Preparation And Electrorheological Properties Of MOF-based Nanocomposite Particles

In today’s evolving world,the continuous progress of materials is the foundation and support of technological revolution.As a kind of intelligent material,Electrorheological（ER）fluid has different responses under different electric field environment,it can be produced rapidly and can also have reversible changes,which has broad prospects of engineering application.Therefore,it is imperative to study and explore a variety of electrorheological materials.Due to the basic characteristics of traditional electrorheological materials,the anti-deposition and dielectric properties are not ideal,which affect their electrorheological efficiency and performance.Metal organic framework（MOF）material is,in recent years,the rise of a kind of coordination polymer,whose three-dimensional structure can provide good active point,large specific surface area and the characteristics to be able to get a good sedimentation of the problems in the dispersed suspension,and can improve the dielectric performance,improve ER variation of material performance now.In this paper,two new ideas for the preparation of MOF-based nanocomposites are proposed,and the composition,structure and electrorheological properties of MOF-based composites,doping with different amounts of surfactants proportions of rare earth ion Ce,are systematically studied.The aim is to take advantage of the anisotropic morphology and rich porosity of MOF to improve ER property.The main content includes the following two aspects:（1）MOF-Ti（MIL-125）was prepared by simple solvothermal method and doped with rare earth element Ce in a certain proportion.Taking advantage of the MOF-Ti,the doping gradient is shown as follows:The mole ratios of cerium in cerium nitrate hexahydrate and titanium in the reaction system are 0:100,1:100,1.5:100 and 2:100,3:100 and 5:100,respectively.The influence of preparation conditions,namely the influence of Ce doping rare earth ratio on the prepared MOF particles,and explore its influence on electrorheological properties.The results show that the morphology and structure of the MOF are changed after different proportion of Ce doped with rare earth ions,and the morphology of the MOF is decahedral under 1.5%doping ratio.The electrorheological test of pure MOF can be tested below 1000 V,but after Ce doping,the leaking current intensity of applied electric field increases during electrorheological test.（2）In order to solve the problem that the electric field is difficult to apply due to the excessive high leaking current caused by rare earth doped MOF.Further,the Ce doped MOF structure was prepared by solvothermal method as the precursor,and the precursor was calcined at 500℃for two hours in the air atmosphere to obtain the final Ti O₂samples with different Ce doping.The influence of different doping ratios of rare earth element Ce on the composition,structure and electrorheological properties of Ce-mesoporous titanium oxide was systematically studied,and multiple characterization was carried out.The results show that the precursor structure of MOF doped with Ce ions can obtain the anisotropy shape and mesoporous titanium oxide shape well after two hours of calcination at 500℃,thus achieving the improvement of electrorheological properties,and the mesoporous titanium oxide with the doping ratio of 1.5%Ce has a high electrorheological effect.The study found that reasonable doping with Ce for improving the precursor morphology,has a very important way,and square or round pie particle shape which can keep relatively complete after calcining process,and to improve the dielectric performance of the samples,so as to further improve the activity of material of electrorheological has a critical role.In conclusion,the synthesized rare earth ion Ce-doped MOF-Ti structure has unique morphological and structural characteristics,and the existence of mesoporous,which greatly enrich the polarization ability,especially the interfacial polarization ability.The Ce-mesoporous titanium oxide prepared by MOF-Ti doping has excellent electrorheological properties,and the doping of rare earth element Ce is beneficial to improve the dielectric properties and conductive behavior of the materials.This is a better application of MOF structure in the field of electrorheological field,and puts forward some ideas and new insights for the future design and transformation of MOF structure applied in electrorheological effect.