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Adjustable Optical Transmittance of Superhydrophobic Carbon Soot Coatings by in-situ Single-step Control of their Physicochemical Profile
摘要： Soot aerosol formation in the ambient atmosphere, due to inappropriate and incomplete incineration of various fossil fuels or waste materials, has been considered as one of the major anthropogenic contributions to the global warming. However, despite of their adverse environmental impact, the soot nanoparticles are extremely useful in many practical applications if deposited as coatings, since they impart superhydrophobicity of the hosting solid substrate. Here, we unveil novel experimental results on the optical transmittance of superhydrophobic soot coatings with three different physicochemical profiles, synthesized by controlling the atmospheric air flow rate during the combustion of rapeseed oil. The in-depth morphological, chemical and optical analyses using scanning electron microscopy, X-ray photoelectron spectroscopy and spectrophotometry, show relation among the thickness, chemical bonds, morphology and light transmission coefficient (T %) of the soot. In turn, at equal film thicknesses, the gradual decrease of π bonds in the material leads to enhanced light transmittance in the NIR range, while the soot morphology regulates the width of the spectral region with T ?0 %. Our findings demonstrate interconnection between the combustion conditions and the derivative physicochemical properties of the soot coatings, allowing single-step adjustment of their optical behavior, possibly for future underwater optical applications.
关键词： soot,light transmission,physicochemical properties,superhydrophobicity
更新于2025-11-14 15:25:21
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In-flame soot quantification of diesel sprays under sooting/non-sooting critical conditions in an optical engine
摘要： Because of the challenge of meeting stringent emissions regulations for internal combustion engines, some advanced low temperature combustion modes have been raised in recent decades to improve combustion efficiency. Therefore, detailed understanding and capability for accurate prediction of in-flame soot processes under such low sooting conditions are becoming necessary. Nowadays, a lot of investigations have been carried out to quantify in-flame soot in Diesel sprays under high sooting conditions by means of different optical techniques. However, no information of soot quantification can be found for sooting/non-sooting critical conditions. In current study, the instantaneous soot production in a two-stroke optical engine under low sooting conditions has been measured by means of a Diffused back-illumination extinction technique (DBI) and two-color method (2C) simultaneously. The fuels used were n-dodecane and n-heptane, which have been injected separately though two different injectors equipped with single-hole nozzles. A large cycle-to-cycle variation on soot production can be observed under such operating conditions, however the in-cylinder heat release traces were quite repeatable. It is the same with the well-known trends of soot amount to operating conditions that the probability of sooting cycles increases with higher ambient temperature, higher ambient density and lower injection pressure. Both techniques present a pretty good agreement on soot amount when the peak of KL value is close to 1. However, the KL value of two-color method becomes bigger than that of DBI and the difference increases with lower sooting conditions.
关键词： 2C,Soot critical conditions,DBI,Diesel sprays,Optical engine
更新于2025-09-23 15:23:52
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A novel approach for in-situ soot size distribution measurement based on spectrally resolved light scattering
摘要： The present study demonstrates the exploitation of the spectral elastic light scattering technique. Additional information provided by the spectral response of the light scattering signals enables the measurement of the soot size distribution with only two scattering angles. It also provides quantitative data on the spectral dependence of the soot optical index, which is related to the soot chemical composition. The measurement principle consists in dividing the scattered spectra collected at two scattering angles and processing this ratio using the Rayleigh–Debye–Gans theory for Fractal Aggregates (RDG-FA). It is shown that the median diameter of gyration and geometric standard deviation of a lognormal soot size distribution can be determined without any prior information on key parameters such as the fractal prefactor, particle primary diameter, aggregate number density and soot optical properties. A proof of concept was performed on soot particles produced by a miniCAST generator by comparing the optical results with the soot size distributions measured by SMPS. A statistical Bayesian inversion approach was used to determine posterior distributions with a particular emphasis on their uncertainty quantification.
