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The application of liquid–liquid chromatography principles to solvent extraction processes in hydrometallurgy can greatly simplify rare earth metal separation technologies by separating multicomponent mixtures in one technological operation. In this study, the chromatographic separation of rare earth elements (REEs) in multistage extraction columns was experimentally studied under conditions of impulse sample injection—single and multiple loading of large volumes of metal salt solution into the installation. The results obtained showed the feasibility of operating sieve plate extraction columns in the liquid–liquid chromatography mode. A closed-loop recycling technology is proposed for the separation of rare earth elements in multistage extraction columns operating in the liquid–liquid chromatography mode. For further development and industrial implementation of this technology, experimental studies should be conducted on intensified multistage extraction columns, such as sectioned columns with agitators and vibrating plate columns. Computer simulation of the chromatographic separation of rare earth elements by closed-loop recycling liquid–liquid chromatography was carried out. [ABSTRACT FROM AUTHOR]

In the recycling of retired lithium‐ion batteries (LIBs), the cathode materials containing valuable metals should be first separated from the current collector aluminum foil to decrease the difficulty and complexity in the subsequent metal extraction. However, strong the binding force of organic binder polyvinylidene fluoride (PVDF) prevents effective separation of cathode materials and Al foil, thus affecting metal recycling. This paper reviews the composition, property, function, and binding mechanism of PVDF, and elaborates on the separation technologies of cathode material and Al foil (e.g., physical separation, solid‐phase thermochemistry, solution chemistry, and solvent chemistry) as well as the corresponding reaction behavior and transformation mechanisms of PVDF. Due to the characteristic variation of the reaction systems, the dissolution, swelling, melting, and degradation processes and mechanisms of PVDF exhibit considerable differences, posing new challenges to efficient recycling of spent LIBs worldwide. It is critical to separate cathode materials and Al foil and recycle PVDF to reduce environmental risks from the recovery of retired LIBs resources. Developing fluorine‐free alternative materials and solid‐state electrolytes is a potential way to mitigate PVDF pollution in the recycling of spent LIBs in the EV era. [ABSTRACT FROM AUTHOR]

In this work, a phase-field model is established to capture the void migration behavior under a temperature gradient within a crystal matrix, with an appropriate consideration of the surface diffusion mechanism and the vapor transport mechanism. The interfacial energy and the coupling between the vacancy concentration field and the crystal order parameter field are carefully modeled. Simulations are performed on UO2. The result shows that for small voids (with an area≤πμm2), the well-known characteristics of void migration, in consistence with the analytical model, can be recovered. The migration is manifested by a constant velocity and a minor change of the void shape. In contrast, for large voids (with an area of ~10 μm2) initially in circular shapes, significant deformation of the void from a circular to cashew-like shape is observed. After long-time migration, the deformed void would split into smaller voids. The size-dependent behavior of void migration is due to the combined effect of the interfacial energy (which tends to keep the void in circular shape) and the surface diffusion flow (which tends to deform the void due to the nonuniform diffusion along the surface). Moreover, the initial shape of the void modifies the migration velocity and the time point when splitting occurs (for large voids) at the beginning of migration due to the shape relaxation of the void. However, it has a minor effect on the long-time migration. Our work reveals novel void migration behaviors in conditions where the surface-diffusion mechanism is dominant over the vapor transport mechanism; meanwhile, the size of the void lies at a mediate size range. [ABSTRACT FROM AUTHOR]

