Large Particles Research Articles

High-Volumetric-Energy-Density Cathode Material from Single-Sized Precursor via Precise Additive Control

To overcome the energy density limitations of current layered cathode materials, high-nickel cathode materials with a bimodal distribution composed of ∼ 15um-sized secondary particles and micron-sized single crystals are synthesized from a single-sized high-nickel precursor by incorporating the grain-growth promoting/inhibiting additive. Synthesized cathode material effectively reduces the pores within the electrode and shows an excellent electrode density of > 3.9 g/cm3, exceeding ∼ 80 % of the theoretical density. In addition, due to efficient contact between large secondary particles and small single crystals, bimodal particles with additives show higher electrical conductivity compared to additive-free monomodal secondary particles, and a capacity of ∼ 220 mAh/g is achieved even at a high loading level of ∼ 30 mg/cm2 and 96 % active-material fraction. Based on remarkable electrode density and high capacity, it is possible to realize a volumetric energy density of more than 700 mAh/cm3. To the best of our knowledge, this is the highest energy density result for electrodes made from layered cathode materials. Moreover, through the synergistic effect of morphology control by selective additives and surface coating, the synthesized bimodal cathode simultaneously exhibits excellent capacity as well as improved cycle-life performance compared to a bare cathode without additives. The enhanced electrochemical performance is attributed to increased connectivity between individual cathode particles, decreased bulk/surface resistance, and reduced intergranular cracks after cycling through structure design by additives, which is confirmed through various electrochemical analyses and electrode observations.

Improving thermal shock and oxidation resistance of Cr3C2/WC-NiCr cermet coating by embedding large NiCrAlY superalloy particles

Cr3C2/WC-based cermet coating is widely used on the surface of mechanical equipment to strengthen its wear and corrosion resistance. Improving the high-temperature performance of cermet coating is the key to its industrial application. In this study, a novel type of bimodal microstructure cermet coating with the design of functional sites was fabricated via high-velocity air fuel (HVAF) spray technology. The toughness NiCrAlY superalloy particles are introduced into the traditional Cr3C2/WC-NiCr cermet structure to construct the thermal stress release site, which significantly improved the thermal shock resistance and thermal oxidation properties of the coating. The addition of NiCrAlY superalloy particle reduces the porosity of Cr3C2/WC-NiCr coating to 0.29 % and creates high-quality interface bonding and surface passivation layer. The newly structured cermet coating exhibits outstanding high-temperature performance. In a 1000 °C oxidation environment, the new coating remained intact after 120 h of exposure, while the traditional Cr3C2/WC-NiCr cermet coating exfoliated completely after 48 h of exposure. Further, in the thermal shock condition at 1000 °C, the lifetime of the new coating is 50 times greater than that of the traditional cermet coating, displaying excellent ability to relieve thermal stress. Additionally, the new coating shows good wear resistance and stability during high-temperature thermal exposure. After thermal exposure for 24 h and 72 h, the wear rates of the coating are 5.28 and 5.83 × 10−5 mm3 N−1 m−1, respectively, which is slightly lower than that of the as-sprayed coating. This study provides guidance for the improvement of high temperature resistance of thermally sprayed Cr3C2/WC-based cermet coatings.

Variations of the elemental composition distribution over the thickness of YBa2Cu3O7-δ thin films obtained by pulsed laser deposition from one target

Epitaxial YBa2Cu3O7‒δ (YBCO) films 150-200 and 300 nm thick, respectively, were deposited on SrTiO3 (100) substrates by pulsed laser deposition at different conditions: with and without using the velocity filtration technique. The films have T(R=0) in the range of 77.4 - 87 R(T) depending on the conditions of deposition from one target with YBa2Cu3O6.8 composition. The films contain Zn, Sr, Pd, Ag and Ti impurity elements obtained from the target (a total of no more than 2 at. % ). Data of the film resistance temperature dependences, X-ray phase analysis, analysis of X-ray fluorescence (XRF) spectra and study of the surface relief by SEM methods revealed the nonuniform distributions of impurity and matrix Y, Ba, Cu elements over the film depth. Impurity concentrations near the surface lead to the formation of faceted spiral pyramids on the surface, which probably evolve into large elongated particles according to the Ostwald mechanism. This knowledge is practically important for optimizing pulsed laser deposition technologies and creating 2D instruments and devices for studying physical phenomena.

