Frontiers of Materials Science (v.7, #4)

Over the past decade, there has been tremendous progress in developing advanced biomaterials for tissue repair and regeneration. This article reviews the frontiers of this field from two closely related areas, new engineering materials for bone substitution and biomimetic mineralization for bone-like nanocomposites. Rather than providing an exhaustive overview of the literature, we focus on several representative directions. We also discuss likely future trends in these areas, including synthetic biology-enabled biomaterials design and multifunctional implant materials for bone repair and regeneration.
Keywords: bone; engineering material; biomimetic material; implant; biomineralization

Surface engineering of synthetic nanopores by atomic layer deposition and their applications by Ce-Ming Wang; De-Lin Kong; Qiang Chen; Jian-Ming Xue (335-349).
In the past decade, nanopores have been developed extensively for various potential applications, and their performance greatly depends on the surface properties of the nanopores. Atomic layer deposition (ALD) is a new technology for depositing thin films, which has been rapidly developed from a niche technology to an established method. ALD films can cover the surface in confined regions even in nanoscale conformally, thus it is proved to be a powerful tool to modify the surface of the synthetic nanopores and also to fabricate complex nanopores. This review gives a brief introduction on nanopore synthesis and ALD fundamental knowledge, and then focuses on the various aspects of synthetic nanopores processing by ALD and their applications, including single-molecule sensing, nanofluidic devices, nanostructure fabrication and other applications.
Keywords: synthetic nanopore; atomic layer deposition (ALD); surface engineering

Electrospinning of curcumin loaded chitosan/poly (lactic acid) nanofilm and evaluation of its medicinal characteristics by Bhaarathi Dhurai; Nachimuthu Saraswathy; Ramasamy Maheswaran; Ponnusamy Sethupathi; Palanisamy Vanitha; Sukumar Vigneshwaran; Venugopal Rameshbabu (350-361).
The curcumin loaded chitosan/poly (lactic acid) (PLA) nanofibers were produced using electrospinning. Box—Behnken experimental design was used for the optimization of variables (−1, 0, + 1 coded level) like chitosan/PLA strength (% w/v), curcumin strength (% w/v) and applied voltage (kV) to obtain uniform fiber diameter. The morphology of nanofibers was shown by SEM. Molecular interactions and the presence of each chemical compound of curcumin loaded chitosan/PLA fibers were characterized by FTIR and EDX analysis. Antioxidant, drug release and in vitro cytotoxicity tests were performed to evaluate the suitability of nanofibers that would be used for wound healing. In vivo wound healing studies on excision and incision wounds created on rat model showed significant reduction of wound area when compared to untreated. The better healing efficiency can be attributed to the presence of curcumin and chitosan.
Keywords: Box-Behnken; chitosan; curcumin; electrospinning; poly (lactic acid) (PLA)

A novel method has been developed to rapidly deposit bone-like apatite with the assistance of ultraviolet (UV) light irradiation on the nanostructured titania in the simulated body fluid (SBF). The process has three main steps: Ti-24Nb-4Zr-7.9Sn alloy was heated at 650°C for 3 h, UV-light illumination in air for 4 h and soaking in the SBF for 3 d. A titania coating consisted of main rutile formed on the thermal oxidized Ti-24Nb-4Zr-7.9Sn alloy. The UV not only converted the rutile surface from hydrophilic to hydrophobic but also stimulated high surface activity. After 4 h UV illumination, the contents of Ti3+ and hydroxyl groups on the oxidized sample were increased, while that of lattice O decreased. After 3 d of soaking in the SBF, a compact and uniform layer of carbonated hydroxyapatite (CHA) particles was formed on the UV-illuminated rutile surface whereas there was a few of HA to be viewed on the surface of as-oxidized Ti-24Nb-4Zr-7.9Sn alloy. Our study demonstrates a simple, fast and cost-effective technique for growing bone-like apatite on titanium alloys.
Keywords: Ti-24Nb-4Zr-7.9Sn alloy; thermal oxidation; UV illumination; rutile; bonelike apatite

