Interparticle Interaction Energy Research Articles

Pore-scale behaviors of CO2 hydrate formation and dissociation in the presence of swelling clay: Implication for geologic carbon sequestration

Hydrate-based CO2 sequestration (HBCS) under seafloor with huge storage capacity and long-term mechanical stability is attractive for large-scale carbon reduction. However, as representative geochemical constituents of marine sediments, swelling clay minerals still play ambiguous roles in hydrate phase transition and sedimentary structure stability. In this study, pore-scale behaviors of hydrate deposition and reservoir structure evolution in the presence of montmorillonite (MMT), a representative swelling clay, was investigated using low-field nuclear magnetic resonance (LNMR) technique. Total inter-particle interaction energy of 195.4 KbT ensured the dispersion of clay in 0.5 wt% MMT system, which facilitated homogeneous hydrate formation by providing nucleation sites and surface electric fields, improving hydrate conversion from 78.2 % to 89.6 %. Weak water activity caused by strong water absorption of swelling clay resulted in a 14.4 % reduction in CO2 storage capacity of high-concentration (10.0 wt%) MMT reservoir. Hydrate phase transition accompanied by the migration of MMT particles and liquid water synergistically contributed to sedimentary structure evolution. Migration of MMT-rich fluid with high viscosity could cause irreversible geologic damages by exacerbating sedimentary skeleton deformation. This work reveals the interaction between swelling clay and CO2 hydrate at microscopic scale, providing new perspectives for effective implementation of CO2 geologic sequestration in marine sediments.

Nanoscale Porosity in Microellipsoids Cloaks Interparticle Capillary Attraction at Fluid Interfaces.

Anisotropic particles pinned at fluid interfaces tend toward disordered multiparticle configurations due to large, orientationally dependent, capillary forces, which is a significant barrier to exploiting these particles to create functional self-assembled materials. Therefore, current interfacial assembly methods typically focus on isotropic spheres, which have minimal capillary attraction and no dependence on orientation in the plane of the interface. In order to create long-range ordered structures with complex configurations via interfacially trapped anisotropic particles, control over the interparticle interaction energy via external fields and/or particle engineering is necessary. Here, we synthesize colloidal ellipsoids with nanoscale porosity and show that their interparticle capillary attraction at a water-air interface is reduced by an order of magnitude compared to their smooth counterparts. This is accomplished by comparing the behavior of smooth, rough, and porous ellipsoids at a water-air interface. By monitoring the dynamics of two particles approaching one another, we show that the porous particles exhibit a much shorter-range capillary interaction potential, with scaling intriguingly different than theory describing the behavior of smooth ellipsoids. Further, interferometry measurements of the fluid deformation surrounding a single particle shows that the interface around porous ellipsoids does not possess the characteristic quadrupolar symmetry of smooth ellipsoids, and quantitatively confirms the decrease in capillary interaction energy. By engineering nanostructured surface features in this fashion, the interfacial capillary interactions between particles may be controlled, informing an approach for the self-assembly of complex two-dimensional microstructures composed of anisotropic particles.

Exploring new solvent mixtures for near-net shaping of Ultra-High Temperature Ceramics via colloidal processing

Suspensions of Ultra-High Temperature Ceramic (UHTC) powder with various organic solvents and co-solvent mixtures were prepared with the intention of verifying and understanding the relationship between interparticle interactions, flow behavior, and resulting particle packing. These relationships can be used to predict optimal solvent choices in colloidal processing of UHTCs to guarantee suspension stability through an adequate balance of the interparticle forces in suspension. Four organic solvents were selected: cyclohexane (CYC), tetrahydrofuran (THF), acetone (ACE) and N,N-dimethylformamide (DMF). The theoretical performance of each suspension, based on interparticle interaction energies, was compared to the empirical results. Detailed flow behavior was studied through rheological measurements and particle packing was measured by Archimedes’ method. The relationship between interparticle forces, viscosity and particle packing is discussed. Other contributing factors such as the performance of the dispersing agent were also considered and surface characteristics were reported using X-ray Photoelectron Spectroscopy (XPS), providing a modification to the adsorption parameter in the repulsive model. Low viscosity slurries were obtained at approximately 40% solid loading. CYC and THF demonstrated the ability to be effective co-solvents and produce the highest suspension stability with 100% CYC. These findings will help to produce UHTC complex shape component with minimal flaws during processing that can withstand extreme, high temperature oxidizing environments after densification.

