Average Primary Particle Size Research Articles

Cracking Mechanism and Inhibition Strategies of Polycrystalline NCM Electrode Particles.

Developing a high-energy-density cathode material (LiNi1-x-yCoxMnyO2, NCM) for lithium-ion batteries is crucial to the electric vehicle and energy storage industries. However, the continuous insertion/extraction of Li+ generates diffusion-induced stress, causing NCM particles to crack or even pulverize, leading to battery capacity loss and limiting its wider commercial application. Current experimental studies are primarily postmortem examinations, and it is difficult to capture the particle cracking evolution. Simulation studies frequently ignore or simplify anisotropic volume contraction, demonstrating an insufficient understanding of the cracking mechanism of NCM polycrystalline particles, and cracking prevention strategies still need improvement. Therefore, we develop an anisotropic polycrystalline fracture phase-field model (AP-FPFM) that focuses on the anisotropic volume contraction of primary particles and precisely generates grain boundary distribution, coupling with Li+ diffusion, mechanical stress, and particle cracking. We employ AP-FPFM to demonstrate the behavior and mechanism of NCM polycrystalline particle cracking and illustrate the necessity and importance of anisotropic volume contraction to understand particle cracking. Furthermore, we explore the effects of average primary particle size, secondary particle size, and core-shell structure modulation on crack initiation and propagation and propose strategies to inhibit or migrate NCM polycrystalline particle cracking. This work provides theoretical support for revealing the cracking mechanism of anisotropic polycrystalline NCM particles and supplying optimization strategies to suppress particle cracking and improve the mechanical stability.

Earth-abundant Li-ion cathode materials with nanoengineered microstructures

AbstractManganese-based materials have tremendous potential to become the next-generation lithium-ion cathode as they are Earth abundant, low cost and stable. Here we show how the mobility of manganese cations can be used to obtain a unique nanosized microstructure in large-particle-sized cathode materials with enhanced electrochemical properties. By combining atomic-resolution scanning transmission electron microscopy, four-dimensional scanning electron nanodiffraction and in situ X-ray diffraction, we show that when a partially delithiated, high-manganese-content, disordered rocksalt cathode is slightly heated, it forms a nanomosaic of partially ordered spinel domains of 3–7 nm in size, which impinge on each other at antiphase boundaries. The short coherence length of these domains removes the detrimental two-phase lithiation reaction present near 3 V in a regular spinel and turns it into a solid solution. This nanodomain structure enables good rate performance and delivers 200 mAh g−1 discharge capacity in a (partially) disordered material with an average primary particle size of ∼5 µm. The work not only expands the synthesis strategies available for developing high-performance Earth-abundant manganese-based cathodes but also offers structural insights into the ability to nanoengineer spinel-like phases.

Impacts of Fuel Stage Ratio on the Morphological and Nanostructural Characteristics of Soot Emissions from a Twin Annular Premixing Swirler Combustor.

Soot particles emitted from aircraft engines constitute a major anthropogenic source of pollution in the vicinity of airports and at cruising altitudes. This emission poses a significant threat to human health and may alter the global climate. Understanding the characteristics of soot particles, particularly those generated from Twin Annular Premixing Swirler (TAPS) combustors, a mainstream combustor in civil aviation engines, is crucial for aviation environmental protection. In this study, a comprehensive characterization of soot particles emitted from TAPS combustors was conducted using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. The morphology and nanostructure of soot particles were examined across three distinct fuel stage ratios (FSR), at 10%, 15%, and 20%. The SEM analysis of soot particle morphology revealed that coated particles constitute over 90% of the total particle sample, with coating content increasing proportionally to the fuel stage ratio. The results obtained from HRTEM indicated that average primary particle sizes increase with the fuel stage ratio. The results of HRTEM and Raman spectroscopy suggest that the nanostructure of soot particles becomes more ordered and graphitized with an increasing fuel stage ratio, resulting in lower oxidation activity. Specifically, soot fringe length increased with the fuel stage ratio, while soot fringe tortuosity and separation distance decreased. In addition, there is a prevalent occurrence of defects in the graphitic lattice structure of soot particles, suggesting a high degree of elemental carbon disorder.

