NiCr_2O_4(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 ...NiCr_2O_4(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℃.展开更多
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 applica...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.展开更多
LaMgAl_(11)O_(19)(LMA),characterized by high melting point,low density and thermal conductivity as well as good infrared emissivity,is regarded as a potential candidate for the thermal protection of hypersonic vehicle...LaMgAl_(11)O_(19)(LMA),characterized by high melting point,low density and thermal conductivity as well as good infrared emissivity,is regarded as a potential candidate for the thermal protection of hypersonic vehicles.Nevertheless,the unsatisfied phase stability at high temperature results in declining of the emissivity below 6μm,which limits the extensive applications of LaMgAl_(11)O_(19).In order to overcome this obstacle,three dense bulk high-entropy ceramics,(La_(0.2)Nd_(0.2)Gd_(0.2)Sm_(0.2)Pr_(0.2))MgAl_(11)O_(19)(HE LMA-1),(La_(0.2)Nd_(0.2)Gd_(0.2)Sm_(0.2)Dy_(0.2))Mg Al_(11)O_(19)(HE LMA-2)and La(Mg_(0.2)Fe_(0.2)Co_(0.2)Ni_(0.2)Zn_(0.2))Al_(11)O_(19)(HE LMA-3),were designed and successfully prepared through solid state reaction at 1700℃for 4 h in one step.XRD analyses show that the phase compositions of HE LMA-1,HE LMA-2 and HE LMA-3 are single-phase solid solutions with the relative density of 95.61%,95.49%and 94.31%,respectively.Heat treatment experiments demonstrate that the phase composition of HE LMA-1 remains a single phase after high-temperature heating,while second phase appears in other two samples.The stability of HE LMA-1 is attributed to small average size differenceδ(~4%)of constitute elements.Intriguingly,the average emissivity of HE LMA-1 in the range of 3-6μm reaches 0.9,which is significantly higher than that of LMA and other two HE LMA samples.The emissivity of all samples remains above 0.95 from 6 to 10μm.In the far infrared region(10-14μm),although the emissivity of these specimens decreases slightly,it still exceeds 0.85.The UV-Vis absorption spectra indicate that the formation of many discrete impurity energy levels with small intervals in HE LMA-1 promotes the f electrons to transit between adjacent impurity energy levels and conduction band,which enhances the infrared emission of HE LMA-1 below 6μm.In a word,with improved phase stability and thermal emissivity in infrared range,high-entropy REMgAl_(11)O_(19),especially(La_(0.2)Nd_(0.2)Gd_(0.2)Sm_(0.2)Pr_(0.2))MgAl_(11)O_(19)(HE LMA-1),is a promising candidate in thermal protection coatings of hypersonic vehicles.展开更多
Sn-doped ZnO particles were successfully synthesized by chemical co-precipitation method.Their morphology,phase,microstructure and infrared emissivity were characterized.The results show that the Sn-doped ZnO particle...Sn-doped ZnO particles were successfully synthesized by chemical co-precipitation method.Their morphology,phase,microstructure and infrared emissivity were characterized.The results show that the Sn-doped ZnO particles are of ellipsoid shape,their crystalline structure changed with thermal process temperature,the optimal thermal process temperature and Sn-doped proportion are 1000℃ and 15%,respectively,the minimum emissivity values are 0.42,0.28,0.46 and 0.48 corresponding to the infrared wavelengths of 0~∞,3~5,8~14 and 14~20 μm,which indicates that the Sn-doped ZnO particles have the application potential as low infrared emissivity material.展开更多
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 ...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.展开更多
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)...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℃.展开更多
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,an...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.展开更多
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 a...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.展开更多
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 s...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.展开更多
