Chemothermal pulverization: Crushing titanate crystals to obtain nanosized powders via high‐temperature treatment

Abstract

In this study, we investigated chemothermal pulverization (CTP) phenomena that are induced in titanate single crystals and ceramics by high-temperature treatment at approximately 1000°C under reactive gas containing ammonia and oxygen and cause these materials to break down into nanosized powders. Structural characterization revealed that there were many nanosized voids formed in titanates during heat treatment for CTP, and subsequent analysis revealed that these voids were filled with nitrogen gas. These results indicated that CTP consisted of four steps: the in-diffusion of nitride ions from the surface to titanates, the deposition of nitrogen molecules (gas) inside the titanate crystals instead of nitride formation, the growth of voids by further nitrogen transport from the surface to voids, and, finally, the breakdown of the walls between voids to form nanopowders. Furthermore, we discussed the exact mechanism of CTP phenomena by examining the effect of doping into titanates on the progress of CTP and by conducting theoretical calculations for the simulation of nitrogen impurities in titanate lattices.

Challenges and Strategies for Synthesizing High Performance Micro and Nanoscale High Entropy Oxide Materials

“…[67,68] In the "top-down" approach, like solidphase synthesis, high temperatures and extended reaction times are required, necessitating additional processes such as milling bulk HEO materials into nano powders. [69,70] Conversely, the "bottom-up" method, involving atomic-level mixing of precursors, is more suitable for HEO MNMs preparation. This method allows for milder conditions.…”