Papers by Keyword: SHS Process

Abstract: The paper describes the researches of the SHS process initiation in samples of powder mixtures of reagents intended for steel parts hardening with an excess of Al or B₂O₃ by a heat source. Mixtures of reagents with different weight ratios of components were used as samples. Thereat, the initiation of SHS process in thin layers was conducted with a coating layer thickness of no more than 6 mm for all tested compositions. The dependences of the combustion rate on various factors including particle size of powder materials and charge composition have been obtained. The main factors influencing the dependences of initiation (ignition) and combustion rate are established, and the degree of influence of these factors on the dependences is estimated. The obtained results made it possible to correct the composition of the base mixture reasonably in order to achieve the required combustion rate.

Abstract: Porous NiTi alloys were successfully synthesized by two different processes, including self-propagating high-temperature synthesis (SHS), and a combined process of decomposition – sintering. A systematic comparison of micro-structures and mechanical properties of these alloys was investigated. The results showed that the SHS process was better than decomposition – sintering process. By controlling the processing parameters of SHS, the received porous NiTi alloys showed that the porosity and pore were larger, and ratio of opened-pore reached up to 80%. The porous NiTi alloys fabricated by SHS process also exhibited good properties, such as a high compressive strength (up to 250MPa), and elastic modulus in range of 6.1 – 7.0GPa. The porous NiTi alloys synthesized by decomposition – sintering process have lower porosity (26-43%), lower compressive strength (< 110MPa), lower elastic modulus (< 1.2GPa) but the strain could be reached to 10%.

Abstract: The article presents an alternative method of obtaining aluminium cast iron in the process of self-propagating high-temperature synthesis from disperse waste of machine-building enterprises. The deficiencies of the traditional methods for obtaining structural iron castings with aluminum are established. The analysis of the factors influencing the strength of the SHS aluminium cast iron, the planned experiment for obtaining the maximum strength of SHS aluminium cast iron for two input factors varying at three levels and three parallel observations were carried out. The statistical processing of experimental results is performed. The mathematical model is obtained for the dependence of operational factors on the composition of the charge of the SHS process. The significance of the regression coefficients of the equation is determined. The adequacy of the obtained equation is checked for the results of observations. The analysis of the conditions for the formation of the microstructure of aluminium cast iron in the process of SHS-casting is presented.

Abstract: In this study, silica obtained from the rice husk was used to synthesis of Al₂O₃/SiC nanoparticles. For this reason, the ash obtained from the burning of the rice husk which contains more than 93 wt. % silica, aluminum and carbon powders with the molar ratios of 3:4:6 were mixed and then compacted into pellets by using a cylindrical die under a pressure 50MPa. In order to conduct the self-propagating high-temperature synthesis (SHS), the produced pellets were placed in an electrical furnace at 850°C under the argon gas atmosphere. Then, a planetary ball milling for 4 to 24h was used to decrease the particle size of the synthesized composite. The results of XRF, XRD, SEM and DLS investigations shown that the rice husk ash can be used to fabricate Al₂O₃/SiC nanoparticles with an average particle size of about 80 to 65nm via SHS process and ball-milling for 12 to 24h.

Abstract: This article provides a method of disposing of a particulate waste that allows treatment to produce ferroaluminum. In this work the optimization of the charge composition was carried out by the planned experiment to obtain the maximum performance properties of the SHS ferroaluminum. The article presents the analysis of the conditions of formation of the ferroaluminum microstructure in the process of the self-propagating high-temperature synthesis. The SHS process is initiated in the mixture composed of the dispersed waste engineering. The factors influencing the formation of the alloy structure were brought out.

Abstract: In this study, the self-propagating high-temperature synthesis (SHS) and following acid leaching techniques were carried out to produce zirconium diboride (ZrB2) powder. In the SHS experiments, technical grade ZrO2 powder, and different amounts of B2O3 and Mg powders were used. The SHS products were obtained in the form of black, spongy solid. In the leaching step, the effect of different acid concentrations on selective leaching was investigated by using optimum SHS product to eliminate the impurities such as MgO, Mg3B2O6 and Mg2B2O5. The products obtained were characterized by using XRD, ICP and SEM techniques.

Abstract: The nature of SHS process was studied, and conditions under which equilibrium and non-equilibrium regimes take place for wave propagation and structure formation of SHS products are under consideration. The important role of cooling down time is shown. Depending on its magnitude, either autoannealing or autoquenching processes can take place in the products after combustion front propagation. The correlation between transition from non-equilibrium to equilibrium state of the product with prolongation of cooling time was examined as well as character of products and processes was indicated in dependence on relationship between the characteristic times of combustion, time of cooling down, and structure formation in SHS product.