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 gree...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.展开更多
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 i...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.展开更多
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 e...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).展开更多
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...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.展开更多
We report the structural and photoluminescence(PL) properties of Nd^(3+)-doped Y_(2)O_(3)-SiO_(2) powders(Y_(2)O_(3)-SiO_(2):Nd^(3+)) as functions of annealing temperature and Nd^(3+) ion doping concentration.Y_(2)O_(...We report the structural and photoluminescence(PL) properties of Nd^(3+)-doped Y_(2)O_(3)-SiO_(2) powders(Y_(2)O_(3)-SiO_(2):Nd^(3+)) as functions of annealing temperature and Nd^(3+) ion doping concentration.Y_(2)O_(3)-SiO_(2):Nd^(3+)powders were prepared using the high-energy ball-milling(HEBM) method,and their structural and PL properties were investigated using X-ray diffraction(XRD),Fourier transform infrared(FTIR) spectroscopy,and PL spectroscopy.The XRD results reveal a cubic phase without impurities,and the peak broadening decreases with an increase in annealing temperature due to the increase in the crystallite size.The PL emission intensity increases with an increase in annealing temperature.The highest PL emission intensity is observed for the 300-min milled mixture annealed at 1000℃ for 1 h with a Nd^(3+) concentration of 1 mol%.The PL peaks excited by 800 nm radiation were detected,centered at 1080 nm(^(4)F_(3/2)→^(4)I_(11/2)) and 1350 nm(^(4)F_(3/2)→^(4)I_(13/2)).展开更多
Conventional photoluminescence(PL)yields at most one emitted photon for each absorption event.Downconversion(or quantum cutting)materials can yield more than one photon by virtue of energy transfer processes between l...Conventional photoluminescence(PL)yields at most one emitted photon for each absorption event.Downconversion(or quantum cutting)materials can yield more than one photon by virtue of energy transfer processes between luminescent centers.In this work,we introduce Gd2O2S:Tm^(3+) as a multi-photon quantum cutter.It can convert near-infrared,visible,or ultraviolet photons into two,three,or four infrared photons of,1800 nm,respectively.The cross-relaxation steps between Tm^(3+) ions that lead to quantum cutting are identified from(time-resolved)PL as a function of the Tm^(3+) concentration in the crystal.A model is presented that reproduces the way in which the Tm^(3+) concentration affects both the relative intensities of the various emission lines and the excited state dynamics and providing insight in the quantum cutting efficiency.Finally,we discuss the potential application of Gd2O2S:Tm^(3+) for spectral conversion to improve the efficiency of next-generation photovoltaics.展开更多
Near infrared to near infrared(NIR-NIR)photo-stimulated persistent luminescence(PSPL)has shown excellent potential in high-resolution bioimaging for deep tissues.However,the PSPL in NIR-Ⅱregion(900-1700 nm)is still l...Near infrared to near infrared(NIR-NIR)photo-stimulated persistent luminescence(PSPL)has shown excellent potential in high-resolution bioimaging for deep tissues.However,the PSPL in NIR-Ⅱregion(900-1700 nm)is still lacking.In this work,Ca_(2)Ga_(2)GeO_(7):Yb^(3+),Tb^(3+)(CGGYT)phosphor with unique lowdimensional crystal structure was synthesized by high-temperature solid-state reaction.Thanks to the carriers transferring from deep traps to shallow ones induced by low energy light,the 978 nm PSPL originating from ^(2)F_(5/2) to ^(2)F_(7/2) transition of Yb^(3+)induced by multimode stimulating(980 nm or WLED)is successfully realized after pre-excited by UV lamp.The NIR PSPL of the specimen can be repeatedly stimulated after placed in dark for 12 h.Moreover,the results indicate that codoping with Tb^(3+)can significantly enhance the NIR-ⅡPSPL owing to the quantum cutting persistent energy transfer(QC PET)from Tb^(3+)to Yb^(3+).Our study points to a new direction for the future development of multimode PSPL materials for bioimaging or multimode optical storage applications.展开更多
