars Nyborg (294-303).
High affinity of titanium to oxygen in combination with the high surface area of the powder results in tremendous powder reactivity and almost inevitable presence of passivation oxide film on the powder surface. Oxide film is formed during the short exposure of the powder to the environment at even a trace amount of oxygen. Hence, surface state of the powder determines its usefulness for powder metallurgy processing. Present study is focused on the evaluation of the surface oxide state of the Ti, NiTi and Ti6Al4V powders in as-atomized state and after storage under air or Ar for up to eight years.Powder surface oxide state was studied by X-ray photoelectron spectroscopy (XPS) and high resolution scanning electron microscopy (HR SEM). Results indicate that powder in as-atomized state is covered by homogeneous Ti-oxide layer with the thickness of ∼2.9 nm for Ti, ∼3.2 nm and ∼4.2 nm in case of Ti6Al4V and NiTi powders, respectively. Exposure to the air results in oxide growth of about 30% in case of Ti and only about 10% in case of NiTi and Ti6Al4V. After the storage under the dry air for two years oxide growth of only about 3-4% was detected in case of both, Ti and NiTi powders. NiTi powder, stored under the dry air for eight years, indicates oxide thickness of about 5.3 nm, which is about 30% thicker in comparison with the as-atomized powder. Oxide thickness increase of only ∼15% during the storage for eight years in comparison with the powder, shortly exposed to the air after manufacturing, was detected.Results indicate a high passivation of the Ti, Ti6Al4V and NiTi powder surface by homogeneous layer of Ti-oxide formed even during short exposure of the powder to the air.
Keywords: Titanium powder; Titanium alloy powder; Surface chemical state; Oxide layer thickness; Storage conditions;
Investigation of electrode distance impact on PEO coating formation assisted by simulation by Xun Ma; Carsten Blawert; Daniel Höche; Mikhail L. Zheludkevich; Karl U. Kainer (304-312).
The influence of electrode distance between anode and cathode during plasma electrolytic oxidation (PEO) process on the coating formation was investigated by combining experiments and simulation. Firstly a model was built to simulate the effect of electrode distance on the anodic current distribution using finite element analyses. Complementary, PEO coatings were fabricated on AM50 magnesium alloy in an alkaline electrolyte with different electrode distances applying constant voltage. Phase composition, coating morphology and thickness were studied for both the front and back sides of the PEO coating depending on the electrode distance. For paralleled plate-like electrodes, based on coating uniformity, an optimum electrode distance of 60–80 mm was identified under the chosen experimental conditions. Via correlation of simulation and experimental results, the influence of electrode distance on coating formation is explored. It is demonstrated that under constant voltage mode, PEO coating formation is affected by electrode distance on both front and back sides of magnesium substrates. This effect is ascribed to the influence of electrode distance on the current distribution in the bath and to the related average current density on the surfaces.
Keywords: PEO; Electrode distance; Simulation; Coating; Magnesium;
Surface wettability of TiO2 nanotube arrays prepared by electrochemical anodization by Guohua Liu; Kang Du; Kaiying Wang (313-320).
Surface wettability of TiO2 nanotube arrays prepared by electrochemical anodization.This work reports structural engineering and wettability of titania nanotube arrays (TNTs). The nanotube diameter and thickness of TNT layer increase with increasing of applied voltage from 20 to 40, 60 and 80 V, and the diameter has no relevance to extending anodic duration. The fabricated TNTs are 30–190 nm inner diameter and 5–40 mm height. 10 mL water droplets are applied to define wettability of the TNTs by measuring contact angles. Hydrophilicity is enhanced with increasing diameter of TNTs as well as over-etching occurring on the surface. Large diameter tubes and capillary force provide more space and power for liquid to penetration. The contact angle reduces from 35° to 2° with the tube diameter increasing from 30 to 190 nm. Bare Ti foil is inherently hydrophobic with approximately 90° contact angle. The as-prepared TNTs are hydrophilic with contact angle of 24°, and annealing further improves this property to a contact angle of 13°. The bottom of TNTs shows superhydrophilic due to hydroxide compounds existed on the surface. The metal substrate with tube footprint left presents hydrophobic with contact angle of 68°, which is lower than the bare one. It is believed that wettability on the surface of TNTs is dependent on their morphology and chemical composition.
Keywords: Anodization; TiO2 nanotube arrays; Hydrophilic; Wettability; Contact angles;
In vitro study of 3D PLGA/n-HAp/β-TCP composite scaffolds with etched oxygen plasma surface modification in bone tissue engineering by Hee-Sang Roh; Sang-Chul Jung; Min-Suk Kook; Byung-Hoon Kim (321-330).
Three-dimensional (3D) scaffolds have many advantageous properties for bone tissue engineering application, due to its controllable properties such as pore size, structural shape and interconnectivity. In this study, effects on oxygen plasma surface modification and adding of nano-hydroxyapatite (n-HAp) and β-tricalcium phosphate (β-TCP) on the 3D PLGA/n-HAp/β-TCP scaffolds for improving preosteoblast cell (MC3T3-E1) adhesion, proliferation and differentiation were investigated. The 3D PLGA/n-HAp/β-TCP scaffolds were fabricated by 3D Bio-Extruder equipment. The 3D scaffolds were prepared with 0°/90° architecture and pore size of approximately 300 μm. In addition 3D scaffolds surface were etched by oxygen plasma to enhance the hydrophilic property and surface roughness. After oxygen plasma treatment, the surface chemistry and morphology were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. And also hydrophilic property was measured by contact angle. The MC3T3-E1 cell proliferation and differentiation were investigated by MTT assay and ALP activity. In present work, the 3D PLGA/HAp/beta-TCP composite scaffold with suitable structure for the growth of osteoblast cells was successfully fabricated by 3D rapid prototyping technique. The surface hydrophilicity and roughness of 3D scaffold increased by oxygen plasma treatment had a positive effect on cell adhesion, proliferation, and differentiation. Furthermore, the differentiation of MC3T3-E1 cell was significantly enhanced by adding of n-HAp and β-TCP on 3D PLGA scaffold. As a result, combination of bioceramics and oxygen plasma treatment showed a synergistic effect on biocompatibility of 3D scaffolds. This result confirms that this technique was useful tool for improving the biocompatibility in bone tissue engineering application.
Keywords: 3D scaffold; PLGA; Plasma etching; Hydroxyapatite; β-Tricalcium phosphate;
Preparation of ZnO nanorods on conductive PET-ITO-Ag fibers by Yiwen Li; Shuai Ji; Yuanyu Chen; Hong Zhang; Yumei Gong; Jing Guo (331-338).
We studied the vertical ZnO nanorods grown on conductive conventional polyethylene terephthalate (PET) fibers which are prepared by electroless silver depositing on tin-doped indium oxide (ITO) coated PET fibers through an efficient and low-cost green approach. The PET fibers were firstly functionalized with a layer of ITO gel synthesized through a sol–gel process at rather low temperature, simply by immersing the fibers into ITO sol for several minutes followed by gelation at 120 °C. Once the ITO gel layer surface was activated by SnCl2, a continuous, uniform, and compact layer of silver was carried out on the surface of the PET-ITO fibers through electroless plating operation at room temperature. The as-prepared PET-ITO-Ag fibers had good electrical conductivity, with surface resistivity as low as 0.23 mΩ cm. The overall procedure is simple, efficient, nontoxic, and controllable. The conductive PET-ITO-Ag fiber was used successfully as a flexible basal material to plant vertical ZnO nanorods through controlling the seeding and growth processes. The morphology of the PET-ITO, PET-ITO-Ag, and PET-ITO-Ag-ZnO fibers were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Undergone the whole process, although the tensile strength of the fiber decreased slightly, they may still exert their applications in flexible electronic such as photovoltaic and piezoelectric devices.
