WO3-TiH2 혼합분말의 동결건조 및 수소환원에 의한 W-Ti 다공체 제조
Fabrication of Porous W-Ti by Freeze-Drying and Hydrogen Reduction of WO3-TiH2 Powder Mixtures
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Porous W-10 wt% Ti alloys are prepared by freeze-drying a WO3-TiH2/camphene slurry, using a sintering process. X-ray diffraction analysis of the heat-treated powder in an argon atmosphere shows the WO3 peak of the starting powder and reaction-phase peaks such as WO2.9, WO2, and TiO2 peaks. In contrast, a powder mixture heated in a hydrogen atmosphere is composed of the W and TiW phases. The formation of reaction phases that are dependent on the atmosphere is explained by a thermodynamic consideration of the reduction behavior of WO3 and the dehydrogenation reaction of TiH2. To fabricate a porous W-Ti alloy, the camphene slurry is frozen at -30oC, and pores are generated in the frozen specimens by the sublimation of camphene while drying in air. The green body is hydrogen-reduced and sintered at 1000oC for 1 h. The sintered sample prepared by freeze-drying the camphene slurry shows large and aligned parallel pores in the camphene growth direction, and small pores in the internal walls of the large pores. The strut between large pores consists of very fine particles with partial necking between them.
Abstract
Porous W-10 wt% Ti alloys are prepared by freeze-drying a WO3-TiH2/camphene slurry, using a sintering process. X-ray diffraction analysis of the heat-treated powder in an argon atmosphere shows the WO3 peak of the starting powder and reaction-phase peaks such as WO2.9, WO2, and TiO2 peaks. In contrast, a powder mixture heated in a hydrogen atmosphere is composed of the W and TiW phases. The formation of reaction phases that are dependent on the atmosphere is explained by a thermodynamic consideration of the reduction behavior of WO3 and the dehydrogenation reaction of TiH2. To fabricate a porous W-Ti alloy, the camphene slurry is frozen at -30oC, and pores are generated in the frozen specimens by the sublimation of camphene while drying in air. The green body is hydrogen-reduced and sintered at 1000oC for 1 h. The sintered sample prepared by freeze-drying the camphene slurry shows large and aligned parallel pores in the camphene growth direction, and small pores in the internal walls of the large pores. The strut between large pores consists of very fine particles with partial necking between them.
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