Powder Diameter Research Articles

Three-Dimensional Numerical Simulation of High-Speed Shear Crushing of High-Density Fluid

Plasma atomization is a technology that can produce high sphericity, small particle diameters, and high-purity copper powder, which is of great significance for the development of metal additive manufacturing. At present, although plasma atomization can realize the industrial preparation of spherical copper powder, there are still some problems, such as unclear understanding of the atomization process and a lack of theoretical support for powder quality control. This leads to the inability to predict the average particle diameter of powder in advance based on the actual atomization conditions and to optimize the process parameters, which seriously affects the further development of the plasma atomization process. We mainly studied the non-stationary simulation of a DC argon plasma torch. The purpose of this paper was to study the specific influence law of the average particle diameter of the powder in the process of plasma atomization by means of numerical simulation and experimental observation. The aim was to establish the mapping relationship between the atomization condition and the average particle diameter of the powder and realize the controllable preparation of the plasma atomized powder. At the same time, we used industrial-grade plasma atomization equipment to carry out pulverizing experiments to verify the plasma atomization theory and the powder average particle diameter control scheme proposed in this paper, thus proving the reliability of this study.

Complexation mechanism and adsorption modes of Cu (II) ions by wool keratin powder

The excessive presence of Cu (II) ions in wastewater has led to various health problems. Using wool keratin powder adsorbent, the adsorption of Cu (II) ions in wastewater was explored. The adsorption mechanism and efficiency of keratin powder towards Cu (II) ions were characterized by infrared spectroscopy, x-ray diffraction and scanning electron microscopy. The results indicate that the particle size of keratin powder has a significant impact on its adsorption performances. Keratin powder with smaller particle size has more adsorption sites, larger specific surface area, higher porosity and more effective adsorption capacity. After adsorption of Cu (II), the average diameter of keratin powder increased by 11.48 μm. The adsorption capacity reached 58.95 mg g−1, and the adsorption efficiency reached 99.52% after 12 h of contact time. The research results not only provide an effective solution for Cu (II) ion pollution in wastewater, but also explore the resource utilization of waste wool.

Free radical-initiated direct ink writing of liquid polycarbosilane slurry and its conversion into SiC ceramic parts with low shrinkage

Additive manufacturing technology is being developed for manufacturing SiC ceramic parts with designed shape and microstructure. In this study, direct ink writing (DIW) was adopted to print SiC ceramic parts. To avoid incorporating volatile organic solvents or water, a SiC ceramic precursor liquid polycarbosilane (LPCS) was used as the binder of SiC powder and the rheological adjustment additive. The content of LPCS with the content and diameter of SiC powder were optimized to improve the fluidity of slurry, increase its ceramic yield and reduce its shrinkage during pyrolysis. According to the results of rheological analysis and shrinkage during pyrolysis, 78 wt% SiC powders composed of 40 nm SiC powder and 5 μm SiC powder in a ratio of 1:6 was appropriate. For achieving rapid solidification rate of the slurry at low temperature, a free‐radical initiator which can trigger the crosslinking of allyl group on LPCS was incorporated. According to the results of rheology, DSC and FT-IR, the preferred platform temperature for fast curing of DIW slurry was 150 °C. As the slurry accumulated layer by layer on heating platform, the cured green bodies were successfully prepared. After pyrolysis to 1200 °C, SiC ceramic parts were obtained with only 4.43% linear shrinkage associated with the precursor-to-ceramic conversion. Because the shrinkage was limited, no obvious deformation or crack was found.

The influence of ball milling conditions on the powder characteristics and sintering densification of Mo[sbnd]Cu alloy