Membrane separation technology is attracting a broad spectrum of attention because of its low energy consumption and superior availability in oily wastewater treatment. Poly(vinylidene fluoride) (PVDF) membranes play an important role in membrane separation field. Herein, a kind of superhydrophilic/underwater superoleophobic nanoparticles modified PVDF membrane based on mussel-inspired chemistry was prepared via a one-pot method. This method applied the Michael addition/Schiff base reactions between dopamine (DA) and alkoxy hydrolysis of (3-Aminopropyl) trimethoxysilane (APTMS). The water contact angle (WCA) decreased from 117∘ to 12.6∘ after the modification. The resultant superhydrophilic/underwater superoleophobic membrane exhibited the outstanding water flux (12280.4 L m − 2 h − 1 bar − 1) , which was a sixfold increment compared to Pristine PVDF. Besides, the resultant membranes showed the effective separation of various oil–water emulsions (> 9 8 %) , and a high recoverability in multiple-iterations presented the membrane possessing the performance of persistent separation. With the simplicity of one-pot method preparation, outstanding performance, and environmental friendliness, this work provided a potential strategy to large-scale modified membrane materials for the treatment of oily wastewater. In this work, hybridized hydrophilic nanoparticles obtained through reactions of DA and APTMS were extraordinary deposited on PVDF surface for the modification of hydrophilicity. The entire deposition process of nanoparticles was carried out in a buffer solution at ambient room temperature. The as-prepared membrane exhibited excellent superhydrophilic/underwater superoleophobic and anti-fouling properties. The resultant membranes were tested for reusability, generalizability, and separation performance in complex environments. The present results indicated that the modified PVDF membranes possessed good potentials and anti-fouling properties for oil-water separation. [ABSTRACT FROM AUTHOR]

The present work focuses on the structure of a double-layer of overscreened charged surfaces by smeared-out charges and probes the link between the structure of a double-layer and the bulk properties of an electrolyte with special view to the role of the Kirkwood crossover. Just as the Kirkwood line divides a bulk solution into a fluid with monotonic and oscillatory decaying correlations, it similarly separates charge inversion into two broad domains, with and without oscillating charge density profile. As initially oscillations may appear like a far-field occurrence, eventually they develop into a full fledged layering of a charge density. [ABSTRACT FROM AUTHOR]

In this work, we theoretically study the interaction between a solid state membrane equipped with a nanopore and a tethered, negatively charged polymer chain subjected to a time-dependent applied electrolyte bias. In order to describe the movement of the chain in the biomolecule-membrane system immersed in an electrolyte solution, Brownian dynamics is used. We show that we can control the polymer's equilibrium position with various applied electrolyte biases: for a sufficiently positive bias, the chain extends inside the pore, and the removal of the bias causes the polymer to leave the pore. Corresponding to a driven process, we find that the time it takes for a biomolecular chain to enter and extend into a nanopore in a positive bias almost increases linearly with chain length while the amount of time it takes for a polymer chain to escape the nanopore is mainly governed by diffusion. [ABSTRACT FROM AUTHOR]

This paper deals with diffusion of point particles in linearly corrugated two-dimensional channels. Such geometry allows one to obtain an approximate analytical expression that gives the particle effective diffusivity as a function of the geometric parameters of the channel. To establish its accuracy and the range of applicability, the expression is tested against Brownian dynamics simulation results. The test shows that the expression works very well for long channel periods, but fails when the period is not long enough compared to the minimum width of the channel. Tofix this deficiency, we propose a simple empirical correction to the analytical expression. The resulting corrected expression for the effective diffusivity is in excellent agreement with the simulation results for all values of the channel period. [ABSTRACT FROM AUTHOR]

