改性SiO2源对合成高纯莫来石材料结构及性能的影响

Effect of Modified SiO Source on Structure and Properties of High-Purity Mullite Materials

在天然石英中引入质量分数为8%的γ-Al_(2)O_(3),经1550℃加热处理实现了对SiO2源的掺杂改性。以不同SiO2源和γ-Al_(2)O_(3)为原料,对比研究了改性SiO2源对合成高纯莫来石材料结构和性能的影响。结果表明:SiO2中掺入少量γ-Al_(2)O_(3)后,其熔融温度降低;改性SiO2源在较窄的温度范围(1570~1580℃)内转化为富SiO2液相。大量富SiO2液相的形成促进了莫来石化反应,加速了颗粒重排,提高了材料的致密度,从而改善了高纯莫来石材料的反应烧结性能。在煅烧过程中,富SiO2液相逐渐被反应消耗转化为高温相的莫来石;同时,改性SiO2源熔融提供的液相环境,促进了莫来石晶体的各向异性生长。经1700℃保温3 h煅烧后,莫来石晶体发育呈柱状并形成交叉的网络结构,增强了晶体间的结合程度。采用改性SiO2源合成的高纯莫来石材料,表现出更好的力学性能。

To assess the effects of modified SiO2 sources on the structure and properties of high-purity mullite materials by reactive sintering method, the modified SiO2 source was fabricated by doping 8%(mass fraction) γ-Al_(2)O_(3) into natural quartz and heating at 1 550 ℃. Subsequently, mullite samples were prepared by using different SiO2 sources and γ-Al_(2)O_(3) as raw materials. The results show that the melting temperature of SiO2 decreases after adding a small amount of γ-Al_(2)O_(3). The modified SiO2 sources are transformed into a large amount of SiO2-rich liquid phase in a narrow temperature range(1 570 ℃ to 1 580 ℃). The formation of a large amount of SiO2-rich liquid phase promotes the mulliteization reaction, accelerates the particle rearrangement, increases the density of materials, and improves the reaction sintering property of high-purity mullite materials. During the calcination process, the SiO2-rich liquid phase is gradually consumed by the reaction and converted into high-temperature mullite. Meanwhile, the liquid phase environment provided by the melting of modified SiO2 source promotes the anisotropic crystal growth of mullite. After calcination at 1 700 ℃ for 3 h, the obtained mullite grains morphology exhibits columnar shape and forms a cross network structure, which enhances the degree of bonding between crystals. Therefore, high-purity mullite materials with the modified SiO2 sources exhibit higher density and better mechanical properties.