Equilibrium Particle Research Articles

Combustion of micron-sized iron particles in a drop tube reactor

Combustion of micron-sized particles of iron, a promising renewable alternative to fossil fuels, was investigated in a drop tube reactor (DTR) under overall lean conditions. A bimodal particle size distribution was observed after combustion: black micron-sized particles consisting of a mixture of iron oxides, with oxidation degrees ranging from 60% to 90%, and reddish fine particles of Fe2O3. The oxidation degree of the products showed no obvious variation with the reactor temperature. The coarse product particles were comparable in size with those of the raw iron particles, independent of temperature. The evaporation of iron represented a mass loss of 1%–2%. The primary nm-sized particles agglomerated to form aggregates of the order of 1μm. A simplified model for the combustion was used to analyze the results. It was based on the Particle Equilibrium Composition approach by van Gool et al. (Appl Energy Combust Sci 2023;13:100115) that assumes the oxidation from Fe to FeO to be limited by external diffusion and further oxidation by thermodynamic equilibrium. The model predicted larger oxidation degrees than observed experimentally. The difference was believed to be due mainly to stratification in the drop tube reactor, resulting in local fuel-rich conditions. The small impact of reactor temperature on the final oxidation stage indicated that diffusion limitations, rather than kinetic barriers, were rate controlling.

Natural zeolite/PVC beads for the removal of ammonium ions from water: Wettability, particle size, strength, hydrophilicity and equilibrium behaviour

This study developed an improved method for removing ammonium ions from water using natural zeolite/PVC beads. Research gaps relating to the impact of particle size, wettability, robustness, hydrophobicity and equilibrium behaviour were addressed. It was surmised that manipulation of the formation of natural zeolite/PVC beads will improve the performance of these composite materials. First it was noted that water-saturated sorbents exhibited higher ammonium ion exchange rates than dried beads. An air nozzle was proposed as a potential solution for controlling particle size. To control bead particle size, a range of airflow rates passed through an optimised 3D printed nozzle design. Bead diameters from below 0.5 mm up to 2 mm were obtained, with higher airflow rates promoting the growth of smaller beads. 0.5–1 mm beads also were characterised by lower attrition rates compared to larger ≈ 2.7 mm particles (54 to 57 % change) and had almost the same kinetics exchange rate as their regular unbound zeolite powder counterparts (0.4 to 13.5 % difference). The equilibrium data was in the shape of a linear isotherm, which suggested that the ammonium ions were equally dispersed throughout the sorbent and the aqueous solution. Finally, the use of amphipathic copolymer (Pluronic F127) improved the exchange kinetics of the dry beads (42 to 160 % change) but also weakened the structural integrity of the zeolite composites (284 to 647 % change depending on the analysed composites).

Triboplasma assisted chemical conversion in granular systems: a semi-analytic model

Abstract We present a semi-analytic model for a novel plasma-assisted chemical conversion pathway using triboplasmas generated in granular flows. Triboelectric charge relaxation is a well known phenomena where the potential generated from contact charging of particles exceeds the breakdown voltage of the background gas. In this work, we extend the triboelectric charge relaxation theory to include non equilibrium plasma energy and particle balance equations to predict the formation of dissociated and excited species that act as precursors to chemical conversion, for example in plasma-assisted ammonia synthesis. 
Our example case study with nitrogen background gas and Teflon/aluminum tribomaterial system yielded high excited nitrogen species densities per collision that are comparable to current plasma-assisted conversion pathways. We also present a regime diagram for various gases where Paschen breakdown parameters are used to determine whether triboplasmas can be formed for a given effective work-function difference between two materials. Our sensitivity studies indicate particle velocity, particle radius, solids fraction and space charge effects play a critical role in overall plasma densities and excited species production.

