A NiAI-based composite with HfB2 dispersed particles has been synthesized by mechanical alloying of Ni, Al, Hf and C powders. The formation mechanism of NiAI-HfC during milling can be attributed to two chemical reacti...A NiAI-based composite with HfB2 dispersed particles has been synthesized by mechanical alloying of Ni, Al, Hf and C powders. The formation mechanism of NiAI-HfC during milling can be attributed to two chemical reactions: Ni+AI→NiAI+△H; Hf+C→HfC+△H, induced by mechanical collision in a certain period of time, which results in an abrupt exothemic reaction. Hot pressing (HP) and hot isostatic pressing (HIP) have been used to make the NiAI-10HfC compacts near fully dense. Compressive testing from room temperature to 1000℃ indicated that the yield stress of NiAI-10HfC composite is 3-4 times higher than that of cast NiAl and correspond to the MA NiAI-10TiB2 composite. In the meantime, yield strength at high temperature is dependent on strain rate, and deformation is controlled by diffusion mechanism.展开更多
The α-SiC in 0.5μm size powders were coated with Al_2O_3 and Y_2O_3 by a coprecipitation coating (CPC) method forfabrication of SiC/YAG composites. The same powder preparation was carried out by conventional mechani...The α-SiC in 0.5μm size powders were coated with Al_2O_3 and Y_2O_3 by a coprecipitation coating (CPC) method forfabrication of SiC/YAG composites. The same powder preparation was carried out by conventional mechanical mixing(MM) method for comparison. Two kinds of SiC/YAG composites were manufactured by pressureless sintering usingthe different powders, named CPC composite and MM composite thereafter respectively. It is shown that the CPCcomposite has the advantages of homogeneous distribution of YAG phase and of being sintered to high density ata low temperature, 100℃ lower than that of MM composite. The strength (573 MPa) and hardness (23.3 GPa) ofthe CPC composite are significantly higher than those (323 MPa and 13.5 GPa) of the MM composite, respectively.展开更多
The gold sulfide concentrate with a high As content in Liangshan District, Sichuan Province, China, is a potentially important resource. This paper describes experiments of dearsenification of gold concentrate in a we...The gold sulfide concentrate with a high As content in Liangshan District, Sichuan Province, China, is a potentially important resource. This paper describes experiments of dearsenification of gold concentrate in a weakly reduced atmosphere in a rotary pipe furnace. The results showed that the optimal parameters were a temperature range of 650-700℃, 15%-16% CO2 of gas and a reaction time of 30-40 min. The removal rate of arsenic and sulfur was over 95% and 25%-28%, respectively. With further oxidization and roasting, residue sulfur in the roasted materials was dropped to below 4%, and the cyanide leaching recovery of gold was over 92%.展开更多
The influence of the heat of reaction during the aluminothermic process for the production of ferrotitanium was investigated. The effect of the variation of the heat of reaction on FeTi and Ti recovery and the topogra...The influence of the heat of reaction during the aluminothermic process for the production of ferrotitanium was investigated. The effect of the variation of the heat of reaction on FeTi and Ti recovery and the topographical analysis of slag produced showed that FeTi and Ti recovery increased and Al content in the alloy decreased with the increase of the absolute value of ΔH when │ΔH│<2584.24K·J/kg; however, when │ΔH│>2584.24K·J/kg, FeTi and Ti recovery decreased with an increase of the absolute value of ΔH. Therefore, the heat of reaction in the aluminothermic process of ilmenite should be strictly controlled to -2584.24K·J/kg.展开更多
基金This research was supported by the National Natural Science Foundation of China(59895152)the National High Technology Committee of China(863-715-005-0030).
文摘A NiAI-based composite with HfB2 dispersed particles has been synthesized by mechanical alloying of Ni, Al, Hf and C powders. The formation mechanism of NiAI-HfC during milling can be attributed to two chemical reactions: Ni+AI→NiAI+△H; Hf+C→HfC+△H, induced by mechanical collision in a certain period of time, which results in an abrupt exothemic reaction. Hot pressing (HP) and hot isostatic pressing (HIP) have been used to make the NiAI-10HfC compacts near fully dense. Compressive testing from room temperature to 1000℃ indicated that the yield stress of NiAI-10HfC composite is 3-4 times higher than that of cast NiAl and correspond to the MA NiAI-10TiB2 composite. In the meantime, yield strength at high temperature is dependent on strain rate, and deformation is controlled by diffusion mechanism.
基金This work was supported by the National Natural Science Foundation of China(No.50372041)National“863”Plan(No.2003AA305620).
文摘The α-SiC in 0.5μm size powders were coated with Al_2O_3 and Y_2O_3 by a coprecipitation coating (CPC) method forfabrication of SiC/YAG composites. The same powder preparation was carried out by conventional mechanical mixing(MM) method for comparison. Two kinds of SiC/YAG composites were manufactured by pressureless sintering usingthe different powders, named CPC composite and MM composite thereafter respectively. It is shown that the CPCcomposite has the advantages of homogeneous distribution of YAG phase and of being sintered to high density ata low temperature, 100℃ lower than that of MM composite. The strength (573 MPa) and hardness (23.3 GPa) ofthe CPC composite are significantly higher than those (323 MPa and 13.5 GPa) of the MM composite, respectively.
文摘The gold sulfide concentrate with a high As content in Liangshan District, Sichuan Province, China, is a potentially important resource. This paper describes experiments of dearsenification of gold concentrate in a weakly reduced atmosphere in a rotary pipe furnace. The results showed that the optimal parameters were a temperature range of 650-700℃, 15%-16% CO2 of gas and a reaction time of 30-40 min. The removal rate of arsenic and sulfur was over 95% and 25%-28%, respectively. With further oxidization and roasting, residue sulfur in the roasted materials was dropped to below 4%, and the cyanide leaching recovery of gold was over 92%.
基金This work was supported by Yunnan Science and Technology Department Contract(No.2002PY0I,2001 HG 04).
文摘The influence of the heat of reaction during the aluminothermic process for the production of ferrotitanium was investigated. The effect of the variation of the heat of reaction on FeTi and Ti recovery and the topographical analysis of slag produced showed that FeTi and Ti recovery increased and Al content in the alloy decreased with the increase of the absolute value of ΔH when │ΔH│<2584.24K·J/kg; however, when │ΔH│>2584.24K·J/kg, FeTi and Ti recovery decreased with an increase of the absolute value of ΔH. Therefore, the heat of reaction in the aluminothermic process of ilmenite should be strictly controlled to -2584.24K·J/kg.
