A study on the spectra equivalent attenuation coefficient of the micron pore size aluminum foam

Metal foam is a new functional material having a variety of excellent performances because of its special porous structure. The size of the porosity and stent can achieve micron and submicron depending on the preparation process. For the micron-sized pore, its internal analysis of the thermal radiation transfer needs to consider the coherence effect. This article uses the finite-difference time-domain (FDTD) method to study the spectra equivalent attenuation of the monolayer and multilayer periodic cube cells of aluminum foam and analyze the size effect when the incident wavelength is comparable with the pore size. The results show that there was a complex nonlinear relationship between the equivalent attenuation coefficient and the number of layers and the equivalent attenuation coefficient of monolayer structure reaches approximately 20% of the deviation with that of the multilayer structure (20 layers) due to the size effect, however, the deviation was less than 6% between the two-layer structure and the multilayer structure (20 layers), and the effective spectral extinction coefficient stabilizes as the number of layers increases. The transmittance of aluminum foam with different thickness calculated by FDTD was in good agreement with the classical multilayer net radiation method which indicated that the method in which aluminum foam was equivalent to semitransparent media using the classical theory of radiative transfer was feasible.