Study On Preparation And Performance Of Ag/YAG Electrical Contact Material

Silver-based electrical contact materials are widely used in low-voltage electrical appliances,which is one of the most important foundation for the people's livelihood Among them,silver oxide(Ag/MeO)electrical contact materials with excellent thermal conductivity,electrical conductivity,anti-welding properties and mechanical properties ate the most common electrical contact materials.Ag/CdO,known as the"universal contact" has strong anti-arc corrosion resistance and low resistance.But Ag/CdO electrical contact materials have harmful to the environment and the users because of cadmium vapor.The development of environmentally friendly silver-based electrical contact materials is imminent.Yttrium aluminum garnet has high thermal conductivity,high melting point,good mechanical properties and stable physical and chemical properties,which make it a good potential reinforcing phase for silver-based electrical contact materials to replace CdO.In this thesis,many attempts have been made to study the preparation and modification of yttrium aluminum garnet(YAG)reinforced phase powder and its properties of Ag/YAG electrical contact materials.The main research contents and conclusions are as follows:(1)Pure phase YAG powders were produced when calcination temperature of dried precipitate precursor reaches 950 0C,using ammonium bicarbonate as precipitating agent.After the investigation of various factors,it was found that when the concentration of metal ions was 0.1 mol/L,the concentration of NH4HCO3 was 1.5 mol/L,the sintering temperature was 1000 ?,and the surface modifier was CTAB,nano-sized YAG powders with good dispersion were produced.(2)Yttrium aluminum garnet powders were prepared by sol-gel method with hexamethylenetetramine as catalyst.It was found that when the water bath temperature was 50 ?,xerogel sintering temperature reached 950 ?,pure phase YAG powders were prepared.The amount of hexamethylenetetramine addition had no effect on the final phase of the powder,but had great impact on the morphology of powders.The results showed that YAG powder with good dispersibility could be prepared when water bath temperature was 50 °C,hexamethylenetetramine dosage was 2.8 g,sintering temperature was 950 ? and surface modifier was CTAB.(3)The electrical life testing machine was used to test the electrical life.For both Ag/YAG(co)and AgAYAG(Soi-gel),the influence of current and service cycle were explored.After research,it is found that with the increasing of current and service cycle,the range of arc area increases.And Ag/YAG(sol-gel)has stronger resistance to arc erosion than Ag/YAG(co).In the conditions of welding,the surface of AgAYAG(sol-gel)has such phenomena as quasi-fracture morphology,skeleton-like structure,clusters,pores,droplets,protrusions and YAG enriched zones.On the surface of AgfYAG(co),there are aggregation of spherical Ag and more obvious droplet splash and protrusions.