Stability of Detonation Nanodiamond Colloid with Respect to Inorganic Electrolytes and Anionic Surfactants and Solvation of the Particles Surface in DMSO–H2O Organo-Hydrosols

In this article, the stability of sols of detonated nanodiamonds, DND, with positively charged colloidal particles, is studied in different salt solutions in water–dimethyl sulfoxide (DMSO) binary systems containing 95 vol.% organic solvent. Additionally, several CCC values are determined in 95 vol.% acetonitrile for comparison. The critical coagulation concentrations (CCC) are determined using the dynamic light scattering technique and the Fuchs function. As coagulators, NaCl, NaBr, NaNO3, NaClO4, Nan-C8H17SO3, and Nan-C12H25OSO3 are used. Comparison of the CCC values in DMSO–H2O and CH3CN–H2O with those obtained in water allows us to make some conclusions. The variations of these values in different solvents are explained in terms of good and poor interfacial solvation of colloidal particles, “structural” contribution to the interparticle interaction energy, lyotropic series for anions, and more or less pronounced adsorption of surfactants. The study of the stability of DND hydrosol in solutions of anionic surfactants with different hydrocarbon tail length demonstrated the crucial role of adsorption in the coagulation process.

Excitations of a Bose-Einstein condensate and the quantum geometry of a flat band

The quantum geometry of Bloch states fundamentally affects a wide range of physical phenomena. The quantum Hall effect, for example, is governed by the Chern number, and flat-band superconductivity by the distance between the Bloch states: the quantum metric. While understanding quantum geometry phenomena in the context of fermions is well established, less is known about the role of quantum geometry in bosonic systems where particles can undergo Bose-Einstein condensation (BEC). In conventional single-band or continuum systems, excitations of a weakly interacting BEC are determined by the condensate density and the interparticle interaction energy. In contrast to this, we discover here fundamental connections between the properties of a weakly interacting BEC and the underlying quantum geometry of a multiband lattice system. We show that, in the flat-band limit, the defining physical quantities of BEC, namely, the speed of sound and the quantum depletion, are dictated solely by the quantum geometry. We find that the speed of sound becomes proportional to the quantum metric of the condensed state. Furthermore, the quantum distance between the Bloch functions forces the quantum depletion and the quantum fluctuations of the density-density correlation to obtain finite values for infinitesimally small interactions. This is in striking contrast to dispersive bands where these quantities vanish with the interaction strength. Additionally, we show how in the flat-band limit the supercurrent is carried by the quantum fluctuations and is determined by the Berry connections of the Bloch states. Our results reveal how nontrivial quantum geometry allows reaching strong quantum correlation regime of condensed bosons even with weak interactions. This is highly relevant, for example, for polariton and photon BECs where interparticle interactions are inherently small. Our predictions can be experimentally tested with flat-band lattices already implemented in ultracold gases and various photonic platforms.

