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Hazards
Published in Rick Houghton, William Bennett, Emergency Characterization of Unknown Materials, 2020
Rick Houghton, William Bennett
Diborane (B2H6) is a highly reactive gas with a flammable range of 0.9–98% and an ignition temperature of 38–52°C (100–125°F). Diborane will ignite spontaneously in moist air at room temperature. Diborane is normally stored at less than 20°C (68°F) in a well ventilated area segregated from other chemicals. A sample of diborane can be ignited easily in air with a hot wire or other low temperature source. The flame should be green, but the presence of other materials may obscure the color.
Past, present, and the future of the research and commercialization of CVD diamond in China
Published in Functional Diamond, 2022
Boron doped diamond (BDD) films appeared quite a long time ago in the early 1990s in China. Diborane is the ideal boron source for the preparation of BDD films. However, it is seldom used in China due to the safety issues [31,32]. Diborane is under extremely strict control, because of its serious toxicity, flammability and explosibility. Trimethoxy-boron (dissolved in acetone) had been the widely used less toxic boron source for the preparation of the BDD films [33]. However, it is still toxic to certain extent and corrosive to the pipeline system. Therefore, more nontoxic solid boron source, e.g. boric anhydride (B2O3) and elementary boron, are being used [33]. Recently a mixture of graphite powder and boron powder is also used, which was reported to have the advantage of better uniformity and controllability of the boron concentration in the BDD films [33]. At present, Hot Filament CVD is the most widely used technique for the preparation of BDD films in the industrial scale (see Figure 2). However, microwave plasma CVD is also widely used, particularly for the laboratory research and development. Recently, DC Arc Plasma Jet is also used for both laboratory work as well as for the industrial mass production of BDD films [28, 34]. Right now, the Hebei Plasma Diamond is selling thick freestanding BDD diamond films to the domestic customers with a diameter of 100 mm and a thickness of 0.5-2mm. The substrate materials usually used are titanium, niobium, tantalum and single crystal silicon [33]. However, way back in 2001, Shafer et al. reported a BDD film with diameter of 200 mm and maximum area of 0.5 m2 [35]. However, it was special to use thick freestanding diamond plate as the substrate material for the preparation of BDD films, which is in fact a process of epitaxial diamond growth. The advantage of using free standing diamond plate as the substrate for the preparation of BDD films is most likely due to the high thermal conductivity, which was reported by the USTB to be as high as 17 W/cm.K [36]. Obviously, this is beneficial for certain functional applications where extreme heat dissipation is needed.