Keywords: Surface coating; PET-ITO-Ag conductive fiber; PET-ITO-Ag-ZnO fiber; ZnO nanorods;
Real-time study of electromigration in Sn Blech structure by C.E. Ho; W.Z. Hsieh; C.H. Yang; P.T. Lee (339-344).
Electromigration has become a critical issue for reliability in Sn-based conducting materials that are used in advanced microelectronic packages with micro-joint integration. In this study, a Blech structure was used to characterize the Sn electromigration behavior of various strip lengths (L 0 = 10–100 μm). We established a mathematical model based on the fundamental electromigration theory to describe the correlation between the residual strip length (L) and the current stressing time (t). A three-stage mechanism was proposed to rationalize the Sn electromigration in the Blech structure. A good agreement between the mathematical model and experimental data was obtained, advancing our understanding of Sn electromigration.
Keywords: Blech structure; Electromigration; Back stress; Sn film; Sn whiskers;
Synthesis of three-dimensional flower-like BiOCl:RE3+ (RE3+ = Eu3+, Sm3+) globular microarchitectures and their luminescence properties by Yang-Yang Guo; Zhi-Jun Zhang; Gang-Qiang Zhu; Woochul Yang (345-351).
Three-dimensional flower-like Eu3+ and Sm3+-activated BiOCl globular microarchitectures were synthesized by the solvothermal method employing urea as a dispersing agent for the first time. The crystal structure, morphologies and luminescence properties of Eu3+ and Sm3+ doped BiOCl have been systematically investigated by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) and spectroscopy, respectively. The unit cell volumes show a nearly linear decrease by about 0.18 and 0.15% with increasing Eu3+ and Sm3+ concentration up to 9 mol%, respectively. All of the prepared samples show flower-like globular microarchitectures with an average diameter about 3–5 μm with different Eu3+ and Sm3+ concentrations. Possible formation mechanism for the flower-like microarchitectures is proposed on the basis of time-dependent experiment. Both BiOCl:Eu3+ and BiOCl:Sm3+ samples show a strong red emission corresponding to the 5D0 → 7F4 transition (700 nm) of Eu3+ and 4G5/2 → 6H7/2 transition (600 nm) of Sm3+, respectively. This work sheds some light on the design and preparation of red-emitting phosphors with novel microstructures.
Keywords: BiOCl; Flower-like structure; Luminescence; Solvothermal;
Improving photoelectrochemical performance on quantum dots co-sensitized TiO2 nanotube arrays using ZnO energy barrier by atomic layer deposition by Min Zeng; Xi Zeng; Xiange Peng; Zhuo Zhu; Jianjun Liao; Kai Liu; Guizhen Wang; Shiwei Lin (352-358).
PbS and CdS quantum dots (QDs) have been deposited onto TiO2 nanotube arrays (TNTAs) in turn via a sonication-assisted successive ionic layer adsorption and reaction method. This method could uniformly decorate TNTAs with QDs, avoiding QDs aggregation at the mouth of TiO2 nanotube. The loading amounts of QDs on TNTAs could be controlled by adjusting the TNTAs length. Under one sun illumination, the QDs co-sensitized TNTAs (TNTAs/QDs) with the length of about 2.4 μm displayed the highest photocurrent of 4.32 mA cm−2, which is 27 times higher than that of the bare TNTAs. Introduction of a thin ZnO energy barrier by atomic layer deposition (ALD) between the TNTAs and QDs can further improve the photocurrent of TNTAs/QDs. And the TNTAs/QDs with 10 ALD cycles of ZnO interlayer exhibits the highest photocurrent of 5.24 mA cm−2 and best photoconversion efficiency of 4.9%, a more than 20% enhancement over the bare TNTAs/QDs. Such enhanced photoelectrochemical performance may be ascribed to the increased amounts of QDs on the TNTAs due to the introduction of ZnO interlayer. The benefits of ALD layers play a crucial role in development and optimization of high-performance photoelectrodes in the near future.
Keywords: TiO2 nanotube arrays; Quantum dots; Interface modification; Atomic layer deposition;
Behavior of the new composites obtained from fly ash and titanium dioxide in removing of the pollutants from wastewater by Maria Visa; Luminita Andronic; Alexandru Enesca (359-369).
The goal of this paper was to develop a low-temperature TiO2-fly ash (TiO2-FA) composite based on interaction in alkaline solution using hydrothermal methods, to obtain crystalline nanocomposite at low temperature. These composites are interesting to be applied in visible photocatalysis/adsorption simultaneous advanced wastewater processes. Combining fly ash with titanium dioxide has the following advantages: (1) the titanium oxide crystallites grow on the support (active fly ash); (2) pollutant molecules migrate to the surface of TiO2 can be degraded by photocatalysis; and (3) activated fly ash substrates are regenerated in situ.The composites were characterized by the scanning electron microscopy (SEM) and atomic force microscopy (AFM) for morphological characterization of the surface, X-ray diffraction (XRD) for phase and crystallinity analysis, UV–vis spectroscopy to calculate the energy band gap, surface analysis by determining the contact angle, porosity analysis (BET).The photocatalytic property of the composites was evaluated by dye (methylene blue), surfactant (dodecylbenzenesulfonate–SDBS) degradation under UV and Visible irradiation. The adsorption tests were made on heavy metal (Cu2+) cation. Properties of composites were correlated with the adsorption/photocatalytic activity of the samples.
Keywords: Composites; Adsorption; Photodegradation; Heavy-metals; Surfactants; Dye;
Effects of modifying agents on surface modifications of magnesium oxide whiskers by Yun Zhao; Bei Liu; Jinjun Yang; Junping Jia; Chen You; Minfang Chen (370-375).
In this work, the MgO whiskers have been treated by several modifying agents including the mixture of dl-malic acid oligo-l-lactide (g), aluminate coupling agent (Al) and stearic acid (Sa). The morphologies, covering quantity, compositions and components of the whiskers before and after the modifications were investigated by SEM, TG, XRD and FT-IR, respectively. Comparisons have been made on the morphologies of modified whiskers by different modifiers tailoring. The results show that the MgO whiskers treated by stearic acid have superior performance to the others, especially in terms of uniform dispersion. In contrast, both the mixture of dl-malic acid oligo-l-lactide and aluminate coupling agent have the negative effects on whiskers’ dispersibility. FT-IR reveals that the chemical bonds were formed between the whiskers and each modifying agent and the XRD testing demonstrate that the crystal structures of the modified whiskers were well maintained without significant change.
Keywords: Magnesium oxide whiskers; Surface modifications; Modifying agents;
Structural and electrical properties of heterojunction devices formed by spinning TIPS Pentacene thin films on n-Si substrates by Ke Wang; Ya Huang; Ruofei Chen; Zhan Xu (376-380).
Heterojunctions were fabricated by spinning triisopropylsilyl (TIPS) Pentacene films on n-Si. The electrical transport measurements reveal that the heterojunctions possess good Schottky-type rectifying capability. The electrical parameters of the devices are derived by applying thermionic emission model. The electrical characteristics of the devices are found to be strongly related to the thickness of TIPS Pentacene film. A high barrier height demonstrated in the device formed with thin TIPS Pentacene can be explained by a low image force lowering and small roughness of the film. The large rectification ratio accompanied with the low reverse saturation current exhibited in the device with thin film may be attributed to this high barrier height formed in the junction. A depletion width in Si was estimated to be ∼860 nm in TIPS Pentacene/Si junctions from the zero-bias capacitance measured at 1 MHz.
Keywords: Triisopropylsilyl Pentacene film; Structural properties; Electrical characterisation; Heterojunction devices;
Non-uniform binding of single-stranded DNA binding proteins to hybrids of single-stranded DNA and single-walled carbon nanotubes observed by atomic force microscopy in air and in liquid by Kazuo Umemura; Kei Ishizaka; Daisuke Nii; Katsuki Izumi (381-384).
