The Preparation Of Micro Spherical Powder By Centrifugal Atomization Of Mono-sized Droplets

pherical powders are widely used in electronic packaging,semiconductor integratedcircuits,new energy sources and especially in 3D printing.In which excellent properties of powders such as high sphericity,small particle size,narrow diameter distribution are required.The traditional preparation methods of spherical powder mainly include Gas Atomization Method,Rotating Electrode Atomization Method,Rotating Disk Centrifugal Atomization Method and Pulsated Orifice Ejection Method(POEM),etc.These methods have their own advantages and disadvantages.At present,the preparation technology of spherical powders in our country is relatively backward and the high quality micro-spherical powder is mainly dependent on imports.Therefore,it has great significance to develop a new technology for the preparation of spherical powders with small size,narrow size distribution and controllable particle size.Mono-sized Droplets Centrifugal Atomization Method is a noval technology for preparation of spherical powder developed by our team.The technology combines Pulsated orifice ejection method with centrifugal atomizing,the uniform liquid droplets prepared by Pulsating Orifice Ejection Method are dropped on the rotating disk,and form a liquid film,which is broken into smaller droplets because of the centrifugal force by the high speed rotating of disk.The droplets become spherical due to the surface tension and finally solidified into spherical powders during dropping.On the basis of the POEM,a centrifugal atomizing device was added to complete the construction of the droplet atomizing equipment for mono-sized droplets.The effects of melt temperature,rotation speed,rotating disk size and the structure of rotary disk on powder preparation and powders size distribution were studied.It is found that the average size of powder decreases with the increase of rotating speed of the disk and melt temperature;The narrow powders size distribution is obtained with the higher rotating speed of the disk and the relatively lower melt temperature;The morphology and sphericity of powder are greatly influenced by the melt temperature and rotation speed,the higher the rotational speed,the smaller the powder size,the better the sphericity and better surface appearance are obtained;Disk shape also has a great influence on powders size distribution,two kinds of powders size distribution can be obtained with convex and concave rotary disk by controlling theexperimental parameters,and the powders size distribution is narrower with plane rotary disk.At the same time,the low temperature of the rotary disk has a great influence on the atomization process.Therefore the modified equipment with the use of the induction heating system is introduced,the redesigned rotary disk came into use.This method has broken through the disintegration mode of traditional molten metal,and we have obtained the ultrafine spherical powders with narrow powders size distribution due to the fibrous disintegration,which can only be achieved with the atomization medium of aqueous solution or organic solution.The forming process of fibrous disintegration in molten metal was analyzed and the effect on powder preparation was studied.It was found that the liquid flow width had a good corresponding relationship with the powder size.The powder size could be controlled by controlling the width of the liquid flow;The atomization medium and the surface roughness of the rotating disk also have an important effect on the preparation of the powders.