Single Particle Size Research Articles

Quantitative NIR spectroscopy determination of coco-peat substrate moisture content: Effect of particle size and non-uniformity

The particle size and non-uniformity of solid particle samples directly affected the acquisition of samples spectral data. In this study, different particle size samples and mixed samples with two different particle size grade samples were applied to investigate the impact of particle size and non-uniformity on near-infrared (NIR) spectroscopy detection of moisture content in coco-peat substrate. Simultaneously, the pretreatment effect and capability of MSC and SNV on spectral scattering were studied. The results showed that the prediction accuracy of the spectral detection model for moisture content in coco-peat substrate was higher with smaller particle size or smaller non-uniformity; MSC and SNV had better effects on improving the accuracy of prediction models with small particle size samples or small non-uniformity samples; the optimal moisture content spectral prediction models for single particle size grade samples and mixed samples of two particle size grades could be respectively established when SNV was adopted to pretreat the samples spectral data of A and A-B. And the corresponding correlation coefficients of the two optimal models were 0.9964 and 0.9959 for calibration set, 0.9959 and 0.9957 for prediction set, respectively; the root mean square errors were 1.2299% and 1.0090% for calibration set, 1.2820% and 1.0723% for prediction set, respectively; the ratios of prediction to deviation were 10.83 and 10.51, respectively. The prediction model with the minimal spectral scattering influence could be built by combining physical pretreatment with spectral pretreatment. This study would provide a reference for reducing the scattering effect of solid particle sample spectral detection.

Development and application of three-directional compression testing system for gangue backfill in deep mine

ABSTRACT Based on the research background of bearing compression deformation of filling gangue in deep mines, athree-directional compression testing system of gangue was developed independently to carry out the three-directional compression tests of single-particle size gangue. Furthermore, the compression deformation characteristics of gangue particles during the three-directional loading were also studied. Firstly, the composition and technical parameters of the self-developed three-directional compression testing system for gangue were introduced and compared with the results of aconventional gangue compression test. Through the three-directional compression tests of gangue samples, it was shown that the influence of the lateral stress on the lateral strain of gangue samples was greater than that of the particle size on the lateral strain. With the increase of initial confining pressure, the volume strain of gangue samples increased with the increase in the particle size of gangue samples. Furthermore, larger the volume strain of the sample, larger was the volume strain of the gangue sample. Additionally, the particle size of 50–60mm could reach 0.398. The microanalysis of the three-directional compression of the gangue filling material showed that the force chain skeleton of the gangue sample was evenly distributed in the three-directional compression process. When the volume strain increased from 0 to 0.3, the mutual penetration degree of the internal force chains of the sample gradually increased. Larger the initial confining pressure, higher was the total number of the contact force chains. Alarge number of voids in the sample was gradually compacted and filled to improve its bearing capacity.

Influence of grain growth on the thermal structure of protoplanetary discs

The thermal structure of a protoplanetary disc is regulated by the opacity that dust grains provide. However, previous works have often considered simplified prescriptions for the dust opacity in hydrodynamical disc simulations, for example, by considering only a single particle size. In the present work, we perform 2D hydrodynamical simulations of protoplanetary discs where the opacity is self-consistently calculated for the dust population, taking into account the particle size, composition, and abundance. We first compared simulations utilizing single grain sizes to two different multi-grain size distributions at different levels of turbulence strengths, parameterized through the α-viscosity, and different gas surface densities. Assuming a single dust size leads to inaccurate calculations of the thermal structure of discs, because the grain size dominating the opacity increases with orbital radius. Overall the two grain size distributions, one limited by fragmentation only and the other determined from a more complete fragmentation-coagulation equilibrium, give comparable results for the thermal structure. We find that both grain size distributions give less steep opacity gradients that result in less steep aspect ratio gradients, in comparison to discs with only micrometer-sized dust. Moreover, in the discs with a grain size distribution, the innermost (<5 AU) outward migration region is removed and planets embedded in such discs experience lower migration rates. We also investigated the dependency of the water iceline position on the alpha-viscosity (α), the initial gas surface density (Σg,0) at 1 AU and the dust-to-gas ratio (fDG) and find rice ∝ α0.61Σg,00.8fDG0.37 independently of the distribution used in the disc. The inclusion of the feedback loop between grain growth, opacities, and disc thermodynamics allows for more self-consistent simulations of accretion discs and planet formation.