Using atomic force spectroscopy (AFM), we observed hybrids of single-stranded DNA (ssDNA) and single-walled carbon nanotubes (SWNTs) with or without protein molecules in air and in an aqueous solution. This is the first report of ssDNA–SWNT hybrids with proteins in solution analyzed by AFM. In the absence of protein, the height of the ssDNA–SWNT hybrids was 1.1 ± 0.3 nm and 2.4 ± 0.6 nm in air and liquid, respectively, suggesting that the ssDNA molecules adopted a flexible structure on the SWNT surface. In the presence of single-stranded DNA binding (SSB) proteins, the heights of the hybrids in air and liquid increased to 6.4 ± 3.1 nm and 10.0 ± 4.5 nm, respectively. The AFM images clearly showed binding of the SSB proteins to the ssDNA–SWNT hybrids. The morphology of the SSB–ssDNA–SWNT hybrids was non-uniform, particularly in aqueous solution. The variance of hybrid height was quantitatively estimated by cross-section analysis along the long-axis of each hybrid. The SSB–ssDNA–SWNT hybrids showed much larger variance than the ssDNA–SWNT hybrids.
Keywords: Single-stranded DNA; Single-stranded DNA binding protein; Single-walled carbon nanotubes; Atomic force microscopy;
Effect of surface topological structure and chemical modification of flame sprayed aluminum coatings on the colonization of Cylindrotheca closterium on their surfaces by Xiuyong Chen; Xiaoyan He; Xinkun Suo; Jing Huang; Yongfeng Gong; Yi Liu; Hua Li (385-391).
Biofouling is one of the major problems for the coatings used for protecting marine infrastructures during their long-term services. Regulation in surface structure and local chemistry is usually the key for adjusting antifouling performances of the coatings. In this study, flame sprayed multi-layered aluminum coatings with micropatterned surfaces were constructed and the effects of their surface structure and chemistry on the settlement of typical marine diatoms were investigated. Micropatterned topographical morphology of the coatings was constructed by employing steel mesh as a shielding plate during the coating deposition. A silicone elastomer layer for sealing and interconnection was further brush-coated on the micropatterned coatings. Additional surface modification was made using zwitterionic molecules via DOPA linkage. The surface-modified coatings resist effectively colonization of Cylindrotheca closterium. This is explained by the quantitative examination of a simplified conditioning layer that deteriorated adsorption of bovine calf serum proteins on the zwitterionic molecule-treated samples is revealed. The colonization behaviors of the marine diatoms are markedly influenced by the micropatterned topographical morphology. Either the surface micropatterning or the surface modification by zwitterionic molecules enhances antimicrobial ability of the coatings. However, the combined micropatterned structure and zwitterionic modification do not show synergistic effect. The results give insight into anti-corrosion/fouling applications of the modified aluminum coatings in the marine environment.
Keywords: Aluminum coatings; Surface functionalization; Diatom colonization; Microtopography; Antifouling;
Study on the preparation of boron-rich film by magnetron sputtering in oxygen atmosphere by Zhangmin Pan; Yiming Yang; Jian Huang; Bing Ren; Hongze Yu; Run Xu; Huanhuan Ji; Lin Wang; Linjun Wang (392-395).
In this paper, the growth of boron (10B) oxide films on (1 0 0) silicon substrate were achieved by radio frequency (r.f.) magnetron sputtering under the different oxygen partial pressure with a target of boron and boron oxide. The structure and properties of deposited films were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy spectrometer (FTIR), X-ray photoelectron spectroscopy (XPS), respectively. The results showed that the substrate was covered with boron-rich films tightly and the surface of films was covered with B2O3. And the growth mechanism of boron-rich film in oxygen atmosphere was also analyzed.
Keywords: Boron films; Magnetron sputtering; X-ray photoelectron spectroscopy;
Ellipsometric study and application of rubrene thin film in organic Schottky diode by Liang Chen; Jinxiang Deng; Hongli Gao; Qianqian Yang; Le Kong; Min Cui; Zijia Zhang (396-400).
Rubrene thin film was deposited by thermal evaporation technique under high vacuum (∼10−4 Pa). The film surface morphology was characterized by atomic force microscopy (AFM). Ellipsometric studies on rubrene thin film were presented for understanding its growth and optical characteristics by the Classical-Oscillator model. The analysis of the absorption coefficient (α) revealed the direct allowed transition with corresponding energy 2.21 eV of the rubrene film. In order to exploring the rubrene applications, Al/rubrene/ITO Schottky diode was fabricated. The basic device parameters, barrier height and ideality factor were determined by the I–V measurement. The log(I)–log(V) characteristic indicated three distinct regions. These regions followed ohmic conduction, TCL conduction and SCLC conduction mechanisms.
Keywords: Rubrene; Spectroscopic Ellipsometry; Optical constant; Organic Schottky diode;
Optimized dispersion of conductive agents for enhanced Li-storage performance of TiO2 by Moyan Han; Ge Chen (401-405).
Novel TiO2/carbon (TiO2/C) composites have been synthesized by a layer-by-layer deposition method, with electrostatic interaction. The addition of carbon conductive agents enhances the electrochemical performance of TiO2. Carbon for these has been sourced 0D nitrogen-doped carbon, 1D carbon nanotubes and 2D graphene. The as-obtained TiO2/C composites show carbon nanotubes and titanium dioxide coaxial nanocables anchored on the graphene. The nitrogen-doped carbon is uniformly dispersed on the nanocables. As anode materials for Li-ion batteries, the TiO2/C composites exhibit excellent rate capability and cycling stability. A capacity of 150 mAh/g is retained at a current density of 4 A/g. The enhanced electrochemical performance may be attributed to the well-dispersed carbon conductive framework, which facilitates charge transfer during the lithium insertion/extraction process.
Keywords: TiO2; Graphene; Carbon nanotube; Composite; Lithium ion battery;
Improved wear resistance by phase transformation of surface nanocrystalline 1090 steel prepared by sandblasting technique by Rong Peng; Licai Fu; Lingping Zhou (406-411).
A surface nanocrystalline 1090 steel has been fabricated by using sandblasting technique. The surface average grain size was about 78 nm. The high strain rate and strain in sandblasting were main reasons for surface nanocrystallization. The wear resistance of 1090 steel was considerably enhanced as grain size decreased. The microstructure and hardness of contact zones before and after wear tests have been examined by XRD, SEM and TEM. Except the higher hardness, the results demonstrated that parts of ferrite transferred to cementite and martensite. It was additional beneficial for improving the wear resistance of 1090 steel as the grain size decreased.
Keywords: Nanocrystalline; Sandblasting; Wear behavior; Phase transformation;
Nanospherical composite of WO3 wrapped NaTaO3: Improved photodegradation of tetracycline under visible light irradiation by Lingnan Qu; Junyu Lang; Shuwei Wang; Zhanli Chai; Yiguo Su; Xiaojing Wang (412-419).
In this paper, WO3-wrapped NaTaO3 nanospheres photocatalysts with different W/Ta molar ratios were successfully prepared via a facile hydrothermal method. The samples were characterized by X-ray diffraction, transmission and scan electron microscopy, X-ray photoelectron spectroscopy, FT-IR spectrum, UV−vis diffuse reflectance spectroscopy, and Barrett−Emmett−Teller technique. The photocatalytic activities for degrading tetracycline hydrochloride under visible light irradiation were examined. The results indicated that the as-prepared NaTaO3@WO3 photocatalysts showed the obvious enhancement in the tetracycline hydrochloride degradation ratio, compared with the pure NaTaO3 and WO3 under visible light irradiation. The optimum percentage of NaTaO3@WO3 composites with a 60.88% degradation rate was W:Ta = 0.3:1 in mole, which was mainly attributed to the effective separation of the photo-generated electron and hole as well as the expanding of the absorption edge to the visible region due to the spherical heterojunction by wrapping WO3 on the surface of NaTaO3. The radicals trapping experiments demonstrated that there were multiple active species during the degrading process of TC. The possible mechanism of tetracycline hydrochloride degradation by NaTaO3@WO3 composite was also proposed.
