Particle Size Distribution Characteristics Research Articles

Preparation and characterization of monodispersed spherical Fe2O3@SiO2 reddish pigments with core\u2013shell structure

The α-Fe2O3@SiO2 reddish pigments with core–shell structure were successfully prepared by hydrothermal and Stöber methods. The structure, morphology, and chromaticity of the synthesized pigments were characterized by XRD, SEM, TEM, FTIR, XPS, and colorimetry. The results indicated that the as-prepared pigments have the characteristics of narrow particle size distribution, high dispersion, and good sphericity. The α-Fe2O3@SiO2 reddish pigments were uniform and well dispersed in solution. In addition, the pigments with different shell thickness were also prepared, and the effect of shell thickness on the color performance of the pigments was discussed.

대구지역 도로변 미세먼지 입경분포 특성

대구지역 도로변 미세먼지 입경분포 특성

Characterizing the spatial variability of soil particle size distribution in an underground coal mining area: An approach combining multi-fractal theory and geostatistics

Long-term underground coal mining activities results in severe surface deformation and land subsidence, altering soil physical properties significantly. Soil particle size distribution (PSD) is a fundamental physical attribute affecting many other soil properties. Therefore, understanding the variability of PSD is crucial to conduct targeted land rehabilitation. In present study, a novel method combining multi-fractal theory and geostatistics was advanced to characterize the spatial variability of soil PSD in a coal-mined subsidence area. Three independent field plots, i.e., one unmined plot (UMP), one subsided plots (SUP), and one reclaimed plot (RCP), in NO.3 Pingshuo Anjialing underground coal-mine in Shanxi province of China, were selected to perform this study. Four multi-fractal attributes of PSD of individual soil samples, i.e., D(0), D(1), Δα(q) and Δf(α), in three plots were calculated, and geo-statistics was employed to quantify the spatial variability of multi-fractal attributes of PSD. This combining method showed some advantages in characterizing the variability of soil PSD compared to single multi-fractal, single geo-statistics or traditional statistics, and it can characterize the spatial variability of overall PSD characteristics in detail, quantifying the spatial variability of soil PSD range, PSD concentration degree, PSD non-uniformity, and PSD non-symmetry. The soil PSD range, PSD concentration degree, PSD non-uniformity and PSD non-symmetry in this underground coal mining area didn't present a high spatial variability. Combining multi-fractal theory and geostatistics is an effective method to characterize the spatial variability of soil PSD in underground coal-mine area, and this method is universal and can be popularized and applied in other unmined areas.

1P4-6 Characteristics of particle size distribution of agglomerates in an ultrasonic source with a cylindrical rigid wall

1P4-6 Characteristics of particle size distribution of agglomerates in an ultrasonic source with a cylindrical rigid wall

CUPROUS OXIDE NANOPARTICLES: PREPARATION AND EVALUATION OF ANTIFOULING ACTIVITY

There are few methods to obtain uniform and well dispersed cuprous oxide nanoparticles, which limits its application widely. In this research, an improved method to prepare nanoparticles was introduced. Cuprous oxides were prepared by the reduction of cupric nitrate, with hydrazine hydrate as a reductant in the presence of glucose. The nanoparticles formed have the characteristics of small particle size and uniform distribution. The crystalline structure and morphological characteristics were analyzed by XRD and TEM respectively. The result showed they were pure sphere polycrystal. The particle size is about 9nm. Subsequently, the antifouling activity was tested in detail through comparative experiments. The results indicated that the effective concentration of nanoparticles was obviously lower than ordinary cuprous oxide.

Mobile Measurements of Particulate Matter in a Car Cabin: Local Variations, Contrasting Data from Mobile versus Stationary Measurements and the Effect of an Opened versus a Closed Window.

Air pollution of particulate matter (PM) from traffic emissions has a significant impact on human health. Risk assessments for different traffic participants are often performed on the basis of data from local air quality monitoring stations. Numerous studies demonstrated the limitation of this approach. To assess the risk of PM exposure to a car driver more realistically, we measure the exposure to PM in a car cabin with a mobile aerosol spectrometer in Frankfurt am Main under different settings (local variations, opened versus a closed window) and compare it with data from stationary measurement. A video camera monitored the surroundings for potential PM source detection. In-cabin concentrations peaked at 508 µg m−3 for PM10, 133.9 µg m−3 for PM2.5, and 401.3 µg m−3 for coarse particles, and strongly depended on PM size and PM concentration in ambient air. The concentration of smaller particles showed low fluctuations, but the concentration of coarse particles showed high fluctuations with maximum values on busy roads. Several of these concentration peaks were assigned to the corresponding sources with characteristic particle size distribution profiles. The closure of the car window reduced the exposure to PM, and in particular to coarse particles. The mobile measured PM values differed significantly from stationary PM measures, although good correlations were computed for finer particles. Mobile rather than stationary measurements are essential to assess the risk of PM exposure for car passengers.

