Infrared Measurements of Heating and Cooling Emissions in Aluminium and Steel during Tensile and Cyclic Loading

In this paper,a new thermographic method based on the measurement of infrared emission(IR) from the surface of loaded body has been used to study the cooling and heating in aluminium and steel specimens under tensile and cyclic loading.A typical test procedure using infrared to measure thermographic changes near the crack tip and the immediate surrounding area is described.In addi- tion,a procedure for determining the stress concen- tration near the crack tip is also presented.Results are given for thermoelastic cooling phenomenon of metals during the tensile process and IR cooling and IR heating emissions at the crack tip during cyclic loading.Attention is drawn to the multiple phenomenon of IR cooling emission in the received signal as the applied load range increases beyond the elastic limit of both metals.A new application of the IR technique to the determination of the po- sition of crack tip during cyclic loading is also pres- ented.

Unidentified Infrared Discrete Emission Bands

Unidentified Infrared emission bands (UIBs) are infrared discrete emissions from circumstellar regions, interstellar media (ISM), star-forming regions, and extragalactic objects for which the identity of the emitting materials is unknown. The main infrared features occur around peaks at 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 μm with the photon’s rest energy at the peaks 0.376, 0.200, 0.161, 0.144, 0.111, and 0.098 eV, respectively. The UIB emission phenomenon has been studied for about forty five years. The prevailing hypothesis is that the materials responsible for UIB are polycyclic aromatic hydrocarbon (PAH) molecules. PAHs are thought to be one of the main forms in which carbon exists in space. And yet, not a single member of this group of compounds had been identified in space definitively until now [1]. In frames of Hypersphere World-Universe Model (WUM), we introduced Dark Matter (DM) particles, named DIONs, with the rest energy 0.199 eV and an energy density of 68.8% of the total energy density of the World. DIONs compose Outer shells of DM Supercluster’s Cores—the main objects of the World [2]. In this paper, we give an explanation of UIB emission based on the self-annihilation of DM particles DIONs and biDIONs (DIONs pairs) with a rest energy about 0.38 eV that depends on the binding energy. To the best of our knowledge, WUM is the only cosmological model in existence that is consistent with UIB emission phenomenon.

A thin radar-infrared stealth-compatible structure:Design,fabrication,and characterization

A thin radar-infrared stealth-compatible structure with reflectivity below -10 dB in the whole radar X wave band and infrared emissivity less than 0.3 in the infrared region of 8μm-14 μm is reported. The designed stealth-compatible structure consists of metallic frequency selective surface （MFSS）, resistive frequency selective surface （RFSS）, and metal backing from the top down, and it is only 2. l-mm thick. The MFSS is made up of some divided low infrared emissivity metal copper films, and the RFSS consists of a capacitive array of square resistive patches. They are placed close together, working as an admittance sheet because of a mutual influence between them, and the equivalent admittance sheet greatly reduces the thickness of the whole structure. The proposed stealth-compatible structure is verified both by simulations and by experimental results. These results indicate that our proposed stealth-compatible structure has potential applications in stealth fields.

Preparation and Characterization of High Infrared Emissivity Mn-doped NCO Spinel Composites

NiCr2O4（NCO）spinel composites with different Mn/Ni atomic ratios（Mn/Ni=0.05,0.10,0.15,and 0.20）were synthesized via solid state reaction method.Phase compositions and microstructure of samples were characterized by X-ray diffraction（XRD）and X-ray photoelectron spectroscopy（XPS）.The TG-DSC curves showed that the appropriate baking temperature for Mn-doped NCO spinel preparation was approximately 1 320℃.X-ray diffraction patterns exhibited the formation of NCO spinel with Fd-3m space group.Valence state of the Mn ions was determined from 2p and 3s X-ray photoelectron spectra.Manganese ions were mostly in divalent and trivalent states,and the ratio of Mn^2＋/Mn^3＋was 0.78-0.98.Fourier transform infrared spectroscopy（FTIR）was used to analyze the spectral emissivity of Mn doped NCO spinel.It was revealed that the infrared emissivity of Mn-doped NCO spinel in 1.8-5μm could be significantly enhanced with increasing content of Mn^2＋,reaching as high as 0.9398.Mn-doped NCO spinel showed excellent radiation performance and good prospect in high emissivity applications in the temperature range of 800-1 200℃.