[Display omitted] • The bifunctional MoS 2 @Cl/S-CNM was prepared via electrospinning technology. • MoS 2 @Cl/S-CNM shows excellent self-cleaning performance. • Photocatalytic degradation ability is the key to MoS 2 @Cl/S-CNM. • MoS 2 @Cl/S-CNM exhibits superior separation performance in practical oily wastewater. The development of membrane separation technology has long been constrained by membrane fouling issues. This work developed novel chlorine sulfur double-doped graphite carbon nitride composite molybdenum disulfide photocatalyst (MoS 2 @Cl/S-TCN) and incorporated it into polyacrylonitrile nanofiber membranes through electrospinning technology to obtain porous catalytic nanofiber membrane (MoS 2 @Cl/S-CNM). MoS 2 @Cl/S-CNM has superior oil–water separation and photocatalytic degradation performance. The typical porous and nodular structures of nanofiber endow the membrane with superior hydrophilicity and lipophobicity under water. The MoS 2 @Cl/S-CNM exhibits superior oil–water separation efficiency above 98.0% for various oil-in-water emulsions including crude oil emulsion. Significantly, the composite membrane shows a superior self-cleaning performance with the flux recovery rate (FRR) of up to 96.1% for actual oilfield wastewater under visible light irradiation washing conditions. In addition, the novel MoS 2 @Cl/S-TCN catalyst, with a fast transfer of charge carriers at the interface, effective separation of photogenerated electron hole pairs and great thermodynamic driving force, renders the membrane with a positive photocatalytic degradation ability of 79.5% to p-nitrophenol (PNP). MoS 2 @Cl/S-CNM also exhibits excellent durability and chemical stability during various solvents and salt solutions. In conclusion, the novel multifunctional catalytic membrane is of great significance for the advanced treatment of petroleum industry wastewater in terms of severe membrane fouling and complicated wastewater quality conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Super-hydrophilic polyetherimide membrane was prepared with RF microspheres wrapped. • The mechanism of the pearl necklace-like structures preparation was studied. • The oil–water separation efficiency of PEI@RF-3 was kept above 99%. • PEI@RF-3 showed excellent environmental stability in harsh conditions. In terms of treating the problem of oily wastewater, membrane separation technology has always been a simple and efficient method of oil–water emulsion separation. Inspired by the hydrophilic bumps of the desert beetle, the polyetherimide (PEI) fiber membrane with super-hydrophilic/underwater super-oleophobic properties was prepared by electrospinning and subsequent seeded aggregation strategy of resorcinol (R) and formaldehyde (F). The membrane (PEI@RF) demonstrates pearl necklace-like structures and good antifouling properties, oil–water separation performances, as well as good stabilities in a variety of environments (immersed in water at high/low temperature, and in acid/alkali/salt solutions). More importantly, the as-prepared membrane exhibits excellent performance for various kinds of oil–water mixtures separation, and the corresponding separation fluxes and efficiencies are above 2600 L/m2·h and 99 %, respectively. [ABSTRACT FROM AUTHOR]

The finite-temperature phase diagram of hydrogen in the region of phase IV and its neighborhood was studied using the ab initio molecular dynamics (MD) and the ab initio path-integral molecular dynamics (PIMD). The electronic structures were analyzed using the density-functional theory (DFT), the random-phase approximation, and the diffusion Monte Carlo (DMC) methods. Taking the state-of-the-art DMC results as benchmark, comparisons of the energy differences between structures generated from the MD and PIMD simulations, with molecular and dissociated hydrogens, respectively, in the weak molecular layers of phase IV, indicate that standard functionals in DFT tend to underestimate the dissociation barrier of the weak molecular layers in this mixed phase. Because of this underestimation, inclusion of the quantum nuclear effects (QNEs) in PIMD using electronic structures generated with these functionals leads to artificially dissociated hydrogen layers in phase IV and an error compensation between the neglect of QNEs and the deficiencies of these functionals in standard ab initio MD simulations exists. This analysis partly rationalizes why earlier ab initio MD simulations complement so well the experimental observations. The temperature and pressure dependencies for the stability of phase IV were also studied in the end and compared with earlier results. [ABSTRACT FROM AUTHOR]

The fluorescence of the exciplex, 1[D+δA-δ ], formed at contact of photoexcited acceptor 1A* with an electron donor 1D, is known to be very sensitive to an external magnetic field, reducing the spin conversion efficiency in the resulting geminate radical ion pair, 1, 3[D+...A-]. The relative increase of the exciplex fluorescence in the highest magnetic field compared to the lowest one, known as the magnetic field effect, crucially depends on the viscosity of the solvent. This phenomenon first studied experimentally is at first reproduced here theoretically. The magnetic field effect is shown to vanish in both limits of high and low solvent diffusivity reaching a maximum in between. It is also very sensitive to the solvent dielectric constant and to the exciplex and radical-ion pair conversion rates. [ABSTRACT FROM AUTHOR]

