Co-sintering Preparation Of The Metal-ceramic Lamellar Composite With Positive Temperature Coefficient

The Metal-ceramic lamellar composite is a novel non-fire，low-temperatureheating element which resistance present positive temperature coefficientcharacteristic with the temperature changes．Due to its unique properties， TheMetal-ceramic is widely used in many fields，such as the daily life，medical，communications，industrial and agricultural．However，The resistance of the heatingmaterials increase slowly with the temperature rise，Which result in the heatingelement thermostatic temperature reaches800-1000℃． The high thermostatictemperature is unsafe which limits its Application．Therefore，The preparation of theheating element with the low thermostatic temperature is very meaningful toexpanding its applications．In this study，several methods were used such as Archimedes Density Test，Thermo gravimetric analysis（TGA）test，Optical microscope（OM），High voltageleakage current test，Resistance-Temperature characteristic test of the materials．Byadjusting the ingredients and preparation，The heating material was elected and TheFormula and Sintering aids of Alumina were determined． In addition， Thepreparation of metal-alumina ceramic was successful under laboratory conditions．Studies of the heating materials show that tungsten and molybdenum with highmelting point，and ferromagnetic materials with low melting point were suitablematerials．The test of material properties show that tungsten can reduce the finalcurrent of heating element slightly． Theoretically， the curie transition offerromagnetic material was present，which can enlarge the change of resistance．Bytesting Resistance-Temperature characteristic of the materials， Ferromagneticmaterials can replace the heating material．The test result showed that300℃，600℃，900℃，The change of resistance were2.14times，5.43times and11.48timesrespectively．In order to make the melting point of the Ferromagnetic materials and aluminasintering temperature matches，sintering aid was used．The alumina with averageparticle size of2μm added1wt%TiO2and0.5wt%CuO could achieve good performance after sintering at1450℃．The study on sintering aid of alumina showedthat the relative density of95%and leakage current Less than1.5mA of aluminacould meet the requirements of the product．At later stage of the experiment，Metal-Ceramic green tape were prepared withproduction process of factory by using ferromagnetic materials as heatingmaterials． The Co-Sintering process was also investigated under laboratoryconditions．The Co-Sintering process including heating rate，sintering temperature，holding time，The temperature of the mixed gas，the holding time of the mixedgas．The result indicate that the heating rate of3-5℃/min，sintering temperature of1450℃，holding time for120min, the temperature of the mixed gas select at900℃，the holding time of the mixed gas for10min was the optimum process．Theappearance and performance of the sample with the above-described processsintering seemed to be the most suitable．Comparative Experiment showed that themagnitude of the resistance change of the sample prepared in the laboratory was30%-70%bigger than that of product prepared in the factory．The result also showsthat ferromagnetic materials replace heating materials is effective．...