Effect of ion type and concentration on rheological properties of natural sodium bentonite dispersions at low shear rates

Understanding the behavior of bentonite dispersions is of remarkable importance in many industrial and engineering applications. Dispersion behavior depends on interparticle interactions. These mechanisms are influenced by the volumetric content of solid particles, ionic concentration in suspending fluid, ion valence, and pH. In this research, natural sodium bentonite dispersions were analyzed. Tests were performed in dispersions prepared with different volumes of particles in solutions of sodium chloride, calcium chloride, and magnesium sulphate with different concentrations. The rheology of dispersions was analyzed by fitting three rheological models, namely the power law, Bingham plastic, and Herschel-Bulkley models. Changes in shear stress and model parameters with ionic strength were analyzed. The observed behavior was interpreted in terms of particle-particle association and was later confirmed by computing the Derjaguin, Landau, Verwey and Oberbeek (DLVO) interparticle interaction energy. Finally, electroviscous effects were analyzed by computing the importance of the electroviscous parameter considering Einstein's equation and the Dougherty-Krieger equation. The electroviscous parameter was found to decrease with the increase in ionic concentration. The influence of ion type had a negligible effect on the electroviscous parameter.

Fast quantum driving in two-level systems with interaction and nonlinear sweep

We investigate high-fidelity fast quantum driving in a generalized nonlinear two-level system with both interparticle interaction and nonlinear energy sweep. We find that fast quantum dynamics depend on the interaction, energy sweep parameter, and energy sweep strength. We show that the driving protocol for a large energy sweep parameter reaches a given final high fidelity in a shorter time. The interparticle interaction can influence the quantum driving dynamics and can even break the quantum speed limit of the linear model. For the attractive interaction, the minimal time decreases monotonically as energy sweep strength increases, while it increases for the repulsive interaction. We also study a critical behavior and obtain analytical expressions of a critical interaction or a critical sweep strength, beyond which the target state cannot be achieved with high fidelity.

The effect of simple electrolytes on coagulation of hydrosols of monodisperse negatively charged detonation nanodiamond

The influence of the concentration of potassium and barium chlorides on the aggregation stability of a hydrosol of monodisperse negatively charged detonation nanodiamond with particle sizes of 4−5 nm obtained by annealing of its agglomerates in air has been studied by turbidimetry. The experimental results have been discussed within the classical and generalized Derjaguin−Landau−Verwey−Overbeek theories. The analysis of the pair interaction potentials calculated for ultradispersed particles of detonation nanodiamond has led to the conclusion that the coagulation occurs by the barrier mechanism in the primary potential minimum. It has been assumed that the structural component of the interparticle interaction energy contributes to the total balance of the surface forces.

Determination of Blocking Temperature in Magnetization and Mössbauer Time Scale: A Functional Form Approach

We studied the temperature dependence of the magnetization in an ensemble of monodomain nanoparticles both with dc magnetometry and Mossbauer spectroscopy. The analytical form of the temperature dependence is given by the complementary cumulative distribution function. This allows to determine the magnetization blocking temperatures of the sample by a fitting procedure. It is possible to calculate the Mossbauer blocking temperature by a single spectrum and the dc magnetization blocking temperature by two points of the thermoremanent magnetization curve, thus with a large reduction of the experimental work. The method may be used for particles with not too strong interactions, such happens in the Fe28 sample and not for samples with strong interactions as N30; it may be used for interparticle interaction energies up to 2 yJ and not for energies larger than 60 yJ. This method of analysis of the data should be used in the future work concerning the thermoremanent magnetization and Mossbauer spectra of magnet...

Thermodynamic equivalence of two-dimensional imperfect attractive Fermi and repulsive Bose gases

We consider two-dimensional imperfect attractive Fermi and repulsive Bose gases consisting of spinless point particles whose total interparticle interaction energy is represented by $a{N}^{2}/2V$ with $a=\ensuremath{-}{a}_{F}\ensuremath{\le}0$ for fermions and $a={a}_{B}\ensuremath{\ge}0$ for bosons. We show that, in spite of the attraction, the thermodynamics of a $d=2$ imperfect Fermi gas remains well defined for $0\ensuremath{\le}{a}_{F}\ensuremath{\le}{a}_{0}={h}^{2}/2\ensuremath{\pi}m$, and is exactly the same as the one of the repulsive imperfect Bose gas with ${a}_{B}={a}_{0}\ensuremath{-}{a}_{F}$. In particular, for ${a}_{F}={a}_{0}$ one observes the thermodynamic equivalence of the attractive imperfect Fermi gas and the ideal Bose gas.

