Flake-shaped Particles Research Articles

Wear behaviour of Al-MWCNT composites by varying MWCNTs concentration

The present study illustrates the mechanical and wear behaviour of Al-MWCNT composites by varying MWCNTs concentration (0 %,0.25 %, 0.50 % & 1 %) by weight in composites. These composites were synthesized through sintering in the muffle furnace after mechanical alloying which involved flattening and welding particles to form flake-shaped lamellar particles. The presence of MWCNT lamellas restricted grain growth, creating a 2D aluminium layer between the MWCNTs during sintering. Increasing the MWCNT content in aluminum refined the interlayer thickness of the composites. The compressive strength of Al is increased exponentially with the addition of CNTs. By adding CNTs to aluminium, the maximum strength was reached at 460 MPa in 1% samples, and the compression strength of the aluminium increased by 84 % as well. The sintered composites exhibited higher hardness and its value increased significantly when CNTs were added to the Al composite. The wear resistance of aluminium is substantially increased when CNTs are added, and the maximum wear resistance is achieved when CNTs are added at 0.5 wt%. The addition of CNTs reduced wear resistance, which could be attributed to the decrease in interface adhesion and agglomeration effects of CNTs.

Relationship between particle shape and fast-charging capability of a dry-processed graphite electrode in lithium-ion batteries

Improving lithium-ion transport in electrodes by controlling electrode microstructure is a promising option for enhancing the fast-charging capability of graphite anodes in lithium-ion batteries. Dry processing of electrodes based on a polytetrafluoroethylene binder has attracted considerable attention as an alternative to solvent-based wet processing. The morphology of graphite particles has a significant impact on electrode microstructure, but few reports have been published on dry-processed graphite anodes. In this work, we found that the morphology of graphite particles is a key factor to determine the fast-charging capability of the dry-processed graphite electrode as well as the microstructure of the dry-processed graphite electrode. X-ray microscopy combined with mercury porosimetry and symmetrical cell electrochemical impedance spectroscopy reveal that the difference in porosity between the top and bottom layers of a dry electrode with spherical graphite particles is greater than that of flake-shaped graphite particles, resulting in enhanced lithium-ion transport in the electrode and improved fast-charging capability at a high charging rate of 5C (17.5 mA cm−2). These findings supply insights into the effective design of dry-processed graphite anodes with an emphasis on fast-charging capability as well as the development of graphite anode materials for dry-processing based lithium-ion batteries.

Polymer Composites with Carbon Fillers Based on Coal Pitch and Petroleum Pitch Cokes: Structure, Electrical, Thermal, and Mechanical Properties.

The effect of particle size and oxidation degree of new carbon microfillers, based on coal pitch (CP) and petroleum pitch (PET) cokes, on the structure as well as thermal, mechanical, and electrical properties of the composites based on ultrahigh molecular weight polyethylene (UHMWPE) was investigated. The composites studied have a segregated structure of filler particle distribution in the UHMWPE matrix. It was found that composite with smaller CP grain fraction has the highest Young's modulus and electrical conductivity compared to the other composites studied, which can be the result of a large contribution of flake-shaped particles. Additionally, conductivity of this composite turned out to be similar to composites with well-known carbon nanofillers, such as graphene, carbon black, and CNTs. Additionally, the relationship between electrical conductivity and Young's modulus values of composites studied was revealed, which indicates that electrical conductivity is very sensitive to the structure of the filler phase in the polymer matrix. In general, it was established that the properties, especially the electrical conductivity, of the composites studied strongly depends on the size, shape, and oxidative treatment of CP and PET filler particles, and that the CP coke of appropriately small particle sizes and flake shape has significant potential as a conductive filler for polymer composites.

Fractional Maxwell viscoelastic model to explain dynamic magneto-viscoelastic properties of an isotropic magnetorheological elastomer containing flake-shaped magnetic particles

ABSTRACT A modified fractional Maxwell viscoelastic model was developed for the dynamic magneto-viscoelastic behavior of an isotropic magnetorheological elastomer (MRE) having flake-shaped iron particles. This model can capture the low-frequency and high magnetic field static friction contribution with frequency, both in storage and loss modulus. The magnetic dipole-dipole interaction model is used to find the influence of the external magnetic field on viscoelastic behavior. The variation of field-induced modulus with the magnetic field is well described using the Langevin function. The predicted and experimental measured storage and loss modulus agree with the present model with an accuracy of ≥99%. The present model is compared with the results of spherical particle-based MRE.

