In<Subscript>0.22</Subscript>SnS<Subscript>0.33</Subscript>(OH)<Subscript>4</Subscript> nanolayers synthesized by the layer-by-layer technique

The possibility of the synthesis of In_0.22SnS_0.33(OH)₄ nanolayers on the silica surface by the layer-by-layer technique was demonstrated. The synthesized layers were studied by ellipsometry, X-ray spectral microanalysis, and electronic and IR Fourier spectroscopy.     

Synthese de F-alkyl oxirannes

The perfluoroalkyloxirans were obtained with good yields from the long chain perfluoroalkyl ethylenes R_FCHCH₂. All the reaction intermediates were isolated and described. Their structure was determinated by the usual spectroscopy methods : N.M.R., infra-red, mass spectrometry and by microanalysis.     

Electron Probe Microanalysis of HfO2 Thin Films on Conductive and Insulating Substrates

Quantitative electron probe microanalysis of highly insulating materials is a complicated problem, partially solved by coating samples with grounded thin conductive layers or using novel scanning electron microscopy (SEM) techniques, such as low-voltage and/or variable pressure SEM. In this work, some problems of quantitative X-ray microanalysis of thin HfO₂ films, in particular the possibility to determine mass thickness correlated to the density of the layer material, are discussed. For comparison, Al₂O₃, Ta₂O₅ and TiO₂ films grown onto both semiconductive Si and insulating quartz substrates were also analysed. All the films studied were synthesized by atomic layer deposition method.     

An EPMA Study on KNbO3 and NaNbO3 Single Crystals – Potential Reference Materials for Quantitative Microanalysis

Single crystals of KNbO₃ and NaNbO₃ were selected from the limited number of suitable alkali compounds that are available and evaluated as possible reference materials for the electron-probe microanalysis (EPMA) of alkaline niobates with a composition described by the general formula K_1–XNa_XNbO₃. The EPMA study verified that KNbO₃ and NaNbO₃ single crystals are stable under the electron beam and compositionally homogeneous. A quantitative microanalysis confirmed the composition of pure KNbO₃, while the NaNbO₃ crystal contained 0.3 mass fraction % of Ca. A significant improvement in the accuracy of the quantitative EPMA of polycrystalline potassium–sodium niobates was achieved using these single crystals as standards. The crystals can also be useful as reference materials for the analysis of sodium and potassium in other materials.     

Phase relationships in the SiO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript> system

Phase equilibria in a miscibility gap of the SiO₂-TiO₂ system were studied. A visual polythermal analysis and annealing of samples were performed in a Galakhov microfurnace. The microstructure and composition of the obtained samples were investigated by scanning electron microscopy and electron probe microanalysis. A critical analysis of the experimental data was made. Thermodynamically optimized based on the sub-regular solution model, a phase diagram of the SiO₂-TiO₂ system was constructed.     

Ag<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>-SnO<Subscript>2</Subscript> nanocomposite layers synthesized by ionic layer deposition onto silica surface

Possibility of performing synthesis of Ag _x -SnO₂ nanocomposite layers on the silica surface by ionic layer deposition was analyzed, and the factors affecting the layer morphology and composition were determined. The synthesized layers were examined by visible transmission spectroscopy, as well as by scanning electron microscopy, IR Fourier-transform spectroscopy, and X-ray spectral microanalysis.     

Preparation and X-ray diffraction study of phosphate sulfates M<Subscript>2</Subscript>MgTi(SO<Subscript>4</Subscript>)(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>

Phosphate sulfates M₂MgTi(SO₄)(PO₄)₂ (M = alkali metal) prepared by the sol–gel technique with ethanol as salting-out agent were characterized by differential thermal analysis, electron probe microanalysis, and X-ray phase analysis. The crystal structure of the compounds synthesized (M = Na, K) was refined by powder X-ray diffraction. The phase stability of the phosphate sulfates under heating was examined.     