Keywords: NaTaO3@WO3; Tetracycline hydrochloride; Degradation; Visible light irradiation; Spherical heterojunction;
Experimental research of surface roughness and surface texture after laser cladding by Damian Przestacki; Radomir Majchrowski; Lidia Marciniak-Podsadna (420-423).
The objective of the investigation was to identify surface integrity of machined parts after laser cladding. Surface analysis was made by using novel metrology methods: auto correlation and gradient distributions. An Infinite Focus Measurement Machine (IFM) has been used for the surface texture analysis. The study has been performed within a production facility during the prototyping process of new products. There are many methods available for geometric and surface topography measurements: contact and non-contact, micro and nanoscale approaches. An optical method based on the measurement of light reflected or scattered from the surface of an examined object can be used for this purpose. We have tested the application of an advanced 3D scanner for this purpose – optical scanner ATOS II. The scanner ATOS II represents the optical method, i.e. the digital light projection (DLP) method. The system consists of a projector and two digital cameras capable of supplying 1.4 million of measuring points per second. This method enables to scan elements from a few millimeters to a several dozen of meters in size. The roughness analysis is based on 2D measurements, which gave two-dimensional characteristics of the surface. In last decades, the metrology of the surface layer notes dynamical development as a science. During the last decades, many scientists and constructors became convinced that the third dimension should be added to the surface analysis. At present, 3D analysis of the surface geometry is widely accepted. In order to complete the topography analysis of the surface texture after laser cladding, our team worked out original program for 2D and 3D surface analysis. It was called TAS (topography analysis and simulation) and was based on Matlab software. Four modules were developed: the initial data processing module, basic parameters calculating module, data visualization module, and digital filtration module.
The formation of FHA coating on biodegradable Mg-Zn-Zr alloy using a two-step chemical treatment method by S.T. Jiang; J. Zhang; S.Z. Shun; M.F. Chen (424-430).
To improve the corrosion resistance of the biomedical magnesium alloy, a two-step chemical treatment method has been employed to prepare an FHA coating on the alloy surface. Prior to forming an FHA layer, the samples of Mg-3 wt% Zn-0.5 wt% Zr alloy were soaked in HF with concentration of 20% (v/v) at 37 °C temperature for 2 h, and were then placed into an aqueous solution with 0.1 mol/L Ca(NO3).4H2O and 0.06 mol/L NH4H2PO4 at 90 °C to prepare the Ca-P coating. The concentrations of Mg2 +, F− ions, and pH variation with immersing time in the solution were investigated to explore the growth mechanism of FHA. The surface morphologies and compositions of the coatings were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The results showed that the alloy surface treated with acid formed a layer of MgF2 nanoparticles with a thickness of 0.7 μm. The corrosion resistance of coatings in SBF solution was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The results showed that the substrate with FHA coating had good corrosion resistance. After immersing into the calcium phosphate solution, some small spherical particles were first formed on the surface; these then cover the surface completely after 20 min. Some clusters consisting of needle-like crystal were observed in the spherical particles covering the surface, and the Ca/P ratio of the needle-like crystal was 1.46, clearly growing along the c axis preferred orientation growth. After immersion for 60 min, the FHA coating with completely uniform growth was obtained on the Mg-Zn-Zr alloy surface with its thickness reaching about 120 μm.
Keywords: Mg-3Zn-0.8Zr alloy; Two-step chemical treatment method; Chemical deposition; MgF2 coating; FHA coating;
Electrochemiluminescent detection of Pb2+ by graphene/gold nanoparticles and CdSe quantum dots by Liping Lu; Linqing Guo; Jiao Li; Tianfang Kang; Shuiyuan Cheng (431-436).
A highly sensitive electrochemiluminescent detection method for lead ions (Pb(II)) was fabricated based on the distance-dependent quenching of the electrochemiluminescence from CdSe quantum dots by nanocomposites of graphene and gold nanoparticles. Graphene/gold nanoparticles were electrochemically deposited onto a glassy carbon electrode through the constant potential method. Thiol-labeled DNA was then assembled on the surface of the electrode via gold−sulfur bonding, following which the amino-labeled terminal of the DNA was linked to carboxylated CdSe quantum dots by the formation of amide bonds. The 27-base aptamer was designed with two different domains: the immobilization and detection sequences. The immobilization sequence was paired with 12 complementary bases and immobilized on the gold electrode; the single-stranded detection sequence, rich in G bases, formed a G-quadruplex (G4) structure in the presence of Pb2+. The formation of G4 shortens the distance between the CdSe quantum dots and the Au electrode, which decreases the electrochemiluminescent intensity in a linear fashion, proportional to the concentration of Pb(II). The linear range of the sensor was 10−10 to 10−8 mol/L (R = 0.9819) with a detection limit of 10−10 mol/L. This sensor detected Pb(II) in real water samples with satisfactory results.
Keywords: Biosensor; DNA; Electrochemiluminescence; Pb(II); Quantum dots;
Influence of surface states of CuInS2 quantum dots in quantum dots sensitized photo-electrodes by Zhuoyin Peng; Yueli Liu; Lei Wu; Yinghan Zhao; Keqiang Chen; Wen Chen (437-443).
J–V curves of different ligands capped CuInS2 QDs sensitized TiO2 photo-electrodes.Surface states are significant factor for the enhancement of electrochemical performance in CuInS2 quantum dot sensitized photo-electrodes. DDT, OLA, MPA, and S2− ligand capped CuInS2 quantum dot sensitized photo-electrodes are prepared by thermolysis, solvethermal and ligand-exchange processes, respectively, and their optical properties and photoelectrochemical properties are investigated. The S2− ligand enhances the UV–vis absorption and electron–hole separation property as well as the excellent charge transfer performance of the photo-electrodes, which is attributed to the fact that the atomic S2− ligand for the interfacial region of quantum dots may improve the electron transfer rate. These S2−-capped CuInS2 quantum dot sensitized photo-electrodes exhibit the excellent photoelectrochemical efficiency and IPCE peak value, which is higher than that of the samples with DDT, OLA and MPA ligands.
Keywords: CuInS2 quantum dot sensitized photo-electrodes; Surface states; Electrochemical performance enhancement;
Influences of post-annealing on structural, morphological and electrical properties of Cd1−x Mn x Te films by Huanhuan Ji; Jian Huang; Lin Wang; Junnan Wang; Jianming Lai; Run Xu; Jijun Zhang; Yue Shen; Jiahua Min; Linjun Wang; Yicheng Lu (444-447).
Cd1−x Mn x Te films were grown on SnO2:F (FTO)-coated glass substrates by close-spaced sublimation method. After deposition, the films were etched by Br-MeOH (BM) solution followed by two separate annealing processes. One was only carried out in N2 directly, and the other was further annealed in MnCl2. XRD, SEM, EDS and I–V measurement were employed to investigate the influences of post-annealing on the structure and properties of Cd1−x Mn x Te films. Uniform Cd1−x Mn x Te films with high quality and high resistivity were obtained by BM/N2 post-treatment.
Keywords: Cd1−x Mn x Te films; CSS; Post-treatment; Structure; Properties;
Study on the interfacial adhesion property of low-k thin film by the surface acoustic waves with cohesive zone model by Xia Xiao; Haiyang Qi; Ye Tao; Takamaro Kikkawa (448-454).
