Characterization of porosity of ammonia catalysed alkoxysilane silica
Characterization of porosity of ammonia catalysed alkoxysilane silica
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DOI：
10.1016/s0022-3093(97)00414-6
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发表时间：
1997-12-01
影响因子：
3.5
通讯作者：
Burneau, A
中科院分区：
文献类型：
--
作者：
Labrosse, A;Burneau, A
以四烷氧基硅烷为原料，在浓氨溶液中进行水解缩合反应，制得单分散二氧化硅微球，并对其结构进行了研究。用透射电子显微镜观察其粒径在10-730 nm之间。热重分析和Si-29核磁共振分析表明，尽管大多数样品的比表面积很小，但通过Kr吸附测定，硅醇的浓度很高，接近5.4mmolOg(-1)。这种对比是由珠子的超微孔结构解释的。在这些珠子的超微切片上，直接观察到了小于1 nm的孔洞。这种孔隙率也解释了用十盐比浊法测量的低密度和在直径10 nm的拉曼光谱中观察到的10 cm(-1)以下的振动模式。一些单分散的二氧化硅微珠的样品显示出了奇特的特性。I型Kr等温线与很长的平衡时间和高达210 m(2)g(-1)的Kr和385m(2)g(-1)的N-2的高比表面积相关联，证明了它们的微孔隙度。用比浊法测得的密度仍然比通常的样品小。热处理和氢氧化钠反应显示了这些微孔二氧化硅微球的各种性质。(C)1997年爱思唯尔科学公司。
Monodispersed silica spheres were obtained by hydrolysis and condensation of a tetraalkoxysilane in concentrated ammonia solutions and their structure was studied. The particle size, in the range 10-730 nm, was observed by transmission electron microscopy. Thermogravimetric analysis and Si-29 nuclear magnetic resonance reveal a high silanol concentration, close to 5.4 mmol OH g(-1), despite a very small specific surface area of most samples, determined by Kr adsorption. This contrast is explained by an ultramicroporous structure of the beads. Pores smaller than 1 nm have been directly observed on transmission electron micrographs of ultramicrotomed slices of these beads. This porosity also explains both the low density measured by decaline picnometry and the vibration mode observed in Raman spectra below 10 cm(-1) for particles 10 nm diameter. Some samples of monodispersed silica beads display peculiarities. Type I Kr isotherms, associated with very long equilibrium times and high surface areas up to 210 m(2) g(-1) with Kr and 385 m(2) g(-1) with N-2, prove their microporosity. The density obtained by picnometry is still smaller than for usual samples. Thermal treatments and reaction with NaOH illustrate various properties of these microporous silica spheres. (C) 1997 Elsevier Science B.V.