Abstract: In order to systematically study the crystallization rules of fused silica ceramics,fused silica particles with three different particle sizes (d₅₀=660.82,42.12,and 5.58 μm) were used as raw materials to prepare fused silica ceramics at 1 250-1 400 ℃.The crystallization kinetics and crystallization processes were analyzed by the isothermal phase transition method and polarized light microscopy.The results show that with the decrease of the particle size,the crystallization activation energy of the fused silica ceramics gets lower,the crystallization onset temperature decreases continuously,and the crystallinity increases rapidly,generating more larger microcracks.The analysis shows that because of the different mass transfer efficiency in the solid phase sintering process,the Si—O bond rearrangement can fully occur between smaller fused silica particles thus crystallization is more likely to occur.In addition,fused silica crystallization exhibits the surface nucleation mechanism:crystallization starts from the surface of the fused silica particles and then gradually spreads inwards.

Key words: fused silica, particle size, crystallization, activation energy, nucleation mechanism

摘要： 为系统研究熔融石英陶瓷的析晶规律,以3种不同粒径(中位径分别为660.82、42.12、5.58 μm)熔融石英为原料,分别在1 250~1 400 ℃制备了熔融石英陶瓷,分别采用等温相变法和偏光显微技术分析了析晶动力学和析晶过程。结果表明:随着熔融石英粒径减小,熔融石英陶瓷的析晶活化能降低,析晶开始温度持续降低,析晶量快速增加,导致其生成的微裂纹数量更多、尺寸更大。分析认为,固相烧结过程中的物质扩散传质效率不同,粒径更小的熔融石英颗粒间可以更充分地发生Si—O键重排,更容易析晶。此外,熔融石英析晶表现为表面成核机制,即析晶开始于熔融石英颗粒边缘,并逐渐向内部扩散。

关键词: 熔融石英, 粒径, 析晶, 活化能, 成核机制