Research On The Microstructure And Optical Properties Of The Magnetic Fluid Based On The Monte Carlo Method

Magnetic fluid as a novel functional material has the characteristics of the magnetism of solid and the liquidity of liquid. Thus it shows a lot of special physical properties and superficial phenomenon. The research of microstructure and optical properties of magnetic fluid is one of current hot research questions. In this paper, by Monte Carlo numerical simulation method, microstructure of magnetic fluid is modeled. Then the changes in optical properties caused by the microstructure changes are analyzed and studied.In this paper, potential-energy function of magnetic particles in magnetic fluid is detailedly analyzed, based on which, the forming process of the two dimensions and three dimensions micro aggregate structure of magnetic fluid is simulated using Monte Carlo method. Clusters structure of magnetic particles in the magnetic fluid is formed without magnetic field. And the magnetic particles in magnetic field will form chain structure along with the direction of magnetic field. With the increase of magnetic field strength (25Gs,50Gs,75 Gs, 100Gs) the chain structure becomes length and straighten; with the increase of the concentration (1%,1.8%,3.6%) the chain structure becomes long and dense.On the basis of magnetic fluid microstructure built by Monte Carlo method, the transmission model of magnetic fluid is established. Also utilizing Monte Carlo method, the transfer process of light transmitting inside the magnetic fluid film is simulated. The influence factors in the transfer process are analyzed, such as magnetic field strength, magnetic field direction, film thickness volume concentration and so on. Spectral transmittance, reflection and absorption of magnetic fluid film are counted to obtain the relationship between each factors and the spectral transmittance and transmittance at 1550nm of magnetic fluid film. When the direction of incident light is parallel to the direction of applied magnetic field, transmittance increases with the increase of magnetic field strength (0Gs,25Gs,50Gs,75Gs and 100Gs, etc.); when the direction of incident light is vertical to the direction of applied magnetic field, with the increase of magnetic field strength, the transmittance will be first rising then reducing. Meanwhile the concentration and thickness impact on magnetic fluid transmittance is discussed:with concentration increasing(1%,1.8%,3.6%, etc.), the transmittance linearly decreases; with thickness increasing(5μm, 10μm,15μm,20μm, etc.), the transmittance linearly decreases.Besides, under existing experimental conditions, the experiment system is finally set up. When the concentration 1.8%, the thickness of film 10μm, the incident light parallel or vertical to magnetic field and the magnetic field strength 0～200Gs, the changing rules between magnetic fluid film transmittance and the applied magnetic field strength are obtained in experiments. Comparing the simulation results and the experiments results, the trends are same, and the maximum relative error is 8.79% and 5.67%. The rationality and validity of the magnetic fluid structure model and the transmittance model is verified.Through the research in this paper, magnetic fluid structure changes can be understood at the micro-level. And the influence mechanism between external environment and optical properties of magnetic fluid is essentially explicit. It is of great significance for the magnetic fluid and fiber technologies combined to achieve the application on optical sensors (such as optical magnetic sensors, etc.) in the future.