Calcium hegzaboride synthesis with solid phase reaction from calcium metaborate

Black bright colored, powder form, oxygen-free, metallic calcium hexaboride is a refractive compound with low thermal expansion coefficient, low electrical resistance, high hardness, high melting temperature, high chemical stability and high electrical conductivity. The crystal structure has a cubic structure formed by B6 octahedrals bonded to each other by B-B covalent bonds. Each B6 octahedral in the structure is also at the center of a cube with a calcium atom at its corners. Among the methods in the literature on CaB6 synthesis, the most successful method is considered to be the carbothermal reduction method. However, in this method, high process requirements and extra processes are needed to remove the impurities. In the light of the works which previously was synthesized successfully calcium hexaboride by mechanochemical method, calcium metaborate and oxygen-scavenging activated carbon were used as starting reactants in this study. Pilot scale calcium hexaboride synthesis was carried out with three dimensional high energy multiplication solid phase reactions in a spex type ball mill under amospheric conditions. Fourier Transform Infrared Spectrometer analysis was used to characterize the product and determine the synthesis reaction efficiency and it was seen that calcium hexaboride synthesis was achieved successfully. The results of this study may provide new contributions to the existing literature in terms of the production of CaB6 powders.