Powder Particles Research Articles

Numerical Study of Powder Particle Flight Behavior during Gas Detonation Spraying Process

Numerical Study of Powder Particle Flight Behavior during Gas Detonation Spraying Process

WASTE EGGSHELL AND SAWDUST AS REINFORCEMENTS FOR SUSTAINABLE POLYESTER COMPOSITES: MECHANICAL CHARACTERIZATION AND ENVIRONMENTAL DURABILITY ASSESSMENT

This research endeavor undertakes an experimental investigation into the bending and tensile properties of polyester composites reinforced with waste eggshell powder and sawdust particles at 35 wt.%. Valorizing these waste materials as reinforcements contributes to sustainable practices, waste minimization, and environmental pollution mitigation. Composite samples were fabricated using hand lay-up and compression molding techniques. The effects of environmental exposure to water, acidic, and basic media immersion on the mechanical performance were evaluated to assess durability. Experimental characterization through tensile and three-point bending tests determined mechanical properties, stress-strain behavior, and failure mechanisms. Additionally, finite element analysis (FEA) simulations complemented the experiments by providing insights into stress distributions, deformations, and potential failure initiation sites within the composites under flexural loading. The computational models accurately captured the reinforcing effects of the waste materials and the degradation induced by environmental exposure, validating the experimental trends. Incorporating waste natural fibers significantly enhanced polyester's bending strength by 140% (sawdust) and 75% (eggshell), and tensile strength by 13% (sawdust) and 10% (eggshell). However, environmental exposure degraded properties to varying extents, with water immersion reducing tensile strength by 63% (sawdust) and 3% (eggshell), and flexural strength by 63% (sawdust) and 3% (eggshell). The acidic medium caused 58% (sawdust) and 23% (eggshell) reductions in tensile strength, and similar flexural strength degradations. Strikingly, the basic medium decreased eggshell composite tensile strength by 170% and flexural strength by 6%, while sawdust composite strengths declined by 44%.

Experimental and theoretical study of size-dependent phase evolution in NaCl-KCl alloys

In the present investigation, the formation of nanocrystalline bi-alkali halide (NaCl+KCl) obtained by combined low temperature (cryomilling) with room temperature (RT) milling was reported. The cryomilling, which is endowed with special ability to accelerated fracture and form free ionic salt crystals, is utilized for rapid refinement. This is followed by RT milling to form biphasic nanocrystallites. The bi-phase formation with the time of milling was characterized using a scanning electron microscope (SEM) and transmission electron microscope (TEM). The change in lattice parameter and introduction of micro-strain in the lattice (due to cold work and bi-phase formation) have been characterized using X-ray diffraction and deduce using theoretical calculations. The investigation reveals the influence of milling time on the shape and size of the crystallites along with formation of biphasic NaCl-KCl crystallites with inner core being NaCl surrounded by KCl crystals. The KCl powder particles get deposited on the surface of NaCl crystals to maintain the charge neutrality during ball milling. The shape of NaCl undergoes change from cuboid to cuboctahedron with the progression of milling time due to plastic deformation induced roughing. The temperature-dependent mechanical behaviour and associated mechanism of the milled NaCl-KCl system were discussed and supported by the thermodynamic modal. It is evident, NaCl-KCl is phase separating system, which accentuated at nanosized and hence, the formation of biphasic crystalline structure is observed during combined cryo and RT milling.

Differences in physicochemical properties and proteomics analysis of spray- and freeze-dried milk powders from bovine, goat, and horse sources

Milk powder, a nutrient-rich dairy product, lacks comprehensive information summarizing its specific properties when produced by spray- and freeze-dried technologies from different sources. Therefore, this study investigated the differences in physicochemical properties, microstructure, and proteome of spray- and freeze-dried milk powders from bovine, goat, and horse sources. The results revealed that spray-dried milk powder exhibited a smaller particle size, lower air content within the powder particles, inferior reconstitution properties, and lower lactose crystallinity compared with freeze-dried milk powder. Additionally, among the studied varieties, horse milk powder showed the lowest flowability but the most effective reconstitution properties. Proteomic analysis indicated that freeze-dried milk powder exhibited higher levels of immune-related proteins, including complement C3, C7, and complement factor B, and antimicrobial enzymes such as lysozyme and lactoperoxidase compared with spray-dried milk powder. Furthermore, specific milk powders contained more immune-related proteins such as serum amyloid A, myeloid antimicrobial peptide-28, polymeric immunoglobulin receptor, and mucin-1 compared with bovine milk powder. These findings contribute to a deeper understanding of the differences in the physical-chemical properties and potential biological functions of spray- and freeze-dried milk powders from various sources, which may help in further optimizing specific milk powder processing technologies.

