Synthesis and characterization improvement of gradient density aerogels for hypervelocity particle capture through co-gelation of binary sols

Abstract

In this paper, we reported the preparation technics and details of gradient density aerogels (GA) via continuous formation technics, and introduced an effective and facile method to analyze its physical properties and microstructure correctly, since these properties are density dependent. With tetramethoxysilane as precursor and two-step sol–gel process, high transparence and crack-free of GA were fabricated, the density ranges from 0.02 to 0.2 g/cm3. The linear shrinkage of GA increases continuously with density increases from top to bottom. Base on systematically analyze the formation mechanism of GA, the co-gelation of binary sols with different concentrations method was developed to prepare mixed aerogels, which possessed a similar internal skeleton structure compare with GA. The internal skeleton structure of these aerogels is cross-linked by distinct sizes silica particles from two concentrations of silica-sols. Four mixed aerogels corresponding to different density positions of GA (a—0.15, b—0.12, c—0.09, and d—0.05 g/cm3) were selected to test. X-ray phase contrast method was used to shown the density distribution of GA. BET observation, SEM analysis, and TEM study, DMA and UV–vis results shown that GA are with excellent performance in physical properties, such as high optical transmittance, and good mechanical strength, which are critical characteristics for practical applications of GA, particularly in capture particle areas, for easy observation and lossless capture.