Synthesis of dehydrated magnesium borate powders and the effect on the properties of MgO-C refractories

For the synthesis of magnesium borate powder, magnesium carbonate and boric acid powders were mixed in ethanol and then investigated by differential thermal analysis (DTA) and thermogravimetry (TG). X-ray diffraction (XRD) results of the samples showed the formation of Mg2B2O5 phase at 500 degrees C and Mg3B2O6 at 650 degrees C. The synthesized powder used as an antioxidant additive in magnesia-graphite bodies containing 20% graphite. After curing at 200 degrees C and firing at 1200 degrees C and 1400 degrees C for 2 hrs in a coke bed environment, its physical and mechanical properties and also microstructural features were investigated. The results showed that after curing at 250 degrees C, the addition of magnesium borate led to an increase in cold crushing strength at about 20%. Comparing the samples with additives and without any additives at 1200 and 1400 degrees C showed that the cold crushing strengths were improved about 45%, 35%, respectively. In addition, the results clarified that magnesium borate (Mg3B2O6) phase led to improve oxidation resistance.