Papers by Author: Yu Min Zhang

Abstract: In this investigation, the rare-earth oxide La₂O₃ combined with Al₂O₃ served as sintering additives and commercial α-SiC and B₄C powder were applied to fabricate SiC/B₄C composites by pressureless sintering. The results proved that combination of Al₂O₃ and La₂O₃ sinter additives were effective for densification of SiC/B₄C composites. The influence of sinter temperature on the phase constitution, micro-structure and densification behavior of SiC/B₄C composites was investigated.

Abstract: The network SiC ceramics was fabricated by combining organic foam impregnation and presureless sintering method. The co-continuous interpenetrating SiC/P₂₀ steel composites were fabricated by means of pressureless infiltration technique. The results showed that coarse surface of SiC ceramics with three-dimensional network structure was obtained and observed, which was halpful for the reaction of metal alloy during the impregnation process. The continuous interface could be detected in the SiC/P₂₀ steel composites.

Abstract: Discontinuities have an important influence on deformation and failure of rock mass in practical engineering. It is one of the key issues in modern rock mechanics to investigate geometric characteristics of joints and fractures inside the rock mass such as shape, size, location and direction etc. Based on the deep analysis of the above geometric properties, it is proposed that the stochastic fractures in the rock mass can be simulated with the random numbers generated by the Monte Carlo method. The related algorithm is designed and implemented. The correctness and effectiveness of the algorithm is verified with an example of a project. This will lay a solid foundation to further study the cutting problems of discontinuous rock block systems.

Abstract: The SiC-B₄C multi-phase ceramics was fabricated by gas-pressure sintering technology. The rare-earth oxide Al₂O₃ combined with Er₂O₃/SiO₂ was served as sintering aids. The results were shown that the combination of Al₂O₃/Er₂O₃/SiO₂ sintering additives were effective for densification of SiC-B₄C multi-phase ceramics. The influence of B₄C content on the phase constitution, microstructure and densification behavior of the SiC-B₄C multi-phase ceramics were detailed. The lose weight and volume shrinkage rate of SiC-B₄C multi-phase ceramics had similar evolvement trend when B₄C content increased. Keywords: Gas-Pressure Sintering, SiC-B₄C multi-phase ceramics, densification behavior.

Abstract: The network SiC ceramics was prepared by organic foam impregnation and pressure-less sintering technology. The co-continuous SiC_n/Mg composites were fabricated by vacuum infiltration methods. The results proved that coarse surface was observed on the surface of SiC network ceramics, which was helpful for interface reaction of metal alloy during impregnation process. The continuous interface can be formed in the SiC_n/Mg composites. KF concentration had more important influence on coatings morphologies and polarization behaviors of SiC_n/Mg composites during micro-arc oxidation process.Key words: Interpenetrating, Ceramic Coatings, Micro-arc Oxidation

Abstract: In this paper, the rare-earth oxide Al₂O₃ combined with La₂O₃ served as sintering additives and commercial α-SiC powder were applied to fabricate SiC ceramics by pressure-less sintering technology. The results proved that combination of Al₂O₃ and La₂O₃ sintering additives was effective for densification of SiC ceramics. The influence of sintered additives content on the phase constitution, microstructure and sintering behavior of the SiC ceramics was detailed. The relative density, lose weight and volume shrinkage rate of SiC ceramics had similar evolvement trend with the increase of sintered aids content. Keywords: Pressure-less Sintering, Mechanical Properties, Sintering Behavior

Abstract: In this investigation, the rare-earth oxide Y₂O₃ combined with Al₂O₃ served as sintering additives and commercial α-SiC powder were applied to fabricate C_f/SiC composites by hot-pressing sintering. The results proved that combination of Al₂O₃ and Y₂O₃ sintering additives was effective for densification of C_f/SiC composites. The influence of annealed temperature on the phase constitution, microstructure and mechanical properties of the C_f/SiC composites was detailed. The combination of grain bridging, crack deflection and fiber debonding can improve fracture toughness. Keywords: Pressing sintering, Mechanical Properties, Annealed Treatment

Abstract: In this paper, the commercial α-SiC powder and bargain price La₂O₃/Y₂O₃ additives were utilized to fabricate SiC matrix composites. The influence of the Y₂O₃/La₂O₃ molar proportion on the microstructure, mechanical properties of the C_f/SiC composites were researched. The results showed that La₂O₃/Y₂O₃ additives could not enhance mechanical properties for the C_f/SiC composites distinctly. The flexural strength for the C_f/SiC composites with different Y₂O₃/La₂O₃ proportion was higher than 250MPa. The multi-toughening mechanics including grain bridge, crack deflection and fiber pullout were responsible for improvement of fracture toughness.

Abstract: The micro-arc oxidation technology were utilized to fabricated the ceramics coating in order to improve the corrosion resistance of Ti–6Al–4V alloy (TC₄). The sodium silicate solution was introduced into the electrolyte solution for increasing the coating properties. The effect of the sodium silicate content on the phase composition, surface morphology and potentiodynamic polarization behavior was investigated. The results showed that the increase of Na₂SiO₃ concertration was benefit to improve corrosion resistance of the MAO coating of TC₄ alloy. Key words: Micro-arc oxidation, Ceramic Coatings, Corrosion Resistance.

Abstract: The SiC network ceramics was prepared by the organic foam impregnation method and presureless sintering technologies. The network interpenetrating co-continuous SiC/Mg composites were fabricated by means of pressureless infiltration technique. The results showed that The coarse surface of the SiC network ceramics was observed in the SiC network ceramics, which was benefit for the reaction of the metal alloy during the impregnation process. The continuous and gradual interface can be found in the SiC/Mg composites. It was demonstrated that better interface structure was helpful for improving the bonding strength. Key words: Network Interpenetrating, Interface , Pressureless infiltration