Mechanical alloying was utilized to produce Mo-30Cu(wt%) composite powder. The effects of milling conditions on the powder characteristics and sintering densification were investigated. The morphological evolution during the mechanical alloying process can be categorized into four stages: 1-individual Mo and Cu particles, 2-coexistence of Mo particles and blocky MoCu composite particles, 3-coarse irregular composite particles, and 4-refined near-spherical composite particles or lamellar MoCu composite particles, depending on whether process control agent (PCA) is added. The mechanical alloying degree of the MoCu composite powder was deepened gradually from stage 1 to 4, which is influenced by the ball milling parameters. As the milling speed and milling time increase, the lattice strain and the alloying degree of the MoCu composite powders increase while the grain size of molybdenum particles decreases, which is conducive to accelerating the sintering density. Among these ball milling parameters, an elevated milling speed notably accelerates the mechanical alloying process and the sintering density. Under the milling speed of 600 r/min, ball to powder ratio (BPR) of 10:1, and milling time of 4 h, the grain size, lattice strain, and average particle diameter of the composite powder were measured to be 48.4 nm, 0.247 %, and 21.04 μm, respectively, with the particle morphology being nearly spherical. The sintered density of the MoCu composite reached 98.1 %, larger than the other composites.

Rheological Behavior of SiO2 Ceramic Slurry in Stereolithography and Its Prediction Model Based on POA-DELM.

Ceramic slurry is the raw material used in stereolithography, and its performance determines the printing quality. Rheological behavior, one of the most important physical factors in stereolithography, is critical in ceramic printing, significantly affecting the flow, spreading, and printing processes. The rheological behavior of SiO2 slurry used in stereolithography technology is investigated in the current research using different powder diameters and temperatures. The results present the apparent non-Newtonian behavior. The yielding characteristics occur in all cases. For single-powder cases, the viscosity decreases when the powder diameter is increased. When the nano-sized and micro-sized powders are mixed in different proportions, a more significant proportion of micron-sized powders will decrease the viscosity. With an increase in the nano-sized powders, the slurry exhibits the shear thinning behavior; otherwise, the shear thickening behavior is observed. Thus, the prediction model is built based on the use of the pelican optimization algorithm-deep extreme learning machine (POA-DELM), and the model in then compared with the fitted and traditional models to validate the effectiveness of the method. A more accurate viscosity prediction model will contribute to better fluid dynamic simulation in future work.

The investigation on the ceiling of inlet velocity regarding to fine particle separation in a cyclone

The maximum efficiency inlet velocity (MEIV) serves as the upper limit for the inlet velocity that defines the separation efficiency in cyclone design and operation. In this paper, a combination of numerical and experimental methods is used to study MEIV. Experimental findings indicate that the MEIV is 22 m/s for a median particle size of 12.39 μm (coarse powder) and 35 m/s for a median particle size of 2.93 μm (fine powder). Meanwhile, the amount of escaped fine powder is reduced by 25% compared to that at an inlet velocity of 22 m/s. Computational fluid dynamics (CFD) simulations have shown that the inconsistency between tangential and axial velocity growth of inlet velocity with respect to various powder diameters can explain this phenomenon. As the inlet velocity increases, the peak axial velocity exhibits a stepwise increase. When the peak value remains constant, the peak width increases. This phenomenon is called stagnation of the axial velocity. During the axial velocity stagnation step, the residence time of back-mixed particles vary. In contrast, the tangential velocity increases linearly with the inlet velocity, resulting in an enhanced secondary separation of the inner vortex. Both factors hinder the escape of fine particles due to entrainment by a rapid upward airflow. The inlet velocity range corresponding to the stagnation step of the fine powder is larger than that of the coarse powder. Therefore, the MEIV of the fine powder is higher.

Potential of Powder Rheology for Detecting Unforeseen Cross-Contamination of Foreign Active Pharmaceutical Ingredients.

Unexpected cross-contamination by foreign components during the manufacturing and quality control of pharmaceutical products poses a serious threat to the stable supply of drugs and the safety of customers. In Japan, in 2020, a mix-up containing a sleeping drug went undetected by liquid chromatography during the final quality test because the test focused only on the main active pharmaceutical ingredient (API) and known impurities. In this study, we assessed the ability of a powder rheometer to analyze powder characteristics in detail to determine whether it can detect the influence of foreign APIs on powder flow. Aspirin, which was used as the host API, was combined with the guest APIs (acetaminophen from two manufacturers and albumin tannate) and subsequently subjected to shear and stability tests. The influence of known lubricants (magnesium stearate and leucine) on powder flow was also evaluated for standardized comparison. Using microscopic morphological analysis, the surface of the powder was observed to confirm physical interactions between the host and guest APIs. In most cases, the guest APIs were statistically detected due to characteristics such as their powder diameter, pre-milling, and cohesion properties. Furthermore, we evaluated the flowability of a formulation incorporating guest APIs for direct compression method along with additives such as microcrystalline cellulose, potato starch, and lactose. Even in the presence of several additives, the influence of the added guest APIs was successfully detected. In conclusion, powder rheometry is a promising method for ensuring stable product quality and reducing the risk of unforeseen cross-contamination by foreign APIs.

