Inorganic Materials (v.46, #10)
Epitaxial growth of silicon whiskers without tapering at the base by V. A. Nebol’sin; A. I. Dunaev; E. V. Zotova; M. A. Zavalishin (1039-1044).
Based on the measured parameters of the tapered portion (pedestal) at the base of silicon whiskers, we show that the tapering is the consequence of the increase in the contact angle of the liquid droplet and is due to the fact that the surface free energy of the three-phase system is constant (zero increment) during whisker growth. The growth angle of nanowhiskers should depend on their cross-sectional size because of the effect of the line tension at the three-phase boundary. A procedure is proposed for whisker growth without tapering at the base.
Effect of electroactive nickel on the low-temperature annealing behavior of silicon by E. A. Jafarova; E. S. Taptygov; Z. A. Iskenderzade (1045-1048).
We have studied the effect of low-temperature annealing on the behavior of electroactive nickel in silicon. The results demonstrate that the state of electroactive nickel centers in silicon is stable up to 200°C. Starting at 300°C, the SiNi solid solution decomposes and the electroactive nickel concentration decreases. From low-temperature (t > 200°C) annealing kinetics, the activation energy for the annealing of a deep center at E c − 0.41 eV is estimated at 1.2–1.5 eV. The decomposition rate of the SiNi solid solution increases with temperature.
Preparation and properties of Mn1.5 − x Cu x Sb and Mn1.5 − x Zn x Sb solid solutions with the B8 structure by M. Budzyński; V. I. Mitsiuk; V. V. Ryzhkovskii; Z. Surowiec; T. M. Tkachenko (1049-1053).
Mn1.5 − x Cu x Sb (x ≤ 0.30) and Mn1.5 − x Zn x Sb (x ≤ 0.10) solid solutions have been prepared using high-pressure high-temperature processing, and their structural and magnetic properties have been studied. The results of magnetic and Mössbauer measurements indicate that the interatomic magnetic interactions in the solid solutions are markedly weaker compared to those prepared by direct melting of elemental mixtures.
Photoluminescence and raman spectra of (Ga2S3)0.95(Sm2O3)0.05 crystals by A. N. Georgobiani; B. G. Tagiev; O. B. Tagiev; Kh. B. Ganbarova; U. F. Kasumov (1054-1056).
We have measured the photoluminescence and Raman spectra of (Ga2S3)0.95(Sm2O3)0.05 crystals and identified the mechanism of the energy transfer from the host to the rare-earth ion and the vibrational modes of the constituent atoms.
Se-TlPrSe3 phase diagram by C. A. Veliev (1057-1060).
The Se-TlPrSe3 system has been studied using differential thermal analysis, X-ray diffraction, microstructural analysis, microhardness tests, and density measurements, and its phase diagram has been constructed. The Se-TlPrSe3 system is shown to be partially nonpseudobinary. The system contains α-TlPrSe3-based solid solutions with a boundary at 8 mol % Se. The Se solubility in TlPrSe3 is insignificant. α-TlPrSe3 has a tetragonal structure with lattice parameters a = 8.87 Å and c = 7.96 Å (ρmeas = 7.36 g/cm3, and ρx = 7.71 g/cm3).
Synthesis and properties of SnTe-PrTe solid solutions by E. M. Gojaev; M. I. Murguzov; I. M. Mamedov; A. A. Abdurragimov (1061-1064).
A partial phase diagram of the SnTe-PrTe system has been constructed. The system is shown to contain SnTe-based solid solutions. The electrical conductivity, Hall coefficient, thermoelectric power, and thermal conductivity of the SnTe-PrTe alloys containing 1, 2, and 3 mol % PrTe have been measured as functions of temperature, and their thermoelectric figure of merit has been determined.
Molecular beam epitaxy of Pb1 − x Eu x Te and Pb1 − x Sn x Te layers and related periodic structures by Yu. G. Selivanov; E. G. Chizhevskii; V. P. Martovitskiy; A. V. Knotko; I. I. Zasavitskii (1065-1071).
Layers and periodic Bragg structures based on Pb1 − x Eu x Te (0 < x < 1) and Pb1 − x Sn x Te (0 < x < 0.1) ternary solid solutions have been grown on (111) BaF2 and (111) Si substrates by molecular beam epitaxy. X-ray diffraction measurements show that the layers in three-period EuTe/Pb0.94Eu0.06Te structures maintain the  crystallographic orientation normal to the substrate plane. In the interface plane, the  directions of the layers and substrate are parallel to each other. The full width at half maximum of the rocking curve of each layer of both the binary and ternary compounds is about 20′. The large optical contrast (40%) in such structures allowed us to reach 99.9% mid-IR reflectivity.
