Scanning Electron Acoustic Microscopy of GaInAsSb by Metalorganic Chemical Vapor Deposition

ＳｃａｎｎｉｎｇＥｌｅｃｔｒｏｎＡｃｏｕｓｔｉｃＭｉｃｒｏｓｃｏｐｙｏｆＧａＩｎＡｓＳｂｂｙＭｅｔａｌｏｒｇａｎｉｃＣｈｅｍｉｃａｌＶａｐｏｒＤｅｐｏｓｉｔｉｏｎＬｉＳｈｕｗｅｉ，ＪｉｎＹｉｘｉｎ，ＺｈｏｕＴｉａｎｍｉｎｇ，ＺｈａｎｇＢａｏｌｉｎ（李...     

Formation of Dy－Co Alloy and Preparation in Chloride Melt by Molten Salt Electrolysis

ＦｏｒｍａｔｉｏｎｏｆＤｙ－ＣｏＡｌｌｏｙａｎｄＰｒｅｐａｒａｔｉｏｎｉｎＣｈｌｏｒｉｄｅＭｅｌｔｂｙＭｏｌｔｅｎＳａｌｔＥｌｅｃｔｒｏｌｙｓｉｓＬｉｕＧｕａｎｋｕｎ，ＴｏｎｇＹｅｘｉａｎｇ，ＨｏｎｇＨｕｉｃｈａｎ，ＣｈｅｎＳｈｅｎｇｙａｎｇａｎｄＧ...     

Preparation of high-purity indium by electrorefining

The application of indium requires high purity indium as material, and the high purity indium has been prepared by electrorefining. The selection and preparation of electrolyte in electrorefining indium were investigated,and the effect of component of electrolytic solution on electrolytic refining was also studied. Compared with electro-lyte of InCl3-HCl, electrolyte of In2(SO4)3-H2 SO4 has higher stability and lower corrosivity, electrolytic solution can be heated at low temperature, and bath is open and simple, which makes operation more convenient. The results show that the voltage can be kept at 0. 3-0.5 V, and the content of indium can exceed 99. 999% when the contentof indium(Ⅲ) ion and sodium chloride are 80-120 g/L. The bench-scale test of electrolysis was carried out, and the product of indium reaches the national standard of 99. 999% high purity indium.     

Preparation of antimony-doped nanoparticles by hydrothermal method

Antimony-doped tin oxide (ATO) nanoparticles were prepared by the mild hydrothermal method at 200℃ using sodium stannate, antimony oxide, sodium hydroxide and sulfuric acid as the starting materials. The doped powders were examined by differential thermal analysis(DTA), X-ray diffractometry(XRD) and transmission electron microscopy(TEM). The doping levels of antimony were determined by volumetric method and iodimetry.The results show that antimony is incorporated into the crystal lattice of tin oxide and the doping levels of antimony in the resulting powders are 2.4%, 4.3%and 5.1%(molar fraction). The mean particle size of ATO nanoparticles is in the range of 25 - 30 nm. The effects of antimony doping level on the crystalline size and crystallinity were also discussed.     

Crystal Perfection in GaP Films Heteroepitaxially Grown on GaAs by Low-pressure Metalorganic Chemical Vapor Deposition

1ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｃｒｙｓｔａｌｐｅｒｆｅｃｔｉｏｎｆｏｒⅢⅤｇｒｏｕｐｓｅｍｉｃｏｎｄｕｃｔｏｒｍａｔｅｒｉａｌｓｈｅｔｅｒｏｅｐｉｔａｘｉａｌｌｙｇｒｏｗｎｂｙｍｅｔａｌｏｒｇａｎｉｃｃｈｅｍｉｃａｌｖａｐｏｒｄｅｐｏｓｉｔｉｏｎ(ＭＯＣＶＤ)ｗａｓｆｏｕｎｄｔｏｂｅａｓｅｎｓｉｔｉｖｅｆｕｎｃｔｉｏｎｏｆｇｒｏｗｔｈｆａｃｔｏｒｓ,ｉｎｃｌｕｄｉｎｇｐｒｅｃｕｒｓｏｒｓ,ｓｕｂｓｔｒａｔｅ,ｔｅｍｐｅｒａｔｕｒｅ,ｐｒｅｓｓｕｒｅ,ｆｌｏｗｒａｔｅａｎｄｒｅａｃｔｏｒｄｅｓｉｇｎｅｔ…     

