Broad Particle Size Distribution Research Articles

Eulerian Deposition Model for Sediment Mixture in Gravel-Bed Rivers with Broad Particle Size Distributions

AbstractPredicting sediment transport and river morphodynamics is a challenging task in gravel-bed rivers where sediment mixtures have various particle sizes. In this study, we derive a binary pack...

Synergetic Effect of Water-Soluble PEG-Based Macromonomers and Cellulose Nanocrystals for the Stabilization of PMMA Latexes by Surfactant-Free Emulsion Polymerization.

The combination of cellulose nanocrystals (CNCs) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) was evaluated to synthesize stable latexes by surfactant-free emulsion polymerization of methyl methacrylate (MMA). Cellulose-particle interaction was provided due to the dual role of PEGMA, acting as water-soluble comonomer with MMA under emulsion polymerization conditions and able to interact with CNCs, recovered from sulfuric acid hydrolysis (H2SO4-CNCs). After preliminary experiments designed to validate the affinity between CNCs and PEG-stabilized PMMA particles obtained by MMA/PEGMA emulsion copolymerization, the effect of the PEGMA content and molar mass and also of the content of CNCs on the kinetics of the polymerization and the stability of the latexes were investigated. The use of PEGMA300 (Mn = 300 g mol-1, 2-10 wt %) allowed the formation of a stable latex, however, with a broad particle size distribution and the presence of both small (ca. 25-50 nm) and large (ca. 425-650 nm) particles (at 10 wt %, Dn = 278 nm and Dw/Dn = 1.34). Increasing the molar mass of PEGMA (PEGMA950 or PEGMA2080) significantly increased the fraction of small particles. This was explained by the nucleation and growth of small polymer particles adsorbed at the CNCs' surface, resulting in a particular organization where the CNCs were covered by several polymer particles. The influence of the initial amount of CNCs in these systems was finally evidenced, the polymerization being faster as the content of CNCs increased, but only the latexes prepared with 2 and 5 wt % of CNCs were stable.

Optical and magnetic properties of nanostructured cerium-doped LaMgAl11O19

Abstract

Enhancing packaging board properties using micro- and nanofibers prepared from recycled board

In this study, cellulose microfibers and cellulose nanofibers (CNF) prepared from recycled boxboard pulp using a mechanical fine friction grinder were used as reinforcements in a board sheet. Micro- and nanofibers manufactured by mechanical grinding have typically broad particle size distribution, and they can contain both micro- and nano-sized fibrils. Deep eutectic solvent of choline chloride and urea was used as a non-hydrolytic pretreatment medium for the CNF, and reference CNF were used without any chemical pretreatment. The CNF were ground using three grinding levels (grinding time) and their dosage in the board varied from 2 to 6 wt%. The results indicate that the board properties could be tailored to obtain a balance between the processability and quality of the products by adjusting the amount of CNF that was added (2–6 wt%). A preliminary cost assessment indicated that the most economical way to enhance the board strength properties was to add around 4% of CNF with a moderate grinding level (i.e., grinding energy of 3–4 kWh/kg). Overall, the strength properties of the manufactured board sheets improved by several dozen percentages when CNF was used as the reinforcement.

Stability of kaolin particles subjected to elevated temperatures using various dispersing agents

The stability of kaolin particles is largely influenced by nature and the behaviour of dispersing agents introduced to the system. This study analysed the size of kaolin particles subjected to elevated temperatures by using various dispersing agents such as ultrapure water (UPW), acetone (Ace) and sodium hydroxide (NaOH). It was found that kaolin particles in UPW formed a stable dispersion compared to particles in Ace and NaOH without further aggregation. Interestingly, kaolin particles under UPW, Ace, and NaOH dispersants had a strong affinity for water and can be classified as possessing hydrophilic behaviour. The mean size of kaolin particles was reduced under UPW and Ace dispersion but increased under NaOH suspension. Under UPW dispersion, kaolin particles ranged from 141.8nm to 5560nm, creating a mid-range monodisperse size distribution (0.08 < PDI < 0.7) without any presence of agglomeration due to high potential energy barrier and electrostatic repulsion. Kaolin particles subjected to NaOH dispersant produced a narrow distribution of particle sizes ranging from 295.3nm to 1106nm but appeared to agglomerate because of Van der Waals interactions. In contrast, the Ace dispersant produced a very broad polydisperse particle size distribution (PDI > 0.7) of greater than 10μm in kaolin with a little aggregation but lacking consistency in terms of stability. However, all dispersants contributed to the kaolin particles dispersion but UPW shown more stability dispersion due to increase in number of hydroxyl groups in dispersant molecule. In conclusion, this simple and low cost methodology can be useful in characterising kaolin particle sizes with limited resources.