Mechanochemical Recycling of Flexible Polyurethane Foam Scraps for Quantitative Replacement of Polyol Using Wedge-Block-Reinforced Extruder.

Recycling flexible polyurethane foam (F-PUF) scraps is difficult due to the material's high cross-linking structure. In this work, a wedge-block-reinforced extruder with a considerable enhanced shear extrusion and stretching area between the rotating screw and the stationary wedge blocks was utilized to recycle F-PUF scraps into powder containing surface-active hydroxyl groups. The powder was then utilized for the quantitative replacement of polyol in the foaming process. Characterizations showed that the continuous shear extrusion and stretching during the extrusion process reduced the volume mean diameter (VMD) of the F-PUF powder obtained by extruding it three times at room temperature to reach 54 μm. The -OH number (OHN) of the powder prepared by extruding it three times reached 19.51 mgKOH/g due to the mechanochemical effect of the powdering method. The F-PUF containing recycled powder used to quantitively replace 10 wt.% polyol was similar in microstructure and chemical structure to the original F-PUF, with a compression set of 2%, indentation load deflection of 21.3 lbf, resilience of 43.4%, air permeability of 815.7 L/m2·s, tensile strength of 73.0 Kpa, and tear strength of 2.3 N/cm, indicating that the recycling method has potential for industrial applications.

Influence of Excitation Parameters on Finishing Characteristics in Magnetorheological Finishing for 6063 Aluminum Alloy.

The present work is aimed at studying the effects of the magnetorheological finishing process, using a low-frequency alternating magnetic field, on the finishing performance of 6063 aluminum alloy. The study investigates the influence of key excitation parameters such as current, frequency, excitation gap, and iron powder diameter on the material removal and surface roughness (Ra) of the finished workpiece by experiments. This study employs a single-factor experimental method, and the finish surface is analyzed by a Zigo non-contact white light interferometer. The magnetic field strength in the processing area increases with the increase in the excitation current and decreases with the increase in the excitation gap. When the current frequency is set to 1 Hz, the circulation and renewal of abrasives in the magnetic cluster is most sufficient, resulting in the optimal surface roughness value for the workpiece. According to the experimental results of the excitation parameters, more suitable process parameters were selected for a two-stage finishing experiment. The surface roughness of 6063 aluminum alloy was improved from 285 nm to 3.54 nm. Experimental results highlighted that the magnetorheological finishing using a low-frequency alternating magnetic field is a potential technique for obtaining nano-scale finishing of the 6063 aluminum alloy.

Simulation of storage of cold energy considering unsteady conduction mechanism in mathematical model

To enhance system productivity, fins were incorporated into the container, and PCM (phase change material) infused with alumina nanoparticles was introduced. Mathematical modeling was employed to evaluate the current problem, with a specific focus on utilizing water as the PCM for achieving the fastest solidification process. The integration of fins, PCM, and nano-powders introduces a novel dimension to the research, providing unique insights into enhancing solidification processes. The surrounding cold walls of the container play a crucial role in solidification, primarily through conduction. The low speed of H2O allows its neglect in simulation. The developed mathematical model for this work comprises two equations. While considering larger powder sizes improves particle interaction, the negative impact of sedimentation diminishes conductivity. The addition of nanoparticles results in a 41.34 % enhancement in the solidification rate. Furthermore, altering the powder diameter from thirty to 40 nm reduces the completion time about 19.98 %, whereas an increase from 40 to 50 nm elevates it by about 49.37 %.

