Spinodal Decomposition by a Two-Step Procedure for Nano Porous Silica

Area of Science:

• Materials Science
• Chemical Engineering
• Physical Chemistry

Background:

• Phase separation in glass systems is crucial for creating advanced materials.
• Controlling spinodal structure morphology is key for tailored material properties.

Purpose of the Study:

• To achieve a spinodal structure with <70 nm periodic distance and ~60% porosity in the Na2O-B2O3-SiO2 system.
• To investigate the effects of a two-step phase separation process and Al2O3 addition on structure evolution.

Main Methods:

• Theoretical modeling and experimental exploration of phase separation kinetics.
• Utilizing a two-step heat treatment process for controlled structure formation.
• Incorporating an inverse-square law model for SiO2 diffusion kinetics.

Main Results:

• A spinodal structure with narrowed periodic distance (<70 nm) and ~60% porosity was successfully attained.
• Al2O3 addition decreased interfacial energy, promoting smaller periodic distances and faster silica skeleton formation.
• The two-step process increased the borate-rich phase fraction and structure growth.

Conclusions:

• The developed two-step phase separation method effectively controls spinodal structure formation in the Na2O-B2O3-SiO2 system.
• Al2O3 is a critical additive for refining periodic distances and accelerating the formation of durable silica skeletons.
• The study provides a framework for designing glasses with specific microstructures and properties.