- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Determination of high-temperature radiative properties of porous silica by combined image analysis, infrared spectroscopy and numerical simulation
摘要： The influence of the texture of fused silica glasses ? containing unconnected spherical bubbles ? on their thermal radiative properties was investigated by combining experimental measurements and numerical simulations. Exact numerical replicas of the porous samples were obtained from X-ray microtomography and image analysis showed that their bubble populations include two lognormal distributions of radii. The complex refractive index of the silica matrix was extracted from emittance measurements acquired at 1200 K on two reference silica samples. The comparison between direct measurements of the normal spectral emittance of the porous samples and those generated by applying Monte-Carlo ray tracing, performed on the numerical replicas, validated the use of geometric optics. The OH content of the porous samples was evaluated to be around 210 ppm. Ray tracing simulations carried out on a set of virtual samples having a similar texture proved to be a flexible means to address experimental limits when characterizing semi-transparent materials. The simulations also provided a natural framework to test the ability of the modified two-flux approximation model to predict the thermal radiative response of the porous silica investigated.
关键词： Radiative properties,X-ray microtomography,Porous silica glass,Spectral emittance,Monte-Carlo ray tracing
更新于2025-09-23 15:23:52
-
state of RbCs
摘要： We perform a high-resolution Fourier-transform spectroscopic study of the (4) 1Σ state of the RbCs molecule by applying two-step (4) 1Σ ← A 1Σ+ ～ b 3Π ← X 1Σ+ optical excitation followed by observation of the (4) 1Σ → X 1Σ+ laser-induced fluorescence (LIF) spectra. In many LIF progressions the collision-induced satellite rotational lines are observed, thus increasing the amount of term values and allowing us to estimate the Λ-doubling effect in the (4) 1Σ state. The direct potential fit (DPF) of experimental term values of 777 rovibronic levels of both 85RbCs and 87RbCs isotopologues is performed by means of the robust weighted nonlinear least-squares method. The DPF analysis based on the adiabatic approximation and analytical expanded Morse oscillator potential reveals numerous regular shifts in the measured level positions. The spectroscopic studies of the (4) 1Σ state are supported by the electronic structure calculations including the potential energy curves of the singlet- and triplet-state manifold and spin-allowed transition dipole moments. The subsequent estimates of radiative lifetimes and corresponding vibronic branching ratios elucidate a dominant contribution of the (4) 1Σ → A ～ b channel into the total radiative decay of the (4) 1Σ state. The relative intensity distributions simulated for (4) 1Σ → X 1Σ+ LIF progressions agree well with their observed counterparts even for the profoundly shifted levels of the entirely perturbed (4) 1Σ state. To get insight into the origin of the intramolecular perturbations, the relevant spin-orbit- and L-uncoupling electronic matrix elements are evaluated.
关键词： electronic structure calculations,Fourier-transform spectroscopy,RbCs molecule,perturbed state,direct potential fit,laser-induced fluorescence,radiative properties
更新于2025-09-23 15:23:52
-
Mean-Force Scattering Potential for Calculating Optical Properties of Dense Plasmas
摘要： We assess the relative importance of ionic structure on the opacity of dense plasmas by using the potential of mean force as a scattering potential within the Kubo-Greenwood formalism. We compare results from the potential of mean force, which includes realistic ionic structure, to results using an average atom potential, which includes only a crude treatment of ionic structure. Comparisons with less approximate but more expensive DFT-MD simulations for aluminum plasma reveal that the mean force generally improves agreement for DC conductivity. We also see improvement when applying the mean force to free-free transitions, whereas for bound-bound and bound-free transitions the mean force leads to poorer agreement on transition energies. Further, we assess the impact of accounting for correlations within the plasma at the temperature and density conditions relevant to iron opacity measurements at Sandia's Z machine facility [Bailey et al., Nature 517:56-59, 2015] and find that these correlations do not account for the discrepancy between the measurements and leading opacity calculations.
