Studies of Combustion Mechanochemical Reactions in Off-Stoichiometric Powder Mixtures of Fe1 − x S1 + x

The reaction between iron and sulfur powders induced by high-energy ball milling was studied as a function of milling time and the composition of starting powders Fe(1 – x) + S(1 + x), where x = –0.03, 0, 0.03, 0.05, 0.10. The reaction products were studied by using the Mössbauer spectra and X-ray diffraction analysis. The analyzed process is self-sustaining and runs for a period of time of 2–5 hours of milling. The iron powder used in this case was characterized by a particle size of 1600 mesh. The Mössbauer spectra obtained at room temperature after 2 hours of milling revealed partial sulfiding missed in the course of X-ray diffraction analysis. In all other samples, we observed a sextet (for an internal magnetic field of 21 MA/m) and a doublet (with insignificant deviations from the corresponding parameters for FeS₂). This confirms the results of X-ray phase diffraction analysis according to which FeS is the sole significant phase.     

Preparation of nanocrystalline VO<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> by high-energy ball milling

We report high-energy milling of macrocrystalline nonstoichiometric cubic vanadium monoxide (VO _y ) powder in a planetary ball mill lined with stabilized zirconia. The results indicate that milling of macrocrystalline VO _y powder at 500 rpm for more than 2 h considerably broadens diffraction line profiles, with no changes in the crystal structure of the vanadium monoxide, VO_1.00. Microstructural examination of vanadium monoxide powder by high-resolution scanning electron microscopy and X-ray diffraction indicates that high-energy ball milling can be used to produce vanadium monoxide powder with an average crystallite size within 23 nm.     

Synthesis of Mg<Subscript>2</Subscript>Ni nanoparticles in a KCl-NaCl-MgCl<Subscript>2</Subscript> melt

The reaction between magnesium and nickel powders in a KCl-NaCl-MgCl₂ ionic melt at 970 K (reaction time, 5 h) has been studied by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, and chemical analysis. According to scanning electron microscopy data, the synthesized Mg₂Ni powder consists of particles 70–75 nm in size, in reasonable agreement with the equivalent particle diameter, ≃ 64 nm, determined from the specific surface area of the Mg₂Ni powder and with the crystallite size, D _hkl ≃ 65 nm, evaluated from X-ray diffraction data. The hydrogen sorption properties of the Mg₂Ni obtained in a KCl-NaCl-MgCl₂ ionic melt are identical to those of Mg₂Ni powder prepared by a standard method, but the former reacts with hydrogen far more rapidly.     

Spectroscopic and thermal behavior of ZnHg(SCN)4

The synthesis and purification of zinc mercury thiocyanate, ZnHg(SCN)₄ (ZMTC), are described. The identity of the synthesized compound was characterized by elemental analysis, X-ray powder diffraction, infrared, Raman, and UV/Vis/NIR transmission spectra. The thermal stability and thermal decomposition of ZMTC crystal were investigated by means of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurements. The intermediates and final products of the thermal decomposition were identified by X-ray powder diffraction (XRPD).     

Effects of boron-doping on the morphology and magnetic property of carbon nanotubes

Boron carbide nanotubes (nano-fibers) was prepared by B powder and carbon nanotubes (CNTs) at high temperature in a vacuumed quartz tube. The morphology, microstructure, component and magnetic property of samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and magnetic property measurement system (MPMS) controller. The results showed that B-doping CNTs have great difference in the morphology and magnetic property from those of pristine CNTs. __________ Translated from Journal of Functional Materials, 2006, 37(9): 1398–1400 (in Chinese)     

Crystallization mechanism in amorphous material of 0.5LiMnO2-0.5B2O3

0.5LiMnO₂-0.5B₂O₃ glass has been prepared by quenching a melt of LiNO₃, MnO₂ and B₂O₃ at 1100°C to room temperature in air. The crystallization mechanism of this kind of glass was investigated by differential thermal analysis (DTA) and powder X-ray diffraction (XRD). It is shown that the substances crystallized from powder and bulk samples are different because manganese with lower valence in powder sample can be further oxidized by the oxygen penetrated through the large surface of powder sample. For a powder sample the glass transition endothermic peak in the DTA curve is overlapped by an exothermic reaction attributed to the oxidization of Manganese. LiMn₂O₄ can not be crystallized directly from the glass matrix but can be formed on the surface of glass particles by effect of oxygen in air near the glass transition temperature.     

