Boron carbide, which has a high melting point, outstanding hardness, good mechanical properties, low specific weight, great resistance to chemical agents and high neutron absorption cross-section ( ) is currently used in high-technology industries for example, fast breeders, light weight armors, high-temperature thermoelectric conversion, wear resistance applications, e.g., as blast nozzles, wheel dressing tools and nuclear industry, e.g., shielding material and control rods etc.
Boron carbide can be synthesized by a variety of high temperature methods, such as the direct reaction of carbon with boron; carbon-thermal reduction of boron oxide( ) over 1000 ; reduction of by at a temperature of 1500 with laser; thermal decomposition of a mixture of pure carbon and boron trilogies in an atmosphere of hydrogen; gaseous reaction between and a methane-hydrogen mixture in r.f. argon plasma.
The most commercially viable and industrial method is from reduction of boric acid with carbon black at a temperatures over 1750 .The product thus obtained is hard and consists of excess unreacted carbon. The hard mass is crushed and pulverized to the requisite mesh size and purified by chemical and thermal oxidation method because of their contamination from grinding media.
In this work, boron carbide was produced from inexpensive raw materials such as boric acid (boron source) and citric acid (carbon source) by sol-gel method. Aqueous solution of boric acid in presence of citric acid forms a stable gel under controlled pH condition. The gel on subsequent pyrolysed under vacuum. The precursor from primary pyrolysis with stoichiometric composition was heated in a tube furnace under vacuum to 1250, 1350, 1450, and 1500 with a heating rate of 5 and held for 2.5 hr at temperature.
XRD patterns were taken from the samples prepared at different temperatures. From the patterns, it was found that no reactions have occurred at 1250 and the product contains B2O3 and C. By¬ increasing temperature to 1350 it looks that some reactions have taken place, but unreacted B2O3 and C are seen yet. Whereas, at 1450 and 1500 no B2O3 is observed and the only impurity seen is C. This indicates that at 1450 and higher temperatures the reaction is completed. From the SEM patterns it can be seen that the shape of the particles is somewhat between spherical and elliptical. The free carbon and particle size of the product were analyzed.
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