Event-based high-resolution neutron image formation analysis using intensified CMOS cameras

We present a versatile optical setup for high-resolution neutron imaging with an adaptable field of view and magnification that can resolve individual neutron absorption events with an image intensifier and a CMOS camera. Its imaging performance is characterized by evaluating the resolution limits of the individual optical components and resulting design aspects are discussed. Neutron radiography measurements of a Siemens star pattern were performed in event mode acquisition comparing two common high-resolution neutron scintillators, crystalline Gadolinium Gallium Garnet (GGG) and powdered Gadolinium Oxysulfide (GOS). An analysis of the light signature caused by neutron absorption events is performed and some resulting issues for both GGG and GOS regarding optical system design are addressed. Both scintillators reach similar resolution (4–5 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upmu }$$\\end{document}m) in event mode acquisition despite different light emission characteristics. The findings suggest that, in the case of GOS, the resolution is limited by the size of the light clusters which in turn originate from the photon scattering at the boundaries of the powder particles comprising it, while with GGG the lower light conversion efficiency makes it challenging to collect enough photons to trigger sufficient signal amplification in the image intensifier. Overall, the proposed event-based evaluation of scintillators allows for quantifying and optimizing various design parameters, which is much more complex than adopting conventional methods based on integrated images.

Local adaptive insulation in amorphous powder cores with low core loss and high DC bias via ultrasonic rheomolding

Amorphous powder cores are promising components for next-generation power electronics. However, they present inherent challenges of internal air gaps and stresses during cold compaction, which significantly deteriorate soft magnetic properties. Here, we report the formation of a local adaptive insulation structure of biconcave lens in amorphous powder cores by ultrasonic rheomolding. Consequently, compared with conventional cold-compacted powder cores, the ultrasonic rheomolded powder cores offer significant simultaneous improvements in the permeability from 31.3–32.4 to 41.8–43.3 and the direct-current bias performance from 69.4–69.7% to 87.4–87.8% (7960 A/m), thereby overcoming the trade-off between permeability and direct-current bias performance. In particular, their core losses are as low as 13.73–15.45 kW/m3, approximately one twentieth of that of the cold-compacted powder cores (282.84–304.03 kW/m3) at a magnetic field of 100 mT and 100 kHz. The biconcave-lens insulation structure can effectively buffer the impact of high mechanical stress on the magnetization of magnetic powder particles, allowing for the ultrasonic rheomolded powder cores to maintain better magnetization efficiency and consequently resulting in excellent soft magnetic properties under the cooperative effect of very low internal stresses and low porosity. The ultrasonic rheomolded powder cores can be used as alternative core components in next generation miniaturized power electronics.

Ultrasonic and conventional fatigue behavior, strain rate sensitivity, and structural design methods for wrought and cold spray Al-6061

Cold spray is an additive manufacturing process that accelerates powder particles to supersonic speeds to create repairs and bulk depositions with fine-grained microstructures, high density, and good mechanical properties. Fatigue property measurement for these novel materials is critical for their use in safety-critical components, which can be accelerated with the use of ultrasonic fatigue testing. In this work, ultrasonic (20 kHz) and conventional (20 Hz) fatigue studies were conducted on as-sprayed bulk Al-6061 and conventional wrought Al-6061-T6. Complementary fatigue studies of surface preparation (surface finish and residual stress) and fatigue specimen geometry (round versus flat), as well as hole-drilling residual stress measurements, were undertaken to minimize the influence of these confounding variables. Cold spray Al-6061 exhibits fatigue frequency sensitivity, whereas the wrought material does not. Tensile testing at varied strain rates indicates that a portion of the fatigue frequency effect can be attributed to strain rate sensitivity. Fractographic studies show that crack initiation occurs from unbonded powder particles at the surface at high stress amplitude, and transitions sub-surface at lower stress amplitude. The results of these studies were used to create frequency-corrective models of S-N data and Kitagawa-Takahashi diagrams that can be used to design for fatigue crack initiation and growth resistance.