Efficient rare event sampling with unsupervised normalizing flows

From physics and biology to seismology and economics, the behaviour of countless systems is determined by impactful yet unlikely transitions between metastable states known as rare events, the study of which is essential for understanding and controlling the properties of these systems. Classical computational methods to sample rare events remain prohibitively inefficient and are bottlenecks for enhanced samplers that require prior data. Here we introduce a physics-informed machine learning framework, normalizing Flow enhanced Rare Event Sampler (FlowRES), which uses unsupervised normalizing flow neural networks to enhance Monte Carlo sampling of rare events by generating high-quality non-local Monte Carlo proposals. We validated FlowRES by sampling the transition path ensembles of equilibrium and non-equilibrium systems of Brownian particles, exploring increasingly complex potentials. Beyond eliminating the requirements for prior data, FlowRES features key advantages over established samplers: no collective variables need to be defined, efficiency remains constant even as events become increasingly rare and systems with multiple routes between states can be straightforwardly simulated.

Effect of ECAP and aging on microstructure of an Al-Cu-Mg-Si alloy

The effect of equal-channel-angular pressing (ECAP) on the microstructure and precipitation of an Al-4.7Cu-0.74 Mg-0.51Si-0.48Mn-0.10Cr-0.09Ti-0.02Fe (all wt%) has been studied using aberration-corrected scanning transmission electron microscopy. The ECAP followed by a short-term aging provides a superior combination of strength and ductility in the present alloy. The ECAPed alloy shows a substantially different precipitation behavior in the deformation bands (DBs) compared to extended regions (ERs) during aging. The relatively coarse particles of the equilibrium θ (Al2Cu) and β (Mg2Si) phases were found to form along deformation-induced grain/subgrain boundaries within the DBs after short-term aging. In the present alloy after ECAP and aging, the phases continuously decorating dislocation lines or forming the discrete particles in the ERs are similar to those in the bulk matrix after conventional aging. The macroscopic strengths have been estimated for the ERs and DBs in the samples after ECAP and aging. The former, i.e., ERs, with predominant strengthening contributions originating from solid solution, precipitation and dislocations, is likely have a higher YS than the latter with the relatively coarse equilibrium particles and mainly strengthened by only grain boundaries and dislocations.

A correlation-based approach for fast prediction of the equilibrium position of particles within a spiral microchannel

ABSTRACT As inertial microfluidics is a proven technique for manipulating particles within microchannels, a deep understanding of hydrodynamics forces acting on particles in these systems is crucial for optimal manipulation. However, existing numerical techniques for examining particle equilibrium positions are often time-intensive and require high-memory systems, limiting accessibility due to complexity and cost. To address this issue, this study proposes a method to develop a correlation for fast estimation of particle equilibrium positions. An algorithm is devised to develop the correlation in three main steps: first, a dataset is created by conducting simulations using the finite element method, considering width, height, flow rate, particle size, and curvature radius. The computed distance between the equilibrium position of the particle and the inner channel wall serves as input for the next step where a general form of the correlation is established using Buckingham’s Π-theorem. The unknown coefficients of the correlation are calculated using 80 percent of the dataset from the first step and the least sum squares errors method. Finally, the obtained correlation is validated using the remaining data and previous experimental studies. The proposed correlation reduces the computational burden associated with predicting particle focus positions, with a 3.7 percent mean absolute error.

Bioderived Thiol-Ene Emulsion Polymerization for Hybrid Latex Particles.

The thiol-ene emulsion polymerization of three dienes synthesized from bioderived compounds, and subsequent preparation of core-shell polymer latexes, is reported. Levoglucosan (LGA), levogucosenone (LGO) and isosorbide were first modified with 4-pentenoic acid to install polymerizable groups. These monomers were used along with a dithiol to prepare poly(thioether) particles via ab initio emulsion polymerization using potassium persulfate as initiator and sodium dodecyl sulfate as surfactant. The structure of the diene significantly influenced the size of the resulting polymer latex particles. Given their low glass transition temperature, the LGA-derived poly(thioether) particles were used as a seed for the seeded emulsion polymerization of either styrene or methyl methacrylate. Core-shell latex particles with a high Tg core and a low Tg bioderived shell were formed, as verified by electron microscopy and in agreement with theoretical predictions of the equilibrium particle morphology based on the interfacial tensions of each particle phase.