An Experimental Study of Mineral and Microstructure for Undisturbed Loess Polluted by Landfill Leachate

To investigate the shear strength and microstructure of undisturbed loess polluted by landfill leachate, a series of laboratory tests were carried out to determine the shear strength, mineral composition, surface morphology, particle size distribution and pore characteristics of the loess. The stress-strain curve of undisturbed soil polluted by landfill leachate showed typical strain-softening behavior. The deviatoric stress, cohesion and angle of shearing resistance of undisturbed soil decreased at increased landfill leachate concentrations, decreased by 31.03%, 30.01%, respectively. But pore water pressure was positively related to leachate concentrations. The content of primary minerals remained stable, and the content of montmorillonite and illite decreased with increased leachate concentration, reduced by 26.02%, 23.93%, respectively. Soil structure changed into an unstable honeycomb structure when the leachate concentration increased. Moreover, the average particle size decreased by 62.1%, and the specific surface area increased and then stabilized at 500 ~ 650 m2/kg. The soil particles became nonuniform and porous and their sizes gradually decreased. The pore radius of soil mainly ranged from 0.02 μm to 1 μm. The maximum radius and optimal radius of the pore increased when the leachate concentrations increased.

Effect of methane addition to ethylene on the morphology and size distribution of soot in a laminar co-flow diffusion flame

The characteristics of soot in the diffusion flames of methane and ethylene under different oxygen concentrations and the influence of mixing methane in ethylene on soot generation were investigated using thermophoretic sampling and subsequent transmission electron microscopy image analysis. The process of soot particle nucleation, surface growth, coagulation, agglomeration and oxidation along the flame axis was analyzed. The variation of soot particle size distribution and aggregate characteristics at different heights along the centerline of the flame at different oxygen concentrations and methane doping ratios were obtained. Results show that the various stages of soot generation in methane flame obviously lags behind the ethylene flame at different oxygen concentrations, and increasing the oxygen concentration makes the various stages of soot formation in the flame advance. A 10% methane doping can promote soot generation at low flame locations. Increasing the doping amount to 30%, the generation of soot can be promoted at high flame locations. The synergistic effect of soot formation in fuel combustion occurs in the above two cases. However, the synergistic effect of the fuel will disappear under high blending ratio conditions. The effect of methane-ethylene at high blend ratios is more like a neutralization effect.

Experimental investigation on the microprocess of hydrate particle agglomeration using a high-speed camera

To investigate the microprocess of hydrate particle agglomeration, a high-pressure visual cell was used for repeated experiments of hydrate particle formation and flow from methane + water systems at an experimental temperature of 275.15 K, an initial pressure of 6 MPa and a rotation rate of 200 rpm. During the experiments, a high-speed camera was used to capture the micromorphologies and micro flow behavior of hydrate particles. Based on the experimental data obtained by the high-speed camera, three types of micromorphologies were identified for hydrate particles. Then, the variation in the average diameter of hydrate particles and the characteristics of hydrate particle size distribution were investigated by calculating the equivalent projection area diameter of hydrate particles. During the experiments, particle collision, particle agglomeration and particle breakage were the three main micro flow behaviors of hydrate particles captured by the high-speed camera. The whole process of hydrate agglomeration under flow conditions was also captured by the high-speed camera. Finally, according to the variation in the average diameter of hydrate particles and the micro flow behavior of hydrate particles, a physical model for the whole process of hydrate particle “agglomeration” was established.

The Influence of Milling Regimes in Beater Mill on Particle Size Distribution and Structural Characteristics of Strontium Hexaferrite Powder

The paper experimentally substantiates effectiveness of method of milling particulate ferromagnetic materials in magneto fluidized bed. Comparative results of particle size distributions and structural parameters of strontium hexaferrite SrFe12O19 powder obtained by milling coarse material in beater mill without electromagnetic effect and in same mill with formation of magneto fluidized bed from mill material are presented. The magneto fluidized bed is formed by constant and alternating gradient magnetic fields with induction lines that are mutually perpendicular and parallel to the plane of rotating beaters. It is shown that application of electromagnetic effect to milling coarse material in beater mill allowed to greatly intensify that process, significantly increase powder quality: increase particle size distribution uniformity and decrease average particle size from 1558.50 μm to 0.56 μm after 120 minutes of processing in the mill. X-ray diffraction analysis showed that milling in beater mill in magneto fluidized bed leads to reduction of coherent-scattering region size, increase of lattice microstrain and dislocation density, making powder more active during sintering process.

