Fabrication And Properties Of Doped SnO₂-Al₂O₃/Cu Novel Nano-composite Electrical Contact Materials

With respect to the urgent needs of rapidly rising electronics industries for the electric contact materials applied in low voltage electrical apparatus,a novel SnO₂-Al₂O₃/Cu nano composite contact material with low cost and high performance was prepared by adopting powder metallurgy technique,and a systematic investigation and analysis on the basic properties and related mechanisms of the resultant material were also conducted.The study found that TiO2 doped SnO2 nano powders with spherical shape,uniform particle size and good dispersion could be successfully prepared by sol-gel method.Because of the high cost and the low comprehensive performance of the resultant materials of the wet mixing method compared with that of the ball milling method,the latter should be more suitable for the preparation of the nano composite electrical contact material.The orthogonal experiment results showed that the best preparation process of the material should be:the well mixed composite powders were compressed under a pressure of 600MPa and sintered at 940 ^oC for 2 h,and then compressed at 1000 MPa and sintered at 980^oC for 3 h,and finally plastic deformed at 1000 MPa to form the product.Test and analysis on properties of the material showed that,with increasing the total content of doped SnO₂ and Al₂O₃ nano powders the conductivity decreased,while the hardness and wear resistance increased at first and then decreased.When the total content is0.8wt%,the hardness and wear resistance reached their maximum.When the total content of the two kinds of nano powders was constant,with the increase of the content of doped SnO₂,the hardness and wear resistance decreased,while the conductivity increased.Rare earth element Ce could significantly affect the basic properties of materials.With increasing the content of Ce,the softening temperature and the high temperature oxidation resistance capacity increased monotonously;conductivity increased at first and then decreased,and at the content of 0.08wt%,conductive achieved its maximum;when the total content of the two kinds of nano powders was relatively low,the hardness and wear resistance rised monotonously,and when the total content of two kinds of nano powders was relatively high,however,the hardness increased slightly at first and then decreased slowly,and the wear resistance remained nearly unchanged.When the Ce content was0.05wt%,the hardness of the material reached its maximum.Both rare earth element Ce and doped SnO₂ had obvious improving effect on the electrical contact properties.When the total content of the two kinds of nano powders was constant,with the increase of doped SnO2,arc time,arc energy and arc welding force gradually decreased.With increasing the content of rare earth elements Ce,arc time and arc energy decreased at first and then increased,while welding force decreased monotonously.When the adding amount of Ce reached 0.1wt%,the best electric contact property could be achieved.However,with increasing the content of Ce and decreasing the total content of the two kinds of nano powders the contact resistance decreased monotonously.With the increase of rare earth element Ce and total content of the two kinds of nano powders,the electric erosion surface gradually became smooth and uniform,and the degree of molten metal spatter as well as the density of pores and bubbles gradually decreased,i.e.the arc erosion resistance gradually increased.When the content of Ce was more than0.1wt%,the arc erosion resistance would be deteriorated.