Preparation of Rarc Earth Alloys by Cathodic Alloying

ＰｒｅｐａｒａｔｉｏｎｏｆＲａｒｃＥａｒｔｈＡｌｌｏｙｓｂｙＣａｔｈｏｄｉｃＡｌｌｏｙｉｎｇＹａｎｇＱｉｑｉｎ；ＬｉｕＧｕａｎｋｕｎ；ＱｉｕＫａｉｒｏｎｇ；ＨｏｎｇＨｕｉｃｈａｎ；（杨绮琴）（刘冠昆）（丘开容）（洪惠婵）ＴｏｎｇＹｅｘｉａｎｇａｎｄＳ...     

Preparation of open-cell metal foams by investment cast

1. Introduction Metal foams are a new kind of materials with low densities and novel physical, mechanical, thermal, electrical and acoustic properties. They are potential materials for lightweight structures, energy absorption, and thermal management applications. They can be divided into closed and open cell structures (sponges). For sponges, the typical applications of these open-cell materials so far are heat exchangers, filter elements, acoustic absorbers, stiffening elements, crash absorb…     

Preparation of chain copper oxide nanoparticles by microwave

Cu（OH）2 nano-fibers were prepared by chemical precipitation with CuSO4·5H2O and NaOH as raw materials. The Cu（OH）2 nano-fibers have a diameter of 10-30 nm and a length of 1-6 μm. The reaction conditions were as follows： the concentration of CuSO4 solution was 0.1 mol·L^-1,NaOH solution 4 mol·L^-1,the dropping rate of the NaOH solution 50 mL·min^-1,the reaction temperature 20℃the pH value of the reaction terminal 13,and the stirring rate 1200 r·min^-1. The chain nano-CuO grains were obtained through the microwave radiation of the Cu（OH）2 nano-fibers.     

Preparation of zirconium by electro-deoxidization in molten salt

Metal zirconium was prepared by electro-deoxidization method. Using CaCl2 molten salt as electrolyte, sintered ZrO2 pallets as cathode, graphite rod as anode, the pallets were electrolyzed at 900 ℃ and 3.1 V for 8, 10 and 12 h, respectively. The mechanism of electro-deoxidization of ZrO2 was studied preliminarily. The results show that the morphologies of cathode pallets affect the forming process of products. The process of electro-deoxidization ofZrO2 in the molten salt is conducted step by step, from exterior of cathode to its interior and from high valence oxide to low valence oxide until to metal.     

Preparation of single-phase ammonium dimolybdate by combination process

A novel method for the preparation of single-phase ammonium dimolybdate with industrial ammonium molybdate was studied.Various influential factors were evaluated in the paper,including reaction temperature,reaction time,initial molybdenum concentration,initial NH3/Mo molar ratio,and stirring speed.Under the optimum experimental conditions,the crystallization rate of product is 85.23％.The X-ray diffraction (XRD) analysis and chemical analysis show that the product is single-phase ammonium dimolybdate,and no impurity phases exist.The scanning electronic microscope (SEM) image reveals uniform particle size,good particle dispersion,and no agglomeration between particles.Meanwhile,the final pH value of acidification was investigated.The total molybdenum recovery can reach up to 99.40％,and the main phases of acidification product are the same as those of raw material with the final pH value of 1.5.This determines that the acidification product can be used as a raw material to produce single-phase ammonium dimolybdate.     