非水体系中苯并三唑在铜电极上吸附的电化学表面增强拉曼光谱研究

采用电化学现场表面增强拉曼光谱(SERS)研究了非水体系中苯并三唑(BTAH)在铜电极上的吸附及成膜行为, 结果表明非水体系中BTAH的吸附行为随电位变化而不同. 较负电位区间主要以中性分子形式吸附; 中间电位区间主要以BTA^－吸附并不可逆成膜; 而在氧化电位区间主要表现为铜的氧化. 随中性配体三苯基膦(pph₃)的加入, 在中间电位区间, 由于易溶的Cu(pph₃)_n⁺的生成而使铜的溶解速度加快, 最终该阳离子在溶液中和BTA^-作用而生成了多核铜的配合物. 采用直接电化学方法模拟电极表面过程合成了相应的吸附产物, 并对其组成进行了相关表征.     

Layer-by-layer synthesis and study of nanostructured Pb<Subscript>4</Subscript>SbS<Subscript>6.5</Subscript> layers

Conditions for the layer-by-layer synthesis of nanostructured Pb₄SbS_6.5 layers on a silica surface, using reagent solutions, were determined. The synthesized layers were studied by X-ray photoelectron spectroscopy, UV and visible transmission spectroscopy, X-ray spectral microanalysis, and scanning electron microscopy.     

X-Ray and Electron Microscopy Studies of Rare-Earth Tungsten Bronzes

Rare-earth tungsten bronzes, RE_xWO₃, of perovskite tungsten-bronze (PTB) type, formed by conventional solid-state synthesis, have been studied by X-ray powder diffraction, electron diffraction in combination with microanalysis, and high-resolution transmission electron microscopy (HRTEM). The X-ray patterns indicated cubic PTB type structure with a≈3.83 Å (subcell), while the electron microscopy study indicated a lowering of the subcell symmetry and a complex superstructure. The upper phase composition limit, x≤0.25, for the RE_xWO₃ bronzes with PTB-related structures was established from the microanalysis study. Ordered, disordered and microtwinned superstructures were revealed by electron diffraction patterns and HRTEM images taken along 〈110〉_p. The superstructure is due to filling of the interstices in the WO₃ structure with the rare-earth ions. A hypothetical model of the superstructure based on the contrast features in the HRTEM images has been deduced. The relationships between the RE_xWO₃ bronzes formed by solid-state synthesis under high- and ambient-pressure conditions are presented.     

Synthesis,structure, and properties of substituted bismuth niobates Bi<Subscript>3</Subscript>Nb<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>Er<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>7–δ</Subscript>

Results are reported of a study of the structural and electrical characteristics of substituted bismuth niobates with composition Bi₃Nb_1–x Er _x O_7–δ, which are promising oxygen-ion conductors. The homogeneity regions of solid solutions were determined by X-ray phase analysis and electron microscopy with X-ray fluorescence microanalysis, and their crystal-chemical parameters were calculated. The electrical conductivity of sintered samples was examined by impedance spectroscopy.     

Synthesis of Bi-O- and Bi-V-O-containing Nanolayers by Ionic Deposition

A possibility of preparing Bi₂O₃ and BiVO₄ nanolayers by ionic deposition on the silica surface was shown for the first time. The influence of the concentration and pH of reactant solutions and of the number of ionic deposition cycles on the kinetics of the nanolayer growth was studied. The conditions were determined for the formation of a nanolayer by a reaction in a layer of ions sorbed on the surface. The thickness of the synthesized layers was determined by ellipsometry. The layer compositions were studied by X-ray spectral microanalysis, X-ray photoelectron spectroscopy, and UV and IR Fourier transform spectroscopy. The structure of the layers was studied by powder X-ray diffraction.     

The calculation of the thermodynamic equilibrium in Fe3+/MoO 4 2− /H+(OH−)/H2O system and determination of reasonable conditions for iron molybdate deposition

The thermodynamic data on the Fe³⁺/MoO₄ ^2?/H⁺(OH^?)/H₂O system were analyzed. The iron(III) molybdate precipitates were studied by the X-ray phase analysis and electron probe microanalysis. It was shown that the content of the iron(III) oxide impurity in the precipitates depends on method and conditions of mixing of an iron precursor solution and an molybdenum precursor solution.     

Synthesis and Characterization of the Titanium Containing Mesoporous Molecular Sieve MCM-48

Ti-MCM-48 mesoporous materials have been synthesized by sequential addition of alkoxides. The atomic ratio of Si and Ti in the synthesis gel was 40 and 5, respectively. The materials were characterized by means of powder XRD, N₂ adsorption-desorption measurements. HREM, ²⁹Si MAS NMR, diffuse reflectance FT-IR spectroscopy, electrophoretic mobility measurements and electron probe microanalysis.     