Multigenerational effects of combined exposure of triphenyltin and micro/nanoplastics on marine medaka (Oryzias melastigma): From molecular levels to behavioral response

In natural environments, micro/nanoplastics (MNP) inevitably coexist with various pollutants, making it essential to examine their combined toxicity and intergenerational effects on marine organisms. This study investigated the combined toxicity and intergenerational effects of exposure to triphenyltin (T), microplastics (M), nanoplastics (N), a combination of microplastics and triphenyltin (MT), and a combination of nanoplastics and triphenyltin (NT) on marine medaka. The results showed that all treatments had adverse and intergenerational effects on marine medaka. Regarding oxidative stress and energy metabolism, smaller sized plastic particles caused more significant damage to the organisms. However, MT inflicted greater gonadal system damage than NT, leading to imbalanced sex hormone levels. Additionally, T induced hyperactivity in fish, whereas MNP tended to induce behavioral depression. Notably, large plastic particles in the F0 generation had a more pronounced impact on depressive behaviors compared to smaller particles. These findings suggest that both individual and combined exposures to TPT and MNP can detrimentally affect marine medaka from the molecular to behavioral levels, posing risks to population sustainability. This study provided a robust theoretical foundation and deeper insights into the ecotoxicological impacts and risk assessments of coexisting pollutants.

Multimodal 3D quantification of particle stimulated nucleation in industrially manufactured aluminium AA5182 sheet

Particle stimulated nucleation is a dominant recrystallisation mechanism observed in many industrially relevant aluminium alloys during thermomechanical processing. In this work, we quantify particle stimulated nucleation in 3D in an aluminium AA5182 alloy sheet cold-rolled to 75 % thickness reduction. Second phase particles and nuclei are mapped in the same sample volume by conventional laboratory absorption X-ray tomography and synchrotron X-ray Laue micro-diffraction. The large second phase particles are classified as Fe- and Mg-rich phases. It is found that84 % of the nuclei are particle stimulated and 40 % of the particles stimulate nucleation. The critical particle diameter is found to be 4μm. Deviatoric elastic strains are derived from micro-diffraction data and it is found that elastic strains are present in the recrystallised nuclei. The effects of the different particle types, particle clustering, particle size and aspect ratio as well as strain inheritance are discussed. This work provides a full 3D quantification of particle stimulated nucleation behaviour in AA5182 alloy sheet deformed to high strain.

Depletion forces beyond the diluted limit

The determination of the effective interactions in many-body systems still possesses a tremendous challenge in Condensed Matter Physics. The problem mainly resides in the fact that, on the one hand, there is not a unique route to obtain the effective forces between the ”observable” constituents and, on the other hand, one typically considers that the diluted limit of those components always corresponds to the effective forces at all particle concentrations. In the particular case of colloidal dispersions, it is very important to have experimental, theoretical, and computational tools that allow us to determine, accurately and without using significant approximations, the effective interactions between colloids. In this contribution, we report on a detailed study of depletion potentials in colloidal mixtures at finite concentration, namely, binary and ternary mixtures of disks (in two dimensions or 2D) and spheres (in three dimensions or 3D). To this end, the depletion forces between the large colloidal species are determined through a recently developed scheme based on the so-called contraction of the description, which has been extended and built at the level of the bare forces, i.e., we basically consider that all particles interact through the bare potentials and the net force acting on a given particle is determined by the second’s Newton law. This scheme can be easily adapted to Molecular Dynamics simulations. To verify the physical consistency of the formalism, we explicitly show that in the diluted limit of large particles, the resulting depletion potential reproduces correctly the AO-Vrij limit. As further proof of the accuracy of the results, a comparison of the structure of the large colloids in the whole mixture with the one that results using exclusively the depletion potential is carried out. In 3D, the results are explicitly compared with the potential of mean force and those obtained with the integral equations formalism. We also report a new colloidal stability mechanism based on the use of two different species of depletant agents at low and equal concentrations. Although we highlight the fact that the depletion potential depends on the concentration of the large species, we show that this dependence can be eliminated when the colloidal dispersion is open to a reservoir of small particles, i.e., when the chemical potential of small particles is fixed. Finally, we report the effects of polydispersity on the depletion interaction between large colloids.