Spiral waves composed of coherent traveling waves surrounding a core containing stochastically distributed stationary areas are found in numerical simulations of a three-variable reaction-diffusion system with one diffusible species. In the spiral core, diffusion of this component (w) mediates transitions between dynamic states of the subsystem formed by the other two components, whose dynamics is more rapid than that of w. Diffusive coupling between adjacent sites can be "on" or "off" depending on the subsystem state. The incoherent structures in the spiral core are produced by this decoupling of the slow diffusive component from the fast non-diffusing subsystem. The phase diagram reveals that the region of incoherent behavior in chimera spirals grows drastically, leading to modulation and breakup of the spirals, in the transition zones between 1n-1 and 1n local mixed-mode oscillations. [ABSTRACT FROM AUTHOR]

It is widely believed that the breakdown of the Stokes-Einstein (SE) relation between the translational diffusivity and the shear viscosity in supercooled liquids is due to the development of dynamic heterogeneity, i.e., the presence of both slow and fast moving particles in the system. In this study we directly calculate the distribution of the diffusivity for a model system for different temperatures in the supercooled regime. We find that with decreasing temperature, the distribution evolves from Gaussian to bimodal indicating that on the time scale of the typical relaxation time, mobile (fluid like) and less mobile (solid like) particles in the system can be unambiguously identified. We also show that less mobile particles obey the Stokes-Einstein relation even in the supercooled regime and it is the mobile particles which show strong violation of the Stokes-Einstein relation in agreement with the previous studies on different model glass forming systems. Motivated by some of the recent studies where an ideal glass transition is proposed by randomly pinning some fraction of particles, we then studied the SE breakdown as a function of random pinning concentration in our model system. We showed that degree of SE breakdown increases quite dramatically with increasing pinning concentration, thereby providing a new way to unravel the puzzles of SE violation in supercooled liquids in greater details. [ABSTRACT FROM AUTHOR]

In this paper we investigate the adsorption of various probe molecules in order to characterize the porous structure of a series of pillared interlayered clays (PILC). To that aim, volumetric and microcalorimetric adsorption experiments were performed on various Zr PILC samples using nitrogen, toluene, and mesitylene as probe molecules. For one of the samples, neutron scattering experiments were also performed using toluene as adsorbate. Various structural models are proposed and tested by means of a comprehensive computer simulation study, using both geometric and percolation analysis in combination with Grand Canonical Monte Carlo simulations in order to model the volumetric and microcalorimetric isotherms. On the basis of this analysis, we propose a series of structural models that aim at accounting for the adsorption experimental behavior, and make possible a microscopic interpretation of the role played by the different interactions and steric effects in the adsorption processes in these rather complex disordered microporous systems. [ABSTRACT FROM AUTHOR]

We present a fast and accurate numerical method for the self-consistent field theory calculations of confined polymer systems. It introduces an exponential time differencing method (ETDRK4) based on Chebyshev collocation, which exhibits fourth-order accuracy in temporal domain and spectral accuracy in spatial domain, to solve the modified diffusion equations. Similar to the approach proposed by Hur et al. [Macromolecules 45, 2905 (2012)], non-periodic boundary conditions are adopted to model the confining walls with or without preferential interactions with polymer species, avoiding the use of surface field terms and the mask technique in a conventional approach. The performance of ETDRK4 is examined in comparison with the operator splitting methods with either Fourier collocation or Chebyshev collocation. Numerical experiments show that our exponential time differencing method is more efficient than the operator splitting methods in high accuracy calculations. This method has been applied to diblock copolymers confined by two parallel flat surfaces. [ABSTRACT FROM AUTHOR]

The subject of this paper is studies of the deterministic identifiability of molecular parameters, such as rotational diffusion tensor components and orientation of electronic transition moments, resulting from the time-resolved fluorescence anisotropy experiment. In the most general case considered, a pair of perpendicularly polarized emissions enables the unique determination of all the rotational diffusion tensor's principal components. The influence of the tensor's symmetry and the associated degeneration of its eigenvalues on the identifiability of the electronic transitions moments is systematically investigated. The analysis reveals that independently of the rotational diffusion tensor's symmetry, the transition moments involved in photoselection and emission processes cannot be uniquely identified without a priori information about their mutual orientation or their orientation with respect to the principal axes of the tensor. Moreover, it is shown that increasing the symmetry of the rotational diffusion tensor deteriorates the degree of the transition moments identifiability. To obtain these results analytically, a novel approach to solve bilinear system of equations for Markov parameters is applied. The effect of the additional information, obtained from fluorescence measurements for different molecular mobilities, to improve the identifiability at various levels of analysis is shown. The effectiveness and reliability of the target analysis method for experimental determination of the molecular parameters is also discussed. [ABSTRACT FROM AUTHOR]

