Radiative Properties of Real Surfaces

Modest, Michael F.

doi:10.1016/b978-0-12-386944-9.50003-0

Cited by 9 publications

(6 citation statements)

References 89 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although the Si-FNSs were heated to the same temperature, the apparent temperatures increase with etching time: the apparent temperature of the Si-FNS etched for 10 min was approximately 48 °C but that of the Si-FNS etched for 240 min was approximately 91 °C. Given that the emissive power is governed by the surface temperature and emissivity 8 and that the temperature of the Si-FNSs was constant, we believed that emissivity varies as the etching time increases. Therefore, we conducted emissivity measurements in the infrared range of 8−12 μm to manipulate the infrared colors.…”

Section: Resultsmentioning

confidence: 99%

“…This structural variation improves the multiple internal reflections inside the cavity, increases the path length of the incident light, enhances the light-trapping effect in the nanostructures, and finally results in strong absorption. 32,51 Moreover, according to Kirchhoff's law, 8 emissivity and absorptivity are equal in the thermal equilibrium state, meaning that the emission increases as cavity size increases. Recalling the linear proportionality between the lacunarity and height of the Si-FNSs (Figure 2e), we observed that the average emissivity has linear proportionality with lacunarity in the LWIR range.…”

Section: Resultsmentioning

confidence: 99%

“…As a countermeasure to novel detection systems, many researchers have studied various camouflage materials whose electromagnetic (EM) behaviors can be manipulated in particular spectral ranges. Because visible colors are generated by the reflection of visible light and infrared signatures are obtained from surface emissions based on temperature and emissivity, 8 color filters with subwavelength structures have been studied extensively for controlling visible colors 2,9−12 as well as photonic or plasmonic resonators for controlling infrared signatures. 13−17 Additionally, to address the EM properties in a multispectral range, several artificial materials have been studied, such as thin-film stacks, 1,18 hierarchical materials combining two or more materials working in different spectral ranges, 19−21 and metal−dielectric-metal (MDM) structures having broad tunable ranges.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Multispectral Optical Confusion System: Visible to Infrared Coloration with Fractal Nanostructures

Chang

Kim

Lee

et al. 2022

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

Optical confusion refers to a camouflage technique assimilated with the surroundings through manipulating colors and patterns. With the advances in multispectral imagery detection systems, multispectral camouflage studies on simultaneous deceptions in the visible to infrared ranges remain a key challenge. Thus, creating pixelated patterns is essential for mimicking background signatures by assimilating both colors and patterns. In this study, a multispectral optical confusion system (MOCS) comprising pixelated silicon-based fractal nanostructures (Si-FNSs) is introduced to realize multispectral optical confusion. We analyzed the fractality of the Si-FNSs to understand the relationships between structural characteristics and optical properties with the aggregation phenomenon. The aggregation phenomenon changes the morphological heterogeneity by up to 38.5%, enabling a controllable range of visible reflectivity from 0.01 to 0.12 and infrared emissivity from 0.33 to 0.90. Visible and infrared colors were obtained by controlling the wet-etching time from 10 to 240 min and temperature from 40 to 100 °C. Finally, the MOCS consisting of pixelated Si-FNSs was designed and created by extracting the pattern from the simultaneously captured visible and infrared background images. Using the artificial backgrounds representing these images, we evaluated and compared the multispectral optical confusion performance of the MOCS with conventional camouflage surfaces.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Multispectral Optical Confusion System: Visible to Infrared Coloration with Fractal Nanostructures

Chang

Kim

Lee

et al. 2022

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

show abstract

“…The IR emissivity/reflectivity of materials can also be electrically modulated. , Under the condition that ωτ ≪ 1 (ω is the angular frequency of the electromagnetic wave, τ is the relaxation time of conducting electrons in materials), the relationship between the spectral normal emissivity (ε) and the electrical resistivity (ρ) for a certain material approximately satisfies the Hagen–Rubens equation in the long-wavelength region (λ > 5 μm): − ε = 2 2 ρ ε 0 ω where ε 0 is the vacuum electric permittivity. Tunning carrier densities and electrical properties of materials is thus feasible to manipulate their IR emissivity.…”

Section: Bioinspired Thermal Energy Regulationmentioning

confidence: 99%

Biological and Bioinspired Thermal Energy Regulation and Utilization

Shi

Jiang

et al. 2023

Chem. Rev.

View full text Add to dashboard Cite

The regulation and utilization of thermal energy is increasingly important in modern society due to the growing demand for heating and cooling in applications ranging from buildings, to cooling high power electronics, and from personal thermal management to the pursuit of renewable thermal energy technologies. Over billions of years of natural selection, biological organisms have evolved unique mechanisms and delicate structures for efficient and intelligent regulation and utilization of thermal energy. These structures also provide inspiration for developing advanced thermal engineering materials and systems with extraordinary performance. In this review, we summarize research progress in biological and bioinspired thermal energy materials and technologies, including thermal regulation through insulation, radiative cooling, evaporative cooling and camouflage, and conversion and utilization of thermal energy from solar thermal radiation and biological bodies for vapor/electricity generation, temperature/infrared sensing, and communication. Emphasis is placed on introducing bioinspired principles, identifying key bioinspired structures, revealing structure–property–function relationships, and discussing promising and implementable bioinspired strategies. We also present perspectives on current challenges and outlook for future research directions. We anticipate that this review will stimulate further in-depth research in biological and bioinspired thermal energy materials and technologies, and help accelerate the growth of this emerging field.

show abstract

“…Therefore, given also the low radiation path in the reactor, it was chosen to perform simulations with the original WSGG model. Particle radiation and wall radiation interactions were considered: a value of 0.9 was set for both the coal particle emissivity and the reactor wall emissivity …”

Section: Numerical Modelmentioning

confidence: 99%

Evaluation of Scenario Uncertainties in Entrained Flow Reactor Tests through CFD Modeling: Devolatilization

2016

View full text Add to dashboard Cite

A Computational Fluid Dynamic model of oxy-coal devolatilization experiments in a pilot-scale entrained flow\ud reactor is proposed to gain insight into the thermal histories of the cloud of solid fuel particles and to investigate sources of\ud uncertainties that may affect the analysis of devolatilization. Solid fuel particles experience different paths and are characterized by\ud a temperature which is lower than the reactor nominal one at some of the sampling locations used for investigating\ud devolatilization rates. Indeed, neglecting the quick heating up of the particles by assuming their temperature to be equal to the\ud reactor one for calculating kinetics leads to an underestimation of devolatilization rates. A simple hypothesis on a linear\ud dependence of the particle temperature on residence time through an average heating rate, with residence time and heating rate\ud estimated from the numerical model, was found to largely improve the reliability of devolatilization kinetics even with a simple\ud Single First Order Reaction model. An analysis of uncertainties on the kinetic parameters due to the cloud of particles is\ud performed

show abstract

Radiative Properties of Real Surfaces

Cited by 9 publications

References 89 publications

Multispectral Optical Confusion System: Visible to Infrared Coloration with Fractal Nanostructures

Multispectral Optical Confusion System: Visible to Infrared Coloration with Fractal Nanostructures

Biological and Bioinspired Thermal Energy Regulation and Utilization

Evaluation of Scenario Uncertainties in Entrained Flow Reactor Tests through CFD Modeling: Devolatilization

Contact Info

Product

Resources

About