The intermetallic synergy plays a critical role in exploring the chemical-physical properties of metal nanoclusters.However,the controlled doping or layer-by-layer alloying of atom-precise metal nanoclusters(NCs)has l...The intermetallic synergy plays a critical role in exploring the chemical-physical properties of metal nanoclusters.However,the controlled doping or layer-by-layer alloying of atom-precise metal nanoclusters(NCs)has long been a challenging pursuit.In this work,two novel alloy nanoclusters[PPh_(4)]_(4)[Ag_(32)Cu_(18)(PFBT)_(36)]((AgCu)_(50))and[PPh_(4)]_(4)[Au_(12)Ag_(20)Cu_(18)(PFBT)_(36)](Au_(12)(AgCu)_(38)),where PFBT is pentafluorobenzenethiolate,with shell-by-shell configuration of M_(12)@Ag_(20)@Cu_(18)(PFBT)_(36)(M=Ag/Au)were synthesized by a facile one-pot co-reduction method.Notably,a fingerprint library of[Ag_(50)−xCux(PFBT)_(36)]^(4−)(x=0 to 50)from Ag_(50)to Cu_(50)has been successfully established as revealed by electrospray ionization mass spectrometry.Single-crystal X-ray diffraction analysis of trimetallic Au_(12)(AgCu)_(38)confirmed the layer-by-layer alloying under reducing conditions.What is more,(AgCu)_(50)and Au12(AgCu)_(38)both show broad photoluminescence(PL)peak in the second near-infrared(NIR-II)window,and the Au doping in the innermost shell considerably enhances the photoluminescence intensity.This work not only offers an insight in the process of metal cluster alloying but also provides a platform to study the doping-directed PL properties in the multimetallic cluster system.展开更多
The formation of amyloid plaques usually occurs in the early-stage of Alzheimer’s disease(AD).Stimulated emission depletion(STED)imaging provided a powerful tool for visualizing amyloid structures on the nanometer sc...The formation of amyloid plaques usually occurs in the early-stage of Alzheimer’s disease(AD).Stimulated emission depletion(STED)imaging provided a powerful tool for visualizing amyloid structures on the nanometer scale.However,many commercial probes adopted in detecting amyloid fibrils are inapplicable to STED imaging,owing to their unmatched absorption and emission wavelengths,small Stokes'shift,easy photo-bleaching,etc.Herein,we demonstrated a polarity-activated STED probe based on an intramolecular charge transfer donor(D)-7c-acceptor(A)compound.The electron-rich carbazole group and the electron-poor pyridinium bromide group,linked by 7i-conjugated thiophen-bridge,ensure strong near infrared(NIR)emission with a Stokes'shift larger than 200 nm.The tiny change in polarity before and after binding with amyloid plaques leads to a transition from weakly emission charge-transfer(CT)state(Φ<0.04)to highly emissive locally-excited(LE)state(Φ=0.57),giving rise to a fluorescence Turn-On probe.Together with large Stokes'shift,good photostability and high depletion efficiency,the super-resolution imaging of the formation and morphology of amyloid fibrils in vitro based on this probe was realized with a lateral spatial resolution better than 33 nm at an extremely low depletion power.Moreover,the ex-vivo super-resolution imaging of(E)-1-butyl-4(2-(5-(9-ethyl-9Hcarbazol-3-yl)thiophen-2-yl)vinyl)pyridinium bromide(CTPB)probe in Aβ plaques in the brain slices of a Tg mouse was demonstrated.This research provides a demonstration of the super resolution imaging probe of amyloid fibrils based on polarity-response mechanism,providing a new approach to the development of future amyloid probes.展开更多
基金Funded by the Scientific and Technological Research Projects for Education Department of Hubei Province(Q20161407)
文摘NiCr_2O_4(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℃.
基金This work was financially supported by the National Natu-ral Science Foundation of China(Nos.51972082,51972089,and 52172041)the Key Program of National Natural Science Foun-dation of China(No.52032003).
文摘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.
