Median Particle Size Research Articles

Laboratory Study of Interface Friction between Sand and Steel Surfaces

Abstract In this study, results have been reported from a series of laboratory tests to determine the interface friction angle of steel surfaces with sand through modified direct shear testing. For completion, steel surfaces with different surface geometry to replicate the roughness have been slid against various sands compacted at different relative densities under both dry and wet conditions. The standard square shape direct shear box has been modified into circular and rectangular boxes to sufficiently enhance the contact area and to subsequently quantify its effect on interface friction angle. A mild steel interface of smooth and rough texture with a groove depth of 0.2 mm and tipping at an angle of 90° has been used in this study. The analysis of results revealed that the interface friction angles obtained from the standard direct shear box agree closely with those obtained from both modified rectangular and circular shear boxes. However, the ratio of the interface friction angle from the modified apparatus and soil’s angle of internal friction significantly depends upon the roughness of the surface in contact with the sand, its median particle size, and is independent of the effects of box size, soil’s relative density, and dry or wet condition. A comparison between existing well-accepted guidelines and current observations has been presented for use by the practicing engineers dealing with soil-structure interaction.

Jet cavitation-enhanced hydration method for the preparation of magnesium hydroxide

During the preparation of magnesium hydroxide via the hydration method, in-situ growth and agglomeration often inhibit the reaction. This study used active magnesium oxide as the raw material and employed jet cavitation technology to enhance the hydration process. Based on the growth process of magnesium hydroxide, the mechanism of jet-enhanced hydration was analyzed. The effects of reaction temperature (T), reaction time (t), solid-liquid ratio (s), and cavitation number (σ) on the hydration rate were investigated. An L25(54) orthogonal experiment explored the significance of each factor's impact on the hydration rate. The hydration products were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and a specific surface area analyzer. Results indicate that the factors affecting the hydration rate, in order of significance, are cavitation number > reaction temperature > solid-liquid ratio > reaction time. The optimal process parameters were determined to be a reaction temperature of 70 °C, reaction time of 80 min, solid-liquid ratio of 1:12, and cavitation number of 0.42. Under these conditions, the hydration rate reached 94.87 %, producing well-dispersed lamellar magnesium hydroxide with a narrow particle size distribution (median particle size D50 = 4.511 μm) and a BET specific surface area of 11.345 m²/g.

Distinct roles of size-defined HDL subpopulations in cardiovascular disease.

Doubts about whether high-density lipoprotein-cholesterol (HDL-C) levels are causally related to atherosclerotic cardiovascular disease (CVD) risk have stimulated research on identifying HDL-related metrics that might better reflect its cardioprotective functions. HDL is made up of different types of particles that vary in size, protein and lipid composition, and function. This review focuses on recent findings on the specific roles of HDL subpopulations defined by size in CVD. Small HDL particles are more effective than larger particles at promoting cellular cholesterol efflux because apolipoprotein A-I on their surface better engages ABCA1 (ATP binding cassette subfamily A member 1). In contrast, large HDL particles bind more effectively to scavenger receptor class B type 1 on endothelial cells, which helps prevent LDL from moving into the artery wall. The specific role of medium-sized HDL particles, the most abundant subpopulation, is still unclear. HDL is made up of subpopulations of different sizes of particles, with selective functional roles for small and large HDLs. The function of HDL may depend more on the size and composition of its subpopulations than on HDL-C levels. Further research is required to understand how these different HDL subpopulations influence the development of CVD.

