The concept of emissivity has been with the scientific and engineering world since Planck formulated his blackbody radiation law more than a century ago.Nevertheless,emissivity is an elusive concept even for ex⁃perts....The concept of emissivity has been with the scientific and engineering world since Planck formulated his blackbody radiation law more than a century ago.Nevertheless,emissivity is an elusive concept even for ex⁃perts.It is a vague and fuzzy concept for the wider community of engineers.The importance of remote sensing of temperature by measuring IR radiation has been recognized in a wide range of industrial,medical,and environ⁃mental uses.One of the major sources of errors in IR radiometry is the emissivity of the surface being measured.In real experiments,emissivity may be influenced by many factors:surface texture,spectral properties,oxida⁃tion,and aging of surfaces.While commercial blackbodies are prevalent,the much-needed grey bodies with a known emissivity,are unavailable.This study describes how to achieve a calibrated and stable emissivity with a blackbody,a perforated screen,and a reliable and linear novel IR thermal sensor,18 dubbed TMOS.The Digital TMOS is now a low-cost commercial product,it requires low power,and it has a small form factor.The method⁃ology is based on two-color measurements,with two different optical filters,with selected wavelengths conform⁃ing to the grey body definition of the use case under study.With a photochemically etched perforated screen,the effective emissivity of the screen is simply the hole density area of the surface area that emits according to the blackbody temperature radiation.The concept is illustrated with ray tracing simulations,which demonstrate the approach.Measured results are reported.展开更多
Infrared radiation(IR)ceramics have been recognized as energy-saving materials for high-temperature industry due to excellent IR performance.However,for conventional IR ceramics,low emissivity in partial band and emis...Infrared radiation(IR)ceramics have been recognized as energy-saving materials for high-temperature industry due to excellent IR performance.However,for conventional IR ceramics,low emissivity in partial band and emissivity degradation during high-temperature service restricted the practical application.Herein,we integrated broad-band high emissivity and slow degradation rate in novel high-entropy perovskite ceramics:La(Al_(0.2)Co_(0.2)Fe_(0.2)Ni_(0.2)Cr_(0.2))O_(3−δ)(HE-1) and La(Al_(0.2)Co_(0.2)Fe_(0.2)Ni_(0.2)Mn_(0.2))O_(3−δ)(HE-2).Specifically,the high-energy ceramic HE-1&HE-2 displayed high emissivity of 0.94/0.90 and 0.90/0.95 in the broad-band of near/mid-infrared(0.76–14µm).This excellent IR performance can be attributed to impurity energy level absorption,free carrier absorption,and lattice vibration absorption.During high-temperature service,these high-entropy ceramics have much slower emissivity degradation rate than conventional IR ceramic,because of hysteresis diffusion effect.Additionally,energy-saving ratios of 17.70%and 10.77%were realized by heating water with porous burner containing HE-1 and HE-2 coating respectively,due to enhanced heat radiation in systems.Thus,these high-entropy IR ceramics have significant application potential for long-term energy-saving in high-temperature industry.展开更多
Given the conflict between high microwave absorption and low infrared emissivity performance in electromagnetic-controlled metasurface design,achieving multispectral compatibility between low microwave reflectivity an...Given the conflict between high microwave absorption and low infrared emissivity performance in electromagnetic-controlled metasurface design,achieving multispectral compatibility between low microwave reflectivity and low infrared emissivity remains challenging.Leveraging the non-dominated sorting genetic algorithm II(NSGA-II),this study presents a three-layer lightweight metasurface comprising a metal-patterned F4B substrate with a metal backplate,designed to achieve simultaneous ultra-wideband polarization conversion and low infrared emissivity.展开更多
The rapid evolution of hypersonic vehicle technologies necessitates robust thermal protection systems capable of withstanding extreme oxidative ablation.This study introduces a novel gradient-architected ZrB_(2)-MoSi_...The rapid evolution of hypersonic vehicle technologies necessitates robust thermal protection systems capable of withstanding extreme oxidative ablation.This study introduces a novel gradient-architected ZrB_(2)-MoSi_(2)-SiC dense layer embedded within a lightweight three-dimensional(3D)needled carbon fiber composite.Utilizing the volatility of ethanol and polycarbosilane,the ceramic slurry is selectively infused into targeted regions of the fibrous structure,optimizing the ZrB_(2)to MoSi_(2)ratio to enhance performance.The resulting dense layer exhibits exceptional emissivity,surpassing 0.90 in the 1-3μm range and exceeding 0.87 in the 2-14μm range.Moreover,it demonstrates remarkable oxidative ablation resistance.Specifically,at an optimized ZrB_(2)to MoSi_(2)ratio of 6:4,the dense layer achieves a minimal linear ablation rate of 0.015μm·s^(-1) under a 1.5 MW·m^(-2)oxyacetylene flame for 1000 s.Even after exposure to oxyacetylene ablation at surface temperatures of approximately 1750℃for 1000 s,the dense layer retains its structural integrity,highlighting its enduring oxidation resistance.The incorporation of MoSi_(2)not only enhances emissivity but also fortifies the ZrO_(2)and SiO_(2)oxide layers,crucial for environments with elevated oxygen levels,thereby mitigating the active oxidation of SiC.This combination of high emissivity and long-term oxidation resistance at ultra-high temperatures positions the ZrB_(2)-MoSi_(2)-SiC dense layer as an exceptionally promising candidate for advanced thermal protection in hypersonic vehicles.展开更多
文摘The concept of emissivity has been with the scientific and engineering world since Planck formulated his blackbody radiation law more than a century ago.Nevertheless,emissivity is an elusive concept even for ex⁃perts.It is a vague and fuzzy concept for the wider community of engineers.The importance of remote sensing of temperature by measuring IR radiation has been recognized in a wide range of industrial,medical,and environ⁃mental uses.One of the major sources of errors in IR radiometry is the emissivity of the surface being measured.In real experiments,emissivity may be influenced by many factors:surface texture,spectral properties,oxida⁃tion,and aging of surfaces.While commercial blackbodies are prevalent,the much-needed grey bodies with a known emissivity,are unavailable.This study describes how to achieve a calibrated and stable emissivity with a blackbody,a perforated screen,and a reliable and linear novel IR thermal sensor,18 dubbed TMOS.The Digital TMOS is now a low-cost commercial product,it requires low power,and it has a small form factor.The method⁃ology is based on two-color measurements,with two different optical filters,with selected wavelengths conform⁃ing to the grey body definition of the use case under study.With a photochemically etched perforated screen,the effective emissivity of the screen is simply the hole density area of the surface area that emits according to the blackbody temperature radiation.The concept is illustrated with ray tracing simulations,which demonstrate the approach.Measured results are reported.
