Papers by Keyword: MoSi2

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Authors: Li Chao Feng, Ning Xie, Wen Zhu Shao, Yu Sheng Cui, Liang Zhen
Abstract: MoSi2 and SiC ceramics were prepared by traditional powder metallurgy method. A novel ceramic thermocouple (CTC) used in the high temperature and high corrosion environment was assembled by SiC as the cathode and MoSi2 as the anode. The thermo-emf of CTC was tested from 25 °C to 1600 °C in air. The results show that there is a simple relationship between the thermo-emf of CTC and the temperature. By holding temperature for 70 h at 1500 °C, the deviation of thermo-emf is ±0.37%, and better than 0.75% which is the criteria of industry thermocouple. And also the response characteristics of CTC were analyzed.
Authors: Jin Yong Zhang, Zheng Yi Fu, Wei Min Wang
Abstract: MoSi2 is one of the few intermetallics to have potential for further systems. However, the use of MoSi2 has been hindered due to the brittle nature of the material at low temperatures, inadequate creep resistance at high temperatures, accelerated (pest) oxidation at temperatures between 450~ 550°C. In this investigation Mo(Al,Si2)/Ti3SiC2 composites has been prepared by reaction hot-pressing from Mo, Si, SiC, Ti, Al powder mixture under different temperatures. XRD results show that the main products are Mo(Si,Al)2 and Ti3SiC2. Part of TiC and SiC also appeared at low treating temperature. With the treating temperature increasing SiC disappeared. No evidence show lattice change of Mo(Si,Al)2. It must be the results of sufficient Al added. The electrical conductivity properties were also investigated. Samples treating under different temperatures showed different changes. Samples under high treating temperature showed a near linear change ranging from 27~800°C and Samples under low treating temperature showed a nonlinear change.
Authors: Jian Guang Xu, Shi Bo Guo, Jian Hui Yan, Da Gong Zhang
Abstract: Si3N4 particle reinforced MoSi2 composite powder has been successfully synthesized combustion synthesis method. XRD and SEM results showed that the combustion product was mainly composed by MoSi2 and Si3N4. The as-prepared Si3N4/MoSi2 composite powder has been pressureless sintered at 1600°C for 1h. The microstructure and mechanical properties of the composite were investigated. Relative densities of the monolithic material and composite were 92.2% and 89.6%, respectively. The composite has higher Vicker’s hardness and flexural strength than monolithic MoSi2. Especially the room-temperature fracture toughness of the composite is from 4.21MPa•m1/2 for MoSi2 to 7.25MPa•m1/2 for composite, increased by 72.2%, respectively. The morphology of fractured surface of composite revealed the mechanism of improving mechanical properties of MoSi2 matrix. The results of this work showed that in situ Si3N4/MoSi2 composite powder prepared by combustion synthesis could be successfully pressureless sintered and significant improvement of mechanical properties could be achieved.
Authors: Helmut Mehrer, Sergiy V. Divinski
Abstract: Starting from some fundamentals of solid-state diffusion, we remind the reader to the major techniques for lattice diffusion measurements. Self-diffusion is the most basic diffusion phenomenon in any solid. The paper covers main features of self-diffusion in pure fcc and bcc metals and some important facts about diffusion of substitutional solutes in metals. Binary intermetallics are compounds of two metals or of a metal and a semimetal. Their structures are different from those of the constituents. Some intermetallics are interesting functional materials others have attracted attention as high-temperature structural materials. The paper reviews some results mainly from our laboratory on diffusion in binary intermetallics from the systems Cu-Zn, Ni-Al, Fe-Al, Ni-Ge, Ni-Ga, Fe-Si, Ti-Al, Ni-Mn, Mo-Si and Co-Nb, which have been published in detail elsewhere. Some results for the ternary system Ni-Fe-Al are also mentioned.
Authors: Guang Ping Zou, Zhong Liang Chang, Ying Jie Qiao
Abstract: Carbon nanotubes (CNTs) are good reinforcement of composite materials, through add appropriate amount of carbon nanotubes to MoSi2 can be improve the strength and toughness of MoSi2. In this paper, the material of CNTs/MoSi2 was made through vacuum hot pressing technology. And the split hopkison press bar (SHPB) technology was used for testing the dynamic mechanical properties of CNTs/MoSi2 composite material which has different proportion of CNTs. In the SHPB experiment, in order to get better waveforms, the waveform shaping technology was used for improving the waveform quality, and also the strain gauge technology was used for testing the real strain of the specimen in the dynamic loading process. Through calculating, the dynamic stress-strain curves which under different high strain rate are given. At the same time, the strength, deformation and other test results are analyzed, and also compared them with the static compression experiment results of the CNTs/MoSi2 specimen which is tested by the electronic universal testing machine, and then obtained the dynamic performance of CNTs/MoSi2 composite material.
Authors: G. Wang, Wan Jiang, Guang Zhao Bai, Jian Feng Li
Authors: Jian Ying Gao, Wan Jiang, Gang Wang
Abstract: The phase constituent of MoSi2 with 2.0 wt.% La2O3 synthesized by self-propagating high-temperature synthesis (SHS) was studied. It was observed that the addition of La2O3 as a doping agent significantly influences the thermodynamics and kinetics of combustion process when compared with the combustion synthesis of molybdenum disilicide alone. The morphology of the combustion product was investigated using scanning electron microscopy (SEM). The results showed that the addition of La2O3 could obviously decrease the particle size of the combustion product. Hardness and fracture toughness of the material were directly obtained from the sintered product by using micro-indentation technique. The fracture toughness was found to be significantly enhanced with the addition of La2O3.
Authors: Si Yong Gu, Hou An Zhang, Chun Shi
Abstract: Wear behaviours of La2O3-MoSi2 composite against SiC under different loads at 1000°C and 0.126m/s sliding speed in air were investigated by using an XP-5 type high temperature friction and wear tester. The worn surfaces and phase of the sample were observed by scanning election microscopy (SEM) and X-ray diffraction (XRD), respectively. Results showed that friction coefficient and wear rate of La2O3-MoSi2 composite and SiC decreased with the increase of loads. The wear mechanisms of La2O3-MoSi2 composite are oxidation, adhesion abrasion and fatigue pitting.
Authors: Sébastien Chevalier, Frédéric Bernard, Eric Gaffet, Sébastien Paris, Z.A. Munir, Jean Pierre Larpin
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