A new method for corrosion protection of Al-based metal matrix composites (MMC) was developed using two-step process, which involves anodizing in H2SO4 solution and sealing in rare earth solution. Corrosion resistance...A new method for corrosion protection of Al-based metal matrix composites (MMC) was developed using two-step process, which involves anodizing in H2SO4 solution and sealing in rare earth solution. Corrosion resistance of the treated surface was evaluated with polarization curves. The results showed that the effect of the protection using rare earth sealing is equivalent to that using chromate sealing for Al6061/SiCp. The rare earth metal salt can be an alternative to the toxic chromate for sealing anodized Al MMC.展开更多
The effects of positron diffusion on the measured S parameter have been investigated by a point-source diffusion model and a δ function method. Firstly, the theoretical analyses of the effects are presented for the s...The effects of positron diffusion on the measured S parameter have been investigated by a point-source diffusion model and a δ function method. Firstly, the theoretical analyses of the effects are presented for the samples of a homogeneous semi-infinite medium and a film of definite thickness. Then the results are used to analyze the S parameters in several composite systems and interface models.展开更多
We perform synthesis, characterization, and application of nanostructured diamond composites. The enhancements of the thermomechanical performance of bulk diamond compacts in terms of hardness, fracture toughness, wea...We perform synthesis, characterization, and application of nanostructured diamond composites. The enhancements of the thermomechanical performance of bulk diamond compacts in terms of hardness, fracture toughness, wear resistance, impact strength, and thermal stability are our project objectives. It is to aim at applying an advanced nanosynthesis process for the manufac-turing of superhard and ultratough diamond/SiC nanocomposites with the implementation of nanofiber reinforcement. The R&D re-sults can be used in multi-industrial applications, particularly, for drill bits designed to encounter dynamic impacts for high speed oil/gas drillings, thus to achieve high efficiency and energy saving. Science and technology (S&T) researches on precursors, cata-lyst, reactive sintering, and in-situ/real-time characterization of high P-T neutron/X-ray diffraction studies on phase stability, syn-thesis kinetics, residual strain, and yield strength have been applied to help optimizing the nanomanufacturing process. Our R&D ef-fort in high P-T nanosynthesis of TSP diamond/SiC composites is to achieve superior performance of nanomechanics in resisting dy-namic impact and thermal degradation, while still maintaining the super-hardness and super-abrasiveness of diamond and silicon-car-bide. The improved polycrystalline diamond compact (PDC) bit inserts for drilling, boring, and cutting will be applied in harsh envi-ronments so as to meet the demands of the mining, petroleum, and machinery industries. With success of the proposed project, the expected energy savings and reduction of CO2 emission will be significant and the economic advantages are going to be enormous.展开更多
Mechanical properties of alumina-fluorapatite composites with different titania additive amounts （0, 0.5, 1, 1.4, 2, 3, 4 and 5 wt%） have been investigated between 1200 and 1600℃. The optimum values of densificatio...Mechanical properties of alumina-fluorapatite composites with different titania additive amounts （0, 0.5, 1, 1.4, 2, 3, 4 and 5 wt%） have been investigated between 1200 and 1600℃. The optimum values of densification and mechanical properties of composites have been reached with 1.4 wt% of titania after the sintering process at 1500℃ for 1 h. Thus, the rupture strength of alumina-26.52 wt% Fap-1.4 wt% TiO2 reaches 75 MPa. At higher temperature and beyond 1.4 wt% TiO2 ,the densification and mechanical properties were hindered by the formation of both intergranular porosity and secondary phase. X-ray diffraction （XRD） analysis of alumina-Fap-TiO2 composites shows the formation of aluminium titanate （Al2O3-TiO2：Al2TiO5 ）. The 27Al magic angle scanning nuclear magnetic resonance analysis of Al2O3-Fap-TiO2 composites reveals the presence of octahedral and pentahedral aluminium and novel environment relative to tetrahedral aluminium sites.展开更多
文摘A new method for corrosion protection of Al-based metal matrix composites (MMC) was developed using two-step process, which involves anodizing in H2SO4 solution and sealing in rare earth solution. Corrosion resistance of the treated surface was evaluated with polarization curves. The results showed that the effect of the protection using rare earth sealing is equivalent to that using chromate sealing for Al6061/SiCp. The rare earth metal salt can be an alternative to the toxic chromate for sealing anodized Al MMC.
文摘The effects of positron diffusion on the measured S parameter have been investigated by a point-source diffusion model and a δ function method. Firstly, the theoretical analyses of the effects are presented for the samples of a homogeneous semi-infinite medium and a film of definite thickness. Then the results are used to analyze the S parameters in several composite systems and interface models.
文摘We perform synthesis, characterization, and application of nanostructured diamond composites. The enhancements of the thermomechanical performance of bulk diamond compacts in terms of hardness, fracture toughness, wear resistance, impact strength, and thermal stability are our project objectives. It is to aim at applying an advanced nanosynthesis process for the manufac-turing of superhard and ultratough diamond/SiC nanocomposites with the implementation of nanofiber reinforcement. The R&D re-sults can be used in multi-industrial applications, particularly, for drill bits designed to encounter dynamic impacts for high speed oil/gas drillings, thus to achieve high efficiency and energy saving. Science and technology (S&T) researches on precursors, cata-lyst, reactive sintering, and in-situ/real-time characterization of high P-T neutron/X-ray diffraction studies on phase stability, syn-thesis kinetics, residual strain, and yield strength have been applied to help optimizing the nanomanufacturing process. Our R&D ef-fort in high P-T nanosynthesis of TSP diamond/SiC composites is to achieve superior performance of nanomechanics in resisting dy-namic impact and thermal degradation, while still maintaining the super-hardness and super-abrasiveness of diamond and silicon-car-bide. The improved polycrystalline diamond compact (PDC) bit inserts for drilling, boring, and cutting will be applied in harsh envi-ronments so as to meet the demands of the mining, petroleum, and machinery industries. With success of the proposed project, the expected energy savings and reduction of CO2 emission will be significant and the economic advantages are going to be enormous.
文摘Mechanical properties of alumina-fluorapatite composites with different titania additive amounts （0, 0.5, 1, 1.4, 2, 3, 4 and 5 wt%） have been investigated between 1200 and 1600℃. The optimum values of densification and mechanical properties of composites have been reached with 1.4 wt% of titania after the sintering process at 1500℃ for 1 h. Thus, the rupture strength of alumina-26.52 wt% Fap-1.4 wt% TiO2 reaches 75 MPa. At higher temperature and beyond 1.4 wt% TiO2 ,the densification and mechanical properties were hindered by the formation of both intergranular porosity and secondary phase. X-ray diffraction （XRD） analysis of alumina-Fap-TiO2 composites shows the formation of aluminium titanate （Al2O3-TiO2：Al2TiO5 ）. The 27Al magic angle scanning nuclear magnetic resonance analysis of Al2O3-Fap-TiO2 composites reveals the presence of octahedral and pentahedral aluminium and novel environment relative to tetrahedral aluminium sites.