Infrared emissivities of Mn,Co co-doped ZnO powders

Infrared emissivities of Zn0.99-xMn0.01CoxO （x = 0.00, 0.01, 0.03, 0.05） powders synthesized at different calcination temperatures by solid-state reaction are investigated. Their phases, morphologies, UV absorption spectra, and infrared emissivities are studied by XRD, SEM, UV spectrophotometer, and an IR-2 dual-band infrared emissometer in a range of 8 μm-14 μm. Doped ZnO still has a wurtzite structure, and no peaks of other phases originating from impurities are detected. The optical band-gap decreases as the Co content and calcination temperature ascend, and of which the smallest optical band gap is 2.19 eV. The lowest infrared emissivity, 0.754, is observed in Zn0.98Mn0.01Co0.01O with the increase in Co concentration. The infrared emissivity experiences fluctuations as the calcination temperature increases, and its minimum value is 0.762 at 1100 ℃.

Infrared Thermochromic Properties of VO_2 Thin Films Prepared through Aqueous Sol-gel Process

The stoichiometric vanadium（IV） oxide thin films were obtained by controlling the temperature, time and pressure of annealing. The thermochromic phase transition and the IR thermochromic property of 400 nm and 900 nm VO2 thin films in the 7.5 μm-14 μm region were discussed. The derived VO2 thin film samples were characterized by Raman, XRD, XPS, AFM, SEM, and DSC. The resistance and infrared emissivity of VO2 thin films under different temperature were measured, and the thermal images of films were obtained using infrared imager. The results show that the VO2 thin film annealed at 550 ℃ for 10 hours through aqueous sol-gel process is pure and uniform. The 900 nm VO2 thin film exhibits better IR thermochromic property than the 400 nm VO2 thin film. The resistance of 900 nm VO2 film can change by 4 orders of magnitude and the emissivity can change by 0.6 during the phase transition, suggesting the outstanding IR thermochromic property. The derived VO2 thin film can control its infrared radiation intensity and lower its apparent temperature actively when the real temperature increases, which may be applied in the field of energy saving, thermal control and camouflage.

Current Status and Prospect of Infrared Radiation Ceramics for Energy-saving Applications in High Temperature Furnaces

Nowadays,it is a great challenge to reduce energy consumption and exhaust emission for human activities,in particular,high temperature industries.Among many efforts made to realize energy savings for high temperature furnaces and kilns,the use of high emissivity materials is considered to be an effective route to increase their thermal efficiency by enhancing heat transfer.Most materials with high refractoriness and superior chemical stability have weak infrared absorption and radiation properties;however,their emissivity in infrared regions（1 —25 μm） could be effectively increased by ion doping.This is attributed to three main mechanisms：1） distortion of the crystal lattice;2） increase of free carrier absorption; 3） formation of impurity energy level.In this paper,the development and advancement of various material systems with high emissivity including non-oxides and oxide based ceramics were reviewed.It is also suggested that the establishment of evaluation models or instruments for energy savings would be beneficial to design and application of high emissivity materials in various high-temperature environment.Furthermore,more efforts should be made on durability of high emissivity materials at high service temperatures and on the standardization of testing methods for emissivity.

Dual Anthropogenic Origin of Global Warming through GHGs and IR Radiation Emissions from Artificialized Soils

This paper contributes to explain the global warming instead of"giving up"and thinking about passively adapting to climate change or global warming.It makes more sense to tackle what creates the greenhouse effect and contributes to global warming.The greenhouse effect is not only due to GHGs emissions,but also to the excess IR radiation emitted during the day,by artificial surfaces,following the absorption of solar radiation.The phenomenon should be compared to that of radiative forcing well known by climatologists and which makes the link between atmospheric pollution and the density of heat fluxes stopped by the atmosphere inducing global warming.It becomes clear that type an equation here.The surplus CO2 and IR radiation emissions influence global warming,not to mention the direct part of the heat released by the combustion of fossil fuels and even renewable(wood fires,biogas,friction of wind turbine propellers with the air).

