Interparticle Cohesion Research Articles

Bi-Dimensional PTFE Fibrillation Process Implemented in Solvent-Free Manufacturing of Ultra Thick Electrodes for Lithium-Ion Batteries

A method for manufacturing electrodes via a solvent-free dry process can dramatically increase the energy density of lithium-ion batteries (LIBs) without the use of toxic organic solvents. This innovative approach is a strong candidate for advanced battery technologies due to its environmental benefits and cost savings. However, ultra thick electrode required to achieve high energy density significantly intensifies the migration resistance (Rion) and charge transfer resistance (Rct) by longer diffusion length of lithium ions and electrons.The fundamental solution proposed to solve this problem is to increase the conductive additives content to form the enhanced electronic conductivity networks. However, the higher the content of conductive additives in the electrode composition, the more binder is required. If the binder content is insufficient, the increased contact area and excessive agglomeration due to the high specific surface area of the conductive additives will result in reduced interparticle cohesion and uneven packing density. This hinders the formation of a continuous fiber matrix in the PTFE fibrillation process and consequently weakens the mechanical properties of the electrode.In this study, the proposed bi-dimensional PTFE fibrillation process can be effectively utilized to form a uniform and efficient fiber matrix within electrodes, even at high conductive additives content (≥5 wt%) and low binder content (≤1 wt%). This process enables the electrodes to be stored and transported in roll form and preserves the structural integrity of the electrodes during mass production. Moreover, the high and uniform conductivity of the manufactured electrodes prevents significant increases in resistance, even with increased electrode thickness, thus enhancing the electrochemical performance of high energy density LIBs.

Influence of stearate dry coating on ibuprofen powder: What about the combustibility?

Dust explosion is one common type of process safety incident within the pharmaceutical industry. During powder processing, surface modification is widely used to increase dust flowability by alleviating inter-particle cohesion. However, it is currently unclear whether the addition of guest particles affects the combustibility of pharmaceutical powders. To investigate the explosion hazard of stearate-coated ibuprofen powder, this paper studied the ignition sensitivity and explosion severity of pure and coated ibuprofen by determining a series of explosion parameters in accordance with ASTM standards. The results indicated that the addition of stearate significantly reduced the minimum ignition energy of the mixture. Other parameters including the minimum ignition temperature, the minimum explosible concentration, the maximum explosion pressure, and the maximum rate of pressure rise were found to have less correlation with the improvement in dust flowability. Powder characterization through methods such as the Hausner ratio, scanning electron microscope, thermo-gravimetric analysis, and X-ray diffraction were employed to investigate chemical phase changes between coated mixtures and pure pharmaceuticals. The effects of improved dust flowability and dust dispersibility on the combustibility of ibuprofen dust were discussed to improve explosion-proof awareness in the pharmaceutical industry.

Assessing processability of milled HME extrudates: Consolidating the effect of extrusion temperature, drug loading, and particle size via Non-dimensional cohesion

The downstream processability of Hot Melt Extrusion (HME) Amorphous Solid Dispersions (ASD), an underexplored topic of importance, was assessed through a multi-faceted particle engineering approach. Extrudates, comprised of griseofulvin (GF), a model poorly water-soluble drug, and hydroxypropyl cellulose (HPC), were prepared at four drug concentrations and three HME temperature profiles to yield cases with and without residual crystallinity and subsequently milled to five sieve cuts ranging from < 45 μm to 355 – 500 μm. Solid state characterization was performed with XRPD, FT-IR, and TGA. Particle scale properties of the milled extrudates were evaluated including particle size, density, surface energy, and morphologies imaged via SEM. It was observed that regardless of sieve cut size, drug concentration and HME conditions impacted the flowability trends, quantified via Flow Function Coefficient (FFC) and bulk density. As a novelty, the effects of various process parameters and drug loadings were consolidated into a dimensionless interparticle cohesion measure, granular Bond Number (Bog), to better correlate them with bulk powder properties. The significant contrast in particle morphologies, particle size, and densities among selected cases demonstrated that particle size alone should not be the sole consideration when correlating particle scale to bulk powder scale properties of milled extrudates. Instead, the HME temperature profile and ASD drug loading may be more suitable parameters affecting the bulk powder properties of the milled extrudates.

