Investigations on the hydride rich region of the sodium-boron-oxygen-hydrogen system.

摘要

The purpose of this study was to determine the feasibility of electrolytically hydrogenating sodium metaborate (NaBO2) to sodium borohydride (NaBH4). The NaH-NaBO2-NaBH 4 system was investigated by employing the analytical techniques pressure differential thermal analysis, powdered x-radiation diffraction, and gas evolution analysis. Sodium hydride (NaH) and sodium borohydride are miscible with a eutectic temperature of approximately 390°C. The decomposition temperature of sodium hydride is greatly increased when it is in molten solution with sodium borohydride. Sodium metaborate and molten sodium borohydride are immiscible with each other and react to give sodium orthoborate (Na4B 2O5), boron, and hydrogen at approximately 600°C. The NaH-NaBO2-NaBH4 system has complex reactions occurring between sodium metaborate and sodium hydride, above the NaH-NaBH4 eutectic temperature, forming sodium borohydride and sodium orthoborate, when the ratio of sodium hydride to sodium metaborate is less than 0.8. (Abstract shortened by UMI.)