关键词： Light scattering,Bayesian,Spectral scattering,Optical properties,Soot,Size distribution
更新于2025-09-23 15:23:52
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Evolution of volatile cloud in pulverized coal combustion with high-speed digital inline holographic visualization
摘要： The coal devolatilization plays a significant role in the combustion of pulverized coal particles. The evolution of volatile cloud during devolatilization of pulverized coal particles (105–125 μm) is studied in a high-temperature flat-flame burner by combining high-speed photography with high-speed digital inline holography (DIH). By the high-speed holographic visualization, the evolution of volatile cloud of pulverized coal from volatile release to soot aggregation generation can be divided into four stages. Effects of coal type on volatile cloud evolution are investigated using three different coals, i.e., Shanxi bituminous coal, Ximeng lignite and Yinni lignite. The results show that both the Shanxi bituminous coal and Ximeng lignite produce soot aggregation during devolatilization, which is rarely observed for Yinni lignite. Moreover, Shanxi bituminous coal has a higher potential in soot cluster formation for its higher coal rank than Ximeng lignite. The high-speed reconstructed image sequences are analyzed to measure the velocity slip between the parent particle and volatile cloud. Compared with Shanxi bituminous coal, Ximeng lignite exhibits a larger slip velocity. This work also demonstrates that high-speed DIH has the powerful capacity of directly observing the evolution of volatile cloud, and helps to gain a deep understanding of pulverized coal combustion.
关键词： Volatile cloud,Coal combustion,High-speed digital inline holography,Soot aggregation,High-speed photography
更新于2025-09-23 15:22:29
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Fuel Waste to Fluorescent Carbon Dots and Its Multifarious Applications
摘要： Herein, we report the fluorescent carbon dots (KCDs) from kerosene fuel soot via simple one pot oxidative acid treatment. The obtained KCDs were thoroughly characterized by pivotal techniques. The prepared KCDs are 5 nm sized quasi-spherical particles and exhibited an outstanding stability against pH, NaCl and light irradiation. Intriguingly, the KCDs display an excitation wavelength independent emissive property. Further, the KCDs were successfully utilized for multifarious applications such as photoinduced electron transfer (PET) and sensing studies. For PET studies, charged porphyrins (tetra pyridyl and tetra sulphonato) were selected and the fluorescence of associated porphyrin was quenched and the quenching is due electron transfer. The lower recombination rate obtained from transient absorption spectral studies suggests that KCDs can be used as electron shuttling material in a cascade system of photovoltaic device. On the other hand, the fluorescent nature of KCDs was used for the selective and sensitive detection of explosives and metal ions. The detection limit for picric acid, Cu2+ and Fe3+ is found to be 86 ng/ml, 15.3 ng/ml and 0.36 μg/ml respectively. Moreover, the unreacted soot during the acid treatment has been calcined and used as an affordable filter bed for waste water treatment.
关键词： Explosives,PET,Kerosene Soot,Carbon dots,Metal ion detection
更新于2025-09-23 15:21:21
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A forward approach for the validation of soot sizing??models using laser-induced incandescence (LII)
摘要： While validating the numerical modeling of the primary particle size distribution (PPSD) in sooting flames, a common practice is to compare the numerical results to the corresponding experimental data obtained with the Time-Resolved Laser-Induced Incandescence (TiRe-LII) technique. Since the PPSD is not directly measured by TiRe-LII, but derived with a post-processing procedure, various uncertainties and errors can potentially affect the consistency of such comparison requiring the estimation of many input parameters. On the contrary, nowadays, detailed numerical simulations provide access to a more complete set of data, which can be used to reconstruct the incandescence signal. In this work, a forward approach for the generic validation of numerical models for the PPSD is performed. It is based on the numerical reconstruction of the temporal evolution of the incandescence from the numerical results and its comparison with the measured signal. First, two indexes are proposed to quantify the agreement between the numerically synthesized and the measured signals. Then, the effectiveness of the proposed approach is demonstrated a priori by quantifying the potential errors that can be avoided with this new strategy compared to the classical approach. Finally, the feasibility of the proposed procedure is proven by comparing synthesized signals to the experimental ones available in the literature for a laminar premixed flame. It is shown that the proposed approach can be used for strengthening the analysis on numerical model performances in addition to the classical approach.
关键词： validation,soot sizing models,numerical modeling,primary particle size distribution,laser-induced incandescence
更新于2025-09-23 15:21:01
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Nanosecond laser irradiation of soot particles: insights on structure and optical properties
摘要： In spite of the advances in laser diagnostics in combustion, the effect of rapid laser irradiation on the physical/chemical properties of soot particles is far from being comprehensively understood. Optical properties, particle nanostructure and aggregate size of laser-irradiated soot particles are analyzed in this paper. Carbonaceous particles sampled from nitrogen-quenched diffusion flames of ethylene and methane are irradiated on-line by a 1064-nm short laser pulse. Wavelength-resolved extinction measurements in the visible range are used to follow their transformation by varying the laser energy density. A variation of the extinction coefficient of the irradiated particles compared to the extinction coefficient of the pristine ones is observed, especially for ethylene soot. The particle nanostructures are analyzed by Raman spectroscopy and the effect of laser irradiation on aggregate structure is evaluated by measuring particle size distributions. The results indicate that both soot nanostructure and optical properties are strongly dependent on the laser energy density when irradiated by a laser source. This is significant for ethylene soot, while for methane soot the degree of variation of such properties is less pronounced, at least in the investigated heating conditions.