Surface chemistry characterization of AA2014 aluminum alloy powder through triboelectric charging

Traditional characterization techniques for powders primarily focus on bulk properties, often neglecting the critical role of surface chemistry variations that influence the performance in applications such as additive manufacturing. The method presented in this work addresses this gap by utilizing triboelectric charging concept to gain a comprehensive understanding of powder surface state under varying environmental conditions. In particular, the study investigates the detection of surface chemistry variations of AA2014 powder caused by an exposure to various relative humidity (RH) levels through a change in triboelectric charging behavior. The surface variations are analyzed in parallel with X-ray photoelectron spectroscopy (XPS). The findings reveal a direct correlation between elevated RH and increased hydroxide species content at the surface of the powder. The triboelectric charging experiments demonstrated a significant RH-dependent variations of charge accumulation, with higher humidity levels leading to reduced static charge buildup on the powder particles. The charge accumulation behavior in the powder was fitted with the compressed exponential relaxation model. The results showed that each surface chemical species exhibits a distinct correlation between charging rate and charge accumulation, confirming the method's effectivity to detect subtle variations in surface chemistry. The variations in the exponent of the fitted model were shown to be characteristics to the surface scale of the powder particles.

Investigation of Elaeocarpus ganitrus seed (EGs) powder as a sustainable composite biomaterial: Effects of particle size on the mechanical, frictional, and thermal properties for potential biomedical applications

This study explores the potential of Elaeocarpus ganitrus seed (EGs) powder as a sustainable composite biomaterial, focusing on its particle size effects on the mechanical, frictional, and thermal properties of composite materials for potential biomedical applications such as prosthetics and implants. Composite specimens were produced using the compression hot molding method, utilizing EG powder particles of varying sizes (120, 140, and 200-mesh sieving). The influence of EG powder particle size on key properties was systematically investigated. The findings reveal that reducing the particle size of EGs leads to a decrease in density and hardness of the composite, with the largest particle size (BP1) resulting in the highest density and hardness. Friction coefficient measurements indicated suitability for biomedical applications where surface interaction and wear resistance are critical, such as joint prosthetics. Thermal analysis showed that BP1 exhibited superior thermal stability, with a maximum decomposition temperature (Tmax) exceeding 375 °C. Differential scanning calorimetry identified significant differences in glass transition temperature (Tg) and crystallization temperature (Tc) across specimens. The composites demonstrated exceptional thermal performance, surpassing previous benchmarks for biomaterials in high-temperature environments. The mechanical and thermal characteristics of Specimen BP1—2.725 g/cm3 density, 74 Shore D hardness, 0.159 coefficient of friction, 93.3% total residual, 378.14 °C Tmax, 426.25 °C Tc, and 376.87 °C Tg—suggest its potential for biomedical applications requiring durability and thermal resilience, such as in orthopedic devices and tissue engineering scaffolds.

Recent Patents on Particle Wettability Measurement and Improvement

Background: As the coal mining industry becomes more mechanized, it leads to a large number of coal dust particles suspended in the air, polluting the surrounding environment, accompanied by an increase in fine-grained low-rank coal particles and a low recovery rate of a large amount of organic matter in the particles, wasting resources. Objective: The study of particle wettability can have an impact on spray dust reduction and particle flotation efficiency. By adjusting the hydrophilicity of coal powder particles, the generation of suspended coal dust can be effectively suppressed. By adding surfactants, the flotation separation efficiency of coal particles can be improved. Method: This article introduces the measurement method of particle wetting properties and methods to improve the wetting properties of particles, providing a reference for studying the wetting properties of particles Results: The measurement of particle wetting properties is more accurate, simple, and convenient. Improving the wetting properties of particles by adding additives has significant implications for later dust reduction and particle flotation. Conclusion: This thesis provides an important basis for studying the wettability of particles, modifying the wettability and hydrophilicity of particles, providing specific guidance for improving the wettability of particles for spray dust reduction and particle flotation, and greatly improving industrial production efficiency.