Correlative Fluorescence and Transmission Electron Microscopy Assisted by 3D Machine Learning Reveals Thin Nanodiamonds Fluoresce Brighter.

Nitrogen vacancy (NV) centers in fluorescent nanodiamonds (FNDs) draw widespread attention as quantum sensors due to their room-temperature luminescence, exceptional photo- and chemical stability, and biocompatibility. For bioscience applications, NV centers in FNDs offer high-spatial-resolution capabilities that are unparalleled by other solid-state nanoparticle emitters. On the other hand, pursuits to further improve the optical properties of FNDs have reached a bottleneck, with intense debate in the literature over which of the many factors are most pertinent. Here, we describe how substantial progress can be achieved using a correlative transmission electron microscopy and photoluminescence (TEMPL) method that we have developed. TEMPL enables a precise correlative analysis of the fluorescence brightness, size, and shape of individual FND particles. Augmented with machine learning, TEMPL can be used to analyze a large, statistically meaningful number of particles. Our results reveal that FND fluorescence is strongly dependent on particle shape, specifically, that thin, flake-shaped particles are up to several times brighter and that fluorescence increases with decreasing particle sphericity. Our theoretical analysis shows that these observations are attributable to the constructive interference of light waves within the FNDs. Our findings have significant implications for state-of-the-art sensing applications, and they offer potential avenues for improving the sensitivity and resolution of quantum sensing devices.

Influence of the particle morphology and internal porosity characteristics of coral sand in the South China Sea on its limit void ratio

An essential physical parameter for describing the characteristics of cohesionless soil is the limit void ratio. A type of cohesionless soil made up of pieces of coral skeleton is known as coral sand. The limit void ratio of the aggregate will be significantly impacted by its distinct particle morphology and internal pores. The influence of particle morphology and internal pores on the limit void ratio of coral sand is investigated in this paper based on the quantitative evaluation of particle morphology and internal pores. The comparison test with natural quartz sand, artificial broken quartz sand, glass balls, and other loose aggregates reveals the impact of mineral composition on aggregates' limit void ratio. The findings indicate that: (1) the roundness of sand particles increases with particle size. (2) The roundness and internal porosity of the sample show an upward trend with an increase in the content of cube-shaped particles. (3) The internal porosity of particles is controlled by the shape of the particles. The internal porosity of cube-shaped particles is the highest, with an average internal porosity of 20.19%, followed by bar-shaped particles, and the lowest in flake-shaped particles. (4) The particle size will not affect the limit void ratio. The limit void ratio of quartz sand and glass ball has a linear negative correlation with roundness, the limit void ratio of coral sand is affected by roundness and internal porosity together, and internal porosity has a significantly greater impact than roundness. (5) Coral sand also largely follows the linear relationship between maximum void ratio and minimum void ratio which is based on terrigenous cohesionless soil.

Effect of Semisolid and Heat Treatment Process on Microstructural Refinement of Al-7Si Alloy.

Improving the engineering properties of Al-7Si cast alloys (300 series) provides an attractive alternative to automotive and aircraft engine industries. The solubility limit of silicon (Si) in Al contributes to the precipitation of flake-shaped Si particles with sharp edges, which function as a stress riser and promote crack propagation during the eutectic phase while also weakening the protective layer's durability. In this study, the impact of microstructure refinement of Al-7Si alloys by using cooling slope, thixoforming and the T6 heat treatment process on hardness and corrosion resistance behavior was investigated. Results showed that the microstructures of the as-cast alloy had a very coarse dendritic shape, whereas the dendritic transferred to the globular α-Al phase, and the Si particles were replaced into a lamellar- or acicular-like shape after the cooling slope and thixoforming process, respectively. The as-cast, cooling slope and thixoformed samples were subjected to the T6 heat treatment process, which enhanced the hardness to 79, 99 and 104 HV, respectively, due to Si particle refinement. The potentiodynamic test revealed that the corrosion rate dropped to 0.00790 and 0.00736 mmpy-1 in the heat-treated cooling slope and thixoforming samples. This finding can be attributed to the substantially refined Si particles and reduced eutectic phase area due to the smaller cathodic to anodic area ratio.