关键词： Warm Dense Matter,Radiative Properties,Ion Correlations,Average Atom
更新于2025-09-19 17:15:36
-
Spectral radiative properties of skeleton inner structure of ceramic foam based on ordered opal structure model
摘要： In this work, three dimensional periodic ordered opal structures are used to model the inner structures of skeleton of porous ceramic foam. The radii of close-packed spheres range from 0.7 μm to 1.7 μm. The spectral radiative properties are predicted by applying the FDTD method to analyze the radiative transfer inside the skeleton. The characteristics of re?ection spectra and transmission spectra with increasing incident wavelength are analyzed, including the different feature regions constituting the variation curves and the red shift of variation curve with growing size of close-packed spheres. The values and characteristics of absorption peaks surrounding the locations where size parameters are approximate to 1 are compared. The BSDF of scattering power are calculated further. The transformation of transmission in incident direction and re?ection in mirror direction is shown. Then, the distribution of radiation intensity in cross sections parallel to the incident light are compared and the variety from uniform distribution to anisotropic periodic distribution is summarized. The prediction and analysis are bene?t to further researches about the radiative transfer inside the porous ceramic foam.
关键词： Spectral radiative properties,Skeleton of ceramic foam,Opal structure,FDTD
更新于2025-09-19 17:15:36
-
Analysis on spectral radiative properties of micro-scaled rough ligament surface inside open-cell nickel foam
摘要： Accurately predicting the spectral radiative properties of ligament surface is vital for exploring the heat transfer inside open-cell foam materials. In this work, the complex morphology of ligament surface in open-cell nickel foam is reconstructed by analyzing the SEM scanning pictures of ligament surfaces. Then, the radiative parameters including the directional-hemispherical re?ectivity, directional-directional re?ectivity and proportion of specular re?ection of rough ligament surface in the waveband from visible to near infrared light are numerically predicted by applying the FDTD method. Furthermore, the effects of incident angle and wavelength on the predicted radiative properties are compared and summarized. Besides, a ?fth-degree polynomial is put forward for characterizing the directional-hemispherical re?ectivities under different incident angles and wavelengths. The distributions of directional-directional re?ectivities of ligament surface are compared and analyzed in order to predict the various value and dominated scope of re?ection peak in the specular re?ection direction. Additionally, the proportions of specular re?ection under different incident conditions are achieved properly and characterized by proposed mathematical formulas. This work is helpful for the multi-scale numerical prediction of radiative transfer inside open-cell nickel foams, which is bene?cial to further researches about engineering applications of open-cell foam materials.
关键词： Micro scaled morphology,Spectral radiative properties,Ligament surface,FDTD
更新于2025-09-19 17:13:59
-
Waveguide laser potency of samarium doped BaSO4-TeO2-B2O3 glasses: Evaluation of structural and optical qualities
摘要： A series of samarium ions (Sm3+) doped barium-sulfur-telluro-borate glasses of composition (70-x)B2O3-15BaSO4-15TeO2-xSm2O3 (x ranged from 0.0 to 2.5 mol%) was prepared by melt-quenching method and examined via diverse analytical tools. Influence of changing Sm3+ doping contents on the structures and optical attributes of the proposed glasses was determined. The XRD pattern of as-quenched samples verified their glassy states. The FTIR spectra displayed the vibrational modes of tellurites and borates functional groups in the corresponding range of 460–850 cm?1 and 700–1650 cm?1. The EDX elemental maps confirmed the homogeneous distribution of the traced elements in the glass matrix. The UV–Vis–NIR absorption spectra of glasses exhibited nine distinct bands compatible with the transition from lower 6H5/2 state to the excited 6P3/2, 4I11/2, 6F11/2, 6F9/2, 6F7/2, 6F5/2, 6F3/2, 6H15/2 and 6F1/2 states of Sm3+. The photoluminescence spectra showed four emission bands allotted to magnetic dipole 4G5/2 → 6H5/2 (moderate green at 562 nm), electric dipole dominated 4G5/2 → 6H7/2 (intense orange at 598 nm), electric dipole 4G5/2 → 6H9/2 (moderate red at 645 nm) and 4G5/2 → 6H11/2 (weak red at 703 nm) transitions in Sm3+, respectively. Glasses containing Sm2O3 contents above 1.0 mol % disclosed luminescence intensity quenching. Evaluated Judd-Ofelt intensity parameters Ω2, Ω4, and Ω6 were discerned from 1.48 × 10?20–4.2 × 10?20 cm2, 2.31 × 10?20–4.31 × 10?20 cm2 and 1.26 × 10?20–1.99 × 10?20 cm2 respectively. Furthermore, the lifetime of the samples decreases with increase in Sm3+ contents as unraveled by decay curve analysis. The achieved excellent spectroscopic properties of the proposed glass composition suggested their effectiveness as visible laser for waveguide applications.