Effect of morphology of catalyst thin film on carbon nanotube growth by Gang Li (1072-1076).
The Ni catalyst films were deposited on single crystal Si by magnetron sputtering system. The surface morphologies of the films were controlled by varying the pretreatment temperature in NH3. We have investigated how the morphology of Ni after thermal treatment influences on the vertically aligned carbon nanotubes growth during thermal chemical vapor deposition. We found that the pretreatment temperature determined the grain size and density of the Ni catalyst that controlled the diameter, length, and density of carbon nanotubes. The degree of crystallization and order of the CNTs as a function of pretreatment temperature was further discussed by Raman spectrums. We found that more aligned and ordered samples correspond to lower I D/I G ratios.
Acid functionalization of carbon nanofibers by Nguyen Tran Hung; Nguyen Mang Tuong; E. G. Rakov (1077-1083).
We have studied the effects of temperature (70–100°C), process duration (1–4 h), and the ratio of the acid mixture (concentrated HNO3 and H2SO4 in the volume ratio 1: 3) volume to carbon nanofiber weight (70: 1 to 133: 1 ml/g) on the yield of functionalization products and their dispersibility in water. The results indicate that, with increasing temperature and process duration, the yield of functionalization products decreases, and their concentration (“solubility”) in the aqueous dispersion increases: from 1.2–1.3 to 11.0 mg/ml when the yield decreases from 71–89 to 30%. We present the first measurements of the gas volume evolved during functionalization and show that it increases with increasing temperature and process duration, reaching 500–600 ml/g carbon under the most severe conditions. The major component of the reaction gases is CO2 (over 50 vol %).
Conversion of graphite intercalation compounds to carbon materials containing polymetallic nanoparticles by A. V. Dunaev; A. I. Chikin; K. V. Pokholok; D. S. Filimonov; I. V. Arkhangel’skii (1084-1089).
We report the formation of ternary graphite intercalation compounds (GICs) with FeCl3 and PtCl4 via reaction between hexachloroplatinic acid and a binary GIC with iron(III) chloride. Mössbauer spectroscopy and X-ray microanalysis results show that ternary GICs form only when the interlayer spaces in the parent binary GIC are incompletely occupied (stage III or lower). The coexistence of different chloride molecules in the ternary GIC leads to the formation of intermetallic nanoparticles when the material is reduced. The yield of the intermetallic phase increases with decreasing graphite particle size.
Thermodynamic study on codeposition of ZrC-SiC from MTS-ZrCl4-CH4-H2 by Q. M. Liu; L. T. Zhang; J. Liu; Y. G. Wang (1090-1095).
Thermodynamic equilibrium condensed phases for chemical vapor deposition of ZrC-SiC from the MTS-ZrCl4-CH4-H2 system were calculated by FactSage programs based on Gibbs free energy minimization of the reaction system. The deposition phase diagrams, which indicated the condense phases, were constructed according to the calculation results. The effects of temperature and partial pressure of precursors on the final condensed phases were studied. The results indicate that the codeposition is more effective in the presence of an independent carbon source, CH4, with a reasonable partial pressure than in the absence of CH4. The experimental results are in good agreement with the thermodynamic calculation results.
Synthesies and properties of Tb-doped GaN nanowires by Y. P. Cao; F. Shi; X. W. Xiu; H. B. Sun; Y. F. Guo; W. J. Liu; Chengshan Xue (1096-1099).
The synthesis of Tb-doped GaN nanowires on Si (111) substrates through ammoniating Ga2O3 films doped with Tb was investigated. X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope, high-resolution transmission electron microscopy and photoluminescence were used to characterize the composition, structure, morphology and optical properties of the products. The results show that the as-synthesized GaN nanowires doped with 3 at % Tb are of single-crystalline hexagonal wurtzite structure. The nanowires have diameters ranging from 30 to 50 nm and the lengths up to tens of micrometers. An f-f intra-atomic transition of rare earth at 545 nm corresponding to 5 D 4–7 F 5 of the Tb3+ and other two peaks related with doping are observed in PL spectrum, confirming the doping of Tb into GaN. The growth mechanism of GaN nanowires was discussed briefly.
