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Express: Modelling of Carbon Monoxide Two-Photon Laser-Induced Fluorescence (LIF) Spectra at High Temperature and Pressure
摘要： In this study, quantitative model of two-photon excitation and fluorescence spectra of carbon monoxide based on up-to-date spectroscopic constants collected during an extensive literature survey was developed. This semi-classical model takes into account H?nl–London factors, quenching effects (collisional broadening and shift), ionization and stark effect (broadening and shift), whereas predissociation is neglected. It was specifically developed to first reproduce with a high confidence level the behavior of our experimental spectra obtained from laser-induced fluorescence (LIF) measurements, and then to allow us to extrapolate the fluorescence signal amplitude in other conditions than those used in these experiments. Synthetic two-photon excitation and fluorescence spectra of CO were calculated to predict the fluorescence signal at high pressures and temperatures, which are representative of gas turbine operating conditions. Comparison between experimental and calculated spectra is presented. Influence of temperature on both excitation and fluorescence spectra shapes and amplitudes is well reproduced by the simulated ones. It is then possible to estimate flame temperature from the comparison between experimental and calculated shapes of numerical excitation spectra. Influence of pressure on both excitation and fluorescence spectra was also investigated. Results show that for temperature below 600 K and pressure above 0.1 MPa, the usual Voigt profile is not suitable to reproduce the shape of the excitation spectrum. We found that the Lindholm profile is well suited to reproduce the pressure-dependence of the spectrum in the range 0.1 to 0.5 MPa at 300 K, and 0.1 to 0.7 MPa at 860 K. Beyond 0.7 MPa, in this temperature range, it is shown that the Lindholm profile does no longer match the spectral profiles, in particularly the red wing. Further analyses taking into account the line mixing phenomenon at higher pressure are thus discussed.
关键词： spectroscopy,combustion,modeling,LIF,Laser-induced fluorescence,carbon monoxide
更新于2025-09-19 17:13:59
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Express: Time-Gated Single-Shot Picosecond Laser-Induced Breakdown Spectroscopy (ps-LIBS) for Equivalence-Ratio Measurements
摘要： Time-gated picosecond laser-induced breakdown spectroscopy (ps-LIBS) for the determination of local equivalence ratios in atmospheric-pressure adiabatic methane–air flames is demonstrated. Traditional LIBS for equivalence-ratio measurements employ nanosecond (ns)-laser pulses, which generate excessive amounts of continuum, reducing measurement accuracy and precision. Shorter pulse durations reduce the continuum emission by limiting avalanche ionization. Furthermore, by contrast the use of femtosecond lasers, plasma emission via picosecond-laser excitation has high signal-to-noise ratio (S/N), allowing single-shot measurements suitable for equivalence-ratio determination in turbulent reacting flows. We carried out an analysis of the dependence of the plasma emission ratio Hα (656 nm)/NII (568 nm) on laser energy and time-delay for optimization of S/N and minimization of measurement uncertainties in the equivalence ratios. Our finding shows that higher laser energy and shorter time delay reduces measurement uncertainty while maintaining high S/N. In addition to atmospheric-pressure flame studies, we also examine the stability of the ps-LIBS signal in a high-pressure nitrogen cell. The results indicate that the plasma emission and spatial position could be stable, shot-to-shot, at elevated pressure (up to 40 bar) using a lower excitation energy. Our work shows the potential of using ps-duration pulses to improve LIBS-based equivalence-ratio measurements, both in atmospheric and high-pressure combustion environments.
关键词： time-resolved spectroscopy,combustion diagnostics,Laser-induced breakdown spectroscopy,picosecond phenomena,LIBS
更新于2025-09-19 17:13:59
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Direct Laser Etching Free‐Standing MXene‐MoS <sub/>2</sub> Film for Highly Flexible Micro‐Supercapacitor
摘要： The biomass hydrolysis residue (BHR) is the residue consisting of mainly lignin after the biomass-to-ethanol process. A combustion kinetic comparison of the biomass material (BM), BHR, and three main components (lignin, cellulose, and hemicellulose) is studied by thermogravimetry (TG) using the Kissinger method and Flynn?Wall?Ozawa (FWO) method under five different heating rates. The results show that the ignition temperature (Ti) and burnout temperature (Tb) of BHR are both higher than those of BM. BM burns more sufficient than BHR because it contains more fixed carbon content. The results show that the activation energy calculated by the Kissinger method for the corn cob hydrolysis residue (CCHR), corn straw hydrolysis residue (CSHR) and corn cob (CC) is 188.08, 192.76 and 205.76 kJ/mol, respectively. The results calculated by the FWO method show that, when the mass conversion (α) is small, EBHR > EBM, as α increases, E of BM gradually exceeds that of BHR. This could explain the phenomenon why BHR ignites earlier than BM but burns out later than BM. The power law (P4 and P2) reaction models are proper to describe the experimental behavior of BHR and BM, respectively. This paper also verifies that, on the premise of an accurate measurement of the three main components in BM and BHR, the TG curves and kinetic parameters of BM and BHR can be predicted.
