Research On The Preparation And Properties Of Electromagnetic Composite Rheological Polishing Fluids

With the continuous development,innovation and integration of optics and electronics,more and more high requirements are put forward for the manufacturing precision of photoelectric crystal substrates,which are represented by the manufacturing of integrated circuits,photovoltaic and flat panel display,and the limit of precision machining is constantly challenged.Only by continuously realizing the high efficiency and low cost machining of lower damage and smoother surface can we meet the requirements of the rapid development of information technology industry.Therefore,it is necessary to continuously explore new efficient and ultra-precision flattening technology.Electromagnetic composite rheological polishing based on the electrorheological effect and magnetorheological effect is a kind of processing method which forms a flexible polishing pad under the action of external electric field and magnetic field and then removes the material on the workpiece surface.It can ensure high removal efficiency at the same time without introducing the surface damage,can efficiently eliminate the subsurface damage layer of grinding,nearly zero and surface damage and nanoscale precision polishing,and a traditional mechanical polishing and chemical mechanical polishing incomparable advantages,is to address the electro-optical crystal substrate of super smooth and flat,a kind of effective processing method.In this paper,based on the electromagnetic composite rheological polishing technology,the preparation method of new electromagnetic two-phase composite particles was studied,the components of the electromagnetic composite rheological polishing fluid were optimized,and the removal rate model of the electromagnetic and magnetorheological properties and the electromagnetic composite rheological polishing was established.The specific research contents and results are as follows:First of all,based on the electrorheological effect and produce principle of magnetorheological effect,select the appropriate dielectric materials and magnetic materials,according to the electrorheological materials and physical and chemical properties of magnetorheological material,adopt appropriate chemical synthesis method combined together,successfully prepared a variety of kernel with magnetorheological effect and the shell is of electrorheological effect duplex composite particles:Different thickness of the shell type of silicon dioxide composite particles,low silica shell as the substrate of different crystal type titanium dioxide composite particles and low silica shell as insulating layer of different size of diamond powder composite particles,and through the Raman,SEM,EDS,XRD,laser granularity instrument on the characterization,The successful coating,particle size change and crystal transformation of the shell layer were verified.Secondly,the electromagnetic composite particles were prepared into the electromagnetic composite rheological fluid,and the electrical and magnetorheological properties of the electromagnetic composite particles were detected by using MCR302 equipped with electrorheological module and magnetorheological module.Results show that the independent preparation of electromagnetic rheological fluid has good electric and magnetic rheological properties,including silicon dioxide and titanium dioxide model due to the influence of the shell,while the magnetic rheological property can be pure carbonyl iron powder type of MRF has subsided,but it is than ordinary ferroferric oxide type electromagnetic composite rheological more excellent performance of electrorheological fluid.However,the diamond micro-powder type,due to the irregular diamond micro-powder with a pit-like distribution on its surface,enhances the friction between particles and greatly improves the electric and magnetorheological shear stress,making up for the weakened electric and magnetic shear stress caused by the shell layer.When the excitation current is 3A,the magnetic shear stresses of silicon dioxide,titanium dioxide and diamond powder are3735 Pa,3657 Pa and 4104 Pa,respectively.When the voltage is 2500 V,the electric shear stresses are 73 Pa,119 Pa and 276 Pa,respectively.Finally,the fused quartz glass was polished by single electric field,single magnetic field and combined electromagnetic field on the electromagnetic composite polishing device.The results show that the polishing efficiency under single electric field is much lower than that under single magnetic field and combined electromagnetic field.Under the effect of a single magnetic field,a high removal rate can be obtained,but under the influence of a gradient magnetic field,the typical W-shaped profile appears,and the height difference of the profile is large.Under the action of electromagnetic composite field,the height difference between the center of the circle with the minimum material removal rate and the lowest place with the maximum material removal rate is smaller,and the processed surface with more uniform and flat surface can be obtained.Compared with MR polishing,the maximum height difference of surface profile can be reduced from 8 ?m to 2.5 ?m after EMR polishing,which is an improvement of 68.75%.