The cohesive zone model being increasingly used in discrete fracture processes simulation is adopted to study the interfacial adhesion property of low dielectric constant film deposited on the silicon substrate in this work. The two parameters, maximum normal traction and normal interface characteristic length in cohesive zone model, are taken into account to calculate the theoretical surface acoustic wave dispersion curves. Broadband surface acoustic wave signals with effective frequency up to 200 MHz are generated by short pulse ultraviolet laser source and detected by a piezoelectric transducer. The interfacial adhesion properties of dense and porous films determined accurately by matching the experimental dispersion curves with the calculated theoretical dispersion curves are 10.7 PPa/m and 2.8 PPa/m, respectively. The results show that the adhesion quality of dense low dielectric constant film is better than that of the porous. The study exhibits that the adhesion properties determined by improved laser-generated surface acoustic wave technique have the same trends with the test results of the nanoscratch technique, which indicates that the surface acoustic wave technique with cohesive zone model is a promising and nondestructive method for determining interfacial adhesion properties between low dielectric constant film and substrate.
Keywords: Interfacial adhesion property; Cohesive zone model; Surface acoustic waves (SAWs); Low-k film; Nondestructive;
The influence of surface oxygen and hydroxyl groups on the dehydrogenation of ethylene, acetic acid and hydrogenated vinyl acetate on pure Pd(1 0 0): A DFT study by Yanping Huang; Xiuqin Dong; Yingzhe Yu; Minhua Zhang (455-460).
On the basis of a Langmuir–Hinshelwood-type mechanism, the dehydrogenation of ethylene, acetic acid and hydrogenated vinyl acetate (VAH) on pure Pd(1 0 0) with surface oxygen atoms (Os) and hydroxyl groups (OHs) was studied with density functional theory (DFT) method. Our calculation results show that both Os and OHs can consistently reduce the activation energies of dehydrogenation of ethylene, acetic acid and VAH to some degree with only one exception that OHs somehow increase the activation energy of VAH. Based on Langmuir–Hinshelwood mechanism, the three dehydrogenation reactions in presence of surface Os and OHs are almost consistently favored, compared with the corresponding processes on clean Pd(1 0 0) surfaces, and thus a Langmuir–Hinshelwood-type mechanism may not be excluded beforehand when investigating the microscopic performance of the oxygen-assisted vinyl acetate synthesis on Pd(1 0 0) catalysts.
Keywords: Surface oxygen; Hydroxyl; Dehydrogenation; Ethylene; Acetic acid; Hydrogenated vinyl acetate;
Building high-coverage monolayers of covalently bound magnetic nanoparticles by Mackenzie G. Williams; Andrew V. Teplyakov (461-467).
This work presents an approach for producing a high-coverage single monolayer of magnetic nanoparticles using “click chemistry” between complementarily functionalized nanoparticles and a flat substrate. This method highlights essential aspects of the functionalization scheme for substrate surface and nanoparticles to produce exceptionally high surface coverage without sacrificing selectivity or control over the layer produced. The deposition of one single layer of magnetic particles without agglomeration, over a large area, with a nearly 100% coverage is confirmed by electron microscopy. Spectroscopic techniques, supplemented by computational predictions, are used to interrogate the chemistry of the attachment and to confirm covalent binding, rather than attachment through self-assembly or weak van der Waals bonding. Density functional theory calculations for the surface intermediate of this copper-catalyzed process provide mechanistic insight into the effects of the functionalization scheme on surface coverage. Based on this analysis, it appears that steric limitations of the intermediate structure affect nanoparticle coverage on a flat solid substrate; however, this can be overcome by designing a functionalization scheme in such a way that the copper-based intermediate is formed on the spherical nanoparticles instead. This observation can be carried over to other approaches for creating highly controlled single- or multilayered nanostructures of a wide range of materials to result in high coverage and possibly, conformal filling.
Keywords: “Click” reaction; High coverage; Magnetic nanoparticle functionalization;
Effect of multiple passes treatment in waterjet peening on fatigue performance by Azmir Azhari; Christian Schindler; Claudia Godard; Jens Gibmeier; Eberhard Kerscher (468-474).
The influence of waterjet peening on the residual stresses and fatigue performance of AISI 304 is investigated. The specimen surfaces were treated with multiple jet passes. The fatigue strength was evaluated using an alternating bending fatigue tester. The results of XRD measurements showed that a higher amount of compressive residual stresses is induced in the treated specimens. This strengthening layer is limited within the first 100 μm below the surface, which had been confirmed by micro hardness measurements. Even though the treated specimens showed compressive residual stresses the fatigue limit is lower than that of the untreated specimens. The roughness of the surface and the resulting notch effect seems to be stronger than the positive effect of the hardened layer.
Keywords: Waterjet peening; Compressive residual stresses; Multiple passes treatment; Surface roughness; Fatigue strength;
Influence of the substrate on the morphological evolution of gold thin films during solid-state dewetting by Patrick D. Nsimama; Andreas Herz; Dong Wang; Peter Schaaf (475-482).
The evolution of electron-beam evaporated Au thin films deposited on crystalline TiO2 (c-TiO2) and amorphous TiO2 (a-TiO2) as well as amorphous SiO2 substrates are investigated. The kinetic of dewetting is clearly dependent on the type of substrate and is faster on TiO2 substrates than on SiO2 substrates. This difference can result from the difference in adhesion energy. Furthermore, the kinetic of dewetting is faster on a-TiO2 than on c-TiO2, possibly due to the crystallization of TiO2 during annealing induced dewetting process. The morphologies of dewetted Au films deposited on crystalline TiO2 are characterized by branched holes. The XRD patterns of the Au films deposited on TiO2 substrates constituted peaks from both metallic Au and anatase TiO2. The activation energy of Au films deposited on crystalline TiO2 substrates was higher than that that of the films deposited on amorphous TiO2 substrates.
Keywords: Au; TiO2; Crystalline; Amorphous; Dewetting; Activation energy;
Corrosion and carburization behavior of Al-rich surface layer on Ni-base alloy in supercritical-carbon dioxide environment by Ho Jung Lee; Sung Hwan Kim; Hyunmyung Kim; Changheui Jang (483-490).
In order to improve the corrosion and carburization resistance in a high-temperature supercritical-carbon dioxide (S-CO2) environment, an Al-rich surface layer was developed on Alloy 600 by Al deposition and a subsequent high energy electron beam (EB) remelting. As a result of the EB surface treatment, an Al enriched (5–7 wt.%) micro-alloying zone (40 μm) was produced. When the EB surface-treated Alloy 600 was corroded in S-CO2 at 600 °C (20 MPa) for 500 h, the surface oxide layer mostly consisted of chromia (Cr2O3) with small amount of transition alumina (Al2O3). In addition, a carburized region of an amorphous C layer inter-mixed with the alumina was observed at the oxide/matrix interface. Meanwhile, when the EB surface-treated specimen was pre-oxidized in helium at 900 °C, α-alumina layer was formed on the surface, which showed superior corrosion and carburization resistance in S-CO2 environment. Therefore, it could be said that the presence of Al-rich surface layer alone is not enough to provide sufficient corrosion and carburization resistance in S-CO2 environment at 600 °C, unless pre-oxidation at higher temperature is applied to form a more protective α-alumina on the surface.
Keywords: EB surface treatment; Alumina; Corrosion; Supercritical-carbon dioxide; Carburization;
Synthesis of ZnO nanocoatings by decomposition of zinc acetate induced by electrons emitted by indium by Ladislav Svoboda; Richard Dvorský; Petr Praus; Dalibor Matýsek; Jiří Bednář (491-496).
In this work, a new method for the synthesis of ZnO nanocoatings is presented. It was tested for the nanocoating of silica nanoparticles forming core/shell SiO2/ZnO nanoparticles by the decomposition of zinc acetate in silica aqueous nanodispersions induced by electrons generated by a plate indium photocathode, which was irradiated with a UV Hg lamp with maximum intensity at the wavelength of 245 nm.The ZnO nanocoatings were examined by X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PLS), dynamic light scattering (DLS) and transmission electron microscopy (TEM). It was found that ZnO of hexagonal structure formed nanocoatings with the mean thickness of 13 nm. The photocatalytic activity of ZnO nanocoatings was verified by the photocatalytic decomposition of methylene blue (MB). Such nanocoating procedure based on the electron-induced decomposition of suitable metal salts could be a promising method for various applications in nanotechnology.
