Role of particles size on the cohesive strength of non-sintered (green) ceramics

TL;DR

This study investigates how particle size influences the mechanical strength of non-sintered ceramic foams, revealing that smaller particles significantly enhance strength and proposing a new theoretical model based on van der Waals forces.

Contribution

It introduces a novel theoretical expression to predict the strength of green ceramics based on particle size and van der Waals interactions, supported by experimental data.

Findings

Smaller particles lead to much higher mechanical strength.

The strength of green ceramics can approach that of sintered materials.

A new theoretical model accurately predicts the strength based on particle interactions.

Abstract

Preparation of particle-loaded foams, followed by drying, sintering and/or cross-linking are widely explored routes for developing lightweight ceramics with high mechanical strength. The non-sintered dry ceramic foams are less studied due to their intricate production and the assumed poor mechanical strength of the obtained "green" materials. Here we produce lightweight ceramics from foamed particle suspensions containing spherical silica particles with radii varied between 4.5 nm and 7 {\mu}m. The wet foams were prepared in the presence of cationic surfactant and were dried at ambient conditions to obtain porous materials with mass densities between 100 and 700 kg/m3. The materials containing smaller particles exhibited much higher strength (up to 2000 times), approaching that of the sintered materials. A new theoretical expression for predicting the mechanical strength of such materials was derived and was used to explain the measured strengths of the produced materials through the van der Waals attractions between the particles in the final dry materials.