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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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Digital holographic sizer for coal powder size distribution measurement: preliminary simulation and experiment
摘要： On-line and continuous measurements of coal powder size distribution in coal-fired plants remain challenging. A coal powder size measurement system based on digital holography (DH) is developed. The effects of several factors, i.e. pixel size, recording distance, particle size, and concentration, on particle size measurement by the DH method are quantified by simulation, yielding the suitable pixel size, recording distance and particle concentration. The measurement system is implemented based on the simulation results and applied to measure particle size distribution of pulverized coal samples. Results show that the particles are clearly reconstructed from the hologram, and the measured size distributions agree well with those of the samples measured by laser particle size analyzer. This work shows that the digital holographic sizer has great potential in coal powder size distribution measurement in power plant pipes.
关键词： digital holography,particle size distribution,coal powder,on-line measurement
更新于2025-09-23 15:21:01
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A Comparative Study of Particle Size Distribution of Graphene Nanosheets Synthesized by an Ultrasound-Assisted Method
摘要： Graphene-based materials are highly interesting in virtue of their excellent chemical, physical and mechanical properties that make them extremely useful as privileged materials in different industrial applications. Sonochemical methods allow the production of low-defect graphene materials, which are preferred for certain uses. Graphene nanosheets (GNS) have been prepared by exfoliation of a commercial micrographite (MG) using an ultrasound probe. Both materials were characterized by common techniques such as X-ray diffraction (XRD), Transmission Electronic Microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). All of them revealed the formation of exfoliated graphene nanosheets with similar surface characteristics to the pristine graphite but with a decreased crystallite size and number of layers. An exhaustive study of the particle size distribution was carried out by different analytical techniques such as dynamic light scattering (DLS), nanoparticle tracking analysis (NTA) and asymmetric flow field flow fractionation (AF4). The results provided by these techniques have been compared. NTA and AF4 gave higher resolution than DLS. AF4 has shown to be a precise analytical technique for the separation of GNS of different sizes.
关键词： exfoliation,graphene nanosheets,nanoparticle tracking analysis,asymmetric flow field flow fractionation,particle size distribution
更新于2025-09-19 17:15:36
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Laser-induced incandescence on metal nanoparticles: validity of the Rayleigh approximation
摘要： Time-resolved laser-induced incandescence (TiRe-LII) is increasingly being used to characterize non-carbonaceous nanoparticles. However, there exist several measured phenomena, particularly on metal nanoparticles, that cannot be explained using traditional models. This paper shows that some of these phenomena may be due to errors caused by the Rayleigh approximation of Mie theory, which is a standard approach for modeling the spectral absorption of carbonaceous nanoparticles but is generally invalid for metal nanoparticles. Other measurement phenomena can be explained by combining Mie theory with a polydisperse particle size distribution or by considering the change in the refractive index as the nanoparticles melt. Also, the effect of the nanoparticle charge on optical properties is investigated and is found to have a negligible effect on the TiRe-LII model.
关键词： Mie theory,Polydisperse particle size distribution,Metal nanoparticles,Refractive index,Nanoparticle charge,Rayleigh approximation,Laser-induced incandescence
更新于2025-09-19 17:13:59
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A brief introduction to the selective laser melting of Ti6Al4V powders by supreme-speed plasma rotating electrode process
摘要： In the present study, Ti6Al4V spherical powders were prepared by supreme-speed plasma rotating electrode process and the particle size fit log-normal distribution. The average diameter of the powders was successfully determined by a model developed in this work, suggesting that the particle size distribution is mainly affected by the rotating speed. The log-normal distribution factor of the particle size distribution maintains stable as the rotating speed ω varies. The particle size distribution indicates that the main atomization mode of Ti6Al4V under supreme-speed plasma rotating electrode process is of the characteristics of direct drop formation. The mechanical properties of the samples prepared by selective laser melting of Ti6Al4V powders were characterized, indicating that such Ti6Al4V samples with isotropy structure exhibit high yield strength and good ductility.
关键词： Atomization,Ti6Al4V,Selective laser melting,Rapid solidification,Particle size distribution,Plasma rotating electrode process
更新于2025-09-16 10:30:52
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Influence of particle morphology and size distribution on the powder flowability and laser powder bed fusion manufacturability of Ti-6Al-4V alloy
摘要： Laser powder bed fusion (LPBF) additive manufacturing technology is sensitive to variations in powder particle morphology and size distribution. However, the absence of a clear link between the powder characteristics and the LPBF performances complicates the development, selection and quality control of LPBF powder feedstock. In this work, three Ti-6Al-4V powder lots produced by two different techniques, namely, plasma atomization and gas atomization, were selected and characterized. Following the micro-computed tomography analysis of the powder particles’ morphology, size and density, the flowability of these powder lots was concurrently evaluated using Hall and Gustavsson flowmeters and an FT4 powder rheometer. Using established rheology-based criteria, a figure of merit was proposed to quantify the overall powder suitability for the LPBF process. Next, the same three powder lots were used to 3D-print and post-process a series of testing specimens with different layer thicknesses and build orientations, in order to establish a correlation between the powder characteristics and the geometric and mechanical properties of a final product. This study demonstrates that the use of highly spherical powders with a limited amount of fine particles promotes their flowability and yields LPBF components with improved mechanical and geometric characteristics.