基金financially supported by the National Natural Science Foundation of China(Nos.52372029,U22A20127,52304356,and 92263205)the Key R&D Plan Project in Hubei Province(No.2023BCB100).
文摘Infrared radiation(IR)ceramics have been recognized as energy-saving materials for high-temperature industry due to excellent IR performance.However,for conventional IR ceramics,low emissivity in partial band and emissivity degradation during high-temperature service restricted the practical application.Herein,we integrated broad-band high emissivity and slow degradation rate in novel high-entropy perovskite ceramics:La(Al_(0.2)Co_(0.2)Fe_(0.2)Ni_(0.2)Cr_(0.2))O_(3−δ)(HE-1) and La(Al_(0.2)Co_(0.2)Fe_(0.2)Ni_(0.2)Mn_(0.2))O_(3−δ)(HE-2).Specifically,the high-energy ceramic HE-1&HE-2 displayed high emissivity of 0.94/0.90 and 0.90/0.95 in the broad-band of near/mid-infrared(0.76–14µm).This excellent IR performance can be attributed to impurity energy level absorption,free carrier absorption,and lattice vibration absorption.During high-temperature service,these high-entropy ceramics have much slower emissivity degradation rate than conventional IR ceramic,because of hysteresis diffusion effect.Additionally,energy-saving ratios of 17.70%and 10.77%were realized by heating water with porous burner containing HE-1 and HE-2 coating respectively,due to enhanced heat radiation in systems.Thus,these high-entropy IR ceramics have significant application potential for long-term energy-saving in high-temperature industry.
基金National Natural Science Foundation of China(62401614,62201609)Natural Science Foundation of Shaanxi Province(2024JC-YBMS-462)National Natural Science Foundation Regional Innovation and Development Joint Fund(U24A20224)。
文摘Given the conflict between high microwave absorption and low infrared emissivity performance in electromagnetic-controlled metasurface design,achieving multispectral compatibility between low microwave reflectivity and low infrared emissivity remains challenging.Leveraging the non-dominated sorting genetic algorithm II(NSGA-II),this study presents a three-layer lightweight metasurface comprising a metal-patterned F4B substrate with a metal backplate,designed to achieve simultaneous ultra-wideband polarization conversion and low infrared emissivity.
基金supported by the National Natural Science Foundation of China(Nos.52272060,51902067,51872066 and 52172041)the Key Program of National Natural Science Foundation of China(No.52032003)+5 种基金the Young Elite Scientists Sponsorship Program by CAST(No.2020QNRC001)China Postdoctoral Science Foundation(Nos.2019M651282 and 2022T150157)Heilongjiang Provincial Postdoctoral Science Foundation(Nos.LBH-Z19022 and LBH-TZ2207)Heilongjiang Touyan Innovation Team Program,Shanghai Aerospace Science and Technology Innovation Fund(No.SAST2019-012)the Fundamental Research Funds for the Central Universities(No.FRFCU5710051022)the Science Foundation of National Key Laboratory of Science and Technology on Advanced Composites in Special Environments(No.JCKYS2022603C011).
文摘The rapid evolution of hypersonic vehicle technologies necessitates robust thermal protection systems capable of withstanding extreme oxidative ablation.This study introduces a novel gradient-architected ZrB_(2)-MoSi_(2)-SiC dense layer embedded within a lightweight three-dimensional(3D)needled carbon fiber composite.Utilizing the volatility of ethanol and polycarbosilane,the ceramic slurry is selectively infused into targeted regions of the fibrous structure,optimizing the ZrB_(2)to MoSi_(2)ratio to enhance performance.The resulting dense layer exhibits exceptional emissivity,surpassing 0.90 in the 1-3μm range and exceeding 0.87 in the 2-14μm range.Moreover,it demonstrates remarkable oxidative ablation resistance.Specifically,at an optimized ZrB_(2)to MoSi_(2)ratio of 6:4,the dense layer achieves a minimal linear ablation rate of 0.015μm·s^(-1) under a 1.5 MW·m^(-2)oxyacetylene flame for 1000 s.Even after exposure to oxyacetylene ablation at surface temperatures of approximately 1750℃for 1000 s,the dense layer retains its structural integrity,highlighting its enduring oxidation resistance.The incorporation of MoSi_(2)not only enhances emissivity but also fortifies the ZrO_(2)and SiO_(2)oxide layers,crucial for environments with elevated oxygen levels,thereby mitigating the active oxidation of SiC.This combination of high emissivity and long-term oxidation resistance at ultra-high temperatures positions the ZrB_(2)-MoSi_(2)-SiC dense layer as an exceptionally promising candidate for advanced thermal protection in hypersonic vehicles.