基金supported by the National Natural Science Foundation of China under Grant Nos.51772027 and 51972089。
文摘LaMgAl_(11)O_(19)(LMA),characterized by high melting point,low density and thermal conductivity as well as good infrared emissivity,is regarded as a potential candidate for the thermal protection of hypersonic vehicles.Nevertheless,the unsatisfied phase stability at high temperature results in declining of the emissivity below 6μm,which limits the extensive applications of LaMgAl_(11)O_(19).In order to overcome this obstacle,three dense bulk high-entropy ceramics,(La_(0.2)Nd_(0.2)Gd_(0.2)Sm_(0.2)Pr_(0.2))MgAl_(11)O_(19)(HE LMA-1),(La_(0.2)Nd_(0.2)Gd_(0.2)Sm_(0.2)Dy_(0.2))Mg Al_(11)O_(19)(HE LMA-2)and La(Mg_(0.2)Fe_(0.2)Co_(0.2)Ni_(0.2)Zn_(0.2))Al_(11)O_(19)(HE LMA-3),were designed and successfully prepared through solid state reaction at 1700℃for 4 h in one step.XRD analyses show that the phase compositions of HE LMA-1,HE LMA-2 and HE LMA-3 are single-phase solid solutions with the relative density of 95.61%,95.49%and 94.31%,respectively.Heat treatment experiments demonstrate that the phase composition of HE LMA-1 remains a single phase after high-temperature heating,while second phase appears in other two samples.The stability of HE LMA-1 is attributed to small average size differenceδ(~4%)of constitute elements.Intriguingly,the average emissivity of HE LMA-1 in the range of 3-6μm reaches 0.9,which is significantly higher than that of LMA and other two HE LMA samples.The emissivity of all samples remains above 0.95 from 6 to 10μm.In the far infrared region(10-14μm),although the emissivity of these specimens decreases slightly,it still exceeds 0.85.The UV-Vis absorption spectra indicate that the formation of many discrete impurity energy levels with small intervals in HE LMA-1 promotes the f electrons to transit between adjacent impurity energy levels and conduction band,which enhances the infrared emission of HE LMA-1 below 6μm.In a word,with improved phase stability and thermal emissivity in infrared range,high-entropy REMgAl_(11)O_(19),especially(La_(0.2)Nd_(0.2)Gd_(0.2)Sm_(0.2)Pr_(0.2))MgAl_(11)O_(19)(HE LMA-1),is a promising candidate in thermal protection coatings of hypersonic vehicles.
文摘Sn-doped ZnO particles were successfully synthesized by chemical co-precipitation method.Their morphology,phase,microstructure and infrared emissivity were characterized.The results show that the Sn-doped ZnO particles are of ellipsoid shape,their crystalline structure changed with thermal process temperature,the optimal thermal process temperature and Sn-doped proportion are 1000℃ and 15%,respectively,the minimum emissivity values are 0.42,0.28,0.46 and 0.48 corresponding to the infrared wavelengths of 0~∞,3~5,8~14 and 14~20 μm,which indicates that the Sn-doped ZnO particles have the application potential as low infrared emissivity material.
文摘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.
文摘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℃.
基金Financial support of the National Natural Science Foundation of China(No.52003248)the China Postdoctoral Science Foundation(Nos.2018M642780 and 2021T140613)+1 种基金the Opening Project of State Key Laboratory of Polymer Materials Engineering(Sichuan University)(No.sklpme2019-4-31)the Key Research and Development and Promotion projects of Henan Province(No.202102210032)are gratefully acknowledged.
文摘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.
文摘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.
基金the National Natural Science Foundation of China(Nos.51732001,U1832219,and 51972013)Beijing Natural Science Foundation(No.2182035)+1 种基金the Fundamental Research Funds for the Central Universities,the Program of China Scholarships Council(No.201806020161)the Academic Excellence Foundation of Beihang University(BUAA)for Ph.D.Students.
文摘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.
文摘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.
文摘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.
文摘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).
基金supported by the National Natural Science Foundation of China(Grant Nos.12288102,12033003,and 11633002)the Ma Huateng Foundation+4 种基金the Scholar Program of Beijing Academy of Science and Technology(Grant No.DZ:BS202002)the Tencent Xplorer Prizesponsored(in part)by the Chinese Academy of Sciences(CAS)through a grant to the CAS South America Center for Astronomy(CASSACA)in Santiago,ChileFunding for the LJT has been provided by the CAS and the People’s Government of Yunnan Province。
文摘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.
基金The authors would like to thank the financial support by a 2019 research fund from Chosun University.