Cocrystal screening in minutes by solution-mediated phase transformation (SMPT): Preparation and characterization of ketoconazole cocrystals with nine aliphatic dicarboxylic acids

The rapid and efficient cocrystal screening, based on solution-mediated phase transformation (SMPT), was applied to the screening of cocrystals between ketoconazole (KTZ) and nine aliphatic dicarboxylic acids. Cocrystals formed successfully, in minutes, with a change of suspension characteristics, either a cake formation or the formation of large particles. Bulk cocrystals were characterized by powder X-ray diffraction, thermal analysis, and Raman spectroscopy. Single crystals were grown, and molecular structures were determined. Three previously reported cocrystals were reproduced, and six new cocrystals were discovered, including one that was reported as a failure in literature by solution or grinding method. Two hydrogen-bonded motifs are observed in these nine cocrystals: Most cocrystals form hydrogen bonded discrete tetramer with two KTZ and two acids molecules; while two cocrystals form infinite chain. This study demonstrated the high efficacy of cocrystal generation using the slurry screening method. It should be fully utilized in future cocrystal screening.

Intercomparison of WRF-chem aerosol schemes during a dry Saharan dust outbreak in Southern Iberian Peninsula

The Iberian Peninsula (IP), where this study is conducted, has experienced an increase of the frequency and intensity of Saharan aerosol dust outbreaks over the latest decades, which may have an impact on its regional climate. The Weather Research and Forecasting model coupled with chemistry (WRF-chem) has been used worldwide to simulate dust outbreaks and can support the analysis of such potential impacts. However, it includes multiple alternative aerosol parameterization choices that have not been conveniently evaluated in the study region yet. Here, three of the most popular WRF-chem aerosol parameterization schemes, namely, the Goddard Chemistry Aerosol Radiation and Transport (GOCART), the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) and the Modal Aerosol Dynamics Model for Europe (MADE) schemes, are inter-compared during a strong and dry dust outbreak on July 2021 in southern IP. The results show that the three schemes predict qualitatively similar dust intrusion patterns that are consistent with ground observations and have inter-model dust loading differences smaller than 4%. However, their average dust size distributions differ notably. While GOCART is reasonably consistent with observations, MOSAIC underpredicts the amount of dust particles with sub-micron diameters and overpredicts that of large particles and MADE does the opposite. This is found to have a strong detrimental impact on the prediction performance of dust optical properties in MOSAIC and MADE, which is related, at least partially, with issues in the required inter-sectional redistribution of dust parameters during the dust emission and calculation of optical properties. Overall, GOCART generally appears a better choice for strong and dry dust outbreak events in southern IP. It remains to be evaluated during wet dust outbreaks, which is a work underway.

A conceptual model for the formation of ramparts on Martian impact crater ejecta

Mars Orbiter Laser Altimeter (MOLA) elevation measurements for 23 different impact craters and 12 different long runout landslides show rampart ridges on Martian fluidized ejecta flows are higher relief than those on Martian landslides. We propose a conceptual model to explain this height difference that is based on the effects of the impact and ejecta emplacement process on the development of ejecta ramparts. Our model explains the relatively high relief of the distal ramparts as well as the particle size distribution that is inferred from thermal inertia measurements. In this model, impact events produce ejecta curtains that advance radially at increasingly higher velocity outward excavating and roughening the surface as they impact. This produces an inertia-driven, ground-hugging ejecta flow composed of primary and secondary ejecta. This flow moves rapidly across the surface following closely behind the impacting ejecta curtain. The ejecta curtain continuously adds impact-generated debris to the flow front that includes large particles, some of which are overridden by the flow, but some accumulate at the flow front. These particles are pushed forward at the flow front as a high-friction “dam” with the accumulating material growing into a relatively high rampart as the ejecta curtain adds more large particles to it. In addition, the impact-roughened surface cause substantial vibrations and shear in the flows moving behind the ejecta curtain. This roughness results in kinetic sieving in the flows that brings large particles to the surface and transports them to the flow front where some are also overridden or accumulate to add the ones already at flow front. We propose that these processes combine to produce the observed high ejecta ramparts. The relatively high velocity of the ejecta flows pushes the load of coarse-grained debris to the top of even high developing ramparts. When the flow halts, it drains back from the accumulated coarse debris at the flow front, leaving a high rampart dominantly composed of large particles.