Preparation and cooling performance analysis of double-layer radiative cooling hybrid coatings with TiO_(2)/SiO_(2)/Si_(3)N_(4) micron particles

Passive daytime radiative cooling is achieved by radiating heat into outer space through electromagnetic waves without energy consumption. A scalable double-layer coating with a mixture of TiO_(2), SiO_(2), and Si_(3)N_(4)micron particles for radiative cooling is proposed in this study. The finite-difference time-domain algorithm is used to analyze the influence of particle size and coating thickness on radiative cooling performance. The results of the simulation show that the particle size of 3 μm can give the best cooling performance, and the coating thickness should be above 25 μm for SiO_(2)coating. Meanwhile, the mixture of SiO_(2)and Si_(3)N_(4)significantly improves the overall emissivity. Through sample preparation and characterization,the mixture coating with a 1:1 ratio addition on an Al substrate exhibits high reflectivity with a value of 87.6% in the solar spectrum, and an average emissivity of 92% in the infrared region(2.5 μm–15 μm), which can be attributed to the synergy among the optical properties of the material. Both coatings can theoretically be cooled by about 8℃ during the day and about 21℃ at nighttime with hc = 4 W·m^(-2)·K^(-1). Furthermore, even considering the significant conduction and convection exchanges, the cooling effect persists. Outdoor experimental results show that the temperature of the double-layer radiative cooling coating is always lower than the ambient temperature under direct sunlight during the day, and can be cooled by about 5℃ on average, while lower than the temperature of the aluminum film by almost 12℃.

Lightweight Dual‑Functional Segregated Nanocomposite Foams for Integrated Infrared Stealth and Absorption‑Dominant Electromagnetic Interference Shielding

Lightweight infrared stealth and absorption-dominant electromagnetic interference(EMI)shielding materials are highly desirable in areas of aerospace,weapons,military and wearable electronics.Herein,lightweight and high-efficiency dual-functional segregated nanocomposite foams with microcellular structures are developed for integrated infrared stealth and absorption-dominant EMI shielding via the efficient and scalable supercritical CO_(2)(SC-CO_(2))foaming combined with hydrogen bonding assembly and compression molding strategy.The obtained lightweight segregated nanocomposite foams exhibit superior infrared stealth performances benefitting from the synergistic effect of highly effective thermal insulation and low infrared emissivity,and outstanding absorption-dominant EMI shielding performances attributed to the synchronous construction of microcellular structures and segregated structures.Particularly,the segregated nanocomposite foams present a large radiation temperature reduction of 70.2℃ at the object temperature of 100℃,and a significantly improved EM wave absorptivity/reflectivity(A/R)ratio of 2.15 at an ultralow Ti_(3)C_(2)T_(x) content of 1.7 vol%.Moreover,the segregated nanocomposite foams exhibit outstanding working reliability and stability upon dynamic compression cycles.The results demonstrate that the lightweight and high-efficiency dual-functional segregated nanocomposite foams have excellent potentials for infrared stealth and absorption-dominant EMI shielding applications in aerospace,weapons,military and wearable electronics.

Modulation of the cutoff wavelength in the spectra for solar selective absorbing coating based on high-entropy films

This paper demonstrates an intrinsic modulation of the cutoff wavelength in the spectra for solar selective absorbing coating based on high-entropy films.The(NiCuCrFeSi)N((NCCFS)N)films were deposited by a magnetron sputtering system.Rutherford backscattering spectroscopy analysis confirms the uniform composition and good homogeneity of these high-entropy films.The real and imaginary parts of the permittivity for the(NCCFS)N material are calculated on the basis of the reflectance spectral fitting results.A redshift cutoff wavelength of the reflectance spectrum with increasing nitrogen gas flow rate exists because of the different levels of dispersion when changing nitrogen content.To realize significant solar absorption,the film surface was reconstituted to match its impedance with air by designing a pyramid nanostructure metasurface.Compared with the absorptance of the as-deposited films,the designed metasurface obtains a significant improvement in solar absorption with the absorptance increasing from 0.74 to 0.99.The metasurfaces also show low mid-infrared emissions with thermal emittance that can be as low as 0.06.These results demonstrate a new idea in the design of solar selective absorbing surface with controllable absorptance and low infrared emission for high-efficiency photo-thermal conversion.

