高纯高导热BeO陶瓷材料烧结工艺研究

Studies on the Sintering Process of High Pure BeO Ceramics with High Thermal Conductivity

选用两种高纯氧化铍(BeO)瓷料(一种为原生料,另一种为瓷件料),以不同的烧结工艺制备高纯BeO陶瓷。通过品红实验和扫描电镜(SEM)观察发现:采用原生料制备的陶瓷素坯在天燃气方式加热的钟罩炉中难以致密化,陶瓷容易吸红。这主要是由于高纯BeO的原生料的烧结是以蒸发-凝聚传质方式为主,扩散传质方式为辅,在一定的温度和压力下,有BeO(蒸汽)+CH4易产生BeOH+CH3或CH3OH+Be。采用瓷件料制备的陶瓷素坯在天燃气热钟罩炉中能致密化,陶瓷不易吸红。这主要是由于高纯BeO的瓷件料的烧结是以扩散传质方式为主,以蒸发-凝聚传质方式为辅,烧结后期离子沿粒界作快速迁移,靠界面扩散使瓷体致密化。

In this paper, high pure BeO ceramics have been produced under different sintering conditions using two kinds of BeO powders （one is original powder and the other is crushed BeO ceramic powder） as raw materials. Fuchsine experiment and SEM observation showed that the green chip made from original BeO powder could not be well sintered in bell furnace in CH4 atmosphere and the ceramic with low density is easy to absorb fuchsine. This result can be explained that the sintering process is mainly dependent on the evaporation-condensation mechanism, assisted by the diffusive mass transfer. BeOH＋CH3 or CH3OH＋ Be would be yielded by the reaction between BeO vapor and CH4 under certain temperature and pressure. On the contrary, dense ceramic using crushed BeO ceramic powder as raw material could be obtained when sintered in bell furnace, in CH3 atmosphere. It is due to the fact that the sintering process in this system is primarily through diffusive mass transfer, and the evaporation-condensation mass transfer is auxiliary. Thus, the densification is proceeded by the fast migration of ions along the grain boundaries in final sintering time.