Homogeneous water condensation and ice formation in supersonic expansions to vacuum for stagnation pressures from 12 to 1000 mbar are studied using the particle-based Ellipsoidal-Statistical Bhatnagar-Gross-Krook (ES-BGK) method. We find that when condensation starts to occur, at a stagnation pressure of 96 mbar, the increase in the degree of condensation causes an increase in the rotational temperature due to the latent heat of vaporization. The simulated rotational temperature profiles along the plume expansion agree well with measurements confirming the kinetic homogeneous condensation models and the method of simulation. Comparisons of the simulated gas and cluster number densities, cluster size for different stagnation pressures along the plume centerline were made and it is found that the cluster size increase linearly with respect to stagnation pressure, consistent with classical nucleation theory. The sensitivity of our results to cluster nucleation model and latent heat values based on bulk water, specific cluster size, or bulk ice are examined. In particular, the ES-BGK simulations are found to be too coarse-grained to provide information on the phase or structure of the clusters formed. For this reason, molecular dynamics simulations of water condensation in a one-dimensional free expansion to simulate the conditions in the core of a plume are performed. We find that the internal structure of the clusters formed depends on the stagnation temperature. A larger cluster of average size 21 was tracked down the expansion, and a calculation of its average internal temperature as well as a comparison of its radial distribution functions (RDFs) with values measured for solid amorphous ice clusters lead us to conclude that this cluster is in a solid-like rather than liquid form. In another molecular-dynamics simulation at a much lower stagnation temperature, a larger cluster of size 324 and internal temperature 200 K was extracted from an expansion plume and equilibrated to determine its RDF and self-diffusion coefficient. The value of the latter shows that this cluster is formed in a supercooled liquid state rather than in an amorphous solid state. [ABSTRACT FROM AUTHOR]

The anisotropic 3D equation describing the pointlike particles diffusion in slender impermeable tubes of revolution with cross section smoothly depending on the longitudinal coordinate is the object of our study. We use singular perturbations approach to find the rigorous asymptotic expression for the local particles concentration as an expansion in the ratio of the characteristic transversal and longitudinal diffusion relaxation times. The corresponding leading-term approximation is a generalization of well-known Fick-Jacobs approximation. This result allowed us to delineate the conditions on temporal and spatial scales under which the Fick-Jacobs approximation is valid. A striking analogy between solution of our problem and the method of inner-outer expansions for low Knudsen numbers gas kinetic theory is established. With the aid of this analogy we clarify the physical and mathematical meaning of the obtained results. [ABSTRACT FROM AUTHOR]

The chemical master equation (CME) and the mathematically equivalent stochastic simulation algorithm (SSA) assume that the reactant molecules in a chemically reacting system are "dilute" and "well-mixed" throughout the containing volume. Here we clarify what those two conditions mean, and we show why their satisfaction is necessary in order for bimolecular reactions to physically occur in the manner assumed by the CME and the SSA. We prove that these conditions are closely connected, in that a system will stay well-mixed if and only if it is dilute. We explore the implications of these validity conditions for the reaction-diffusion (or spatially inhomogeneous) extensions of the CME and the SSA to systems whose containing volumes are not necessarily well-mixed, but can be partitioned into cubical subvolumes (voxels) that are. We show that the validity conditions, together with an additional condition that is needed to ensure the physical validity of the diffusion-induced jump probability rates of molecules between voxels, require the voxel edge length to have a strictly positive lower bound. We prove that if the voxel edge length is steadily decreased in a way that respects that lower bound, the average rate at which bimolecular reactions occur in the reaction-diffusion CME and SSA will remain constant, while the average rate of diffusive transfer reactions will increase as the inverse square of the voxel edge length. We conclude that even though the reaction-diffusion CME and SSA are inherently approximate, and cannot be made exact by shrinking the voxel size to zero, they should nevertheless be useful in many practical situations. [ABSTRACT FROM AUTHOR]