CT image-based simulation of microbially induced carbonate precipitation

Soil improvement efforts occasionally negatively impact the delicate balance of the natural environment and disrupt ecosystems. Thus, adopting ecologically sensitive techniques that can harmoniously safeguard the Earth is imperative. Recently, researchers have focused on microbially induced carbonate precipitation (MICP), an eco-friendly soil enhancement method that fosters increased interparticle cohesion and augments the mechanical strength of soil. The spatial distribution of calcium carbonate precipitation in MICP-treated soil can be observed using scanning electron microscopy and X-ray computed tomography (CT). However, since this precipitation occurs in the microscopic region, it cannot be directly observed over time. Therefore, in this study, we propose a simulation technique to replicate the MICP process using a voxel dataset obtained via X-ray CT analysis. The calculated patterns of calcium carbonate were distributed on the soil particles in the same manner as the spatial precipitation observed in the experiments. Notably, some precipitates bridged the soil particles, indicating that the proposed technique could morphologically estimate the calcium carbonate distribution through MICP. Evidently, the proposed technique could accurately simulate MICP phenomena. Furthermore, the results showed that the proposed technique can effectively express a multidiscliplinary phenomenon. Therefore, the study can inspire further studies that employ such techniques to investigate MICP.

Self-growing biomimetic functional hydrogel particles for conformance control in tight reservoir fracture network

Hydraulic fracturing is gradually becoming a common approach for enhancing the oil production from tight reservoirs. Blocking agents such as soft particle systems are necessary as a means of conformance control to mitigate the side effect of reservoir heterogeneity due to hydraulic fracturing. In this work, a novel technique based on the mussel biomimetic concept is proposed to generate self-growing biomimetic functional hydrogel particles (SG-BFHPs). The fracture conformance control capacity of the products is evaluated, and the results show that multi-scale (0.5–3.0 mm) SG-BFHPs can cohere and grow at the reservoir condition, and the median agglomerated particle size can increase by 20–25 times. High flow resistance (Frr = 10.7–11.8), facilitated by the higher adhesion between the biomimetic particles and the pore walls, can be established by SG-BFHPs while maintaining a good injectivity. In the single-fracture model, the increased oil recovery by SG-BFHPs is about 12.2 %, and in the matrix-fracture model can be increased from 9.2 %–13.5 % to 25.8 %–28.8 %. AFM experiments show that SG-BFHPs have stronger adhesion between particles or rock surface than conventional hydrogel particles. After conformance control of SG-BFHPs, the particles are distributed in an irregular structure in the fractures and adsorbed on the fracture wall under the effect of inter-particle cohesion and adhesion, which can realize fracture channel adjustment by the particle self-growing. The SG-BFHPs studied in this paper provide valuable insights for the development of dispersed particle gel, which is of great significance in improving oil recovery in tight reservoirs.

Investigation of thermal damage in explosive bridgewire detonators via discrete element method simulations

AbstractExploding bridgewire (EBW) detonators are used to rapidly and reliably initiate energetic reactions by exploding a bridgewire via Joule heating. While the mechanisms of EBW detonators have been studied extensively in nominal conditions, comparatively few studies have addressed thermally damaged detonator operability. We present a mesoscale simulation study of thermal damage in a representative EBW detonator, using discrete element method (DEM) simulations that explicitly account for individual particles in the pressed explosive powder. We use a simplified model of melting, where solid spherical particles undergo uniform shrinking, and fluid dynamics are ignored. The subsequent settling of particles results in the formation of a gap between the solid powder and the bridgewire, which we study under different conditions. In particular, particle cohesion has a significant effect on gap formation and settling behavior, where sufficiently high cohesion leads to coalescence of particles into a free‐standing pellet. This behavior is qualitatively compared to experimental visualization data, and simulations are shown to capture several key changes in pellet shape. We derive a minimum and maximum limit on gap formation during melting using simple geometric arguments. In the absence of cohesion, results agree with the maximum gap size. With increasing cohesion, the gap size decreases, eventually saturating at the minimum limit. We present results for different combinations of interparticle cohesion and detonator orientations with respect to gravity, demonstrating the complex behavior of these systems and the potential for DEM simulations to capture a range of scenarios.

Micromechanics of contact-bound cohesive granular materials in confined compression.