Keywords: ZnO nanocoatings; Silica nanoparticles; Core/shell; Indium; Zinc acetate;
Preparation of surface–modified lanthanum fluoride–graphene oxide nanohybrids and evaluation of their tribological properties as lubricant additive in liquid paraffin by Cuizhen Yang; Xiao Hou; Zhiwei Li; Xiaohong Li; Laigui Yu; Zhijun Zhang (497-502).
Oleic acid surface–modified Lanthanum trifluoride–graphene oxide (OA–LaF3–GO) nanohybrids were successfully prepared by surface modification technology. The morphology and phase structure of as-prepared samples were analyzed by means of X-ray diffraction and transmission electron microscopy, Fourier transform infrared spectrometry, Raman spectrometry and thermogravimetry. The results revealed that OA were bonded onto the surface of LaF3–GO nanohybrids. Subsequently, the tribological properties of OA–LaF3–GO nanohybrids as lubricant additive in liquid paraffin were evaluated with a four-ball machine, and the morphology and elemental composition of worn steel surfaces were examined on a scanning electron microscope with an energy dispersive spectrometer. Tribological results showed that OA–LaF3–GO nanohybrids had excellent friction reduction and antiwear ability at the loading of 0.5 wt.% OA–LaF3–GO nanohybrids, compared to liquid paraffin alone. The results of energy dispersive spectrometer revealed that improved tribological properties resulted from OA–LaF3–GO could transfer to the rubbed steel surface and decompose to form protective layers, which help to improve tribological properties.
Keywords: Surface modification; Lanthanum trifluoride; Graphene oxide; Nanohybrids; Tribological properties;
Microstructure and property of diamond-like carbon films with Al and Cr co-doping deposited using a hybrid beams system by Wei Dai; Jingmao Liu; Dongsen Geng; Peng Guo; Jun Zheng; Qimin Wang (503-509).
DLC films with weak carbide former Al and carbide former Cr co-doping (Al:Cr-DLC) were deposited by a hybrid beams system comprising an anode-layer linear ion beam source (LIS) and high power impulse magnetron sputtering using a gas mixture of C2H2 and Ar as the precursor. The doped Al and Cr contents were controlled via adjusting the C2H2 fraction in the gas mixture. The composition, microstructure, compressive stress, mechanical properties and tribological behaviors of the Al:Cr-DLC films were researched carefully using X-ray photoelectron spectroscopy, transmission electron microscopy, Raman spectroscopy, stress-tester, nanoindentation and ball-on-plate tribometer as function of the C2H2 fraction. The results show that the Al and Cr contents in the films increased continuously as the C2H2 fraction decreased. The doped Cr atoms preferred to bond with the carbon while the Al atoms mainly existed in metallic state. Structure modulation with alternate multilayer consisted of Al-poor DLC layer and Al-rich DLC layer was found in the films. Those periodic Al-rich DLC layers can effectively release the residual stress of the films. On the other hand, the formation of the carbide component due to Cr incorporation can help to increase the film hardness. Accordingly, the residual stress of the DLC films can be reduced without sacrificing the film hardness though co-doping Al and Cr atoms. Furthermore, it was found that the periodic Al-rich layer can greatly improve the elastic resilience of the DLC films and thus decreases the film friction coefficient and wear rate significantly. However, the existence of the carbide component would cause abrasive wear and thus deteriorate the wear performance of the films.
Keywords: Diamond-like carbon; Al:Cr co-doping; Residual stress; Elastic recovery; Tribology;
Microstructure and erosive wear behaviors of Ti6Al4V alloy treated by plasma Ni alloying by Z.X. Wang; H.R. Wu; X.L. Shan; N.M. Lin; Z.Y. He; X.P. Liu (510-516).
The Ni modified layers were prepared on the surface of Ti6Al4V substrate by the plasma surface alloying technique. The surface and cross-section morphology, element concentration and phase composition were investigated by thermal field emission scanning electron microscopy (SEM), and glow discharge optical emission spectroscopy (GDOES), X-ray diffraction (XRD), respectively. The cross-section nano-scale hardness of Ni modified layer was measured by nano indenter. The results showed that Ni modified layers exhibited triple layers structure and continuous gradient distribution of the concentration. From the surface to the matrix, they were 2 μm Ni deposition layer, 8 μm Ni-rich alloying layer including the phases of Ni3Ti, NiTi, Ti2Ni, AlNi3 and 24 μm Ni-poor alloying layer forming the solid solution of nickel. With increasing of the thickness of Ni modified layer, the microhardness increased first, reached the climax, then gradient decreased. The erosion tests were performed on the surface of the untreated and treated Ti6Al4V sample using MSE (Micro-slurry-jet Erosion) method. The experiment results showed that the wear rate of every layer showed different value, and the Ni-rich alloying layer was the lowest. The strengthening mechanism of Ni modified layer was also discussed.The Ni modified layers were prepared on the surface of Ti6Al4V substrate by the plasma surface alloying technique. The surface and cross-section morphology, element concentration and phase composition were investigated by thermal field emission scanning electron microscopy (SEM), and glow discharge optical emission spectroscopy (GDOES), X-ray diffraction (XRD), respectively. The cross-section nano-scale hardness of the Ni modified layer was measured by nanoindenter. The results showed that the Ni modified layers exhibited triple-layer structure and continuous gradient distribution of the concentration. From the surface to the matrix, they were 2 μm Ni deposition layer, 8 μm Ni-rich alloying layer including the phases of Ni3Ti, NiTi, Ti2Ni, AlNi3 and 24 μm Ni-poor alloying layer forming the solid solution of nickel. With increasing of the thickness of the Ni modified layer, the microhardness increased first, reached the climax, then gradient decreased. The erosion tests were performed on the surfaces of the untreated and treated Ti6Al4V samples using MSE (Micro-slurry-jet Erosion) method. The experiment results showed that the wear rate of every layer showed different values, and the Ni-rich alloying layer was the lowest. The strengthening mechanism of the Ni modified layer showed micro-cutting wearing.
Keywords: Ti6Al4V; Ni modified layer; Plasma alloying; Erosion;
The evolution of structure and defects in the implanted Si surface: Inspecting by reflective second harmonic generation by Sanjaya Brahma; Chung-Wei Liu; Kuang-Yao Lo (517-523).
Detailed information about the recrystallization and formation of defects in the ultra-shallow junction of implanted Si is a key for semiconductor fabrication below 20 nm regime. The surface quality of highly doped Si via annealing treatment would influence the fabrication and yield. Here, we employ nonlinear optics to study the correlated physical phenomena and underlying evolution of restructure of P+ ion implanted Si. Reflective second harmonic generation (RSHG) results reveal the restructure of the implanted Si layer that involves recrystallization, dopant activation and dopant diffusion in correlation with annealing temperature. In the implanted Si layer, defects cause inactivity in electrical properties and generate isotropic dipole contribution to the RSHG pattern. The trend of isotropic dipole contribution is consistent with the sheet resistance measurement that presents more information about the evolution of the restructure. At lower annealing temperatures, the precipitation and the interstitialcy pairs form due to the effect of transient enhanced diffusion, and then the isotropic contribution of the RSHG pattern and sheet resistance sharply increases because of aggregation of the dopants. The isotropic contribution of RSHG is an index of the transformation of the electrical property as well as estimate recrystallization during rapid thermal annealing.
Keywords: Implanted Si; Reflective second harmonic generation; Recrystallization; Defects; Sheet resistance; Electrical Properties;
Nondestructive analysis of lithographic patterns with natural line edge roughness from Mueller matrix ellipsometric data by Xiuguo Chen; Yating Shi; Hao Jiang; Chuanwei Zhang; Shiyuan Liu (524-530).