This paper deals with a problem of transient anomalous diffusion which is currently found to emerge from a wide range of complex processes. The nonscaling behavior of such phenomena reflects changes in time-scaling exponents of the mean-squared displacement through time domain - a more general picture of the anomalous diffusion observed in nature. Our study is based on the identification of some transient subordinators responsible for transient anomalous diffusion. We derive the corresponding fractional diffusion equation and provide links to the corresponding compound relaxation laws supported by this case generalizing many empirical dependencies well-known in relaxation investigations. [ABSTRACT FROM AUTHOR]

Today, it is extremely urgent to face the increasing shortage of clean and safe water resources, determined by the exponential growth of both world population and its consumerism, climate change and pollution. Water remediation from traditional chemicals and contaminants of emerging concerns (CECs) is supposed to be among the major methods to solve water scarcity issues. Reverse osmosis (RO) and nanofiltration (NF) membrane separation technologies have proven to be feasible, sustainable and highly effective methods for the removal of contaminants, comprising the extremely persistent and recalcitrant perfluoroalkyl substances (PFASs), which failed to be treated through the traditional water treatment approaches. So far, however, they have been unable to assure PFASs levels under the established guidance limits for drinking water and still suffer from fouling problems, which limit their large-scale application. Novel configurations, improvement in process design and the development of high-performant materials for membrane production are important steps to tackle these issues, especially in view of new more stringent regulations limiting PFASs content in drinking water. As a possible future strategy, nanocomposite mixed matrix membranes (MMMs) offer a platform of advanced materials which promise to revolutionize RO/NF technologies for water treatment. In particular, the introduction of MOFs as adsorbent fillers in the polymeric membrane matrix appears as a viable approach for the effective and selective capture and removal of PFASs from water. The objective of this review is to provide a dedicated outlook on the most recent advances in RO and NF membrane technologies for PFASs removal. The effects of membrane properties, the solution chemistry, and contaminant properties on the RO/NF performances will be discussed in detail. Future challenges are also discussed, offering new perspectives toward the development of new advanced membranes with improved performance for PFAS removal, which are likely to significantly progress RO and NF technology for water remediation. [ABSTRACT FROM AUTHOR]

Rotational diffusion processes are correlated with nanoparticle visualization and manipulation techniques, widely used in nanocomposites, nanofluids, bioscience, and so on. However, a systematical methodology of deriving this diffusivity is still lacking. In the current work, three molecular dynamics (MD) schemes, including equilibrium (Green-Kubo formula and Einstein relation) and nonequilibrium (Einstein-Smoluchowski relation) methods, are developed to calculate the rotational diffusion coefficient, taking a single rigid carbon nanotube in fluid argon as a case. We can conclude that the three methods produce same results on the basis of plenty of data with variation of the calculation parameters (tube length, diameter, fluid temperature, density, and viscosity), indicative of the validity and accuracy of the MD simulations. However, these results have a non-negligible deviation from the theoretical predictions of Tirado et al. [J. Chem. Phys. 81, 2047 (1984)], which may come from several unrevealed factors of the theory. The three MD methods proposed in this paper can also be applied to other situations of calculating rotational diffusion coefficient. [ABSTRACT FROM AUTHOR]

Molecular dynamics (MD) simulations of mixtures of the room temperature ionic liquids (ILs) 1-butyl-4-methyl imidazolium [BMIM]/dicyanoamide [DCA] and [BMIM][NO3-] with HNO3 have been performed utilizing the polarizable, quantum chemistry based APPLE&P® potential. Experimentally it has been observed that [BMIM][DCA] exhibits hypergolic behavior when mixed with HNO3 while [BMIM][NO3-] does not. The structural, thermodynamic, and transport properties of the IL/HNO3 mixtures have been determined from equilibrium MD simulations over the entire composition range (pure IL to pure HNO3) based on bulk simulations. Additional (non-equilibrium) simulations of the composition profile for IL/HNO3 interfaces as a function of time have been utilized to estimate the composition dependent mutual diffusion coefficients for the mixtures. The latter have been employed in continuum-level simulations in order to examine the nature (composition and width) of the IL/HNO3 interfaces on the millisecond time scale. [ABSTRACT FROM AUTHOR]