Radial dependence of ionization clustering around a gold nanoparticle irradiated by X-rays under charged particle equilibrium

Objective.This work explores the enhancement of ionization clustering and its radial dependence around a gold nanoparticle (NP), indicative of the induction of DNA lesions, a potential trigger for cell-death.Approach.Monte Carlo track structure simulations were performed to determine (a) the spectral fluence of incident photons and electrons in water around a gold NP under charged particle equilibrium conditions and (b) the density of ionization clusters produced on average as well as conditional on the occurrence of at least one interaction in the NP using Associated Volume Clustering. Absorbed dose was determined for comparison with a recent benchmark intercomparison. Reported quantities are normalized to primary fluence, allowing to establish a connection to macroscopic dosimetric quantities.Main results.The modification of the electron spectral fluence by the gold NP is minor and mainly occurs at low energies. The net fluence of electrons emitted from the NP is dominated by electrons resulting from photon interactions. Similar to the known dose enhancement, increased ionization clustering is limited to a distance from the NP surface of up to200nm. The number of clusters per energy imparted is increased at distances of up to150nm, and accordingly the enhancement in clustering notably surpasses that of dose enhancement. Smaller NPs cause noticeable peaks in the conditional frequency of clusters between50nm-100nmfrom the NP surface.Significance.This work shows that low energy electrons emitted by NPs lead to an increase of ionization clustering in their vicinity exceeding that of energy imparted. While the electron component of the radiation field plays an important role in determining the background contribution to ionization clustering and energy imparted, the dosimetric effects of NPs are governed by the interplay of secondary electron production by photon interaction and their ability to leave the NP.

Equilibrium and self-assembly of Janus particles at liquid-liquid interfaces for the film formation

This article investigates the equilibrium arrangement, self-assembly process, and subsequent curing of amphiphilic snowman-shaped Janus particles at the oil-water interface. The independent Janus particles are in vertical equilibrium state and the contact position of the oil-water interface is at the largest cross section of the particle’s hydrophobic phase. Under the effect of the surface tension and the adsorption of materials, Janus particles may form particle combinations including the particle pairs and the particle triangle, whose inner and outer sides have the liquid surface exhibiting completely opposite contact angles. Particle combinations form stable parallel double-chain structures with diverse shapes after the self-assembly process. However, the single Janus particles attain a state of mechanical equilibrium under the influence of surrounding particles, enabling them to assemble into regular array structures. The relationship of interfacial tension coefficient between phases can be changed by adjusting the oil-water system, which leads to variations in the self-assembly speed and the final arrangement results. The thin-film with uniformly distributed vertical particles is achieved by replacing the underlying deionized water with a curing agent. Based on the understanding of the interactions between irregularly shaped Janus particles at the oil-water interface, it will be convenient to achieve the controllable self-assembly and widely applications of these particles.

Full counting statistics of 1d short range Riesz gases in confinement

We investigate the full counting statistics of a harmonically confined 1d short range Riesz gas consisting of N particles in equilibrium at finite temperature. The particles interact with each other through a repulsive power-law interaction with an exponent k > 1 which includes the Calogero–Moser model for k = 2. We examine the probability distribution of the number of particles in a finite domain [−W,W] called number distribution, denoted by N(W,N) . We analyze the probability distribution of N(W,N) and show that it exhibits a large deviation form for large N characterized by a speed N3k+2k+2 and by a large deviation function (LDF) of the fraction c=N(W,N)/N of the particles inside the domain and W. We show that the density profiles that create the large deviations display interesting shape transitions as one varies c and W. This is manifested by a third-order phase transition exhibited by the LDF that has discontinuous third derivatives. Monte–Carlo simulations based on Metropolis–Hashtings (MH) algorithm show good agreement with our analytical expressions for the corresponding density profiles. We find that the typical fluctuations of N(W,N) , obtained from our field theoretic calculations are Gaussian distributed with a variance that scales as Nνk , with νk=(2−k)/(2+k) . We also present some numerical findings on the mean and the variance. Furthermore, we adapt our formalism to study the index distribution (where the domain is semi-infinite (−∞,W]) , linear statistics (the variance), thermodynamic pressure and bulk modulus.

