Papers by Keyword: SHS

Abstract: The preparation of AlB₁₂ powder by SHS has been investigated. Mg, Al₂O₃ and B₂O₃ powders were mixed as staring materials. SHS products were treated by acid pickling. Adiabatic temperatures were calculated by HSC software. XRD, SEM, TEM analyses were used products after acid picking treatment. The reason caused AlB₁₂ low purity is the formation of Mg_0.4Al_2.4O₄ and insoluble matter

Abstract: Titanium diboride (TiB₂) ceramics have unique physical and chemical properties such as excellent electrical conductivity, high melting point and good corrosion resistance. But due to its relatively low sinterability, the use of this material is currently limited. The addition of Al₂O₃ to TiB₂ can improve its fracture toughness, flexural strength, sinterability, and impact resistance. In this paper, TiB₂-Al₂O₃ composite powders were produced by self-propagating high-temperature synthesis (SHS) method with reductive process from H₃BO₃-TiO₂-Al system. Aluminum and magnesium were used as reductive elements to provide sufficient heat as primary driving force to obtain TiB₂-Al₂O₃ composite. Due to the lower energy release in using aluminum as the initiator of the SHS process, finer microstructure can be achieved. Different stoichiometric amounts of aluminum as precursor were added to the mixture to examine its effect on the reaction progress. To evaluate the complete chemical conversion of the reactants, X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) analyses were carried out. The highest conversion ratio was obtained from the sample containing 1.2 stoichiometric amount of aluminum.

Abstract: This paper presents a novel fabrication process that combines SHS with V-EPC (vacuum expandable pattern casting) and microstructural features of TiB₂+TiC duplex particulates reinforced surface composite with carbon steel matrix. Macro structural observation shows that the surface composite is dense and there are no obvious defects. Microstructural investigation demonstrates that the composite from surface to core is consisted of three different layers, i.e., the top surface compound layer, the interim transitional layer and the bottom carbon steel matrix. A large amount of fine TiB₂ and TiC duplex particles are evenly distributed in the composite matrix, while the concentration are significantly decreased and non-uniform distribution increased for these particles in the interim layer.

Abstract: TiB2-TiC multiphase ceramics were prepared through altering the molar ratio of Mg and C and leached with suitable acid by the combustion synthesis reaction of Mg, C, TiO2 and B2O3. The samples were investigated by XRD and SEM, and the results showed the diameter of the TiB2 was 1.5μm and the shape of the TiC was irregular spherical particles. The diameter and the proportion of the TiB2 were increased with the increase of Mg powder. The formation mechanism of TiB2 has been studied. The optimized proportioning of the molar ratio of Mg and C was 3:2.

Abstract: The pressure-less sintering of slag α-Sialon powder, derived from slag wastes by self-propagating high-temperature synthesis technology, was carried out and the phase assemblages of slag α-Sialon sintered at different temperatures were studied. The results showed that the formation of β-Sialon phase did occur during the pressure-less sintering and was restrained to some extent via mass diffusion of Ca²⁺/Mg²⁺ added in embedded powder in samples. α-Sialon phase with two different unit cells was detected in samples sintered at 1700°C and above, and the formation mechanism was also discussed.

Abstract: Micro-nanoTiB₂ ceramic was prepared through increasing the molar ratio of Mg and leaching with suitable acid by the combustion synthesis reaction of Mg, TiO₂ and B₂O₃, which could get higher temperature and purer product. The Samples were investigated by XRD and SEM, and the results showed the diameter of the TiB₂ was 200 nm ~ 300 nm and the shape of the TiB₂ was irregular hexagonal crystal. The diameter of the TiB₂ was decreased with the increase of Mg powder. The formation mechanism of TiB₂ has been studied.

Abstract: In this work, the influences of the particle size and morphology of raw materials on the formation of MoSi2 by self-propagating high-temperature synthesis (SHS) were investigated. A series of Si powders with different particle sizes and Mo powders with different morphologies were obtained by grinding for 1, 5 and 10 hours, respectively. X-ray diffraction pattern characterization (XRD) and scanning electron microscopy (SEM) were used to characterize the samples. It was found that, the phase compositions and morphologies of the combustion products depended on the particle size and morphology of the raw materials. The particle sizes of Si powders decreased with increasing the grinding time, and a secondary phase of Mo5Si3 was detected in the obtained MoSi2 powders when the smallest particle size of Si powders was about 1μm. While, the particle sizes of Mo powders increased with increasing the grinding times, and the obtained MoSi2 showed massive flaky structures, which were similar to the morphologies of Mo particles.

Abstract: An experimental study on the preparation of molybdenum disilicide (MoSi2) was conducted by self-propagating high-temperature synthesis (SHS) from elemental powder compacts with different pelletizing pressures (0, 50, 100 and 200MPa). The composition of test specimens is Mo:Si = 1:2. The results showed that the propagation time of the reaction front, the density of the combustion products, the particle size and the morphology of MoSi2 were significantly influenced by pelletizing pressure of the reactant compact. In addition, all the samples obtained with different pelletizing pressures were single-phase MoSi2.

Abstract: SHS (Self-propagating High-temperature Synthesis) process is a new method to synthesis materials. The preparation of high temperature and resisting material with Al-CrO3 system was shown in this paper. According to the orthogonal test, a best sample was obtained with high refractoriness reaching 1800 °C and cold crushing strength 20MPa. The SEM analysis was used to analyze the microstructure of the product. The XRD was used to make sure the components of the product. The product has the characteristics of heat insulation, heat insulation and crush resistance, etc.

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.