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首页> 外文期刊>Journal of Sol-Gel Science and Technology >Room Temperature Synthesis of Noble Metal Clusters in the Mesopores of Mechanically Strong Silica-Polymer Aerogel Composites
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Room Temperature Synthesis of Noble Metal Clusters in the Mesopores of Mechanically Strong Silica-Polymer Aerogel Composites

机译：机械强度高的二氧化硅-聚合物气凝胶复合材料的中孔中贵金属簇的室温合成

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Clusters of Ag and Au have been formed in the bulk of mechanically strong silica-polymer aerogel composite monoliths.For that purpose,base-catalyzed silica hydrogels were washed with a 50% w/w ace-tone/diisocyanate (di-ISO) solution,and cured at 55 deg C for 3 days.Unreacted di-ISO solution was washed off with acetone,and the gels were washed with a acetone solutions of Ag~+ or AuCl_4~- (3x10~(-4) mol centre dot L~(-1)),containing also 0.2 mol centre dot L~(-1) of 2-propanol as radical scavenger.Metal clusters were formed upon radiolytic reduction (gamma rays,48-72 h,7-7.5 kGy) of the precursor ions.After irradiation,the hydrogels were washed with acetone,and dried in supercritical CO_2.The resulting aerogel monoliths had a density of 0.56 g centre dot cm~(-3),a surface area of about 160 m~2 centre dot g~(-1),and an average pore diameter of about 200 nm.Transmission electron microscopy showed that the metal clusters are free of contamination,with a cubic face centered structure,and a narrow size distribution,centered around 10 nm.The elastic module,measured with a three-point flexural bending method,was in the 60-70 MPa range,and the load at rupture between 16 and 19 kg.Thermogravimetric analysis showed that the composites were stable up to about 300 deg C.These results are in excellent agreement with results obtained previously for as-grown,di-ISO cross-linked silica aerogels,and show that addition of metal clusters and gamma irradiation to a dose corresponding to a permanence of several years in low earth orbit at high inclination did not affect the chemical identity,the mechanical strength,the porosity and the bulk density of the composite aerogel monoliths.
机译：在大量机械强度高的二氧化硅-聚合物气凝胶复合整料中形成了Ag和Au团簇。为此，用50％w / w丙酮/二异氰酸酯（di-ISO）溶液洗涤碱催化的二氧化硅水凝胶，并在55℃固化3天。用丙酮洗去未反应的di-ISO溶液，并用Ag〜+或AuCl_4〜-（3x10〜（-4）mol中心点L的丙酮溶液洗涤凝胶。 〜（-1）），还含有0.2摩尔中心点L〜（-1）的2-丙醇作为自由基清除剂。金属团簇经辐射还原（γ射线，48-72 h，7-7.5 kGy）形成辐照后，水凝胶用丙酮洗涤，并在超临界CO_2中干燥。所得气凝胶整料的密度为0.56 g中心点cm〜（-3），表面积约为160 m〜2中心点g 〜（-1），平均孔径约为200 nm。透射电子显微镜显示，金属团簇无污染，具有立方面中心结构，并且具有箭头尺寸分布，中心在10 nm左右。用三点弯曲弯曲法测量的弹性模量在60-70 MPa范围内，断裂载荷在16到19 kg之间。热重分析表明，复合材料是在高达300摄氏度的温度下稳定。这些结果与以前获得的成对的，二-ISO交联二氧化硅气凝胶的结果非常吻合，并且表明金属簇和伽马射线辐射的剂量对应于持久性在低倾斜度的高地球轨道上运行几年没有影响复合气凝胶整料的化学特性，机械强度，孔隙率和堆积密度。

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