Sharp scattering spectra induced brilliant and directional structural colors

Structural color materials, which generate colors through the interaction between light and nano-microstructures, have always been research hotspots in the fields of display, anticounterfeiting and stimuli-responsive materials. Structural colors based on scattering have received increasing attention due to their wider viewing angles than that originating from the specular reflection of photonic crystals. However, the wide scattering spectrum of an amorphous structure leads to lower purity and brightness of the appeared colors. Few researchers have focused on the scattering of ordered structures due to their strong reflection and diffraction in the visible regions. In this work, by building ordered films (OFs) using SiO2 spheres (refractive index n = 1.46) with a diameter of 300–500 nm, for the first time, sharp scattering spectra with narrow full width at half-maximum (FWHM, 24 nm) were generated. Importantly, under ambient light, brilliant colors covering the entire visible region can be observed, and a formula was proposed to calculate the scattering spectra of OFs. Moreover, rainbow structural color was realized under irradiation of the nonparallel light, and full-spectrum structural color patterns were fabricated using building blocks with a single particle size by a spraying method. Finally, a composite structure was constructed to explore possibilities in the field of flexible transparent displays.

Particle Size Distribution of Bimodal Silica Nanoparticles: A Comparison of Different Measurement Techniques.

Silica nanoparticles (SNPs) belong to the most widely produced nanomaterials nowadays. Particle size distribution (PSD) is a key property of SNPs that needs to be accurately determined for a successful application. Many single particle and ensemble characterization methods are available for the determination of the PSD of SNPs, each having different advantages and limitations. Since most preparation protocols for SNPs can yield bimodal or heterogeneous PSDs, the capability of a given method to resolve bimodal PSD is of great importance. In this work, four different methods, namely transmission electron microscopy (TEM), dynamic light scattering (DLS), microfluidic resistive pulse sensing (MRPS) and small-angle X-ray scattering (SAXS) were used to characterize three different, inherently bimodal SNP samples. We found that DLS is unsuitable to resolve bimodal PSDs, while MRPS has proven to be an accurate single-particle size and concentration characterization method, although it is limited to sizes above 50 nm. SAXS was found to be the only method which provided statistically significant description of the bimodal PSDs. However, the analysis of SAXS curves becomes an ill-posed inverse mathematical problem for broad size distributions, therefore the use of orthogonal techniques is required for the reliable description of the PSD of SNPs.

Gravity-Driven Monodisperse Avalanches: Inertial- to Frictional-Dominated Flow

A set of experiments on avalanches—each one with a single particle size (monodisperse)—is presented. Experiments were performed with different flume lengths, inclinations, and roughness, for different avalanching masses and particle sizes. A transition from an inertial behavior to a frictional dominated one is observed at a particle size of 1 mm, in all cases. Taking into account the energy dissipated during each step of the avalanching process, we inferred a scaling function that allowed us to collapse all experimental data into a single curve. The transition from an inertial to a frictional dominated regime is explained in terms of the increasing number of particles per unit mass with decreasing particle size, for which the external shear activates a growing number of internal degrees of freedom in which the energy is dissipated. Molecular dynamic numerical simulations showed consistency with the suggested hypothesis of higher dissipated power for larger number of avalanching particles (smaller grain size).