Characterization of solid carbon from hydrocarbon pyrolysis in molten aluminum

This study analyzed the synthesized solid carbon from the pyrolysis of methane, ethane, propane, and natural gas using molten aluminum at 1000 °C. Microscopic examination revealed the formation of spherical structures and capped-carbon nanotubes with average primary particle sizes of 0.18–1.29 μm for the spheres and 0.31–0.39 μm for the capped-carbon nanotubes. Methane and ethane pyrolysis generated spherical carbon exclusively, while propane and natural gas pyrolysis produced spheres and capped-carbon nanotubes. The analysis of interlayer spacing indicated the presence of nanocrystalline properties in all carbon samples. X-ray diffraction analysis indicated broad graphitic phases in methane, ethane, and natural gas-derived carbon, and a broad and sharp graphitic carbon peak in propane-derived carbon. Raman spectroscopy confirmed the presence of graphitic structures and disorder, with capped-carbon nanotubes demonstrating more ordered structures than spheres. The thermogravimetric analysis uncovered differences in oxidation behavior, with the mixture of spherical carbon and capped-carbon nanotubes resulting from propane pyrolysis displaying superior thermal stability compared to samples composed solely of spherical carbon. Additionally, the solid carbon samples from the pyrolysis of methane, ethane, and natural gas displayed a final decomposition curve corresponding with commercial carbon black N991. The surface area analysis unveiled that carbon samples derived from ethane and natural gas exhibited surface areas that were 2.4–5.2 times larger than those of commercial carbon black N991 and graphite flakes. These findings underscore the adaptability of tailoring solid carbon materials by selecting the appropriate feed gas to suit specific applications.

Carbon black preparation by partial oxidation of spent tyre pyrolysis oil – Influence of temperature, residence time and oxygen to feed ratio

Preparation of carbon black (CB) by partial oxidation of the spent tyre pyrolysis oil (STPO) and its heavy residue fraction (HRF) was systematically studied using a lab-scale drop tube furnace. The effect of furnace operating temperature (T: 1100 to 1400 °C), residence time (tr: 5 to 60 s) and oxygen to feed ratio (O/F: 174 to 732) on the yield and quality of CB was examined using the response surface methodology (RSM). T was shown to have the most significant influence on CB yield and properties. While the CB yield was also influenced by tr, the quality was more sensitively dependent on T and O/F. The predicted optimal tr and O/F were approximately the same for both feedstocks (60 s and 174, respectively). However, T was higher for the HRF feedstock (1368 °C) than the STPO feedstock (1331 °C) due to the abundance of more viscous heavy hydrocarbons in HRF. Validation experiments under the aforementioned conditions demonstrated the models’ ability to predict responses accurately. The CB from both feedstocks had low contents of ash (<0.03%), volatiles (∼0.5%), sulphur (<0.7%), and high carbon (≥95%). The BET surface area and average primary particle size for CB from STPO and HRF were comparable to those of commercial CBs from fossil fuel feedstock. The CB from HRF had a higher carboxyl oxygen functional group (18%) compared to the CB from STPO (∼13%) and commercial CB (<5%).

Synergistic Effect of Strontium and Melt Quenching on the Solidification Microstructure of Hypereutectic Al-Si Alloys.

The synergistic effect between strontium (Sr) and melt quenching on the solidified microstructure of hypereutectic Al-Si alloys was investigated by optical and scanning electron microscopy. The results indicate that melt quenching can suppress the growth of primary Si particles in the solidified structure of the hypereutectic Al-Si alloy, resulting in a significant decrease of in the average size of primary Si particles in Al-(18~22)Si alloys from 30.35~66.31 μm to 15.13~34.63 μm. The synergistic effect between Sr and melt quenching can further inhibit the precipitation of primary Si particles in the Al-18Si alloy. After the addition of Sr to Al-18Si alloy and undergoing melt quenching, the area fraction of primary Si clearly decreases. When the added amount of Sr increases from 0.1 wt.% to 0.5 wt.%, the area fraction of primary Si decreases from 1.13% to 0.16%. With 0.5 wt.% Sr in the tested alloy, the inhibiting effect on primary Si precipitation was significantly improved. Research has shown that the cooling rate has a significant impact on the solidified structure of the melt-quenched Al-18Si-0.5Sr alloy. There exists no primary Si in solidified structures on the area of 1/8R and 1/4R from the surface of the round bar sample, but the area fraction of primary Si increases, respectively, to 1.97% and 12.48% on the area of 1/2R and R from the surface. The higher the cooling rate, the higher the inhibitory effect on the primary Si precipitation in the Al-18Si-0.5Sr alloy.