We study the structure formation of grafted Y-shaped block copolymers in solutions via dissipative particle dynamics simulations. We systematically examine how the solvent quality, the grafting density, and the incompatibility between polymer blocks affect the morphology of the grafted layer. The layer thickness and the lateral domain size and inhomogeneity of the layer structures are analyzed. A power law, hlayer ∼ σn, is found between the layer thickness (hlayer) and the grafting density (σ), which shows three regimes, i.e., the brushes regime, the crossover regime, and the mushrooms regime. In the brushes regime, we also find that the exponent n is dependent on the grafting densities and solvent conditions, regardless of the incompatibility between the polymer blocks. In the mushrooms and the crossover regime, a variety of surface structures can be observed, such as mixed micelles, internally segregated micelles, hamburger micelles, segmented wormlike micelles, and dumbbell micelles. The stripe-like structure formed in the brushes regime is investigated in detail. The simulation results are in good agreement with theoretical predictions and experimental observations, and can be helpful for the surface structure design of functional materials. [ABSTRACT FROM AUTHOR]

In recent years, inspired by the structure of natural lotus leaves and fish scales, the oil/water separation membrane with special wettability has made remarkable progress. A cost-effective, eco-friendly and facile approach of membranes with special wettability performance is highly desired. Herein, magnesium hydroxide (Mg(OH)2) is synthesized in situ on cotton fabrics through a surface micro-dissolution method to prepare superhydrophilic and underwater superoleophobic functionalized fabrics. Driven by gravity, the Mg(OH)2@fabric can successfully separate the oil/water mixture with high flux of 3027–4137 L/m2 h and high separation efficiency of 99.5%. In addition, after soaking in harsh environment for 72 h, such as alkali and salt solution, it still has high stability and can be used as a membrane to separate a series of oil/water mixtures. Driven by a constant current pump (200 mL/min), the developed fabric can separate oil-in-water emulsions with a high separation efficiency of 99.5%. After 50 cycles, the separation efficiency of the treated fabric for oil–water mixture is more than 99.3%, and the underwater contact angle is more than 156.6°. This method can simply and effectively produce fabrics that can be used to treat water purification and oily wastewater, and has a broad application prospect. [ABSTRACT FROM AUTHOR]

Large amount of oil leakage and organic wastewater discharge have greatly harmed the natural environment and human health. Therefore, researchers urgently need an effective method to address this problem. Superwetting materials can provide people with a good way to solve the problem because of their special selective wettability. In this report, a kind of green, fluorine-free, durable and low-cost superhydrophobic magnetic sponge was prepared by Fe3O4 particles and stearic acid. It can be controlled by changing the magnetic field to avoid direct contact with toxic and harmful solvents by the operator. The prepared material can be soaked for 7 days under harsh conditions of an acid solution, an alkali solution and a salt solution, and still maintain superhydrophobic property. Moreover, it is loaded with a weight of 200 g for 80 cycles of extrusion deformation (the compressive strain is 75%), and then with superhydrophobic properties. The sponge can be used for the separation of oil–water mixtures and oil–water emulsion purification with a separation efficiency of over 90%. It is worth mentioning that crude oil emulsion can be separated and purified by this material. The magnetic superhydrophobic sponge is prepared by simple and easy-to-operate method, which can be prepared in large scale. These results provide useful avenue utilization for the sponge, demonstrating the potential applications for oil–water separation, sewage purification, emulsion purification and oil spill collection. [ABSTRACT FROM AUTHOR]

