The Development Of Equipment For Preparing Metal Nanoparticals By Electrical Explosion

Metal nanoparticles with the special properties such as volume effect,quantum size effect,macroscopic quantum tunneling effect,has a wide range of applications in aerospace,electronic information,medicine and other fields.Metal wire electrical explosion have the advantages of simple production process,no pollution to the environment,high purity of nanometer particles so that it's considered to have a good development prospect for the industrialized preparation of metal nanoparticles.However,there are still some limitations in the development of equipment for preparation of nanoparticles by metal wire electrical explosion,which still needs further study in order to realize the industrialized production.On the basis of the present research results,the equipment for the preparation of nanoparticles by wire electrical explosion with filament with diameter of about 0.2mm or 0.1mm is developed.The metal wire is held on the hub made of the ablation material,and the wire segment is continuously feed into the electric field by the hub rotation so that to realize the nanoparticles pr epared by the wire electrical explosion.The transmission mechanism can change the position of wire on the hub up and down,during the explosion,so that to disperse the ablation,shock and other damage,and the ablation material can cool the plasma.Both of them make the wire feeding mechanism's life longer.In order to produce the large amount of nanoparticles by electrical explosion,the nanoparticles collecting device which uses the brush roller to adsorb the nanoparticles was developed.The working eff ect of the collecting device shows that the nanoparticles collecting device has obvious effect on atmosphere purification of the chamber during the process of electrical explosion,can ensure the electrical explosion not interfered by the prepared nanopart icles with the equipment working for a long time.The device has a simple process to collect the nanoparticles,and can acquire the nanoparticles directly,but the collection quantity of nanoparticles is close to manual dusting collection quantity.The equipment uses the trigger tube as the high-voltage circuit switch,in order to meet the requirement of the equipment,three kinds of high-voltage circuit's conductive structure was developed.Taking the electrical explosion experiment under each conductive structure,analyze the experiment phenomenon and the electrical signal of the discharge circuit,the results showed that: When the surface distance between the high-voltage conductor and the grounding conductor is short,the discharge phenomenon will occur along the surface,called creepage.Insulating the conductor surface,and make the insulating part into a structure of anti-climbing electric skirt,can increase the creepage path,then prevent the creepage happening.When the inductance of the electric explosion circuit is large,the high-frequency oscillating current signal is generated in the circuit,which affects the observation of the electric explosion process.Using the coaxial structure,the inductance of the conductor can be compensated by mutual inductance,and reducing the conductor length also can reduce the inductance,so that the inductance of conductive structure can be reduced to eliminate the high-frequency oscillation signal in the current waveform.In addition,when the trigger tube is t riggered,its current signal is superimposed with the loop current signal,which interferes with the initial change signal of the electric explosion circuit current.Using the developed equipment to conduct experiment of nanoparticles preparing at different initial charging with three different metal wires of molybdenum tungsten and nickel,The nanoparticles were observed by transmission electron microscope,and the size of nanoparticles were calculated by transmission electron microscope photo.The energy deposition density of metal wire in electric explosion process is estimated by the current and voltage waveform.The results show that with the increase of the energy deposition density of the metal wire,the particle size is decreased and the particle size distribution is more concentrated,but the change trend will decrease gradually.Reducing the diameter of metal wire at the same voltage will make the particle size of the nanoparticles decrease obviously.Molybdenum wire in the case of no trigger tube control,during the electrical explosion process wire surface occurred bypass action and generate a large current gas breakdown,the energy deposition is low,the size of the nanoparticles is larger and the particle size distribution is not uniform;Because of the low melting point and small resistance of the nickel wire,it averted the appearance of large current discharge during the explosion.So that the nickel nanoparticles were prepared with the average grain size of 20nm~30nm;The tungsten wire was pre vented from the large current gas breakdown during the explosion,with the position of explosion controlling by trigger tube,it can be made into nanoparticles with the average grain size of 20.5nm.