关键词： sphericity,powder flowability,particle size distribution,Laser powder bed fusion,layer thickness,Ti-6Al-4V
更新于2025-09-12 10:27:22
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Effect of powder characteristics on production of oxide dispersion strengthened Fe 14Cr steel by laser powder bed fusion
摘要： In order to assess the potentialities of additive manufacturing in nuclear industry, Oxide Dispersion Strengthened (ODS) Fe\14Cr steels are produced by laser powder bed fusion (L-PBF). Such materials are currently manufactured by milling a Fe\14Cr atomized powder with Y2O3 and TiH2 powders. The resulting powder has a non-spherical shape being coarser than powders typically used in L-PBF equipment. The influence of powder characteristics on the processability of ODS Fe\14Cr by L-PBF are studied in details. Four different powders are used. These powders differ from size, morphology and chemical composition. Finer is the powder; wider is the process range to obtain dense samples. This phenomenon could be mitigated by transferring an amount of energy superior to 110 J.mm?3. The presence of yttrium and titanium gives columnar microstructure for ODS samples, whereas Fe\14Cr samples have stirred microstructure. Titanium and yttrium form oxides, which enlarge the melt pool and induce columnar growth.
关键词： Additive manufacturing,Powder flowability,Metal Matrix Composites (MMCs),Chemical composition,Laser Powder Bed Fusion (L-PBF),Particle size distribution
更新于2025-09-11 14:15:04
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Solar Light Induced Photon-Assisted Synthesis of TiO2 Supported Highly Dispersed Ru Nanoparticle Catalysts
摘要： Ru/TiO2 are promising heterogeneous catalysts in different key-reactions taking place in the catalytic conversion of biomass towards fuel additives, biofuels, or biochemicals. TiO2 supported highly dispersed nanometric-size metallic Ru catalysts were prepared at room temperature via a solar light induced photon-assisted one-step synthesis in liquid phase, far smaller Ru nanoparticles with sharper size distribution being synthesized when compared to the catalysts that were prepared by impregnation with thermal reduction in hydrogen. The underlying strategy is based on the redox photoactivity of the TiO2 semi-conductor support under solar light for allowing the reduction of metal ions pre-adsorbed at the host surface by photogenerated electrons from the conduction band of the semi-conductor in order to get a ?ne control in terms of size distribution and dispersion, with no need of chemical reductant, ?nal thermal treatment, or external hydrogen. Whether acetylacetonate or chloride was used as precursor, 0.6 nm sub-nanometric metallic Ru particles were synthesized on TiO2 with a sharp size distribution at a low loading of 0.5 wt.%. Using the chloride precursor was necessary for preparing Ru/TiO2 catalysts with a 0.8 nm sub-nanometric mean particle size at 5 wt.% loading, achieved in basic conditions for bene?tting from the enhanced adsorption between the positively-charged chloro-complexes and the negatively-charged TiO2 surface. Remarkably, within the 0.5–5 wt.% range, the Ru content had only a slight in?uence on the sub-nanometric particle size distribution, thanks to the implementation of suitable photo-assisted synthesis conditions. We demonstrated further that a ?ne control of the metal Ru nanoparticle size on the TiO2 support was possible via a controlled nanocluster growth under irradiation, while the nanoparticles revealed a good resistance to thermal sintering.
关键词： highly dispersed Ru nanoparticle,sub-nanometric particle size distribution,catalyst preparation,reaction mechanism,Ru/TiO2 catalyst,photodeposition,photon-assisted synthesis
更新于2025-09-10 09:29:36
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Estimation of the particle size distribution of colloids from multiangle dynamic light scattering measurements with particle swarm optimization
摘要： In this paper particle Swarm Optimization (PSO) algorithms are applied to estimate the particle size distribution (PSD) of a colloidal system from the average PSD diameters, which are measured by multi-angle dynamic light scattering. The system is considered a nonlinear inverse problem, and for this reason the estimation procedure requires a Tikhonov regularization method. The inverse problem is solved through several PSO strategies. The evaluated PSOs are tested through three simulated examples corresponding to polystyrene (PS) latexes with different PSDs, and two experimental examples obtained by simply mixing 2 PS standards. In general, the evaluation results of the PSOs are excellent; and particularly, the PSO with the Trelea’s parameter set shows a better performance than other implemented PSOs.
关键词： inverse problem,particle swarm optimization algorithm,particle size distribution,Swarm Intelligence,dynamic light scattering
更新于2025-09-09 09:28:46