Preparation of α-Bi_2O_3 from bismuth powders through low-temperature oxidation

α-Bi2O3 powders were prepared from nanometer Bi powders through low-temperature oxidation at less than 873.15 K. XRD, SEM, TEM and HRTEM were used to characterize the structure and morphology of Bi powders and Bi2O3 particles. Kinetic studies on the bismuth oxidation at low-temperatures were carried out by TGA method. The results show that bismuth beads should be reunited and oxidized to become irregular Bi2O3 powders. The bismuth oxidation follows shrinking core model, and its controlling mechanism varies at different reaction time. Within 0-10 min, the kinetics is controlled by chemical reaction, after that it is controlled by O2 diffusion in the solid α-Bi2O3 layer. The apparent activation energy is determined as 55.19 kJ/mol in liquid-phase oxidation.

PREPARATION OF NANOMETER ZrO_2-8% Y_2O_3 POWDERS BY AZEOTROPIC DISTILLATION PROCESSING

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Self-Propagating High-Temperature Reductive Synthesis of TiB_2-Al_2O_3 Composite Powders

TiB2-Al2O3 composite powders were produced by self-propagating high-temperature synthesis（SHS） method with reductive process from B2O3-TiO2-AI system. X-ray diffraction（XRD） and scanning electron microscopy（SEM） analyses show the presence of TiB2 and Al2O3 only in the composite powders produced by SHS. The powders are uniform and free-agglomerate. Transmission electron microscopy （TEM） and high resolution electron microscopy （HREM） observation of microstructure of the composite powders indicate that the interfaces of the TiB2-Al2O3 bond well, without any interfacial reaction products. It is proposed that the good interfacial bonding of the composite powders can be resulted from the TiB2 particles crystallizing and growing on the Al2O3 particles surface with surface defects acting as nucleation centers.

STUDY ON PREPARATION OF YBa_2Cu_3O_(7-x) ULTRAFINE POWDERS BY SOL-GEL PROCESS

The ultrafine powders of YBa2Cu3O7-x with the size of 100nm were synthesized by Sol-Gel process using cit-rate as complex and ammonium hydroxide to adjust pH of solu-tion. The process of Sol formation and Gel polymerization of YBa2Cu3O7-x in the Sol-Gel synthetic reaction has bee studied. The particle size ,pruity, sintering activity and superconducting properties of YBa2Cu3O7-x prepared by Sol-Gel method are better than by solid state reaction.

Hot deformation and processing maps of Al_2O_3/Al composites fabricated by flake powder metallurgy

The deformation behaviors of Al2O3/Al composites were investigated by compressive tests conducted at temperature of 300-450 °C and strain rates of 0.001-1.0 s-1 with Gleeble-1500 D thermal simulator system. The results show that the flow stress increases with increasing strain rate and decreasing temperature. The hyperbolic sine constitutive equation can describe the flow stress behavior of Al2O3/Al composites, and the deformation activation energy and constitutive equations were calculated. The processing maps of Al2O3/Al-2 μm and Al2O3/Al-1 μm composites at strain of 0.6 were obtained and the optimum processing domains are in ranges of 300-330 °C, 0.007-0.03 s-1 and 335-360 °C, 0.015-0.06 s-1 for hot working, respectively. The instability zones of flow behavior can also be recognized by the maps.

Effect of anions on preparation of ultrafine α-Al_2O_3 powder

Ultrafine alumina power was obtained by calcining the precursor at 1 200 ℃ for 2 h, which was prepared by homogeneous precipitation method using aluminium salts and urea as raw materials. The effects of anions on the morphology, particle size, surface area and configuration of the precursors were studied. The results show that the reactions of urea with aluminium nitrate and aluminium chloride result in agglomerates gels with bad filtering performance, the morphology is fibrillar. Aluminium sulphate-urea reactions result in the direct formation of amorphous powders with good filtering performance, of which morphology are regular spherical particles with larger granularity and smaller surface area. The reaction of mutual compound of aluminium sulphate and aluminium nitrate with molar ratio of 40:60 with urea can produce precursor with good filtering performance, spherical morphology, and uniform granularity distribution in the particle size range of 2-3 μm.

In_2O_3 Ultrafine Powder Synthesis by Sol0Gel Method

The precursor of ultrafine In 2O 3 powder was prepared by the hydrolysis, peptization and gelation of InCl 3·4H 2O used as raw material. After calcination, ultrafine In 2O 3 powder was obtained. The particles were characterized by the methods of thermo gravimetric and differential thermal analysis (TG DTA), X ray diffractometry (XRD) and transmission electron microscopy (TEM), respectively.

Transition of Y_2BaCuO_5 Phase in Powder Melting Processed YBa_2Cu_3O_(7-x) Superconductors

The morphology and the formation of Y2BaCuO5 phase in powder melting processed YBa2Cu3O7-x superconductors were investigated. The experimental results show the heat treatment can not change the shape of Y2BaCuO5 particles in powder melting processed samples. The formation of round Y2BaCuO5 phase is due to relative content of each constitution of precursor powders in powder melting process. For powder melting process, the excessive liquid phase is eliminated, which restrains the preferred growth of Y2BaCuO5 particles.

