Formation Mechanism of High Thermal Resistance Oxide Eutectic Film Prepared by High Speed Solidification Process | Chapter 4 | Current Innovations in Chemical and Materials Sciences Vol. 2

 This phase summarized the authors' efforts in evolving a process for the fabrication of very heat-resistant oxide eutectic films for Al2O3/HfO2 and CaZrO3/ZrO2 eutectic scheme with fine microstructures. In these processes, light fixating floating zone appliance and/or high-power ray of light equipment were used. Formation system of the oxide eutectic films and their characteristics were described. Solidified Al2O3/HfO2 eutectic film was prepared utilizing optical district melting method on the silicon carbide substrate. At extreme temperatures, a tiny amount of silicon carbide decomposed into silicon and carbon. The elements of Al2O3 and HfO2 in molten point also react accompanying the free carbon on silicon carbide substrate. The Al2O3 state reacts with free carbon and mist specie of AlO point is formed. The composition of the melted phase enhances HfO2 rich from the eutectic composition and HfO2 phase hardens as primary phase on the substrate. The hardened HfO2 phase further reacts with the free carbon and HfC chapter is formed, before a high-density in-between layer was made on the surface of silicon carbide substrate. The adhesion middle from two points the intermediate tier and the substrate is excellent by an anchor effect and chemical sticking. When the solidification process done before all of solidified HfO2 primary point is reduced to HfC development, HfC-HfO2 functionally graded layer is made on the silicon carbide substrate and the Al2O3/HfO2 eutectic structure evolve from the top of the intermediate tier. As the intermediate tier is formed by the related series of events between the group of chemical elements melt and the silicon carbide substrate, the thickness of the middle layer cut down with increasing the speed of the transfer velocity of the molten district. On the other hand, the authors' experiments showed that development separation from ZrO2 results in the formation of a fine CaZrO3/ZrO2 eutectic construction even during accelerated solidification. When CaZrO3/ZrO2 eutectic was formed on a ZrO2 substrate for one same combination method as above, it was found that when the transfer velocity beneath 3000 mm/h, the 200 peak for cubic ZrO2 phase powerfully oriented. At fast transfer velocity of the melting district, rapid thickening from supercooling melt occurs. In specific cases, crystals evolve in the (100) direction. Rapid crystal development results in the formation of various peculiar film structures. Columnar crystal, cauliflower-like columnar crystal and eutectic microstructures filling the gaps in the tubular crystals are the main microstructures.

Author(s) Details:

Shunkichi Ueno,
College of Engineering, Nihon University, Koriyama, Fukushima 963-8642, Japan.

Please see the link here: https://stm.bookpi.org/CICMS-V2/article/view/12326