Flake Particles Research Articles

Nacre-like aluminum/PVDF energetic composites with enhanced combustion and mechanical properties

This study introduces a nacre-inspired aluminum (Al) flake/polyvinylidene fluoride (PVDF) energetic composite, designed to enhance its combustion and mechanical performance for propulsion applications. In comparison to Al/PVDF composites utilizing spherical micron-sized Al particles, the nacre-like Al/PVDF composite with aligned Al flakes showed a 115% enhancement in tensile strength, a 10% increase in toughness, but a 75% reduction in elongation. A hybrid composite, combining aligned Al flakes and spherical particles, demonstrated a balanced improvement in mechanical properties: a 122% increase in tensile strength, a 96% rise in toughness, and a more modest 29% reduction in elongation. Furthermore, the aligned Al flakes enhanced the thermal conductivity of the composites, resulting in a 53% faster burn rate of Al/PVDF, suggesting that microstructural tuning through flake alignment and particle incorporation influences both mechanical and combustion properties. These findings highlight that nacre-like microstructure can effectively augment the performance of Al/PVDF energetic composites, indicating potential applications in propulsion.

Determining the priority control sources of heavy metals in the roadside soils in a typical industrial city of North China

Heavy metals (HMs) in roadside soils (RS) are closely related to urban ecosystem and human health, but priority control sources and eco-health risks of HMs remain unclear. We explored pollution sources of HMs using positive matrix factorization (PMF), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), and random forest (RF), and assessed their source-specific eco-health risks. The combination of PMF, SEM-EDS and RF indicated that pollution sources of HMs were coal combustion (27.99 %), construction materials (30.15 %), and traffic emissions (41.86 %). SEM-EDS revealed RS particles were identified by a combination of physical (spherical, porous rounded, crustal flake, crustal rounded and irregular particles) and elemental surface characteristics (O, C, Si, Al, Fe, Ca, Mg, K, Zn, Cu, and Mn). RF highlighted road network density, residential density, and industrial density had significant importance influence on pollution sources. Approximately 72.35 % of soil samples were at a low ecological risk with traffic emissions being the major contributor. Non-carcinogenic risks had a minimal effect, but carcinogenic risks were at a cautionary level with coal combustion being the highest contributor. Overall, coal combustion and traffic emissions were regarded as priority control sources of HMs. These findings provided effective guidance for soil pollution prevention and risk control.

Preparation of M-type barium ferrite submicron absorbing powder by one-step high-temperature ball milling and its particle structure regulation

This study investigates a simple and rapid process for directly preparing M-type barium ferrite using high-temperature ball milling. By adjusting the rotation speed of the high-temperature ball milling, the morphology and size of the powder can be altered to regulate its electromagnetic properties, aiming for an overall good absorbing effect. The powder’s morphology, agglomeration properties, elemental valence states, and electromagnetic parameters were characterized using SEM, BET, XPS, EDS, and VNA. The results show that as the milling speed increases, the particle size of the M-type barium ferrite decreases, transitioning from the typical hexagonal flake particles to spherical block particles, forming a porous loose structure with richer dielectric loss mechanisms and enhanced electromagnetic wave loss capacity. Electromagnetic loss performance analysis indicates that at a milling speed of 50 rpm, the powder achieves the best electromagnetic loss of −61.16 dB at a matching thickness of 8.77 mm and a microwave absorption bandwidth of 4.1 GHz.

Performance optimization of FeSiCr/ZnO soft magnetic composites by highly orientation and domain wall engineering

The power loss and permeability of soft magnetic composite (SMC) might be improved by surface modification and magnetic field orientation of flake particles. The oriented ZnO-modified flaky FeSiCr SMCs were produced under the magnetic field. The orienting mechanism of flake powder under a magnetic field produced by Helmholtz coils was investigated using torque model analysis. After surface modification, the permeability and power loss of ZnO-modified flaky FeSiCr SMCs could reach 63 and 421.29 kW/m3(at 50 mT, 100 kHz), respectively. The three-dimensional loss separation results demonstrate that spin rotation mechanism, defects, and dislocations of ZnO modification from theory and experiment may be responsible for the enhanced soft magnetic characteristics.

