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91.
对自调式压板压紧力的计算 ,使其公式化、系列化 ,从而减少人们在使用时选用的难度 ,增加其在实际应用中广泛度 ,使其在实际应用中发挥更大的作用。 相似文献
92.
Haoyi Wang Delong Cai Zhihua Yang Xiaoming Duan Bingzhu Wang Bo Wang Daxin Li Dechang Jia Yu Zhou 《Journal of the American Ceramic Society》2022,105(5):3590-3600
A type of boron nitride–magnesium aluminum silicate (BN-MAS) composite ceramics was fabricated by hot-press sintering at different sintering temperatures. The relationship between the sintering temperature and microstructure was investigated by analyzing the interaction between hexagonal boron nitride (h-BN) and the MAS phase. The main MAS phase in the composite ceramics is the α-cordierite phase at a sintering temperature of 1300°C. At temperatures above 1400°C, the inhibitory effect of h-BN on the crystallization of the MAS system is significant, and MAS mainly exists in the form of an amorphous phase. The composite sintered at 1700°C exhibited the highest bending strength of 218MPa. h-BN and MAS were co-enhanced. MAS can be used as an effective liquid-phase sintering aid to assist in the sintering of h-BN, whereas h-BN can absorb the fracture energy of the composite ceramics through the pull-out and bridging effect of the particles. 相似文献
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Sandan Kumar Sharma B. Venkata Manoj Kumar Kwang-Young Lim Young-Wook Kim S.K. Nath 《Ceramics International》2014
Dense silicon carbide (SiC) ceramics were prepared with 0, 10, 30 or 50 wt% WC particles by hot pressing powder mixtures of SiC, WC and oxide additives at 1800 °C for 1 h under a pressure of 40 MPa in an Ar atmosphere. Effects of alumina or SiC erodent particles and the WC content on the erosion performance of sintered SiC–WC composites were assessed. Microstructures of the sintered composites consisted of WC particles distributed in the equi-axed grain structure of SiC. Fracture surfaces showed a mixed mode of fracture, with a large extent of transgranular fracture observed in SiC ceramics prepared with 30 wt% WC. Crack bridging by WC enhanced toughening of the SiC ceramics. A maximum fracture toughness of 6.7 MPa*m1/2 was observed for the SiC ceramics with 50 wt% WC, whereas a high hardness of 26 GPa was obtained for the SiC ceramics with 30 wt% WC. When eroded at normal incidence, two orders of magnitude less erosion occurred when SiC–WC composites were eroded by alumina particles than that eroded by SiC particles. The erosion rate of the composites increased with increasing angle of SiC particle impingement from 30° to 90°, and decreased with WC reinforcement up to 30 wt%. A minimum erosion wear rate of 6.6 mm3/kg was obtained for SiC–30 wt% WC composites. Effects of mechanical properties and microstructure on erosion of the sintered SiC–WC composites are discussed, and the dominant wear mechanisms are also elucidated. 相似文献
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《Journal of the European Ceramic Society》2014,34(16):4137-4144
Al2O3 particle-reinforced Cr2AlC in situ composites were successfully fabricated from powder mixtures of Cr3C2, Cr, Al, and Cr2O3 by a reactive hot-pressing method at 1400 °C. A possible synthesis mechanism was proposed to explain the formation of the composites in which Al2O3 was formed by the aluminothermic reaction between Al and Cr2O3, meanwhile, Cr3C2, Al, together with Cr reacted to form Cr2AlC in a shortened reaction route. The effect of Al2O3 addition on the microstructure and mechanical properties of Cr2AlC/Al2O3 composites was investigated. The results indicated that the as-sintered products consisted of Cr2AlC matrix and Al2O3 reinforcement, and the in situ formed fine Al2O3 particles dispersed at the matrix grain boundaries. The flexural strength and Vickers hardness of the composites increased gradually with increasing Al2O3 content. But the fracture toughness peaked at 6.0 MPa m1/2 when the Al2O3 content reached 11 vol.%. The strengthening and toughening mechanism was also discussed. 相似文献
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《Journal of the European Ceramic Society》2014,34(15):3635-3640
Laminated HfC–SiC/BN ceramics were successfully fabricated by tape casting and hot pressing. Fully dense HfC–SiC ultra-high temperature ceramics with homogeneous structure were obtained. The introduction of the weak BN layer resulted in a slight decrease of the flexural strength but significantly improved the fracture toughness compared with monolithic HfC–SiC ceramics. The fracture toughness of laminated HfC–SiC/BN ceramics in the parallel direction peaked at 8.06 ± 0.46 MPa m1/2, which increased by 115% than that of monolithic HfC–SiC ceramics. The composites showed non-catastrophic fracture behaviors in both parallel and perpendicular directions. It indicates that laminated structure design is a promising approach to obtain full density HfC–SiC ceramics with high fracture toughness. 相似文献
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通过对PLC特殊功能和计时器功能的应用与开发,最大限度地替代外设控制、检测器件,而系统功能加强,更稳定可靠. 相似文献
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