Multi-Size Proppant Pumping Schedule of Hydraulic Fracturing: Application to a MP-PIC Model of Unconventional Reservoir for Enhanced Gas Production

Slickwater hydraulic fracturing is becoming a prevalent approach to economically recovering shale hydrocarbon. It is very important to understand the proppant’s transport behavior during slickwater hydraulic fracturing treatment for effective creation of a desired propped fracture geometry. The currently available models are either oversimplified or have been performed at limited length scales to avoid high computational requirements. Another limitation is that the currently available hydraulic fracturing simulators are developed using only single-sized proppant particles. Motivated by this, in this work, a computationally efficient, three-dimensional, multiphase particle-in-cell (MP-PIC) model was employed to simulate the multi-size proppant transport in a field-scale geometry using the Eulerian–Lagrangian framework. Instead of tracking each particle, groups of particles (called parcels) are tracked, which allows one to simulate the proppant transport in field-scale geometries at an affordable computational cost. Then, we found from our sensitivity study that pumping schedules significantly affect propped fracture surface area and average fracture conductivity, thereby influencing shale gas production. Motivated by these results, we propose an optimization framework using the MP-PIC model to design the multi-size proppant pumping schedule that maximizes shale gas production from unconventional reservoirs for given fracturing resources.

Particle resolved CFD simulation on vapor-phase synthesis of vinyl acetate from ethylene in fixed-bed reactor

The synthesis of vinyl acetate (VAc) from ethylene is a strongly exothermic reaction that might easily cause catalyst deactivation and reduce selectivity of VAc. Research at the bed scale helps to improve the conversion of C2H4 and the selectivity of VAc. In this study, the discrete element method (DEM) was used to construct a fixed-bed structure model via simulating the filling process of catalyst particles in the reactor. The inlet section of a reaction tube was studied, and its length was 10 cm. The temperature distribution, and the effects of particles size, inlet velocity, inlet temperature and the feed ratio of C2H4 to O2 on the reaction process were studied. Simulated results show that the bed temperature gradually increased from the wall to the center, and the temperature gradient gradually decreased along the radial direction. The maximum temperature was 438.68 K and the temperature difference from the inlet temperature was 5.54 K. Comparing the composite particle packed bed with the single particle size packed bed, the composite packed bed has higher vinyl acetate selectivity. Increasing inlet velocity from 1.5 m/s to 3.5 m/s, the selectivity of vinyl acetate increased from 91.71% to 92.60%. Adding an inert gas to the feed gas can increase the oxygen concentration and reduce the explosion interval of QH4, the conversion of C2H4 and the selectivity of vinyl acetate increased.

The Reservoir Adaptability and Oil Displacement Mechanism of Polymer Microspheres.

Polymer microsphere profile control is a promising approach for the profile control of heterogeneous reservoirs. Matching between polymer microspheres and the reservoir pore throat is crucial for profile control. In this study, the range of the optimal matching factor Ra between polymer microspheres and core porosity was divided through core permeability limit experiments, and the dynamic migration laws and shut-off patterns of microspheres were studied using 9-m-long cores and microscopic models. The oil displacement effect and mechanism of microspheres were analyzed using three cores in parallel. The “injectability limit” and “in-depth migration limit” curves were divided by Ra into three zones: blockage (Ra < 1.09 ± 0.10), near-well profile control (1.09 ± 0.10 < Ra < 5.70 ± 0.64), and in-depth fluid diversion (Ra > 5.70 ± 0.64). During migration in porous media, the microspheres gradually enlarged in size and thus successively shut off in four forms: multi-microsphere bridging shut-off, few-microsphere bridging shut-off, single-microsphere shut-off, and elastic shut-off. Microspheres with a rational combination of sizes versus those with a single particle size further enhanced reservoir oil recovery under certain reservoir conditions. Through “temporary shut-off–breakthrough–temporary shut-off,” the polymer microspheres were able to change the fluid flow rate and streamlines, mobilize residual oils, and enhance the oil recovery rates.

