高比表面积Y掺杂Al2O3气凝胶制备及Y的作用机制

Preparation of Y-doped Al2O3 aerogels with high specific surface areas and Y function

以Al(NO3)3、Y(NO3)3的水合物为前驱体,结合溶胶-凝胶法和超临界干燥方式,制备Y掺杂Al2O3气凝胶。研究气凝胶经热处理后的比表面积、晶相、微观形貌及气凝胶中Y元素分布形式的变化规律,并分析Y对气凝胶热稳定性的作用机制。结果表明:制备的Y掺杂Al2O3气凝胶具有较高的初始比表面积(483 m2/g),在高温下具有较高的比表面积保留(1200℃处理后仍有80 m2/g)。Y元素在Al2O3气凝胶中均匀分布,抑制了高温下Al3+的扩散和重排,经1200~1300℃热处理后,Y元素由均匀分布转变为非均匀分布,在Al2O3颗粒表面生成Y和Al的化合物,能够进一步减少颗粒间的颈部接触,抑制烧结和相变。经1300℃热处理后,由于Y和Al的化合物本身比表面积较低,气凝胶总的比表面积发生显著下降。

Y-doped Al2O3 aerogels were prepared by aluminum nitrate and yttrium nitrate precursors through the sol-gel and supercritical drying method.The specific surface areas,pore structures,phase transformation,micro structures and Y distribution of calcined Y-doped Al2O3 aerogels were investigated,and the influence mechanism of Y was discussed.The prepared Al2O3 aerogels had high specific surface areas(483 m2/g)and maintened at elevated temperatures(80 m2/g at 1200℃).The uniformly distributed Y in Al2O3 aerogels suspended the vibration and rearrangement of Al3+.At 12001300℃,there was an enrichment of Y in Al2O3 aerogels,and the compounds of Y and Al emerged at the surface of Al2O3 particles.These compounds could further suppress the sintering and phase transformation toα-Al2O3,but the specific surface area of Y-doped Al2O3 aerogels decreased dramatically at 1300℃since the surface area of these compounds themselves was small.