Papers by Keyword: Composite Ceramic

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Authors: Wei Li, Cheng Ge Wu, Qiang Han Fang
Abstract: The iron-based composite ceramic powder Fe-WC is produced by ball milling with synthetic tungsten mine and graphite. The process is accomplished through mechanical activation and reductive diffusion of the reactant powders during the milling process. The products are analyzed by means of XRD, DTA and EPMA. The results approved that the reaction does not carry through completely when the milling time is less than 8h. However, the composite powder of Fe and WC is gained by annealing from powders milled under 180V of the milling machine. The apparent activation energy of the reductive reaction is gradually decreased with the extending of milling time by mechanical activation.
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Authors: Fu Meng Li, Yi Hua Feng, Hao Sun, Hai Xia Huang
Abstract: Under the special circumstances, we cannot use the lubricating medium and want to overcome the lake of friction properties of the single material in the cutting process, we will be done mainly through two ways: prepared self-lubricating tool and preparation of coating tools, in order to work reliable under the extreme conditions.
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Authors: Yong Cheng, Xun Jia Su, Gen Liang Hou, Zi Liang Shi, Chong Rong Zhong, Ya Kun Xing
Abstract: Cf/ZrC-xCu composite ceramics with different Cu content were prepared by self-propagating high-temperature synthesis/pseudo–hot isostatic pressing (SHS/PHIP). The effect of Cu content on the microstructure and properties of Cf/ZrC composite ceramics were investigated. Our results indicated that carbon fiber was serious chemical damaged in the absent of Cu, accompanied by attenuating of the reinforced effect.Whereas, the density of the complex was increased in the present of Cu content in a dose-dependent-way due to the better fluidity of Cu. Adding to Cu into the complex material leads to the increased diffusion resistance of the elements, decreased damage of the carbon fiber. Meanwhile, the ability of flexural strength manifested as incureasing-decreasing manners according to the elevation of Cu content, while, the fracture toughness was increased gradually. We finally concluded that we could get the best composite ceramic in the present of 25V% of Cu.
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Authors: Zong Hui Zhou, Xin Cheng, Pi Yi Du, Jun Chang, Shi Feng Huang, Ling Chao Lu, Zheng Mao Ye
Abstract: The phase composition of (1-x)BaO·xSrO·0.7TiO2·0.3Nb2O5 (BSTN) composite ceramics was analyzed by XRD, and the effect of Sr/Ba ratio on the dielectric properties of BSTN was investigated by impedance analyzer. The results showed that any sample with different x value contained two phases-the perovskite phase and the tungsten bronze phase. The dielectric constants of BSTN basically decreased while the tanδ increased with the increase in x value. Both dielectric constant and tanδ decreased with the applied frequency increased for the same x value. There were two Curie points for BSTN composite ceramics. The first one belonging to the perovskite phase decreased with the increase in x value, but the second one belonging to the tungsten bronze phase kept almost constant at about 300°C.
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Authors: Zong Hui Zhou, Pi Yi Du, Gao Rong Han, Wen Jian Weng
Abstract: The effect of SrO/BaO ratio on the phase structure of the (1-x)BaO.xSrO.0.7TiO2.0.3Nb2O5 composite ceramics was investigated by XRD and SEM. The results showed that the SrO/BaO ratio increased in the perovskite phase and kept almost constant in the tungsten bronze phase as the content of SrO increased in the composite system. The constant SrO/BaO ratio in the tungsten bronze phase was about 0.667. The crystal lattices of the perovskite phase in the composite system were larger and smaller respectively than that in pure (1-x)BaO.xSrO.TiO2 system when SrO/BaO ratio were respectively <0.667 and >0.667. The crystal lattices of the perovskite phases in both systems showed the same crystal lattices when SrO/BaO = 0.667. Affected by the SrO/BaO ratio required in the tungsten bronze phase in composite system, the contents and average grain size of the perovskite phase decreased, while the content of tungsten bronze phase increased as the SrO/BaO ratio increased.
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Authors: Xin Cheng, Zong Hui Zhou
Abstract: The effects of Mn doping on the phase composition and dielectric properties of (1-x)BaO·xSrO·0.7TiO2·0.3Nb2O5 (BSTN) composite ceramics was investigated. The results showed that the dielectric constants of 0.7BaO·0.3SrO·(0.7-z)TiO2·0.3Nb2O5·zMnO2 (BSTNM) composite ceramics basically decreases as the content of doped MnO2 increases at the same applied frequency, while tanδ decreases when value z≤0.01 but increases when value z>0.01. The phase transition temperature of tungsten bronze phase in BSTNM composite ceramics increases with the increase of value z.
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Authors: You Feng Zhang, Qing Chang Meng, De Chang Jia, Yu Zhou
Abstract: The Al2O3/LiTaO3 (ALT) composite ceramics were fabricated by hot pressing method and polarization treated at different temperatures along height and width directions. Effects of polarization treatment on mechanical properties of the ALT composite ceramic were investigated. Flexural strength decreased with the increase of polarization temperature. Meanwhile, the flexural strength of samples polarized in height direction is higher than that polarized in width direction. The composite ceramic fractures intragranularly, and many rupture steps in polarization direction were observed on fractographs of the composite ceramics. Domain switching in LiTaO3 particles increased the resistance of crack propagation and improved the mechanical properties of the polarized ALT composite ceramics.
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Authors: Yi Hua Li, De Chang Jia, Zhi Hua Yang, Yu Zhou
Abstract: Alumina ceramic, with high mechanical strength, good electric insulation, high hardness and good corrosion resistance performance, has been widely used in machinery, electronic and electrical, chemical, medicine, construction and other high-tech areas. In this study, both silicon sol and zirconia particles are incorporated into the system and dense alumina composite ceramics were prepared by cold isostatic processing and pressureless sintering at 1550 . The influence of additives on phase composition, microstructure and mechanical properties were investigated. The XRD results show that mullite phase was generated in the composite ceramic. The composite ceramic has excellent comprehensive performance. For example, the sample with 3wt.% SiO2 and 5wt.% ZrO2 has density of 3.87g·cm-3, Vickers hardness of 17.6GPa, flexural strength of 369.0MPa, youngs modulus of 374.2GPa and fracture toughness of 3.57MPa·m1/2.
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