Development and experimental evaluation of surface enhancement methods for laser powder directed energy deposition microchannels

ABSTRACT This research evaluates Laser Powder Directed Energy Deposition (LP-DED) for producing fine feature internal microchannels. This study is focused on enhancing and characterising the surfaces of microchannels produced using techniques such as abrasive flow machining, chemical milling, chemical mechanical polishing, electrochemical machining, and thermal energy method to modify internal surfaces of microchannels made from NASA HR-1 Fe-Ni-Cr alloy. Flow testing for discharge coefficient measurement is conducted on processed microchannel samples, followed by characterisation through optical microscopy, Scanning Electron Microscopy (SEM), and Computed Tomography. Findings reveal variations in surfaces due to powder adherence, melt pool undulations, and polishing mechanisms. The study emphasises the significance of removing material equivalent to the mean powder diameter to reduce surface roughness and impact the discharge coefficient. The research proposes a ratio for planarising roughness and waviness peak height and density, offering insights for tailored surface adjustments in specific applications requiring reduced flow resistance. Highlights Internal microchannels with thin-walls were fabricated using the laser powder directed energy deposition process. Various surface enhancements and polishing processes were developed to modify the surface texture of the LP-DED channels. Flow testing was conducted to determine the discharge coefficient. Post-test characterisation was completed to obtain cross sectional area, perimeter, surface texture, and general surface condition to analyse results. Ratio of roughness and waviness peak and density (Spk/Spd and Wp/WPc) is proposed as a relevant surface characterisation parameter. Tailored surface modifications for specific end-use applications.

Bioactive dry extract production from Hymenaea courbaril L. bark via spouted bed drying

AbstractThe work aims to develop and optimize a powdered phytopharmaceutical product from the stem bark of Hymenaea courbaril L. (jatobá) by the spouted bed drying. The study commenced with the extraction of bioactive compounds present in the plant raw material by dynamic maceration using ethanol/water 70% (v/v) at a temperature of 50°C for 60 min, for the ratio stem bark: solvent mass of 1:10 (w/w). The extract quality was assessed by quantifying chemical markers via spectrophotometry (total polyphenols and tannins) and through antioxidant activity by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assay. The extractive solution was concentrated, added with drying adjuvant, and submitted to spouted bed drying. Product quality was evaluated by moisture content (Xp), water activity (aW), powder diameter, total polyphenols, and tannins content (PT and TT), and antioxidant activity, expressed as the extract concentration needed to reduce 50% of the DDPH radical (IC50). Spouted bed drying performance was evaluated through the drying yield (REC), product accumulation (Ac), and thermal efficiency (η). The optimal processing conditions were: inlet gas temperature, Tgi: 150°C, the ratio of the mass feed flow rate of the concentrated extract to the evaporation capacity of the dryer, Ws/Wmax: 45%, and the drying gas flow rate relative to minimum spouting, Q/Qms: 1.85. Under these conditions, it is predicted to obtain a dried extract with Xp = 4.9% w/w, PT = 26.0% w/w, REC = 77.7% w/w, η = 44.3%, and Ac = 10% w/w, with adequate values of aW, TT, and high antioxidant activity.

Study on sedimentation stability of silicone oil-based magnetorheological fluids with fumed silica as additive

In order to study the sedimentation stability of silicone oil-based magnetorheological fluids with fumed silica as additive, magnetorheological fluids with different mass fractions of fumed silica, particle sizes of carbonyl iron powder and viscosities of silicone oil were prepared. The sedimentation rate of magnetorheological fluids was calculated by observation method, and the zero-field viscosity of magnetorheological fluids was measured by viscometer. The results show that the sedimentation rate and viscosity of magnetorheological fluids increase gradually with the increase of the mass fraction of fumed silica. The mass fraction of fumed silica should not be constant for magnetorheological fluids, but should be determined according to the content of silicone oil in magnetorheological fluids. With the increase of average diameter of carbonyl iron powder, the sedimentation stability of magnetorheological fluids becomes worse. With the increase of viscosity of silicone oil, the sedimentation stability of magnetorheological fluids does not increase significantly. However, the high viscosity of silicone oil will result in wall hanging phenomenon, and increase the start-up difficulty of magnetorheological device. With 2.5 wt% of fumed silica for silicone oil, the magnetorheological fluids has good sedimentation stability and suitable zero-field viscosity.