Synthesis and Characterization of the Titanium Containing Mesoporous Molecular Sieve MCM-48

Ti-MCM-48 mesoporous materials have been synthesized by sequential addition of alkoxides. The atomic ratio of Si and Ti in the synthesis gel was 40 and 5, respectively. The materials were characterized by means of powder XRD, N₂ adsorption-desorption measurements, HREM, ²⁹Si MAS NMR, diffuse reflectance FT-IR spectroscopy, electrophoretic mobility measurements and electron probe microanalysis.     

Thermal analysis of two Fe-X-B (X=Nb,ZrNi) alloys prepared by mechanical alloying

The alloys, Fe₆₀Ni₁₄Zr₆B₂₀ and Fe₈₅Nb₉B₆, were produced by mechanical alloying. The formation of the nanocrystallites (about 40 nm) was detected by X-ray diffraction. Furthermore, a slight oxygen presence (<3 at.%) was found by induced-coupled plasma and EDX microanalysis. After milling, calorimetry scans show low temperature recovery process and several crystallization processes related with the crystal growth and reordering of the crystalline phases. The apparent activation energies, 360 and 290 kJ mol^-1, were determined by the Kissinger method. A mass increase (about 1 mass%) was detected by thermogravimetry. This revised version was published online in July 2006 with corrections to the Cover Date.     

Investigation of the phase diagram and the determination of synthesis conditions of volume amorphous alloys in the Cu-Ni-Zr system at 1123 K

The phase equilibria in the Cu-Ni-Zr system in a field enriched by zirconium at 1123 K were investigated by the methods of X-ray and electron-probe microanalysis, microdurometry, and scanning calorimetry. A fragment of the isothermal section of the given system was constructed and the borders of areas of homogeneity of double phases of the Ni-Zr and Cu-Zr systems were defined. It was established that the double compounds NiZr and NiZr₂ dissolve up to 33 and 12 at % Cu, respectively, and CuZr and CuZr₂, dissolve up to 7 at % Ni.     

Growth and properties of MnIn<Subscript>2</Subscript>S<Subscript>4</Subscript> single crystals

Homogeneous MnIn₂S₄ single crystals ∼14 mm in diameter and ∼40 mm long were grown by directional solidification of melt. For these MnIn₂S₄ single crystals, the composition was determined by electron probe microanalysis, structure by X-ray diffraction, and melting temperature by differential thermal analysis. Transmission spectra were studied in these single crystals, in the region of the intrinsic absorption edge within 10–300 K. The transmission spectra were used to determine the bandgap width, and it was plotted as a function of temperature. The thermal expansion of MnIn₂S₄ single crystals was studied dilatometrically in the range 80–700 K, and the thermal expansion coefficient was determined.     

Layers of nanocomposite FeOOH-xH3PW12O40 synthesized by ion-colloid layering

For the fi rst time the conditions of synthesis by ion-colloid layering of layers of nanocomposite FeOOH—xH₃PW₁₂O₄₀ on the surface of silica were defined using successively adagulation of FeOOH colloidal particles, and adsorption of H₃PW₁₂O₄₀. Investigation of the synthesized layers was carried out by scanning electron microscopy, X-ray microanalysis, UV and Fourier transmitting infrared spectroscopy.     

Effect of Bimetallic Pd/Pt Clusters on the Sensing Properties of Nanocrystalline SnO<Subscript>2</Subscript> in the Detection of CO

Nanocrystalline tin dioxide modified by Pd and Pt clusters or by bimetallic PdPt nanoparticles was synthesized. Distribution of the modifers on the SnO₂ surface was studied by high-resolution transmission electron microscopy and energy dispersive X-ray microanalysis with element distribution mapping. It was shown that the Pd/Pt ratio in bimetallic particles varies over a broad range and does not depend on the particle diameter. The effect of platinum metals on the reducibility of nanocrystalline SnO₂ by hydrogen was determined. The sensing properties of the resulting materials towards 6.7 ppm CO in air were estimated in situ by electrical conductivity measurements. The sensor response of SnO₂ modified with bimetallic PdPt particles was a superposition of the signals of samples with Pt and Pd clusters.