| 摘 要： | 1 Results and Discussion Nanopowders were synthesized by using microwave plasma synthesis technique.The microwave plasma was operated in atmospheric pressure at a frequency of 2.45 GHz.The reaction temperature is directly related to the power of the microwave generator that can be controlled by adjusting the actual operating current.Firstly,ionization and dissociation of precursor species will be occurred in the plasma,nucleus can then be formed by the collision of these molecules,followed by the growth of the nuclei by further collisions.Cooling gas was used to quench the as-synthesized particles in order to inhibit further particle growth,the products will then condensed in the heat exchanger and finally collected in the powder collector. The synthesis of metal nitride,metal oxide,metals1] and metal alloy nanopowders using the microwave plasma unit was investigated,and the effect of various processing parameters such as the effect of plasma gas,carrier gas,cooling gas,precursor raw materials and feeding rate was systematically studied.Modification of the microwave plasma unit by installing a second precursor dosing device at the lower portion of the reaction chamber can be used to form core-shell structure nanopowders2].The processing conditions can be tuned to manipulate particle size and particle size distribution of the nanopowders.Experimental evidence suggested that the effect of feeding rate,plasma gas,carrier gas and cooling gas was critical in controlling the particle size and particle size distribution during the microwave plasma synthesis.
|
