二步法低温制备六铝酸钙/镁铝尖晶石复相陶瓷

Low-temperature Synthesis of Calcium-hexaluminate/Magnesium-Aluminium Spinel Composite Ceramics by Two Steps Process

以白云石和工业Al(OH)3为原料,采用水热合成和低温煅烧二步法工艺制备六铝酸钙-镁铝尖晶复相陶瓷,探索了水热处理温度对前驱体性能及六铝酸钙/镁铝尖晶石复相陶瓷物相组成和形貌的影响。结果表明:200℃水热处理后的前驱体中,板状三水铝石转变为多孔薄片状薄水铝石;前驱体高温分解后可为复相陶瓷的生成提供高活性原料和六铝酸钙片状形貌的生长空间;二步法工艺可使烧成温度降低100℃以上。白云石添加量为13%时,配料经200℃水热、1 400℃煅烧3 h即可制备出主晶相为六铝酸钙和镁铝尖晶的复相陶瓷,六铝酸钙形貌发育完整,呈交叉片状存在。复相陶瓷的体积密度为1.56 g/cm3,气孔率为61.5%,孔径分布在0.2~1.1μm之间。未水热处理配料于1 500℃保温3 h,制备出六铝酸钙/镁铝尖晶石复相陶瓷,六铝酸钙和镁铝尖晶石晶体衍射峰强度较弱,六铝酸钙片状形貌发育不完整。

A new fabrication process(so called two-steps method, e.g. autoclaved firstly, and then calcined) was developed. A lightweight calcium-hexaluminate/aluminium-magnesium spinel(CA6/Mg Al2O4) composite ceramics was synthesized by this new process using dolomite(Ca Mg(CO3)2) and Al(OH)3 as raw materials. The effect of hydrothermal treatment temperature on properties of precursor, and phase composition and microstructure of lightweight composite ceramics were studied. The results showed that: hydrothermal treatment at 200 ℃, gibbsite in the precusor was translated into boehmite. The precursor is provided with high reaction activity by hydrothermal treatment and provided more space for hexaluminate growth when resolved at high temperature. The two steps method can make the sintering temperature lower over 100 ℃ than traditional process, and the CA6 crystal grows perfectly. When the dosage of dolomite is 13%, precursor through hydrothermal treatment at 200 ℃, composite ceramics which consists of CA6 and Mg Al2O4 can be synthesized after calcining at 1 400 ℃ for 3 h, which achieves density of 1.56 g/cm3, porosity of 61.5%, and pore-size distribution of 0.2–1.1 μm. However, the composite ceramics with the weaker diffraction peak of CA6 and uncompleted crystal appearance can only be prepared at 1 500 ℃ for 3 h by the same batch without hydrothermal treatment.