Effects of reformed exhaust gas recirculation (REGR) of ethanol-gasoline fuel blends on the combustion and emissions of gasoline direct injection (GDI) engine

Transportation is one of fast-growing sources of greenhouse gas emission worldwide. Road transport accounts as the main cause of HC, CO, NOX, CO2, and PM emissions. Ethanol blended fuel could improve engine performance and reduce both gaseous and PM emissions. Meanwhile, reformed exhaust gas recirculation (REGR) is introduced to achieve simultaneous reduction of NOX and PM from gasoline engines. In this work, the effect of REGR on combustion characteristics, and emissions of the gasoline direct injection (GDI) engine fuelled with ethanol-gasoline fuel blends (E10 and E20) was investigated. The H2 and CO mixture were used as a simulated REGR charge which was fed to the GDI engine’s intake manifold. The H2/CO ratio was determined via modelling of ethanol-gasoline fuel blend reforming based on equilibrium analysis. Moreover, the characteristics of PM emission (e.g. size distribution, primary particle size, morphology) were explored using TEM imaging. The results revealed that REGR could simultaneously improve both the engine thermal efficiency and engine-out emissions. A total number of PM particles and average primary particle size were reduced and compared with baseline (no-EGR) condition. An insight from this investigation can be used for designing control strategies to reduce the negative impact of internal combustion engine usage on human health and environment.

Effect of ammonia addition on the morphology and nanostructure evolution of soot particles in ethylene co-flow diffusion flames

Carbon-free ammonia (NH3) fuel blending hydrocarbon fuel is a viable option to overcome the drawbacks of pure NH3 combustion, but will lead to soot formation. In this study, the effects of NH3 addition (0–40 vol%) on soot morphology and nanostructure evolution in ethylene (C2H4) co-flow diffusion flames were investigated by using thermophoretic sampling particle diagnostic-transmission electron microscopy and lattice-fringe algorithm. The results showed that under the same carbon flow rate, NH3 addition has little effect on the flame height, but great effect on the flame structure and soot formation. With the increase of NH3 blending ratio, the soot volume fraction (SVF), the fractal dimension of the soot aggregates and the average primary particle size showed a gradual decrease. Among them, with 40% NH3 addition, the SVF decreased by 76.7% and the peak average particle size decreased by 34.3% at HAB = 30 mm. Moreover, many particles with multi-core core-shell structure appear in the A40 flame. In terms of nanostructure parameters, the mean fringe length of particle fringes shows a gradually increasing trend, while the mean tortuosity and mean inter-fringe spacing show a gradually decreasing trend with the increasing HAB. NH3 addition causes the fringe length to decrease, the tortuosity and inter-fringe spacing to increase. The soot particles formed in the doped NH3 flames have more disordered structure.

Characterisation of soot agglomerates from engine oil and exhaust system for modern compression ignition engines

The characteristics of soot in oil samples extracted from lubricating oil and exhaust system of a modern common rail compression ignition engine were studied. The morphological parameters of the soot agglomerates were calculated from micrographs obtained by a High-Resolution Transmission Electron Microscopy (HR-TEM). The morphological analysis indicated that the soot in oil agglomerates have a larger average primary particle size and overall larger agglomerate size (determined by the radius of gyration) compared to the agglomerates sampled in the exhaust system. This can be a consequence of the dehydrogenation of hydrocarbon (HC) chains from the oil around the soot agglomerates. The shape of the agglomerates is quantified by fractal dimension. The soot in oil agglomerates presented a slightly larger fractal dimension than those studied in the exhaust system. Therefore, it seems that soot in oil agglomerates were more compact than those found in the exhaust system. The impact on lubricating oil properties should be further investigated.

