Preparation And Properties Of Al-Si-C Closing Resistor

Aluminum-silicon-carbon(Al-Si-C)closing resistors have superior properties such as low resistivity,small temperature coefficient of resistance,low cost,and simple preparation.They are mainly used for power system neutral contact resistance and breaker closing resistance.At present,the performance of the Al-Si-C closing resistor on the market has not yet reached the practical application requirements,the heat treatment process is complex,and there is no research to reflect whether the electrode material has an effect on the performance of the resistor.This paper systematically studies the material formulation,the sintering process and the electrode materials of Al-Si-C closing resistors.The main research content is as follows:1.In order to study the influence of the formula on the performance of the Al-Si-C system closing resistor,the effects of different graphite content,kaolin content and alumina content on the micro structure and electrical properties of the Al-Si-C system closing resistor were studied.The experimental results show:when the graphite content exceeds 15%,a good continuous conductive path was formed inside the closing resistor material,and the electrical properties were excellent.But,if the graphite content was too high,the strength of the resistor chip was reduced,so the graphite content should be controlled at 15～40%;In addition,the content of kaolin should be controlled between 35%and 60%,and the content of Al2O3 should be controlled at 20%.The resulting Al-Si-C closing resistor had a high density,and its electrical properties could meet the requirements of practical applications.The resistivity was 1.2～5 Ω·m,the temperature coefficient of resistance was-0.5～-0.16%/℃,the actual density was 2.2～2.4 g/cm3.Selecting the Fe2O3-containing composite additives could effectively reduce the electrical resistance of the sample and improve the thermal stability of the sample resistance and the best content was 2%.2.In order to study the influence of the sintering process on the performance of the Al-Si-C closing resistor,we studied the effects of sintering atmosphere(air,N2,Ar/H2 atmosphere)and the sintering temperature(1200℃,1300℃,1500℃)on the microstructure and electrical properties of Al-Si-C closing resistors.The experimental results show that at 1200℃,because the graphite would oxidizes if it sintered in the air,the resistivity of samples sintered in N2 was significantly lower than that in air.But,under the protection of N2 atmosphere,there was still a small amount of graphite being oxidized.Therefore,an Ar/H2 atmosphere with an H2 content of 4%was selected for practical experiments.In the Ar/H2 atmosphere,the higher the sintering temperature was,the higher the actual density was and the lower resistivity was.But considering the energy consumption,cost issues and experimental conditions,the actual experimental sintering temperature was set at 1400℃.3.In order to study the effect of electrode materials on the performance of Al-Si-C closing resistors,we studied the effects of silver paste electrode and sputtered aluminum electrode on the performance of Al-Si-C closing resistors.The experimental results show that the sputtered Al electrode was more uniform and thinner than the calcined Ag electrode on the sample surface.The Al-Si-C closing resistors that sputter A1 electrodes could reduce contact resistance between electrodes and closing resistors more effectively than Ag electrodes which were calcining in N2 atmosphere,so that the resistance performance of the Al-Si-C closing resistor was improved..Its resistivity was 1.66～2.14 Ω·m,and the temperature coefficient was-0.27～-0.11%/℃.