关键词： thermogravimetry,combustion kinetics,biomass hydrolysis residue,Flynn?Wall?Ozawa method,Kissinger method
更新于2025-09-19 17:13:59
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Paint Removal with Pulsed Laser: Theory Simulation and Mechanism Analysis
摘要： This paper studies paint removal using laser technology. A finite element model was created using COMSOL Multiphysics software, and the temperature field generated during the cleaning process was analyzed and verified. Laser paint removal behavior was investigated using a fiber laser, and its mechanism studied by combining Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. In-depth analysis of this relatively new technology could provide the theoretical basis for industrial application. The results of this study show that, when compared to the original paint layer, the infrared absorption spectrum of the cleaned surface had two additional two peaks—1333.36 cm?1 and 678.82 cm?1. In addition, there was a decrease in C element content on the treated surface and an increase in O content. In addition, new organic and complex compounds were formed on the cleaned surface as a result of bond cleavage and rearrangement. Furthermore, paint particles of varying sizes and shapes were produced by the impact of plasma shock. Under high-energy laser irradiation, the paint layer underwent combustion, resulting in spherical nanoparticles of uniform shape.
关键词： plasma,mechanism,combustion,paint removal,chemical bond,pulsed laser
更新于2025-09-19 17:13:59
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AIP Conference Proceedings [AIP Publishing DAE SOLID STATE PHYSICS SYMPOSIUM 2018 - Hisar, Haryana, India (18–22 December 2018)] DAE SOLID STATE PHYSICS SYMPOSIUM 2018 - Mixed fuel approach for the fabrication of TiO2:Dy3+(1-11?mol%) nanophosphors: Applications towards wLED and latent finger print detection
摘要： The pure and Dy3+(1-11 mol%) ions doped TiO2 nanophosphors (NPs) were prepared by solution combustion method using grouping of fuels; glycine and ammonium acetate. PXRD studies establishes that the pure and doped samples show rutile and anatase phases respectively. The Raman spectra illustrates that the absorption peaks noticed at ～ 142, 446 and 609 cm-1 were due to the active vibrational optical phonon modes pertaining to B1g, Eg and A1g respectively of the pure tetragonal rutile phase, whereas the peaks at ～ 395, 513 and 639 cm-1 were attributed due the active modes B1g, A1g and Eg respectively of anatase phase of TiO2. The active mode observed at ～ 142 cm-1 was a characteristic mode whereas the mode at ～ 229 cm-1 was attained due to second order effect [SOE] of pure rutile phase of TiO2. The Raman studies validate the PXRD studies. The CIE and CCT outcomes show that NPs can be used for wLED and household applications. The optimized product TiO2:Dy3+(9 mol% ) was utilized for the visualization of latent finger prints (LFPs). The results reveal that, all the levels (I to III) of ridge feature were clearly visualized under normal light indicating that the powder was a reliable and promising labeling agent for LFPs.