Effect of La_2O_3 nanoparticles on properties of molybdenum powder

The properties of La 2O 3 doped molybdenum powder were studied. The La 2O 3 nanoparticles on the surface of molybdenum powder which is produced by the reduction of La(NO 3) 3 doped MoO 2 in hydrogen decrease the intensity of feature energy loss peak of molybdenum substrate; but increase that of peak of Mo?3d. The surface of molybdenum powder exposed to the atmosphere can be reduced because the surface is mainly covered with La 2O 3 nanoparticles. As a result, the capability of anti oxidation of molybdenum is improved.

Effects of Particle Size and Content of Silicon Powder on Strength and Microstructure of Coked Al_2O_3-ZrO_2-C Refractories

Effects of particle size （A：d50 = 336. 9 μm, B：d50 =123.5μm, C： d50=19.5 μm, D： dso=2.21μm） and content （1 wt% , 3 wt% , 5 wt% , 7 wt% ） of silicon powder on cold crushing strength （CCS） , pore size distribution and microstructure of Al2O3 - ZrO2 - C refractories coked at high temperature had been investigated by means of mercury porosimeter, SEM, EDS, tic. The results indicated that particle size and content of silicon powder affected the cold crushing strength of coked specimens. It increased with the addition of silicon powder and its finer particle size. However, it decreased greatly when using too fine silicon powder. The particle size and content of silicon powder also impacted the phase evolution and microstructure of coked specimens, much more β-SiC whiskers constituted network structure and well distributed in specimens with reduction of their slenderness ratios when finer silicon powder was added, corresponding to that, the specimens＇ pore size distribution range became narrower with smaller pore diameter, but β-SiC whiskers were distributed sparsely and the specific pore volume of small pores increased when much finer powder was added. It was worthly mentioned that some nitride could form in specimens with addition of appropriate particle size and content of silicon powder.

Effects of Rare Earth Doping on the Properties of γ-Fe_2O_3 Magnetic Powder

The effects of rare earth doping on the formation process of α-FeOOH crystallite and the properties of γ-Fe2O3 magnetic powder were investigated. The growth of needle α FeOOH crystallite was completed by the basic process. The experimental results show that the rare earth doping can increase the aspect axial ratio of needle α-FeOOH grains. its anti-sintering capability during the heat-treatment and the thermostability of γ-Fe2O3 magnetic properties. The magnetic properties of γ-Fe2O3 doping with rare earth are as follows: the coercivity Hc=36.3 kA/m (445 Oe), the ratio saturation magnetization σs=90.4μWbm/kg (72 emu/g), the ratio remanent magnetization σr=54 μWbm/kg (43 emu/g), and the temperature coefficient of remanent magnetization of γ-Fe2O3 doping with 0.1 mol% Dy can reach -5 ×10-4℃-1.

A Comparative Study on Dry Sliding Wear Characteristics of Al2O3 and Bone Powder Filled Hybrid Composites

The aim of the research was to develop E-glass/jute fiber reinforced epoxy composites with an addition of Al2O3 and bone powder by using hand layup technique and to compare tribological properties of these composites under similar test conditions. The wear experiments were designed according to Taguchi’s (L27) orthogonal array with three control variables such as sliding velocity, filler content and normal load. The results indicated that the normal load for Al2O3 and filler content for bone powder emerged as the significant factors affecting specific wear rate of hybrid composites. An addition of 10 wt% of bone powder or Al2O3 into E-glass/jute fiber reinforced epoxy composites increased the wear resistance considerably, and natural waste bone powder can be used instead of ceramic filler Al2O3 in hybrid composites. After the analysis of control factors, an optimal factor setting has been suggested for specific wear rate and coefficient of friction. Further, the scanning electron microscopy (SEM) images for worn surfaces of hybrid composites were studied. Finally, a confirmation test was carried out to validate the results.

用8-羟基喹啉(oxine)制备Ba(Mg_(1/3)Ta_(2/3))O_3粉体

本文对用８羟基喹啉（ｏｘｉｎｅ）为螯合剂来制备Ｂａ（Ｍｇ１／３Ｔａ２／３）Ｏ３（ＢＭＴ）粉料进行了研究。就ｏｘｉｎｅ的加入量，ｐＨ值的改变对生成钽镁沉淀的产率及其粉料性能的影响进行了研究比较。结果表明：当ｏｘｉｎｅ的加入量大于ＭｇＴａ２Ｏ６摩尔数的３倍，ｐＨ值保持在１０左右时制得的钽镁粉料较为理想，其比表面积达３２ｍ２／ｇ，与ＢａＣＯ３混合后烧结温度比用传统制备法降低１８０～２５０℃。