Effect of O2/CO2 atmospheres on coal fragmentation

Recently, a single particle pyrolysis-combustion fragmentation model has been developed (Senneca et al., 2013, 2017) [1,2] to predict the propensity of coal particles to fragment under a wide range of heating conditions as a consequence of mechanical failure of the particle. Stress inside the particle arises from thermal shock, associated to particles’ heat up, as well as from overpressure generated by volatiles release upon devolatilization.The model is now used to calculate the propensity of coal particles to undergo fragmentation in the early stages of oxy-combustion, with gaseous atmospheres of 5–30% O2 in CO2 in entrained flow and fluidized beds reactors. Accordingly particles size of 0.1–10 mm are assumed, temperatures of 1123 and 2073 K, heating rates of 100 and 10,000 K/s.Results show that under entrained flow reactor conditions the particles break in the first 20–30 ms, producing a bimodal particle-size distribution. Under fluidized bed conditions, the particles undergo explosive fragmentation after 1–2 s, before pyrolysis is complete, generating broad particle size distribution. In both cases fragmentation occurs over short timescales compared to char combustion and gasification.Operative conditions where fragmentation occurs before or in parallel with char combustion or gasification are inferred by comparing on an Arrhenius plot the timescale of fragmentation and heterogeneous reactions for a larger array of operating conditions. The figure reveals that for high reaction temperatures, more reactive coals, larger particles size, gasification reactions can have an important role and maybe enhance porosity and percolative fragmentation.

Crystallisation parameters effect on the particle size distribution (PSD) of carbamazepine-saccharin (CBZ-SAC) co-crystals in batch cooling crystallisation

The crystallisation parameters effect on the particle size distribution (PSD) of carbamazepine-saccharin (CBZ-SAC) co-crystals in batch cooling crystallisation is presented. The particle size distribution study of CBZ-SAC co-crystals revealed that the multimodal with broad PSD was found for CBZ concentration of 19.14 mg/ml. Meanwhile, the unimodal with broad PSD were observed at CBZ concentration of 17.01 mg/ml and 17.96 mg/Crystal characterisation using differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), Fourier transform infrared (FTIR) and optical microscopy confirm the solid formed is CBZ-SAC co-crystal Form I with plate-like crystal morphology.

A Composite Analysis of Snowfall Modes from Four Winter Seasons in Marquette, Michigan

AbstractPresented are four winter seasons of data from an enhanced precipitation instrument suite based at the National Weather Service (NWS) Office in Marquette (MQT), Michigan (250–500 cm of annual snow accumulation). In 2014 the site was augmented with a Micro Rain Radar (MRR) and a Precipitation Imaging Package (PIP). MRR observations are utilized to partition large-scale synoptically driven (deep) and surface-forced (shallow) snow events. Coincident PIP and NWS MQT meteorological surface observations illustrate different characteristics with respect to snow event category. Shallow snow events are often extremely shallow, with MRR-indicated precipitation heights of less than 1500 m above ground level. Large vertical reflectivity gradients indicate efficient particle growth, and increased boundary layer turbulence inferred from observations of spectral width implies increased aggregation in shallow snow events. Shallow snow events occur 2 times as often as deep events; however, both categories contribute approximately equally to estimated annual accumulation. PIP measurements reveal distinct regime-dependent snow microphysical differences, with shallow snow events having broader particle size distributions and comparatively fewer small particles and deep snow events having narrower particle size distributions and comparatively more small particles. In addition, coincident surface meteorological measurements indicate that most shallow snow events are associated with surface winds originating from the northwest (over Lake Superior), cold temperatures, and relatively high surface pressures, which are characteristics that are consistent with cold-air outbreaks. Deep snow events have meteorologically distinct conditions that are accordant with midlatitude cyclones and frontal structures, with mostly southwest surface winds, warmer temperatures approaching freezing, and lower surface pressures.

