Advanced Materials Research Vol. 412

Abstract: Compound ceramic coatings with the main crystal phase of Al₂TiO₅ (as-coated samples) were prepared in situ on the surface of Ti-6Al-4V alloy by means of pulsed bi-polar micro-arc oxidation (MAO) in an NaAlO₂ solution. The coated samples were calcined in argon and air at 1000°C, respectively. The phase composition, surface and section morphology, and element contents of the ceramic coatings were investigated by X-ray diffractometry (XRD), Scanning electron microscopy (SEM) and X-ray fluorescence spectroscopy (XRF). The samples were treated in argon and the as-coated ones were calcined in air at 1000°C to study the anti-oxidation properties of the samples. The results show that Al₂TiO₅ had been decomposed in an hour and transformed into α-Al₂O₃ and rutile TiO₂ in air. However, Al₂TiO₅ had been decomposed in four hours in argon and the final coating surface was completely composed of α-Al₂O₃. The content of Al₂O₃ was decreased from outside to inside layers and Ti₂O₃ was formed in the coating. Furthermore, the morphology of the ceramic coatings after the calcination was different. The coatings calcined in argon were finer; the grains and pores were smaller than those in air.

Abstract: BaTiO₃ ceramic composite powders were prepared by a gel-solid reaction method using the raw materials of two particle sizes, DSC was used to study the thermal decomposition of the green body. The effect of the calcination temperatures on the phase structure of the powders was investigated. The influence of the particle sizes of the raw materials on the reaction temperature and the microstructure of the powders was explored. The results showed that reaction temperature of BaTiO₃ ceramic powders reacted from BaCO₃ of the large size was about 933.0°C, and the one from BaCO₃ of the smaller size was about 903.5°C, respectively. XRD results indicated that BaTiO₃ powders could be prepared at a temperature range of 900°C ~ 1000°C using the raw materials of either size. The particle size of the synthesized powders was determined by the particle size of the raw material. Therefore, the raw materials of small size should be chosen to prepare the synthesized powders of small size, and at a lower reaction temperature.