Carbothermal synthesis of zirconium diboride (ZrB2) whiskers

In the present investigation, carbothermal synthesis technique is used for the production of ZrB2 whiskers. The synthesis is carried out by heating the mixture of ZrB2, H3BO3 and carbon black over the temperature range of 1300 to 1700 degrees C in argon atmosphere. Different elements such as Ni, Co and Fe are tested for their role as catalysts. The synthesised powder contains ZrB2 as the major phase with minor phases of ZrC and B4C. Whisker yield is found to be low at lower temperatures (<1500 degrees C) and then increases with the pyrolysis temperature. The Ni addition seems more effective as a catalyst than Co or Fe. Shorter length whiskers are found in the case of Co catalyst, whereas use of Fe catalyst shows whisker with rod shape and a special bird's nest type whiskers. The electron microscope study of whisker reveals the presence of various defects.