Mueller matrix ellipsometry (MME) is applied to characterize lithographic patterns with natural line edge roughness (LER). A computationally efficient approach based on effective medium approximation is proposed to model the effects of LER in MME measurements. We present both the theoretical and experimental results on lithographic patterns with realistic LER which demonstrate that MME in combination with the proposed effective modeling method is capable of quantifying LER amplitudes. Quantitative comparisons between the MME and scanning electron microscopy measured results also reveal the strong potential of this technique for in-line nondestructive line roughness monitoring.
Keywords: Line edge roughness; Effective medium approximation; Mueller matrix ellipsometry; Optical scatterometry; Nanometrology;
Comparison of rheological, mechanical, electrical properties of HDPE filled with BaTiO3 with different polar surface tension by Jun Su; Jun Zhang (531-538).
In this work, three types of coupling agents: isopropyl trioleic titanate (NDZ105), vinyltriethoxysilane (SG-Si151), 3-aminopropyltriethoxysilane (KH550) were applied to modify the surface tension of Barium titanate (BaTiO3) particles. The Fourier transform infrared (FT-IR) spectra confirm the chemical adherence of coupling agents to the particle surface. The long hydrocarbon chains in NDZ105 can cover the particle surface and reduce the polar surface tension of BaTiO3 from 37.53 mJ/m2 to 7.51 mJ/m2, turning it from hydrophilic to oleophilic properties. The short and non-polar vinyl groups in SG-Si151 does not influence the surface tension of BaTiO3, but make BaTiO3 have both hydrophilic and oleophilic properties. The polar amino in KH550 can keep BaTiO3 still with hydrophilic properties. It is found that SG-Si151 modified BaTiO3 has the lowest interaction with HDPE matrix, lowering the storage modulus of HDPE composites to the greatest extent. As for mechanical properties, the polar amino groups in KH550 on BaTiO3 surface can improve the adhesion of BaTiO3 with HDPE matrix, which increases the elongation at break of HDPE composites to the greatest extent. In terms of electrical properties, the polar amino groups on surface of BaTiO3 can boost the dielectric properties of HDPE/BaTiO3 composites and decrease the volume resistivity of HDPE/BaTiO3 composites. The aim of this study is to investigate how functional groups affect the rheological, mechanical and electrical properties of HDPE composites and to select a coupling agent to produce HDPE/BaTiO3 composites with low dielectric loss, high dielectric constant and elongation at break.
Keywords: High density polyethylene (HDPE); Barium titanate (BaTiO3); Surface tension; Rheology; Coupling agents; Mechanical and electrical properties;
Roll-to-roll DBD plasma pretreated polyethylene web for enhancement of Al coating adhesion and barrier property by Haibao Zhang; Hua Li; Ming Fang; Zhengduo Wang; Lijun Sang; Lizhen Yang; Qiang Chen (539-545).
The images of Al coating adhesion testes for (a) untreated and (b) roll-to-roll DBD plasma treated PE.In this paper the roll-to-roll atmospheric dielectric barrier discharge (DBD) was used to pre-treat polyethylene (PE) web surface before the conventional thermal evaporation aluminum (Al) was performed as a barrier layer. We emphasized the plasma environment effect based on the inlet three kinds of reactive monomers. The cross hatch test was employed to assess the Al coating adhesion; and the oxygen transmission rate (OTR) was used to evaluate gas barrier property. The results showed that after roll-to-roll DBD plasma treatment all Al coatings adhered strongly on PE films and were free from pinhole defects with mirror morphology. The OTR was reduced from 2673 cm3/m2 day for Al-coated original PE to 138 cm3/m2 day for Al-coated allyamine (C3H7N) modified PE. To well understand the mechanism the chemical compositions of the untreated and DBD plasma pretreated PE films were analyzed by X-ray photoelectron spectroscopy (XPS). The surface topography was characterized by atomic force microscopy (AFM). For the property of surface energy the water contact angle measurement was also carried out in the DBD plasma treated samples with deionized water.
Keywords: Barrier web; Adhesion; Permeation properties; Surface modification; DBD plasma;
Surface characteristics of Ti–6Al–4V alloy by EDM with Cu–SiC composite electrode by L. Li; L. Feng; X. Bai; Z.Y. Li (546-550).
Ti–6Al–4V alloy is widely used in many industries due to its outstanding properties. However, it has poor machinability using conventional mechanical cutting process. Electrical discharge machining is an alternative competitive process to machine titanium alloy by electrical erosion. This article studies the machining characteristics of Ti–6Al–4V with Cu–SiC composite electrode. Surface topography, subsurface microstructure, energy dispersive spectroscopy analysis, and micro-hardness have been analyzed. The machined surfaces show irregular compound structures, droplets of debris, shallow craters, and micro-pores. The surfaces processed by Cu–SiC electrode have fewer number of microcracks compared with that by Cu electrode. Continuous and uniform hardened layer can be achieved by Cu–SiC electrode. The hardened layer has significantly higher hardness than the bulk material because the new phases of TiC and TiSi2 were created on the surface.
Keywords: Ti–6Al–4V alloy; Electrical discharge machining; Cu–SiC electrode;
Morphological variation of stimuli-responsive polypeptide at air–water interface by Sungchul Shin; Sungmin Ahn; Jie Cheng; Hyejin Chang; Dae-Hong Jung; Jinho Hyun (551-556).
The morphological variation of stimuli-responsive polypeptide molecules at the air–water interface as a function of temperature and compression was described. The surface pressure–area (π–A) isotherms of an elastin-like polypeptide (ELP) monolayer were obtained under variable external conditions, and Langmuir–Blodgett (LB) monolayers were deposited onto a mica substrate for characterization. As the compression of the ELP monolayer increased, the surface pressure increased gradually, indicating that the ELP monolayer could be prepared with high stability at the air–water interface. The temperature in the subphase of the ELP monolayer was critical in the preparation of LB monolayers. The change in temperature induced a shift in the π–A isotherms as well as a change in ELP secondary structures. Surprisingly, the compression of the ELP monolayer influenced the ELP secondary structure due to the reduction in the phase transition temperature with decreasing temperature. The change in the ELP secondary structure formed at the air–water interface was investigated by surface-enhanced Raman scattering. Moreover, the morphology of the ELP monolayer was subsequently imaged using atomic force microscopy. The temperature responsive behavior resulted in changes in surface morphology from relatively flat structures to rugged labyrinth structures, which suggested conformational changes in the ELP monolayers.
Keywords: Elastin-like polypeptide (ELP); Langmuir–Blodgett (LB) monolayer; Morphological variation; Conformational change;
The roles of buffer layer thickness on the properties of the ZnO epitaxial films by Kun Tang; Shimin Huang; Shulin Gu; Shunming Zhu; Jiandong Ye; Zhonghua Xu; Youdou Zheng (557-564).
In this article, the authors have investigated the optimization of the buffer thickness for obtaining high-quality ZnO epi-films on sapphire substrates. The growth mechanism of the buffers with different thickness has been clearly revealed, including the initial nucleation and vertical growth, the subsequent lateral growth with small grain coalescence, and the final vertical growth along the existing larger grains. Overall, the quality of the buffer improves with increasing thickness except the deformed surface morphology. However, by a full-scale evaluation of the properties for the epi-layers, the quality of the epi-film is briefly determined by the surface morphology of the buffer, rather than the structural, optical, or electrical properties of it. The best quality epi-layer has been grown on the buffer with a smooth surface and well-coalescent grains. Meanwhile, due to the huge lattice mismatch between sapphire and ZnO, dislocations are inevitably formed during the growth of buffers. More importantly, as the film grows thicker, the dislocations may attracting other smaller dislocations and defects to reduce the total line energy and thus result in the formation of V-shape defects, which are connected with the bottom of the threading dislocations in the buffers. The V-defects appear as deep and large hexagonal pits from top view and they may act as electron traps which would affect the free carrier concentration of the epi-layers.
