Fabrication and Properties of Porous SiC Sheets from Clutch Lining Wastes

Abstract

During the production of friction sheets with their pack assemblies used in clutch for automatic transmission of motorcars, useless sheet fragments are formed and have to be disposed of, amounting to several tens of tons per a month. These wastes are composed of cellulose, diatomaceous earth, synthetic fibers, and carbon powder/fibers, impregnated with phenol resin as the bonding medium. When two types of these sheets are heated in an inert atmosphere at 600°C, they become porous and contain excess carbon formed by decomposition of the resin. The reaction of these porous sheets with a source of silicon such as tetra-ethoxy-silane or SiO at 1500°–1600°C results in the formation of porous silicon carbide (SiC) (∼80% porosity). If the porous sheets are impregnated with phenol resin and again reacted with SiO gas at 1500°–1600°C in Ar, SiC sheets with reduced porosity (<70%) are obtained. The surfaces and cross sections of the SiC sheets were observed by scanning electron microscopy, and their pore size distribution in the samples heated at 1600° and 1900°C in Ar was determined by mercury porosimetry. The oxidation and corrosion properties of the SiC sheets with 60% and 80% porosities were determined at 1200°C in Ar/O2 in the absence and presence of NaCl vapor.