Micro/nanocellulose from waste Pili (Canarium ovatum) pulp as a potential anti-ageing ingredient for cosmetic formulations

Abstract The potential of nanocellulose synthesized from waste pili pulp to replace mineral-based ingredients in cosmetics has been determined. Waste Pili pulp is biomass that comes from the extraction process, in the production of Pili essential oils. Conventional methods of cellulose extraction: boiling, alkalization and bleaching methods were employed to isolate cellulose from lignocellulosic and hemicellulosic materials. Sulfuric acid hydrolysis at 64 wt % has been used to synthesize nanocellulose at varying reaction times (30, 45 and 60 minutes). Infrared spectrum of the isolated cellulose has an 85% match with α-cellulose. The conditions for acid hydrolysis produced micro-sized cellulose with an average particle size of 3.4×105 nm or 34 µm and exhibited broad particle size distribution due to rapid agglomeration of some of its particles. Surface morphology analysis showed the nanostructures of the synthesized micro/nanocellulose at different time regimes. The optical properties of the cellulose suspensions were found almost parallel to that of the conventional mineral-based nanoparticles used in cosmetics; verifying nanocellulose as a promising alternative to mineral-based ingredients for cosmetics

Effective size separation of laser-generated, surfactant-free nanoparticles by continuous centrifugation

High-power, nanosecond, pulsed-laser ablation in liquids enables the continuous synthesis of highly pure colloidal nanoparticles (NPs) at an application-relevant scale. The gained mass-weighted particle size distribution is however often reported to be broad, requiring post treatment like centrifugation to remove undesired particle size fractions. To date, available centrifugation techniques are generally discontinuous, limiting the throughput and hindering economic upscaling. Hence, throughout this paper, a scalable, continuously operating centrifugation of laser-generated platinum NPs in a tubular bowl centrifuge is reported for the first time. To that end, using a 121 W ns-laser, the continuous production of a colloidal suspension of NPs, yet with broad particle size distribution has been employed, yielding productivities of 1–2 g h−1 for gold, silver, and platinum. The power-specific productivities (Au: 18 mg h−1 W−1, Pt: 13 mg h−1 W−1, Ag: 8 mg h−1 W−1, Ni: 6 mg h−1 W−1) are far higher than reported before. Subsequent downstream integration of a continuously operating tubular bowl centrifuge was successfully achieved for Pt NPs allowing the removal of undesired particle size with high throughput. By means of a systematic study of relevant centrifugation parameters involved, effective size optimization and respective size sharpness parameters for a maximum Pt NP diameter of 10 nm are reported. The results of the experimental centrifugation of laser-generated Pt NPs were in excellent agreement with the theoretically calculated cut-off diameter. After centrifugation with optimized parameters (residence time of 5 min; g-force of 38,454 g), the polydispersity indices of the Pt NPs size distributions were reduced by a factor of six, and high monodispersity was observed.