关键词： Raman spectroscopy,optical properties,laser-heating,Soot,nanostructure,LII
更新于2025-09-19 17:13:59
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Predicting the photoresponse of soot nuclei: Spectroscopic characteristics of aromatic aggregates containing five-membered rings
摘要： Establishing the mechanism for soot nucleation will require in situ experimental characterization of the identity and intermolecular interactions of the initial precursors, and electronic spectroscopy methods have the potential to do both. However, the optical response of polycyclic aromatic hydrocarbon (PAH) dimers and complexes differs significantly from that of the constituent monomers, and studies of soot precursor complexes have largely been limited to PAHs containing only six-membered aromatic rings. Hydrocarbons containing unsaturated five-membered rings are also present in high concentration in flames, and the photoresponse of complexes containing five-membered rings has not yet been examined. In this work, we elucidate the spectroscopic properties of small hydrocarbon complexes containing cyclopentadienyl groups or cyclopenta-fused groups, calculating ground- and excited-state binding energies, optimal excited-state geometries, repulsion energies, and fluorescence emission wavelengths. We show that excited-state distortion of cyclopentadienyl groups allows strong binding and low-energy fluorescence emission compared to similar-sized PAHs, and that a cyclopenta-fused group dramatically lowers the absorption and emission energies for acenaphthylene, dominating excited-state noncovalent interactions—findings that could shed light on the complex electronic properties of flames.
关键词： Particle inception,LIF,Soot nucleation,Cyclopentadiene,Acenaphthylene,PAH
更新于2025-09-19 17:13:59
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Cost-efficient solar cells using nanocrystalline perovskite La (Fe and Mn) O3 and candle soot: Theory and experiment
摘要： In present investigation, co-precipitation as a simple, low temperature synthesis and low cost route was used to prepare nanocrystal perovskite La (Fe and Mn) O3 for solar cell application. The synthesized powders were characterized by XRD, SEM, PL, DRS, CV, EDS, and FTIR analysis. The photovoltaic behavior of prepared La (Fe and Mn) O3 perovskite as photo anode was also investigated, experimentally and theoretically. The best power conversion efficiency was experimentally obtained by LaFeO3 perovskite (0.07). Two different counter electrodes were applied: Pt electrode and an electrode prepared from a candle soot coated on the surface of FTO glass as a remarkable alternative material and process of noble metal electrode (Au or Ag) deposited by complicated vacuum technologies. In another stage, commercial electrolyte was used to enhance efficiency. These results indicate that there is a possibility to further increase the performance and efficiency of perovskite based cells.
关键词： Candle soot,Solar cell,Perovskite,Co-precipitation
更新于2025-09-11 14:15:04
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The Self-Reaction of <i>ortho</i> -Benzyne at High Temperatures Investigated by Infrared and Photoelectron Spectroscopy
摘要： Ortho-benzyne, a Kekulé-type biradical is considered to be a key intermediate in the formation of polycyclic aromatic hydrocarbons (PAH) and soot. In the present work we study the ortho-benzyne self-reactions in a hot micro-reactor and identify the high-temperature products by IR/UV spectroscopy and by photoion mass-selected threshold photoelectron spectroscopy (ms-TPES) in a free jet. Ms-TPES confirms formation of ortho-benzyne as generated from benzocyclobutendione, as well as benzene, biphenylene, diacetylene and acetylene, originating from the reaction o-C6H4 → HCC-CCH + C2H2 , and CH3. PAH molecules like naphthalene, 2-ethynylnaphthalene, fluorene, phenanthrene and triphenylene are identified based on their IR/UV spectra. By comparison with recent computations their formation starting from ortho-benzyne can be readily understood and supports the importance of the biradical addition (1,4-cycloaddition followed by fargmenation) pathway to PAH molecules, recently proposed by Comandini et al.
关键词： photoelectron spectroscopy,Ortho-benzyne,high-temperature reactions,IR/UV spectroscopy,biradical addition,polycyclic aromatic hydrocarbons,PAH,soot
更新于2025-09-10 09:29:36