文摘We report the structural and photoluminescence(PL) properties of Nd^(3+)-doped Y_(2)O_(3)-SiO_(2) powders(Y_(2)O_(3)-SiO_(2):Nd^(3+)) as functions of annealing temperature and Nd^(3+) ion doping concentration.Y_(2)O_(3)-SiO_(2):Nd^(3+)powders were prepared using the high-energy ball-milling(HEBM) method,and their structural and PL properties were investigated using X-ray diffraction(XRD),Fourier transform infrared(FTIR) spectroscopy,and PL spectroscopy.The XRD results reveal a cubic phase without impurities,and the peak broadening decreases with an increase in annealing temperature due to the increase in the crystallite size.The PL emission intensity increases with an increase in annealing temperature.The highest PL emission intensity is observed for the 300-min milled mixture annealed at 1000℃ for 1 h with a Nd^(3+) concentration of 1 mol%.The PL peaks excited by 800 nm radiation were detected,centered at 1080 nm(^(4)F_(3/2)→^(4)I_(11/2)) and 1350 nm(^(4)F_(3/2)→^(4)I_(13/2)).
基金Financial support from the National Science Foundation of China(51125005 and 51472088)is gratefully acknowledgedDechao Yu thanks the China Scholarship Council(CSC,File No.201206150022)for a scholarshipThis work is part of the research program of the‘Stichting voor Fundamenteel Onderzoek der Materie(FOM)’,which is financially supported by the‘Nederlandse Organisatie voor Wetenschappelijk Onderzoek(NWO)’.
文摘Conventional photoluminescence(PL)yields at most one emitted photon for each absorption event.Downconversion(or quantum cutting)materials can yield more than one photon by virtue of energy transfer processes between luminescent centers.In this work,we introduce Gd2O2S:Tm^(3+) as a multi-photon quantum cutter.It can convert near-infrared,visible,or ultraviolet photons into two,three,or four infrared photons of,1800 nm,respectively.The cross-relaxation steps between Tm^(3+) ions that lead to quantum cutting are identified from(time-resolved)PL as a function of the Tm^(3+) concentration in the crystal.A model is presented that reproduces the way in which the Tm^(3+) concentration affects both the relative intensities of the various emission lines and the excited state dynamics and providing insight in the quantum cutting efficiency.Finally,we discuss the potential application of Gd2O2S:Tm^(3+) for spectral conversion to improve the efficiency of next-generation photovoltaics.
基金Project supported by the National Natural Science Foundation of China-Yunnan Joint Fund(U1902222)the National Natural Science Foundation of China(11774138,11664022,51862020 and 11804255)the Natural Science Foundation of Yunnan Province(2019HC016)。
文摘Near infrared to near infrared(NIR-NIR)photo-stimulated persistent luminescence(PSPL)has shown excellent potential in high-resolution bioimaging for deep tissues.However,the PSPL in NIR-Ⅱregion(900-1700 nm)is still lacking.In this work,Ca_(2)Ga_(2)GeO_(7):Yb^(3+),Tb^(3+)(CGGYT)phosphor with unique lowdimensional crystal structure was synthesized by high-temperature solid-state reaction.Thanks to the carriers transferring from deep traps to shallow ones induced by low energy light,the 978 nm PSPL originating from ^(2)F_(5/2) to ^(2)F_(7/2) transition of Yb^(3+)induced by multimode stimulating(980 nm or WLED)is successfully realized after pre-excited by UV lamp.The NIR PSPL of the specimen can be repeatedly stimulated after placed in dark for 12 h.Moreover,the results indicate that codoping with Tb^(3+)can significantly enhance the NIR-ⅡPSPL owing to the quantum cutting persistent energy transfer(QC PET)from Tb^(3+)to Yb^(3+).Our study points to a new direction for the future development of multimode PSPL materials for bioimaging or multimode optical storage applications.