An analytical study of the tabia mortar from Lin Yimu’s tomb, Zhejiang, China

The Lin Yimu’s tomb in Zhejiang Province, China, is a significant Qing Dynasty tabia structure that, despite relatively good preservation, has suffered damage from weathering, necessitating urgent restoration. In this study, we conducted a comprehensive scientific analysis of archaeological samples from the tabia of Lin Yimu’s tomb, employing a range of analytical techniques including X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDX), Fourier transform infrared spectroscopy (FTIR), chemical methods, and measurements of hardness and strength. Analytical results revealed that the main phases of the sample are calcite, quartz, illite/mica, feldspar, with a minor presence of Tung oil. The proportion of calcium carbonate is approximately 27%, and the ratio of earth to sand is 1:2, suggesting a raw material formula mass ratio of lime-earth-sand of 3:4:8. The surface hardness of the sample is measured at 293 ± 15 HL, with a compressive strength of 5.5 ± 0.2 MPa. The sand used in the raw material has a medium particle size of 250 μm, while earth particles are predominantly around 17 μm. The sample exhibits a porosity of 27.5%, with pore sizes concentrated at 95 nm. These findings contribute significantly to our understanding of Qing dynasty tomb construction technologies and provide a solid scientific basis for the restoration of such historical sites.

Study on the preparation and modification mechanism of GO/SBR composite modified emulsified asphalt

This paper employs graphene oxide (GO) and anionic styrene-butadiene rubber (SBR) latex as modifiers for road-emulsified asphalt. A silane coupling agent (KH550) is used to modify GO, resulting in the development of a novel GO/SBR composite-modified emulsified asphalt. A mathematical model was optimized to determine the optimal material ratio, which was verified through performance tests. Techniques such as Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were utilized to investigate the modification mechanism. The results indicated that both the median particle size and storage stability of the GO/SBR composite-modified asphalt were enhanced, with significant improvements in mechanical properties compared to ordinary emulsified asphalt. Microscopic analysis revealed enhanced dispersion of modified GO in asphalt, and the interaction between modified GO and emulsified asphalt was determined to be purely a physical reaction. This study provides valuable insights into the application of GO in road engineering.

Comparison of lab-produced asphalt emulsions by manufacturing equipment type

Asphalt emulsions can be produced with colloid mills and high-speed shear mixers, but effects of equipment type on emulsion properties are largely unknown. The study objective was to assess the impact of different manufacturing equipments on emulsion properties. Particle size, viscosity, residue, sieve and storage stability properties were observed after production on three emulsion manufacturing devices. For each device, three emulsions were manufactured by three operator pairs. Median particle size was as small as 2.0 microns on recirculating and in-line equipment, but only 5.3 on high-speed shear mixer. Recirculating equipment also produced emulsion with better storage stability than high-speed shear mixer and in-line equipment. In-line manufactured emulsions had the highest viscosity while the shear-mixed emulsion viscosity was below specification. Sieve was significantly affected by the operator. These results demonstrate that emulsions produced by different laboratory equipment are not identical, and caution must be exercised when comparing and manufacturing lab-produced emulsions.

Real-time monitoring of integrated continuous granulation/drying line system “LaVortex®” for the pharmaceutical manufacturing of acetaminophen oral dosage formulations using near-infrared spectroscopy

Granules for tableting were continuously manufactured using a fully flow-type continuous wet-granulation and drying (CGD) line system, “LaVortex®.” The raw material powder containing standard excipients and 28.8 % acetaminophen was mixed with a binder liquid (pure water), continuously wet-granulated, and dried for 600 s under 20 different granulation/drying process conditions, and the process was monitored in real-time using near-infrared (NIR) spectroscopy. Twenty granulation/drying process conditions, varying across three parameters, namely added binding water rate, agitation blades and container rotational rates, and hot drying air flow rate, were applied. Training datasets from NIR spectroscopy stably measured during the CGD process were used to construct calibration models to predict the various critical quality attributes (CQAs) of granules, such as residual moisture content, median particle size, angle of repose, and tablet hardness, using partial least squares regression (PLSR). Optimal calibration models were validated using the NIR spectroscopy test dataset. The actual granule CQA profiles evaluated using the NIR/PLSR method were almost constant up to 600 s at the end of production depending on the critical process parameters (CPPs), except for fluctuations in the initial process. These results indicate that tableting granules with various pharmaceutical properties could be obtained continuously depending on CQAs, such as the rate of water addition. Additionally, changes in CQAs could be continuously monitored by the NIR/PLSR method. Furthermore, CGD granules with various characteristic CQAs can be continuously manufactured by controlling CPPs, such as agitation blades and tube rotation rates in the agitating granulation process and drying air flow rate in the drying process under NIR spectroscopy.