Morphological Evaluation of the Blended Microalgae-Activated Carbon (Mass Ratio 10:7) for Considering Its Impact on Thermal Conversion Processes

Morphology, including size, shape, and structure, plays a crucial role in determining heat and mass transfer within materials during thermal conversion processes. This study presents a concise overview of research conducted on the morphological evaluation of a blended composite consisting of microalgae and activated carbon, with a mass ratio of 10:7. To ensure homogeneity, the mixture was stirred simultaneously at 1200 rpm for 30 minutes. The blended microalgae-activated carbon composite was analyzed using scanning electron microscopy (SEM) to examine its surface structure and morphology. The SEM images revealed the presence of predominantly flake-shaped particles in the sample. The particle size distribution, determined from the SEM images, indicated that particles of approximately 30 μm in size were the most dominant. Considering the impact of this blended composite on thermal conversion processes, the findings suggest that the combination of both materials significantly enhances reactivity during thermal conversion.

Improving filter cake sealing properties for high-density ilmenite drilling fluid

Drilling fluids must be cautiously designed to form an impermeable filter cake layer that diminishes the intensity of solid and mud invasion during drilling of a well. Inability to abate solid and mud invasion can cause adverse effects on the productivity of the drilled well. As a result, a variety of additives have been proposed for improving filter cake's sealing properties, which are also utilized to control fluid filtration. This work investigates the role an amorphous volcanic glass (perlite), a novel filtration agent, to amend the quality of filter cake layer that formed using ilmenite (FeTiO3) drilling fluid. The characteristics of the filter cake were evaluated in terms of the filtration behavior, filter cake thickness, permeability and porosity. In order to accomplish this aim, several concentrations of perlite particles were loaded to the Ilmenite weighted drilling fluid. The tests were conducted under high-pressure high-temperature environment according to API standards. The results of the drilling fluid (containing perlite) were compared with a reference drilling fluid (zero concentration of perlite). It is observed that the perlite containing formulation has improved filtration properties. The flake-shaped perlite particles blocked the filter cake pores and accordingly produced an impermeable filter cake. There was a drastic drop in the filter cake overall permeability after adding perlite concentration of 3 lb/bbl, from 6.09 × 10−3 Darcy to 1.46 × 10−3 Darcy and a significant drop (55%) in the associated filtration volume from 18.5 cm3 to 8.5 cm3. Moreover, perlite-based filter cake lowered the pore size of the filter cake and decreased the filter cake thickness by 45%.

Synthesis of highly sinterable Tb2O3 powders by spray coprecipitation for transparent ceramics: The influence of ammonium hydrogen carbonate to metal ions molar ratio

A modified spray coprecipitation method was used to prepare highly sinterable Tb2O3 nanopowders. The effects of R (molar ratio of ammonium hydrogen carbonate to metal ions) were studied throughout the preparation process. The characteristics of the precursors and Tb2O3 powders were determined using analytical techniques including XRD, FTIR, TG-DSC, and SEM. It was discovered that altering the R values significantly affected the chemical components, microstructure, and homogeneity of the precursors and oxide powders. Ultrafine, monodispersed, and spherical terbium (III) oxide powders were obtained when R = 4, while inhomogeneous rhombic flake-shaped particles were prepared with R ≥ 5. The powders calcined at 800 °C produced Tb2O3 ceramics with the highest optical transmittance of 64.08% at a wavelength of 1064 nm via flowing hydrogen atmosphere sintering at 1520 °C for 10 h. The Verdet constant measured at 632.8 nm for the obtained Tb2O3 sample was −466.3 rad T−1 m−1, which was approximately 3.5 times that of the Tb3Ga5O12 single crystal.

