Radiation Absorption And Distribution Of Temperature Field Of Spherical Particle In The Medium

Particle is regarded as the fourth state of material. Typical particulate media include: atmospheric aerosol, stealth coating, rocket plume and so on. When the electromagnetic wave propagating in the media, the light intensity attenuation happens and the wavelength becomes small. Besides, the particle also has some complex interaction with the medium, so many researchers are interested with the absorption and scattering of irradiated particle. In this thesis, the problems of radiation absorption characteristics of particle in media are investigated and the main research work are as follows:(1) According to the Mie theory in absorbent medium, we establish the mathematical model of electric field distribution of particle which is dispersed in the media. Using Ag particle in ZnS、H2O as examples, we calculate the internal electric field of irradiated particle, and compare these with the electric field distribution of Ag in the vacuum separately. In the calculation range of this paper, we find that the inner electric field will concentrate on the back side of particle if the scale parameter is small and vice versa.(2) Treat absorption energy as the inner heat source of particle. Based on the numerical heat transfer, take the source into the heat conduction differential equation and solve the temperature by programming. Then using Ag particle in ZnS and Al2O3 particle in H2O as examples, we calculate the temperature distribution of cross section of irradiated particle. We find that radius and wavelength influence the shape of temperature distribution; radiation time and intensity effect the size of temperature.(3) Based on the Mie theory, We establish the FDTD model of irradiated particle and compare the results of two different methods. We simulate the radiation absorption characteristics of Ag/Al2O3 nanoshell particles in the medium of H2O with FDTD solutions software. In the calculation range, the absorption of small Ag particle is stronger; with the distance between particles increasing, the absorption of Ag particle become weaker. The average radiation absorption energy density of H2O is more strong if the size of core Ag particle is smaller; with the distance between particles increasing, the radiation absorption effect of H2O will trend increased gradually.(4) We use the experimental methods of magnetron sputtering and annealing to prepare the particle composite media to prove that the size and space of particle and media will effect the particle radiation. The experiment shows that after depositing the composite film on substrate, the global reflectance of the sample increases; the transmittance decreases and the absorptivity is enhanced. In addition, when the composite film irradiated, the change of optical property is the result of interaction between particle and medium and this interaction play a more prominent role than pure particle or medium.