The choice of methods for lithium and boron determination in lithium-boron alloys

A lithium-boron alloy (LBA) with a high lithium content (up to 70%) is used as an anode material for molten salt batteries in chemical sources of current. We present a complex of developed techniques for determining mass fractions of free lithium, total lithium, and total boron in lithium-boron alloys containing lithium mass fractions no more than 70%, boron mass fractions — no less than 26%. Optimal conditions for preparation of LBA samples and subsequent free lithium extraction from them are determined. The developed techniques are intended for i) extraction-titrimetric determination of free lithium in a content range of 20 - 50% (the relative total error no more than 1.1%); ii) determination of the total lithium content using flame atomic emission spectrometry in a content range of 59.0 - 96.0% (the relative overall error no more than 2.7%; iii) determination of the total boron content by two methods, i.e., potentiometric titration within a content range of 5 - 40% (the relative total error no more than 1.3%) and flame atomic absorption spectrometry within a content range of 4.9-50.7% (the relative total error no more than 4.9%). The results of analysis of full-scale LBA samples for the content of free lithium, total lithium and total boron are presented. It is shown that the application of two techniques for the determination of total boron content in lithium-boron alloys makes it possible to get the convergent results within the limits of measurement errors. The developed techniques are certified by the metrological service of the enterprise and can be used for the incoming and process control of the LBA production.

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