Contribution study of properties of copper indium diselenide thin films

Stoichiometric powder of CuInSe₂ (CIS) was prepared from molten stoichiometric quantities of the elements. The structure analyzed by X-ray diffraction powder (XRD), shows mainly the chalcopyrite phase. CIS polycrystalline thin films deposited from this powder have been grown on glass substrates in vacuum by thermal evaporation method. The structural and electrical properties of both as-deposited and annealed films were studied using X-ray diffraction and dark conductivity measurements respectively. As-prepared films at room temperature showed an amorphous structure. However, the chalcopyrite structure with (112) preferential orientation was observed after annealing in vacuum at 400 °C during 30 min. The influence of the annealing process on the dark conductivity of the films was also discussed.     

Studies on growth and characterization of an NLO crystal: L-alanine hydrogen chloride (LAHC)

A nonlinear optical (NLO) salt viz. L-alanine hydrogen chloride (LAHC) has been synthesized and solubility of the synthesized salt in de-ionized water was determined at different temperatures. Single crystals of L-alanine hydrogen chloride (LAHC) salt were grown by solution method with slow evaporation technique. The grown crystals were characterized by single crystal X-ray diffraction (XRD) and powder XRD analyses to study the crystal structure. The crystallinity of LAHC crystal was confirmed by the powder X-ray diffraction study and diffraction peaks were indexed. FTIR study was used to confirm the presence of various functional groups in the grown crystals. UV–visible transmittance spectrum was recorded to study the optical transparency of LAHC crystal. The nonlinear optical (NLO) property of the grown crystal was confirmed by Kurtz–Perry powder test. The density of LAHC crystal was determined by floatation method. The mechanical strength of the crystal was estimated by Vickers hardness test. The grown crystals were subjected to TG/DTA analyses. The dielectric behavior of the sample was also studied.     

The effect of multi-walled carbon nanotubes/hydroxyapatite nanocomposites on biocompatibility

In the present study, multi-walled carbon nanotubes/hydroxyapatite (MWCNTs/HA) nanocomposites with various MWCNT contents were manufactured by sol-gel processing. The MWCNTs/HA powder was characterized using field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman analysis. The results show that the MWCNTs were fully covered with HA nanoparticles and help forming the crystallized hydroxyapatite. In addition, in vitro tests highlighted the excellent biocompatibility of the MWCNTs/HA composite.     

Hydrothermal treatment of effluent affected polluted soil of Nanjangud, Mysore district, India

The polluted soils from the major textile, distillery and food industries located on a high-grade rock terrain (Nanjangud, Mysore district, India) were treated under hydrothermal conditions using water as a solvent. The electrical conductivity and N, P, K content have been studied before and after the hydrothermal treatment for these soil samples. Characterization of these soil samples was carried out through powder X-ray diffraction, thin section and infrared spectroscopic studies.     

Synthesis of Nano Crystalline Ni and Fe by Levitational Gas Condensation Method

Nanocrystalline Ni and Fe were synthesized by the levitaional gas condensation (LGC) method using wire feeding (WF) and micron powder feeding (MPF) systems. The magnetic properties have been characterized using a vibrating sample magnetometer (VSM) and Moumlssbauer spectroscopy. The X-ray diffraction and saturation magnetization results indicate the small amount of oxidized phases such as amorphous NiO and Fe₃O₄ on the surface of metal powders. The size and shape of the nano powders were investigated by transmission microscopy (TEM). It was found that particles have a mean crystallite size about 22 and 24 nm for Fe and Ni. The surface effect might influence the magnetic hysterisis behavior of Ni and Fe     

醇-水热法制备钇铝石榴石(YAG)纳米粉体

首先采用共沉淀法制备钇铝石榴石前驱体,然后以乙醇-水混合溶剂作为反应介质,在较低的温度(300℃)和压力(10MPa)下,制备分散性好的钇铝石榴石纳米粉体.并借助XRD,TEM,BET与IR等测试手段,对所制备样品的性能进行了表征.实验结果表明,在适当的醇-水比条件下可在较低的温度和压力下制备纯相的YAG纳米粉体,其粒度大约为20nm,分散性良好.并对YAG的醇-水热形成机理进行了初步探讨.     