关键词： Borate glasses,Samarium ions,Waveguide laser,Bonding parameter,Radiative properties
更新于2025-09-11 14:15:04
-
Eu3+-doped fluoro-telluroborate glasses as red-emitting components for W-LEDs application
摘要： From 0.1 up to 2.5 mol% Eu3t-doped fluro-telluroborate glasses as red light-emitting components for white-light-emitting diodes (WLEDs) were investigated. Non-periodicity in the atomic arrangements was studied through the XRD pattern. The photoluminescence (PL) spectra were recorded under blue light (464 nm) excitation and analyzed. All the PL spectra exhibit an intense peak at 612 nm for 5D0 → 7F2 transition, revealing their red photoemission. Optimal PL emissions were achieved for 1.0 mol% Eu3t-doped sample. The CIE chromaticity coordinates for all the glasses (x ? ~0.69, y ? ~0.30) fall within the red color region. The J?O parameters (Ω2, Ω4) were calculated following the emission spectra of Eu3t-doped samples and the intensity parameters (Ω2>Ω4), as well as the high asymmetry ratio (R/O), indicate the low ionicity in all the studied glasses. Using the J-O parameters, several radiative features like total emission transition probability (AT), branching ratios (radiative (βR) & experimental (βexp)), stimulated emission cross-section (σEP), gain bandwidth (σEP × λeff), and optical gain (σEP × τrad) were evaluated. All the luminescence decay curves fit well to non-exponential function and decay times were decreased at Eu3t concentration >0.5 mol%. The evaluated σEP = 19.684 × 10?21 cm2, βexp = 0.759, τexp = 1.325 ms, minimum non-radiative relaxation, WNR = 296/s, and 60.78% of quantum efficiency (η) for 1.0 mol% Eu3t-doped glass for 5D0 → 7F2 transition indicates its promising features for red light-emitting optical devices and also as a red component in WLEDs.
关键词： Luminescence features,Decay lifetimes,Eu3t,White LEDs,Radiative properties,CIE chromaticity coordinates
更新于2025-09-11 14:15:04
-
A feasible and accurate method for calculating the radiative properties of soot particle ensembles in flames
摘要： The accurate calculation of the radiative properties of soot particle ensembles in flames needs to exactly reconstruct the geometric structures of all soot particles and accurately calculate the radiative properties of all soot particles based on their reconstructed geometric structures. However, the enormous number of soot particles in real ensembles makes it practically impossible to implement this task. To solve this problem, a feasible and accurate method is proposed for calculating their main radiative properties except scattering matrix and depolarization ratio. Experimental and numerical results show that soot particles with the same number of primary particles from the same sampling point can be considered as equivalent soot particles, which have almost the same volume, absorption cross-section, scattering cross-section and scattering asymmetry cross-section. Moreover, the average values of these quantities of equivalent soot particles approximately linearly increase with the number of primary particles. These findings can dramatically reduce the difficulty of reconstruction and calculation. The radiative properties of 37 different morphologies of soot particle ensembles in the visible and near-infrared regions (λ = 0.40-3.00 μm) are calculated using this method, and it is shown that the increasing of the average diameter of primary particles and the average number of primary particles per soot particle can enhance the absorption coefficient, scattering coefficient, asymmetry factor and single-scattering albedo of soot particle ensembles 0.1-900 times. In addition, these radiative properties are found to decrease by at least 70% with the increasing of λ from 0.40 μm to 3.00 μm.
关键词： Incident wavelength,Radiative properties,Soot particle ensemble,Particle structure
更新于2025-09-10 09:29:36