Thermal analysis of dispersed boron powders

367

THERMAL

F. N. TAVADZE, L. K. SVANIDZE

ANALYSIS

OF DISPERSED

K. P. TSOMAYA, D. L. GABUNIA, and T. SH. BADZAGUA

Institute of Metallurgy,

BORON

POWDERS*

0. A. TSAGAREISHVILI,

Academy of Sciences of the Georgian S.S.R., Tbilisi (U.S.S.R.)

Thermal and thermogravimetric analyses of dispersed boron powders with grain sizes in the range 100 - 5 urn were made. The powders were obtained by grinding compact crystalline boron in a ball mill and in an apparatus of the vortex type. Experimental results showed a series of thermal effects at the temperatures 350, 370, 510 and 610 K. Their intensity increases when the boron particle size decreases. These effects are caused by the presence of B,O, in the boron powders, the content of which increases with increasing particle dispersion. It was established that an extensive oxidation of finely dispersed powder fractions starts above 760 K. In massive specimens above 760 K the weight increase during the heating process is small. It was noted that heating finely dispersed powder fractions above 770 K initiates and intensifies the effects characteristic for the heating process of boric acid. The possible causes and conditions for the appearance of the observed thermal effects are discussed.

*Abstract of a paper presented at the 7th International Symposium Related Compounds, Uppsala, Sweden, June 9 - 12, 1981.

on Boron, Borides and

c Elsevier Sequoia/Printed

in The Netherlands