Mass Production of Multishell Hollow SiO₂ Spheres With Adjustable Void Ratios and Pore Structures

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Silica multishell hollow spheres (MHSs) offer advantages in mass transport and chemical reactions due to their porous structure.
• High production costs and low efficiency currently limit the practical application of SiO₂ MHSs.

Purpose of the Study:

• To develop a cost-effective, large-scale production method for void-ratio tunable SiO₂ MHSs.
• To demonstrate the versatility of the method for fabricating other metal oxide hollow spheres.
• To optimize SiO₂ MHSs for controlled release applications.

Main Methods:

• A precursor hydrolysis method was developed for cost-effective, large-scale SiO₂ MHS production.
• An NH₄Cl precipitation-pyrolysis strategy was employed to tune pore diameters and distributions.
• The method was adapted for the synthesis of TiO₂ and SnO₂ hollow spheres.

Main Results:

• The new method achieved a significantly lower cavitation temperature (25 °C) and reduced costs by an order of magnitude.
• SiO₂ MHSs with tunable void ratios exhibited broad controlled release time ranges (30-430 h).
• The synthesis approach is applicable to other metal oxides like TiO₂ and SnO₂.

Conclusions:

• The developed precursor hydrolysis and NH₄Cl precipitation-pyrolysis methods enable scalable and cost-effective production of tunable SiO₂ MHSs.
• These advancements pave the way for industrial-scale applications of SiO₂ MHSs.
• The tunable properties of these MHSs are highly suitable for advanced controlled release systems.