Synergistic impact mechanism of particle size and morphology in superalloy powders for additive manufacturing

The particle size and morphology of superalloy powders are crucial parameters that significantly influence the performance of additive manufacturing (AM) processes. This study investigates the effects of atomization pressure on these characteristics through a combination of computational fluid dynamics (CFD) simulations and vacuum induction melting gas atomization (VIGA) experiments. The CFD simulations revealed that increasing the atomization pressure from 2.0 MPa to 3.5 MPa resulted in a rise in maximum gas velocity from 526 m/s to 537 m/s and a reduction in median particle size (D50) from 60.9 μm to 37.5 μm. Subsequent experiments demonstrated a decrease in D50 from 52.9 μm to 35.6 μm, and sphericity from 0.9432 to 0.9377, as pressure increased. The particle size results of the atomization experiments and numerical simulations show strong consistency, validating the accuracy of the numerical simulation results. The volume of hollow particles also increased slightly in specific size fractions. These results suggest that higher atomization pressures produce finer powders with lower sphericity, but also promote particle adhesion, reducing the overall refinement effect. This study provides insights into optimizing atomization conditions for the precise control of superalloy powders in AM.

Continuous self-circulating up-flow granular sludge fluidized bed process treating low-strength real municipal wastewater at high hydraulic loads

Conditions conducive to aerobic granular sludge (AGS) growth and maintenance are very difficult to realize in continuous-flow biological treatment processes. This study conducted a continuous-flow self-circulating up-flow granular sludge fluidized bed (Zier process) treating real urban wastewater approximately one year. The substantial self-circulating multiple times (RSCMT, 8–15 times) and up-flow velocity (8–15 m/h) generated by aeration, the only power equipment in Zier process, facilitated pollutant removal, particle granulation and stabilization. With hydraulic retention time of 5 h, RSCMT of 9.3–14.4 times and chemical oxygen demand (COD)/total nitrogen (TN) ratio of 5.9 ± 1.0, the effluent COD, ammonia nitrogen and TN were 28.6 ± 7.7, 1.1 ± 1.2, and 13.3 ± 1.7 mg/L, respectively. The median particle size was 150–250 μm and effluent suspended solids concentration was 33.4 ± 14.5 mg/L. It is unnecessary to set up sludge reflux which simplifies the subsequent mud-water separation facilities. The Zier process provides a new process structure for implementation of continuous-flow AGS process.

Micronization of wholewheat flour increases iron bioavailability from hydrothermally processed wheat flour dough

Cereal products contribute significantly to dietary intake of essential minerals. In wheat, iron and zinc are stored in specific grain structures including the aleurone, scutellum and embryo. Wheat cell walls are resistant to digestion in the human gastrointestinal tract and therefore this study investigated the hypothesis that physical disruption of the cell walls would increase the bioaccessibility and bioavailability of iron and zinc from wheat-based foods. Flour was micronized using a combination of roller milling and a micro-mill and this reduced median particle size by two-thirds. Hydrothermally processed wheat flour doughs were subjected to in vitro digestion to determine mineral bioaccessibility. Mineral bioavailability from food digests was measured using human intestinal Caco-2 cells. Iron (but not zinc) bioavailability from wheat foods made using the micronized flour (2.5 ± 0.5 nmol/mg cell protein) was increased significantly compared with foods produced from standard milled flour (1.3 ± 0.1 nmol/mg cell protein; P = 0.031). Micronization of wheat flour has the potential to increase the absorption of the endogenous iron present in cereal foods and this might have health benefits for population groups with poor iron status.

Proteomic Characterization of Corneal Epithelial and Stromal Cell-Derived Extracellular Vesicles.

