Synthesis of Microporous Silica Spheres

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Microporous silica spheres are crucial for applications like chemical mechanical polishing.
• Controlling particle size distribution and porosity is essential for optimizing slurry performance.
• Existing templating methods for silica synthesis have limitations in achieving uniform particle size and desired porosity.

Purpose of the Study:

• To investigate methods for synthesizing spherical microporous silica powders with narrow size distribution.
• To compare two templating methods: co-hydrolysis of alkoxides and adsorption of glycerol.
• To understand the effect of glycerol as a porogen on the silica precipitation mechanism and particle formation.

Main Methods:

• Precipitation technique involving hydrolysis of silicon alkoxide in ethanol.
• Templating using co-hydrolysis of alkoxides with a porogen function.
• Templating using adsorption of glycerol as an organic porogen.
• Removal of organic porogen via calcination.
• Analysis using an aggregative growth model.

Main Results:

• Co-hydrolysis with >20 mol% porogen alkoxide resulted in nonuniform silica particles with large size distribution.
• The glycerol method successfully synthesized submicrometer silica spheres with narrow size distribution and ~40 vol% porosity.
• Glycerol incorporation led to a larger mean particle size due to a second aggregative growth phase.
• The aggregative growth model explained the effect of glycerol on particle formation and colloidal stability.

Conclusions:

• Glycerol is an effective porogen for synthesizing uniform, submicrometer microporous silica spheres.
• The synthesis method allows for control over particle size and porosity, enabling tailored silica slurries.
• This research provides a pathway for developing advanced silica materials for chemical mechanical polishing and other applications.