Executive Summary : | Diffusion bonding of ceramics requires prolonged exposure to high temperatures, causing grain growth. Low melting bonding materials like glass or other compounds have limitations in terms of temperature and loading. Flash sintering is a non-conventional field-assisted technique that can be used for the joining of ceramics like YSZ and alumina at lower temperatures. The flash event is characterized by a non-linear increase in conductivity above a threshold applied field, resulting in thermal runaway and accelerated diffusion/mass transport. Flash can be used for the joining of ceramics such as YSZ and alumina, but the specific mechanism of joining is not known. Lower oxygen partial pressures tend to lower the flash onset temperature, but it results in lower densification of oxide materials by promoting pore formation due to vacancy accumulation. Applying sufficient pressure can retard pore formation and increase the processing time-temperature domain for achieving high strength joints. This proposal proposes developing a relatively inexpensive pressure-assisted flash joining process for YSZ and alumina ceramics. A universal testing machine equipped with a high-temperature furnace will be used for this process. Pre-sintered bar specimens will be loaded under uniaxial compression, and platinum/Inconel electrodes will be used to apply an electric field. The setup will be equipped with an optical pyrometer and a high-speed camera to monitor temperature and shrinkage/deformation close to the joint. |