基金supported by the National Natural Science Foundation of China(Nos.92061201,21825106,and 21801228)the Program for Innovative Research Team(in Science and Technology)in Universities of Henan Province(No.19IRTSTHN022)Zhengzhou University。
文摘The intermetallic synergy plays a critical role in exploring the chemical-physical properties of metal nanoclusters.However,the controlled doping or layer-by-layer alloying of atom-precise metal nanoclusters(NCs)has long been a challenging pursuit.In this work,two novel alloy nanoclusters[PPh_(4)]_(4)[Ag_(32)Cu_(18)(PFBT)_(36)]((AgCu)_(50))and[PPh_(4)]_(4)[Au_(12)Ag_(20)Cu_(18)(PFBT)_(36)](Au_(12)(AgCu)_(38)),where PFBT is pentafluorobenzenethiolate,with shell-by-shell configuration of M_(12)@Ag_(20)@Cu_(18)(PFBT)_(36)(M=Ag/Au)were synthesized by a facile one-pot co-reduction method.Notably,a fingerprint library of[Ag_(50)−xCux(PFBT)_(36)]^(4−)(x=0 to 50)from Ag_(50)to Cu_(50)has been successfully established as revealed by electrospray ionization mass spectrometry.Single-crystal X-ray diffraction analysis of trimetallic Au_(12)(AgCu)_(38)confirmed the layer-by-layer alloying under reducing conditions.What is more,(AgCu)_(50)and Au12(AgCu)_(38)both show broad photoluminescence(PL)peak in the second near-infrared(NIR-II)window,and the Au doping in the innermost shell considerably enhances the photoluminescence intensity.This work not only offers an insight in the process of metal cluster alloying but also provides a platform to study the doping-directed PL properties in the multimetallic cluster system.
基金This work was supported by the Ministry of Science and Technology of China(Nos.2017YFA0204503 and 2018YFA0704805)the National Natural Science Foundation of China(Nos.21503139,21573251,21673144,21873065,21833005,81970425 and 21790364)+5 种基金the Beijing Natural Science Foundation of China(No.2192011)the High-level Teachers in Bejing Municipal Universities in the Period of 13^th Five-year Plan(Nos.IDHT20180517 and CIT&TCD20180331)the Open Fund of the State Key Laboratory of Integrated Optoelectronics(No.IOSKL2019KF01)Capacity Building for Sci-Tech Innovation-Fundamental Scientific Research Funds(Nos.025185305000/210,009/19530050162 and 19530012018)Youth Innovative Research Team of Capital Normal University(No,009/19530050148)Beijing Advanced Innovation Center for Imaging Theory and Technology(No.009/19530011009).
文摘The formation of amyloid plaques usually occurs in the early-stage of Alzheimer’s disease(AD).Stimulated emission depletion(STED)imaging provided a powerful tool for visualizing amyloid structures on the nanometer scale.However,many commercial probes adopted in detecting amyloid fibrils are inapplicable to STED imaging,owing to their unmatched absorption and emission wavelengths,small Stokes'shift,easy photo-bleaching,etc.Herein,we demonstrated a polarity-activated STED probe based on an intramolecular charge transfer donor(D)-7c-acceptor(A)compound.The electron-rich carbazole group and the electron-poor pyridinium bromide group,linked by 7i-conjugated thiophen-bridge,ensure strong near infrared(NIR)emission with a Stokes'shift larger than 200 nm.The tiny change in polarity before and after binding with amyloid plaques leads to a transition from weakly emission charge-transfer(CT)state(Φ<0.04)to highly emissive locally-excited(LE)state(Φ=0.57),giving rise to a fluorescence Turn-On probe.Together with large Stokes'shift,good photostability and high depletion efficiency,the super-resolution imaging of the formation and morphology of amyloid fibrils in vitro based on this probe was realized with a lateral spatial resolution better than 33 nm at an extremely low depletion power.Moreover,the ex-vivo super-resolution imaging of(E)-1-butyl-4(2-(5-(9-ethyl-9Hcarbazol-3-yl)thiophen-2-yl)vinyl)pyridinium bromide(CTPB)probe in Aβ plaques in the brain slices of a Tg mouse was demonstrated.This research provides a demonstration of the super resolution imaging probe of amyloid fibrils based on polarity-response mechanism,providing a new approach to the development of future amyloid probes.
