Preparation Of LaSrCuO₄ And Hot Extrusion Process Simulation Of Ag-based Electrical Contact Materials

As a core component of electrical components,the electrical contact material is a key factor that affects the ability to switch off electrical conversion at service time,reliability and service life.Electrical contacts in the process of long-term service is state in opening or closing,so higher properties of the contacts should be strictly needed,such as good conductivity,welding resistance,resistance to abrasion resistance,low contact resistance,etc.Ag/CdO electrical contact material is known as a“universal contact”and has been widely and long-term used,but prohibited by the EU directive due to the toxicity of Cd.The research of Ag/SnO₂ and other new electrical contact materials has been rapidly developed,but it has been found that higher contact resistance and molding difficulties of Ag/SnO₂ electrical contact materials took place in the further application process then it hindered the continued application of this material.Therefore,the development of the new electrical contact materials with superior performance has become a hot topic in the field,and a silver-based conductive ceramic composite material has been an important direction.LaSrCuO₄ powder was prepared by sol-gel method and the effects of process parameters such as the molar ratio of citric acid?CA?to ethylene diamine tetra-acetic acid?EDTA?,pH and sintering temperature on the morphology and phase of the LaSrCuO₄ were researched.Surface morphology and phase were characterized by Scanning Electron Microscope?SEM/EDS?and X-ray Photoelectron Diffraction?XRD?.Using DEFORM-3D simulation software to simulate the extrusion process,the impact of extrusion speed on the temperature distribution,metal flow velocity distribution,extrusion pressure in the blank and the temperature distribution,equivalent stress distribution in the mold were researched.The main contents and conclusions are as follows:?1?LaSrCuO₄ conductive ceramic with mesoporous morphology were prepared by the sol-gel method:?a?The powder agglomeration was serious at T_s=800??T_s=sintering temperature?but better dispersed powder was obtained when T_s?900?or above it.?b?Lamellar structure was observed at pH=9 and T_s=1000?and mesoporous structure when pH=9 and T_s?1000?or pH=8 and arbitrary sintering temperature.?c?The addition of EDTA could improve the crystallization performance,it can promote the growth of LaSrCuO₄ phase and inhibit the growth of La₂SrCu₂O₆phase in the crystallization process,which may be one of the main sheet of the layered structure disappeared.?2?Extrusion process of Ag/LaSrCoO₃ electrical contact materials was simulated by DEFORM-3D software,exploring the impact of extrusion speed on billet and die:?a?The billet temperature was decreased with extrusion progresses at 5mm/s rate of extrusion.Billet temperature was rising and eventually fluctuated up and down in a stable value at 10mm/s or above rate of extrusion.?b?The higher the speed extrusion,extrusion pressure was lower,while the metal flow was faster.?c?With the increase of extrusion speed,the temperature of mold deformation zone was raised,but the equivalent stress was decreased.