SGER: Exploratory Study on Low Temperature Synthesis of Nanostructured Particles by a Novel Aero-Sol-Gel Process

CTS-9730535总结 低温合成纳米结构粒子的探索性研究 一种新型的气溶胶-凝胶工艺 G. Beaucage，材料科学与工程助理教授，PI S.E. Pratsinis，化学工程教授，Co-PI 辛辛那提大学，辛辛那提，OH 45221-0012 本项目的目标是通过在气溶胶相中进行溶胶-凝胶反应来研究新型室温纳米颗粒合成工艺的可行性。 第一个实验基地将用二氧化硅和二氧化钛纳米粒子创建。 初步实验已经产生了具有与气凝胶相当的比表面积的纯二氧化硅纳米颗粒（通过质谱法）。 这些分析表明，直径小于1.5 nm的初级颗粒聚集成约30 nm的经典扩散限制聚集体，质量分形维数接近2.5。 长期以来，人们一直在寻找这种聚集体，希望开发具有最大可能表面积的催化载体。 常规的热解方法（例如火焰反应器）不能够得到这样的形态，因为初级颗粒大约大一个数量级。 所提出的过程涉及一个非常简单和成本效益的方法，借用溶胶-凝胶化学和层流，热解（火焰）气溶胶技术。 在初步实验中，溶胶-凝胶前体如四乙氧基硅烷（TEOS）沿着其它反应物使用与火焰反应器中遇到的那些类似的流动室以紧密交错的模式分散在气相中。 然而，这里没有火焰，整个装置是由PVC塑料管制成的，而不是石英合金，成本只有大约100美元。尽管初始设置简单，但通过改变前体浓度、类型和流速，已经在纳米尺度上实现了一定程度的控制。

SUMMARY CTS-9730535 Exploratory Study on Low Temperature Synthesis of Nanostructured Particles By a Novel Aero-Sol-Gel Process G. Beaucage, Asst. Professor of Materials Science and Engineering, PI S.E. Pratsinis, Professor of Chemical Engineering, Co-PI University of Cincinnati, Cincinnati, OH 45221-0012 The goal of this project is to investigate the feasibility of novel, room temperature process for synthesis of nanoparticles by carrying our sol-gel reactions in the aerosol phase. A first experimental base will be created with silica and titania nanoparticles. Preliminary experiments have resulted in pure silica nanoparticles (by mass spectroscopy) with specific surface areas comparable to aerogels. These analyses show primary particles smaller than 1.5 nm in diameter aggregated into classical diffusion-limited-aggregates of approximately 30nm with a mass fractal dimension close to 2.5. Such aggregates have long been sought in the hope of developing catalysis supports with the maximum possible surface area. Conventional pyrolytic methods (e.g. flame reactors) are not capable of such morphologies since the primary particles are about an order of magnitude larger. The proposed process involves an exceedingly simple and cost effective approach which borrows from both sol-gel chemistry and laminar flow, pyrolytic (flame) aerosol techniques. In preliminary experiments, sol-gel precursors such as tetraethoxysilane (TEOS) along with other reactants are dispersed in the gas phase in a closely controllled mode using a flow chamber similar to those encountered in flame reactors. Here, however, there is no flame and the entire apparatus is constructed form PVC plastic tubing, rather than quartz of alloys, costing only about $100. In spite of the simplicity of the initial set-up, some degree of control has already been achieved on the nanoscale by variation of the precursor concentration, type and flow rates.