Effects of interfacial interactions between metal and process control agents during ball milling on the microstructure of the milled Fe-based nanocrystalline alloy powder

Fe–Si–B–P–Cu nanocrystalline alloy were treated with ball-mill using a lubricant as a process control agent (PCA). The resulting alloy powder is a strong candidate material for soft magnetic composites. Two ball milling methods (continuous and interval) were employed to control the interactions between the PCA and the alloy surface, and their effect on the microstructure of the prepared alloy particles was investigated. The alloy sheet was broken into small pieces and deformed plastically into flake-shaped particles regardless of the ball milling method implemented. Friction-force microscopy of the alloy immersed in the PCA revealed that the friction coefficient of the alloy surface exposed to air for a certain period was higher than that of the unexposed alloy surface (immediately after polishing). During ball milling, the ratio of the newly generated surface to the oxidized surfaces of the alloy subjected to interval milling was smaller than that of the alloy subjected to continuous milling. Therefore, the friction coefficient of the surface of the alloy subjected to interval milling was higher than that of the alloy subjected to continuous milling. Synchrotron radiation analysis revealed that the alloy subjected to interval milling exhibited enhanced surface friction, showing an obvious steepness and inflection in the diffraction intensity as a function of the tilt angle based on the Schulz reflection method. This indicates formation of crystallographic texture in α-Fe grains in an amorphous matrix. Hence, we demonstrated successfully that the ball milling process induced a crystallographic texture in the Fe-based nanocrystalline alloy due to plastic deformation due to the enhanced surface friction. The surface of the alloy was prepared based on the effect of the interfacial interactions between the alloy surface and the PCA.

Preparation of anisotropic (Ce, Nd, Pr)-Fe-B powder with HDDR method from wasted sintered magnets

With the wide application of Ce-contained rare earth (RE) permanent magnets, recycling of wasted Ce-contained magnets has drawn more and more attention. Hydrogenation-disproportionation-desorption-recombination (HDDR) method was used to prepare anisotropic magnetic powder from wasted (Ce, Pr, Nd)-Fe-B sintered magnet (N45 magnet). The influence of hydrogen pressure in disproportionation (Pdis) and desorption (Pdes) and the disproportionation time (tdis) on the magnetic properties and microstructures of HDDR powders was studied. The Pdis, Pdes and tdis were optimized to be 50 kPa, 5 kPa and 5 h, respectively. The optimized anisotropic HDDR (Ce, Pr, Nd)-Fe-B powder possessed the coercivity of 10.15 kOe, remanence of 11.14kG and the degree of alignment of 0.77. This coercivity has reached 83 % of that of the recycled N45 magnet. Microstructure examination with scanning electron microscope revealed that the optimized HDDR powder is consisted of flake-shaped particles with hierarchical structure. The distribution of rE-rich phase has been significantly influenced by Pdis, Pdes and tdis. The optimized HDDR particles exhibited the best homogeneous distribution of rE-rich phase. The result of transparent electron microscopy (TEM) and energy dispersive spectrometry demonstrated the nature of (Ce, Pr, Nd)-rich phase and (Ce, Pr, Nd)2Fe14B for the rE-rich phase and RE2Fe14B grain phase, respectively. Examination with high-resolution TEM revealed that the optimized tdis resulted in the largest thickness of (Ce, Pr, Nd)-rich phase at grain boundaries and the consequent maximum coercivity of HDDR particles. The orientation of the optimized HDDR particles was analyzed with X-ray diffractometer and electronback-scatter diffractometer. The result revealed well textured HDDR particles and the subordinate nanograins with preferred (001) orientation, suggesting the inherited texture of these HDDR particles from the initial (Ce, Pr, Nd)2Fe14B grains in N45 sintered magnet. This HDDR method was proved to be a prospective strategy in recycling of Ce-contained sintered magnets.

Electromagnetic properties of Sm-doped FeSiAl alloy absorbing materials prepared by melt spinning

The flaky Sm1-xFexSiAl (x = 0,1,2) alloy powders were prepared by melt-spun technique with a wheel speed of 30 m s−1, followed by ball milling method. The flake-shaped FeSiAl alloy particles with the average particle size range from 5µm to 40µm were obtained. The XRD spectra show that the single α-Fe phase without other intermediate phase can be detected for all samples. Complex permittivity decreased remarkable VS complex permeability decreased somewhat with increasing Si content. With the thickness of 1.8 mm, the minimum Reflection Loss (RLmin) of Fe70Si20Al10 alloy powder is −3.4 dB at 2 GHz, while that of Sm2Fe68Si20Al10 alloy powder is −5.8 dB at 3.8 GHz. It is found that the Sm-doped FeSiAl composites can be potential microwave absorbing materials.