Keywords: Zinc oxide; Epitaxy; Sapphire; Buffer layer; MOCVD; Material characterizations;
Thermal stability of hydrogenated diamond films in nitrogen ambience studied by reflection electron energy spectroscopy and X-ray photoelectron spectroscopy by Bing Ren; Jian Huang; Hongze Yu; Weichuan Yang; Lin Wang; Zhangmin Pan; Linjun Wang (565-570).
(1 1 0)-oriented diamond films were grown by microwave plasma chemical vapor deposition technique, followed by an optimized hydrogen-plasma treatment process. Thermal stability of hydrogenated diamond films were studied by annealing in nitrogen atmosphere at temperature varied from 400 to 950 °C. Reflection electron energy spectroscopy associated with X-ray photoelectron spectroscopy indicates that approximate at. 50% hydrogen was present at the surface of hydrogenated diamond films, which is close to the theoretical value. Pinning effect in surface Fermi level in hydrogenated diamond films could not be eliminated by annealing in nitrogen until the temperature was exceeded 950 °C. The films underwent hydrogen desorption and subsequent graphitization mainly on the very surface region without significant bulk modification. Besides, hydrogenated diamond films annealed in N2 at 950 °C showed similar hydrophilicity and resistance to that of the oxidized one, indicating rupture of C-H bond on the surface of hydrogenated diamond films.
Keywords: Hydrogenated diamond films; Thermal stability; REELS; Rapid annealing;
Preparation and high-temperature oxidation behavior of plasma Cr–Ni alloying on Ti6Al4V alloy based on double glow plasma surface metallurgy technology by Dong-Bo Wei; Ping-Ze Zhang; Zheng-Jun Yao; Xiang-Fei Wei; Jin-Tang Zhou; Xiao-Hu Chen (571-578).
To improve the oxidation resistance of Ti6Al4V alloy, it was coated with a Cr–Ni alloy with 20, 40, 60, and 80 at.% Ni content using the double-glow plasma surface metallurgy technology. The coatings were dense, uniform, and compact, including a complete structure of deposited layer, interdiffusion layer, and sputtering-affected zone. The effect of Ni content on the isothermal oxidation behavior of coating was investigated at 750, 850, and 950 °C. The results show that the oxide scale consisted of NiO and Cr2O3. The morphology and distribution of NiO in oxide scale were affected by oxidation temperature and Ni content. When the Ni content was ≤40 at.%, the oxidation resistance of the Cr–Ni alloy coating was enhanced.
Keywords: Plasma surface alloying; High-temperature oxidation-resistant coatings; Titanium alloys; Diffusion;
Improvement in temperature dependence and dielectric tunability properties of PbZr0.52Ti0.48O3 thin films using Ba(Mg1/3Ta2/3)O3 buffer layer by Zhi Wu; Jing Zhou; Wen Chen; Jie Shen; Huimin Yang; Shisai Zhang; Yueli Liu (579-583).
In this paper, Pb(Zr0.52Ti0.48)O3 (PZT) thin films were prepared via sol-gel method. The effects of Ba(Mg1/3Ta2/3)O3 (BMT) buffer layer on the temperature dependence and dielectric tunability properties of PZT thin films were studied. As the thickness of BMT buffer layer increases, the tan δ and tunability of PZT thin films decrease while tunability still maintains above 10%. This result shows that BMT buffer layer can improve the dielectric tunability properties of PZT thin films. Furthermore, the temperature coefficient of the dielectric constant decreases from 2333.4 to 906.9 ppm/°C with the thickness of BMT buffer layer increasing in the range from 25 to 205 °C, indicating that BMT buffer layer can improve the temperature stability of PZT thin films. Therefore, BMT buffer layer plays a critical role in improving temperature dependence and dielectric tunability properties of PbZr0.52Ti0.48O3 thin films.
Keywords: PZT thin films; BMT buffer layer; Temperature dependence; Dielectric tunability properties; Sol–gel method;
Reconstruction of GaAs/AlAs supperlattice multilayer structure by quantification of AES and SIMS sputter depth profiles by H.L. Kang; J.B. Lao; Z.P. Li; W.Q. Yao; C. Liu; J.Y. Wang (584-588).
The GaAs/AlAs superlattice multilayer structures were deposited on GaAs (1 0 0) substrates by molecular beam epitaxial (MBE) technique. The as-prepared samples were characterized respectively by Auger Electron Spectroscopy (AES) and Secondary Ion Mass Spectroscopy (SIMS) depth profiling techniques. The measured depth profiles were then fitted by the Mixing-Roughness-Information (MRI) model. The depth resolution values for both depth profiling techniques were evaluated quantitatively from the fitted MRI parameters and the as-prepared GaAs/AlAs multilayer structure was determined accordingly.
Keywords: GaAs/AlAs superlattice; AES; SIMS; Depth profiling; MRI model;
A novel intermediate layer for Au/CdZnTe/FTO photoconductive structure by Yuelu Zhang; Linjun Wang; Run Xu; Jian Huang; Jun Tao; Hua Meng; Jijun Zhang; Jiahua Min (589-592).
In this work, graphene is tried to use to improve the performance of polycrystalline CdZnTe high-energy radiation and photon detectors. A graphene intermediate layer is prepared by spin-coating process on the surface of polycrystalline CdZnTe film, which forms a photoconductive Au/graphene/CdZnTe/FTO structure. XRD, Raman, photoelectric response and other characterisation methods are adopted to investigate the effect of graphene layer on the electrical characteristics and UV photo-response performance of CdZnTe photoconductive structure. It is demonstrated that graphene layer can significantly improve the contact property of Au/CdZnTe structure, and obviously enhance its UV photo-response and the UV sensitivity increased with one order of magnitude.
Keywords: CdZnTe; Thick films; Graphene; Photoconductive device;
Simulation optimization of filament parameters for uniform depositions of diamond films on surfaces of ultra-large circular holes by Xinchang Wang; Xiaotian Shen; Fanghong Sun; Bin Shen (593-603).
Chemical vapor deposition (CVD) diamond films have been widely applied as protective coatings on varieties of anti-frictional and wear-resistant components, owing to their excellent mechanical and tribological properties close to the natural diamond. In applications of some components, the inner hole surface will serve as the working surface that suffers severe frictional or erosive wear. It is difficult to realize uniform depositions of diamond films on surfaces of inner holes, especially ultra-large inner holes. Adopting a SiC compact die with an aperture of Ф80 mm as an example, a novel filament arrangement with a certain number of filaments evenly distributed on a circle is designed, and specific effects of filament parameters, including the filament number, arrangement direction, filament temperature, filament diameter, circumradius and the downward translation, on the substrate temperature distribution are studied by computational fluid dynamics (CFD) simulations based on the finite volume method (FVM), adopting a modified computational model well consistent with the actual deposition environment. Corresponding temperature measurement experiments are also conducted to verify the rationality of the computational model. From the aspect of depositing uniform boron-doped micro-crystalline, undoped micro-crystalline and undoped fine-grained composite diamond (BDM-UMC-UFGCD) film on such the inner hole surface, filament parameters as mentioned above are accurately optimized and compensated by orthogonal simulations. Moreover, deposition experiments adopting compensated optimized parameters and some typical contrastive parameters are also accomplished for further verifying the rationality of the computational model and the correctness of the compensation coefficient 0.7 defined for the downward translation determined by simulations. More importantly, on the basis of more simulations and verification tests, a general filament arrangement model suitable for Ф50–120 mm circular inner holes is determined, involving all above filament parameters that are functionally dependent on the diameter of the inner hole.
Keywords: Ultra-large circular hole; Simulation; Substrate temperature distribution; Filament arrangement; Composite diamond film;