Influence of size‐classified and slightly soluble mineral additives on hydration of tricalcium silicate

AbstractEarly‐age hydration of cement is enhanced by slightly soluble mineral additives (ie, fillers, such as quartz and limestone). However, few studies have attempted to systematically compare the effects of different fillers on cementitious hydration rates, and none have quantified such effects using fillers with comparable, size‐classified particle size distributions (PSDs). This study examines the influence of size‐classified fillers [ie, limestone (CaCO3), quartz (SiO2), corundum (Al2O3), and rutile (TiO2)] on early‐age hydration kinetics of tricalcium silicate (C3S) using a combination of experimental methods, while also employing a modified phase boundary and nucleation and growth model. In prior studies, wherein fillers with broad PSDs were used, it has been reported that between quartz and limestone, the latter is a superior filler due to its ability to partake in anion‐exchange reactions with C‐S‐H. Contrary to prior investigations, this study shows that when size‐classified and area matched fillers are used—which, essentially, eliminate degrees of freedom associated with surface area and agglomeration of filler particulates—the filler effect of quartz is broadly similar to that of limestone as well as rutile. Results also show that unlike quartz, limestone, and rutile—which enhance C3S hydration kinetics—corundum suppresses hydration of C3S during the first several hours after mixing. Such deceleration in C3S hydration kinetics is attributed to the adsorption of aluminate anions—released from corundum's dissolution—onto anhydrous particulates’ surfaces, which impedes both the dissolution of C3S and heterogeneous nucleation of C‐S‐H.

Dynamics of Magnetic Fluids in Crossed DC and AC Magnetic Fields.

In this study, we derived the equations describing the dynamics of a magnetic fluid in crossed magnetic fields (bias and alternating probe fields), considering the field dependence of the relaxation times, interparticle interactions, and demagnetizing field has been derived. For a monodisperse fluid, the dependence of the output signal on the bias field and the probe field frequency was constructed. Experimental studies were conducted in a frequency range up to 80 kHz for two samples of fluids based on magnetite nanoparticles and kerosene. The first sample had a narrow particle size distribution, low-energy magneto dipole interactions, and weak dispersion of dynamic susceptibility. The second sample had a broad particle size distribution, high-energy magneto dipole interactions, and strong dispersion of dynamic susceptibility. In the first case, the bias field led to the appearance of short chains. In the second case, we found quasi-spherical clusters with a characteristic size of 100 nm. The strong dependence of the output signal on the particle size allowed us to use the crossed field method to independently estimate the maximum diameter of the magnetic core of particles.

Co-production of hydrogen and carbon nanomaterials using NiCu/SBA15 catalysts by pyrolysis of a wax by-product: Effect of Ni–Cu loading on the catalytic activity

The simultaneous production of H2 and carbon nanomaterials (CNMs) over NiCu/SBA15 catalysts with different Ni–Cu contents (10, 20, 30, 40 and 50 wt%) was investigated using the pyrolysis-catalysis process of paraffin wax. The fresh and spent catalysts were characterized by various techniques including H2-TPR, XRD, TEM, Raman spectroscopy and BET surface area. TEM observations showed that broad particle size distributions were formed in fresh 40NiCu/SBA15 and 50NiCu/SBA15 catalysts, while catalysts with smaller Ni–Cu contents displayed better metals dispersion. We found that the catalyst activity is related to the type of carbon nanomaterials, catalyst particle size, and catalyst loading with Ni–Cu. Also, the largest yield of H2 and CNMs was achieved using the 30NiCu/SBA15 catalyst. NiCu/SBA15 catalysts with Ni-Cu contents of 30–50 wt% exhibited good catalytic stability and similar activity in terms of H2 yield, especially at reaction time above 225 min. Small diameters carbon nanofibers (CNFs) were produced over the 10NiCu/SBA15 catalyst, while a mixture of CNFs and carbon nano-onions (CNOs) was produced using catalysts with Ni-Cu loadings of 20–50 wt%. The generation of octopus-like CNFs over large catalyst particles was associated with the observed catalytic stability of H2 production. Raman spectroscopy and XRD analyses demonstrated the formation of the best quality CNMs using the 20NiCu/SBA15 catalyst.

