基于高岭土制备轻量微孔莫来石骨料结构与性能研究

Structure and Properties of Lightweight Microporous Mullite Aggregates Based on Kaolin

以高岭土细粉和α-Al_2O_3微粉为主要原料,采用原位分解法制备轻量微孔莫来石骨料,研究了铝硅摩尔比及热处理温度对轻量微孔莫来石骨料结构与性能的影响。结果表明:经过1400~1600℃热处理后,富铝莫来石试样中除主要物相莫来石相外,还残余一定量刚玉相,接近理论莫来石组成试样及富硅试样均仅检测到莫来石相;所制备的轻量骨料孔径分布主要集中于0.1~4μm范围,均具有微孔结构;随着热处理温度的升高,骨料的体积密度上升,显气孔率下降,耐压强度上升;经1500℃热处理后,富铝试样体积密度为2.49 g/cm3、显气孔率为25.6%、耐压强度为146 MPa;接近理论莫来石组成试样及富硅试样体积密度均小于1.95 g/cm3、显气孔率大于38.0%,1000℃时导热系数均小于0.77 W/(m·K)。

Lightweight microporous mullite aggregates （LMMA） were prepared via an in-situ decomposition pore-forming route using kaolin powder and α-Al2O3 powder as the raw materials. The effect of Al2O3/SiO2 molar ratio and firing temperature on their structure and properties was investigated. The results showed that strong diffraction peaks of mullite were found in the alumina-rich sample together with corundum after firing at 1400-1600 ℃ , whereas only mullite phase was found in the other samples; Microporous structures of as-prepared LMMA and pore sizes in the range of 0.1 to 4 μm were detected in all samples; With increasing the firing temperature, both of bulk density and compressive strength increased, whereas apparent porosities showed an opposite tendency. The bulk density of alumina-rich sample was 2.49 g/cm^3, its apparent porosity and compressive strength were 25.6% and 146 MPa, respectively, after firing at 1500 ℃. The silica-rich sample and the one which had a AI203/SiO2 molar ratio of 3：2 possessed bulk densities lower than 1.95 g/cm^3, apparent porosities higher than 38%, their thermal conductivities at 1000 ℃ were 0.76 W/（ m . K）.