METHOD OF PREPARING POWDERED BORON NITRIDE Russian patent published in 1998 - IPC

FIELD: inorganic substances technology. SUBSTANCE: boric acid is mixed with reducing agent, mixture is heated, and reaction is carried out until intermediate product is formed, which is then nitrated at elevated temperature to produce boron nitride. Method is distinguished by performing boric acid-reducing agent reaction in electromagnetic waves of microwave frequency region with specific power 0.25 to 2.5 W/cu.cm, whereas maximum characteristic reaction space (cm³, cu.cm) does not exceed value related with wavelength (, cm) and specific power supplied (l_max -, W/cu.cm) in terms of expression λ = 2.97 N_sp.sup. x ln(cm³./0.25). Conversion of boron into nitride is higher than 97% and content of impurities meets requirements for industrial-grade boron nitride. EFFECT: enhanced process efficiency. 2 cl, 2 tbl