Influence of the Mineral Content on the Emissivity of Hydrothermal Char

AbstractThe influence of minerals on solid fuel conversion is an important topic and has so far been addressed focusing mainly on the catalytic effects. Here, the impact of iron oxide on the emissivity of burning char particles was investigated. Synthetic, hydrothermally carbonized char was doped with SiO2 or with a mixture of SiO2 and Fe2O3. The sample was then exposed to an oxy‐fuel atmosphere in a laboratory reactor. An established pyrometer/infrared (IR) spectrometer setup was used to measure the size, temperature, and IR radiation of single burning particles. Based on these measurements, the spectral and total emissivity in the near‐IR (1.25–2.25 μm) and the total emissivity in the mid‐IR region (2.4–5.5 μm) were calculated. The results show that the iron content directly influences the emissivity of char during combustion.

Evaluation of Performance and Tunability of a Co-Flow Inertial Microfluidic Device.

Microfluidics has gained a lot of attention for biological sample separation and purification methods over recent years. From many active and passive microfluidic techniques, inertial microfluidics offers a simple and efficient method to demonstrate various biological applications. One prevalent limitation of this method is its lack of tunability for different applications once the microfluidic devices are fabricated. In this work, we develop and characterize a co-flow inertial microfluidic device that is tunable in multiple ways for adaptation to different application requirements. In particular, flow rate, flow rate ratio and output resistance ratio are systematically evaluated for flexibility of the cutoff size of the device and modification of the separation performance post-fabrication. Typically, a mixture of single size particles is used to determine cutoff sizes for the outlets, yet this fails to provide accurate prediction for efficiency and purity for a more complex biological sample. Thus, we use particles with continuous size distribution (2–32 μm) for separation demonstration under conditions of various flow rates, flow rate ratios and resistance ratios. We also use A549 cancer cell line with continuous size distribution (12–27 μm) as an added demonstration. Our results indicate inertial microfluidic devices possess the tunability that offers multiple ways to improve device performance for adaptation to different applications even after the devices are prototyped.

Percolation characteristics of multi-polymer composites with different ratios of nanocarbon fillers

We have investigated the concentration and thermal dependences of electrical conductivity of multi-composites with different ratios of two nanocarbons. The concentration curve consists of quasi-dynamic and static percolation threshold, two saturation curves. A synergistic effect is observed for both new multi-composites, but in a certain range. We think that the value of percolation threshold, the height and width of the conductivity saturation in multi-composites are influenced by many factors: the concentration of nanocarbons, the number and size of carbon nanotube (CNT) agglomerates and single CNT particles, the different ratio of the number of longer CNT particles to short.

Effects of grading tungsten powders on properties of CuW alloy

Considering the advantages and disadvantages of CuW alloys with different single particle size of tungsten powder, CuW alloys with three kinds of tungsten powders: ultramicron (50 μm), micron(6–8 μm), submicron(0.4 μm) were prepared by the infiltration method. Microstructure of the CuW alloy with different grading ration of tungsten powder were characterized via field-emission scanning electron microscope (SEM). The Vacuum electrical breakdown properties were studied by electrical breakdown test. The results shows that the grading tungsten powders can form a variety of W-W sintered necks, strengthen the tungsten skeleton. SEM results show that a suitable ratio of grading tungsten powders can make the infiltrated copper phase more dispersed and uniform. Compared with the tradition CuW alloy, the conductivity is greater than 53.5%IACS, with the lowest hardness of 203HB, the lowest CuW/CrCu bonding strength of 417 MPa and the highest of 495 MPa, the hardness and electrical conductivity increased by 20%–30%, the bonding strength of new CuW/CrCu monolithic materials increased by 20%, vacuum electrical breakdown properties performed good.

