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STUDY ON STRUCTURE AND PROPERTIES OF Ni-W-SiC COMPOSITE COATING

K. Y Ma , Z.C. Guo , M.F. Wen , X. W Yang and F. Han ( Kunming University of Science and Technology , Kunming 650093 , China China National Nonferrous Metals Imp. & Exp. Corp. , Shanxi Company , Xi'an 710000 , China )

金属学报(英文版)

The effects of electroplating conditions on the composition of N-W-SiC composite coating were studied; the znfiuence of heat-treatment and nitrocarburization on the microstructure, hardness and wear resistance of the coating were discussed. The results showed that an amorphous composite coating, containing(wt%) 50-55Ni, 42-45.IW and 3.0-7.6SiC, could be electroplated on the matrix. Afier heat-treatment or nitrocarburization the coating crystallized to form some new phases, and the haordness and wear resistance of the composite coating were enhanced retmarkably.

关键词: electroplating , null , null , null

Hydrogen Reduction and Microstructural Changes of ISF Sinter

Yixin HUA (Dept. of Metallurgy , Kunming University of Science and Technology , Kunming 650093 , China)F.R.Sale (Manchester Materials Science Centre , University of Manchester and UMIST , Manchester M1 7HS , UK)

材料科学技术（英文）

The reduction rate and microstructural changes of imperial smelting furnace (ISF) sinter have been investigated by means of thermogravimetric analysis, X-ray difFraction (XRD), scanning electron microscope (SEM ), energy dispersive analysis of X-ray (EDAX) and optical microscope.It is demonstrated that the overall reaction rate of the reduction is influenced by temperature and hydrogen partial pressure in H2 /N2 gas mixtures. There are two distinct zones observed in the partially reduced sinter. The reduction of zincite proceeds predominantly in a narrow range between the two zones, while the reduction of tead oxide and silicate takes place throughout the sinter. The differences between zincite and lead oxide or silicate in reducibility are analysed by thermodynamlcs. The phase transformations and microstructural changes occurring during the reduction process are discussed

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FRACTAL PORE DIFFUSION MODEL OF FLUIDS IN POROUS MEDIA

D.P. Tao(Department of Metallurgy , Kunming University of Science and Technology , Kunming 650093 , China)

金属学报(英文版)

A fractal pore diffusion model of fiuidS in porous media which is in good agreement with the experimental data of the coke-CO2 reaction, has been derived by using the Mandelbrot's fractal length-area relation. Based on the model, a new formula and its interpretation about the tortuosity of pore structures of a porous medium have been suggested, from which the fructal pore dthesion resistance has been defined. The resistance ascends obviously with the fmctal pore dimension and the conversion rutio increasing, especially in the middle-latter period of fiuid-solid reactions.

关键词: fractal model , null , null , null

MICROWAVE-AIDED DECOMPOSITION OF PYROLUSITE

Y.X. Hua(Department of Metallurgy , Kunming University of Science and Technology , Kunming 650093 , China)

金属学报(英文版)

The microwaves were used to stimulate the decomposition process of pyrolusite under air atmosphere. It was shown that the overall rate of the process was significantly enhanced when using microwaves instead of conventional heating. The applications of microwaves in the decomposition of pyrolusite could appreciably lower the reaction temperatures.

关键词: microwave , null , null

MICROWAVE-ASSISTED CARBOTHERMIC REDUCTION OF ILMENITE

HUA Yixin and LIU Chunpeng(Department of Metallurgy , Kunming University of Science and Technology , Kunming 650093 , China)Manuscript received 15 Augnst 1995 , in revised form 16 April 1995

金属学报(英文版)

The microwave-assisted carbothermic reduction of ilmenite was investigated by thermogravimetric analysis under argon atmosphere. A comparison between microwave assisted reduction and the conventional one was made. It was demonstrated that the instantaneously volumetric heating of microwaves could significantly enhance the overall reduction process. By microwave application, the reduction could take place at much lower temperatures and the activation energy for the process could be lowered.The mechanism of the reduction was discussed according to the experimental data.

关键词: : microwave; carbothermic reduction; ilmenite

Separation of Cobalt from Iron by Chloride Hydrolysis at Elevated Temperature

Keyi MA , Zuze ZHU and Chuanyi YAN(Kunming University of Science and Technology , Kunming 650093 , China)

材料科学技术（英文）

The hydrolysis rate of Co-bearing ferrous chloride at elevated temperature and the conditionsof separation of Co from Fe have been investigated. The hydrolysis process is comprised of theinterfacial chemical reaction and the intra-grain diffusion. At the stage under the control of theinterfacial chemical reaction, the apparent rate constant k equals to 198.79exp(-80.57/RT). Theeffects of the temperature, the partial pressure ratio of water vapor and the reaction time on theCo recovery and the separation of Co from Fe are examined. The optimum hydrolysis conditionsare determined.

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EVAPORATION KINETICS OF SnS FROM SnS-Cu_2S-FeS MELTS

Y. X. Hua and C.P. Liu(Depatment of Metallurgy , Kunming University of Science and Technology , Kunming 650093 , China)

金属学报(英文版)

The evaporation kinetics of SnS from SnSCu2SFeS teruary system was investigated against matte grade, tetnperature and carrier gas flow rate. It was demonstrated that the evapomtion process is controlled by gas-phase mass transport. The increases of the flow rote of carrier gas and the temperature could increase the gas-phase mass transport coefficient and the Partial pressure of SnS over the melts, respectively, and hence would appreciably promote the evaporation process. An increase of matte grade could lower the activitv coefficient of SnS in the melts, which in turn would cause the reduction of the evapomtion rate of SnS

关键词: evaporation kinetics , null , null

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