La2O3掺杂氧化铝气凝胶的制备与耐温性能研究

Fabrication and Thermal Stability of La2O3 Doped Alumina Aerogel

摘要:

以仲丁醇铝为前驱体,采用溶胶-凝胶法结合丙酮-苯胺原位生成水技术,通过乙醇超临界干燥,制备出不同含量(1.5 mol%~12 mol%)La₂O₃掺杂的氧化铝气凝胶。采用电子扫描电镜(SEM)、透射电子显微镜(TEM)、X线衍射仪(XRD)、N₂吸附分析仪等仪器表征了La₂O₃掺杂对氧化铝气凝胶的微结构和耐温性能的影响。结果表明：La₂O₃的引入使氧化铝气凝胶的形貌由球状颗粒向大的片状结构转变。适量的La₂O₃掺杂能提高氧化铝气凝胶的比表面积,9 mol% La₂O₃掺杂的氧化铝气凝胶比表面积最大。通过La₂O₃掺杂,能够抑制氧化铝晶粒在高温下的生长和α-Al₂O₃的相变,提高氧化铝气凝胶的耐温性能。1200℃热处理后,La₂O₃掺杂的氧化铝气凝胶仍维持在θ-Al₂O₃,比表面积为86.5 m₂/g,高于未掺杂的氧化铝气凝胶(46 m₂/g)。

Abstract:

La₂O₃ doped alumina aerogels with different La₂O₃ contents are prepared by using aluminum tri-sec-butoxide as precursor via sol-gel route combined with acetone-aniline in situ water formation (ISWF) method, followed by supercritical fluid drying. The effect of La₂O₃ on microstructure and thermal stability of alumina aerogels is investigated by SEM, TEM, XRD and N₂ adsorption. The results show that the morphology of alumina aerogels changes from sphere like accumulated to notably sheet like stacked with the doping of La₂O₃. An appropriate amount of La₂O₃ doping can enhance the specific surface area of alumina aerogels, and the 9 mol% La₂O₃ doping aerogels has the largest specific surface area. In addition, the alumina crystal growth and phase transition of the aerogels upon heat treatment are effectively inhibited by La₂O₃ doping, which significantly improves the thermal stability of the aerogels. After heat treatment at 1200℃ for 2h, the phase of 9 mol% La₂O₃ doped alumina aerogel remains in the θ-Al₂O₃ while that of undoped one is a-Al₂O₃, and the specific surface area of 9 mol% La₂O₃ doped alumina aerogel is 86.5 m₂/g which is higher than the undoped one (46 m₂/g).