Study On Preparation Of Nano Tungsten-copper Composites

The well combination of copper of preeminent conductivity and Tungsten of high-temperature strength and arc-resistant leads a serial of preeminent properties. Tungsten-copper materials are usually made electric contracts, electronic seal, thermal materials. Because Tungsten and copper do not dissolve each other, the preparation methods of W-Cu composite material prove particular. And as nanoparticles manifest some unusual properties and intensive activity, the preparation methods of nano Tungsten-copper composite material is more particular.The thesis adopts powder-preparation, powder-admixture, pressing, sintering to prepare Tungsten-copper composite material and studies the effect of atmosphere, electric current and rotational speed of fan on productivity and grain size. The effects of powder property, sintering gas atmosphere, sintering temperature, the anti-friction material, the rate of heating-up and pressure on the performance of sintered body are also studied in the thesis.Due to the research of the preparation of nano copper powder, thethesis discoveries: The gas atmosphere of N2—Ar is better than that of H2—Ar in increasing productive rate and safe. The grain size of the powder is less than the wavelength of visible light. The grain size of nano copper which we produce is about lOOOnm. Their appearance is nearly spherical. Increasing current intensity can increase the evaporation rate. Then the productive rate of nanometer copper powder is increased, but the grain size will increase at the same time. With the same other test condition, the productive rate of nanometer copper powder is increased at 30% when the percentage composition change from 10% to 15%. With the increase of N2 percentage composition, the particle size distribution of the powder become broad and the average grain size increase. With the increase of fan speed of rotation, the productive rate will increase, the particle size distribution of the powder become narrow, and the average grain size decrease. But the productive rate will decrease with the increase of fan speed of rotation when the speed is more than 2400r/min. The best technological condition to produce nanometer copper powder is the follow: (l)the arc- current is (380 ± 5 ) A;(2)the percentage composition of N2 is (15±2) % in the producing room;(3) the speed of rotation of fan is 2400-2500r/min.According to the research of the formation of nano Tungsten-copper composite material, the thesis discoveries: The effect of powder property upon the performance of sintered body is great. They advantages sintering which are smaller size, more regular appearance and better plasticity. The samples get initiative densification when sintering-temperature is upon 900 °C. But the density will have a wider increase when sintering-temperature rise up to 1000°C. So the samples density is increasing with the rise of temperature. But the temperature has little effect on the density whentemperature rise up to 1350 °C. The rate of heating-up also has an effect on the property of the sintered body. In this test, the rate of heating-up should be between 3-10°C/min. The test sample s density will be increased with extending sintering time. But this effect becomes so little when the sintering time is longer than 300min. The anti-friction material can increase the test samples density. Pressure also has a great effect on the density. The samples heat pressuresintered have higher density than those normal atmosphere sintered.