Efficacy of dispersing nano-powders on rate of cold storage during solidification considering transient conduction

This study conducts a simulation of the freezing through a container featuring finned sinusoidal geometry. The application of the Galerkin method effectively captures the intricate dynamics of unsteady processes, showcasing a significant enhancement by introducing nanoparticles to augment the system's thermal conductivity—an essential element for optimizing conduction efficiency. The numerical approach underscores the importance of employing an adaptive grid in unsteady scenarios, tailoring the grid based on the solid front's position due to heightened scalar gradients. Various powder diameters (dp) and fractions (φ) are systematically investigated, elucidating their distinct impacts on process duration. Results reveal that an initial increase in dp causes to a decrement in period by 19.93%, followed by a subsequent rise of 49.06%, specifically for scenarios with a 0.04 nanoparticle concentration. The incorporation of nanoparticles yields a noteworthy 41.13% decrease in solidification time when optimal powder sizes are utilized. In contrast, the solidification time without additives is 278.95s, reduced to 164.19s with the introduction of optimally sized powders.

Optimization of Technological Parameters for Cold Spraying Using the Response Surface Method

Cold spray technology can obtain coatings in a solid state, which is suitable for deposition protective and restorative coatings. Currently, most of the research in cold spraying is based on a single-factor analysis to explore the law. However, the interaction effect of multiple factors is more scientific. In this study, the response surface method (RSM) was used to optimize the technological parameters of cold spraying. A multi-factor and multi-level quadratic regression model was established for gas temperature, pressure, and particle diameter of outlet velocity, and the process parameters were optimized. The results showed that the gas temperature, particle diameter, and gas pressure have significant effects under a single factor. Also, under the interaction of multiple factors, the P-value of the quadratic regression model was less than 1·10–4, and the R2 of the model was 0.9626, indicating that the curve fitting is good and the model has good credibility. The interaction between gas pressure and gas temperature is significant, while the interaction between gas temperature and powder diameter, gas pressure, and powder diameter are insignificant. Moreover, the parameter error between the optimized parameters through response surface analysis and the actual numerical simulation is 0.76 %, indicating high accuracy.

Insecticidal efficacy of two candidate diatomaceous earth powders against the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

The insecticidal efficacy of amorphous silica powders 1 and 2 with different physical and elemental compositions were evaluated against the lesser grain borer, Rhyzopertha dominica (F.) using concrete arenas. The particle diameter and shape characterization (circularity, elongation, aspect ratio, and convexity) of the two silica powders were performed using Morphology G3 instrument. The particle diameter and shape characteristics (circularity and elongation) of silica powder 1 were significantly higher compared to silica powder 2. However, these factors did not influence the efficacy of silica powders against R. dominica. Silica powder 2 showed higher mortality at lower application rates and shorter exposure times compared to silica powder 1. The efficacy of silica powder 2 was due to its higher oil adsorption capability, low pH, and high silicon dioxide content compared to silica powder 1. Adult progeny production was inversely related to the powder application rate. Silica powder 2 was more effective on R. dominica in inhibiting adult progeny production at 0.25 g/m2. Lower percentages of insect-damaged kernels and grain weight loss were observed at lower application rates (0.10–0.20 g/m2) following exposure to silica powder 2 compared to silica powder 1, which required higher application rates (2.0–3.5 g/m2). Overall, silica powder 2 demonstrated superior efficacy against R. dominica in terms of mortality, progeny production, insect-damaged kernels, and grain weight loss.

Particle-scale analysis of thermophysical behaviors of coaxial gas swirling jets with binary-size particle mixture

Understanding the multi-physics coupling of coaxial-jet gas-particle swirling flow is crucial for practical applications. In this study, computational fluid dynamics coupled with the discrete element method is utilized to investigate the flow behavior of a coaxial jet composed of powder and coal within an annular pipe. The influence of particle diameter on particle-scale information is examined. When powder diameter is 450 μm, large particles display high Reynolds and Nusselt numbers, whereas small coal particles demonstrate elevated velocities and temperature. The variation in particle diameter affects momentum and energy exchanges at specific locations, but has a negligible impact on the radial velocity distribution and Nusselt number of powder particles. Specifically, increasing the particle diameter from 50 to 450 μm leads to a reduction in swirling velocity at the outlet of the annular pipe from 15.43 m/s to 9.57 m/s for binary mixtures, and from 18.49 m/s to 7.03 m/s for powders.