Self-assembly of colloids with magnetic caps

In our earlier work (Steinbach et al., 2016 [1]) we investigated a homogeneous system of magnetically capped colloidal particles that self-assembled via two structural patterns of different symmetry. The particles could form a compact, equilateral triangle with a three-fold rotational symmetry and zero dipole moment and a staggered chain with mirror symmetry with a net magnetisation perpendicular to the chain. The system exhibited a bistability already in clusters of three particles. Based on observations of a real magnetic particles system, analytical calculations and molecular dynamics simulations, it has been shown that the bistability is a result of an anisotropic magnetisation distribution with rotational symmetry inside the particles. The present study is a logical extension of the above research and forms a preparatory stage for the study of a self-assembly of such magnetic particles under the influence of an external magnetic field. Since the magnetic field is only an additive contribution to the total ground state energy, we can study the interparticle interaction energies of candidate ground state structures based on the field-free terms.

Investigation of nanoparticle agglomerates properties using Monte Carlo simulations

By accounting for realistic interparticle interaction energy of fine dry nanoparticles, an off-lattice Monte Carlo (MC) simulation approach is used to gain insight into such properties of agglomerates of nanoparticles with primary sizes ranging from 10nm to 100nm. This novel numerical approach allows for assessment of the mechanical properties and morphological features of the agglomerates. An interesting outcome is that the fractal dimension depends on the material properties represented via interaction energy. The agglomerate porosity increases with increasing agglomerate mass and may approach unity. With increasing Hamaker constant and fixed particle size, the agglomerates are characterized by a lower fractal dimension, higher packing porosity, higher mechanical strength, larger agglomeration size, and lower crystalline fraction. For a fixed Hamaker constant, agglomerates of the smaller primary particles exhibit a more compact packing structure, higher mechanical strength, smaller agglomerate size, and higher crystalline fraction. The local structure analysis indicates that for a fixed Hamaker constant, there are more particles in crystalline structure within the agglomerates constituted by the smaller primary particles. Likewise, for a fixed primary particle size, a lower Hamaker constant allows particles to configure into more stable agglomerate structures, thus providing useful insights into agglomerate morphology.

Influence of Y and La substitution on particle size, structural and magnetic properties of nanosized nickel ferrite prepared by using citrate precursor method

The compounds with the formulas NiFe2O4, NiFe1.9Y0.1O4 and NiFe1.9La0.1O4 were prepared by citrate precursor method and followed by heat treatment in air at 600 °C for 5 h. Crystal structure, valence state, chemical bonding and composition of the samples were studied rigorously by XRD, SXRD, XANES, FTIR and ICP–AES. Rietveld refinement of XRD and SXRD patterns reveals that the samples crystallize in single spinel phase with almost inverted structure in which the substituted ions Y3+ and La3+ locate in the octahedral sites and about ten percents of nickel atoms were found at the tetrahedral sites. Morphology and particle size were studied by SEM and TEM. The results show that the samples are composed of clustered nanoparticles with mean particle size decreases approximately from 20 nm in NiFe2O4 sample to 10 nm in the substituted ones. The magnetic measurements were carried out by means of a VSM. Spontaneous magnetization, magnetic coercivity, Curie temperature, superparamagnetic transition temperature, interparticle interaction energy and effective anisotropy were determined and explained on the basis of the surface and finite–size effects and cation distribution.

Formula for determining the surface temperature of the fullerite consisting of a C60-C70 mixture from a mass spectrum

A calculation is used to show that the kinetic energy of particles in the sublimation flux of the fullerite consisting of a mixture of C60 and C70 that is caused by a pulsed laser beam is significantly higher than the interparticle interaction energy, i.e., kT ≫ E. This finding is used to deduce a formula to determine the fullerite surface temperature from mass spectrum data on the basis of gas-kinetic equations and the data obtained by the Knudsen method for a fullerene effusion flux. The calculated and experimental results are compared. Specific features are noted for the procedure of measuring the temperature. Examples for calculating the surface temperature for other heating methods are given.

