Abstract
Compact layers containing embedded semiconductor particles consolidated using pulsed electric current sintering exhibit intense, broadband near-infrared reflectance. The composites consolidated from nano- or micro-silica powder have a different porous microstructure which causes scattering at the air-matrix interface and larger reflectance primarily in the visible region. The 3 mm thick composite compacts reflect up to 72% of the incident radiation in the near-infrared region with a semiconductor microinclusion volume fraction of 1% which closely matches predictions from multiscale Monte Carlo modeling and Kubelka-Munk theory. Further, the calculated spectra predict a reddish tan compact with improved reflectance can be obtained by decreasing the average particle size or broadening the standard deviation. The high reflectance is achieved with minimal dissipative losses and facile manufacturing, and the composites described herein are well-suited to control the radiative transfer of heat in devices at high temperature and under harsh conditions.
Highlights
Controlled propagation of near-infrared (NIR) electromagnetic waves has been demonstrated in diverse applications, including bio sensing [1], thermal energy management [2], and switchable meta-mirrors [3]
The specimens obtained from micro-silica powders have a more porous composite matrix than those consolidated from nano-silica
Conclusions spectra calculated using Monte Carlo and Kubelka-Munk methods pre dicted that a significant increase in reflectance can be obtained by lowering the average particle size as opposed to a narrower particle size distribution
Summary
Controlled propagation of near-infrared (NIR) electromagnetic waves has been demonstrated in diverse applications, including bio sensing [1], thermal energy management [2], and switchable meta-mirrors [3]. Developing compact layers to trap light in the NIR could be used to provide quantitative spectral information about heat transport under harsh conditions [5] or increase efficiency and reduce cost in solar cells and thermal energy management [6,7,8]. Materials or devices employed in thermal insulation and Gradient Heat Flux sensing applications are subjected to high temperature and harsh conditions. Semiconductors have low dissi pative losses and the quality of the scattering resonances is better maintained than in metallic particles at high temperatures [10]. The light interacts with the particles to generate strong scattering resonances. Unique optical effects such as unidirectional scattering and enhanced Raman scattering arise when there is interference between the reso nances and strong localization of the electric and magnetic fields [14,15,16]
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