Further lowering of temperature for sol-gel processing of ceramic powders

目的是在尽可能低的温度下用溶胶-凝胶法制备α-氧化铝粉体和石英玻璃。取得了以下结果。(1)以丁醇铝为原料，在盐酸存在下，于0 ℃进行溶胶-凝胶反应制备的氧化铝凝胶粉末，在500 ℃左右加入1wt%的Al_2O_3晶种后，部分（40 ~ 50%）转化为α-氧化铝。(2)CL^-在铝氧烷低聚物的低温α-形成过程中起着重要的作用，并被认为是铝氧烷低聚物之间的化学桥梁。(3)AlCl_3和/或Al金属粉可代替醇铝低温合成α-Al_2O_3。(4)HNO_3催化的Al_2O_3凝胶在800 ℃时完全转变为α-Al_2O_3。(5)通过X射线衍射技术分析，无定形生物二氧化硅的原子尺度结构与熔融石英（玻璃）非常相似，这表明即使通过TEOS的溶胶-凝胶反应，也有可能在室温下形成石英玻璃。(6)在有机物质如酒石酸的存在下通过溶胶-凝胶法由TEOS制备的二氧化硅显示出具有类似于熔融二氧化硅的结构。

Sol-gel preparation of α-alumina powders and silica glass at temperature as low as possible was aimed. Following results have been obtained.(1) Alumina gel powders prepared from the aluminum butoxide through the sol-gel reaction at 0 ℃, in the presence of HCI were partially (40 to 50 %) transformed to α-alumina around 500 ℃, when they were seeded with corundum particles to a level of 1 wt %.(2) The CL^- were forun to have an important role in the low temperature α-formation of alumina gels, and were considered to make chemical bridges between aluminoxane oligomers.(3) AlCl_3 and / or Al metal powders could replace aluminum alkoxide for low temperature formation of α-alumina.(4) The HNO_3-catalyzed alumina gel were completely transformed to α-alumina at 800 ℃.(5) The atomic scale structure of amorphous bio-silica, which was analyzed by X-ray diffraction technique, was very similar to fused silica (glass), suggesting the possibility of the room-temperature formation of silica glass even through sol-gel reaction of TEOS.(6) The silica prepared from TEOS by the sol-gel method in the presence of organic substances such as tartaric acid was revealed to have a structure similar to fused silica.