Preparation Of Core-shell Structure Nanocomposites And Its Electrorheological Properties

Electrorheological fluid（ER fluid）,as a kind of intelligent materials,has the advantages of fast response speed,adjustable and reversible liquid-solid conversion performance.ER fluid is consisted of dispersed phase,continuous phase and additive,most of the current widely used ER fluids are suspension liquids with complex components.The prepared dispersed phase is dispersed in silicone oil.Under the applied electric field,the dispersed phase particles can be quickly connected into particle columns along the electric field line direction,which can change the turbidity liquids from liquid to solid,thus obtaining a certain mechanical strength.After removing the electric field,the ER fluid will quickly return to the initial state.ER material,as a new intelligent material with rapid response to electric field,has shown great application prospect in electrical control devices,which has attracted more and more attention and application in recent years.Core-shell structure is widely used in ER material due to its special morphology and structure.As the conductive layer,the core material needs to have sufficient conductivity to realize rapid polarization under applied electric field.At the same time,the shape and particle size of the obtained sample can be controlled by adjusting the shape and size of the core material.As the insulating layer,the shell can regulate the electrical conductivity of the ER fluid,which makes the sample have a high penetration-resistant performance.Meanwhile,the shell material with the polarization property combining with the core material can improve the ER performance of ER materials,and the interface polarization generated by the interaction between core materials and shell materials is also very helpful to the ER performance.The amount and type of core materials and shell materials can be adjusted simultaneously,and they can combine with each other according to different properties of various materials,providing a variety of choices and different ideas.We designed and prepared a variety of ER materials with core-shell structure.The experimental contents are as follows:1、Cubic hollow nanoparticles are introduced into ER fluid due to its anisotropic shape.Hollow cubic TiO₂ nanoparticles are prepared by two-step method.First,TiOF₂nano cubic particles are prepared by one step hydrothermal method.Then,according to Oswald Ripening principle,materials inside the cubic particles are precipitated by second hydrothermal method and then forms the hollow TiO₂ nanoparticles.The internal hollow structure can improve the suspension stability of dispersed phase,and it has a larger specific surface area,providing higher interfacial polarization ability.Pure TiO₂ has a minimal leakage current density and can withstand higher breakdown voltage.Through a series of experiments,it is proved that it has strong ER properties.2、Based on the synthesis of anisotropic core-shell nanocomposite particles,use Si O₂ to coat on the TiOF₂ nano cubic particles.Through the same methods,TiOF₂ nano-cubic particles are prepared by hydrothermal method in the first step,and Si O₂ is uniformly grown on cubic particles by controlled hydrolysis method in the second step.TiOF₂ has unique shape of anisotropic nanocube,Si O₂ can regulate the conductivity,and core-shell structure can improve the interface polarization ability of particles.Combined with the above advantages,the ER material with excellent performance is prepared,whose shear stress can reach 100 Pa.3、In order to make full use of to the unique advantages of two-dimensional material,Mo S₂ is combined with conductive polymers.PANI@Mo S₂ composite nanoparticles are formed the external material molybdenum disulfide and the internal material polyaniline.In the first step,polyaniline nanoparticles are prepared by ice bath method.The obtained polyaniline samples under wet condition are coated with Mo S₂on the surface of polyaniline by hydrothermal method.Molybdenum disulfide has good interfacial polarization ability because of its lamellar structure with large specific surface area.As a common polymer with certain polarization,polyaniline is widely used in ER fluids.The sample prepared by combining the advantages of the two materials has better ER properties than one material.The material can withstand the highest voltage of 3 k V/mm,and the shear stress can reach 99 Pa under this voltage.