Communication between the different layers of the cornea (epithelium and stroma) is a complex, yet crucial element in the corneal healing process. Upon corneal injury, it has been reported that the bi-directional cross talk between the epithelium and stroma via the vesicular secretome, namely, extracellular vesicles (EVs), can lead to accelerated wound closure upon injury. However, the distinct protein markers of EVs derived from human corneal epithelial (HCE) cells, keratocytes (HCKs), fibroblasts (HCFs), and myofibroblasts (HCMs) remain poorly understood. All EVs were enriched for CD81 and showed increased expression levels of ITGAV and FN1 in HCM-EVs compared to HCE- and HCF-EVs. All EVs were negative for GM130 and showed minimal differences in biophysical properties (particle concentration, median particle size, and zeta potential). At the proteomic level, we show that HCM-EVs are enriched with proteins associated with fibrosis pathways, such as COL6A1, COL6A2, MMP1, MMP2, TIMP1, and TIMP2, compared to HCE-, HCK-, and HCF-EVs. Interestingly, HCE-EVs express proteins involved with the EIF-2 signaling pathway (stress-induced signals to regulate mRNA translation), such as RPS21, RALB, EIF3H, RALA, and others, compared to HCK-, HCF-, and HCM-EVs. In this study, we isolated EVs from cell-conditioned media from HCE, HCKs, HCFs, and HCMs and characterized their biophysical and protein composition by Western blot, nanoparticle tracking analysis, and proteomics. This study supports the view that EVs from the corneal epithelium and stroma have a distinct molecular composition and may provide novel protein markers to distinguish the difference between HCE-, HCK-, HCF-, and HCM-EVs.

Innovative Proniosomal Formulation of Cilnidipine, Optimization and InDepth Characterization.

This study aims to enhance the solubility and bioavailability of cilnidipine as a dual L/N-type calcium channel blocker for hypertension using proniosomes. Proniosomes are dry powders that turn into niosomes when they come into contact with water, improving drug encapsulation and stability. Different concentrations of Span-60, cholesterol, and sorbitol were tested in the Box-Behnken design. The entrapment efficiency, particle size, zeta potential, thermal characteristics, crystalline structure and in-vitro drug release were evaluated for 17 formulations. Entrance effectivity was highest in F3 at 71.83%, while a controlled released rate of over 85.28% was observed within 12 hours. The median particle size showed a moderate stability of -11.2 mV with zeta potentials indicating this fact (902.7 nm). When, cilnidipine was inserted into proniosome systems, considerable changes occurred both thermally and crystallinity-wise according to DSC as well as XRD measurements were taken during an experiment where various mathematical models showed first-order kinetics dominated among other processes involved in drug release along Higuchi’s Equation.

Investigations on the dustiness of binary acetaminophen - lactose monohydrate powder blends

In this study, binary powder blends of acetaminophen (ACAM) and α-lactose monohydrate (LM) at different mixing ratios, with fine, medium-size, and coarse particles are investigated with a new two-chamber setup (TCS) to assess dustiness. The TCS consists of an emission and a detection chamber, allowing plain diffusive or convective particle transport. The aim is to compare the diffusive transport of ACAM with binary blends of ACAM and LM at different particle sizes and similar apparent density. Fine ACAM exhibits significantly higher dust emissions compared to medium and coarse ACAM. With increasing LM portion in the blends, ACAM dust emissions decrease. The blend of fine ACAM and coarse LM shows the highest dust emission, while the blend of coarse ACAM and fine LM reveals the lowest emissions. The TCS offers precise, reproducible measurements with good repeatability, making it beneficial for laboratory and industrial applications, even with small powder quantities.

Silica Nanoparticles Decorated with Ceria Quantum Dots Modulate Intra- and Extracellular Reactive Oxygen Species Formation and Selectively Reduce Human A375 Melanoma Cell Proliferation.