Modeling of gas phase diffusion transport during chemical vapor infiltration process

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｃｈｅｍｉｃａｌｖａｐｏｒｉｎｆｉｌｔｒａｔｉｏｎ (ＣＶＩ)ｍｅｔｈｏｄｉｓｏｎｅｏｆｔｈｅｍｏｓｔｐｒａｃｔｉｃａｌａｎｄ ｐｒｏｍｉｓｉｎｇ ｐｒｏｃｅｓｓｆｏｒｆａｂｒｉｃａｔｉｏｎｏｆｃｅｒａｍｉｃ/ｃａｒｂｏｎｍａｔ     

A Safe and Brief Way for Preparing Anhydrous LnCl_3 (Ln=Sc, Y, La to Lu)

@李瑛 @王林山 @王育红     

Preparation and characterization of biomorphic SiC hollow fibers from wood by chemical vapor infiltration

Biomorphic SiC hollow fibers were prepared by the reactive infiltration of SiO vapor into basswood-derived charcoal. Gaseous SiO was produced from a SiO₂/Si powder mixture in Ar at elevated temperatures. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and Fourier transform-infrared spectroscopy were employed to characterize the structural morphology and phase compositions of the final products. The results show that the tubular cells in bulk charcoal are converted into lots of SiC hollow fibers with pore diameters of 10–50 μm and lengths ranging from hundreds of μm to several mm. Resulting SiC hollow fibers consist of β-SiC with a minute amount of α-SiC. The formation mechanism of SiC hollow fibers is based on the gas–solid reaction between SiO and carbon.     

Boron nitride coatings by chemical vapor deposition from borazine

Boron nitride coatings were prepared from borazine as the single source precursor containing stoichiometric boron and nitrogen by hot-wall chemical vapor deposition (CVD) in a low deposition temperature range from 800 °C to 900 °C, with a total pressure of 1 kPa. The chemical and phase compositions, morphologies and structures of the coatings were investigated. The coatings deposited at 800 °C still contained some residual N-H, whereas the coatings prepared at 900 °C were comparatively pure BN. The surface of the as-deposited coatings exhibited a pebble-like and compact structure, and the cross-sectional morphology of the coatings showed a laminar structure. While the as-deposited coatings had a turbostratic structure as evidenced from the XRD and TEM examinations, the turbostratic BN crystallized into hexagonal BN by heat treatment at temperatures above 1400 °C. The as-deposited coatings had a preferential orientation near the coating/graphite substrate interface in which the (002) basal planes organized parallel to the surface of the substrate.     

Formation of mullite coatings on silicon-based ceramics by chemical vapor deposition

Dense, uniform, mullite coatings have been deposited by chemical vapor deposition on SiC substrates, using a AlCl₃-SiCl₄-CO₂-H₂ system. The typical coating microstructure consisted of a thin layer of nanocrystallites of γ-Al₂O₃ in vitreous silica at the coating-substrate interface, with columnar mullite grains over this interfacial layer. The composition of the coating was graded such that the outer surface of the coating was highly alumina rich. The changes in the coating microstructure with processing parameters are discussed. The ability of mullite to incorporate such large composition variations is discussed in the light of vacancy formation as theAl/Si ratio is increased and the ordering of these vacancies leads to changes in lattice parameters. The formation of domains was studied by measuring the spacing of superlattice spots in electron diffraction patterns and the relationship between domain size andAl/Si ratio is discussed.     

Formation of aluminide coatings on Fe-based alloys by chemical vapor deposition

Aluminide and Al-containing coatings were synthesized on commercial ferritic (P91) and austenitic (304L) alloys via a laboratory chemical vapor deposition (CVD) procedure for rigorous control over coating composition, purity and microstructure. The effect of the CVD aluminizing parameters such as temperature, Al activity, and post-aluminizing anneal on coating growth was investigated. Two procedures involving different Al activities were employed with and without including Cr–Al pellets in the CVD reactor to produce coatings with suitable thickness and composition for coating performance evaluation. The phase constitution of the as-synthesized coatings was assessed with the aid of a combination of X-ray diffraction, electron probe microanalysis, and existing phase diagrams. The mechanisms of formation of these CVD coatings on the Fe-based alloys are discussed, and compared with nickel aluminide coatings on Ni-base superalloys. In addition, Cr–Al pellets were replaced with Fe–Al metals in some aluminizing process runs and similar coatings were achieved.     

