Deterioration of mechanical properties by the curing of phenolic resin during fabrication of porous PSZ ceramics under high temperatures and high humidities

摘要

Mechanical and microstructural analyses of partially stabilized zirconia (PSZ) ceramics maintained under high temperature and a high relative humidity were investigated to elucidate the relation between the curing of the phenolic resin as a binder and the deterioration of the ceramics. The PSZ powders containing the binder were exposed to the high humidity (85%, 50 °C) and the high temperature (25%, 100 °C) atmospheres for 1 h before compaction. The green densities of the specimens decreased from 3.54 g/cm3 to 3.45 g/cm~3 and to 3.35 g/cm~3, respectively. The flexural strengths decreased about 3% and 8% compared to the specimen exposed to a lower humidity and temperature condition (25%, 50 °C). Rough surfaces and some agglomerated particles with a large volume of voids and internal spaces, were observed in the fracture surfaces of the green bodies. These agglomerates were generated by the curing of the phenolic resin with the formation of methylene bridges. The reaction occurred by the decomposition of hexamine as a curing agent in the high temperature and the high humidity atmospheres.