The effect of calcination temperature on the capacitive properties of WO3-based electrochemical capacitors synthesized via a sol-gel method by Diah Susanti; Rizky Narendra Dwi Wibawa; Lucky Tananta; Hariyati Purwaningsih; Rindang Fajarin; George Endri Kusuma (370-378).
Electrochemical capacitor (EC) is a promising energy storage device which can be hybridized with other energy conversion or energy storage devices. One type of ECs is pseudocapacitor made of metal oxides. WO3 is an inexpensive semiconductor metal oxide which has many applications. However the application of WO3 as an EC material was rarely reported. Therefore in this research EC was prepared from WO3 nanomaterial synthesized by a sol-gel process. The WO3 gel was spin-coated on graphite substrates and calcined at various temperatures of 300°C, 400°C, 500°C and 600°C for 1 h. Cyclic voltammetry (CV) measurements were used to observe the capacitive property of the WO3 samples. SEM, XRD, FTIR and Brunauer-Emmett-Teller (BET) analyses were used to characterize the material structures. WO3 calcined at 400°C was proved to have the highest capacitance of 233.63 F·g−1 (1869 mF·cm−2) at a scan rate of 2 mV·s−1 in 1 mol/L H2SO4 between potentials −0.4 and 0.4 V vs. SCE. Moreover it also showed the most symmetric CV curves as the indication of a good EC. Hence WO3 calcined at 400°C is a potential candidate for EC material of pseudocapacitor type.
Keywords: electrochemical capacitor (EC); WO3 nanomaterial; sol-gel process; calcination

Photoelectrochemical behaviour of CdIn2S4 films deposited by pulse electrodeposition using non-aqueous electrolyte by Chockalingam Jayanthi; Swaminathan Dhanapandian; Kollegal Ramakrishna Murali (379-386).
CdIn2S4 films were deposited by the pulse electrodeposition technique on tin oxide-coated glass substrates, at different duty cycles in the range of 6%–50%. The deposition potential was −0.7 V vs. saturated calomel electrode (SCE) using non-aqueous di(ethylene glycol) electrolyte. XRD analysis of the films indicated polycrystalline nature. Grain size, strain and dislocation density were evaluated from the XRD data. EDX analysis of the surface composition confirms the formation of stoichiometric CdIn2S4 films. Optical studies show a direct band-gap values in the range of 2.14–2.23 eV for the films deposited at different duty cycles. Room temperature resistivity of the films was in the range of 40–21 Ω·cm with the increase of duty cycle. Photoelectrochemical (PEC) solar cells constructed with the films deposited at 50% duty cycle and post-heat-treated at 500°C indicated open circuit voltage (V oc) of 0.595 V, short circuit current density (J sc) of 6.20 mA·cm−2, fill factor (ff) of 0.61, efficiency (η) of 3.75%, series resistance (R s) of 4 Ω and shunt resistance (R sh) of 2.50kΩ. Making use of the advantages of pulse electrodeposition it can be used to deposit nanocrystalline films which can be employed in optoelectronic and photovoltaic devices.
Keywords: thin film; semiconductor; CdIn2S4 ; photoelectrochemical (PEC) cell

