Novel Pathway for the Combustion Synthesis and Consolidation of Boron Carbide

Abstract

A novel pathway for the magnesiothermic reduction of boron oxide and magnesium dodecaboride (MgB12) in the presence of carbon by a self-propagating high-temperature synthesis method was proposed that was aimed at the direct preparation of boron carbide nanopowder. The combined utilization of two boron sources, boron oxide and MgB12, allowed tailoring the overall caloric effect of the process, increasing the yield of the target product and lessening the laborious leaching process. In addition, it is an alternative way to utilize magnesium borides, which are inevitable side products at boron production. Multivariate thermodynamic calculations performed in the B2O3-MgB12-Mg-C system allowed estimating equilibrium compositions of the products and deducing the optimum composition of the initial mixture for obtaining B4C. For the latter, the adiabatic temperature (Tad) is 2100 °C, which is theoretically enough for the implementation of the self-propagating reaction. The combustion reaction was shown to be extremely sensitive to the initial mixture composition, external pressure, as well as sample diameter (heat losses). It proceeds in self-oscillatory mode and leads to the product of a layered macrostructure. The combustion product was then consolidated by the spark plasma sintering technique at different conditions. Vickers microhardness was measured, and the wear erosion behavior was examined. The variation in lattice parameters of boron carbide reflected the influence of synthesis, sintering and erosion conditions on the ordering/disordering of the boron carbide structure.

Formation of TiB2–MgAl2O4 Composites by SHS Metallurgy

“…Among various fabrication routes for preparing multiphasic ceramics, metallothermic reduction reactions (i.e., thermite reactions) combined with combustion synthesis have been recognized as a promising technique for in situ formation of MgAl 2 O 4 -containing composites [ 15 ]. Combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS), which is based on strongly exothermic reactions, has merits of low energy consumption, short reaction time, simple equipment and operation, high-purity products, and in situ formation of composite components [ 16 , 17 , 18 ]. Moreover, aluminothermic and magnesiothermic reduction reactions have Al 2 O 3 and MgO as their respective by-products, both of which are precursors for the formation of MgAl 2 O 4 .…”

Influences of mechanical activation and tartaric acid addition on the efficiency of B4C synthesis

“…These mentioned excellent properties have made B 4 C a perfect choice for adaptable usages in the military, cutting and abrasive tools, aerospace, nuclear, and electronic industries [4,5]. Recently, the applications expansion of B 4 C in various industries has caused researchers to develop different methods for the synthesis of this material such as sol-gel [6], magnesiothermic reduction [7,8], carbothermal reduction [9][10][11], microwave synthesis [12], co-reduction in the autoclave [13], and the elemental reaction of boron and carbon [14,15], all of which are designed to achieve a wide range of particle sizes for prepared B 4 C powder. Hence, controlling the morphology, size, and purity of the final product are some of the challenges of these techniques [16,17].…”

Synthesizability improvement of B4C ceramics by optimizing the process temperature and atmosphere

“…In addition, due to its considerable boron content, B 4 C is employed as neutron-absorbing material [7][8][9][10]. Several methods can be used for the synthesis of B 4 C ceramics such as the solid-state elemental reaction of carbon and boron [11,12], magnesiothermic reduction [13,14], laser irradiation of boron in organic solvents [15], co-reduction in the autoclave [16], sol-gel [17], self-propagating high-temperature synthesis [18], microwave synthesis [19], and carbothermal reduction [20][21][22]. Reducing the temperature of the synthesis process, especially in heat-based methods, has always been one of the topics of interest to researchers in order to overcome the technological limitations caused by high temperatures and economic considerations caused by more energy consumption.…”