Effects of boron oxide composition, structure, and morphology on B4C formation via the SHS process in the B2O3–Mg – C ternary system

Aghili, Siavash; Panjepour, Masoud; Meratian, Mahmood; Hadadzadeh, Hassan

doi:10.1016/j.ceramint.2019.11.217

Cited by 13 publications

(3 citation statements)

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“…Several publications have already reported the possibility of synthesis of boron carbide by SHS from boron oxide as a starting material, where the reduction was carried out with magnesium and carbon was added to the mixture as a carburizing agent [ 32 , 33 , 34 , 35 , 41 , 42 , 43 ]. To mitigate combustion conditions, namely, to reduce the combustion temperature and to contribute to nanostructure formation, the dilution of the initial mixture by end-products and halides was used [ 44 , 45 ].…”

Section: Resultsmentioning

confidence: 99%

“…In contrary, the magnesiothermic reduction of boron oxide, which is the most common procedure to obtain boron of a purity grade between 90% and 98%, is exothermic (T ad = 2110 °C), but it always leads to a high amount of secondary products, such as MgO, B 2 O 3 and magnesium borides. The magnesiothermic SHS reduction of boron oxide in the presence of carbon (B 2 O 3 -Mg-C exothermic mixture) was proposed by several authors [ 32 , 33 , 34 , 35 ] for the preparation of porous agglomerated particles of B 4 C with a high specific surface area, but the reaction has a low yield (≈19%) and requires long-lasting leaching, the carbide is usually contaminated with magnesium borides formed as stable compounds [ 36 ], and the process is very sensitive to carbon impurities [ 37 ].…”

Section: Introductionmentioning

confidence: 99%

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Novel Pathway for the Combustion Synthesis and Consolidation of Boron Carbide

et al. 2022

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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.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Novel Pathway for the Combustion Synthesis and Consolidation of Boron Carbide

et al. 2022

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“…It can be also used as a catalyst; in the preparation of fluxes, and sintering aid or additive in many systems. Boron oxide and its compounds have been used as a source of boron in preparing a variety of materials such as boron nitride, boron carbide, borates, titanium borides [1][2][3][4][5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

The kinetics and mechanism of B2O3 formation from the chemically-synthesized HBO2 under non-isothermal conditions

Aghili

Panjepour

Meratian

2021

Reac Kinet Mech Cat

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In this investigation, a crystalline metaboric acid (HBO 2 ) powder was subjected to a dehydration process to transform it into boron oxide (B 2 O 3 ) using thermogravimetry (TG) technique in an argon atmosphere under non-isothermal conditions at different heating rates (3, 5, 10, and 15 °C min −1 ). The results of kinetic analysis revealed that the dehydration process was a complex one comprising a consecutive region (region I) followed by a parallel one (region II). Using the relevant kinetic models, the mechanisms involved in each region were analyzed by a proposed method for the complex reactions separately and find that the dehydration mechanism in the region I consisted of the kinetic models R 4 : g(α) = [1 − (1 − α) 2/3 ] (the chemical reaction at the HBO 2 /H 2 B 4 O 7 interface) and D 3 : g(α) = [1 − (1 − α) 1/3 ] 2 (the diffusion of H 2 O (g) in the H 2 B 4 O 7 layer), while that in the region II was parallel and consisted of the models D 3 (the diffusion of H 2 O (g) in the H 2 B 4 O 7 layer) and R 4 (the chemical reaction at the of H 2 B 4 O 7 /B 2 O 3 interface). Therefore, based on the kinetic results, the mechanisms of complex processes could be determined by the method.

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