Number-sensitive particle size measurements for monitoring flocculation responses to different grinding conditions

In gravity thickening, higher levels of fine particles within the feed slurry typically lead to reduced flocculation performance relative to that achieved at the optimal solids concentration and flocculant dosage. Grinding is applied prior to separation processes (e.g. flotation, leaching) to liberate valuable material, and the higher grinding required for finely disseminated minerals substantially increases the fines fraction. To quantify the potential impact on flocculation efficiency of excessive fines formation within feeds to gravity thickeners, slurries of one ore type with seven different particle size distributions (PSDs) were produced by a combination of grinding and blending different size fractions. Sizings by volume- or mass-sensitive methods for these broad PSDs are dominated by coarser particles, despite their contribution to particle numbers being very low. Chord length distributions acquired in situ by focused beam reflectance measurement (FBRM) give real-time indications of size at high solids concentrations, and the raw (unweighted) counts are sensitive to particle number. The results of experiments with the different feed PSDs showed flocculation was strongly affected by fines and thereby particle number. FBRM therefore offers considerable scope for monitoring feed properties in terms of potential flocculation performance.Many flocculation studies focus on a single solids concentration, but useful comparisons for different PSD feed slurries can only be made by testing across multiple concentrations and flocculant dosages, with settling data then converted to solids settling flux. Flux values varied by an order of magnitude at a fixed dosage across the PSD extremes. While tripling the dosage significantly increased fluxes for slurries containing high levels of fines at their optimum solids concentration (~100 kg m−3), much higher fluxes were attained with coarser PSDs at both higher concentrations and lower dosages. When flocculating slurries of the seven PSDs at a fixed dosage, the solids settling flux increased as FBRM counts <20 µm prior to flocculation declined; scope for using FBRM in feed-forward control is discussed.

Ultrafine calcium carbonate-filled natural rubber latex film: mechanical and post-processing properties

This study aims to improve the dispersion of treated calcium carbonate (CaCO3) in natural rubber latex (NRL) films. Ball mill and ultrasonic methods were used to break down the particle size of CaCO3, and the combined effect of ball mill/ultrasonic and ultrasonic/ball mill methods with their optimum processing times was applied to re-agglomerate and further break down the particle size of CaCO3. The particle size and dispersibility of treated CaCO3 were characterized by particle-size analysis, transmission electron microscopy (TEM), and Zeta-potential measurement. The particle-size analysis and TEM results revealed that the particle size of CaCO3 reduced down to 1.4 µm with less agglomeration using ultrasonic for 120 min and ball mill for 72 h. Zeta--potential measurement also indicated that the ultrafine-treated CaCO3 with a broad particle-size distribution was compatible with NRL particles. The treated CaCO3 loadings from 5 to 20 phr were filled in the NRL compounds. NRL/CaCO3compounds showed decrease in viscosity and cross-link density, but increase in swelling index. It was found that tensile strength, modulus at 100% elongation, elongation-at-break, swelling index, and cross-link density of the films were improved with addition of 10 phr of CaCO3. At 20 phr of filler loading, the increment rate of tensile strength of NRL/CaCO3 films was 44% after leaching, and their retention percentage was 62% after heat aging. Therefore, ultrafine CaCO3-incorporated NRL can withstand under accelerated heat-aging condition.

The role of Fe particle size and oxide distribution on the hydrogenation properties of ball-milled nano-crystalline powder mixtures of Fe and Mg

In the aim of evidencing the relationship between Mg2FeH6 synthesis and the size of Fe particles, several specimens have been prepared by applying various milling energies (milling time) on a 2.1 Mg and 1Fe powder mixture doped with a small fraction of Unsaturated Fatty Amine (UFA). The resulting nano-crystalline composite structures display a broad Fe particle size distribution as a function of milling time. The hydrogenation of those complex powders has been conducted at temperatures lower than 400 °C under 60 bar of hydrogen pressure. As expected, the Fe particle size significantly influenced the hydrogenation kinetics. Also, the inevitable distribution of a minor fraction of oxides occurring during the milling process affected greatly the hydrogen storage capacity.Under the low pressure and temperature conditions selected in the frame of this study, lower than 100 bar and 500 °C conventionally used for synthesis of high purity Mg2FeH6, the hydrogenation reaction was demonstrated to be almost completed within 6 h, confirming the fast hydrogen absorption capability of the prepared materials. Plus, nearly 84 wt% of Mg2FeH6 was achieved under the afore mentioned moderate conditions and a minor fraction of unreacted Fe still remained due to diffusion constraints existing at low temperatures.

