| Nanometer materials applies in various research fields and different disciplines and occupies a pivotal position,which has been found since the 1980s.In the innovation area of new materials,it also has played a more crucial role.With the rapid development of society,new materials are widely used in all walks of life instead of the traditional materials.However,limited by current condition of science and technology,there still are some problems needed to solve about nanomaterials,such as,van der Waals force is objective which leads to the aggregation of nanoparticles.Separation and purification of these nanoparticles is difficult in nano-meterscale and is a major problem for the scientists in the field of nano-technology.Van der Waals force includes Keeson force,Debye force and London force,which is the main reason causing the aggregation and reunion of nanoparticles.In this paper,van der Waals potential between molecules or atoms is analyzed.Based on van der Waals potential between two moleculars,the calculation formula of van der Waals potential between the molecular and the infinite body,van der Waals potential between the ball and the infinite body,van der Waals potential between two infinite body and van der Waals potential between the ball and ball are derived.In this paper,separation of two SiO2 nanoparticles interacted by van der Waals force is researched.As a kind of non-contact separation method,ultrasonic separation method would not contact with separation of particles,can achieve continuous operation compared with other separation methods.Nanoparticles will not be damaged or contaminated which might affect the characters of nanoparticles.Applying ultrasonic vibration to one of particles in air medium or water medium.The interaction,displacement and distance changes between two SiO2 nanoparticles are calculated.The effect of all parameters including ratio of diameterη,amplitude of ultrasound H,period of ultrasonic T and the average energy density of ultrasonicζare researched It’s found that separation of two nanoparticles in air medium is faster than in water medium,and the parameters above have different influences on separation.Selecting appropriate value of parameters can realize optimization of separation. |
