A New Process and Structure of Al2O3/LaPO4 Composites
LaPO4 was added to Al2O3 ceramic matrix to improve the machinability of the composites. Different from the traditional way of making Al2O3/LaPO4 composite, coating method is introduced. In the present work, LaPO4-coated α-Al2O3 powders were synthesized through the heterogeneous precipitation method and sintered into Al2O3/LaPO4 composites by pressureless sintering at 1600°C for 2h. The phase components and microstructure of Al2O3/LaPO4 composites are presented according to variations of lanthanum phosphate (LaPO4) content (10 wt.%, 20 wt.%, 30 wt.%, 40 wt.%). From the TEM image, it can be seen that the coated powders have a clear core-shell structure and the thickness of the coating varies from 5 to 15 nm approximately. X-ray diffraction analysis showed that only Al2O3 and LaPO4 phases exist in the Al2O3/LaPO4 composites which indicated that there is good chemical compatibility between Al2O3 and LaPO4 phase. Microstructure development of Al2O3/LaPO4 composites has been explored by SEM, the coating structure became less recognized after sintering, layered and fiber shaped LaPO4 was obviously observed in the Al2O3/LaPO4 composites with the increase of LaPO4 addition. The LaPO4 inhibited grain growth of Al2O3 by distributing at the Al2O3 grain boundaries. The weak interface of Al2O3/LaPO4 and layered soft LaPO4 phase can be responsible for the machinability of the composites.
Yansheng Yin and Xin Wang
Q. J. Zheng et al., "A New Process and Structure of Al2O3/LaPO4 Composites", Advanced Materials Research, Vols. 79-82, pp. 2227-2230, 2009