SYNTHESIZING OF AN ALUMINUM ALLOY RICH IN IRON AND SILICON BY SURFACING WITH A CONSUMABLE ELECTRODE

Developing lightweight, high-strength materials is an important technological problem of the present decade. However, alloying with expensive elements is mainly used to increase the strength of structural materials. In contrast, aluminum alloys with a specific ratio of silicon and iron show very high mechanical properties. This work aims to develop a technology for synthesizing an aluminium-based alloy with a high content of iron and silicon, consisting mainly of intermetallic phases and having high strength and hardness. The additive technology method of surfacing with a consumable electrode produced the alloy. The ratio of the initial components, meticulously determined, led to the precise chemical composition of the alloy. As a result of the synthesis, an ingot with a uniform microstructure and insignificant porosity, a testament to the careful process, was obtained. At room temperature, the alloy has a phase composition of 42.6% β-phase, 43.4% θ-phase and 13.5% FCC-phase. Phases β and θ are large particles between which the FCC aluminum phase is located. The hardness of the intermetallic β/θ is 450.8±5 HV1, FCC aluminum has a hardness of 92.5 HV1. This research has the potential to inspire further developments in materials science and engineering.

Realizing active targeting in cancer nanomedicine with ultrasmall nanoparticles.

Ultrasmall nanoparticles (usNPs) have emerged as promising theranostic tools in cancer nanomedicine. With sizes comparable to globular proteins, usNPs exhibit unique physicochemical properties and physiological behavior distinct from larger particles, including lack of protein corona formation, efficient renal clearance, and reduced recognition and sequestration by the reticuloendothelial system. In cancer treatment, usNPs demonstrate favorable tumor penetration and intratumoral diffusion. Active targeting strategies, incorporating ligands for specific tumor receptor binding, serve to further enhance usNP tumor selectivity and therapeutic performance. Numerous preclinical studies have already demonstrated the potential of actively targeted usNPs, revealing increased tumor accumulation and retention compared to non-targeted counterparts. In this review, we explore actively targeted inorganic usNPs, highlighting their biological properties and behavior, along with applications in both preclinical and clinical settings.

Shear characteristics of nonuniform distribution of granular materials in ring shear test and impact on landslides

Knowledge of the shear behavior of landslide soil is very important for understanding landslide dynamics. This study investigated the shear behavior of base soil particle materials using ring shear tests with glass beads. Samples with varying particle sizes and distributions were examined to explore how particle size affects shear behavior at different shear velocities. Analysis of the samples included assessment of shear stress, displacement-shear stress fluctuations, and changes in the shear stress standard deviation. Results showed that with increasing shear displacement, shear stress fluctuations stabilize. Rather large difference particle size differences lead to more uniform particle mixing and a lower shear stress standard deviation. Conversely, when smaller particles predominate, particle mixing is less uniform, resulting in a higher shear stress standard deviation. Additionally, this study discussed the shear dilation and compaction mechanisms of samples under large displacement shear.

Hevea brasiliensis rubber particles' fluid interfaces reveal size impact on early coagulation steps

Natural rubber originates from the coagulation of rubber particles (RP) from Hevea brasiliensis latex. The size distribution of Hevea RP is bimodal with the presence of small rubber particles (SRP) and large rubber particles (LRP). This study aims at getting a better understanding of the early coagulation steps of Hevea RP taking into account the particle size. SRP and LRP were obtained by centrifugation of freshly tapped ammonia-free latex from RRIM600 clone. Size and zeta potential measurements showed that both RP fractions were efficiently separated and stable in basic buffer. SRP and LRP dispersions were placed in a Langmuir trough and RP were let to adsorb at the air-liquid interface to form interfacial films. Surface tension and ellipsometry indicate that the formation kinetics and the stabilization of the film at the air-liquid interface are faster for SRP than LRP. Moreover, the arrangement of RP at the interface differs between SRP and LRP, as shown by Brewster angle microscopy, atomic force microscopy and confocal laser scanning microscopy. First, the RP membrane and cis-1,4-polyisoprene core spread at the air-liquid interface before clustering. Then, while the SRP fuse, the LRP keep their structure in individual particles in floating aggregate. The role of the non-isoprene molecules on the different organization of SRP and LRP films is discussed, the one of the two major RP proteins, SRPP1 (Small Rubber Particle Protein) and Rubber Elongation Factor (REF1) in the early coagulation steps.

