Papers by Keyword: SHS

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Authors: Jin Yong Zhang, Zheng Yi Fu, Wei Min Wang, Qing Jie Zhang
Abstract: Recently research shows that heterogeneous model is needed to explain some complex combustion behaviors in SHS. However, more heterogeneous details be considered more difficulties will be faced. A micro-heterogeneous & macro-homogeneous model is proposed in this paper based on some previous works for this problem. Combustion compact is divided into lots of little units, which are composed of a large number of small particles. Considering a well-mixed situation, properties of every unit must be almost the same, so the compact can be treated as a macro-homogeneous system on the scale of these little units. During the combustion, every unit will have a heterogeneous properties and change; it can be gotten by a micro-heterogeneous model. Therefore, the micro-heterogeneous characters are connected with the Marco-combustion behaviors. Combustion dynamics of Ti-C-Fe system was studied to certify this model. Results show well consistency with experiments results.
Authors: Tie Ming Guo, Chang Song Han, Jian Gang Jia, Ying Fu, Zhi Hui, Li Qun Wang
Abstract: Thermodynamic calculations indicate that molybdenum particles reinforced copper-matrix composite can be fabricated in CuO-Al-MoO3 powder system. Thermit reaction and self-propagation high-temperature synthesis (SHS) were applied to prepare samples. Then the phases, structure morphologies and properties were studied through the instruments of XRD, SEM and microhardness tester. The results show that nanocrystals are formed in Cu matrix and molybdenum particles are dispersive distributed in Cu matrix. The microhardness of 5﹪Mo-Cu nanocomposite is 110HV,and the relative electric conductivity is 58.6﹪IACS.
Authors: Maxim V. Kuznetsov, Ivan P. Parkin, A. Kvick, S.M. Busurin, I.V. Shishkovskiy, Yuri G. Morozov
Abstract: New experimental methods for investigations of phase formation during SHS have been established. First experiments using penetrating synchrotron radiation and energy dispersive detectors for different classes of complex inorganic materials were carried out at ESRF (Grenoble, France) and Daresbury (UK). A new and very sensitive thermal imaging method (Thermal Imaging Technique (TIT)) based on continuous registration of the whole combustion process by using highly sensitive IR-camera and software developed by MIKRON Instruments Co. (USA) was used for precise registration of the combustion parameters. SHS was performed on different types of pure and doped complex inorganic materials in pellet and powder form in a range of dc magnetic fields up to 20 T and in electrical field strengths up to ±220 kV/m. The dc magnetic field was applied during the reaction, supplied either by a permanent magnet (transverse, up to 1.1 T) or by an electromagnet (longitudinal, up to 20 T). The dc electrical field was applied along the direction of the combustion wave front propagation. The combined processes of SHS and SLS (Selective Laser Sintering) of 3D articles for different powdered compositions were optimized with laser irradiation power.
Authors: Jian Jiang Wang, Xin Kang Du, Hong Wei Liu, Jun Yan
Abstract: Based on SHS reactive flame spray technology, Al2O3 multiphase ceramics coatings were produced. Chemical copper-plating technology was used to produce the Al-CuO powders of copper cladding, which became individual SHS reactive units respectively. The phenomena and principles of the SHS reactive flame spray of the Al-CuO powders of copper cladding forming Al2O3 multiphase ceramics coatings were investigated. It was found that copper cladding of Al-CuO powders were necessary for the SHS reaction during the spray process. The better the cladding was, the more sufficient the SHS reaction, and the higher the transformation rate was. The Cu and Al2O3 fine molten drops produced by the SHS reaction bumped the substrate and flatted to form layer-shaped Al2O3-based multiphase ceramics coatings. The binding strength between the coating and substrate was as high as 19.8MPa, and the micro-hardness of the coatings was Hv712. The overall properties of the coatings were better than those of the ceramics coatings sprayed by the traditional flame spray.
Authors: Xin Kang Du, Jian Jiang Wang, Lian Zhou, Ming Hui Ye, Zhong Min Zhao
Authors: Daniel Rodrigo Leiva, Elíria Maria Jesus Agnolon Pallone, Roberto Tomasi, Walter José Botta Filho
Authors: Wan Hong Zang, Chang Lun Yuan, Yan Li
Abstract: Al2O3-TiC particles reinforced iron matrix functionally gradient material is successfully fabricated by combining the methods of self-propagating high-temperature synthesis (SHS) with casting. The SHS products are analyzed by SEM and XRD and EDS. The results show that the grain size of the particle is round 1μm~3μm, the composition of the Al2O3-TiC/ Fe surface composite takes on a gradient distribution from outside to inside, and transforms gradually to the matrix metal. The hardness below 0.5mm from exterior surface of the functionally gradient materials increases dramatically and gradually changes to the hardness of the matrix. Key words: In situ generation; SHS; Casting; Surface composite material; FGM
Authors: Ying Zhou, Jin Xiao, Guo Tian Ye, Chen Yong Liu
Abstract: In this work, a series of samples of Mo (Si1-xAlx)2 (X =0, 0.10,0.20,0.30,0.40) were prepared by self-propagating high-temperature synthesis (SHS). The influence of the addition of Al on the structures and the micrographs of the final compounds were investigated. X-ray diffraction pattern characterization (XRD) and scanning electron microscopy (SEM) were used to characterize the obtained products. It was found that, the reactions between Mo and Si could be promoted with introducing Al during the SHS process. The high temperature β-MoSi2 phase with hexagonal structure (C40) was obtained and the peaks of the C40 phase shifted towards a higher d value with increasing aluminum substitution. The substitution of Al could reach to 40%. The morphology of the final products was similar with that of the raw Mo powders, which was independent of Al contents.
Authors: Bao Cai Xu, Rong Xia Duan, Jian Jiang Wang, Hong Fei Lou, Long Zhang
Abstract: Barium ferrites hollow microspheres were prepared by self-propagating high-temperature synthesis self-reactive flame spraying method. The droplets enter in the cooling medium and solidified rapidly so that the gas can not escape to remain holes inside the products. The powder samples were used for characterization. The microstructure and crystal structure were studied by SEM, EDS and XRD. The results show that the obtained particles are hollow microspheres. They are spherical or ellipsoidal shapes from nanometer dimension to several micrometers. The phase structure of composite powders is the mixtures of barium ferrite and Fe2O3.
Authors: Vladimir E. Ovcharenko, Sergei Grigorievich Psakhye, E.N. Boyangin
Abstract: We show here that Ni3Al compound which is widely used as the base metal for advanced multipurpose hot-resistant alloys may be efficiently bulk nanostructured for improving its physical and strength characteristics. Developing the nanostructured component in the bulk of the intermetallic compound is achieved by plastic deformation of an SHS product during its synthesis and crystallization under conditions of thermal explosion of nickel/aluminum powder mixture of stoichiometric composition. It was shown that the nanosize component is formed on the basis of intermetallic Ni3Al synthesized by SHS under hot forging conditions from nickel/aluminum powder mixed with an inert binder component. Developing the nanosize structural components improves strength of the intermetallic alloy.
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