Ni/PTC陶瓷复合材料的制备和性能

采用液相包裹法由NiC2O4·2H2O/BaTiO3前躯体热分解制得Ni/PTC陶瓷复合材料,并对其结构和性能进行了表征.Ni/PTC陶瓷复合材料具有多孔性结构和较好的分散性,Ni主要以微细金属颗粒的形式分布于晶界和孔隙中;在Ni/PTC陶瓷复合材料中氧化Ni导致室温电阻率增大,对PTC效应产生消极影响;采用石墨扣烧的方法能避免金属Ni氧化,制得的Ni/PTC陶瓷复合材料具有非常低的室温电阻率,但几乎失去了PTC效应,在烧成后热处理过程中晶界氧的吸附可使其恢复PTC效应;Ni/PTC陶瓷复合材料结构的多孔性和金属Ni的充分分散有利于PTC效应的恢复.

Preparation and properties of the Ni/PTC ceramic composite

In order to decrease the room-temperature resistivity of PTC materials, Ni/BaTiO$_{3}$ composite was synthesized by decomposition of NiC$_{2}$O$_{4}\cdot$2H$_{2}$O/BaTiO$_{3}$ precursor, which was prepared by precipitating nickel oxalate into BaTiO$_{3}$ suspension. Structure and property of the composite were investigated. The results showed that the composite has a porous and uniform structure. Nickel was dispersed in grain boundary and cavity in the form of fine particles. Oxidation of nickel would induce high room--temperature resisitivity and spoil PTC effect. It can be avoided by protection of graphite during sintering. The sintered composite has a very low room--temperature resistivity and little PTC effect. With the absorption of oxygen in grain boundary, PTC effect of the Ni/BaTiO$_{3}$ composite can be effectively renewed by heat--treatment in air. The porose structure and the fine dispersal of nickel were in favor of the renewing of PTC effect.