Nanomaterials show great promise for cancer treatment. Nonetheless, most nanomaterials lack selectivity for cancer cells, damaging healthy ones. Cerium dioxide (ceria, CeO2) nanoparticles have been shown to exert selective toxicity toward cancer cells due to the redox modulating properties they display as their size decreases. However, these particles suffer from poor suspension stability. The efficacy of CeO2 nanoparticles for cancer treatment is hampered by their innate high surface energy, which leads to particle agglomeration and, consequently, reactivity loss. This effect increases as particle size decreases; as such, quantum dots (QDs) suffer most from this phenomenon. In this study, it is proposed that silicon dioxide (silica, SiO2) nanoparticles can provide an inert platform for surface encrusted CeO2 QDs and that the resulting nanocomposite (hereafter QDCeO2/SiO2) not only will exhibit negligible agglomeration compared with CeO2 alone but also will improve the modulation of reactive oxygen species (ROS) leading to selective reduction of human A375 melanoma cell proliferation. The SiO2 nanoparticles had a bimodal size distribution with median particle size of 66 and 168 nm, while the CeO2 quantum dots encrusted on their surface had a size of 3.2 nm. An elevated Ce3+/Ce4+ ratio led to the QDCeO2/SiO2 nanocomposite displaying synergistic superoxide dismutase- and catalase-like activity, favoring the accumulation of ROS at pH 6.5 which translated into QDCeO2/SiO2 exerting selective oxidative stress in, and toward, the melanoma cells. Treatment with 50 μg mL-1 QDCeO2/SiO2 significantly reduced cell proliferation by 27% compared to untreated control cells in the colony formation assay. Treatment with either SiO2 or CeO2 alone did not affect the cell proliferation. These results highlight the benefit of dispersing CeO2 QDs on the surface of core nanoparticles and the resulting enhancement of selective redox reactivity and proliferation arrest when compared to CeO2 nanoparticles alone. Furthermore, the method employed here to encrust CeO2 QDs could lead to the facile synthesis of new nanocomposites with enhanced control of ROS activity, not only for in vitro studies using other cancer cell lines of interest but also in animal models and perhaps leading to clinical trials in melanoma patients.

Size-modulated Pt nanoparticles for low-temperature plasmon-enhanced hydrogen production from aqueous phase reforming of methanol

Al2O3 supported Pt nanoparticles photocatalyst enables efficient hydrogen production (115.2 μmol min−1 gcat−1) through aqueous phase reforming of methanol (APRM) reaction under light irradiation at low temperatures of 150 °C, which is 6 times higher than that of APRM reaction conducted in the dark. We demonstrate that the particle size of Pt nanoparticles greatly affected the light absorption ability, which is of great importance for light utilization of the photocatalyst. The medium particle size of Pt nanoparticles enables the lower electron density states, which is benefit for the dehydrogenation of methanol and the sequential water–gas shift (WGS) reaction and eventually promoted the photocatalytic performance for hydrogen production.

Estimating metal mass flowrate in gas-atomization for metal powder production

The gas-to-metal ratio (GMR) is considered an important parameter in the gas-atomization process for producing metal powders. Consequently, correlations for estimating the mass median particle size (d50) of powders use GMR as the main parameter. In an industrial setup, it is not easy to measure the melt flowrate to ascertain the GMR. Hence, in this study, we develop a theoretical approach to estimate the melt flowrate and measure it in a pilot setup. Both our theoretical and computational fluid dynamics approaches are in good agreement with the measurements. We then conduct a parametric study to elaborate the effect of certain parameters on the melt flowrate. We believe that the theoretical approach presented here will help to quickly estimate the powder size (d50) expected from a gas-atomization system. This will help to correctly choose geometric and operating parameters to reduce the spread in powder size distribution in an actual application.

Characteristics of hollow micron zero valent iron and its transport properties in groundwater: Effect of key engineering parameters and retention mechanism

In this study, a hollow micron zero-valent iron (H-mZVI) was synthesized, and its transport and retention property in saturated porous media was determined via a series of column experiments. Furthermore, the maximum migration distance (Lmax) and sedimentation rate coefficient (Kdep) models of H-mZVI in saturated porous media were established using statistical methods. The results revealed a distinct hollow structure in H-mZVI, with a density of 1.03±0.03 g/cm3, significantly lower than solid micron zero-valent iron (4.57±0.15 g/cm3). FTIR and XRD analyses indicated no formation of new functional groups on H-mZVI's surface, with iron being the main component. The column experiment demonstrated that the Lmax of H-mZVI in saturated porous media was 4.15 times that of solid micron zero-valent iron (mZVI) under the same conditions. The prediction model of Lmax aligned with the linear model, where Lmax correlated positively with particle size, injection velocity, and H-mZVI concentration, but inversely with ionic strength. Medium particle size and injection velocity were the main engineering parameters to control H-mZVI. The prediction model of Kdep accorded with the quadratic model, and an interaction was observed between medium particle size and injection velocity, which jointly affected the deposition rate of H-mZVI. Moreover, the single particle capture coefficient (η0) was hereby calculated and analyzed using the T-E theory. Interception primarily governed the precipitation of H-mZVI in saturated porous media, with gravity sedimentation contributing minimally to η0.

