纳米Al_2O_3-13％TiO_2粉末及其等离子喷涂涂层的相变

将商用纳米Al_2O_3与TiO_2粉末混合制浆，通过喷雾造粒技术重构成大颗粒纳米Al_2O_3-13％T102团聚粉体，然后采用不同加热温度进行烧结，制备用于热喷涂的纳米喂料。采用等离子喷涂技术沉积形成纳米涂层。利用XRD和SEM对纳米粉末和涂层的形貌、显微结构和晶相进行表征。结果表明，在烧结过程中纳米氧化铝没有发生相变，而纳米氧化钛则由锐钛矿相转变为金红石相；在等离子喷涂过程中，部分a—Al_2O_3发生熔化转变为y—Al_2O_3，且转变量与喷涂工艺参数有关；而TiO_2相只在较低喷涂工艺参数下存在衍射峰，在较高喷涂工艺参数下则以z—A1203＂Ti02固溶体存在；涂层在热处理过程中会发生y．A1203向a—A1203的转变，且有Ti02相析出。

Phase evolution of plasma sprayed Al2O3-13%TiO2 coatings derived from nanocrystalline powders

Commercial nanosized alumina and titania particles were selected as raw materials to prepare the blended slurry with composition of A1203-13%TiO2 （mass fraction）, which were reconstituted into micrometer-sized granules by spray drying, subsequently sintering at different temperatures to form nanostructured feedstock for thermal spraying, and then A1203-13%TiO2 nanocoatings were deposited by plasma spraying. The evolution of morphology, microstructure, and phase transformation of the agglomerated powder and as-sprayed coatings were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results show that A1203 retains the same a phase as the raw material during sintering, while TiO2 changes from anatase to futile. During plasma spraying, some a-A1203 phases solidify to form metastable y-A1203, and the volume fraction of a-A1203 decreases as CPSP increases. However, peaks of the TiO2 phase are not observed from the as-sprayed coatings except for the coatings sprayed at the lower CPSP. As the CPSP increases, nanostructured TiO2 is dissolved easily in y-A1203 or z-A1203＇TiO2 phase. After heat treatment, y-A1203 in the coatings transforms to a-A1203, and rutile is precipitated.