Materials based on modified SnO2 for selective gas sensors by V. V. Krivetskiy; A. Ponzoni; E. Comini; S. M. Badalyan; M. N. Rumyantseva; A. M. Gaskov (1100-1105).
This paper presents an approach to improving the selectivity of gas sensors based on nanocrystalline tin dioxide. We demonstrate that chemical modification of the surface of SnO2 crystallites with catalytic metal oxide and gold clusters considerably enhances the selectivity of their sensing response to a variety of reducing gases at gas concentrations near the maximum permissible level. This approach can be used to produce “electronic nose” multisensor arrays.
Fast microwave synthesis of Fe3O4 and Fe3O4/Ag magnetic nanoparticles using Fe2+ as precursor by Baozhan Zheng; Minghui Zhang; Dan Xiao; Yong Jin; Martin M. F. Choi (1106-1111).
A simple and quick microwave method to prepare high performance magnetite nanoparticles (Fe3O4 NPs) directly from Fe has been developed. The as-prepared Fe3O4 NPs product was fully characterized by X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The results show that the as-prepared Fe3O4 NPs are quite monodisperse with an average core size of 80 × 5 nm. The microwave synthesis technique can be easily modified to prepare Fe3O4/Ag NPs and these NPs possess good magnetic properties. The formation mechanisms of the NPs are also discussed. Our proposed synthesis procedure is quick and simple, and shows potential for large-scale production and applications for catalysis and biomedical/biological uses.
Gas-sensing properties of nanostructured M x V2O5 (M = Na, K, Rb, Cs) oxides by Yu. A. Bakhteeva; N. V. Podval’naya; V. L. Volkov (1112-1114).
The gas-sensing properties of nanostructured vanadium oxide doped with alkali-metal cations (M x V2O5 with M = Na, K, Rb, and Cs) have been studied by measuring the resistance of films as a function of analyte content using an impedance meter. The results show that the doped vanadium oxide is sensitive to hydrogen, carbon monoxide, and ammonia in the concentration ranges 0.1–80, 0.1–5, and 0.1–5 vol %, respectively. The strongest gas response is offered by Rb0.47V2O5, which is due to the smallest interlayer spacing in the structure of this nanomaterial and to its larger specific surface area.
Synthesis and magnetic properties of M0.08Ti0.91V0.09O2 + δ · nH2O (M = Cr, Mn, Fe, Co, Ni) nanopowders by G. S. Zakharova; V. L. Volkov; M. A. Uimin; A. A. Mysik; A. E. Ermakov (1115-1120).
Using sol-gel synthesis and ion exchange, we have prepared titanium vanadium oxide nanopowders doped with transition-metal ions: M0.08Ti0.91V0.09O2 + δ · nH2O with M = Cr, Mn, Fe, Co, and Ni. The valence state of the ions in the nanopowders and their morphology and structure have been studied by scanning electron microscopy, X-ray diffraction, IR spectroscopy, and X-ray photoelectron spectroscopy. The M x Ti0.91V0.09O2 + δ · nH2O oxides dried in air or calcined at 400°C in air are shown to be paramagnets. Vacuum annealing of Co0.08Ti0.91V0.09O2 + δ · nH2O at 700°C gives rise to a significant ferromagnetic contribution.
Evaluation and modification of the initial composition of gabbro-basalt rocks for mineral-fiber fabrication and stone casting by S. V. Fomichev; I. Z. Babievskaya; N. P. Dergacheva; O. A. Noskova; V. A. Krenev (1121-1125).
Literature data and calculation results demonstrate that it is appropriate to use the acidity coefficient for the initial evaluation of the properties of gabbro-basalt raw materials for fiber production and stone casting. We examine the capabilities of hydrochloric acid leaching for modifying the composition of raw materials and those of physicochemical calculations for determining the mineralogical compositions of raw materials and modification products.
Mechanochemical synthesis of BaTiO3 using different forms of TiO2 by V. V. Sydorchuk; V. A. Zazhigalov; S. V. Khalameida; K. Wieczorek-Ciurowa (1126-1130).
Reactions between barium oxide and different forms of titanium dioxide during milling in air and subsequent heat treatment have been studied by X-ray diffraction, Raman spectroscopy, and differential scanning calorimetry. The results indicate that, when the low-temperature forms of TiO2 are used, milling produces weakly aggregated barium titanate powders with a large specific surface area.
