PRODUCTION OF ZrO_2 REINFORCED MULLITE CERAMICS BY SPARK PLASMA SINTERING AND ISOTHERMAL REACTION

摘要

Mullite-ZrO_2 reinforced ceramics have been prepared by a two step method.The first step involves the sintering at 1420 deg C by Spark Plasma Sintering(SPS)of a mixture of alumina and zircon.The second step allows nearly full reaction in the body by an Isothermal Reaction(IR)treatment at 1550 deg C for 120 min in an electric furnace.After the SPS process the sample reaches 99.5 % relative density,but only 24 % mullitization.The IR treated sample achieves 98.5 % relative density and 90 % mullitization.An expansion of 9.22% during mullite formation results in microcracking of the sample when IR treatment is carried out.However,the fracture toughness of the final product is 4.36 MPa centre dot m~(1/2),which is an improvement with respect to the values obtained for mullite-ZrO_2 ceramics in other works by a two step method.Therefore,if a mullite-ZrO_2 reinforced ceramic with high density > 98% and full reaction is prepared,higher fracture toughness can be obtained.