Non-firing solidification: A new room temperature ceramics processing
Hadi Razavi‐Khosroshahi, Tomohiro Sato, Masayoshi Fuji
Abstract
Low-temperature sintering has been long desired by many ceramists and materials scientist because sintering is a high-cost and time-consuming process. High temperature sintering is also attempted to be avoided because it may alter the microstructure of ceramics by causing an undesired grain growth or changing the chemical stoichiometry of the final product. This perspective aims to give an insight into a new concept of the powder solidification process, named as the “non-firing solidification process”. The main concept of the non-firing solidification process is to activate the surface of particles by mechanical milling and consolidate the particles via the joining of activated surfaces. This method, which is mainly conducted at room temperature, can be applied for a wide range of materials including oxides and nonoxides. SiO2 (silica) is taken as a model and radical centers before and after surface activation are studied by electron paramagnetic resonance (EPR). The amount of water adsorption on the surface of silica during the process is also observed as an index of the activation. A molecular dynamics (MD) simulation model of β-tridymite silica whose surface is terminated with OH is applied in order to investigate the effect of mechanochemical activation on the surface of particles. The particle-particle bonding, as well as triple junctions and necking between particles are confirmed by transmission electron microscopy.