SYNTHESIS OF TIB2 IN LIQUID COPPER

To fabricate Cu-TiB2 composite materials for electric and heat conduct ive applications, the direct synthesis of TiB2 in liquid copper has be en considered. Different types of precursors consisting in Cu-Ti alloy s or mixtures of elemental powders were used in combination with boron to form the starting reagents. Differential thermal analysis results show that the TiB2 forming reaction proceeds from an incipient liquid phase formed at a temperature and with a composition that depend on bo th the concentration of titanium in reagents and the type of precursor s used, Cu-Ti alloys or elemental powder mixtures. Whatever the heatin g method is (electric arc or resistance furnaces), the reaction produc ts contain only Cu and TiB2 and the titanium concentration within copp er is below 1%. Because the forming reaction is highly exothermic, the concentration of titanium within reagents should be limited to 27 wt. % to avoid excessive copper vaporization. Therefore, the maximum volum e content within Cu-TiB2 composites could not be higher than 55%. To o btain small crystal sizes and to limit their growth, a temperature clo se to the temperature of formation of TiB2 is recommended.