Hypoeutectic and hypereutectic Al2O3-ZrO2 multiphase ceramics-lined composite pipes were produced by using the gravita-tional separation self-propagate high-temperature synthesis (SHS) process. The microstructure of t...Hypoeutectic and hypereutectic Al2O3-ZrO2 multiphase ceramics-lined composite pipes were produced by using the gravita-tional separation self-propagate high-temperature synthesis (SHS) process. The microstructure of the ceramics was observed by meansof SEM and EPMA. The fracture toughness of the multiphase ceramics was tested by using the Vickers indentation method. Thefracture toughness of hypoeutectic Al2O3-ZrO2 multiphase ceramics is 15.96 MPa·m1/2 and that of hypoeutectic Al2O3-ZrO2 multiphaseceramics is 15.23 MPa·m1/2. The toughening mechanisms were systematically investigated by means of SEM and XRD. The resultsshow that the bridging toughening mechanism, stress induced ZrO2 transformation toughening mechanism, and microcrack tougheningmechanism are the predominant toughening mechanism.展开更多
The artificial neural networks (ANN) which have broad application were proposed to develop multiphase ceramic cutting tool materials. Based on the back propagation algorithm of the forward multilayer perceptron, the m...The artificial neural networks (ANN) which have broad application were proposed to develop multiphase ceramic cutting tool materials. Based on the back propagation algorithm of the forward multilayer perceptron, the models to predict volume content of composition in particle reinforced ceramics are established. The Al2O3/TiN ceramic cutting tool material was developed by ANN, whose mechanical properties fully satisfy the cutting requirements.展开更多
Utilizing self-propagating high-temperature synthesis(SHS) reactive spraying technology,the feeding self-combustion agglomerated particles composed of Ti,B4C and C powders,TiC-TiB2 multi-phase ceramic coatings were pr...Utilizing self-propagating high-temperature synthesis(SHS) reactive spraying technology,the feeding self-combustion agglomerated particles composed of Ti,B4C and C powders,TiC-TiB2 multi-phase ceramic coatings were prepared on the steel substrates. Orthogonal experiment was carried out to optimize the spraying parameters. The phase component and microstructure of the coating fabricated at the optimized parameters were studied by XRD and SEM. The reactive mechanism in flying agglomerated particles was discussed. The optimized conditions,spraying distance of 220 mm,powders delivering gas pressure of 0.3 MPa and preheating temperature of 240 ℃ to sprayed particles,were obtained from orthogonal experiment. For the coating,porosity of 2.5% and HV 1 595 are achieved under the optimized parameters. The coatings are mainly composed of TiC0.3N0.7,TiB2 and a little TiO2. The SEM analysis shows the morphology of TiC0.3N0.7 matrix in which the fine granular TiB2 crystals evenly disperse. It is concluded that,as solo reactive units,the agglomerated particles would finally form into the coatings after going through four successive stages in the flame,which are,respectively,pregnant reaction,flight combustion,collision and structure transformation and solidification. The solid diffusion and dissolution-precipitation are the two mechanisms to control the synthesis reaction.展开更多
TiO2/（O′+β′）-Sialon multiphase ceramics were prepared with nano TiO2 （anatase） powder and （O′+β′）-Sialon powder as raw materials. Effect of Yb2O3 additive on transformation behavior of anatase for TiO2/（O...TiO2/（O′+β′）-Sialon multiphase ceramics were prepared with nano TiO2 （anatase） powder and （O′+β′）-Sialon powder as raw materials. Effect of Yb2O3 additive on transformation behavior of anatase for TiO2/（O′+β′）-Sialon multi phase ceramic was investigated and its influence mechanism was discussed. XRD was employed for the analysis of phase composition and lattice parameters. The results show that even though Yb2O3 has no obvious influence on starting temperature of phase transformation, it significantly accelerates the transformation process, which displays a weakened effect with more Yb2O3 addition. There exist two forms of the added Yb2O3: some enters TiO2 lattice and the other deposits on the surface of TiO2. The function of Yb2O3 on phase transformation of anatase can be attributed to the coaction of active and negative influence mechanisms as follows: some Yb n+ enter TiO2 lattice and replace Ti 4+ , as well as the redox reaction between Yb 3+ and TiO2, which promote the transformation, whereas other Yb2O3 deposits on the surface of TiO2, and Ti-O-Yb bond is formed by the coaction of Yb 3+ and TiO2, which inhibit the process.展开更多
The thermal shock resistance and anti-aluminum erosion of TiB2-BN multiphase ceramics composites were studied. The experimental results show that the TiB2-BN multiphase ceramic possesses a good thermal shock resistanc...The thermal shock resistance and anti-aluminum erosion of TiB2-BN multiphase ceramics composites were studied. The experimental results show that the TiB2-BN multiphase ceramic possesses a good thermal shock resistance at high temperatures （1000,1200,1400,1500 ℃）, with the increasing in thermal shocking temperature, the electro-conductivity of TiB2-BN ceramics increases. The metal aluminum has a great influence on the properties of TiB2-BN ceramics and the main reason is that the aluminum reacts seriously with BN. It is suggested that the content of BN should be reduced to the greatest extent.展开更多
The isothermal oxidation behavior and mechanism of the TiC-TiB2 multiphase ceramics fabricated by self-propagating high temperature synthesis were studied.The result shows that the oxidation kinetics agrees to the par...The isothermal oxidation behavior and mechanism of the TiC-TiB2 multiphase ceramics fabricated by self-propagating high temperature synthesis were studied.The result shows that the oxidation kinetics agrees to the parabolic rule within the temperature rang of RT to 1000℃. First at 600℃ TiB2 was oxidized to be TiO2. Then both TiB2 and TiC were oxidized to be TiO2 when temperature increased to 1000℃. A compact TiO2 film, the oxidation product, formed on the sample surface, which prevented further oxidation and resulted in a very high oxidation resistance of the sample.展开更多
文摘Hypoeutectic and hypereutectic Al2O3-ZrO2 multiphase ceramics-lined composite pipes were produced by using the gravita-tional separation self-propagate high-temperature synthesis (SHS) process. The microstructure of the ceramics was observed by meansof SEM and EPMA. The fracture toughness of the multiphase ceramics was tested by using the Vickers indentation method. Thefracture toughness of hypoeutectic Al2O3-ZrO2 multiphase ceramics is 15.96 MPa·m1/2 and that of hypoeutectic Al2O3-ZrO2 multiphaseceramics is 15.23 MPa·m1/2. The toughening mechanisms were systematically investigated by means of SEM and XRD. The resultsshow that the bridging toughening mechanism, stress induced ZrO2 transformation toughening mechanism, and microcrack tougheningmechanism are the predominant toughening mechanism.
