Preparation And Electrorheological Characteristic Of Anisotropic Particles

Electrorheological?ER?fluids are a suspension system with dielectric particles that can make rapid and reversible rheological response.Compared to the traditional spherical particles,ER fluids based on anisotropic materials have attracted widely attention due to its unique rheological properties.This paper designs and prepares two different particles with anisotropy providing the basis for exploring new phenomenon: one type is 2D nanosheets based on graphene oxide and graphene with anisotropic of morphology,for the purpose of achieving an optimum ER response to different electric stimuli,and another type has asymmetric both in geometric and chemical property,through the improved synthesis method adjusting conductivity of the Janus particle on both sides.The main research contents are as follows:1.We respectively used non-conducting graphene oxide?GO?and conducting reduced graphene oxide?r-GO?as the core and used insulating SiO₂ as the shell to prepare core/shell-structured dielectric nanoplates for the purpose of achieving an optimum ER response to different electric stimuli.The morphology and structure of the samples are characterized by scanning electron microscopy,transmission electron microscopy,atomic force microscopy,X-ray diffraction,thermogravimetric analysis,Raman spectroscopy,and X-ray photoelectronic spectroscopy.The conductivity and dielectric properties are measured by an impedance analyzer and the electroresponsive ER characteristics of nanoplates dispersed in insulating oil are investigated by a rheometer.These demonstrate that coating with SiO₂ can provide an electrical insulating effect for the GO or r-GO core,while GO vs.r-GO as the core can induce distinctly different dielectric polarization responses.Compared to GO/ SiO₂,r-GO/ SiO₂ shows a significantly faster polarization rate due to the high conductivity of the r-GO core.As a result,the r-GO/ SiO₂ suspension exhibits a high ER response to high-frequency AC electric fields,while the GO/ SiO₂ suspension exhibits a high ER response to DC or low-frequency AC electric fields.2.In this paper,two-step seed-emulsion polymerization method has been used to synthesis cross-linked polystyrene microspheres and the polystyrene dimers with geometric anisotropy.In order to obtain the Janus with anisotropic of interfacial further,we modified the dimers with the Au nanoparticles selectively according to literature's method,but on both sides of particles have Au nanoparticles.Therefore,the reaction conditions and order in the process of experiment have been changed.Finally,we have successfully explored the method of preparing the metal-organic hybrid Janus with only one side coated gold particles.That is to modify the amino groups on the CPS microsphere,and then grow into Janus particles,modified the Janus with gold particles at last.The reason relating to this is that the presence of positive charge of amino groups on the one side of Janus,but the other side with negative charge,so the gold particles with negative charge will be fully modified by electrostatic adsorption at only one side of Janus particles.