Synthesis and sintering of refractory calcium zirconate for high temperature applications in contact with titanium and titanium alloys

Abstract

The publication provides general information about CaZrCh, discusses synthesis methods and main application areas. Based on the analysis of sources, it was found that the least expensive and easiest technique is solid-phase synthesis from natural carbonate powder and zirconium dioxide. The morphology of powders of micromarble brand KM-2, monoclinic zirconium dioxide brand CrO-1 and calcium metazirconate of domestic production is investigated. To determine the temperature of calcium zirconate synthesis from the initial powders of zirconium dioxide and calcium carbonate, a differential thermal analysis was used. The temperature of the chemical compound formation is approximately 1230 oC. Calcination of a mixture of initial powders was carried out at temperatures of 1100, 1200, 1300 and 1400 oC. X-ray phase and microscopic analysis of the obtained powders was conducted. It is established that at a temperature of 1100 oC solid-phase synthesis does not occur, at 1200 oC it does not pass completely, at 1300 oC and 1400 oC it is fully completed. However, the powder synthesized at 1400 oC is dense aggregated, the destruction of which requires mechanical action. And the powder synthesized at 1300 oC consists of friable particles that can be easily desegregated and is sinter active. A comparison between cera mics obtained from synthesized powder and from calcium meta zirconate of domestic production was carried out. The material made of the synthesized powder has a denser structure and greater strength. The crucible from the synthesized powder was successfully tested under vacuum heating conditions to a temperature of 1600 oC in contact with of Ti – Ni – Hf and Ti – Zr – Nb preforms.