文摘The artificial neural networks (ANN) which have broad application were proposed to develop multiphase ceramic cutting tool materials. Based on the back propagation algorithm of the forward multilayer perceptron, the models to predict volume content of composition in particle reinforced ceramics are established. The Al2O3/TiN ceramic cutting tool material was developed by ANN, whose mechanical properties fully satisfy the cutting requirements.
基金Project (50672130) supported by the National Natural Science Foundation of China
文摘Utilizing self-propagating high-temperature synthesis(SHS) reactive spraying technology,the feeding self-combustion agglomerated particles composed of Ti,B4C and C powders,TiC-TiB2 multi-phase ceramic coatings were prepared on the steel substrates. Orthogonal experiment was carried out to optimize the spraying parameters. The phase component and microstructure of the coating fabricated at the optimized parameters were studied by XRD and SEM. The reactive mechanism in flying agglomerated particles was discussed. The optimized conditions,spraying distance of 220 mm,powders delivering gas pressure of 0.3 MPa and preheating temperature of 240 ℃ to sprayed particles,were obtained from orthogonal experiment. For the coating,porosity of 2.5% and HV 1 595 are achieved under the optimized parameters. The coatings are mainly composed of TiC0.3N0.7,TiB2 and a little TiO2. The SEM analysis shows the morphology of TiC0.3N0.7 matrix in which the fine granular TiB2 crystals evenly disperse. It is concluded that,as solo reactive units,the agglomerated particles would finally form into the coatings after going through four successive stages in the flame,which are,respectively,pregnant reaction,flight combustion,collision and structure transformation and solidification. The solid diffusion and dissolution-precipitation are the two mechanisms to control the synthesis reaction.
文摘TiO2/（O′+β′）-Sialon multiphase ceramics were prepared with nano TiO2 （anatase） powder and （O′+β′）-Sialon powder as raw materials. Effect of Yb2O3 additive on transformation behavior of anatase for TiO2/（O′+β′）-Sialon multi phase ceramic was investigated and its influence mechanism was discussed. XRD was employed for the analysis of phase composition and lattice parameters. The results show that even though Yb2O3 has no obvious influence on starting temperature of phase transformation, it significantly accelerates the transformation process, which displays a weakened effect with more Yb2O3 addition. There exist two forms of the added Yb2O3: some enters TiO2 lattice and the other deposits on the surface of TiO2. The function of Yb2O3 on phase transformation of anatase can be attributed to the coaction of active and negative influence mechanisms as follows: some Yb n+ enter TiO2 lattice and replace Ti 4+ , as well as the redox reaction between Yb 3+ and TiO2, which promote the transformation, whereas other Yb2O3 deposits on the surface of TiO2, and Ti-O-Yb bond is formed by the coaction of Yb 3+ and TiO2, which inhibit the process.
基金Funded by the National Natural Science Foundation of China(No.50372047)
文摘The thermal shock resistance and anti-aluminum erosion of TiB2-BN multiphase ceramics composites were studied. The experimental results show that the TiB2-BN multiphase ceramic possesses a good thermal shock resistance at high temperatures （1000,1200,1400,1500 ℃）, with the increasing in thermal shocking temperature, the electro-conductivity of TiB2-BN ceramics increases. The metal aluminum has a great influence on the properties of TiB2-BN ceramics and the main reason is that the aluminum reacts seriously with BN. It is suggested that the content of BN should be reduced to the greatest extent.
文摘The isothermal oxidation behavior and mechanism of the TiC-TiB2 multiphase ceramics fabricated by self-propagating high temperature synthesis were studied.The result shows that the oxidation kinetics agrees to the parabolic rule within the temperature rang of RT to 1000℃. First at 600℃ TiB2 was oxidized to be TiO2. Then both TiB2 and TiC were oxidized to be TiO2 when temperature increased to 1000℃. A compact TiO2 film, the oxidation product, formed on the sample surface, which prevented further oxidation and resulted in a very high oxidation resistance of the sample.
