Silica nanoparticles are advanced functional materials for its wide utility in a wide range of emerging applications, such as catalyst support, adsorption of CO2, and drug delivery in biomedical engineering. Generally, the preparation of silica nanoparticles was categorized as either wet- or vapor-phase processes. Compared with the wet-phase method, the product obtained using vapor-phase techniques is of higher purity and has a more uniform particle-size distribution and larger surface area. However, the high requirement for equipment and high energy consumption is currently the major drawback of vapor-phase method due to the involving of a hydrogen-oxygen flame (1800ºC). Meanwhile, SiCl4 is a byproduct of the polysilicon industry, which can cause severe environmental pollution, but also a potential precursor of nano-silica. We first reported an economical and environmentally benign method for the preparation of silica nanoparticles by hydrolysis of silicon tetrachloride vapor with water vapor at a low temperature (~150ºC). Analysis by XRF, XRD, N2 physisorption, SEM, and examination of nanoparticle size distribution revealed the high quality of the as-synthesized nano-silica compared to the commercial fumed silica (N20, Wacker Chemie, Germany). The porous amorphous silica had high purity (99.89 wt%), large specific surface area (418 m2/g) and a size distribution (163 ± 41 nm, polydispersity index = 0.221), and was prepared at an optimum condition (reaction temperature of 150ºC and reaction time of 5 s). The thermal stability of the silica nanoparticles was verified by demonstrating that calcination at temperature ≤ 600ºC could remove surface hydroxyl groups, achieving hydrophobic modification, while maintaining particle mesostructure. The reduced cost of the synthesis method presented here is a result of the low reaction temperature and the recycling of byproduct, making it a green and promising approach for wide use in various high end applications.

Novel vapor-phase hydrolysis approach for preparing of nanosilica: Recycling of silicon tetrachloride

249th National Meeting (2015)

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