Designing And Manufacturing A Mechanical Milling Device Assisted By Electrical Discharge And The Study Of Thick Film ZnO Varistors

This paper inclue two parts,the first part is that the detailed introduction of how to make a mechanical milling device assisted by electrical discharge and the working principle of this device.The second part we detailedly introduce the study of thick film ZnO varistors.mechanical milling assisted by electrical discharge is the application of lowcurrent, high-voltage electrical impulses during milling,and it will produce arc or glow discharge phenomenon in the milling chamber.It have been proved that mechanical milling assisted by electrical discharge can result in both faster reactions and new synthesis and processing routes comparing with traditional mechanical milling.Glow discharge milling was found to promote solid-gas reactions whereas spark discharge milling promotes fast solid-solid reactions.We don't see any literature about mechanical milling assisted by electrical discharge in our country till now,so we designed and manufactured a high-speed vibrational milling device assisted by electrical discharge,and detailed describes the structure,working principle of this device.ZnO varistors with highly nonlinear voltage-current coharacteristic,excellent surge withstanding capability and wide range working stability are employed to protect electrical circuits in the fields of electrical and electronics.And the research to manufacture ZnO varistor with high voltage-gradient has attracted lots of attention both at home and abroad,and has prominent meaning in the future too.The results show that it is an effective method for acquiring better electrical properties that the powder were milled for 5h in ethanol.The crystallite size of the constituent oxides were refined to 43nm,the average particle size was 0.605μm and the powder more pure(Fe%=0.78wt%).In the experiment,ZnO varistors is several layers of thick film(100um～200um),because of doping Y₂O₃ and high energy mechanical milling and low temperature sintering,the crystal size of thick film ZnO varistors is very small,which will induce thick film ZnO varistors have high voltage gradient.Our sample is sintered at 700℃for 30min～90min:the leakage current is less than 50uA,the nonlinear coefficient is more than 12,the voltage gradient is more than 2000V/mm.With the time prolonging and temperature increasing,the voltage gradient is reduced obviously,and nonlinear coefficient ofâ… -â…¤is declined too.