Cafestol and kahweol content in different specialty coffee brews: exploration by NMR analysis and evaluation of brewing parameters.

Cafestol and kahweol, two coffee diterpenes known for their health effects, were quantified in cups of Kenya specialty coffee prepared using eight different brewing methods: AeroPress, Chemex, Clever, V60, Moka, Ibrik, Pure Brew, and French press. High-resolution Nuclear Magnetic Resonance (NMR) spectroscopy was employed for this analysis, involving a straightforward sample preparation procedure with only an extraction step for lipid compounds. Statistical tools were utilized to examine the correlation between diterpene concentrations and each extraction feature, with a focus on the impact of brewing parameters. The results indicate that unfiltered brewing methods produce coffee with high concentrations of diterpenes, whereas paper-filtered methods result in significantly lower concentrations. The findings suggest that these compounds are present in the coffee cup as part of the suspended solids, and that filtration, pressurization, and coffee powder particle size are crucial parameters influencing their concentration.

Microstructure and mechanical performance of cold spray Cr coatings

Cold spray deposition has emerged as a promising method for applying protective coatings in the nuclear industry, particularly for enhancing the accident tolerance of fuel assemblies. In this process, helium gas is often used to propel solid powder particles towards the target substrate, however, nitrogen gas is also considered due to its significantly lower cost. In this study, we investigate the influence of nitrogen and helium gas as propellants on the properties and microstructure of pure chromium (Cr) coatings on zirconium (Zr) alloy cladding tubes. Employing Scanning Electron Microscopy (SEM) and electron and x-ray diffraction techniques (EBSD, XRD), we explore the structural characteristics of the coatings. Additionally, in-situ SEM tensile testing at room temperature, coupled with Digital Image Correlation (DIC), is utilized to assess the coating cracking behaviour. Our findings reveal distinct differences in coating morphology and residual stress between nitrogen and helium propelled Cr coatings. The nitrogen-propelled coating exhibits a more porous structure with smoother coating/substrate interfaces and lower compressive residual stress compared to the helium-propelled one. This results in earlier strain-induced crack initiation and higher crack density at lower strains (0.5–2%). However, at higher strains (2–5%), both coatings demonstrate identical crack saturation densities (saturated number of cracks per unit length), accompanied by similar crack toughening mechanisms and evidence of shear strain bands at intercrack regions, indicative of plasticity onset.

A room temperature chemical process for homogeneous mixing of precursor phases for low temperature tetracalcium phoshate preparation

The aim of this study was to prepare phase pure tetracalcium phosphate (TTCP) from the precursor phase mixtures homogeneous at the nano/microscale level at lower heat treatment temperatures in much shorter dwell times.Two different precursor powder mixtures were prepared by reacting CaCO3 with H3PO4 in ethanol or water. The resultant precursor powder mixtures were heat treated at temperatures in the 1200–1350 °C range for 2 and 5 h. Phase structures of the powders were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopy analysis. Scanning electron microscopy (SEM) was used for the investigation of powder particle sizes and morphology. Powders synthesized by the heat treatment of both of the starting powder mixtures prepared in ethanol or water with 2 and 5 h of dwell times at 1350 °C were determined to be phase pure TTCP. SEM analysis along with the phase identification showed that the precursor powder prepared in ethanol had micron sized plates formed by aggregation of sub-micron sized thin CaHPO4 plates covering CaCO3 particles. The precursor powder prepared in water contained large aggregates of sub-micron sized CaCO3 particles whose surface was covered by precipitated nano-sized hydroxyapatite. TTCP powders were composed of large irregularly shaped particles formed by sintering of smaller equiaxed grains. Average grain and particles sizes of the TTCP powders synthesized from the precursor powder prepared in ethanol were 3.2–3.9 and 8.1–8.4 μm, respectively. Average grain and particle sizes of the TTCP powders synthesized from the precursor powder prepared in water however were measured to be 3.3–5.1 and 11.2–11.6 μm, respectively.The TTCP preparation method presented in this study provides homogeneous and well-mixed precursor powders prepared from cheap and commonly available precursors without milling and decreases the heat treatment time to 2 h at 1350 °C.