Study of particle equilibrium based on the combination of light-actuated AC electroosmosis and light-actuated dielectrophoresis.

Optoelectronic tweezers (OETs) represent a flexible, high-throughput method for manipulating micro/nano particles or cells. This technique involves not only light-actuated dielectrophoresis (LDEP) but also light-actuated AC electroosmosis (LACE), which occurs concurrently in OETs devices. Despite this, the combination of negative LDEP and LACE has been relatively unexplored in previous research. To this end, particle equilibrium in OETs devices under the combined influence of negative LDEP and LACE was hereby proposed for what we believe is the first time. The findings revealed that particles experiencing negative dielectrophoresis encountered opposing forces from LDEP and LACE, reaching equilibrium near the light pattern. The location of the equilibrium point was frequency-dependent. The research further demonstrated the rapid differentiation between individual particles and adherent particles by leveraging the distinct equilibrium point positions. These phenomena were corroborated through numerical simulations, which showed a strong correlation between the theoretical analysis results and the experimental data. Overall, the particle equilibrium phenomenon in OET systems exhibits high stability and holds promising potential for future applications in particle or cell sorting and patterning two-dimensional structures.

Thermalization and Hydrodynamics in an Interacting Integrable System: The Case of Hard Rods

We consider the relaxation of an initial non-equilibrium state in a one-dimensional fluid of hard rods. Since it is an interacting integrable system, we expect it to reach the Generalized Gibbs Ensemble (GGE) at long times for generic initial conditions. Here we show that there exist initial conditions for which the system does not reach GGE even at very long times and in the thermodynamic limit. In particular, we consider an initial condition of uniformly distributed hard-rods in a box with the left half having particles with a singular velocity distribution (all moving with unit velocity) and the right half particles in thermal equilibrium. We find that the density profile for the singular component does not spread to the full extent of the box and keeps moving with a fixed effective speed at long times. We show that such density profiles can be well described by the solution of the Euler equations almost everywhere except at the location of the shocks, where we observe slight discrepancies due to dissipation arising from the initial fluctuations of the thermal background. To demonstrate this effect of dissipation analytically, we consider a second initial condition with a single particle at the origin with unit velocity in a thermal background. We find that the probability distribution of the position of the unit velocity quasi-particle has diffusive spreading which can be understood from the solution of the Navier–Stokes (NS) equation of the hard rods. Finally, we consider an initial condition with a spread in velocity distribution for which we show convergence to GGE. Our conclusions are based on molecular dynamics simulations supported by analytical arguments.

