Investigation of the pre-milling effect on synthesis of nanocrystalline TiB2–TiC composite prepared by SHS method

NanocrystallineTiB2–TiC composite was readily prepared by self-propagating high-temperature synthesis (SHS) of the mechanically milled powders. Mixture of Ti and B4C as the starting materials were initially milled for 1, 3, 6 and 9 h, and pressed to form the pellets. The green compacts were placed in a tube furnace preheated to 1100 °C and 1200 °C in argon atmosphere. The samples were characterized by XRD, SEM and TEM analytical techniques. The results showed that, increasing the milling time enhances the formation of TiC and TiB2 phases and reduces the furnace temperature necessary for the synthesis process. In fact, the powder milled for the longer time, required the lower temperature for the SHS process to occur.

Better understanding of the aforementioned processes can be obtained by examining a plot of the enthalpies of the reactants and products as a function of temperature. Such plots are often used to predict the properties of self-propagating high-temperature synthesis processes. The following figure has been drawn by Factsage software that shows the total enthalpy of the reactants (upper line) and of the products (lower line) as a function of temperature.Figure optionsDownload as PowerPoint slideHighlights
► TiC–TiB2 nanocomposites were formed via SHS of mechanically milled reactant.
► The crystallite sizes of TiB2 and TiC in the product were 46 and 34 nm respectively.
► The crystallite size calculations were confirmed by the TEM results.
► The use of milling process has an undeniable role to achieve nano-size product.