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The experimental results for the fabrication of TiC powder from TiO₂by self-combustion reaction are summerized as follows; 1) The mole ratio of Mg was the greatest affecting factor in the reaction and the mole ratio of C, particle size of Mg, mixing times affected the reaction as well. 2) MgO and Mg were completely removed by leaching in the 20% HCl solution. 3) The TiC powders had a spherical shape and the particle size was 0.3-0.4 microns with a narrow distribution. 4) Purity of manufactured TiC powder was about 99.925 weight percent.
Recovery of copper from converter slag and native copper deposits and its recovery in L.P.F process mainly depend on flotation, whereas native copper is recovered from its deposits by chemical leaching in some cases. To obtain a better understanding of flotation, the floatability of metallic copper was studied. The floatability of copper with oleic acid and xanthate was tested using Hallimond tube in terms of varied concentration of collector, pH, particle size, flotation time, and also oxidizing tempeature of metal surface. The experimental results obtained are summarized as follows. (1) In flotation of copper, oleic acid and xanthate were the effective collectors, and the collecting power of oleic acid was stronger than that of xanthate. (2) In intermediate pH range except strong acid and strong base, pH of pulp did not in fluence on the floatability of copper. (3) The floatability of copper with oxidized surface decreased compared with that of metallic copper.
Due to the great hardness, hard nitrides have been extensively used in cutting tools and wear-resistant parts. The nitride also shows excellent high-temperature strength and good corrosion resistance. The purpose of this research is to develop the technology for the synthesis of titanium nitride by the reaction of titanium metal and nitrogen. The titanium nitride(TiN_x) can be manufactured by the several methods. In the present work, bulk TiN_x has been synthesized by the reaction of titanium and nitrogen followed by homogenizing annealing. The homogeneous TiN_(x≥1.0) can be obtained at 1000℃ with the lattice parameter and specific gravity of 0.424㎚ and 5.39g/㎤, respectively similar to that of pure grade TiN.
The preparation of β-SiAlON powder by SHS in the system of Si-Al-SiO2-NH4F(β-Si3N4) was investigated in this study. In thepreparation of SiAlON powder, the effect of gas pressure, compositions such as Si, NH4F, β-Si3N4 and additive in mixture on thereactivity were investigated. At 50 atm of the initial inert gas pressure in reactor, the optimum composition for the preparation of pureβ-SiAlON was 3Si+Al+2SiO2+NH4F. The β-SiAlON powder synthesized in this condition was a single phase β-SiAlON with a rodlike morphology.
The dissolution of silver in NH₄SCN solution containing Fe^(+3) ion and O₂ gas as an oxidant was studied. It was found that the dissolution rate was effected by a pH of solution, concentration of NH₄SCN, O₂ gao and Fe^(+3)ion. And also a transition from diffusion control to chemical reaction control has been noted at a reaction temperature of 60℃.
The purpose of the current research work is to develop a technology for preparing pure AlNi using SHS process. The preparation of AlNi intermetallic compounds was affected by the mole ratio, compaction pressure, and particle size. Combustion temperature is decreased with increasing the compaction pressure and the particle size of aluminum. In the course of combustion reaction, high densification of products was directly attained by inducing pressure and forming simultaneously.
Submicron nickel powders were prepared from aqueous solution under hydrothermal condition. The experimental conditions including the types of protective agents, concentration of the solution and the pH were studied in detail. Starting concentration of nickel ion is a dominant factor affecting particle size. It was shown that the subsequent addition of Poly Vinyl Pyrrolidone(PVP) and Sodium Dodecyle Sulfate(SDS) can help to disperse the nickel powder. X-ray diffraction and SEM were employed to characterize the products.
Characteristics of ultra fine Al₂O₃ powders prepared by Sol-Gel process was investigated with hydrolysis condition and calcination temperature. 1) The transition process of Al₂O₃ took place through the series, Boemite Gel(AlooH)-δ-Alumina-θ-Alumina-α-Alumina. 2) The grain size of the calcined products was increased and the surface area was decreased linearly with increasing calcination temperature. 3) The size of first forming product and the agglomerated was less than 10 ㎚ and about 0.1-0.3 ㎛, respectively. 4) The recovery of Al₂O₃ was increased with decreasing PH of solution and increasing both the ratio of Alkoxide : H₂O and agitation temperature.