Mechanical mechanism of shear cavitating water jet dissociation of flake graphite

Abstract To obtain the mechanical mechanism of shear-type cavitation water jet dissociating flake graphite to improve the grinding technology of flake graphite, the motion state of flake graphite particles in shear-type cavitation water jet, the micro-jet impact process, the high-pressure elastic potential energy pressure release process, and the water wedge stretching process have been analyzed using the theory of hydraulic transport of liquid-solid two-phase, the theory of jets, the cavitation primordial principle, the principle of capacity conversion, and the water wedge action. The primary mechanical mechanism of shear cavitation water jet dissociation of flake graphite is collision friction effect, micro-jet impact, pressure release, and water wedge stretching effect, under these four kinds of loads individually or jointly, to achieve the purpose of removing the surface of flake graphite particles of the veinstone minerals to realize the dissociation of flake graphite. Moreover, the collision friction, pressure release, and water wedge stretching effects destroy the material under tensile stress to remove the veinstone minerals, and the micro-jet impact effect is the destruction of the material under compressive stress to remove the veinstone minerals.

Numerical Simulation of Air–Water–Flake Graphite Triple-Phase Flow Field in a Homemade Double-Nozzle Jet Micro-Bubble Generator

The essential part of the flake graphite flotation apparatus is a micro-bubble generator. Developing a micro-bubble generator with a reasonable structure and superior self-absorption performance is crucial to improving flake graphite sorting. In this study, to realize the integrated treatment of the grinding and mineralization of flake graphite, the development and manufacturing of a double-nozzle jet micro-bubble generator were based on the concepts of shear-type cavitation water jets and jet pumps, among other theories. A numerical simulation of the air–water–flake graphite triple-phase flow field of the generator was conducted using the CFD method. The goal was to investigate the grinding and mineralization process of flake graphite by analyzing the distribution of the air phase’s volume percentage and the speed distribution of the air–water–flake graphite triple-phase flow field. The findings indicate that the air-phase volume percentage produced by the generator ranges from 98.3% to 99.9%, and the air-phase volume percentage is evenly distributed within the steady flow tube, achieving the mineralization function. Additionally, the flake graphite particles are dissociated from the flake graphite under the combined effect of friction shear and cavitation of the internal nozzles, thereby achieving the grinding function.

Factors affecting the energy harvesting efficiency of graphite thermoelectric materials

Thermoelectric materials have attracted significant attention for their ability to utilize waste heat for power generation whereas natural flake graphite holds great potential as a thermoelectric material. In this work, a pressure-assisted molding process was employed to fabricate graphite bulks using natural flake graphite with different purities and particle sizes. The effect of structure on the properties of the samples was analyzed. It was found that increasing the purity of graphite is beneficial for its electrical and thermal conductivity. Notably, the thermoelectric performance of graphite initially improves and then decreases with increasing purity. The decrease of flake graphite particle size is advantageous for enhancing the Seebeck coefficient of the samples but detrimental to their electrical and thermal conductivity. It is verified that changing the forming pressure can alter the arrangement orientation of flake graphite in the sample. However, the ordered arrangement of flake graphite is not conducive to the thermoelectric properties of the sample. Ultimately, an optimized process for preparing thermoelectric materials containing graphite was obtained, namely minimizing the orientation of flake graphite in the sample, and selecting graphite with a purity of about 99 % and a particle size of nearly 50 μm.

Hydrothermal precipitation of hematite from the model solution of zinc hydrometallurgical extraction

Abstract The effect of temperature and silicon concentration on iron precipitation and morphology of hematite particles was discussed. The results showed that increase of initial silicon centration will lead to the decrease of iron removal efficiency, and the Fe content decreases and S content increases in hematite. Increasing temperature is beneficial to increase iron removal rate and Fe content in hematite, but increasing temperature can not decrease silicon content in hematite. The content of Si in precipitate is proportional to the concentration of silicon in solution. Silicon is adsorbed on the surface of hematite in the form of silicic acid. Hematite particle was agglomerated microsphere. Increasing concentration of silicon will increase the disorder degree of hematite crystallization. With the increase of silicon concentration, the agglomeration of hematite particle was more obvious, and the average particle size of hematite particles increased. At 175 °C, the morphology of iron precipitation particles are composed of flake particles and rhomboid massive particles, but when the temperature rises to 195 °C, the agglomeration phenomenon is obvious, small flake particles agglomerate into microspherical aggregates.

Modification of discharge sequences to control the random dispersion of flake particles during wafer etching

During the etching of the dielectric layer of semiconductors through plasma etching, numerous flake particles are generated in the etching equipment. These particles cause layout defects on the wafer and engender reduced yield on production lines. Accordingly, this study investigated how such flake particles could form in a chamber involving varying levels of deterioration on the electrostatic chuck surface and varying levels of by-product deposition. Moreover, we tested the effect of various electrostatic chuck discharge sequences and voltages on the deposition of these flake particles. Our experimental results revealed that selecting an appropriate radiofrequency power and a voltage discharge sequence protocol for the electrostatic chuck and using a low-frequency radiofrequency power supply could minimize the number of flake particles adhering to a wafer surface. In the proposed method, wafer contamination is controlled by suppressing unstable electric stress that arises when the etching chamber is coated with deposited by-products and the electrostatic chuck has a deteriorated surface.