Effect of precursor particle size on the microstructure and Na storage performance of semi-coke derived carbon

The microstructure of carbon-based materials exerts a decisive influence on their Na storage performance. Furthermore, its evolution process may be influenced by the size of precursor particles during the pyrolysis preparation process. In this work, semi-coke has been used as the precursor, and its particle size (median particle sizes of 3, 7, 11, 15, and 19 μm) is investigated for its impact on the microstructure and Na storage performance of the resulting carbon materials (SDC-X, X = 3, 7, 11, 15, or 19). As the size of semi-coke increases from 3 μm to 19 μm, the highly-disordered carbon content of SDC-X decreases from 41.27 % to 30.94 %, while the content of pseudo-graphitic carbon associated with plateau capacity remains nearly constant. When SDC-X are employed as anodes for sodium-ion batteries, the initial coulombic efficiency (ICE) rose from 77.4 % to 82.3 % with the increase of size, primarily due to the increase in the ICE of slope region. However, despite SDC-19 having the highest ICE, its reversible capacity, rate, and cycle performance are inferior compared with the others due to its higher order degree and larger particle size. Therefore, carbon-based materials used as anodes for SIBs require a trade-off between particle size and the electrochemical performance.

Innovative Metal Powder Production Using CFD with Convergent-Divergent Nozzles in Wire Arc Atomization

This study aims to enhance the production of metal powders using a novel approach that integrates computational fluid dynamics (CFD) with convergent-divergent (C-D) nozzles in wire arc spraying atomization (WASA). The primary objective is to investigate the influence of nozzle design on particle size distribution and production efficiency. Utilizing the ANSYS CFD Fluent program, simulations were conducted to analyze the effects of various parameters, including throat diameter and divergent angles, on gas dynamics and metal droplet behavior. The findings reveal that C-D nozzles facilitate the acceleration of gas flow to supersonic speeds, significantly improving the shear force acting on the molten metal, thereby promoting the fragmentation of droplets into smaller particles. Notably, the optimized nozzle configuration achieved a median particle size (D50) of 44.42 µm, suitable for additive manufacturing applications. The novelty of this work lies in its comprehensive simulation framework that allows for rapid virtual testing, potentially leading to significant improvements in the efficiency and quality of metal powder production processes. This research addresses critical gaps in the existing literature and provides a robust foundation for future studies in the field of metal powder manufacturing. Doi: 10.28991/HIJ-2024-05-03-02 Full Text: PDF

The effects of processing parameters on the shape of particle size distribution and grinding rate in a stirred mill

The study of particle size distribution (PSD) of materials is a crucial aspect of mineral processing. It not only determines the appropriate beneficiation process and equipment but also has a significant impact on the grade and recovery of concentrate. This study utilizes a pin-stirred mill for the wet fine grinding of limonite to examine four different widths of PSD functions and compares their quantitative descriptions of the PSD. Skewness is a parameter introduced to quantitatively describe the asymmetry of the PSD. This study aims to investigate the effect of the stirrer speed, the density and the size of the grinding media on the shape of the PSD and on the grinding rate. The results show that a lower stirrer speed and a lower density of the grinding media result in a narrower and a more symmetrical PSD of the grinding products. Moreover, the time-dependent approach succeeds in simulating and proving the evolution behavior of the median particle size. It was found that the optimum mixing ratio of the grinding media can effectively adjust the shape of the PSD and improve the grinding efficiency.