Dimensional Effects of Hybrid Bond Layers on CFRP Metallized by Ti Cold Spray

Hybrid bond layers (BLs) were designed, fabricated, and evaluated for cold spray metallization of CFRP. The bond layers consisted of metal mesh embedded in a polymer film adhesive co-cured to the CFRP. Efforts were devoted to identifying the critical opening ratio—i.e., the ratio of mesh opening size to powder diameter, for deposition of an adherent coating. Analysis of powder deposited at mesh openings show a transition from erosion (at a mesh opening ratio of 6.4) to mechanical interlocking and formation of a continuous coating with decreasing opening ratio. Selection of opening ratio yielded either (a) a grid of consolidated thin-walled deposits atop mesh wires separated by microchannel openings, or (b) densified coatings of cold-sprayed Ti. The effective opening ratio increased with increasing diameter ratio—i.e., the ratio of wire diameter to powder size, a consequence of eroded wire peripheries at shallow impact angles. These findings inform the design of future hybrid BLs, in concert with the selection of powder size, for cold spray metallization of CFRP.

Screening of Cyclodextrins in the Processing of Buserelin Dry Powders for Inhalation Prepared by Spray Freeze-Drying.

In this study, we prepared inhalable buserelin microparticles using the spray freeze-drying (SFD) method for pulmonary drug delivery. Raffinose as a cryoprotectant carrier was combined with two levels of five different cyclodextrins (CDs) and then processed by SFD. Dry powder diameters were evaluated by laser light scattering and morphology was determined by scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis were utilized for the determination of crystalline structures. The aerodynamic properties of the spray freeze-dried powders were evaluated by twin stage impinger (TSI) and the stability of prepared samples was assessed under normal and accelerated conditions. The prepared powders were mostly porous spheres and the size of microparticles ranged from 9.08 to 13.53 μm, which are suitable as spray-freeze dried particles. All formulations showed amorphous structure confirmed by DSC and XRD. The aerosolization performance of the formulation containing buserelin, raffinose and 5% beta-cyclodextrin (β-CD), was the highest and its fine particle fraction (FPF) was 69.38%. The more circular and separated structures were observed in higher concentrations of CDs, which were compatible with FPFs. The highest stability was obtained in the formulation containing hydroxypropyl beta-cyclodextrin (HP-β-16. CD) 5%. On the contrary, sulfobutylether beta-cyclodextrin (SBE-β-CD) 5% bearing particles showed the least stability. By adjusting the type and ratio of CDs in the presence of raffinose, the prepared formulations could effectively enhance the aerosolization and stability of buserelin. Therefore, they can be proposed as a suitable career for lung drug delivery.

Oxidative stability of physiologically functional oil microencapsulated by spray drying

Edible oils with physiological functions, such as fish oil and krill oil, which contain polyunsaturated fatty acids (PUFAs), are highly unstable to heat and oxygen. One of the methods for improving the shelf life of these oils is microencapsulation of the oils through spray drying. This mini-review describes the effects of the surface–oil ratio, oil location within the microcapsules, and oil-droplet diameter on the oxidative stability of functional oils in microcapsules prepared through spray drying. The surface–oil ratio, s, can be expressed through the ratio of the average oil-droplet diameter to the average powder diameter, E, by s = 1 − (1 − 2E)3. Additionally, the effects of oil-droplet size and storage temperature on the stability of the encapsulated oil were examined using squalene as a model functional oil. The activation energy E a of the squalene degradation rate constant of the Avrami equation can be correlated with the average oil-droplet diameter d e. The release behavior of the microencapsulated flavors is also discussed because spray drying is also used for the microencapsulation of flavors. The flavor release rate constant of the Avrami equation is related to the oxygen diffusion coefficient of the wall material.