Synthesis of highly dispersed chromium diboride powder by means of boron carbide reduction using nanofiber carbon

The article describes the synthesis of highly dispersed powder of chromium diboride CrB2 using nanofiber carbon in the process of boron carbide reduction. This compound is a refractory material with melting point of 2200°С. Due to its chemical and physical properties, chromium diboride is widely used in different fields of industry. Chromium oxide (III) Cr2O3, boron carbide B4C and nanofiber carbon C were used as initial reagents. The synthesis was conducted by the use of an induction furnace of a melting pot type in a protective atmosphere of argon at temperatures of 1300, 1500 and 1700°С. Using X-ray phase analysis, atomic emission spectroscopy with inductively coupled plasma, scanning electron microscopy and synchronized thermal TG-DSC analysis general properties and characteristics of the materials obtained were determined. Particle size distribution studies have been also carried out and it has been found that the average size of chromium diboride powder was 7.95 µm. It has been found that the sample of chromium diboride obtained resists oxidation under higher temperatures (1000°С). The paper also deals with the problem of targeted planning of chromium diboride synthesis depending on different experimental conditions. By the use of targeted experiment planning method, the effects of such parameters as synthesis temperature, time of stirring of the initial batch, as well as carbon reducing agent which significantly affects the synthesis process were estimated. It has been found that optimum synthesis conditions consist in an activation of batch in a ball mill with acceleration of 10g for 5 minutes and a synthesis at 1700°С for 20 minutes.