Size Distribution of Contamination Particulate on Porcelain Insulators

The characteristics of contamination on the insulation medium surface play an important role in the surface flashover, especially size distribution of contaminated particles. After measuring the size of contaminated particles on the porcelain insulator surface, obvious size distribution characteristics of particles were found. To study the reason for these statistical characteristics, the movement of particles was analyzed in detail combining with fluid mechanics and collision dynamics. Furthermore, an adhesion model was established in this paper. In addition, the influences of different factors on the adhesion were studied. The results showed that the size of adhered particles on the porcelain insulator surface was easy to focus on a specific range, and the influences of relative humidity and wind speed were remarkable. However, the influences of electric field type, electric field strength, and aerodynamic shape were relatively weak. This research was significant and valuable to the study of artificial contamination simulation experiments, and the influence of particles size distribution on pollution flashover.

Heavy Metal Pollution Characteristics in the Modern Sedimentary Environment of Northern Jiaozhou Bay, China.

The particle size distribution characteristics of sediments and the concentrations of heavy metals in Jiaozhou Bay were investigated in this study. The average concentrations of Cu, Pb, Zn, Cr, Cd, Hg and As were 36.88, 29.60, 82.08, 77.48, 0.083, 0.048 and 11.00mg/kg, respectively. The heavy metal concentrations were highest in the eastern sediments, followed by those at the top of the bay, and the lowest concentrations were observed in the central region. Overall, a decreasing trend from the center of the bay to the periphery was observed. Additionally, the distribution of heavy metals in sediments was not completely controlled by sediment particle size. The degree of heavy metal contamination was evaluated using the geoaccumulation index and Hakanson's method. The results revealed that the level of heavy metal pollution in the sediments was relatively low and that the main pollution elements were Cu and Hg. In addition, the sediments are associated with various levels of potential ecological risk due to the high pollution levels of Hg and Cd.

Correlation of nanoparticle size distribution features to spatiotemporal flame luminosity in gasoline direct injection engines

Particle size distribution measured by mobility instruments is a common diagnostic used to characterize ultrafine and nanoparticle emissions in engine exhaust; however, some features of particle size distribution data are poorly correlated to in-cylinder combustion phenomena. In this work, in-cylinder spatiotemporal flame luminosity is quantitatively correlated to features in the solid particle size distribution measured in the exhaust of a gasoline direct injection engine operating in lean and stoichiometric combustion modes. A multi-channel optical sensor was used to measure diffusion flame light intensity in different areas of the combustion chamber. Total solid particle number and particle size distribution in the exhaust were measured using a scanning mobility particle sizer after a catalytic stripper that removed semi-volatile compounds. Results of the experiments showed that different flame phenomenon resulted in distinct particle size distribution characteristics. A large accumulation mode (particles with diameter of 50–100 nm) in the particle size distribution from stoichiometric engine operation with early injection resulted from anomalous diffusion flames like piston-top pool fires. In lean operation incorporating a secondary fuel injection, particle emissions were dominated by flame propagation through fuel-rich regions of the combustion chamber resulting in a comparatively broad particle size distribution. More generally, this work illustrates how particle size distribution data can be more accurately used to diagnose soot formation in gasoline direct injection engines.

The upgrading of rare earth oxides from iron-oxide silicate rich tailings: Flotation performance using sodium oleate and hydroxamic acid as collectors

To investigate the recovery of rare earth elements (REE) as a by-product from iron-oxide silicate rich tailings generated from the extraction of other primary commodities, bench scale flotation tests, in rougher-scavenger-cleaner configuration were studied. Preliminary mineralogical characterisation identified bastnäsite, monazite, stetindite, brannerite, florencite, and stillwellite as the REE minerals, with hematite and quartz being the major gangue minerals in the tailings material. The flotation response of the rare earth oxides (REO) and major gangue phases was investigated using sodium oleate and hydroxamic acid as collectors; and sodium silicate and starch as depressants. Generally, sodium oleate displayed relatively better selectivity for REO than hydroxamic acid in the presence of the depressants. The rougher-scavenger-cleaner flotation configuration using sodium oleate and the depressants produced a final concentrate recovering 63% REO at a grade of 2.25%. This investigation shows that both collectors may be used for REO recovery but the use of depressants is key, in tandem with cleaning of the rougher and scavenger concentrates. The pulp pH also had a strong impact on the flotation recovery of REO, with the selectivity deteriorating with increasing collector dosage. Furthermore, the high proportion of gangue minerals reporting to the concentrates, even with the use of depressants, affected the quality of concentrates grade. This study has shown that particle size distribution and mineralogical characteristics of feed significantly affect the upgrade and recovery of REO.