Physicochemical properties of La3Ga5.5Ta0.5O14 by I. A. Kaurova; G. M. Kuz’micheva; A. B. Dubovskii (1131-1136).
We report the optical and dielectric properties and microhardness of La3Ga5.5Ta0.5O14 lanthanum gallium tantalate (langatate) crystals. Analysis of the optical transmission spectra of the crystals in relation to their refined compositions indicates that the bands at 34000–35000 and 27000–28000 cm−1 are due to lanthanum and oxygen vacancies, respectively, and that the band at 20000–21000 cm−1 is responsible for the yellow (orange) coloration of the crystals. Their resistivity and microhardness decrease with increasing oxygen vacancy concentration.
Preparation of SrFe12O19 · 6SrB2O4 magnetic composites by spray pyrolysis by O. V. Usovich; L. A. Trusov; P. E. Kazin; Yu. D. Tret’yakov (1137-1142).
Spray pyrolysis has been used to produce X-ray amorphous precursors with the nominal composition SrFe12O19 · 6SrB2O4 in the form of spherical particles 0.3 to 2 μm in diameter. Heat treatment of the precursors at temperatures from 650 to 900°C has produced platelike strontium hexaferrite particles embedded in a SrB2O4 matrix. With increasing annealing temperature, the average dimensions of the hexaferrite particles increase from 80 × 20 to 450 × 100 nm and the coercivity of the material rises from 240 to 440 kA/m.
Specific heat and enthalpy of lattice disordering of LaF3 superionic crystals by V. F. Krivorotov; P. K. Khabibullaev; A. A. Fridman; E. V. Charnaya; Kh. T. Sharipov (1143-1146).
Specific heat (C p ) data obtained near the phase transition of LaF3 are used to estimate the activation enthalpy for anion disordering, H d. At the critical point T c = 263 K, the concentration of disordered fluoride ions is n c = 2.86 × 1020 g−1. In the dielectric phase of LaF3 (T < T c), H d is 0.24–0.26 eV. In the superionic phase (T ≥ T c), where the concentration of disordered fluoride ions exceeds n c, the enthalpy of disordering drops to H d ≃ 0.04 eV.
Determination of impurities in germanium tetrafluoride by IR spectroscopy and gas chromatography by P. G. Sennikov; A. D. Bulanov; V. A. Krylov; T. G. Sorochkina (1147-1150).
Using high-resolution Fourier-transform IR spectroscopy and gas chromatography, we have identified more than 20 impurity species, in concentrations from 10−1 to 10−5 vol %, in GeF4 samples of different isotopic compositions. The germanium tetrafluoride samples are shown to contain C1–C4 hydrocarbons; hydrogen, carbon, silicon, and sulfur fluorides; fluorogermanes; fluorosilanes; and carbon and nitrogen oxides.
Properties of fluorosilicate glass prepared by MCVD by V. A. Aksenov; G. A. Ivanov; L. D. Iskhakova; M. E. Likhachev; S. G. Chernook; O. E. Shushpanov (1151-1154).
Multilayer and two-layer fiber preforms with a fluorosilicate glass core have been produced by the modified chemical vapor deposition (MCVD) process with SiF4 as a fluorination agent. The fluorine profile across the preforms has been studied, the fluorine concentration in the glass has been determined as a function of the initial vapor mixture composition, and the effect of the fluorine concentration on the refractive-index difference between the fluorosilicate and silica glasses and on the mechanical stress in the glass has been examined. Comparison of the present results with literature data demonstrates that the above parameters depend significantly on the fluorosilicate glass preparation process: MCVD or plasma chemical vapor deposition (PCVD). This is tentatively attributed to the difference in structure between the glasses made by MCVD and PCVD.
Effect of mechanical processing of ultrafine ZrO2 + 3 wt % MgO powder on the microstructure of ceramics produced from it by S. P. Buyakova; S. N. Kul’kov (1155-1158).
This paper examines the effect of milling on the morphology and properties of ultrafine ZrO2 + 3 wt % MgO powder and on the microstructure and strength of the ceramics produced from it. Low-energy milling enables a marked decrease in the degree of aggregation of the powder, which in turn reduces the grain size and increases the density and strength of the ceramics.
Erratum: “Anion Disorder in LnF3 (Ln = La, Ce, Pr) Crystals” by V. F. Krivorotov; P. K. Khabibullaev; Kh. T. Sharipov (1159-1159).