Correlation of superparamagnetic relaxation with magnetic dipole interaction in capped iron-oxide nanoparticles

Six nanometer sized iron-oxide nanoparticles capped with an organic surfactant and/or silica shell of various thicknesses have been synthesized by a microemulsion method to enable controllable contributions of interparticle magnetic dipole interaction via tunable interparticle distances. Bare particles with direct surface contact were used as a reference to distinguish between interparticle interaction and surface effects by use of Mössbauer spectroscopy. Superparamagnetic relaxation behaviour was analyzed by SQUID-magnetometry techniques, showing a decrease of the blocking temperature with decreasing interparticle interaction energies kBT0 obtained by AC susceptibility. A many-state relaxation model enabled us to describe experimental Mössbauer spectra, leading to an effective anisotropy constant Keff ≈ 45 kJm−3 in case of weakly interacting particles, consistent with results from ferromagnetic resonance. Our unique multi-technique approach, spanning a huge regime of characteristic time windows from about 10 s to 5 ns, provides a concise picture of the correlation of superparamagnetic relaxation with interparticle magnetic dipole interaction.

Simple analytic solution of the rate equations for the early-stage aggregation kinetics of colloidal particles

The potential energy of the interaction between two approaching colloidal particles obtained by the DLVO theory can exhibit a maximum, a primary minimum, and a secondary minimum on the potential curve of the interparticle interaction energy. Behrens and Borkovec (J Colloid Interface Sci 225: 460, 2000) considered a set of coupled nonlinear differential rate equations for the early-stage aggregation kinetics of colloidal particles by taking into account the influence of the secondary minimum and derived an approximate solution to the rate equations as well as their exact numerical solutions. In the present article, an improved simple analytic solution is derived for these rate equations. The obtained solution, which involves two distinct (fast and slow) exponentially decay constants, is found to be in excellent agreement with numerical solutions to the rate equations with negligible errors.

Entropy-driven crystal formation on highly strained substrates

In heteroepitaxy, lattice mismatch between the deposited material and the underlying surface strongly affects nucleation and growth processes. The effect of mismatch is well studied in atoms with growth kinetics typically dominated by bond formation with interaction lengths on the order of one lattice spacing. In contrast, less is understood about how mismatch affects crystallization of larger particles, such as globular proteins and nanoparticles, where interparticle interaction energies are often comparable to thermal fluctuations and are short ranged, extending only a fraction of the particle size. Here, using colloidal experiments and simulations, we find particles with short-range attractive interactions form crystals on isotropically strained lattices with spacings significantly larger than the interaction length scale. By measuring the free-energy cost of dimer formation on monolayers of increasing uniaxial strain, we show the underlying mismatched substrate mediates an entropy-driven attractive interaction extending well beyond the interaction length scale. Remarkably, because this interaction arises from thermal fluctuations, lowering temperature causes such substrate-mediated attractive crystals to dissolve. Such counterintuitive results underscore the crucial role of entropy in heteroepitaxy in this technologically important regime. Ultimately, this entropic component of lattice mismatched crystal growth could be used to develop unique methods for heterogeneous nucleation and growth of single crystals for applications ranging from protein crystallization to controlling the assembly of nanoparticles into ordered, functional superstructures. In particular, the construction of substrates with spatially modulated strain profiles would exploit this effect to direct self-assembly, whereby nucleation sites and resulting crystal morphology can be controlled directly through modifications of the substrate.