Investigation of triaxial cables and microdetectors in small field dosimetry

Background. Small field dosimetry presents unique challenges with source occlusion, lateral charged particle equilibrium and detector size. As detector volume decreases, signal strength declines while noise increases, deteriorating the signal-to-noise ratio (SNR). This issue may be compounded by triaxial cables connecting detectors to electrometers. However, effects of cables, critical for precision dosimetry, are often overlooked. There is a need to evaluate triaxial cable and detector impacts on SNR in small fields. The purpose of this study is to evaluate the influence of triaxial cables and microdetectors on signal-to-noise ratios in small-field dosimetry. This study also aims to establish the importance of cable quality assurance for measurement accuracy. Methods. Six 9.1 m length triaxial cables from different manufacturers were tested with six microdetectors (microDiamond, PinPoint, EDGE, Plastic scintillator, microSilicon, SRS-Diode). A 6 MV photon beam (TrueBeam) was used, with a water phantom at 5 cm depth with 0.5 × 0.5 cm2 to 10 × 10 cm2 fields at 600 MU min−1. Readings were acquired using cable-detector permutations with a dedicated electrometer (except the scintillator which has its own). Cables had differing connector types, conductor materials, insulation, and diameters. Detectors had various sensitive volumes, materials, typical signals, and bias voltages. Results. Normalized field output correction factors (FOFs) relative differences of 13.4% and 4.6% between the highest and lowest values across triaxial cables for 0.5 × 0.5 cm2 and 1 × 1 cm2 fields, respectively. The maximum difference in FOF between any cable-detector combinations was 0.2% for the smallest field size. No consistent FOF trend was observed across all detectors when increasing cable diameter. Additionally, the non-normalized FOF differences of 0.9% and 0.3% were observed between cables for 0.5 × 0.5 cm2 and 1 × 1 cm2 fields, respectively. Conclusions. Regular triaxial cable quality assurance is critical for precision small field dosimetry. A national protocol is needed to standardize cable evaluations/calibrations, particularly for small signals (<pC) from modern detectors. This could enhance measurement accuracy and treatment delivery with advanced small-field radiotherapy techniques that promise improved patient outcomes. Further studies should expand detector and cable models tested across institutions to establish robust quality control guidelines.

The response of radiation detectors in modulated fields for small targets

Intensity-modulated delivery techniques in radiotherapy are advanced methods that use the superposition of small fields to create complex dose distributions. These techniques result in intense gradients and inhomogeneous dose regions, making the dosimetry of composite fields challenging, especially when the sub-fields superposition does not restore charged particle equilibrium. This work aims to address the response of radiation detectors in non-equilibrium conditions. Two ionization chambers and a micro-diamond detector were irradiated using composite fields from VMAT plans with spherical targets with diameters ranging from 0.5 to 8 cm. The radiation detectors' response and the dose delivered by the VMAT plans were measured using a plastic scintillator detector and radiochromic film as reference detectors. It was observed that an under-response of the ionization chambers was up to 13% and an over-response of the micro-diamond detector was up to 2.5%. Additionally, output correction factors were derived and used to measure the absorbed dose in composite plans using the radiation detectors. The measured dose was compared with that measured with radiochromic film. A dose difference was found within radiochromic film uncertainties (<2.5%). The results of this work suggest that radiation detectors require output correction factors when non-equilibrium conditions persist in composite fields. However, a link between static and composite fields could not be established because the field size cannot be determined accurately.

Study on the variation regularities of minimum explosion concentration of moist magnesium dust/derived hydrogen hybrids under multiple working conditions

Magnesium is widely used but often accompanied by frequent magnesium powder explosion accidents. If the variation regularity and mechanism of the minimum explosion concentration (cm) of magnesium powder under the multi-factor coupling effect can be understood, the occurrence of magnesium powder explosion accidents can be fundamentally avoided, and intrinsic safety can be achieved. In this paper, experiments were conducted using a self-made 20 L explosion device to explore the effects of particle size, initial temperature, and equilibrium relative humidity (ERH) coupling on the cm of magnesium powder. The study found that an increase in ERH of moist magnesium powder would lead to easier agglomeration of the dust, making it less prone to activation. Additionally, excessive moisture also absorbed more heat, reducing the ignition sensitivity of the dust cloud and resulting in a continuous increase in cm. However, increasing the initial temperature and decreasing the dust particle size both decreased the cm of moist magnesium powder, weakening the effect of ERH on cm. Furthermore, using the analysis methods of orthogonal experimental range and AHP model, it was determined that the influence weights of the factors coupling effects on the cm of magnesium powder, from highest to lowest weight, were: particle size > ERH > initial temperature.Furthermore, in order to deeper understand the mechanism of the action process that affect the cm of moist magnesium powder, additional experiments were conducted to further confirm that the addition of hydrogen derived from the erosion reaction of moist magnesium powder to the explosion system can reduce the cm of magnesium dust clouds. Moreover, a quantitative mathematical model for predicting the cm of magnesium powder/hydrogen two-phase system was also established.

