Isothermal calcination kinetics of boric acid and its use for nano boron oxide production under cryogenic conditions

The isothermal calcination kinetics of H3BO3 to B2O3 was firstly investigated as a function of time at 160, 200, 240 and 280 °C using heterogeneous and homogeneous reaction models and were characterized by XRD, FTIR-ATR, SEM and DTA/TG devices. Peaks in XRD patterns and bands in FTIR-ATR spectrum confirmed the structure of H3BO3 and B2O3. SEM showed that H3BO3 had a rather clean, flaky, smooth and plate-shaped surface while B2O3 had a rough surface. TG analysis confirmed that H3BO3 was degraded in two steps. Avrami model fitted a very good agreement with the experimental data. The activation energy was calculated as 14.2 kJ/mol. The smallest particle size for nano B2O3 was measured as 33 nm with Zetasizer NanoS. TEM images also confirmed that the particle size of B2O3 was measured to be approximately 50 nm. Additionally, the BET surface area of nano B2O3 was determined as 10.8 m2/g.