Influence of Flake Particles in Manufactured Sand on the Performance of Cement Mortar and Concrete

Influence of Flake Particles in Manufactured Sand on the Performance of Cement Mortar and Concrete

High-temperature magnetic performance and corrosion resistance of hot-deformed and sintered Nd-Fe-B magnets with similar room-temperature magnetic properties

Both hot-deformed (HD) and sintered Nd-Fe-B magnet have huge prospect in the application of permanent magnet servomotor, but its magnetic performance is often influenced by increased working temperature and corrosion environment. Hereby, the high-temperature magnetic performance and corrosion resistance of HD magnets and sintered magnets with similar room-temperature magnetic properties were investigated. The melt-spun Nd-Fe-B powders of MQU-F and MQU-G have been used to prepare the HD magnets without (HDF) and with (HDG) heavy rare earth of Dy element. The sintered magnets of 45H grade (S45H) and 35UH grade (S35UH) were used as reference magnets to evaluate the high-temperature magnetic performance and corrosion resistance of HDF and HDG, respectively. The results show that both HDF and HDG have superior temperature coefficient of coercivity (β), irreversible flux loss (hirr) and corrosion resistance to the same-grade sintered magnets. The analysis on microstructure and element composition reveals that the difference in β and hirr between HD and sintered magnets is mainly resulted from grain size and Pr content. The nanograins in HD magnets are much smaller than the micrograins in sintered magnets. Consequently, |β| and hirr reduces significantly with the decrease of grain size. Meanwhile, the Pr-contained sintered magnets of S45H and S35UH consist of both Pr2Fe14B and Nd2Fe14B phases. As the magneto-crystalline anisotropy of Pr2Fe14B decreases faster than that of Nd2Fe14B with the increased temperature. |β| and hirr of the HDF and HDG are better than those of the same-grade sintered magnets. In addition, the difference in corrosion resistance is primarily caused by the grain boundary (GB) width, the total rare earth (TRE) content and Co content. The corrosion on Nd-Fe-B magnet initiates from and propagates along GB and the boundary of flake particles at the surface of HD and sintered magnets. The narrower GB width, lower TRE content and higher Dy content all play important role in better corrosion resistance of HD magnets.

Development and Performance Evaluation of Stretchable Silver Pastes for Screen Printing on Thermoplastic Polyurethane Films

Efficient, stretchable wiring electrodes are achieved when the resistance change during expansion and contraction is minimal. Herein, we prepared silver pastes specifically designed for screen printing on thermoplastic polyurethane films; they exhibit minimal resistance changes. The pastes were prepared using silver particles with sizes of 2 and 7 μm as well as a mixture of 2 and 7 μm silver particles (50:50 wt%). These pastes were analyzed using methods such as rheological measurements, thermogravimetric analysis, printability tests, tensile and torsion tests, and light-emitting diode (LED) tests. The most promising results were obtained when exclusively using 2 μm silver flake particles. The pastes demonstrated a viscosity of 24,880 cps, a thixotropic index value of 2.82, excellent printability, and consistent resistance measurements even after 100% stretch, thus indicating exceptional tensile properties. Moreover, the pastes exhibited substantial stability, with no change in brightness after the attachment of seven LEDs at 20% tension.

Effect of intercalated and exfoliated graphite particles on the mechanical properties of polymer composite: A micromechanics-computational approach

This study investigated the effects of intercalation and exfoliation of the graphite flake particles on the mechanical properties of elastomeric composites using analytical, computational, and experimental techniques. Relying on the modified Eshelby and incremental Mori–Tanaka approach, a new micromechanics model was proposed to estimate Young’s modulus and develop a constitutive model for expanded graphite (EG)-filled elastomer in finite strain deformation. It was found that when the initial graphite flakes expanded, the actual volume fraction and ultimate aspect ratio of the dispersed particles significantly affected the mechanical properties of the EG-reinforced composites. The present model and subsequent predictions reflect the initial flake diameter, actual volume fraction, ultimate aspect ratio of the particles, and other convenient physical properties of the composite constituents. In addition, molecular dynamics simulations were performed to evaluate the elastic properties of the EG-Matrix interphase region using the COMPASS force field function. The MD results showed that Young’s modulus of the interphase region increased significantly as the quantity of the graphene layer increased. The micromechanics-constitutive model results were validated using the experimentally determined stress–strain relation of the composites. EG- and CB-elastomer nanocomposite specimens were fabricated and tested in the experimental program. Field emission scanning electron microscopy (FESEM) analysis of the cryo-fractured surfaces of the elastomer compounds showed good interactions between the constituents. Numerical computations indicated that the proposed model incorporating the new parameters could accurately predict the experiment at a small particle concentration.