Results of the Study of Aerosol Characteristics in the Atmosphere of the Kara and Barents Seas in Summer and Autumn 2016

Measurement results of a complex of aerosol microphysical, chemical, and optical parameters in two cruises of the Akademik Mstislav Keldysh research vessel in 2016 are analyzed. The work was carried out in the Kara Sea from July 10 till August 20 and in the Barents Sea from August 25 till October 10. The mean values of the following aerosol characteristics are given: AOD of the atmosphere, fine and coarse components of AOD, number concentration of particles in the near-water air layer, mass concentrations of the absorbing matter (soot), water-soluble ions (Na+, Mg2+, Cl–, K+, Ca2+, $$\rm{NH}_4^+, \rm{NO}_3^-, \rm{SO}_4^{2-}$$ ), and gaseous admixtures (SO2, HCl, HNO3, and NH3). The characteristic particle size distribution functions are presented for different regions of the Kara and Barents Seas. It is shown that the levels of both aerosol turbidity of the atmospheric column (AOD) and the aerosol and soot concentrations in the near-water air layer were close to the long-term mean values in Arctic latitudes. The atmospheric turbidity during the period of measurements was noticeably affected by emissions of continental forest fire smokes. The contribution of smoke aerosol to, e.g., the mean shipborne-measured AOD at λ = 0.5 μm is about 44%.

Particle Size Distribution Equivalency as Novel Predictors for Bioequivalence.

The use of particle size distribution (PSD) similarity metrics and the development and incorporation of drug release predictions based on PSD properties into PBPK models for various drug administration routes may provide a holistic approach for evaluating the effect of PSD differences on in vitro drug release and bioavailability of disperse systems. The objectives of this study were to provide a rational approach for evaluating the utility of in vitro PSD comparators for predicting bioequivalence for subcutaneously administered test and reference drug emulsions. Two types of in vitro comparators for test and reference emulsion products were evaluated: PSD characterization comparators (overlap metrics, median, and span ratios) and release profile comparators (f2 and various fractional time ratios). A subcutaneous-input PBPK disposition model was developed to simulate blood concentration-time profiles of reference and test emulsion products and pharmacokinetic responses (e.g., AUC, Cmax, and Tmax) were used to determine bioequivalence. A pool of 10,440 pairs of test and reference products was simulated using Monte Carlo experiments. The PSD and release profile comparators were correlated to pass/fail bioequivalence metrics using logistical regression. Based on the use of single in vitro comparators, the f2 method was the best predictor of bioequivalence prediction. The use of combinations of f2 and PSD overlap comparators (e.g., OVL or PROB) improved bioequivalence prediction to about 90%. Simulation procedures used in this study demonstrated a process for developing reliable in vitro BE predictors.

In situ generation of zero valent iron for enhanced hydroxyl radical oxidation in an electrooxidation system for sewage sludge dewatering

A hybrid electrochemical conditioning strategy for enhanced sewage sludge dewatering was proposed. A water content of 47.2 wt.% for the dewatered sludge cake was achieved at an applied voltage of 20 V for 30 min, which was significantly lower than previously reported results. The capillary suction time (CST) and specific resistance to filtration (SRF) were decreased by 75.6% and 90.9%, respectively. Four simultaneous processes, including electrooxidation, the electro-Fenton process, molecular oxygen activation via zero valent iron (ZVI) and Fe(III) flocculation, had synergetic effects on the degradation of extracellular polymeric substances (EPS) to enhance sludge dewaterability. The in situ generation of ZVI on the cathode electrode facilitated the reduction of Fe(III) to Fe(II) via activation of molecular oxygen. The sludge pH decreased spontaneously and remained acidic due to the competitive reaction of ZVI generation to hydrogen evolution as well as the Fe(III) flocculation process, which further guaranteed the high efficiency of hydroxyl radical generation. Changes in the physiochemical properties of the sludge (particle size distribution, zeta potential, viscosity and EPS characteristics) induced by the hybrid conditioning process were further explored. In addition, the economic potential of the hybrid system was preliminarily assessed (USD$ 127.6/ton dry sludge).