The mechanical behavior of granular materials results from interparticle interactions, which are predominantly frictional. With the presence of even very small amounts of cohesion this frictional interparticle behavior significantly changes. In this study, we introduce trace amounts of cohesive binder between the intergranular contacts in a sample of quartz particles and apply one-dimensional (1D) compression loading. X-ray computed tomography is performed in situ during 1D compression. We make observations at three different length scales. At the macroscopic or ensemble scale, we track the evolution of the porosity, particle size and the stress-strain response during this compression. At the microstructure or interparticle scale, we compute the directional distribution of contacts and the particles. We also track the evolution of the fabric chains with continued compression. We also evaluate particle rotations, displacements, contact twist, rotation, and sliding. We show through our experiments that even a small amount of cohesion (as low as 1% by weight) significantly changes the response at multiple length scales. This interparticle cohesion suppresses the fragmentation of grains, alters force transmission and changes the structure of the ensemble.

A mixing index for uniformly and gap-graded cohesionless particles influenced by mixing rate and diameter of stirring rods

Soil mechanics, sometimes, deals with the mixing of soil such as in deep mixing of soil and mixing of soil in tunnel boring machines, i.e., earth pressure balance (EPB-TBM) shields. The geometry of mixing apparatus such as size of stirring rods plays an important role to achieve higher degree of mixing. Moreover, the effect of gap-graded particles being mixed on degree of mixture should also be evaluated. It is important to estimate the extent of mixing of the soil to confirm the required performance of such phenomenon.This study aims to propose a simple method to quantify the degree of mixture of solid particles stirred by rotation of rods with varying diameters at different mixing rates. Discrete element method (DEM) is used to simulate the stirring process and evaluate the degree of mixture at each rotation based on the spatial distribution of different types of particles. To reduce complexity in the mixing process of particles, this study focuses on monodispersed (i.e., uniformly graded) and bidispersed (i.e., narrowly gap-graded) spherical particles where inter-particle cohesion is not considered. The DEM results reveal spatial variation of the degree of mixture (dm) in the given volume; however, its mean (dm¯) increases with the rotation number of stirring rods. Besides, dm¯ depends on the size of stirring rods whereas the mixing rate is less sensitive to dm¯ for the non-cohesive sandy particles. The dm¯ of narrowly gap-graded particles cases is slightly on the lower side as compared to that of uniformly graded particles. The results of the DEM simulations are validated through the model test.

Influence of desiccation during freeze-thaw cycles on volumetric shrinkage and tensile strength of compacted clayey soils

Tensile strength is a crucial mechanical property that governs the initiation and propagation of soil tensile cracks. With the global prevalence of warming effects and extreme climatic events, the recurrent freeze-thaw (F-T) cycles intensify the complex evolutions of soil pore structure and tensile strength in regions with widespread seasonal freezing or permafrost active layers. This study investigates the combined influence of F-T cycles and desiccation on the tensile strength of clayey soils. Specimens with varying compaction water contents (14.5%, 16.5%, and 18.5%) and dry densities (1.5 Mg/m3, 1.6 Mg/m3, and 1.7 Mg/m3) were prepared and subjected to cyclic F-T actions. A direct tensile test apparatus was utilized to measure tensile strength (σt) along the desiccation path. Additionally, the changes in void ratio (e) and suction (s) during F-T cycles were analyzed to understand the mechanism behind the changes in σt. Experimental results reveal that as the number of F-T cycles (N) increases, water content (w) declines at a decreasing rate and eventually stabilizes. With increasing N, the tensile displacement at failure and σt show a pattern of initially decreasing and subsequently rising, with the inflection point typically around 1.5%–2.0% lower than the compaction water content (w0). Under a few F-T cycles, soils compacted at the optimum water content and on the wet side exhibit higher void ratio and lower suction and σt compared with dry-side compacted soils. However, this trend reverses with further increasing N. In addition, σt increases as compaction dry density (ρd0) rises within all water content ranges, primarily attributed to the significant interparticle cohesion controlled by a dense pore structure. The variation of σt under F-T and associated desiccation is linked with the microstructural evolution characterized by aggregates, interaggregate pores and water-bridges. It is recommended to compact soils both on the dry side of the optimum water content and at the maximum dry density to enhance the freeze-thaw resistance of earth-works in seasonally frozen regions.

Structural fluctuations in thin cohesive particle layers in powder-based additive manufacturing

Producing dense and homogeneous powder layers with smooth free surface is challenging in additive manufacturing, as interparticle cohesion can strongly affect the powder packing structure and therefore influence the quality of the end product. We use the Discrete Element Method to simulate the spreading process of spherical powders and examine how cohesion influences the characteristics of the packing structure with a focus on the fluctuation of the local morphology. As cohesion increases, the overall packing density decreases, and the free surface roughness increases, which is calculated from digitized surface height distributions. Local structural fluctuations for both quantities are examined through the local packing anisotropy on the particle scale, obtained from Voronoï tessellation. The distributions of these particle-level metrics quantify the increasingly heterogeneous packing structure with clustering and changing surface morphology.

