The electrochemical production of boron

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Virginia Polytechnic Institute

This investigation was conducted to attempt to find an electrolyte that would be suitable for the electrodeposition of boron and to duplicate work performed by previous investigators.

Methods for the electrochemical production of boron previously investigated have either yield a product too impure for practical use, or have involved such serious operating difficulties as to be entirely impractical as commercial processes.

In the present investigation, the systems 4.5KCl-KBF₄-6B₂O₃ and 8.5KCl-KBF₄ were investigated at 800-850°C in an attempt to duplicate the methods reported in the literature as suitable for use as commercial processes. When the electrolyte 4.5KCl-KBF₄-6B₂O₃ was used, boron, 91.2 per cent pure, was electrodeposited at a cathode current density of 0.83 amperes per square centimeter. When the electrolyte 8.5KCl-KBF₄ was used, boron, 96 per cent pure, was electrodeposited at a cathode current density of 1.41 amperes per square centimeter.

The system 5Na₂O-1-LA₂O-6B₂O₃ was investigated at 650 ± 5°C. The deposit obtained proved to contain 68 per cent carbon and only a trace of boron when a cathode current density of 1.04 amperes per square centimeter was employed. The melt attacked the graphite crucible's binder and in no way showed any promise as an electrolyte for commercial use in the production of elemental boron.

The systems 3K₂O-KBF₄-B₂O₃ and 2K₂O-2KBF₄-B₂O₃ were also investigated. The melts alkaline in nature and attacked the graphite crucible's binder. The product obtained when the 3K₂O-KBF₄-B₂O₃ system was investigated at 850 ± 5°C proved to contain 78 per cent boron and 13 per cent carbon. The system 2K₂O-2KBF₄-B₂O₃ was studied to determine the effect of decreasing the alkalinity of the bath. The product obtained when this mixture was studied at 850 ± 5°C proved to contain 85 per cent boron and 6 per cent carbon.