Phase equilibria and chemical vapor transport in the system Mo–Ta–As

The phase diagram Mo–Ta–As was studied in two partial isothermal sections at 1050 °C (in the As-rich corner) and at 1400 °C (As-poor alloys) using powder X-ray diffraction and electron probe microanalysis. A complete solid solution was found to exist between isostructural Mo₅As₄ and Ta₅As₄ and the ternary solubility of Mo in Ta₃As at 1400 °C was determined. A ternary phase Mo_xTa_1−xAs with MnP-type structure was found to exist in the As-rich part of the system. Lattice parameters were investigated as a function of composition for (Mo,Ta)₅As₄ and for Mo_xTa_1−xAs. Additional experiments of chemical vapor transport (CVT) from 1000 °C to 900 °C using different ternary source compositions and I₂ and Br₂ (PtBr₂) as transport agents were performed. Only Ta compounds were found in the sink and no ternary transport was observed.     

Comparative study of ZnO nanostructures grown on silicon (1 0 0) and oxidized porous silicon substrates with and without Au catalyst by chemical vapor transport and condensation

ZnO tetrapods and rods were grown on silicon and thermally oxidized porous silicon substrates with and without Au catalyst layer by carbothermal reduction of ZnO powder through chemical vapor transport and condensation method (CVTC). Porous silicon was fabricated by electrochemical etching of silicon in HF solution. The effect of substrates on morphology, structure and photoluminescence spectra of ZnO nanostructures has been studied. The texture coefficient (TC) of each sample was calculated from XRD data that demonstrated random orientation of ZnO nanostructures on the oxidized porous silicon substrate. Moreover, TC indicates the effect of Au catalyst layer on formation of more highly oriented ZnO nanorods. The morphology of the samples was investigated by SEM which confirms formation of ZnO nanostructures on oxidized porous silicon substrates with and without catalyst. A blue-green emission has been observed in ZnO nanostructures grown on Si and the oxidized PS substrates without Au catalyst layer by PL measurements.     

Preparation of nanocrystalline Lu2O3:Eu phosphor via a molten salts route

The paper reports on the course of decomposition of hydrated lutetium nitrate and lutetium chloride to Lu₂O₃ in the eutectic mixture of NaNO₂ and KNO₂. It was shown that a crystallographically pure phase of the cubic Lu₂O₃ is formed at temperature as low as 250 °C. IR spectra revealed that the recovered powder contains some OH-contamination, however. The powders are characterized by crystallites sizes in the range of 18–30 nm in average. Emission and excitation spectra of Eu-doped powders show characteristic features for Eu³⁺ ion in an oxide host, which indicates that the procedure is appropriate for making activated nanoparticulate oxide phosphors. Most profound emission appears around 611 nm and the luminescence from the powder made starting with Lu(NO₃)₃ was noticeably higher compared to the product obtained from LuCl₃. The excitation spectrum of Eu³⁺ emission at 611 nm contains a band related to the fundamental absorption of the lutetia host lattice, which indicates an existence of the host-to-activator energy transfer.     

Growth kinetics and oxidation behavior of WSi2 coating formed by chemical vapor deposition of Si on W substrate

The growth kinetics of WSi₂ coating formed by chemical vapor deposition (CVD) of Si on a W substrate at temperatures between 1000 and 1200 °C using SiCl₄–H₂ gas mixtures was investigated and its isothermal oxidation resistance in 80% Ar–20% O₂ atmosphere was evaluated at temperatures between 800 and 1300 °C. WSi₂ coating grew with a parabolic rate law after an initial incubation period, indicating the diffusion-controlled growth. The activation energy for growth of WSi₂ coating was about 42.5 kcal/mol. The isothermal oxidation rate of WSi₂ coating increased with increasing oxidation temperature but rapidly decreased at 1300 °C. The oxidation product of WSi₂ coating was composed of the WO₃ particles embedded in the amorphous SiO₂ matrix at below 1200 °C but consisted of only SiO₂ phase at 1300 °C. The fast oxidation behavior of WSi₂ coating at below 1200 °C was attributed to the formation of many cracks and pores, i.e. short-circuit diffusion path of oxygen, within the oxide scale, which resulted from the internal stress generated both by the large volume expansion caused by the oxidation reactions of WSi₂ and by the evaporation of WO₃ phase. The slow oxidation behavior of WSi₂ coating at 1300 °C was due to the exclusive formation of a slow-growing continuous SiO₂ scale by the rapid evaporation of WO₃ phase.