Chemical vapor deposition of tungsten oxides: A comparative study by X-ray photoelectron spectroscopy,X-ray diffraction and reflection high energy electron diffraction

Thin films of tungsten compounds have been deposited by pyrolysis of W(CO)₆ on aluminium plates held at 400°C in oxygen or a neutral environment. Such films have been analysed by X-ray photoelectron spectroscopy X-ray diffraction and reflection high energy electron diffraction. Different compounds have been revealed ranging from metalliic tungsten to fully oxidized tungsten. The X-ray photoelectron spectroscopy study of the W_4f doublet has enabled the determination of various oxidation states of tungsten. A rather good agreement is found with the X-ray diffraction and reflection high energy electron diffraction measurements.     

Crystal structure and electrical properties of CaNaBi<Subscript>2</Subscript>Nb<Subscript>3</Subscript>O<Subscript>12</Subscript> ceramics

Monophasic CaNaBi₂Nb₃O₁₂ powders were synthesized via the conventional solid-state reaction route. Rietveld refinement of the X-ray powder diffraction (XRD) data and selected area electron diffraction (SAED) studies confirmed the phase to be a three-layer Aurivillius oxide associated with an orthorhombic B2cb space group. The dielectric properties of the ceramics have been studied in the 300–800 K temperature range at various frequencies (1 kHz to 1 MHz). A dielectric anomaly was observed at 676 K for all the frequencies corresponding to the ferroelectric to paraelectric phase transition as it was also corroborated by the high temperature X-ray diffraction studies. The incidence of the polarization–electric field (P vs. E) hysteresis loop demonstrated CaNaBi₂Nb₃O₁₂ to be ferroelectric.     

Synthesis and analysis of PbO-modified Bi-Sr-Ca-Cu-O superconductors

High T _c superconducting materials based on a PbO-modified Bi-Sr-Ca-Cu-O system with various ratios between the oxides were prepared by calcination at 800 °C and firing at 855 °C. From X-ray powder diffraction analysis data, the ratio of low- and high-temperature phases was calculated. The material with the nominal composition Bi₂Pb_0.5Sr₂Ca_2.5Cu_3.5O _x was chosen for further experimental work. Samples fired at 800 °C contain mostly the low-temperature phase (2212). Higher firing temperatures lead to the formation of the high T _c phase (2223) with T _c(R=0) over 100 K. Some samples were cold pressed and refired which increased the specific density to over 80% of the theoretical density. The composition of samples was investigated by X-ray powder diffraction analysis and by energy dispersive X-ray spectroscopy. The main phase in the material fired at 800 °C, is the low T _c phase 2212, and secondary phases are Ca₂PbO₄, unreacted CuO and traces of 2223 phase. At higher firing temperatures, the main phase is the high-temperature phase 2223. The material is still heterogeneous and contains Ca₂PbO₄.     

Quantification of compaction-induced crystallinity reduction of a pharmaceutical solid using 19F solid-state NMR and powder X-ray diffraction

¹⁹F solid-state nuclear magnetic resonance (NMR) was investigated as an analytical technique to quantify the amorphous phase in a fluorine-containing pharmaceutical candidate. The crystallinity of Compound 1 was calculated using two ¹⁹F T₁ relaxation-based methods. The first method employs both the pure amorphous and the crystalline reference standards while the second method is model independent and utilizes a single standard. The ¹⁹F solid-state NMR results were confirmed with powder X-ray diffraction methods. From X-ray diffraction data, two linear calibration curves were obtained from blends of crystalline and amorphous Compound 1: one is based on the total integrated intensity of selected diffraction peaks and the other on the total intensity of the amorphous halo at 2θ positions that have no interference from crystalline diffraction peaks. The crystallinity of Compound 1 after compaction calculated by both ¹⁹F solid-state NMR methods was in excellent agreement with the results from the X-ray calibration curves. ¹⁹F solid-state NMR was shown to be a powerful technique in determining the amount of amorphous phase present in a pharmaceutical solid.     

