EFFECT OF HCl CONCENTRATION ON ZrB2 SEPARATION FROM A SELF-PROPAGATING HIGH- TEMPERATURE SYNTHESIS (SHS) PRODUCT

The self-propagating high-temperature synthesis (SHS) of zirconium diboride followed by hydrochloric acid leaching was carried out in this study. In the SHS stage, the initial mixture of B2O3, ZrO2 and Mg powders were ignited and then a mixture of the ZrB2, MgO, Mg3B2O6 and Mg2B2O5 were formed. In the leaching step, the SHS product was leached in the acid solution to remove impurities i.e. MgO, Mg2B2O6 and Mg2B2O5. The effects of temperature and acid concentration on the selective leaching were investigated. The obtained products were characterized by using X-ray diffraction and SEM techniques

EFFECTS OF STOICHIOMETRY ON BORON CARBIDE PRODUCTION VIA SELF PROPAGATING HIGH TEMPERATURE SYNTHESIS

In this study, a self-propagating high-temperature synthesis (SHS) and following acid leaching techniques were carried Out to produce boron carbide (B4C) powder. First, B2O3 was obtained through calcinations of H3BO3 at 1073 K for 2 hours. Then, the glassy B2O3 obtained was crushed and sieved. In the SHS experiments, different amounts of B2O3, Mg and C black were used. The SHS product was obtained in the forni of black, spongy solid. In the leaching step, the SHS product was leached in a HCl solution to eliminate the MgO and Mg3B2O6. The effect of acid concentration on the selective leaching was studied at different concentration range, solid/liquid (S/L) ratio, and temperature. The products obtained were characterized by using Xray diffraction, chemical analysis and SEM technique

A REFINEMENT STUDY OF SHS ALLOYS BY MINI VACUUM ARC MELTING SYSTEM

Self-propagating high temperature synthesis processes are one of the highly productive and economically reasonable methods for the metallurgy industry. The synthesis of compounds by self-propagating high temperature takes place as a combustion reaction of reactive raw materials and the following chemical reaction by heat transfer that allows an easy production of ceramic and intermetallic materials. In this study, the refinement of nickel-based SHS alloys were carried out by remelting of the alloys via mini vacuum arc melting system. The changing in the microstructural and mechanical properties and chemical compositions of the obtained SHS alloys were investigated by remelting process under argon atmosphere. The obtained product samples were characterized by wet chemical analysis, Vickers microhardness and Scanning Electron Microscope (SEM) techniques

Effect of initial composition on boron carbide production by SHS process followed by acid leaching

In this study, iron-free boron carbide powders (B4C) were produced from the milled SHS (self-propagating high temperature synthesis) products followed by leaching in an aqueous hydrochloric acid (HCl) media. The SHS mixtures were composed of boron oxide (B2O3), carbon black and magnesium. Thermochemical simulations were performed to estimate the effect of initial composition on the SHS process. In the SHS experiments, it was found that the formations of boron carbide and magnesium borates were directly related with B2O3 and carbon black contents in the initial SHS mixture. The aqueous HCl leaching of the SHS products did not only eliminate the unwanted byproducts (i.e. MgO, Mg3B2O6 and Mg2B2O5) but also enhanced substantially the pore structure of the particles. Even though the leached SHS particles (d(0.5) = 7.96 mu m) were much coarser than that of the commercial powder (d(0.5) = 1.73 mu m), the surface area of the leached product (15.56 m(2)/g) was found to be larger than that of commercial one (4.92 m(2)/g). (C) 2012 Elsevier Masson SAS. All rights reserved

Production of Al-Co-Ni Ternary Alloys by the SHS Method for Use in Nickel Based Superalloys Manufacturing

In this study, Al-Co-Ni ternary alloys were synthesized, in order to obtain low-cost starting material for Ni-based superalloy production, by a self-propagating high temperature synthesis (SHS) both under normal gravity conditions (a = 9.81 m/s(2)) and under high gravity conditions (up to 1000 g-force) by using a centrifugal machine. The mixture of Co3O4-NiO powder were reduced by Al powder for the production of SHS alloys with the estimated compositions of 5-10 mass% Al, 20-65 mass% Co, 25-75 mass% Ni. The effect of green mixture compositions and centrifugal overload on combustion temperature, alloy/slag separations, chemical composition and microstructure of final alloys were investigated. The chemical analysis results showed that production of SHS alloys were achieved by having up to 86.12% of Co and 92.32% of Ni recoveries. The highest metal recovery value was obtained in SHS alloy with the estimated composition of 10%Al-65%Co-25% Ni by the addition of 20% Al2O3 into the green mixture. The metal/slag separation efficiency increased by increasing the centrifugal overload