Preparation and characterization of nanodiamond reinforced aluminum matrix composites by hot-press sintering

In the present paper, aluminum matrix composites (AMCs) reinforced by nanodiamond (ND) were fabricated by hot-press sintering. The morphology and microstructure of ND/Al composite powders for different milling hours were observed. The effect of ND content on microstructure, mechanical properties and tribological behavior of AMCs was investigated. The relative density, hardness, compressive strength and wear resistance of AMCs with different ND contents were compared. The flake-shape aluminum particles with uniformly distributed ND particles were formed by ball milling for 15 h. A laminated structure of AMCs was formed by hot-press sintering at 550 °C for 5 min. ND was distributed at the grain boundary of Al matrix. At the interface between Al and ND, a layer of Al with high dislocation density was formed, which was closely connected with a layer of amorphous carbon. With increasing of ND content, more and larger pores were presented in AMCs, which caused a decrease in relative density. The hardness, compressive strength and wear resistance of AMCs were significantly improved in comparison with sintered aluminum. The AMC with 2.5% ND obtained the highest hardness and compressive strength and the lowest coefficient of friction and wear rate.

Preparation of flake-shaped Fe-based nanocrystalline soft magnetic alloy particles subjected to plastic deformation

ABSTRACT Fe-based nanocrystalline alloy powder prepared by ball-milling is a potential candidate as a soft magnetic composite (SMC). Since the magnetic properties of particles having a random geometry arising from brittle fracture deteriorate by the presence of a demagnetising field, plastically deformed flake-shaped powders, exhibiting better magnetic properties on account of the suppression of any demagnetising field, are desirable. Microstructure such as grain size, lattice distortion and the distribution of dislocations, are affected by ball-milling treatment which changes the magnetic properties. In this study, Fe-based nanocrystalline alloy sheets are ball-milled with lubricant oil as a process control agent (PCA) and the microstructure of the particles investigated. The PCA effectively suppresses the brittle fracture of the alloy sheet during the ball-milling treatment and plastically deformed flake-shaped particles are then successfully obtained. Transmission electron microscopy reveals that there were few lattice defects in the α-Fe grain of the alloy, which indicated that almost only grain-boundary-mediated processes such as GB diffusion/sliding/migration and grain rotation dominate the deformation mechanism. However, Williamson–Hall analysis based on synchrotron radiation exhibits a slope indicating micro-strain in the α-Fe grains. It is found that the plastic deformation induced by the ball-milling treatment forms a microstructure having lattice distortion but containing few lattice defects. It is considered that a slight growth of the existing grains, which can be induced by thermal treatment, can achieve a strain- and dislocation-free microstructure, which is desirable for soft magnetic alloys.

Molecular transformations in interfaces and liquid media under wet ball milling of iron with N-phenylanthranilic acid

This paper provides FTIR and XPS studies on molecular transformations in interfaces and liquid media under wet ball milling of iron with N-phenylanthranilic acid (NPhA) used as a chelator and corrosion inhibitor. The initial stages of ball milling are accompanied with the formation of a variety of compounds, including complex compounds of iron, polymeric NPhA, ester groups, and non-volatile alkyl derivatives. The NPhA derivatives adsorbed on the surface stabilize the flake-like shape of particles and significantly increase their corrosion resistance in both acidic and neutral media. It has been shown that chelators/corrosion inhibitors may be successfully used as effective process controlling agents for wet ball milling of transition metals of low corrosion resistance to synthesize corrosion-resistant flake-shaped particles. Long-term milling has been shown to make towards the destruction of oxygen-containing groups, including the dehydration of NPhA itself to acridone, a polycyclic compound. The destruction of the modifying NPhA-based surface layer leads to the agglomeration of particles. The intensive destruction of the milling medium ingredients taking place during long-term milling facilitates the accumulation of oxides and carbides.

