Dilatometric study of the sintering process of SiC doped with Al2O3-Yb2O3 or Al2O3-Dy2O3 oxide systems

Abstract

Silicon carbide, SiC, is a material that, when subjected to liquid-phase sintering, produces ceramics with outstanding properties for a variety of technological applications. Liquid-phase sintering of SiC ceramics involves the use of additives, usually oxides or nitrides, which form eutectics with relatively low melting points. The resulting liquids should wet the SiC thoroughly, as well as dissolve the ²-SiC and precipitate the ±-SiC, the latter with a microstructure that has the desired properties. Numerous studies have focused on liquid-phase sintering of SiC, by varying the composition of liquid forming agents, the composition of these agents relative to SiC, heating and cooling rates, and sintering temperature and time, using a normal graphite resistance furnace. In this case, only the initial (compact) and final (sintered body) phase is known. In other words, nothing is known about what takes place during sintering with respect to the behavior of the material as a function of temperature. One way to gain an insight into the behavior of the material, from the compact to the sintered form, is by means of dilatometric measurements of the shrinkage of the compact as a function of temperature. The use of a dilatometer provides data about shrinkage versus temperature and time, which, when plotted graphically, yields extensive information. The information that can thus be obtained includes: the temperature at which each sintering mechanism is triggered, the maximum rate of shrinkage, and hence, of densification, the end of a sintering process, and even the activation energy required to trigger each sintering mechanism. The aim of this project is to make an in-depth dilatometric study of SiC sintering using Al2O3-Yb2O3 or Al2O3-Dy2O3 oxide systems as liquid-forming agents, whose results should provide answers to the main scientific and technical questions that emerge in studies on the sintering of ceramic materials. (AU)