CFD-DEM investigation of the dispersion of elongated particles in the Turbuhaler® aerosol device

Elongated drug particles have the potential to be superior to spherical drug particles for delivery to the deep lung due to their increased ability to align with the airflow. However, the performance of elongated particles within dry powder inhalers (DPIs) has been largely unexplored. This paper presented a CFD-DEM study to simulate the dispersion of elongated active pharmaceutical ingredient (API) particles with equivalent sizes of 1.55–5.53 μm in a commercial DPI device Turbuhaler®. The model, which adopted a multi-sphere approach to mimic the shape of elongated spherocylindrical particles, was validated by comparing experimental data of fluidized beds. The model was then utilized to simulate the dispersion of powders with different aspect ratios in Turbuhaler. Findings revealed that the depositions of elongated particles in the chamber and the mouthpiece were significantly higher than those of spherical particles, and the depositions increased with higher aspect ratios. The higher deposition of the elongated particles was due to much stronger inter-particle cohesion when particles were in flat contact with particles or wall surfaces. Similar to spherical particles, both emitted dose and fine particle fraction (FPF, % mass of particles below 5 μm) of elongated particles increased with flow rates due to intensified particle-wall collisions. On the other hand, the FPF of elongated particles in the device decreased more significantly with increasing cohesion than spherical particles. Results indicated that while elongated particles are preferred for drug delivery to deeper lungs, their poor dispersion in inhalers due to higher deposition needs to be considered.

Improvement of the deposition efficiency and adhesion strength of cold sprayed fluoropolymer coating by laser surface texturing of the substrate

High-performance polymer cold-spraying is attracting the interest of many for its economical, time-saving, and environmentally safe features in comparison to traditional thermal spraying processes. The cold spray process allows applying functional polymer coatings on a similar or dissimilar material surface for protective measures or additional functionalities. However, its practical use has been restricted by inherently low deposition efficiency associated with a weak interfacial adhesion strength.In this study, fluoropolymer powder mixed with 5 wt% of nano-alumina was cold-sprayed on laser-textured carbon steel substrates. A thorough analysis of the particle deposition as a function of the spray parameters (gas temperature, pressure, pass number, traverse speed) was performed to highlight the effect of the laser-texturing (groove geometry, laser pitch, pattern) on the deposition efficiency and adhesion strength. By laser-texturing the substrate, the deposition efficiency increases up to 60 %, and the adhesion strength reaches 1.25 MPa. Thus, while the addition of nano-alumina enhances the interparticle cohesion, a laser-textured substrate promotes the mechanical interlocking at the particle/substrate interface.

Micro-ballistic response of thin film polymer grafted nanoparticle monolayers.

Self-assembled polymer grafted nanoparticles (PGNs) are of great interest for their potential to enhance mechanical properties compared to neat polymers and nanocomposites. Apart from volume fraction of nanoparticles, recent experiments have suggested that nanoscale phenomena such as nanoconfinement of grafted chains, altered dynamics and relaxation behavior at the segmental and colloidal scales, and cohesive energy between neighboring coronas are important factors that influence mechanical and rheological properties. How these factors influence the mechanics of thin films subject to micro-ballistic impact remains to be fully understood. Here we examine the micro-ballistic impact resistance of PGN thin films with polymethyl methacrylate (PMMA) grafts using coarse-grained molecular dynamics simulations. The grafted chain length and nanoparticle core densities are systematically varied to understand the influences of interparticle spacing, cohesion, and momentum transfer effects under high-velocity impact. Our findings show that the inter-PGN cohesive energy density (γPGN) is an important parameter for energy absorption. Cohesion energy density is low for short grafts but quickly saturates around entanglement length as adjacent coronas interpenetrate fully. The response of γPGN positively influences specific penetration energy, , which peaks before chain entanglement starts (<Ne). We further divide the ballistic response into three regimes based on grafted chain length: short graft, intermediate graft, and entangled graft. The short grafted PGNs show fragmentation due to almost no cohesion between particles, and the rigid body motion of the nanoparticles absorbs most of the energy. When chains are in the intermediate graft length regime, the film fails by chain pull-out, and unraveling of grafts is the primary dissipation mechanism. The Ashby plot of penetration energy, Ep, indicates ballistic processes are inelastic collisions when grafted chains are short and vary with density in a power law fashion as expected from momentum transfer. The response indicates that a lower nanoparticle weight fraction, ϕwtNP, leads to higher energy absorption per mass, that is, the added mass of nanoparticles does not warrant proportionate increases in energy absorption in the parametric range studied. However, the peak deceleration, Ab, shows a clear positive effect of adding NPs. Finally, PGNs with intermediate chain lengths simultaneously show relatively higher and Ab.