Noisy-power dissipation and efficiency in NiO/Fe_2O_3 wet grinding by planetary ball mill

The relationship between the efficiency of NiO/Fe2O3 wet grinding and noisy-power dissipation was studied. The optimal grinding parameters were found as: a slurry water content of 64.10%-85.47%, ball number ratio of 360/20, revolution speed of 300.9 r/min, powder-filling ratio of 10.88%, ball-filling ratio of 20.53%-23.88%, and grinding time of approximately 6 h. The discrete element method(DEM) was employed to analyze relationship between the noisy-power dissipation and the grinding efficiency, and equations describing the relationship were derived. The mean particle size of the ground powder decreased with a decrease in the degree of noisy-power dissipation, while the grinding efficiency and the amount of specific impact power used decreased with an increase in the degree of noisy-power dissipation.

(Y_2O_3·CaO)-ZrO_2超细粉的制备及条件对粒径的影响

用化学沉淀法合成Y2O3和CaO共掺杂的ZrO2均匀超细粉并讨论了反应条件对样品粒度的影响。通过TG鄄DTA,XRD,TEM和粒度分布仪等检测手段对产品进行了表征,结果表明,Y2O3含量为2mol%和CaO含量为7mol%时,在550℃得到了全稳定立方相ZrO2,选择适当的合成条件,可得到粒度分布集中、粒径约为30郾1nm的样品。

Effect of Al_2O_3on Structure and Wearability of Composite Coating

The composite coating was prepared by thermal spray welding after making composite powder,which is composed of Ni-based self-melted alloy and AlOceramic powder including nano,sub-micron and micron powders.The influences of contents and sizes of AlOon the structure and wearability were investigated.The results show that the wear resistance of the coating would be increased greatly by adding AlO,but the spray weldability decreases with increasing AlOcontent.So there is an optimal content of AlOpowder.The composite coating with AlOnano or sub-micron powder of 0.5% has the best abrasive resistance,while the optimal content of AlOmicron powder is 1 %.

Effect of Rare Earth on the Crystallization Behavior of Li_2O-Al_2O_3-SiO_2 Glass-ceramic

X-ray powder diffraction and Fourier transform infrared spectroscopy were applied for characterization of Li2O-Al2O3-SiO2 glass-ceramic powders doped with Eu2O3,Gd2O3 and Er2O3,respectively,in the conditions of different heat-treatment temperatures and with various amounts.The powders were derived from the polyacrylamide gel method.The results show that,the wet gels prepared by polyacrylamide perform a unique crystallization behavior in the process of drying,comparing with some customary preparation such as melt processing.The main crystal phase and crystallization sequence of Li2O-Al2O3-SiO2 micro-powders have no distinct with addition of Eu2O3,Gd2O3 or Er2O3,while the crystallization temperature of the β-spodumene decreased and the amount of the β-spodumene increased.

SYNTHESIS AND X-RAY POWDER DIFFRACTION DATA OF A NEW COMPOUND:K_6FeNb_(15)O_(42)

A new compound K6FeNb15O42 was prepared for the first time by solid state reaction in K2O-Fe2O3-Nb2O5 ternary system. The X-ray powder diffraction data of the title compound was measured. K6FeNb15 O42 crystallizes in the hexagonal system with unit cell parameters, a = 9. 1320(4) A ,c = 12. 0670(9) A , and space group P63/mcm (193) , z = 1. The calculated and measured densities are 4. 489 g/cm3 and 4. 485 g. cm3, respectively.

SYNTHESIS AND CHARACTERIZATION OF A NEW COMPOUND :K_6Ti_0.67Nb_15.33O_42

A new compound K6Ti0.67Nb15.33O42 was prepared for the first time by solid state reaction in K2O-Ni2O3-Nb2O5 ternary system. The new compound was characterized by electron probe, X-ray powder diffraction and DTA. The result of X-ray powder diffraction shows that K6Ti0.67Nb15.33O42 crystallizes the hexagonal system with unit cell parameters a = 9. 1341(5) A ,c=12. 090(1)A . and space group P62/mcm(193 ).

Relationship between powder characteristic and internal oxidation of Al in Cu-Al pre-alloyed powders

Since Cu-Al powder characteristics have important effects on the preparation of Cu/Al2O3 composite, the apparent activation energy of Al internal oxidation reaction in Cu-Al pre-alloyed powders with different characteristics was calculated in the present investigation. The microstructure and properties of the synthesized Cu/Al2O3 were studied. The results show that high-energy milling can obviously promote internal oxidation of Al in Cu-Al powders in the same solid solubility. At the same milling conditions and internal oxidation parameters, the solid solution of Al in Cu either in low or high amount will result in the poor microstructure and properties of the Cu/Al2O3 composite. Subsequently, when high-energy milling and internal oxidation are synchronously used to prepare the Cu/Al2O3 composite, there should be an appropriate solubility and milling effect for the pre-alloyed powders.