| On the base of reviewing many kinds of preparation method of nano metal powder materials, some nano metal powders such as Ni, Cu, Fe, Zn were prepared by plasma method, which has many excellent characteristics such as high purity, small average granularity (about 40nm), narrow distribution of granularity (from 10nm to 100nm), little loose density (from 0.1 to 1 g/cm-3) and few conglomeration. Not only were technical parameters of preparing nano powder by plasma method for some kinds of metal materials optimized, but also the whole preparation process was studied fully and systemic from multi-aspect as follows: the quality controlling factor (temperature gradient) and its inner mechanism, the quantity controlling factor (preemptive molecule vaporizing within hydrogen bubble) and its inner mechanism, the powder collection controlling factor (heat flow excursion of nano particles in the non-equivalent temperature field) and its inner mechanism. The performance of special lubricating oil for gas engine was improved by nano copper powder, which was prepared by plasma method, which achieve the level of relevant import products.The temperature gradient request for obtaining nano particles is met by plasma non-confined arc, compulsive air current conveyance and air-cooling, which avoids complicated equipment requirement for liquid nitrogen & confined plasma arc and reduce cost greatly. On the other hand, the high pure hydrogen is imported to improve productive efficiency remarkably. The influence rule to powder quality and quantity from some technical parameters such as materials vapor tension, gas pressure, the ratio between hydrogen and argon, current intensity and gas circulate intensity were discussed by single-factor experiment, on the base of which the perpendicularity experiment scheme was arranged. At last, the best optimized preparing technical scheme for some kinds of nano metal materials were studied.The conclusion that the environmental temperature of reactor is below 373K is obtained by calculation on the base of pressure module, whereas the temperature of plasma arc axis is about from 5000K to 6500K by calculating current density and conductive rate. So the gradient within the scope of special radius of plasma arc (about 1.26cm) can achieve 4787K/cm even without external compulsive cooling condition, which is the concrete representation of high concentrated distribution for plasma temperature field. The essential cause of preparing nano metal powder without cooling from liquid nitrogen is at this point. That is to say, the controlling mechanism of guaranteeing the metal particles in the scope of nano dimension is just the great temperature gradient of plasma arc.The preemptive molecule vaporizing within hydrogen bubble is put forward to interpret the cause why hydrogen can improve the productive efficiency greatly. The mechanism explains the influence law from several phases such as break of hydrogen molecules, action of plasma cathode current, carrier function of hydrogen bubble for fusible metal molecule vaporization and escape of hydrogen bubble. Hydrogen bubble as molecule vaporizing carrier unit not only enhances the unit productive rate, but also improve the effective vaporization acreage. At the same time, the mechanism explains the contradiction between classic metal vaporization theory and experimental data on the influence of gas pressure.Heat flow excursion mechanism is controlling factor for conveyance of nano particles in the non-equivalent temperature field. When particle dimension reduce to 100nm, the Heat Flow Excursion Force is 548 times as much as gravity and 220 times as much as Magnius rinsing Force. So the sedimentation mode of nano particles changes from gravity sedimentation to heat flow excursing sedimentation, whose characteristics is opposite to routine gravity sedimentation. The mechanism explains the abnormal question in the course of collection nano powder, and supply academic foundation for gas current collection equipment.The performance of special...
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