Effect of Powder Characteristic and Freeze Condition on the Pore Characteristics of Porous W

Na-Yeon Kwon; Sung-Tag Oh

doi:10.4150/KPMI.2012.19.4.259

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텅스텐 다공체의 기공특성에 미치는 분말특성 및 동결조건의 영향: 권나연, 오승탁
Effect of Powder Characteristic and Freeze Condition on the Pore Characteristics of Porous W: Na-Yeon Kwon, Sung-Tag Oh; Journal of Korean Powder Metallurgy Institute 2012;19(4):259-263
DOI: https://doi.org/10.4150/KPMI.2012.19.4.259

¹서울과학기술대학교 신소재공학과
²서울과학기술대학교 신소재공학과
¹Department of Materials Science and Engineering, Seoul National University of Science and Technology
²Department of Materials Science and Engineering, Seoul National University of Science and Technology

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Abstract

Dependence of the freeze-drying process condition on microstructure of porous W and pore formation mechanism were studied. Camphene slurries with WO_3 contents of 10 vol% were prepared by milling at 50°C with a small amount of dispersant. Freezing of a slurry was done in Teflon cylinder attached to a copper bottom plate cooled at -25°C. Pores were generated subsequently by sublimation of the camphene during drying in air for 48 h. The green body was hydrogen-reduced at 800°C for 30 min, and sintered in the furnace at 900°C for 1 h. After heat treatment in hydrogen atmosphere, WO_3 powders were completely converted to metallic W without any reaction phases. The sintered samples showed large pores with the size of about 70µm which were aligned parallel to the camphene growth direction. Also, the internal wall of large pores and near bottom part of specimen had relatively small pores with dendritic structure due to the growth of camphene dendrite depending on the degree of nucleation and powder rearrangement in the slurry.

Keywords: Porous W;Freeze-drying process;Camphene-based slurry;Hydrogen reduction of WO_3;

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