Global Warming and Its Multiple Causes

The global warming which preoccupies humanity,is still considered to be linked to a single cause which is the emission of greenhouse gases,CO2 in particular.In this article,we try to show that,on the one hand,the greenhouse effect(the radiative imprisonment to use the scientific term)took place in conjunction with the infrared radiation emitted by the earth.The surplus of CO2 due to the combustion of fossil fuels,but also the surplus of infrared emissions from artificialized soils contribute together or each separately,to the imbalance of the natural greenhouse effect and the trend of global warming.In addition,another actor acting directly and instantaneously on the warming of the ambient air is the heat released by fossil fuels estimated at 17415.1010 kWh/year inducing a rise in temperature of 0.122°C,or 12.2°C/century.

Investigation on Open-Circuit Voltage of an Efficiency-Boosting Solar Cell Technique Featuring V-Configuration

The V-Shaped Module (VSM) solar cell technology, which breaks the traditional concept of solar cell system, has been proven to enhance power conversion efficiency of some solar cells and has offered opportunities to increase generation power densities in area-limited applications. Compared to a planar cell system, the VSM has an additional opportunity to absorb photons and taps the potential of solar cells. In this study, the VSM, the proposed common technique enhancing efficiencies of various solar cells, was investigated by using commercially available multi-crystalline silicon solar cells. The VSM technique enables the efficiencies of the multi-crystalline silicon cells to increase from 13.4% to 20.2%, giving an efficiency boost of 51%. Though the efficiency of the cells increases, the open-circuit voltage of the cells decreases owing to the VSM technique. Furthermore, the obvious reduction in open-circuit voltage in the VSM was found and the phenomenon is explained for the first time.

Effect of fabrication conditions on the properties of indium tin oxide powders

This paper reports that indium tin oxide （ITO） crystalline powders are prepared by coprecipitation method. Fabrication conditions mainly as sintering temperature and Sn doping content are correlated with the phase, microstructure, infrared emissivity c and powder resistivity of indium tin oxides by means of x-ray diffraction, Fourier transform infrared, and transmission electron microscope. The optimum sintering temperature of 1350℃ and Sn doping content 6～8wt% are determined. The application of ITO in the military camouflage field is proposed.

THERMOGRAPHIC ASPECT ON LOADING A THIN-WALL PRESSURE VESSEL STEEL

The infrared emission of a high pressure vessel steel and two thin wall pressure vessel models have been investigated by use of vibro-thermography.The experimental infrared crack lengths were found to be agreed closely with the optical values during fatigue process.A possi- ble nondestructive testing method used to evaluate the pressure vessel has been given.

Visible transparent,infrared stealthy polymeric films with nanocoating of ITO@MXene enable efficient passive radiative heating and solar/electric thermal conversion

Visible transparent yet low infrared-emissivity(ε)polymeric materials are highly anticipated in many applications,whereas the fabrication of which remains a formidable challenge.Herein,visible transparent,flexible,and low-εpolymeric films were fabricated by nanocoating decoration of indium tin oxide(ITO)and MXene on polyethylene terephthalate(PET)film surface through magnetron sputtering and spray coating,respectively.The obtained PET-ITO@MXene(PET-IM)film exhibits lowεof 24.7%and high visible transmittance exceeding 50%,endowing it with excellent visible transparent infrared stealthy by reducing human skin radiation temperature from 32 to 20.8°C,and remarkable zero-energy passive radiative heating capability(5.7°C).Meanwhile,the transparent low-εPET-IM film has high solar absorptivity and electrical conductivity,enabling superior solar/electric to thermal conversion performance.Notably,the three heating modes of passive radiative and active solar/electric can be integrated together to cope with complex heating scenarios.These visible transparent low-εpolymeric films are highly promising in infrared stealth,building daylighting and thermal management,and personal precision heating.

Medium and high-entropy transition mental disilicides with improved infrared emissivity for thermal protection applications

