Development of porous ceramics with high strength and large surface area by spark plasma sintering

2001 Fiscal Year Final Research Report Summary

• Project/Area Number: 12650690
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Structural/Functional materials
• Research Institution: Tohoku University
• Principal Investigator: OMORI Mamoru Tohoku University, Institute for Materials research, Research Associate, 金属材料研究所, 助手 (30005954)
• Project Period (FY): 2000 – 2001
• Keywords: Silicon carbide / Cubic silicon carbide / Hexagonal silicon carbide / Spark plasma sintering / Porous ceramics / Sintering / Crystal growth

Research Abstract

An electric source of spark plasma sintering (SPS) is a generator of pulsed direct current. Graphite dies are heated with this pulsed direct current, and powders in them were exposed in the electric field. Sintering of metal and ceramics powders are enhanced by effect of the electric field. Porous ceramics is used in various fields such as filters, carriers of catalysis for chemical reactors and cleaning of the exhaust gas of automobiles, and so on. The strength of porous ceramics is reduced due to pours. If the low strength is improved, the porous ceramics should be used in new fields.
There are cubic and hexagonal crystals of commercially available SiC powders, β-SiC and α-SiC. These two powders were sintered between 1600 ℃ and 2200 ℃ by SPS in a vacuum. The crystal structure of the β-SiC powder was transformed to α-SiC stable at high temperature. The texture of the compact sintered from the β-SiC powder was composed of connected long crystals and contained 30 % pores. There was no grain boundary between the connected crystals ; that is called a porous single crystal. α-SiC crystals included in the β-SiC crystal grew and connected with other crystals with right crystal axes. The density did not increase with increasing heating temperatures, and the porous ceramics was stable at high temperatures. The compact sintered from the α-SiC powder had a many grain boundaries, and its densification was conducted by sintering mechanism and progressed gradually by heating. The α-SiC compact was not sable at high temperatures. The strength of the β-SiC compact was 141MPa and one seventh as large as that of a dense SiC body.
It is concluded that a porous SiC ceramics with the high strength and large surface area is fabricated from the β-SiC powder by SPS.