Combustion Synthesis in a Mechanically Activated Mg-C-TiO_2-H_3BO_3 System

摘要

TiC-TiB_2 nanocomposite was fabricated by self-propagating high-temperature synthesis (SHS) of mechanically milled powders. H_3BO_3, TiO_2, Mg, and C as starting materials were milled for 0.5, 1, and 3 h then pressed to form pellets. Green compacts were placed in a tube furnace which had been preheated to three different temperatures of 900, 1000, and 1100℃ with argon atmosphere, for the synthesis. The prepared samples were studied by XRD, SEM, and TEM analytical technique. TiC and TiB_2 were not formed during milling process. According to the XRD patterns of synthesized samples, ball milling for 0.5 h is the optimum time for mechanical activation of the mixed powders. Further investigation indicated that 900℃ is the best temperature for the synthesis of this mixture. By using Williamson-Hall method, the average crystallite sizes of TiB_2 and TiC were calculated 40.7 and 75.6 nm, respectively, which were confirmed by TEM images.