Ni-rich cathode material with isolated porous layer hindering crack propagation under 4.5 V high cut-off voltage cycling

This study reports on a preparation of novel Ni-rich cathode material with isolated porous layer and its application into cathode in lithium ion batteries extending cut-off potential into 4.5 V. Using intermittent addition of Al salt during co-precipitation of NixCo1-x(OH)2 (0 < x < 1), the isolated porous layer is easily formed inside the final active material particles maintaining overall mechanical integrity and their spherical shape without the change of external particle morphology. Even under severe cut-off potential of 4.5 V, volume expansion/contraction by anisotropic mechanical stress from hexagonal 2 to 3 (H2 → H3) phase transition is greatly reduced by hindering inner particle crack propagation into the external area at particle surface. Due to this phenomena, 227 mAh/g initial capacity at 0.1C was obtained upon 86 mol% of Ni content, with 75 % cathode capacity retention after 100 cycles under 1C, which is highest available capacity value among ever reported. Under full cell configuration, capacity retention at 100 cycles was 77 % and total available energy was increased into 15 % when compared with normal cycling condition of 4.3 V cut-off. From microtomic transmission electron microscope analysis, the porosity of inner particle was maintained as low as 6.67 % under 12 % increase of average primary particle size even after 100 cycles under 4.5 V cut-off voltage. From our advanced utilization of capacity and cut-off voltage, available energy in full cell application of our Ni-rich cathode material exhibited 20 % increase when compared with 4.3 V cut-off voltage.

A high‐throughput chaotic advection microreactor for preparation of uniform and aggregated barium sulfate nanoparticles

AbstractA high‐throughput (105.5 g/h) passive four‐stage asymmetric oscillating feedback microreactor using chaotic mixing mechanism was developed to prepare aggregated Barium sulfate (BaSO4) particles of high primary nanoparticle size uniformity. Three‐dimensional unsteady simulations showed that chaotic mixing could be induced by three unique secondary flows (i.e., vortex, recirculation, and oscillation), and the fluid oscillation mechanism was examined in detail. Simulations and Villermaux–Dushman experiments indicate that almost complete mixing down to molecular level can be achieved and the prepared BaSO4 nanoparticles were with narrow primary particle size distribution (PSD) having geometric standard deviation, σg, less than 1.43 when the total volumetric flow rate Qtotal was larger than 10 ml/min. By selecting Qtotal and reactant concentrations, average primary particle size can be controlled from 23 to 109 nm as determined by microscopy. An average size of 26 nm with narrow primary PSD (σg = 1.22) could be achieved at Qtotal of 160 ml/min.

Зависимость температуры сублимации образующихся в пламенах сажевых частиц от их размеров и структуры

In this paper, the dependence of the sublimation temperature of soot particles synthesized during the combustion of various hydrocarbons, depending on their size and structure, is obtained. The experimental approach is based on the analysis of the thermal radiation of particles heated to the sublimation temperature by a nanosecond laser pulse. The sublimation temperature of soot particles was measured using the two-color pyrometry method. In this paper, it is proposed to use the average size of primary particles to compare data in different flames. It is established, that the sublimation temperature of soot particles depends mainly on the stage of their formation, which is characterized by an increase in average size. It is shown, that with an increase in the average particle size from 12 to 23 nm, their sublimation temperature increases significantly from 2700 to 4500 K. This reflects a significant difference in the thermodynamic and optical properties of the so-called "young" and "mature" soot particles, which must be taken into account when developing methods of soot diagnostics and in the thermo-physical analysis of combustion and pyrolysis processes with the formation of soot.

