Synthesis and characterization of Al2O3-B4C composites at room temperature by mechanochemical method from aluminum-boron oxide-carbon mixtures at different ratios

In this thesis study, synthesis of Al2O3-B4C composite was carried out by mechanochemical method. Al, B2O3 and C powder materials were used as starting materials in micrometer size. The stoichiometric ratios of the starting materials were milled at 500 rpm for 4, 5, 6, 7, 8, 9 and 10 hours in an argon atmosphere. Milling was carried out using planetary stainless steel balls with diameters of 10 mm and 20 mm and stainless steel pots with a volume value of 125 ml. Ball/powder ratio is selected to be 1/20. During milling from the iron as an impurity (Fe) to eliminate the 3 M HCl acid solution at 105ºC for 3 hours at 350 rpm is made the leaching process. After leaching the powder by washing with distilled water and filtered. The obtained powders were dried at 75ºC for 48 hours. In the grain size analyzes, average grain size of 286 nm and 186 nm was reached with the order of 6 hours and 10 hours after milling. FTIR analysis showed that the peaks of Al-O bonds were between 413 cm-1 and 816 cm-1 and B-C bonds of 1066 cm-1 - 1081 cm-1, 1522 cm-1 - 1529 cm-1, 1022 cm-1 respectively. In the BET analysis, the highest surface area value was found to be 64.72 m2/g for 6 hours of milling and 5.8 m2/g for 10 hours of milling at the lowest surface area value. The densities of the solid samples obtained as a result of the sintering of the samples at 1550°C for 5 hours in an argon atmosphere were measured by the Archimedes method. The relative density of 86% was achieved by shaping with a cold isostatic press with a binder additive to the highest density value.