Image processing and neural network technique for size characterization of gravel particles

Particle size is considered one of the significant characteristics used in geotechnical practices. Traditionally, sieve analysis is utilized for coarse-grained soil. However, this method could be time consuming and take much effort, especially for large scale infrastructure projects. This paper presents an efficient method for estimating gravel particle characterization utilizing image processing and artificial neural network technique (IPNN). The proposed algorithm is performed by utilizing particle boundary delineation and shape feature extraction to train a neural network model for estimating gravel size distribution curve. It is found that excellent agreement exists between the results obtained from conventional sieve analysis and neural analysis for gravel soil particles with maximum difference in passing percentages up to only 3.70%. The proposed technique shows satisfactory results for crushed stone samples with maximum difference in passing percentages about 10.90% mainly in large diameter particles. The presented technique (IPNN) could offer a promising alternative technique for material quality control process especially in large scale projects.

Effect of cellulose nanocrystals on the emulsion stability and rheological properties of microalgal Pickering emulsions

This study investigates the effect of cellulose nanocrystals (CNCs) to Pickering emulsions prepared with microalgal particles (Spirulina sp. (SPI), Chlorella sp. HS2 (CLO)). The microalgae particles show a weak interfacial localization and Pickering behavior on the O/W emulsion depending on the size (avg. drop size ∼5.39 μm with SPI and 22.15 μm with CLO), resulting in a different stabilization effect. When CNC is additionally mixed with the Pickering emulsions including large microalgae particles (CLO), CNC replaces microalgae particles and localizes at the interface, enhancing strong emulsion stabilization. For the Pickering emulsions including small microalgae (SPI), CNC localizes at the continuous phase, forming a network structure regardless of the concentration. This interfacial localization behavior of CNC against microalgae particles is reflected in the rheological behavior of the Pickering emulsion. Depending on the location of CNC, the emulsions exhibit the two-step yielding behavior, mainly attributed to the CNC network in the continuous phase. The complex role of particles in the emulsion system is more sensitively reflected in the large amplitude oscillatory shear (LAOS) region, characterized using the sequence of physical process (SPP) rheological analysis. The maximum elasticity (Emax) in SPP analysis, which indicates the recovery of the deformed structure, exhibits a significant difference, discriminating structural characteristics of CNC dispersion incorporated with microalgae particles. Emulsion with CLO-CNC has lower Emax than the SPI-CNC case because CNC particles disperse at the interface and the continuous phase. Then the distance between CNC particles is longer, resulting in a weak network structure throughout the emulsion. Due to a weak network of CNC, the emulsion is more vulnerable to coalescence compared to the SPI-CNC system. Therefore, this study suggests that CNC particles added to the Pickering emulsion with microalgae compete to localize at the interface and give coalescence suppression effects to the emulsion. Also, for the Pickering emulsion system composed of multi-particles, rheological analysis including SPP analysis successfully indicates structural characteristics and flow-induced stabilization of Pickering emulsions with multi-particles that microscopic characterization could not detect.

Aluminum particles as anode material for lithium ion batteries: effect of particle sizes on the electrochemical behaviours

This study presents a preliminary investigation on using pristine aluminum particles as anodes for lithium-ion battery. The microstructural characteristics of aluminum particle samples with sizes from 100 nm (0.1 μm) to 70 µm were analyzed by the SEM and XRD methods. The electrochemical behaviors of the aluminum particles were examined by the cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) measurements. The obtained results demonstrated the distinct lithiation/delithiation features of the aluminum electrodes at the potential couple of around 0.25 V/0.50 V vs. Li/Li+. Moreover, the GCD results also revealed the strong impact of the particle size on the initial capacity and galvanostatic discharge/charge potential profiles of electrode samples. However, aluminum electrodes with the large-sized particles showed dramatical capacity decay after certain cycles, and stabilized at around the specific capacity of 50 mAh g-1 and exhibited capacitive charge/discharge behavior. In contrast, the nano-sized particles aluminum electrodes possessed stable electrochemical performance upon cycling, but with low initial capacities. The results in this work will enrich the knowledge of the aluminum-based anode for LIBs in future works.

Improvement in the Number of Velocity Vector Acquisitions Using an In-Picture Tracking Method for 3D3C Rainbow Particle Tracking Velocimetry

Particle image velocimetry and particle tracking velocimetry (PTV) have developed from two-dimensional two-component (2D2C) velocity vector measurements to 3D3C measurements. Rainbow particle tracking velocimetry is a low-cost 3D3C measurement technique adopting a single color camera. However, the vector acquisition rate is not so high. To increase the number of acquired vectors, this paper proposes a high probability and long-term tracking method. First, particles are tracked in a raw picture instead of in three-dimensional space. The tracking is aided by the color information. Second, a particle that temporarily cannot be tracked due to particle overlap is compensated for using the positional information at times before and after. The proposed method is demonstrated for flow under a rotating disk with different particle densities and velocities. The use of the proposed method improves the tracking rate, number of continuous tracking steps, and number of acquired velocity vectors. The method can be applied under the difficult conditions of high particle density (0.004 particles per pixel) and large particle movement (maximum of 60 pix).