The dependence of the sublimation temperature of the soot particles formed in the flames on their size and structure

In this paper, the dependence of the sublimation temperature of soot particles synthesized during the combustion of various hydrocarbons, depending on their size and structure, is obtained. The experimental approach is based on the analysis of the thermal radiation of particles heated to the sublimation temperature by a nanosecond laser pulse. The sublimation temperature of soot particles was measured using the two-color pyrometry method. In this paper, it is proposed to use the average size of primary particles to compare data in different flames. It is established, that the sublimation temperature of soot particles depends mainly on the stage of their formation, which is characterized by an increase in average size. It is shown, that with an increase in the average particle size from 12 to 23 nm, their sublimation temperature increases significantly from 2700 to 4500 K. This reflects a significant difference in the thermodynamic and optical properties of the so-called "young" and "mature" soot particles, which must be taken into account when developing methods of soot diagnostics and in the thermo-physical analysis of combustion and pyrolysis processes with the formation of soot. Keywords: flames, soot particles, sublimation temperature, structure of soot particles, transmission electron microscopy, laser-induced incandescence.\

Properties of WCCo Composites Produced by the SPS Method Intended for Cutting Tools for Machining of Wood-Based Materials.

This paper presents the possibility of using the Spark Plasma Sintering (SPS) method to obtain WCCo composite materials. Such materials are used as cutting blades for machining wood-based materials. Two series of composites, different in grain size and cobalt content, were analyzed in the paper. The produced materials were characterized using Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and tribological properties were determined. In addition, preliminary tests were carried out on the durability of the blades made of sintered WCCo composites while machining three-layer chipboard. The results of the microstructure analysis proved that the SPS method makes it possible to obtain solid composites. Phase analysis showed the occurrence of the following phases: WC, Co, and Co3W9C4. The lowest friction coefficient value was found in samples sintered using powder with an average primary particle size of 400 nm (ultrafine).

Part I: A Study of the Underlying Factor(s) Effecting the Change of Point of Zero Charge With Decreasing Particle Size

The general consensus in multiple fields is that changes in the average primary particle size of metal-oxides and -hydroxides affects their Point of Zero Charge (PZC). In the course of this study on anatase titania, a method was developed to minimize the effect of all known variables affecting the material’s pHPZC, save particle size. This led to the discovery of two regions for point of zero charge. Above the average spherical particle diameter ≅ 29, (Region I) pHPZC remains constant demonstrating particle size has no effect on this value . Below a diameter ≅ 29 nm (Region II), pHPZC values decrease in an almost linear manner.

Chemical mapping of tire and road wear particles for single particle analysis

Tire and road wear particles (TRWP), which are comprised of polymer-containing tread with pavement encrustations, are generated from friction between the tire and the road. Similar to environmentally dispersed microplastic particles (MP), the fate of TRWP depends on both the mass concentration as well as individual particle characteristics, such as particle diameter and density. The identification of an individual TRWP in environmental samples has been limited by inherent characteristics of black particles, which interfere with the spectroscopic techniques most often used in MP research. The purpose of this research was to apply suitable analytical techniques, including scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDX) mapping and time-of-flight secondary ion mass spectrometry (ToF-SIMS) mapping, to characterize the specific physical and chemical properties of individual TRWP. Detailed elemental and organic surface maps were generated for numerous samples including bulk tread material, cryogenically milled tire tread particles, and TRWP generated from two separate road simulator methods. Key physical and chemical characteristics of TRWP for single particle identification included (1) elongated/round shape with variable amounts of mineral encrustation, (2) elemental surface characteristics including co-localization of (S + Zn/Na) ± (Si, K, Mg, Ca, and Al), and (3) co-localization of organic surface markers, such as C6H5+ and C7H7+. Comparisons of TRWP with other polymeric (polystyrene) and non-polymeric (carbon black) particle types demonstrated that a combination of physical and chemical markers is necessary to identify TRWP. Addition of a density separation step to the single particle analysis techniques allowed for the determination of average primary TRWP particle size (34 μm by number distribution and 49 μm by volume distribution) and aspect ratio (65% of TRWP with an aspect ratio > 1.5). The use of chemical mapping techniques, such as SEM/EDX and/or ToF-SIMS mapping as demonstrated herein, can support future research efforts that aim to identify complex MP.