Effects of fast-desorbed gas on the propagation characteristics of outburst shock waves and gas flows in underground roadways

Abstract Coal and gas outbursts are the most serious disaster in the underground mining. During an intense outburst, ejection of millions tons of coal and cubic meters of gas with high kinetic energy can cause death or injuries and even destroy underground facilities, the intensity of outburst shock waves and gas flows is highly related to the gas expansion energy, and the gas expansion energy requires the participation of a large amount of desorption gas. There is a significant difference in the gas desorption law between the pulverized coal and the unaffected coal. To investigate the effects of fast-desorbed gas on the propagation characteristics of outburst shock waves and gas flows, the particle size distribution characteristics of pulverized coal were obtained by site investigation. Then, gas desorption experiments were conducted for coal particles of various sizes at different gas pressures and temperatures. The results indicate that a segmentation function is reasonable for representing the gas desorption law during coal and gas outbursts. Based on the gas desorption law, numerical simulation for the propagation characteristics of outburst gas flows were conducted. The results show that fast-released gas compresses the air within the roadway, thereby generating outburst shock waves that propagate at high speed. The intensity of the outburst shock waves decrease with time. Simultaneously, the gas convective transport velocity is lower than that of the outburst shock waves, large areas of high-concentration gas in roadways are induced by the outburst gas flows.

Soil particle size distribution characteristics of different land-use types in the Funiu mountainous region

Soil particle composition is one of the main physical properties of soil that affects soil fertility, and the fractal dimension of soil particle size distribution (PSD) can be used to quantitatively evaluate the particle composition of different soils. The single fractal dimension of soil PSD can quantitatively characterize the roughness of the soil particle, and the multifractal dimension of soil PSD can quantitatively characterize the inhomogeneous property of soil particle composition. Sloping farmland is widely distributed in hilly areas of China that are subject to the most serious soil erosion, and the loss of soil will lead to changes in soil particle composition and soil physical properties. Previous studies have not been used to evaluate the heterogeneity of soil PSD between sloping farmland and other land use types by the multifractal method. In order to quantitatively assess the differences in soil properties between the slope land and other types of land use, this paper takes four types of land use (sloping farmland, shrub-grass sloping land, terraced farmland, and oak forestland) in the warm-temperate granite mountainous areas in eastern central China as research objects. A laser particle size analyzer and soil fractal model were applied to compare the soil PSD of different land-use types and their corresponding single fractal dimension (Dv) and generalized fractal dimension (Dq). The results showed that there were clear differences between the DV and Dq of soil PSD in different land-use types. The Dv of the soil PSD increased as follows: sloping farmland < level terraced land < shrub-grass sloping land < oak forestland, indicating that the soil particle composition coarseness was highest in sloping farmland and lowest in the oak forestland. The sequence of characteristic parameters of Dq (capacity dimension, D0; information dimension, D1; and correlation dimension D2) was as follows: sloping farmland < level terraced land < shrub-grass sloping land < oak forestland, indicating that the inhomogeneity of soil particle composition was the highest in sloping farmland, and lowest in oak forestland. The Dv, D0, D1, and D2 of the soil PSD were significantly positively correlated to the content of clay and silt particles, and were significantly and negatively correlated to the content of sand particles, indicating that the fewer clay particles and silt in the soil or the higher the proportion of sand, the higher the coarseness and the inhomogeneity of soil particle composition. This study showed that the soil coarseness and the inhomogeneity of the sloping farmland soil particle composition are significantly greater than those of other land-use types. The mass loss of the soil fine particles (clay and silt particles) is an important cause of coarsening and increased inhomogeneity of the sloping farmland. This study provides a soil fractal index for quantitative assessment of soil texture and the degradation of soil properties in landscapes prone to soil erosion such as sloping farmland.

Process modeling of the electrode calendering of lithium-ion batteries regarding variation of cathode active materials and mass loadings

Abstract The process chain for production of lithium-ion battery electrodes commonly includes the compaction by calendering. This process step decisively determines the pore structure of the coating and therefore the electrochemical performance of the produced lithium-ion battery cells. For the targeted adjustment of the pore structure, it is of substantial interest to be able to control this process comprehensively. In this study, a Heckel-based model equation is supplemented by a predictive model for the lowest achievable coating porosity based on the theoretical packing structures of equally sized spheres. Using this approach, the influence of different active materials, varying in particle size distribution and mechanical characteristics, on the compaction behavior is examined. An addition of smaller particles as well as increased initial porosities due to coarser particles decrease the compaction resistance. Furthermore, the impact of increasing mass loadings of the coating on the compaction resistance is analysed, resulting in a linear proportional relationship for the considered range from 80 to 280 g/m2.