Characterization of Palmyra palm (Borassus flabellifer Linn.) sap after harvest across different pH ranges for production of palm sugar

The quality of palm sap harvested from the inflorescence of Palmyra palm (Borassus flabellifer Linn.) trees can vary significantly from one container to another, affecting the production of palm sugar. Assessing the pH of the sap is a quick and convenient method for farmers to gauge its quality in Palmyra palm fields. In this study, palm sap collected from various containers was categorized into four groups based on different pH ranges. The objectives were to assess the physical, chemical, and microbiological characteristics of each group and to correlate these characteristics using principal component analysis, as well as to produce palm sugar from each group. The findings revealed that the palm sap with a pH below 5.0 (pHA) exhibited higher levels of reducing sugars, titratable acidity, and total phenolic substances, along with increased lactic acid bacteria (LAB) loads, larger particle sizes, lower contents of total and non-reducing sugar, protein, amino acids, and browning color values compared to sap from other pH ranges (pHB: 5.6–6.5, pHC: 6.9–7.5, and pHD: above 8.0). Principal component analysis indicated similarities between the palm sap groups of pHC and pHD, which were highly correlated with protein and total amino acids, total sugar contents, browning index, and color values of a* and b*. Conversely, pHA was distinct, being highly correlated with reducing sugar and total phenolic contents, titratable acidity, LAB loads, L* value, and particle volume. Meanwhile, pHB showed a high correlation with potassium and calcium contents, % transmission, electrical conductivity, and coliform loads. Crystallization of palm sugar derived from pHA sap was challenging, whereas sugar from the other sap groups readily crystallized. It can be concluded that pH evaluation strongly contributed to parameters of palm sap quality for palm sugar production.

Effects of particle size composition and burden ratio on burden segregation in the blast furnace throat based on DEM

In blast furnace charging, burden segregation affects the distribution of gas flow and the efficiency of chemical reactions, which in turn impacts the overall efficiency and quality of ironmaking. This work developed a bell-less top charging model based on the DEM to analyze burden segregation at the furnace throat under various particle size compositions, chute inclinations, and burden ratios. The results show that the burden exhibits a ring-like distribution around the furnace throat, with smaller particles concentrated in the inner ring near the center. When particle size difference of the burden is significant, adjusting the proportion of large or small particles has a more pronounced effect on particle size segregation near the center of the blast furnace. The smaller the chute inclination, the more serious the particle size segregation of the burden. Pellet tends to accumulate near the center of the blast furnace, with a segregation index reaching 0.8 in this region. Adjusting the burden ratio has a more pronounced effect on the segregation of sinter. This work provides theoretical support for charging optimization in blast furnace operation.

Numerical analysis of the ignition and gas-phase flame evolution of pulverized coal based on online experimental diagnostics

A transient ignition model employing a reduced chemical mechanism was developed to investigate the ignition characteristics and the gas-phase flame evolution of pulverized coal particles. The chemical percolation devolatilization (CPD) model was chosen to simulate the devolatilization process, and its accuracy was validated using a high-temperature entrained-flow reactor. Additionally, a novel method was introduced to cross-validate the single-particle simulation results with real-time OH-PLIF experimental measurements of particle streams, particularly at a large particle spacing ratio. The ignition mode was determined using the ignition delay time and volatile burnout time. Results show that as the oxygen volume fraction increases from 5% to 50% at a temperature of 1800 K, the ignition mode transitions from homogeneous ignition (GI) to heterogeneous ignition (HI). Notably, the same ignition mode was observed regardless of whether GI was defined using gas-phase temperature or OH levels. In the homo-heterogeneous ignition mode, the gas-phase flame intensity, characterized by OH levels, increases rapidly, then decreases, and re-increases slightly. The sequence of gas-phase reactions initiates with volatile combustion, followed by the co-combustion of residual volatiles and newly generated CO, and culminates in the combustion of CO itself. Online experimental findings confirmed that CO originates from char oxidation. Throughout this process, the gas-phase flame front extends outward until the volatiles are consumed.