IDENTIFICATION OF THE INTERACTION OF LITHIUM HEXAFLUOROPHOSPHATE SALT AND ETHYLENE CARBONATE (EC) SOLVENT IN LITHIUM ION BATTERY REDOX EVENTS USING CLASSICAL MOLECULAR DYNAMICS (MD) SIMULATION

The aim of the research is to find the maximum velocity possessed by the molecules (Maxwell velocity distribution) of the solvation event of lithium hexafluorophosphate salt interacting with ethylene carbonate (EC) solvent. We examined the electrolyte simulation of the reaction between lithium ions and hexafluorophosphate with ethylene carbonate (EC) solvent while the potential involved is the Lennard Jones potential. We use the epsilon (ε) and sigma (σ) parameters of Lennard Jones. These parameters are the independent variables used as a reference in determining the response variable which is the velocity of the molecules. Due to the large number of molecules involving the parameters and response variables per molecule mentioned above, we use a microcanonical assembly system (N, V, E) where the number of particles (N), system volume (V) and energy (E) are constant. The energy kT and the distance between molecules σ of 1 are inputted to the program in order to facilitate the computer in the simulation process. Solvation events where litium hexafluorophosphate salt and solvent ethylene carbonate interact then in the final positions of particles (equilibrium) the result is almost symmetry randomly in all planes. The velocity used is the most frequent velocity ( ) and is related to the kinetic energy.

Evaluation of radiation detectors for the determination of field output factors in Leksell Gamma Knife dosimetry using 3D printed phantom inserts

The Leksell Gamma Knife® Perfexion™ and Icon™ have a unique geometry, containing 192 60Co sources with collimation for field sizes of 4 mm, 8 mm, and 16 mm. 4 mm and 8 mm collimated fields lack lateral charged particle equilibrium, so accurate field output factors are essential. This study performs field output factor measurements for the microDiamond, microSilicon, and RAZOR™ Nano detectors.3D printed inserts for the spherical Solid Water® Phantom were fabricated for microDiamond detector, the microSilicon unshielded diode and the RAZOR™ Nano micro-ionisation chamber. Detectors were moved iteratively to identify the peak detector signal for each collimator, representing the effective point of measurement of the chamber.In addition, field output correction factors were calculated for each detector relative to vendor supplied Monte Carlo simulated field output factors and field output factors measured with a W2 scintillator. All field output factors where within 1.1 % for the 4 mm collimator and within 2.3 % for the 8 mm collimator.The 3D printed phantom inserts were suitable for routine measurements if the user identifies the effective point of measurement, and ensures a reproducible setup by marking the rotational alignment of the cylindrical print. Measurements with the microDiamond and microSilicon can be performed faster compared to the RAZOR™ Nano due to differences in the signal to noise ratio. All detectors are suitable for field output factor measurements for the Leksell Gamma Knife® Perfexion™ and Icon™.