EBSD study of the microstructure and texture evolution in an Al–Si–Cu alloy processed by route A ECAP

Microstructure and texture of an Al–Si–Cu alloy subjected to high-temperature equal channel angular pressing (ECAP) were evaluated by electron backscatter diffraction (EBSD). Besides, the inhomogeneity of the ECAP process was investigated in three different zones of ECAPed specimens (i.e., top, center, and bottom). The texture evaluation showed that by increasing the number of passes, the A∗1 and A∗2 components strengthen, and theB/B¯ component becomes stable. Excellent grain refinement was observed after the first pass due to the recrystallization through particle-stimulated nucleation (PSN) mechanism. After the fourth passes, the average size of primary silicon particles (PSPs) and eutectic silicon particles (ESPs) decreased to 26 μm (41%) and 2.8 μm (48%), respectively, compared to the as-cast specimen. The long strain path at the bottom of ECAP die led to significant refinement of the microstructure of the Al alloy, while, due to the high strain rate at the top of the die, the refinement of microstructure postponed. However, a remarkable fragmentation of PSPs has happened at the top of the ECAP die.

Fabrication of Silica Nanoparticle Monolayer Arrays Using an Anodic Aluminum Oxide Template.

Non-close-packed (NCP) silica nanoparticle monolayer arrays (SNMA) on ordered porous anodic aluminum oxide (AAO) templates were fabricated for the first time by a novel two-step spin-coating technique. The obtained NCP-SNMA-AAO was composed of silica nanoparticles (average primary particle size of 440 nm) and well-organized nanopores on the AAO substrates. NCP-SNMA-AAO with a supporting ratio of 87% silica nanoparticles showed a hydrophilic surface (water contact angle of 51.0°), while the original AAO substrate shows a hydrophobic surface (water contact angle of 107.9°). The maximum coefficient of static friction was decreased by 29% (0.327 → 0.233). The coefficient of dynamic friction was also decreased by 20% (0.281 → 0.226). We found that controlling the silica supporting ratio using the two-step spin-coating technique is an effective approach for surface modification of an AAO substrate.

An Experimental Study of Homogeneous Nucleation of Supersaturated Antimony Vapor: Determination of the Surface Tension of a Critical Nucleus

Homogeneous nucleation of supersaturated antimony vapor has been studied in a laminar-flow chamber with the use of transmission electron microscopy, diffusion spectrometer of aerosols, supersaturation cutoff, laser light scattering, and other methods. Surface tension σs of a critical nucleus and radius Rs of its surface of tension have been determined from the experimentally measured temperature field by numerical simulation of the processes occurring in the chamber. The calculation results are in good agreement with the measured profile of a deposit on chamber walls, the average size and concentration of formed aggregates, the average size of primary particles, and their number in an aggregate. Equivalent volume Veq = 0.87 cm3 of the zone of intense nucleation, average nucleation rate I = 5 × 1010 cm−3 s−1, average supersaturation S4 = 3.2 × 106, average temperature T = 421 K in this zone, and radius Rs = 0.63 nm and surface tension σs = 220 mN/m of critical nuclei formed in this zone have been calculated. The surface tension of antimony nuclei has appeared to be lower than the surface tension of its planar surface by 46%. In our previous works, it was found that the surface tension of critical bismuth nuclei was, on the contrary, markedly higher than that of its planar surface. Different signs of the deviation from the surface tension of a planar surface have, for the first time, been observed for elements of the same group.

Influence of Al₂O₃ Nanoparticle Addition on a UV Cured Polyacrylate for 3D Inkjet Printing.

The brittleness of acrylic photopolymers, frequently used in 3D Inkjet printing, limits their utilization in structural applications. In this study, a process was developed for the production and characterization of an alumina-enhanced nanocomposite with improved mechanical properties for Inkjet printing. Ceramic nanoparticles with an average primary particle size (APPS) of 16 nm and 31 nm, which was assessed via high-resolution scanning electron microscopy (HRSEM), were functionalized with 3.43 and 5.59 mg/m2 3-(trimethoxysilyl)propyl methacrylate (MPS), respectively, while being ground in a ball mill. The suspensions of the modified fillers in a newly formulated acrylic mixture showed viscosities of 14 and 7 mPa∙s at the printing temperature of 60 °C. Ink-jetting tests were conducted successfully without clogging the printing nozzles. Tensile tests of casted specimens showed an improvement of the tensile strength and elongation at break in composites filled with 31 nm by 10.7% and 74.9%, respectively, relative to the unfilled polymer.