Encapsulation of NiCl<sub>2</sub> aqueous droplets in water/oil emulsions was conducted with perhydropolysilazane (PHPS), which is a preceramic material for dense silica. Ultra-sonication and SPG methods were chosen for preparation of emulsions. The droplet size of aqueous before and after the encapsulation was measured by dynamic light scattering, and the shape and size of products were observed by transmission electron microscopy. Batyl alcohol and Span 80 were used for surfactants. True spherical silica particles and hollow silica particles (Figure) were obtained by encapsulation. It was found that not the type of surfactant but the size of the droplet was the most important factor to determine the architecture of particles. The true spherical silica particles were obtained from the water droplets with less than 20 nm in diameter, and the hollow particles were formed from the droplets with larger than 25 nm in diameter. The shell thickness of hollow particles was varied with PHPS amount in feed. The emulsion formed by the SPG method provided the large hollow particles with a few micrometers in diameter. Interestingly, relatively small hollow silica particles with ca. 30 - 40 nm in diameter were also obtained. The silica shell of hollow particle was a permselective membrane with a good permeability to water and none for nickel and chloride ions.

Silica hallow particles prepared by encapsulation of water droplets with perhydropolysilazane in hydrophobic solvents

255th National Meeting (2018)

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