Simulated phase state and viscosity of secondary organic aerosols over China

Abstract. Secondary organic aerosols (SOAs) can exist in liquid, semi-solid, or amorphous solid states. Chemical transport models (CTMs), however, usually assume that SOA particles are homogeneous and well-mixed liquids, with rapid establishment of gas–particle equilibrium for simulations of SOA formation and partitioning. Missing the information of SOA phase state and viscosity in CTMs impedes accurate representation of SOA formation and evolution, affecting the predictions of aerosol effects on air quality and climate. We have previously developed a parameterization to estimate the glass transition temperature (Tg) of an organic compound based on volatility and to predict viscosity of SOA. In this study, we apply this method to predict the phase state of SOA particles over China in summer of 2018 using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem). The simulated Tg of dry SOA (Tg,org) agrees well with the value estimated from ambient volatility measurements at an urban site in Beijing. For the spatial distributions of Tg,org, simulations show that at the surface the values of Tg,org range from ∼287 to 305 K, with higher values in northwestern China, where SOA particles have larger mass fractions of low-volatility compounds. Considering water uptake by SOA particles, the SOA viscosity shows a prominent geospatial gradient in which highly viscous or solid SOA particles are mainly predicted in northwestern China. The lowest and highest SOA viscosity values both occur over the Qinghai–Tibet Plateau, where the solid phase state is predicted over dry and high-altitude areas and the liquid phase state is predicted mainly in the south of the plateau with high relative humidity during the summer monsoon season. Sensitivity simulations show that, including the formation of extremely low-volatility organic compounds, the percent time that a SOA particle is in the liquid phase state decreases by up to 12 % in southeastern China during the simulated period. With an assumption that the organic and inorganic compounds are internally mixed in one phase, we show that the water absorbed by inorganic species can significantly lower the simulated viscosity over southeastern China. This indicates that constraining the uncertainties in simulated SOA volatility distributions and the mixing state of the organic and inorganic compounds would improve prediction of viscosity in multicomponent particles in southeastern China. We also calculate the characteristic mixing timescale of organic molecules in 200 m SOA particles to evaluate kinetic limitations in SOA partitioning. Calculations show that during the simulated period the percent time of the mixing timescale longer than 1 h is &gt;70 % at the surface and at 500 hPa in most areas of northern China, indicating that kinetic partitioning considering the bulk diffusion in viscous particles may be required for more accurate prediction of SOA mass concentrations and size distributions over these areas.

Measuring forces in a 2D multi-contact system using the virtual fields method: Principle, simulations and experimental application to a three-particle system

This paper proposes an experimental approach to measure contact forces in a two-dimensional system composed of cylindrical particles using the Virtual Fields Method (VFM). This identification method relies on the knowledge of the strain distribution in the particles forming the discrete medium. Synthetic strain data provided by a finite element model (with added noise) were first used as input data for the identification procedure. It is shown that if the mechanical response of the constitutive material is known, the contact forces applied to a particle can be identified, since they are proportional to a weighted average of the strain components, the weights being the virtual strain components. Various strategies were tested to propose kinematically admissible fields for the virtual displacement. Identification technique robustness was studied with respect to various sources of error, such as noise in the strain field, missing data along the boundaries, and a possible spurious shift between real and virtual fields. An experimental application was then performed on a three-particle system subjected to confined compression by processing strain maps obtained using Localized Spectrum Analysis (LSA) for each particle. In addition to the VFM equations, particle equilibrium and Newton's third law of motion were taken into account to propose a relevant strategy for processing the experimental data. The results open up prospects for applications to granular materials composed of numerous particles.

Efficient composite dispersants for high solid content, low viscosity nano-zirconia slurries: An experimental and molecular dynamics simulation study

An effective dispersant is essential for creating a high-quality water-based ceramic suspension. When the solid content of the slurry is high, a single dispersant proves inadequate. This study proposes a strategy for producing nano-YSZ (yttria-stabilized zirconia) ceramic slurries with high solid content and low viscosity using compound dispersants ammonium polyacrylate (PAANH4) and fructose. The efficacy of dispersion is evaluated through rheological experiments and zeta potential analysis. The optimal dispersant effect is achieved when the compound dispersants are added in the following proportions: PAANH4 = 0.5 wt% and fructose = 5 wt%. Consequently, the viscosity of the nano-YSZ slurry, with a solid content of 50 vol%, is reduced to 696 mPa·s at a shear rate of 100 s−1. Both PAANH4 and fructose effectively lower the slurry’s viscosity via two separate mechanisms: electrostatic-steric stabilization and increasement of free water content. Molecular dynamics (MD) simulation was utilized to examine the nanoparticle dispersion process. The results show that after adding dispersants, the distance between two equilibrium particles is 4 nm, and the potential mean force curve displays a clear energy barrier. This provides a new method for investigating the dispersion effects of dispersants.