The ability to manufacture, control, and manipulate structures at extremely small scales is the hallmark of modern technologies, including microelectronics, MEMS/NEMS, and nano-biotechnology. Along with the advancement of microfabrication technology, more and more investigations have been performed in recent years to understand the influence of microstructures on radiative properties. The key to the enhancement of performance is through the modification of the reflection and transmission properties of electromagnetic waves and thermal emission spectra using one-, two-, or three-dimensional micro/nanostructures. This review focuses on recent developments in metamaterials–manmade materials with exotic optical properties, and other nanostructured materials, such as gratings and photonic crystals, for application in radiative energy transfer and energy conversion systems.
Radiative properties of rough surfaces, particulate media and porous materials are important in thermal engineerit transfer between surfaces and volume elements in participating media, as well as for accurate radiometric temperature measurements. In this paper, recent research on scattering of thermal radiation by rough surfaces, fibrous insulation, soot, aerogel, biological materials, and polytetrafluoroethylene (PTFE) was reviewed. Both theoretical modeling and experimental investigation are discussed. Rigorous solutions and approximation methods for surface scattering and volume scattering are described. The approach of using measured surface roughness statistics in Monte Carlo simulations to predict radiative properties of rough surfaces is emphasized. The effects of various parameters on the radiative properties of particulate media and porous materials are summarized.
The energy conversion properties of Bi-Sb system thermoelectric materials doped by Ag was investigated. Bi85Sb15-xAgx (x=0, 1, 2, 3, 4) alloys with Ag substitution for Sb were synthesized by mechanical alloying and then pressed under 5 GPa at 523 K for 30 min. The phase structure of the alloys was characterized by X-ray diffraction. The electric conductivities and the seebeck coefficients were measured at the temperature range of 80-300 K. The results reveal that the electric conductivities of the Ag-doped Bi-Sb alloys are highly improved. The power factor of Bi85Sb14Ag1 reaches a maximum value of 2.98×10-3 W/(K2?m) at 255 K, which is about three times that of the un-doped sample Bi85Sb15 at the same temperature.