Multi-angle dynamic light scattering analysis based on successive updating of the angular weighting

The angular weighting coefficient is key to accurate particle size distribution (PSD) measurement using multiangle dynamic light scattering (MDLS). However, determining the weighting coefficient is affected by the noise in the measured MDLS data. In this paper, a novel successive updating of the angular weighting (AWSU) method is proposed. By using information character weighting, the angular weighting coefficient and the character weighting matrix are updated once with each additional angle. The effect of autocorrelation function (ACF) denoising and information extraction is improved by using information character weighting step-by-step. The results for broad unimodal and closely-spaced bimodal PSDs demonstrate the effectiveness of this method. Compared with another routinely used inversion method, it is found that the increase in PSD information retrieved from MDLS depends not only on increasing the number of angles, but also on the calculation of the angular weightings. An accurate weighting algorithm can reduce the number of scattering angles required. Using the AWSU method for PSD recovery with 4 scattering angles can give better results than the usual method with 6 scattering angles. It is also found that the AWSU method not only improves the accuracy of the weightings, but it also contributes directly to the PSD recovery by reconstructing the ACF with the PSD obtained by the weighted inversion. The combination of these two contributions not only reduces the number of scattering angles needed, but also keeps the PSD recovery results from getting worse because of excessive scattering angles.

Subvisible Particulate Matter in Therapeutic Protein Injections

Strategies for determining particulate matter in therapeutic protein injections, including extrinsic and intrinsic particles, are reviewed. Special attention is devoted to the advantages and limitations of various methods used for these purposes, each of which enables different particle characteristics to be determined. The source of particles (extrinsic, intrinsic, or inherent) can be understood better and particle-size distribution and other characteristics can be studied and used to differentiate them if methods based on different measurement principles are used. Protein aggregates in drugs have broad particle-size distributions, from oligomers to particles reaching hundreds of microns. The particle properties can be used to assess the risk associated with protein aggregates in the drug and to study their possible formation mechanisms. Such information could be useful during drug development and manufacturing to reduce the particulate matter content.

Towards online Near-Infrared spectroscopy to optimise food product mixing

This paper advances the use of in-situ Near-Infrared (NIR) spectroscopy as the basis for an in-line control system to optimise mixing time of food powder blends. A non-contact NIR fibre-optic probe installed in a conical screw mixer was used to scan three powder mixtures characterised by different particle size distribution and component distribution. The current state of the art is extended by comparing Conformity Index and Standard deviation of the Moving Block Standard Deviation (MBSD), establishing the optimal pre-treatment combination and investigating the effects of the mixture properties on the results. Products with a broad particle size distribution were more accurately represented using derivatives rather than SNV and Detrending, while products with a broad component distribution showed good results with all pre-treatments.This study evaluated the effect of data pre-treatments on mixing time for different physical properties of powder blends and provided a general guidance on the most appropriate pre-treatment.

Origin and prevention of broad particle size distributions in carbon-supported palladium catalysts prepared by liquid-phase reduction

Carbon-supported palladium (Pd/C) catalysts often display broad or multimodal Pd particle size distributions detrimental for their performance. Therefore, the formation of large particles during preparation should be better understood and avoided. We prepared catalysts with up to 10 wt% Pd supported on oxygen-functionalized carbon nanotubes and activated carbon via liquid-phase reduction. It was inferred that small Pd particles (∼1 nm) were formed from Pd ions adsorbed on the carbon. At higher loadings, up to 65% of the Pd ended up in larger particles (>10 nm) probably formed from Pd ions in solution, lowering the Pd-normalized activity in the hydrogenation of cinnamaldehyde 4-fold compared to samples with small particles only. Three key factors were identified for preparing Pd/C catalysts with exclusively ∼1 nm Pd particles: a support with a high density of acid sites and high specific surface area, and a metal loading at molar ratio Pd/acid sites <0.5.