Effect of Sn precursor on the synthesis of SnO2 and Sb-doped SnO2 particles via polymeric precursor method by Francisco López Morales; Teresa Zayas; Oscar E. Contreras; Leonardo Salgado (387-395).
SnO2 and Sb-doped SnO2 particles were synthesized using the polymeric precursor method with different Sn salt precursors: SnCl2·2H2O, SnCl4·5H2O, or Sn citrate. Sb2O3 was used as the precursor of Sb, and the molar ratio of n Sn:n Sb was held constant. FTIR and TGA/DTA were used to examine the influence of the Sn precursor on the formation and thermal decomposition of the Sn and Sn-Sb complexes. The calcination products obtained from heating the Sn and Sn-Sb complexes at 500°C in air were analyzed using XRD and TEM analysis. The results revealed that the SnO2 and Sb-doped SnO2 formation temperatures depended on the nature of the Sn precursor. The calcination products were found to be SnO2 and Sb-doped SnO2 particles, which crystallized in a tetragonal cassiterite structure with a highly preferred (110) planar orientation. The Sn precursor and the presence of Sb in the SnO2 matrix strongly influenced the crystallinity and lattice parameters.
Keywords: SnO2 and Sb-doped SnO2 ; Sn precursor; Pechini method; thermal decomposition; nanoparticle

Mechanical behavior of organo-modified Indian bentonite nanoclay fiber-reinforced plastic nanocomposites by N. Raghavendra; H. N. Narasimha Murthy; M. Krishna; K. R. Vishnu Mahesh; R. Sridhar; S. Firdosh; G. Angadi; S. C. Sharma (396-404).
The aim of the research was to examine the influence of organo-modified Indian bentonite (IB) nanoclay dispersed in vinylester on the mechanical properties of nanoclay/vinylester/glass nanocomposites. Nanoclay was organically modified using cationic surfactant hexadecyltrimethylammonium bromide (HDTMA-Br) by cation exchange method and dispersed in vinylester using ultrasonication and twin screw extrusion. XRD of nanoclay/vinylester revealed exfoliation at 4 wt.% nanoclay indicating uniform dispersion in the polymer. DSC results showed improvement in glass transition temperature by 22.3% in 4 wt.% nanoclay/vinylester/glass when compared with that of vinylester/glass. Nanoclay/vinylester/glass with 4 wt.% nanoclay showed 29.23%, 23.84% and 60.87% improvement in ultimate tensile strength (UTS), flexural strength (FS) and interlaminar shear strength (ILSS) respectively when compared with those of vinylester/glass. The mode of tensile failure examined by SEM showed no agglomeration of nanoclay in 4 wt.% nanoclay/vinylester/glass specimens.
Keywords: Indian bentonite (IB); ultrasonication; twin-screw extrusion; mechanical property

Energy investigations on the mechanical properties of magnesium alloyed by X = C, B, N, O and vacancy by Xiao-Zhi Wu; Li-Li Liu; Rui Wang; Li-Yong Gan; Qing Liu (405-412).
The generalized stacking fault (GSF) energies and surface energies of magnesium and its alloys with alloying atoms X = C, B, N, O and vacancy have been investigated using the first-principles methods. It is found that the predominant reducing effects of the alloying atoms and vacancy on the stacking fault energy are resulted from the position of them in the 1st layer near the slip plane. The stacking fault energies are nearly the same as the pure magnesium while the alloying atoms and vacancy are placed in the 2nd, 3rd, 4th, 5th and 6th layers. It has been shown that O strongly reduces the GSF energy of Mg. The alloying atoms C, B and N increase the surface energy, but O and vacancy reduce the surface energy of Mg. The ductilities of Mg and Mg alloys have been discussed based on the Rice criterion by using the ratio between surface energy and unstable stacking fault energy.
Keywords: magnesium; stacking fault energy; surface energy; Rice criterion

Six non-oriented steel sheets of similar grade produced by different steel companies were used to analyze the magnetic aging behaviors after aging at 200°C for 48 h. It was observed that tiny S atoms, besides C and N, could also induce certain increase of core loss during aging. Thermodynamic calculation indicated that the nucleation driving force of FeS is much higher than those of Fe3C and Fe4N at low temperature, while S atoms, which tend to segregated around dislocations and boundaries, would diffuse rapidly along the crystalline defects while FeS particles would form. Therefore, higher content of tiny S atoms could increase core loss during service time of non-oriented steel sheets.
Keywords: non-oriented electrical steel; sulfur diffusion; magnetic aging; core loss