Small-Angle Neutron Scattering Investigation of Gold Nanoparticle Clustering and Ligand Structure Under Antisolvent Conditions

Solution-based nanoparticle synthesis offers many benefits, primarily control over nanoparticle size, shape, and surface chemistry, as appropriate for different applications. Often, excess stabilizing ligand or surfactant is required during synthesis and remains in solution. This can be deleterious to end applications, and thus postsynthesis purification must be employed. Ethanol is a common liquid antisolvent used to purify and size-selectively fractionate hydrophobically modified metallic nanoparticles dispersed in organic solvents, particularly toluene or hexane. We have employed small-angle neutron scattering (SANS) to investigate the nanoparticle ligand response to antisolvent conditions for gold nanoparticles (GNPs) in toluene-d8 and n-hexane-d14 at varying ethanol-d6 antisolvent compositions. These conditions are common in postsynthesis nanoparticle purification, fractionation, and surface deposition. The ligand lengths and ligand solvation for octadecanethiol and dodecanethiol modified GNPs were found to decrease from 16 to 8 Å and 13 to 7 Å, respectively, with increasing ethanol-d6 concentrations, directly impacting their dispersibility in solution. Calculated Flory–Huggins interaction parameters were found to support the trends determined by SANS. This research has led to a greater understanding of ligand structure and solvation during the nanoparticle precipitation process, providing critical results to model the ligand repulsion contributions to the interparticle interaction energy, which governs the nanoparticle behavior in solution. In addition, nanoparticle clustering was observed at dilute concentrations, and a fractal cluster model was used to interpret the SANS data.

Coalescence of particle-laden drops with a planar oil–water interface

The coalescence mechanism of a particle-laden drop resting at an oil–water interface has been studied. Two mechanisms for drop coalescence are observed; (i) complete coalescence, in which the drop experiences total coalescence in one event, and (ii) partial coalescence, where a drop is observed to separate during coalescence, producing a smaller secondary drop that rebounds and comes to rest at the planar oil–water interface. For particle-laden drops of approximately 4mm in diameter, we show the critical condition for partial to complete coalescence to be dependent on the particle concentration, and the interparticle interaction energy. Colloidal silica spheres dispersed in 10−4M KNO3 electrolyte solution are highly charged and remain dispersed in the drop. By increasing the solids concentration, we measure the transition from partial to complete coalescence at 20wt.%. However, this critical condition can be reduced by increasing the interparticle interaction energy. In 1M KNO3 electrolyte solution, the particle surface charge is sufficiently screened such that particle clusters readily form in the water drop. With particle clustering, transition from partial to complete coalescence is measured at 8wt.% solids.

Magnetophoresis, sedimentation, and diffusion of particles in concentrated magnetic fluids

A dynamic mass transfer equation for describing magnetophoresis, sedimentation, and gradient diffusion of colloidal particles in concentrated magnetic fluids has been derived. This equation takes into account steric, magnetodipole, and hydrodynamic interparticle interactions. Steric interactions have been investigated using the Carnahan-Starling approximation for a hard-sphere system. In order to study the effective interparticle attraction, the free energy of the dipolar hard-sphere system is represented as a virial expansion with accuracy to the terms quadratic in particle concentration. The virial expansion gives an interpolation formula that fits well the results of computer simulation in a wide range of particle concentrations and interparticle interaction energies. The diffusion coefficient of colloidal particles is written with regard to steric, magnetodipole and hydrodynamic interactions. We thereby laid the foundation for the formulation of boundary-value problems and for calculation of concentration and magnetic fields in the devices (for example, magnetic fluid seals and acceleration sensors), which use a concentrated magnetic fluid as a working fluid. The Monte-Carlo methods and the analytical approach are employed to study the magnetic fluid stratification generated by the gravitational field in a cylinder of finite height. The coefficient of concentration stratification of the magnetic fluid is calculated in relation to the average concentration of particles and the dipolar coupling constant. It is shown that the effective particle attraction causes a many-fold increase in the concentration inhomogeneity of the fluid if the average volume fraction of particles does not exceed 30%. At high volume concentrations steric interactions play a crucial role.