Effect of Mechanical Activation on the Phase Composition of Lanthanum Hexaboride Produced by SHS Method

Abstract

Background/Objectives: The work considers the effect of mechanical activation of the charge on the phase composition of the final product based on lanthanum hexaboride produced by the method of self-propagating high-temperature synthesis. Methods/Statistical analysis: To study the influence of mechanical activation on the SHS process a mixture of the following reagents was taken: Lanthanum oxide La2O3 and amorphous boron in the mass fractions of 2 to 1 respectively. Mechanical activation was carried out on a planetary ball mill AGO-2S. Findings: The mechanical activation results in particle size reduction, but it has a “saturation threshold”. Optimal parameters of mechanical activation are selected for the most complete conversion of the charge to the desired product of lanthanum hexaboride. It is established that mechanical activation has a “saturation threshold” after which further processing does not bring positive results, the sample either undergoes a thermo-mechanical destruction or the sample is converted to the finished product incompletely, so it is necessary to select the parameters of mechanical activation for each reagent mixture (charge). Optimal average particle size of the charge - 2.52 μm (activation mode with a frequency of 20 Hz and a processing time of 15 minutes) was defined experimentally at which the most complete conversion of the sample to the finished product occurs. Applications/ Improvements: Due to the development of accelerator equipment for various purposes, the main direction of the development of thermal cathodes is the provision of good emission characteristics in harsh environments.