Evaluating fracture toughness of cold sprayed IN625 coatings: Micro-scratching method

Cold spray deposition of metals and alloys has gained considerable attention due to its advanced applications across various industries. This technique offers numerous advantages, including the absence of phase changes and oxidation. However, the process presents challenges due to its inherent complexities. Plastic deformation is crucial for the successful deposition of powder particles during cold spray. Therefore, achieving an optimal level of plastic deformation is essential. Fracture toughness is one of the important properties that can help understand the degree of plastic deformation in cold-sprayed coatings. Yet, measuring fracture toughness in these coatings is challenging because most evaluation methods are destructive and require large sample sizes. This study investigates the feasibility of predicting the fracture toughness of cold-sprayed coatings. Specifically, the micro-scratching method is employed to predict the fracture toughness of cold-sprayed IN625 coatings. IN625 is selected because of its high-end applications in sectors such as nuclear, marine, and aerospace component manufacturing. In addition to evaluating fracture toughness, the deposited coatings undergo rigorous testing and characterization to establish the microstructure-process-property relationship. The scaling of frictional force and fracture toughness confirms the validity of using scratch data for fracture toughness calculations. Hence, fracture toughness of the resulting coatings was successfully evaluated.

Influence of limestone powder particle size on the sulfate resistance of cement-based materials under the coupling effect of time-varying temperature and sulfate attack

Influence of limestone powder particle size on the sulfate resistance of cement-based materials under the coupling effect of time-varying temperature and sulfate attack

Investigation into the purification and regeneration of rare earth polishing powder waste via continuous solid-phase conversion

The concentration of rare earth elements (lanthanum, cerium, and praseodymium) within rare earth polishing powder waste (REPPW) typically exceeds 50 %, with the majority of impurities comprised of silicon and aluminum-related compounds. Transforming REPPW into recycled rare earth polishing powders that adhere to polishing standards in an eco-friendly and economically viable way presents a significant challenge in the industry. Traditional acid or alkaline processes predominantly recover rare earth elements as oxides, which are underutilized due to their high costs. Considering the varying forms of impurities and rare earth compounds found in REPPW, this research introduces a novel physicochemical decontamination and continuous chemical transformation process aimed at producing regenerated rare earth polishing powders. Under optimal conditions, the physicochemical two-step decontamination process achieved a rare earth recovery rate surpassing 92 %, while silicon and aluminum removal rates reached 86.12 %. During the continuous chemical transformation of REPPW, the rare earth phases in an alkaline setting followed the sequence REOF (CeO2) → RE(OH)3 → RECO3OH→RECO3F→CeLa2O3F3(CeO2), which not only facilitated phase reorganization but also enhanced the particle surface structure. Notably, these chemical transformations did not disrupt the rare earth distribution; instead, they indirectly boosted product purity and uniformly dispersed within the regenerated polishing powder particles, thereby improving polishing efficiency. Consequently, the adoption of this innovative regeneration process for polishing powders holds substantial importance for the sustainable utilization of rare earth resources.

Surface condition driven fatigue performance of laser powder bed fusion H13 steel

Surface variation is an inherent imperfection in the laser powder bed fusion (LPBF) processed samples, comprising of primary roughness (PRR) from the melt pool solidification and secondary roughness (SER) from adhered powder particles. Components under cyclic loading are sensitive to surface defects, making surface finishing crucial for fatigue-bearing parts. However, this undermines LPBF’s advantage of creating high-performance and geometrically complex components. This study examines the effect of surface roughness on fatigue crack initiation in LPBF H13 steel, a high-strength alloy with a tensile strength of 1800 MPa. The focus is on scenarios where contour scanning strategies are not employed. Vertically deposited samples were subjected to three surface conditions: as-built (AB) with PRR + SER, half-polished (HP) with only PRR, and well-machined (M) with no PRR or SER. Optical and digital surface roughness characterization and stress-controlled fatigue testing were performed. Results revealed that while AB-samples showed significantly rough surface compared to HP-samples, their fatigue performance did not reduce. In contrast, M-samples had a slight improvement in roughness but exhibited a fatigue life increase by a factor greater than 17. This was attributed to the PRR, specifically the solidification valleys between the neighboring melt pools. Factographic analysis showed that the PRR-driven fatigue crack initiation is a critical determinant of fatigue performance.

