TiC/Si_3N_4导电陶瓷复合材料的制备

The Preparation of The Electrically Conductive TiC/Si 3N 4 Ceramic Composites

通过气压烧结工艺制备了含１５，２０，２５，３５ｗｔ％ＴｉＣ的Ｓｉ３Ｎ４陶瓷复合材料，研究了其导电特性。该复合材料由充当绝缘体的Ｓｉ３Ｎ４和作为导电添加剂的ＴｉＣ组成，其电阻率主要取决于其中的ＴｉＣ含量。复合材料的渗流阈值Ｖｃ为１６４５～１８５０ｖｏｌ％，当ＴｉＣ含量达到或超过该阈值时复合材料中就形成导电通路，电阻率迅速降低。通过控制ＴｉＣ的加入量可以制取不同电阻率的ＴｉＣ／Ｓｉ３Ｎ４复合材料，当其中ＴｉＣ的加入量达到或超过２２～２３ｗｔ％时，该复合材料电阻率降至０．１２Ω．ｍ以下，就能进行放电加工。

The electrically conductive ceramic composites TiC/Si 3N 4 with 15,20,25,35wt% TiC powder have been fabricated by gas pressure sintering and their electrical conductivity has been investigated. The composites consist of Si 3N 4 as an insulating matrix and TiC as electrically conductive additive.The electrical resistivity of the composites mainly depends on the content of TiC.The electrical conductivity accords with the percolation theory.The percolation threshold Vc of the composites is about 16.45～18.50vol%(Vc),i.e.,an electrical conduction path is formed by adding more than 16.45vol% TiC in the composites,and the electrical resistivity decreases sharply.TiC/Si 3N 4 composites with different electrical resistivity can be fabricated through adjusting the content of TiC of the composites.When the content of TiC reaches 22～23wt%, the electrical resistivity of the composites decreases to 0.12Ω.m or lower so that the ceramic composites can be machined by discharge.