Investigation of Engineering Properties and Solidification Mechanism of Loess by Sodium Silicate Alkali‐Activated Coal Gangue Powder

The aim of this study is to investigate the engineering properties and solidification mechanism of loess through the use of alkali‐activated coal gangue powder with sodium silicate. Experimental methods and comprehensive analysis were employed to examine the effects of different proportions of alkali‐activated coal gangue powder with sodium silicate on the engineering properties of loess, including mass shrinkage, compressibility, and shear strength. Additionally, scanning electron microscopy was utilized to gain in‐depth insights into the interaction and solidification mechanism between loess and alkali‐activated coal gangue powder. The results show that the sodium silicate alkali‐activated gangue powder curing loess has significantly improved the compressive strength and shear strength of the loess. With a ratio of 7 : 2 : 1, the 28 days compressive strength of solidified loess is 1.7 MPa, and the shear strength is 67.92 kPa, which is 1.91 and 2.13 times the 28 days compressive strength and shear strength of unmixed gangue powder and sodium silicate specimens respectively. The hydration–hydrolysis reaction, ion‐exchange reaction, and volcanic ash reaction of the gangue powder under an alkaline environment generated hydrides that filled the pores between soil particles, enhanced the interparticle cohesion, and made the internal structure of the specimens denser, improving the engineering performance of loess solidification. The proposed sodium silicate alkali‐activated gangue powder curing loess mechanism can provide a theoretical reference for the engineering application of gangue powder and the curing modification of loess.

CFD-DEM model of plugging in flow with cohesive particles

Plugging in flows with cohesive particles is crucial in many industrial and real-life applications such as hemodynamics, water distribution, and petroleum flow assurance. Although probabilistic models for plugging risk estimation are presented in the literature, multiple details of the process remain unclear. In this paper, we present a CFD-DEM model of plugging validated against several experimental benchmarks. Using the simulations, we consider the process of plugging in a slurry of ice in decane, focusing on inter-particle collisions and plugging dynamics. We conduct a parametric study altering the Reynolds number (3000...9000), particle concentration (1.6...7.3%), and surface energy (21...541 mJ/m^2). We note the process possesses complex non-linear behaviour for the cases where particle-wall adhesion reduces by more than 20% relative to inter-particle cohesion. Finally, we demonstrate how the simulation results match the flow maps based on the third-party experiments.

Coupled CFD-DEM simulation of submarine landslide movement behavior

Submarine landslide is a common disaster geological phenomenon in the ocean, which can be destructive to underwater infrastructure. Therefore, it is necessary to simulate the evolutionary behavior of submarine viscous landslides. In this paper, computational fluid dynamics (CFD) and discrete element method (DEM) are used to establish the fluid-solid coupling model of water-particle interaction. Firstly, the inter-particle cohesion model is introduced to train the coupled CFD-DEM analysis of the kinematic evolution process, and at the same time, two typical cases are carried out to verify the analysis. In the experimental simulation, the kinematic and morphological characteristics of the submarine landslide were simulated considering the viscous effect and initial velocity of the landslide, and the influence mechanism of the landslide motion and evolution process was investigated in depth. The results show that the coupled method can better simulate the motion of submarine landslide, and the viscous effect of the landslide has a significant influence on its kinematic and morphological characteristics, and the initial velocity also significantly affects the evolution and distribution characteristics of the particle flow field of each part of the landslide in the process of motion. This study is important for the simulation and effective prediction of the kinematic evolution process of real submarine landslides.

