Study Of By-product Of Nabh_4 Hydrolysis And Its Behavior At A Room Temperature

摘要

We report here the observation of phase transitions within mixtures of NaBH_4 and various organic additives exposed to open air at a room temperature 22(±1) ℃ and air humidity 35(±5)%. During the exposure the phase composition of materials was monitored by X-ray diffraction. Also, we found that new crystal phases appear during the exposure. Initially the phase, which was identified as the orthorhombic phase with unit cell parameters a = 10.48 A, b = 6.91 A and c = 12.25 A and Pbca space group, was formed. It has been ascertained that orthorhombic phase is NaBH_4·2H_2O - hydrated sodium boron hydride. Upon prolonged exposure this phase then finally transformed to the known crystalline tincalconite (Na_2B_4O_5(OH)_4·3H_2O). We explained the observed phase transitions as hydrolysis of NaBH_4 and hydration of by-product due to absorption of air humidity. It was ascertained that kinetics of processes depends on kind of organic additives.