脉冲放电高能转化制备纳米粉体

综合介绍了脉冲电流通过细金属丝放电(pulsed wire discharge,PWD)制备纳米粉体的方法.讨论了影响纳米粉体,特别是晶粒尺寸的因素,以防止形成亚微米颗粒.因为达到电压峰值的丝的沉积能相当于丝的汽化能,因此,能夠计算出沉积能.随着所施加的能量增加,气体压力降低,介质气体的热扩散率增大,晶粒尺寸变小.在惰性气氛中,采用PWD工艺,由金属蒸气急冷可制备金属粉体.如果介质气体变为氧气或者氨气,就能制备氧化物、氮化物纳米粒子.要制备双金属合金、双氧化物或氮化物纳米粒子就必需采用双金属丝和不同的介质气体.采用PWD工艺,在有机气体或烟气中,能制备电磁屏蔽和导电浆料和其它用途的钝化纳米粒子.采用丝输送器而实现大量生产纳米粉体的PWD工艺一个实例证明了PWD工艺生产纳米粉体的可行性.

NANOSIZED POWDER PREPARATION WITH HIGH ENERGY CONVERSION EFFICIENCY BY PULSED WIRE DISCHARGE

A method for preparing nanosized powders by the pulsed wire discharge (PWD) method utilizing a pulsed electric current going through a thin metal wire is described. Factors that affect the properties of the nanosized powders, in particular the grain sizes of nanosized powders, are discussed to prevent submicrometer grain formation. Since the energy deposited on a wire up to the voltage peak coincides with the energy for the evaporation of the wire, the wire was almost completely evaporated by the peak. With the in-crease of the charged energy, and the decrease of the gas pressure or increase of the thermal diffusivity of the ambient gas, the grain size decreases. The metal powder can be prepared by the cooling of metal vapor in the PWD process in inert gas. If the ambient gas is changed to oxygen or ammonia, oxide or nitride nanoparticles can be synthesized. For the preparation of binary alloys, double oxides or nitrides, it is necessary to use two different metals and different gases. By using the PWD method in the organic vapor/fume, pas-sivated nanoparticles for electromagnetic shields, conductive pastes and other applications can be prepared. The example of pulling a wire feeder for a large-scale production of nanosized powders by PWD shows the effectiveness of PWD for the preparation of pas-sivated metal nanosized powders.