Sintering Behaviour and Properties of beta'-Si3Al3O3N5 Ceramics

摘要

A study to optimize different production routes for beta'-Si3Al3O3N5 and toinvestigate the influence of the production process parameters and additives on the properties of the product is presented. Production methods used were reaction sintering in a gas pressure furnace, reaction hot pressing and sintering of sialon powder derived from kaolin. Reaction sintering of mixtures of Si3N4, Al2O3 and AlN with only small amounts of CeO2 or CaO addition can produce high density beta'-Si3Al3O3N5. Samples without additive can only be densified by hot pressing. A mechanism comprising the decomposition of mullite and carbon into SiC and Al2O3, whereafter these compounds react with nitrogen to beta'-Si3Al3O3N5 and 15R, is found for the carbothermal production. A study of the influence of the pellet diameter on the reaction rate resulted in the determination of a critical pellet diameter. After thorough milling, the sialon prepared by carbothermal reaction from kaolin can be sintered to high density in 1 hour at 1690 C. The differences in the room temperature properties of the sialons produced are small. The wear behavior of sialon against ZrO2 is reported. The wear resistance of the 'kaolin' sialons is as good as that of the reaction sintered and hot pressed sialons.