Triboelectrostatic separation of coal gasification fine ash based on different mineralogical characteristics

Unburned carbon particles in coal gasification fine ash can be recycled as fuel for further combustion and ash particles are highly valuable for utilization, which can only be of secondary utilization if the two are separated. Due to the small size of gasification fine ash particles, triboelectrostatic separation has more technological advantages than traditional flotation. In this study, a first attempt has been made to separate carbon and ash particles from coal gasification fine ash by triboelectrostatic separation. It aims to investigate the feasibility of the method and to study how different mineralogical characteristics affect triboelectrostatic separation. Herein, proximate analysis, X-ray fluorescence spectroscopy analysis and X-ray diffraction analysis were adopted to investigate the fundamental nature of raw ash. The triboelectrostatic separation experiments under single conditions were conducted. Carbon enriched products with loss on ignition of 37.45% and ash enriched products with that of 10.32% were obtained whose yield was 29.81% and 32.98%, respectively. Results demonstrated the feasibility of the dry technology to separate residual carbon and ash particles in coal gasification fine ash. Furthermore, triboelectrostatic separation of coal gasification fine ash was significantly affected by differences in particle size and microtopography. Particles of small size were firstly adsorbed by plates in the high voltage electric field. The charge capacity of flake and blocky carbon particles was stronger than that of bonded and flocculated carbon particles allowing them easier to be separated.

Morphology transformation of stainless steel 316L powder from spheres to flakes using high-energy ball milling and the investigation of transformation behaviour

ABSTRACT Today, microfiltration plays the most significant role in removing fine particulate impurities in gas streams used in high-tech industries. However, the current SS316L gas filter has a limitation in enhancing performance due to the trade-off relationship between filterability and permeability. This limitation can be overcome by the geometrical effect of the gas filter that maximises inertial impaction and diffusion interception due to complex flow channels using small flake particles. However, since the smaller the particle size, the yield strength higher, there are few reports of preparing the small flake particles by plastic deformation. This study used a high-energy ball milling process to demonstrate the preparation method for small stainless steel 316L flake particles. Furthermore, the process parameters are systematically optimised to fully transform the spherical particles into thin platelets without fracture and cold welding, and the transformation behaviour is discussed in detail.

Identifying temporal sensory drivers of liking of biscuit supplemented with brewer’s spent grain for young consumers

Brewer's spent grain (BSG), a by-product of the brewing industry, has great potential as food additive. BSG is particularly rich in protein and fibre content which makes it an ideal nutritional fortifier for biscuits. However, adding BSG to biscuits can lead to changes in sensory perception and consumer acceptance. This study explored the temporal sensory profiles and drivers/inhibitors of liking in BSG-fortified biscuits. Six biscuit formulations were obtained from a design with factors oat flake particle size (three levels: 0.5 mm, small commercial flakes, large commercial flakes) and baking powder (two levels: with, without). Consumers (n = 104) tasted the samples, described their dynamic sensory perception using the Temporal Check-All-That-Apply (TCATA) method, and rated their liking on a 7-point categorical scale. The Clustering around Latent Variables (CLV) approach was used to group consumers into two clusters based on their preferences. The temporal sensory profiles and drivers/inhibitors of liking were investigated within each cluster. Foamy and Easy–to–swallow were sensory drivers of liking for both groups of consumers. However, inhibitors of liking were different in the two clusters: Dense and Hard–to–swallow for one cluster and Chewy, Hard–to–swallow and Hard for the other cluster. These findings give evidence that manipulating oat particle size and presence/absence of baking powder changes BSG-fortified biscuits’ sensory profiles and consumer preferences. A complementary analysis of the area-under-curve of the TCATA data and inspection of individual temporal curves showed the dynamics of perception and showed how oat particle size and presence/absence of baking powder affected consumer perception and acceptance of BSG-fortified biscuits. The methods proposed in this paper can be further applied to understand how enriching products with ingredients that would otherwise go to waste affects acceptance in different consumer segments.