Effect of cohesion on structure of powder layers in additive manufacturing

Producing a consistent layer quality for different raw-materials is a challenge for powder-based additive manufacturing. Interparticle cohesion plays a key role on the powder spreading process. In this work, we characterise the structure of deposited layers in the powder-base additive manufacturing process by numerical simulations using the discrete element method. The effect of particle cohesion on the quality of powder layers is evaluated. It is found that higher interparticle cohesion lead to poor spreadability, with more heterogeneous powder layer structure and enhances particle size segregation in the powder layer. We also compare the powder layer quality deposited on a smooth substrate with that on a powder layer. Deposition on a powder layer leads to inferior layer quality of powder layer with higher heterogeneity and higher particle size segregation effects.Graphical abstract

An energy‐based strategy to predict the thickness and content of randomly oriented nanolayers aggregates/agglomerates in thermoplastic polymer nanocomposites: Experimental and analytical approaches

AbstractIn this study, the formation of clay nanolayer clusters inside the high‐density polyethylene (HDPE) matrix was evaluated using a specific strategy based on energy equilibrium in the melt mixing stage. Furthermore, the formed interphase region around nanoparticle domains was precisely evaluated considering the molecular structure of the matrix and linear variation of the physical/mechanical characteristics. The obtained results were used in a developed analytical model to predict the tensile modulus of the nanocomposite system containing randomly oriented nanoparticle domains. The domains consisted of exfoliated, intercalated, or aggregated/agglomerated nanolayers placed in different excluded volumes as the components of an equivalent box model. Different comparative studies were performed using the obtained data from different tests, applied to the prepared HDPE/clay nanocomposite samples, and other data from the literature. It was found that the confrontation between the exerted dispersion energy, by the mixer, and interparticle cohesion energy defined the thickness and physical/mechanical characteristics of the final aggregates/agglomerates in a nanocomposite. Though, the size and content of aggregates/agglomerates increased with the content of initially added nanoparticles. Consequently, the random orientation of each nanoparticle domain and formation of the polymer/particle interphase were proved to have determinative impacts on the mechanical properties of the system.

Formation of protein oleogels via capillary attraction of engineered protein particles

Edible oleogels have gained popularity as an approach for formulating food products, profiting from improving nutritional profiles related to health-related concerns, and playing an essential role in food processing. Protein oleogels provide an additional opportunity to load and deliver a high proportion of natural macronutrient in lipid-based food products. However, structuring oleogels with proteins directly were rarely reported, which has greatly limited their practical applications. Herein, we proposed a simple and robust method for structuring protein oleogels. By taking advantage of the improved interparticle cohesion through adding a much small amount of water (e.g., 2%) dispersed by ball milling, a space-spanning fractal network of engineered colloidal protein nanoparticles was formed, allowing for physically trapping the liquid oil into a self-standing gel-like system. Rheology and confocal laser microscopy imaging were adopted to investigate the viscoelasticity and microstructure of the resulting oleogels, showing that these capillary protein oleogels can be designed and fabricated with tunable properties upon water addition. Meanwhile, protein oleogels can be successfully formed by this approach, varying from proteins with different wettability, as well as oils differing in polarity. Overall, our findings raise the possibility of structuring protein oleogels with high operability and easy scale-up in practical applications.

On the Influence of Thermal Stratification on Emitted Dust Flux

AbstractThe influence of the atmospheric boundary layer (ABL) stability on dust emitted from saltation is usually neglected. This has been challenged by two recent studies which suggested a dependency of the dust emission flux particle size distribution (PSD) to the thermal stratification. Both studies observed a dust flux enrichment in fine particles with instability but for two different explanations: (a) a larger eddy diffusivity of submicron particles with instability, and (b) an enhanced turbulence and friction velocity u* stochasticity with instability, increasing saltation bombardment and fine‐dust emission. Here, we discuss and investigate these two propositions using the WIND‐O‐V (WIND erOsion in presence of sparse Vegetation's) 2017 data set. We first show that the first explanation and the observed stability effect on the dust flux are questionable. We, then, investigate the second explanation in the context of the enhanced influence of ABL‐scale motions on the near‐surface turbulence and u* stochasticity with increasing instability. This second explanation appears only possible at the transition between windy and free convection regimes where u* is close to its erosion threshold value. However, this intermediate regime appears more convective than the erosion event from whom the second explanation was proposed. Overall, our results show no thermal stability effect on the dust emission flux PSD. Instead, u* and the air relative humidity seem to be the main meteorological variables influencing the dust emission flux PSD. We, in particular, suggest that the air relative humidity may have affected the surface soil moisture, and thus the interparticle cohesion, through water vapor adsorption.