Preparing silica aerogel monoliths via a rapid supercritical extraction method.
Preparing silica aerogel monoliths via a rapid supercritical extraction method.
复制标题
通过快速超临界萃取方法制备二氧化硅气凝胶整体。
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
Caroline A. Gorka
中科院分区：
文献类型：
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作者：
Mary K. Carroll;A. Anderson;Caroline A. Gorka
描述了通过快速超临界萃取过程在八小时或更短时间内制造整体二氧化硅气凝胶的程序。该过程需要 15-20 分钟的准备时间，在此期间制备液体前体混合物并将其倒入放置在液压热压机压板之间的金属模具的孔中，然后在热压机内进行几个小时的加工。前体溶液由摩尔比为 1.0:12.0:3.6:3.5 x 10(-3) 的原硅酸四甲酯 (TMOS):甲醇:水:氨组成。在模具的每个孔中，形成多孔硅溶胶-凝胶基质。随着模具及其内容物的温度升高，模具内的压力升高。当温度/压力条件超过基质孔内溶剂（在本例中为甲醇/水混合物）的超临界点后，超临界流体被释放，并且整体气凝胶保留在模具的孔内。使用此过程中使用的模具，可生产直径 2.2 厘米、高度 1.9 厘米的圆柱形整料。通过这种快速方法形成的气凝胶具有与通过其他方法制备的气凝胶相当的性质（低体积和骨架密度、高表面积、介孔形态），这些方法涉及额外的反应步骤或溶剂萃取（较长的过程，产生更多的化学废物）。快速超临界萃取方法也可以应用于基于其他前体配方的气凝胶的制造。
A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The procedure requires 15-20 min of preparation time, during which a liquid precursor mixture is prepared and poured into wells of a metal mold that is placed between the platens of a hydraulic hot press, followed by several hours of processing within the hot press. The precursor solution consists of a 1.0:12.0:3.6:3.5 x 10(-3) molar ratio of tetramethylorthosilicate (TMOS):methanol:water:ammonia. In each well of the mold, a porous silica sol-gel matrix forms. As the temperature of the mold and its contents is increased, the pressure within the mold rises. After the temperature/pressure conditions surpass the supercritical point for the solvent within the pores of the matrix (in this case, a methanol/water mixture), the supercritical fluid is released, and monolithic aerogel remains within the wells of the mold. With the mold used in this procedure, cylindrical monoliths of 2.2 cm diameter and 1.9 cm height are produced. Aerogels formed by this rapid method have comparable properties (low bulk and skeletal density, high surface area, mesoporous morphology) to those prepared by other methods that involve either additional reaction steps or solvent extractions (lengthier processes that generate more chemical waste).The rapid supercritical extraction method can also be applied to the fabrication of aerogels based on other precursor recipes.