Online Coated The Surface Of The Metal Nano-materials Research

In the inertial confinement fusion (ICF), target materials need doping with metal nanoparticles. Nanoparticles are often oxidized or aggregate with each other when exposed to air. This could lead to oxygen atoms into the targets materials and non-uniform distribution of nanoparticle dopants. To solve the question mentioned above, researchers have developed a technique to on-line coat nanoparticles during preparation. Aiming at the actual need, this thesis concentrates on fabricating metal nanoparticles by the flow-levitation method, on coating metal nanoparticles with carbon-and-hydrogen(CH) or carbon(C) films by the hollow-cathode glow discharge, magnetic sputtering and heat evaporating, as well as on on-line coating nanoparticles on NMP-I apparatus.In the case of synthesizing metal nanoparticles by the flow-levitation(FL) method, in principle, the solid metal is firstly heated by a highly-frequency electromagnetic induction coil so that a metal liquid droplet is formed. The droplet is levitated and heated continuously under its interaction with the magnetic field generated by another reverse electromagnetic induction coil. Atoms at the surface of the droplet are evaporated when a high-enough temperature is reached. These evaporated atoms are quickly cooled through their collision with the inert gas and form clusters. When the inert gas with a special gradient pressure is imposed in the vapor environment, metal atoms and resultant nanoparticles can flow in a definite direction in no contact with the reactor wall and finally enter the collector. The size distribution of nanoparticles synthesized by the flow-levitation method is determined by several factors such as the velocity of supplying resource materials, the diameter and temperature of the metal droplet, the flow velocity and pressure of the inert gas. To understand the physical principle and process of fabricating nanoparticles by the high-frequency-induction heating a metal wire in the FL method, the force acted on the metal liquid droplet was analyzed and calculated on the basis of the electromagnetic field theory. The theoretical results indicate the condition that makes the metal liquid droplet suspend in the middle of tow reverse coils, consistent with the experimental fact.In order to accomplish on-line coating nanoparticles, nanoparticles synthesized by the FL method enter directly a chamber, in which carbon-and-hydrogen (CH) plasma produced by a hollow-cathode glow discharge (HCGD) is sprayed onto the surfaces of nanoparticles to form organic films. To understand the technology parameter of on-line coating nanoparticles by FL method, some key questions about on-line coating nanoparticles have been analyzed. As the first step, coating nanoparticles was performed only after the process of synthesizingnanoparticles had been completely finished. Through the two distinct steps, the sedimentation rate of CH coating can be definitely obtained. Organic coating is polymerized on the surfaces of nanoparticles. The results show that the surfaces of copper nanoparticles get miscible well with the organic-coating layer and that the coat thickness is determined by several factors such as the applied voltage, the gas flux, and the working time. These parameters are very useful for on-line coating nanoparticles.As an alternative way, we have tried to prepare and on-line coat metal nanoparticles by magnetron sputtering. Carbon film was grown on the surface of crystal salt in vacuum chamber. Then metal nanoparticles were deposited on top of carbon film. Lastly, another layer of carbon film was grown to coat metal nanoparticles. The experiments indicate that the diameter of copper nanoparticles with poor dispersion ranges from 10 ran to 100 nm with the average diameter of 35 nm. The experiments indicate that it is a good method to on-line coat nanoparticles. Subsequently, according to the same thought, metal nanoparticles were prepared and on-line coated with organic film by heating evaporation. The results show that nanoparticles with an average diameter of 25 nm were dispersible and coated completely by the CH films. Finally, we designed a device to sandwich metal nanoparticles produce by the FL method with two layers of organic films. The results show that there are some questions such as the choice of organic materials, the stability of the inert-gas flux into coating chamber, the dispersion of nanoparticles. This question should be solved in future.