关键词： TiO2:Dy3+,latent finger print detection,wLED,solution combustion method,nanophosphors
更新于2025-09-19 17:13:59
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A multi-level optical storage scheme via two-step picosecond laser irradiations: time/space modulations of microstructure and its optical property
摘要： China has a considerable lignite deposit in the Xinjiang province, but surface and underground coal seam fires pose a threat to the resources, environment, economy, and health. As the chemical and physical structure impacts coal fire propensity and behavior, two raw Xinjiang lignites were examined from the Shaerhu (SEH) and Piliqing (PLQ) Collieries. The SEH lignite is more prone to spontaneous combustion (from regional observations). These coals were of the same geological age and were both inertinite-rich 69.8 and 95.6% for SEH and PLQ, respectively (by the point counting approach). The more spontaneous combustion prone lignite had a significantly higher micropore contribution and surface area (92.4% and 195.6 m2/g), while both coals had similar micro- and mesopore size distribution ranges. Despite being classified as lignite by the mean vitrinite random reflectance (Rr, 0.30 and 0.26%) the inertinite contribution displaces some of the structural properties to be similar to the vitrinite-rich, high-volatile bituminous rank. The lignite coals had similar carbon content (74.6 and 78.4 wt % for SEH and PLQ) and vitrinite reflectance but differed in ash, volatile matter, total moisture, and fixed carbon yields. The crystallite parameters [from X-ray diffraction (XRD)], the interlayer spacing, crystallite height, crystallite diameter, and the numbers of aromatic layer indicated the more inertinite-rich coal (PLQ) was slightly less ordered. Both coals were highly aromatic for lignites (fa values of 0.72 and 0.71 for SEH and PLQ), as the inertinite-rich components are more aromatic and polycondensed than huminite-rich (a low rank counterpart of vitrinite) coals of similar reflectance values. Image analysis of high-resolution transmission electron microscopy lattice fringes determined the aromatic fringe length distributions, with contributions between 0.25 and 0.50 nm accounting for 37.1% for PLQ, while SEH had a lower contribution of 28.0% but also a greater contribution of longer fringes (larger polycyclic aromatic hydrocarbon cluster sizes). Image analysis of the lattice fringe orientation and XRD analysis also indicated that the SEH lignite was more ordered. These two coals are potential coals for further exploration of spontaneous combustion behavior for inertinite-rich coals.
关键词： inertinite,lignite,spontaneous combustion,LDIMS,HRTEM,solid-state 13C NMR,XRD
更新于2025-09-19 17:13:59
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Facile synthesis, structure analysis and optical performance of manganese oxide-doped PVA nanocomposite for optoelectronic and optical cut-off laser devices
摘要： In the present work, successful manganese oxide (Mn2O3) nanoparticles (NPs) were synthesized by a combustion technique, while the casting process was employed for the manufacturing of polymer nanocomposites with various weights of Mn2O3 based on Poly(Vinyl Alcohol), PVA. Multiple methods such as X-ray diffraction (XRD), HR-TEM, EDAX, EDS, SEM, FT-IR, DTA analysis, optical spectroscopy from UV to IR regions, and optical reduction (CUT-OFF) setup were used to characterize the structural, elemental chemical analysis, morphological, optical properties, and cut-off laser characteristic of nanocomposite samples. Mn2O3 nanoparticles have a crystallite size of 22.08 nm as calculated using the Debye–Scherer formula from XRD, while the HR-TEM shows a spherical particle of size 30–38 nm range. EDAX spectra and EDS mapping were used to detect the elemental particles of the nanocomposite. The external morphology of the films by SEM images shows an increase in the agglomeration size of the cluster with the percentage of Mn2O3 nanoparticles in PVA. FT-IR spectra show excellent incorporation between the matrix of polymer and the Mn2O3 via the hydroxyl group. Moreover, with increasing the doping rate of nanoparticles, the thermal stability of PVA increased. A significant change of optical transmittance, absorption edge, Urbach energy, and transition bandgap have been observed due to the influence of Mn2O3. The comparison between the bandgap values that have been estimated from Tauc’s relation and thus resulting from optical dielectric loss indicates a direct allowed transition of electrons in the nanocomposites. The light is entirely UV–Vis absorbed by PVA with a high percentage of Mn2O3 nanoparticles. Moreover, the efficiency of the films to decrease the power of two laser beams (635 nm and 533 nm) has been observed. The flexible films of PVA with an elevated rate of Mn2O3 are considered a successful option for low-cost technologies of optical limiting.
