High-Performance Ceramics III

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Authors: Ai Bing Yu, L.J. Zhong, Xin Li Tian, F. Zou
Abstract: A new method is proposed for machinability evaluation of machinable ceramic materials. The relation of machinability attributes is modeled as a digraph, and machinability attribute matrix is defined. Machinability indexes are calculated with permanent function of the matrix, and machinabilities of machinable ceramics are ranked. Five composites consisting of CePO4 and zirconia were fabricated, measured and drilled with tungsten-cobalt carbide bits. Mechanical property parameters of Ce-ZrO2/CePO4 composites, including Vickers hardness, fracture toughness and Elastic modulus, are selected as machinability attributes. The experimental results of material removal rates are consistent with the ranking of machinability index values of Ce-ZrO2/CePO4 ceramics. The machinabilities of Ce-ZrO2/CePO4 ceramics improve with the increase of CePO4 proportions. Machinability of machinable ceramics can be evaluated with digraph method.
Authors: L.J. Ma, Ai Bing Yu, Yan Fei Tan
Abstract: Machinable ZrO2/CePO4 composite was fabricated. ZrO2/CePO4 and mild steel materials were machined with tungsten-cobalt carbide twist drills. The material removal characteristic was analyzed by consideration of tool wear in different stock removals. Wear of twist drills was observed with SEM. Wear widths on major flank were measured with microscope. The experimental results show when ZrO2/CePO4 was drilled, wear widths on flank were much bigger comparing to mild steel drilling processes. The wear of twist drills occurred on major flank, minor flank and on chisel edge. Wear on minor flank is a unique characteristic in drilling of ZrO2/CePO4 ceramics. There exist obvious scratch remarks on tool wear. The tool wear results from abrasive wear, adhesive wear and oxidation wear.
Authors: Jiang Min, Jia Chen Liu, Hai Yan Du, Yi Rong Liu, Zhi Jun Cao
Abstract: Some useful characteristics, including strength, toughness, damage of machining, and propagation pattern of indentation cracks, were studied based on machinable 30 wt%LaPO4/ Al2O3 composites. Corresponding characteristics for Al2O3 ceramic were also concerned for comparing. The results supplied some elementary information for both use and further study of LaPO4/ Al2O3 composites.
Authors: Yan Luting, Si Wenjie, Xiong Tao, Miao Hezhuo
Abstract: The ceramic injection molding feedstock of Al2O3-SiC nanocomposite were prepared and studied in detail. Three ways of surface modification including surfactant pre-coating, surface emulsion polymerization and surface low temperature plasma polymerization were used to modify the surface of SiC powders in order to reduce the agglomeration, improve the dispersion and the compatibility with organic media. CIM feedstock with different SiC content and solid loading were prepared through mixing surface modified SiC powders with Al2O3 powders and organic binders. The effect of three ways of surface modification on the viscosity of CIM feedstock were studied and the way of surface emulsion polymerization developed the best action in increasing dispersion, reducing viscosity and improving the solid loading of CIM feedstock.
Authors: Zhen Zhen Peng, Shu Cai, Yan Wei Wang, Hou Zheng Wu
Abstract: Many significant improvements have been shown in mechanical properties of ceramic nanocomposites with ceramic matrix being dispersed with second sub-micro sized (or nano-sized) phase. This study designed and fabricated Al2O3/SiC nanocomposites with a raw material used for 85% alumina as matrix and SiC grits in submicro-scale as dispersion phase via a controlled pressureless sintering in air. With coarse SiC powder as bed powder, both C and SiC powder making deoxidized atmosphere, 85Al2O3/SiC nanocomposites with different SiC contents were densified by pressureless sintering at low temperature. Fracture surface investigation indicated that dense nanocomposites with small grain size were produced. General material properties and microstructure were measured and characterized. The results showed that composites sintered in deoxidized atmosphere had better mechanical properties than those sintered in flowing argon.
Authors: Hong Jun Huang, Hong Jing Wan
Abstract: In this paper, the SHS process using TiO2, Al and graphite powders has been performed successfully. The TiO2 : Al : C molar ratio was 3 : 4.2 : 2.8. XRD result shows the final product powder is Al2O3-TiC composite powder. The morphology and microstructure of the composite powder was also investigated.
Authors: Sidi Gu, Zhao Qiang Zeng
Abstract: Al2O3/Ni composite ceramics toughened by metallic particles was fabricated by the vacuum reduction of Al2O3 and nickel nitrate (Ni(NO3)2•6H2O) mixed powders at 800-1000° for 2-4h and hot pressed at 1400° ~ 1500°C for 1-2h. Three-point bending strength and facture toughness of the composite were studied. With the increase of Ni content, its flexural strength and facture toughness increases significantly. Microstuctural investigations of the composite revealed that fine nickel particles dispersed homogeneously at the matrix grain boundaries, forming the intergranular nanocomposite.
Authors: Zheng Guang Zou, Jin Li Li, Yi Wu
Abstract: In the paper, natural ilmenite (FeTiO3) was used as the main green material to synthesize TiC-Al2O3/Fe composite powder by Self-propagating High-temperature Synthesis (SHS) technology and densified TiC-Al2O3/Fe composites were prepared in a vacuum hot-pressoven. The reaction mechanism in the synthesis process was studied through theoretical thermodynamical analysis and experiment research .The effect of different synthesis conditions on the products was discussed. The relations among synthesis conditions,sintering conditions, phases composition, microstructure and properties of composites were also studied in details. A new way to synthesize the advanced TiC-Al2O3/Fe composites with relatively lower cost was practiced.
Authors: Qin Fang Yan, Zheng Ren Huang, Shao Ming Dong, Dong Liang Jiang
Authors: Jian Jiang Wang, Xin Kang Du, Hong Wei Liu, Jun Yan
Abstract: Based on SHS reactive flame spray technology, Al2O3 multiphase ceramics coatings were produced. Chemical copper-plating technology was used to produce the Al-CuO powders of copper cladding, which became individual SHS reactive units respectively. The phenomena and principles of the SHS reactive flame spray of the Al-CuO powders of copper cladding forming Al2O3 multiphase ceramics coatings were investigated. It was found that copper cladding of Al-CuO powders were necessary for the SHS reaction during the spray process. The better the cladding was, the more sufficient the SHS reaction, and the higher the transformation rate was. The Cu and Al2O3 fine molten drops produced by the SHS reaction bumped the substrate and flatted to form layer-shaped Al2O3-based multiphase ceramics coatings. The binding strength between the coating and substrate was as high as 19.8MPa, and the micro-hardness of the coatings was Hv712. The overall properties of the coatings were better than those of the ceramics coatings sprayed by the traditional flame spray.

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