Investigation of the optical properties of aluminum nanoparticles in PETN

摘要

Study of optical properties of metal nanoparticles is important in many technical applications, such as development of new energetic meterials, hyperthermia therapy carcinoma, creating new solar cells, etc. The problem is challenging because the nanoparticles both absorb and scatter light. The effect of multiple scattering occurs in many applications, so a comprehensive study that take into account the optical characteristics of individual nanoparticles and their mutual influence is necessary. Objective: To determine the characteristics of the absorption and scattering of light by metal nanoparticles in a transparent medium. Objects were PETN compressed tablets with additives of nano-sized aluminum (～100 nm). Experimental measurements were performed using photometric sphere that allowed us to obtain the transmission coefficients and the sum of transmission and reflection coefficients varying the thickness of the sample and the mass fraction of the additives. The computer programs developed including the calculation of absorption and scattering cross sections and the scattering indicatrice in terms of the Mie theory with their reuse for solving the equation of radiative transfer with spherical harmonics approach. Fresnel boundary conditions were used. The simulation of light absorption and scattering was carried out. The increasing in the scattering coefficient comparing to the Fresnel value is shown. The dependence of the absorption coefficient on the concentration of inclusions is close to linear so the Beer's law is approximately applicable. The results compared with the experimental data at the wavelength of 643 nm, the refractive index obtained (1.280-5.899i) agrees well with the tabulated data. The values of true (0.661) and the apparent (1.640) coefficient of absorption efficiency determined in these conditions. It is shown that the energy absorbed by nanoparticles is higher than estimated with the geometrical cross-section because of the light scattering. The reported study was partially supported by RFBR, research project No. 13-03-98032.