关键词： Casting process,Combustion technique,PVA nanocomposite,Optoelectronic,Manganese oxide,Optical cut-off laser devices
更新于2025-09-19 17:13:59
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Investigation of the structural, optical, elastic and electrical properties of spinel LiZn <sub/>2</sub> Fe <sub/>3</sub> O <sub/>8</sub> nanoparticles annealed at two distinct temperatures
摘要： Nanoparticles of Li0.5ZnFe1.5O4 (LiZn2Fe3O8) with the spinel structure were prepared by a sol–gel auto-combustion method at two different annealing temperatures. X-ray diffractograms and Rietveld refinement confirmed the formation of the spinel structure. The morphology was analyzed by electron microscopy, which showed that the grains were composed of different crystallites. Elastic properties were determined from infrared spectroscopy. It was found that the elastic parameters increased with the increase in annealing temperatures. The band gap depends on the annealing temperature and it decreased on increasing the particle size. The conductivity of the specimen annealed at 500 °C followed either the Jonscher's model or Drude's model depending on the temperature range. This conductivity decreased when the annealing temperature was raised by 600 °C. AC conductivity was found to be controlled by the hopping model. A single relaxation phenomenon was evidenced for each sample from impedance analysis. The Nyquist diagram proved that the samples were simultaneously capacitive and resistive and also supported the presence of multiple relaxation times.
关键词： annealing temperature,spinel,conductivity,LiZn2Fe3O8,impedance analysis,band gap,elastic properties,sol–gel auto-combustion
更新于2025-09-16 10:30:52
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Cymbopogoncitratus assisted green synthesis of doped Yttrium nanopowder: Structural and Photoluminescence properties for wLEDs applications
摘要： For the first time green route was used to synthesize pure and Cr3+ (1-11 mol %) doped Yttrium oxide (Y2O3) nanostructures by using Cymbopogon citrates extract as a fuel. The prepared samples were well characterized by powder X-ray diffraction (PXRD), transmission electron microscopy, Diffused reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. The PXRD results shows the formation of single phase, cubic structure of Y2O3 with crystallite sizes ~15 nm which was further confirmed by TEM results. The SEM results indicated various shaped nanostructures which solely dependent on the fuel concentration. The band gap energy was estimated by DRS and found to be in the range of 5.67 – 5.80 eV. PL results indicate intense sharp peak at ~ 689 nm along with vibronic side bands 706 and 734 nm. The 689 nm peak was well known R – line and was assigned to the 2Eg → 4A2g transition of Cr3+ions.The CIE (Commission International de I'E' clairage) chromaticity coordinates were located in pure orange- red region. Further, (Commission International de I'E' clairage) CCT values were in the range 3387 – 3486 K. The studies indicate that Y2O3:Cr3+nanophosphors (NPs) were quite useful for display devices.
关键词： display devices,orange-red emission,Cymbopogon citrates,Green combustion synthesis,Photoluminescence
更新于2025-09-16 10:30:52
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Coupled photothermal and joule-heating process for stable and efficient interfacial evaporation
摘要： A trade-off inevitably exists between soot and NOX emissions in a traditional engine. The addition of an oxygen-containing biofuel can decrease the soot emission but increase the NOX emission. Multi-injection strategy can be used to decrease the NOX emission. Therefore, both simulations and experimental tests were conducted to evaluate the influences of pre-injection on the combustion and emission characteristics of pure diesel (D100) and diesel/n-butanol (30% n-butanol and 70% diesel by volume, B30). The results showed that as the pre-injection interval decreased, the in-cylinder pressure peak increased, the pre-injection heat release ratio increased, and the brake-specific fuel consumption (BSFC) decreased. Only at a small pre-injection interval, the BSFC under pre-injection condition was lower than that obtained using the single injection strategy. When the same pre-injection strategy was used, B30 had a higher BSFC and lower brake thermal efficiency than D100. The soot emission decreased with the increase in pre-injection interval but increased with the increase in pre-injection ratio. More soot was emitted using the pre-injection strategy than that using single injection strategy. B30 had a lower soot emission than D100 due to a longer ignition delay. As the pre-injection interval increased, the decreasing amplitude of NO production became smaller than the increasing amplitude of NO2 production, thus increasing the net NOX emission. As the pre-injection ratio increased, more CO was produced through the reaction paths CH2O → HCO → CO, whereas the transformation of CO to CO2 almost remained unchanged, thus increasing the net CO emission. The increase in pre-injection ratio inhibited the oxidation of CO to CO2 and thus increased the CO emission. The amount of unburned hydrocarbons increased with the increase in both pre-injection ratio and interval.
关键词： Chemical kinetics,CFD,Pre-injection,Diesel/n-butanol blends,Low-temperature combustion
更新于2025-09-16 10:30:52