Hydration behaviour of synthetic saponite at variable relative humidity

Hydration behaviour of synthetic saponite was examined by X-ray powder diffraction simulation at various relative humidities (RH). The basal spacing of the Ca-saponite increased stepwise with increase in RH. The (00l) reflections observed reflect single or dual hydration states of smectite. Quasi-rational, intermediate, or asymmetrical reflections were observed for all XRD patterns and reflecting heterogeneity of the samples, especially along the transition between two hydration states.     

Antibacterial activity of ZnO powder with crystallographic orientation

ZnO powder with crystallographic orientation was prepared from the mixed aqueous solution of zinc chloride, tri-ethanol amine and thio-urea. From X-ray diffraction measurement, as-prepared powder was found to have the orientation along a–b axes of hexagonal structure, and a needle-like shape with the aspect ratio of 5 was observed by scanning electron microscope, indicating that as-prepared powder had crystallographic orientation. In the tests of antibacterial activity by colony count method, ZnO powders with and without crystallographic orientation were used in present work. Survival ratio of bacteria decreased with increasing powder concentration, i.e., increase in antibacterial activity. The antibacterial activity in ZnO powder with crystallographic orientation was weaker than that in commercial ZnO powder without orientation at same powder concentration. Regarding specific surface area of the powders used in antibacterial tests, however, antibacterial activity in powder with orientation was found to be similar to that without orientation; that is, the crystallographic orientation of ZnO did not affect antibacterial activity. The activity toward Staphylococcus aureus was stronger than that toward Escherichia coli, irrespective of the kind of powders.     

Synthesis and characterization of polycrystalline sintered compacts of cubic boron nitride

Synthetic cubic boron nitride (CBN) compacts are an important tool material used extensively for the machining of hardened steels. The paper describes work on the synthesis and characterization of CBN compacts. A 200 tonne cubic press has been used for the generation of high pressures. Solid solutions of TiN and TiC have been used as the binder material. The CBN powder and the binder are homogenously mixed and the mixed powder is pressed in a steel die under a pressure of about 3 kbars (300 M Pa). The pellets so formed are the starting material for synthesizing the compacts. Compacts both with and without a tungsten carbide substrate have been synthesized. The best compacts are formed at 58kbar (5.8 G Pa) and 1450° C. The sintered compacts after grinding and polishing are characterized by using powder X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray analysis. Knoop hardness measurements made on the best CBN compacts give a hardness of 3400HK _0.5.     

Synthesis,growth, optical,mechanical and electrical properties of <Emphasis Type="Italic">L</Emphasis>-lysine <Emphasis Type="Italic">L</Emphasis>-lysinium dichloride nitrate (<Emphasis Type="Italic">L</Emphasis>-LLDN) single crystal

Semi-organic nonlinear optical material, L-lysine L-lysinium dichloride nitrate (2C₆H₁₅N₂O₂⁺_{2}^{+} · H⁺ · NO₃^-_{3}^{-} · 2Cl⁻) was synthesized at room temperature. Single crystals of L-LLDN were grown by slow cooling solution growth technique. The grown crystal was confirmed by powder X-ray diffraction analysis. The crystalline perfection of the grown single crystal was characterized by high-resolution X-ray diffraction (HRXRD) studies. The cut-off wavelength was determined by UV-vis transmission spectral analysis. The frequency doubling of the grown crystal was confirmed by powder second harmonic generation (SHG) measurement. The refractive index and birefringence of the crystal were determined using He–Ne laser source. Mechanical property of the crystal was determined by Vickers hardness tester. The frequency and temperature dependence of dielectric constant (ε _r), dielectric loss (tan δ) and a.c. conductivity (σ _ac) were also measured.