Transition metal disilicides are widely used as heating elements and infrared emission coatings.However,the limited intrinsic infrared emissivity and high thermal conductivity are the main limitations to their applications as infrared emission coatings in the thermal protection system.To cope with these prob-lems,four medium and high-entropy transition metal disilicides,i.e.,(V_(0.25)Ta_(0.25)Mo_(0.25)W_(0.25))Si_(2)(ME-1),(Nb_(0.25)Ta_(0.25)Mo_(0.25)W_(0.25))Si_(2)(ME-2),(V_(0.2)Nb_(0.2)Ta_(0.2)Mo_(0.2)W_(0.2))Si_(2)(HE-1),and(Cr_(0.2)Nb_(0.2)Ta_(0.2)Mo_(0.2)W_(0.2))Si_(2)(HE-2),were designed and synthesized by spark plasma sintering method using transition metal binary disilicides as precursors.The introduction of multi-elements into transition metal disilicides not only im-proved the infrared emissivity but also reduced the electrical and thermal conductivity.Among them,(Cr_(0.2)Nb_(0.2)Ta_(0.2)Mo_(0.2)W_(0.2))Si_(2)(HE-2)had the lowest electrical conductivity of 3789 S cm-1,which is over one order of magnitude lower than that of MoSi_(2)(50000 S cm^(-1)),and total infrared emissivity of 0.42 at room temperature,which is nearly double of that of TaSi_(2).Benefiting from low electrical conductivity and phonon scattering due to lattice distortion,the medium and high-entropy transition metal disilicides also demonstrated a significant decline in thermal conductivity compared to their binary counterparts.Of all samples,HE-2 exhibited the lowest thermal conductivity of 6.4 W m^(−1)K^(−1).The high-entropy tran-sition metal disilicides also present excellent oxidation resistance at high temperatures.The improved infrared emissivity,reduced thermal conductivity,excellent oxidation resistance,and lower densities of these medium and high-entropy transition metal disilicides portend that they are promising as infrared emission coating materials for applications in thermal protection systems.

Optical transparent metamaterial structure for microwave-infrared-compatible camouflage based on indium tin oxide

A visible transparent metamaterial absorber was designed and fabricated with ultrabroadband microwave absorption and low infrared emissivity to meet the increasing demand for multispectral compatible camouflage. The absorber was fabricated with a low-infrared emissive layer at the top, a microwave-absorbing layer in the middle, and a reflective layer at the bottom, which were separated by polymethyl methacrylate plates. The absorber showed an average visible transmittance of 55%, infrared emissivity of ~0.37, and effective microwave absorption bandwidth of 32.1 GHz with a total thickness of 3.0 mm. Furthermore,microwave absorption exhibited wide-angle stability and polarization insensitivity characteristics. The mechanism of microwave attenuation was further explored through effective electromagnetic parameters as well as surface current, electric field, magnetic field, and energy loss density distributions. The experimental results were consistent with those of the simulations and calculations, indicating the potential of the designed metamaterial absorber for future applications in multispectral compatible camouflage.

The dusty and extremely red progenitor of the typeⅡsupernova 2023ixf in Messier 101

Stars with initial masses in the range of 8-25 solar masses are thought to end their lives as hydrogen-rich supernovae(SNeⅡ).Based on the pre-explosion images of Hubble space telescope(HST)and Spitzer space telescope,we place tight constraints on the progenitor candidate of type IIP SN 2023ixf in Messier 101.Fitting of the spectral energy distribution(SED)of its progenitor with dusty stellar spectral models results in an estimation of the effective temperature as 3091+422-258K.The luminosity is estimated as lg(L/L⊙)~4.83,consistent with a red supergiant(RSG)star with an initial mass of 12-1+2M⊙.The derived mass loss rate(6×10^(-6)-9×10^(-6)M⊙yr^(-1))is much lower than that inferred from the flash spectroscopy of the SN,suggesting that the progenitor experienced a sudden increase in mass loss when approaching the final explosion.In the infrared bands,significant deviation from the range of regular RSGs in the color-magnitude diagram and period-luminosity space of the progenitor star indicates enhanced mass loss and dust formation.Combined with new evidence of polarization at the early phases of SN 2023ixf,such a violent mass loss is likely a result of binary interaction.

Effect of far infrared radiation ceramics containing rare earth additives on surface tension of water

A kind of far infrared radiation ceramics was prepared by using silicate minerals, calcium carbonate and silicon dioxide as main raw materials, and cerium nitrate as additive. The structure of the ceramics and far infrared radiation properties on the surface tension of water were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and a tensiometer, respectively. It was showed that, after being sintered at 1160 ℃, the solid solution was formed by CeO2 and Fe2O3, thus the crystal parameters （c/a axis ratio） and interplanar spacing of Fe2O3 increased. The addition of cerium was regarded to improve the far infrared radiation of ceramics, and the maximum emissivity value in the range of 5-20 μm was 0.94. The surface tension of water gradually decreased with increasing radiation time.