Micromechanical and Tribological Characterization of Fabricated Ti–6Al–4V Alloy Using Laser Powder Bed Fusion

Abstract In the dynamic era of advanced manufacturing technology, laser powder bed fusion (L-PBF) have gained popularity in different domains due to its capability to build parts from bulk to miniature size with higher efficiency and precision. Ti–6Al–4V, a bio-inert metal alloy, possesses a unique blend of profound mechanical and biocompatibility attributes, making it highly suitable for implant applications. This study reports the fabrication of Ti–6Al–4V alloy for implant application via the L-PBF process. The objective is to enhance the micromechanical and tribological properties of the fabricated Ti–6Al–4V component by identifying the optimal processing conditions. The fabricated component exhibited a maximum hardness of 395.26 HV and a minimum frictional coefficient of 0.3193 at 195 W laser power, 900 mm/s scanning speed, and 70 μm hatching distance. The wear-rate and absorbed wear volume were measured as 1.265 × 10−5 mm3 N−1 min−1 and 0.3162 mm3, respectively, under sliding conditions. At optimal processing state, the printed surface displayed an alpha-phase morphology with homogeneous microstructural features due to uniform melting of powder particles that improved bond strength and minimized defects. This study offers an experimental insight into operational attributes, paving the way for accelerated production of Ti–6Al–4V alloy components using the L-PBF method and tailoring tribological properties to meet specific functional requirements.

Fabrication of Aluminium Matrix Composite Powder Reinforced with Silicon Dioxide Tailings for Non-Asbestos Brake Pads (NOB)

Tin mining tailings consist of 80-90% sand and the rest mud. The high levels of Silicon Dioxide (SiO2) in these tailings are hard and can be used as an added material in the manufacture of composites. This research aims to study the physical and mechanical properties of metal matrix composites reinforced with SiO2 powder processed by powder metallurgy, as an effort to provide a replacement material for Non-Asbestos (NOB) motorbike brake linings. The impact of hot compaction pressure in the form of two pressing directions, including 4600, 4500 and 4400 Psi, with a pressing hold of 15 minutes and sintering which includes 30, 20 and 10 minutes, at a temperature of 600 ºC was studied for its effect on hardness and density. Mechanical blending was used with a horizontal ball mill in the ratio of 10:1 at a speed of 90 rpm for 4 hours. The test results showed that the greater the hot compaction pressure and the longer the sintering, the higher the hardness and density values. The highest hardness reached 81.7 HB and the highest density of 2.385 g/cm3 occurred at a bidirectional hot compaction pressure of 4600 Psi, with the lowest wear rate of 0.333 mm3/m. This occurs as a result of the increase in hot compaction has an impact on increasing the contact between powder particles resulting from mechanical alloying to be tighter as a result of which the cavity and porosity decrease

Study on the strength influence mechanism and cracking mechanism of stone powder-cement floor grouting materials

Underground grouting is a concealed project, and it is difficult to test the strength of grouting stones in engineering practice. Aiming at the problems of high confined water pressure and strong water-richness of the roadway floor, a pressure filtration test device was developed, and a PFC2D uniaxial compression model was established to study the variation law of stone strength and crack evolution mechanism of grouting materials under different grouting pressures. The results show that with the increase of pressure filtration value, the amount of slurry dehydration increases, the pore water pressure dissipates, the pores between particles are tightly compressed, the contact force between particle skeletons increases, and the strength of stone body increases. Under the condition of the same cement powder ratio (mass ratio of cement to stone powder) or stone powder particle size, the strength of stone body of stone powder-cement grouting material increases with the increase of pressure filtration value. The stress-strain curves of the stone body with different pressure filtration values all experienced three stages: continuous elasticity, fracture expansion and strength failure. Before the peak, the number of cracks increases slowly; after reaching the peak, the micro-cracks extend rapidly and the number increases rapidly, resulting in the final tensile failure of the specimen. This study can provide a basis for the selection of grouting engineering material ratio and grouting pressure parameters.