Production of hexagonal boron nitride by carbothermic reduction of colemanite-boric oxide mixtures

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2011
Kahramansoy, Eylem
Carbothermic production of hexagonal BN by using boric acid and ground colemanite mined from Bigadiç Region in Turkey was investigated by subjecting pellets prepared from B2O3, activated carbon and colemanite mixtures to nitrogen gas at 1500°C. Similar to CaCO3 addition, colemanite addition to the B2O3-C mixtures resulted in higher amounts of h-BN in the final products. As a result of the experiments conducted with colemanite and CaCO3 additions providing the same quantity of CaO to the initial mixtures, similar amounts of hexagonal BN in the reaction products were observed. As a result of the experiments conducted with different compositions of colemanite- B2O3- C mixtures, 5 wt % colemanite addition was determined to be the optimum composition giving the highest amount of hexagonal BN in the reaction products. Increasing duration of the experiments increased the amount and particle size of h-BN formed in the products. Optimum amount of colemanite addition resulted in higher amounts and coarser particles of h-BN in the products than the optimum amounts of CaCO3 addition.