Magnetorheological Study Based On Suspension System Of Cellulose Derivatives

Magnetorheological fluid is a suspension system which stabilized by additives and formed by magnetic particles as dispersed phase that dispersed in the carrier fluid.The system can achieve the rapid transition from liquid to solid state and increase the reversibility of viscosity and yield stress by regulating magnetic field.According to this characteristic,various kinds of magnetorheological fluid devices emerge one after another in order to meet the needs of engineering field.At present,the focus of researchers is still the development of high performance magnetorheological fluid.Sedimentation stability has been a problem that has not been completely solved in the research and development process of magnetorheological fluid.Because there is a large density difference between magnetic particles and liquid carrier,magneto-rheological fluid inevitably exists sedimentation phenomenon.As a result,the rheological property of magnetorheological fluid can decline or even fail.In this paper,carbonyl iron was selected as magnetic particles,and cellulose derivatives were used to stabilize the water-based magnetorheological fluid.The effects of additives on magnetorheological properties and the stability of magneto-rheological fluid by different cellulose derivatives were studied.Specific research contents are as follows:1.Carbonyl ferromagnetic rheological fluids with different volume fractions were prepared.The chain-forming process and form of magnetorheological fluid were studied by optical microscope.The relationship between macroscopic magnetorheological properties and microscopic magnetic particle chains is established by magnetic field scanning,steady-state scanning and other rheological testing methods.Then,the effects of volume fraction and magnetic field strength on the structure and properties of magnetorheological fluid were studied.Furthermore,creep and creep recovery experiments show that chain structures do not work well under large stresses and need to be explained by cylindrical structures.2.Carbonyl ferromagnetic fluid was stabilized by cellulose nanocrystalline(CNC).The performance and stability of CNC/CI-based magnetorheological fluid were studied by rheology.The relationship between yield stress,zero field viscosity and the internal structure change of magnetorheological fluid was also established by rheology.Through creep experiments,it is proved that CNC thixotropic network and the chain structure of magnetic particles work together to provide creep resistance.In the time scanning experiment,large strain was applied to destroy the microstructure of magnetorheological fluid,and it was found that the recovery of thixotropic network was hysteresis,and it took some time to return to the original state.3.Three cellulose derivatives were used to stabilize CI based MRF,then the effects of additive types on magnetic rheological properties were compared and analyzed.Under the same magnetic field strength and additive mass fraction,thixotropic network formed by cellulose nanofibers(CNF)will increase the yield stress and zero-field viscosity of the system,and the fluidity of magnetorheological fluid will be seriously weakened.In the sedimentation experiment,the introduction of cellulose based additives can stabilize the magnetorheological fluid well.The distance between Cl particles in the system can be used as the basis for evaluating the stability of MRF.Because CNF has a large length-diameter ratio,a more stable thixotropic network can be formed in the system.Therefore,the spacing of CI particles is the largest and the stability of magnetorheological fluid is the best.The nature of the different additives needs to be considered separately and the type and amount of the additive must be determined according to the specific needs.