For the preparation of boron carbide powder by magnesio-thermal method the mixture of boron trioxide ($B_2O_3$), magnesium, and carbon was reacted at 1400℃, 1500℃, 1600℃and 1700℃ in Ar atmosphere.
X-ray analysis showed that boron carbide, magnesium oxide (MgO), magnesium ortho-borate ($Mg_3 (BO_3)_2$), and unreacted carbon were produced after reaction. After acid treatment only boron carbide and unreacted carbon was observed.
The amount of $Mg_3(BO_3)_2$ which restricted the production of boron carbide was decreased with increase of magnesium content. The amount of unreacted carbon was decreased and that of boron carbide was increased with increase of reaction temperature. Above 1600℃, carbo-thermic reaction was occured spontaneously with magnesiothermal reaction. The amount of unreacted carbon was increased with increase of carbon content. Specially the amount of $Mg_3(BO_3)_2$ was very increased in case that carbon content was small than stoichiometric composition.
Boron carbide obtained from this experiment had a mean diameter of 0.6-0.8㎛ and spherical morphology.
