In situ observation of the multistep process of cold sintering

A compact cold sintering stage was constructed to densify ceramic samples in capillary tubes for the purpose of conducting in situ experiments designed to elucidate fundamental cold sintering mechanisms. The stage was used to successfully densify samples composed of ZnO/CH3COOH mixtures under a range of pressures (25-175 MPa) over a modest temperature range (room to 150 degrees C) in capillary tubes (0.75 mm inner diameter). The progression of the cold sintering process of ZnO was monitored by both piston displacement and a camera. These measurements allowed the strain rate and fluid extraction during densification to be recorded. The results of these measurements are compared to existing models of cold sintering and pressure solution creep, and direct correlations are observed between abrupt changes to the densification rate during constant heating rate experiments and the observation of solvent extraction from the powder compact.