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Al 2 O 3 -TiO 2 nanocomposite powders with or without nano-additives used for plasma spraying were successfully prepared by spray drying, heat treatment and plasma treatment. The effects of treatment process and nano-additives on the microstructure and properties of Al 2 O 3 -TiO 2 nanocomposite powders were investigated. Al 2 O 3 -TiO 2 composite powders prepared by spray drying and heat treatment were nanostructured composite powders with high sphericity and nanosized grains. Spherical and dense particles with smooth surface were formed due to the extremely rapid liquid phase sintering during plasma treatment. The formation of different microstructures after plasma treatment was mainly determined by two key factors: the density and heating temperature of powder particles. The three-dimensional network structure was the typical microstructure in the plasma treated Al 2 O 3 -TiO 2 composite powder with nano-additives. The nanocomposite powder with three-dimensional network structure was composed of amorphous intergranular network thin film rich in Ti, Zr and Ce surrounding the α-Al 2 O 3 colonies. Spherical powders with smooth surface and dense microstructure were formed due to the rapid melting and solidifying of plasma treatment. Therefore, the flowability and density of the plasma treated powders was significantly improved. The plasma treated composite powders were good spraying material with excellent performance, which can be used to prepare high performance nanostructured coatings. [ABSTRACT FROM AUTHOR]

The Al 2 O 3 -Y 2 O 3 system composite coatings were prepared by plasma spraying Al 2 O 3 -Y 2 O 3 composite powders with or without TiO 2 addition. The effects of TiO 2 on the microstructure and properties of the Al 2 O 3 -Y 2 O 3 coatings were investigated. The results show that the composition of the composite powders had great influence on their microstructure evolution. The Al 2 O 3 -Y 2 O 3 coatings were composed mainly of α-Al 2 O 3 and c-Y 2 O 3 . There were amorphous phase, Y 3 Al 5 O 12 (YAG) phase and Y 4 Al 2 O 9 (YAM) phase formed in the Al 2 O 3 -Y 2 O 3 coating. The content of Y 3 Al 5 O 12 in the Al 2 O 3 -Y 2 O 3 -TiO 2 coating increased with addition of 2 wt% TiO 2 , and the content of Y 4 Al 2 O 9 and amorphous phases decreased correspondingly. There was no Y 3 Al 5 O 12 formed in the Al 2 O 3 -Y 2 O 3 -TiO 2 coatings with further increasing of TiO 2 , while the content of amorphous phase increased. The microhardness of the Al 2 O 3 -Y 2 O 3 -TiO 2 coating was improved with the addition of 2 wt% TiO 2 , which was attributed to its lower porosity, more uniform microstructure, more YAG phase, and less amorphous phase. The microhardness of the Al 2 O 3 -Y 2 O 3 -TiO 2 coatings decreased significantly with further increasing of TiO 2 due to the significant decrease of YAG phase and the increase of the amorphous phase. The Al 2 O 3 -Y 2 O 3 -TiO 2 coating with addition of 2 wt% TiO 2 possessed higher toughness, adhesive strength and wear resistance compared with the Al 2 O 3 -Y 2 O 3 coating, which was due to its lower porosity, smaller and spherical pores, and more YAG phase. [ABSTRACT FROM AUTHOR]

Abstract: BaFe12O19 nanowire arrays having single magnetic domain size (≤460nm) in anodic aluminum oxide (AAO) templates were prepared by sol–gel and self-propagating high-temperature synthesis techniques. The diameter of the nanowire arrays is approximately 70nm and the length is about 2–4μm. The specimens were characterized using X-ray diffraction, vibrating sample magnetometer, field emission scan electron microscope, atomic force microscopy and microwave vector network analyzer. The magnetic properties of BaFe12O19 nanowire arrays embedded in AAO templates were measured by VSM with a field up to 1274KA/m at room temperature. The results indicate that the nanowire arrays exhibit large saturation magnetization and high coercivity in the range of 6000Oe and an obvious magnetic anisotropy with the easy magnetizing axis along the length of the nanowire arrays, probably due to the shape anisotropy and magneto-crystalline anisotropy. Finally the microwave absorption properties of the nanowires were discussed. [Copyright &y& Elsevier]