Deformation type during the ball milling process: A comparative study of the microstructures formed by ball milling, uniaxial compression, and rolling

The plastic deformation type of metal during ball-milling treatment has not yet been unveiled due to the difficulty in direct observation, and it is also difficult to clarify the deformation behavior even by numerical simulations. A comparative study of the effects of lubrication on the microstructure induced by ball-milling, compression, and rolling was con. Ducted to reveal the deformation type. The deformed flake particle showed a uniform microstructure for the ball-milling treatment with a lubricant. By contrast, the closer the particle surface, the finer the crystal grains were for the treatment without a lubricant. These microstructural features on the ball-milled iron particles were observed in rolled iron sheets, and the effects of the lubricant on the microstructure induced by compression were the opposite. Therefore, we conclude that the type of ball-milling-induced deformation is close to rolling, considering the similarity of the effect of the lubricant on the microstructures.

Metal Particle Movement and Induced Insulator Flashover Under Impact Vibration Generated By Switching Operation in GIS

Gas insulated switchgear (GIS) insulation failures occur frequently in field operations, seriously affecting the reliability of power systems. Fault statistics show that nearly half of the insulation flashover faults in field operation are strongly related to the switching operation, and metal particles are considered to be a crucial cause of flashover. The impact vibration generated by the switching operation may activate the metal particles and make them lift and jump in the GIS, reducing the insulation performance. Therefore, in this study, an experimental platform was established to simulate the impact vibration generated by the switching operation. The flashover characteristics induced by metal particles under impact vibration were studied, and the movement behavior of metal particles was also analyzed. The results show that metal particles lying on the enclosure lift under the impact vibration and then keep jumping in the GIS. These particles can jump to cause insulator flashover with high probability after the impact vibration. The longer the metal particles, the higher the probability of insulator flashover, and the shorter the average jump duration of the metal particles before the flashover. Moreover, compared with the flake particles, linear particles are more likely to cause insulator flashover after the impact vibration. This study demonstrates the mechanism of insulator flashover caused by metal particles under impact vibration, which provides a significant support for understanding the insulation failures strongly related to the switching operation in practical applications.

Improved Separation between Recycled Anode and Cathode Materials from Li-Ion Batteries Using Coarse Flake Particle Flotation

Separation between two recycled electrode active materials from spent Li-ion batteries by a conventional froth flotation method has been challenging due to similarity in their surface hydrophobicity. In this study, a new coarse flake particle flotation technology has been developed to separate the electrode active materials from Li-ion batteries. The new process separates the recycled electrode flake particles effectively at a size range of 212–850 μm by taking advantage of a significant difference in densities between the anode flake materials and cathode flake materials. At a feed size of 212 μm or less, a fraction of recycled cathode particles is floated in the froth layers resulting in a loss of cathode materials in the sink product. At a feed size of 850 μm or above, a small fraction of anode flakes becomes non-floatable, resulting in a decrease in the grade of cathode materials in the sink product. The mechanism has been investigated by induction time measurements, bubble–flake detachment, contact angle measurements, and force analysis. The anode flakes are more hydrophobic than cathode flakes, which is consistent with the result obtained from induction time measurements. A force analysis reveals that the critical size for electrode flake particles being attached to air bubbles varies with advancing contact angle and density. Maintaining a desirable feed size is essential to achieve an optimum separation performance. In this regard, a flotation column is superior to mechanical flotation cells in minimizing size reduction during the flotation process. Lab-scale column flotation trials showed that a good separation between anode and cathode flake particles has been achieved by column flotation with 98–99% purity of cathode flake materials in the sink product at a recovery rate of 96–99%. The present study demonstrates a new process in separating two electrode flake materials from spent Li-ion batteries.

One-step synthesis of micro-sized flake silver particles as electrically conductive adhesive fillers in printed electronics

A novel one-step liquid phase reduction method was proposed to synthesize uniform micro-sized flake silver particles at room temperature. The La(OH)3 was used to replace other expensive agent (H2PtCl6 or H2PdCl4) as structure-directing agent. The role of the reagents and possible formation mechanism of micro-sized flake silver particles were investigated in detail. The effect of each synthesis parameter on morphology and particle size of micro-sized flake silver particles was also explored. It is found that La(OH)3 could control the reduction rate of Ag+ and its oriented growth by adsorbing on the (111) crystal plane of silver particles. The uniform micro-sized flake silver particles with a length of 4-55 μm and thickness of 0.2-5 μm could be synthesized by tuning the synthesis parameters. The synthesized micro-sized flake silver particles presented a smoother and straighter surface compared with commercial micro-sized flake silver particles prepared by ball milling. What is more important, the electrically conductive adhesive (ECA) filled by as-prepared micro-sized flake silver particles printed on polyethylene terephthalate film (PET) exhibited lower bulk resistivity (about 4.4×10-5 Ω·cm) than that filled by the commercial ball-milled micro-sized flake silver particles with the same Ag content of 80 wt. % (about 1.2×10-4 Ω·cm).