On SiC/Al2O3 reinforced HDPE 3D printed rapid tooling

This work reports the in-house fabrication of SiC/Al2O3 reinforced rapid tooling (RT) using feed stock filament prepared by single screw extrusion for fused deposition modelling (FDM) platform. The current investigation focuses on preparation of high density polyethylene (HDPE) matrix reinforced with single particle size, dual particle size and triple particle size for RT applications. The study suggests that triple particle size of Al2O3 is best alternative among single, double and triple particle size of reinforcement for preparation of RT. Also the study highlights that the infill density (ID) plays significant and most important input processing parameter for preparation of RT comprising of HDPE composite matrix from dimensional accuracy and hardness view point. The differential scanning calorimetry (DSC) study suggested us that the RT prepared with HDPE composite matrix is thermally stable.

Wear properties of rapid tooling prepared by reinforcement of SiC/Al2O3 in HDPE domestic waste

This study highlights the fabrication of rapid tooling (RT) with improved wear properties from the domestic polymeric waste of high density polyethylene (HDPE) by reinforcement of SiC/Al2O3. The RT were prepared with HDPE and different particle sizes of SiC/Al2O3 (having single particle sizes (SPS); dual particle sizes (DPS) and tri-particle sizes (TPS) in form of reinforcement). The process started with establishing melt flow index (MFI) of the polymer composites (PC). After establishing MFI, the selected PC was used for filament wire preparation on twin screw extruder (TSE). The wires so prepared were put to mechanical testing, after which these wires were fed to 3D printer (fused deposition modelling (FDM) open source) for preparation of functional prototypes. The cylindrical pins printed on FDM were further subjected on pin on disc setup to investigate the wear properties. As per results of the present study it has been ascertained that the better wear properties of the feed stock filaments is achieved by reinforcement of ceramic particles and can be used as RT. The SEM analysis of the pins was performed to understand the wear mechanism. Finally, thermographs were plotted to ensure the thermal stability of RT and ensure the credibility of manufacturing process adopted.

On wear of 3D printed Al2O3 reinforced Nylon6 matrix based functional prototypes

The use of fused deposition modelling (FDM) based functional prototypes for wear resistance applications is presently limited mainly because of selective material availability of filament materials. Various research groups have reinforced several fillers in thermoplastic base to prepare feedstock filaments to improve the mechanical properties and to address the reusability issue of polymeric waste. But hitherto the effect of Al2O3 particle sizes (as single, dual and triple particle size as reinforcement) in Nylon6 thermoplastic blend has been less explored. In the present investigation an effort has been made to prepare feed stock filament for 3D printing application to explore its wear resistant properties. The current investigation suggested that dual particle size reinforced pin exhibit better wear properties followed by triple and single particle reinforced pins. The wear tracks obtained in this study shows that dual particle size based composite material is highly wear resistant as compared to virgin acrylonitrile butadiene styrene (ABS)/ Nylon6. The results have been supported by scanning electron microscopy (SEM) images of prepared pins for wear testing.

Study on Characteristic Spectrum and Multiple Classifier Fusion With Different Particle Size in Marine Sediments

Marine sediments record much information of the ecological process, which highly correlated with global and local environmental change. Particle size and its distributions of sediments indicate different ecological functions, thus are the key questions in marine ecology. The analysis method is tedious and laborious, which is not conducive for in-situ monitoring. Here, a spectral analysis was explored using surface sediments sampled in the intertidal zone of Dongdayang village, Qingdao, China. These samples were dried and sieved to pass through the mesh size of 0.3 mm, 0.2 mm, 0.1 mm, and 0.075 mm, respectively. Then, four types of subsamples were collected with the particle size of 0.3-0.2 mm, 0.2-0.1 mm, 0.1-0.075 mm, and <; 0.075 mm, respectively. The visible and near infrared reflectance spectra (226-975nm) of these subsamples with different particle size were measured. Results showed that there was a negative correlation between the spectral reflectance and the particle size. And the characteristic spectra for particle size classification were 926-975nm. These particle size were classified by the support vector machine algorithm. The classification accuracy for the calibration set and validation set was 100% and 89.06%, respectively. Furthermore, the fusion classifier was compared with the single classifier. Three spectral bands were selected as the single particle size classifier, that is 226-325nm, 826-925nm and 226-975nm. These three single classifiers were fused by voting method, forming multiple classifier fusion. A fusion classifier was recommended whose validation set had the classification accuracy of 93.75%, better than any single classifier. Multiple classifier fusion is a good tool for searching the characteristic spectra of the chemical and physical parameter in sediments. This method provides a solution for the division of particle size in sediment.