Evaluation of Static and Dynamic Yield Stress for Isotropic and Anisotropic Particle–Based MR Fluids: Modeling and Analysis

Structural deformation in the low shear rate region that is an undeformed state is investigated for the isotropic and anisotropic magnetic particle–based magnetorheological (MR) fluid. Flow curves were obtained for both MR fluids between 0.1 s−1 and 500 s−1 in the absence and in the presence of magnetic fields. A model to describe the flow behavior over the full shear rate study is proposed. The proposed model accounts for the friction contribution coming from particle-particle as well as particle-carrier interactions of anisotropic particles particularly in flake-shaped particles. The parameters derived from the fit have physical meaning, and it correlates with the observed dependency in rheology study. To get a better understanding of particle-particle friction contribution, magnetic nanoparticles were added in the MR fluid and flow behavior is studied. The study clearly demonstrates the contribution of particle-particle friction on the MR properties. The contribution of particle-carrier friction, due to the shape of the particle, is verified by comparing the result with spherical-shaped particle–based MR fluid.

Performance Enhancement of MR Brake Using Flake-Shaped Iron-Particle–Based Magnetorheological Fluid

Abstract A non-spherically shaped iron particle–based magnetorheological (MR) fluid, particularly flake-shaped, is synthesized and utilized for the first time to evaluate the performance of an MR brake. The effects are compared with the commercially available spherically shaped particle–based MR fluid. The study shows that flake-shaped particle–based MR fluid with 70 % weight fraction of iron particles exhibits 17 % higher breaking torque at relatively low magnetic field strength compared to spherically shaped MR fluid with 72 % particle weight fraction. This increase in the torque value at low field is due to increases in the surface wetted area of flake-shaped particles. This enhances the friction between particle–particle and particle–carrier. Preferable to lower weight fraction requirement, the hysteresis loss is low and fluid has better stability in terms of gravity as well as thermally. The present MR fluid, having flake-shaped particles, improves MR brake performance substantially, both in terms of braking torque value at low field and reducing hysteresis loss. All the results are discussed based on the Herschel-Bulkley model. The performance of the brake is tested and evaluated in detail.

Electromagnetic properties and EMI shielding effectiveness of polymer composites reinforced with ferromagnetic particles at microwave frequencies

By means of the integration embedding scheme, a model is developed for the complex dielectric permittivity and magnetic permeability of polymers reinforced with ferromagnetic particles. The model takes into account the aspect ratio of particles and their aggregation into clusters. The governing equations involve six material parameters that are found by matching the experimental data on the real and imaginary parts of the dielectric permittivity and those of the magnetic permeability (four curves are fitted simultaneously for each material) of polymers filled with spherical and flake-shaped micro- and nanoparticles. Good agreement is demonstrated between the results of simulation and observations on polymers reinforced with carbonyl iron, cobalt, and FeCoNi alloy particles at microwave frequencies in the X-band of the electromagnetic spectrum. The model is applied to evaluate the effectiveness of electromagnetic interference shielding in the transmittance mode by polymer absorbers with spherical and flake-shaped particles. Numerical analysis shows that for the same effectiveness of shielding, reinforcement of polymers with flakes (instead of microspheres) allows the volume fraction of filler to be reduced by a factor of 2 to 3.

Thermal conductivity of flake-shaped iron particles based magnetorheological suspension: Influence of nano-magnetic particle concentration

The non-spherical shape (flake-shape) iron particles based magnetorheological (MR) fluid thermal conductivity is experimentally investigated using the hot-wire method. Under the magnetic field, thermal conductivity is enhanced by 20% compared to spherical shape commercial MR fluid having nearly 20% higher volume fraction of iron particles. This enhancement attributes to the larger contact area of the flake-shape particle (when they form a chain), which helps to transport heat quickly. The magnetic nanoparticles of size 6.5 nm were added to this MR fluid for varying magnetic weight fraction and studied its influence on thermal conductivity. The increase of magnetic nanoparticle concentration enhances the thermal conductivity and increases field reversibility. The observed increase in thermal conductivity and low hysteresis losses is attributed to the friction reduction in flake-shaped iron particles in the presence of nanoparticles.