Study on Interference Factors of Light Scattering PM2.5 Dust Test Instrument

Light scattering PM2.5 dust test instrument is widely used, but it is susceptible to many kinds of interference, and will produce large deviation in some industrial sites. The influence of particle size, relative humidity and other parameters on the measurement results of light scattering dust meter is studied and corrected. The experimental results show that the relative error of detecting single particle size dust is smaller than that of detecting multi-particle size dust. Relative humidity has no effect on non-hygroscopic dust detection, but has obvious influence on hygroscopic dust detection, and the relative error after correction is significantly reduced.

Experimental study and CPFD simulation on circumferential flow heterogeneity in a disc-donut catalyst stripper

Abstract Disc-donut strippers are widely equipped in fluid catalytic cracking (FCC) units of petroleum refineries. In this study, circumferential gas-solids flow heterogeneity in a disc-donut catalyst stripper was investigated using both experimental and CFD simulation approaches. A four-channel fiber optical densitometry was used to measure the radial gas-solids profiles synchronously from four different circumferential angles. Computational particle fluid dynamics (CPFD) model was used to simulate the experimental stripper section. It was found in experiment that the circumferential gas-solids distribution is highly heterogeneous throughout the disc-donut stripper. Local gas bypassing existed under all the experimental conditions. The CPFD model successfully predicted gas bypassing and circumferential flow heterogeneity in the disc-donut stripper. However, previous two-fluid model (TFM) simulations on disc-donut strippers using a single mean particle size can only predict axially symmetrical flow distribution. According to a series of sensitivity analyses, it is shown that the consideration of particle size distribution (PSD) is a possible key reason leading to the successful prediction of the circumferential flow heterogeneous by the CPFD model.

Identifying the soil structure of the piedmont-plains by the fractal dimension of particle size

Soil structure fundamentally determines the hydrodynamic characteristics of the saturated–unsaturated zone, solute transport characteristics, and thermodynamic properties of the soil. Additionally, it regulates the process of transfer and conversion of matter and energy in the saturated–unsaturated zone. However, the quantification of soil structure is difficult because it depends on a combination of factors including soil particle sizes and types and spatial distribution of pores. In this study, the structural characteristics of the vadose zone are examined based on self-similarity in the soil and the fractal theory of non-linear science. This approach describes the soil particle sizes and spatial distribution of pores in the interior layers of the soil. The study area stretches across 165 km of the piedmont–plains of the Taihang Mountains. The particle sizes and volume percentages of particle sizes in 57 soil samples were measured using the Mastersizer 2000 laser diffraction particle size analyser (Malvern Instruments, U.K.). This information is then combined with the volume-based fractal dimension (D), calculated using the fractal theory, of the various samples. The results obtained indicate that: (i) the fractal theory can be used to effectively identify the characteristics of three-dimensional structural changes within the soil profiles. The average soil particle size decreases from the piedmont of the Taihang Mountains towards the plains. Similarly, the volume percentage of particle size and the maximum volume percentage of a single particle size decreases. Moreover, the D values show an overall declining trend; (ii) the D values of the soils of the piedmont–plains of the Taihang Mountains show significant spatial variations in the range of 1.037–1.925. Although there is no correlation between the D value and soil particle size, the D value is very sensitive to the soil structure uniformity. The higher the uniformity, the greater is the D value; and (iii) D values cannot be used as the sole basis for determining the soil hydraulic properties. The D values and soil hydraulic properties are correlated only for a particular range of soil particle sizes.