Using the Jagla model potential we calculate the potential of mean force (PMF) between hard sphere solutes immersed in a liquid displaying water-like properties. Consistent estimates of the PMF are obtained by (a) umbrella sampling, (b) calculating the work done by the mean force acting on the hard spheres as a function of their separation, and (c) determining the position dependent chemical potential after calculating the void space in the liquid. We calculate the PMF for an isobar along which cold denaturation of a model protein has previously been reported. We find that the PMF at contact varies non-monotonically, which is consistent with the observed cold denaturation. The Henry constant also varies non-monotonically with temperature. We find, on the other hand, that a second (solvent separated) minimum of the PMF becomes deeper as temperature decreases. We calculate the solvent-solvent pair correlation functions for solvents near the solute and in the bulk, and show that, as temperature decreases, the two pair correlation functions become indistinguishable, suggesting that the perturbation of solvent structure by the solute diminishes as temperature decreases. The solvent-solute pair correlation function at contact grows as the temperature decreases. We calculate the cavity correlation function and show the development of a solvent-separated peak upon decrease of temperature. These observations together suggest that cold denaturation occurs when the solvent penetrates between hydrophobic solutes in configurations with favorable free energy. Our results thus suggest that cold denatured proteins are structured and that cold denaturation arises from strong solvent-solute interactions, rather than from entropic considerations as in heat denaturation. [ABSTRACT FROM AUTHOR]

The combination of a top-down and a bottom-up fabrication approach will be a key technology to overcome the minimum size limit of the top-down approach. Gentle cold welding is a promising method to connect nano objects without appreciable damages to the nano device in a bottom-up approach. We developed the gentle cold welding method using the combination of an electrical field and an atomic rearrangement. The formulated process was visualized between gold tips using a transmission electron microscope. The initial connection mechanism was divided into three modes depending on a bias voltage between tips; (1) physical contact, (2) atom extraction, and (3) field evaporation, depending on the electrical fields. All the nano connections grew by the atomic rearrangement driven by gold surface self-diffusion. The grown connections were single crystalline structures. These results suggested that this welding will be a useful method to build up future nano devices and systems. [ABSTRACT FROM AUTHOR]

Specially designed plate-impact experiments have been conducted on a Zr-based amorphous alloy using a single-stage light gas gun. To understand the microdamage nucleation process in the material, the samples are subjected to dynamic tensile loadings of identical amplitude (∼ 3.18 GPa) but with different durations (83-201 ns). A cellular pattern with an equiaxed shape is observed on the spallation surface, which shows that spallation in the tested amorphous alloy is a typical ductile fracture and that microvoids have been nucleated during the process. Based on the observed fracture morphologies of the spallation surface and free-volume theory, we propose a microvoid nucleation model of bulk amorphous alloys. It is found that nucleation of microvoids at the early stage of spallation in amorphous alloys results from diffusion and coalescence of free volume, and that high mean tensile stress plays a dominant role in microvoid nucleation. [ABSTRACT FROM AUTHOR]

A study of carrier transport in top-gate and bottom-contact TIPS-pentacene organic field-effect transistors (OFETs) based on mobility is presented. Among three mobilities extracted by different methods, the low-field mobility obtained by the Y function exhibits the best reliability and ease for use, whereas the widely applied field-effect mobility is not reliable, particularly in short-channel transistors and at low temperatures. A detailed study of contact transport reveals its strong impact on short-channel transistors, suggesting that a more intrinsic transport analysis is better implemented in relatively longer-channel devices. The observed temperature dependences of mobility are well explained by a transport model with Gaussian-like diffusivity band tails, different from diffusion in localized states band tails. This model explicitly interprets the non-zero constant mobility at low temperatures and clearly demonstrates the effects of disorder and hopping transport on temperature and carrier density dependences of mobility in organic transistors. [ABSTRACT FROM AUTHOR]

When two types of side chains (A,B) are densely grafted to a (stiff) backbone and the resulting bottlebrush polymer is in a solution under poor solvent conditions, an incompatibility between A and B leads to microphase separation in the resulting cylindrical brush. The possible types of ordering are reminiscent of the ordering of block copolymers in cylindrical confinement. Starting from this analogy, Leibler's theory of microphase separation in block copolymer melts is generalized to derive a description of the system in the weak segregation limit. Also molecular dynamics simulation results of a corresponding coarse-grained bead-spring model are presented. Using side chain lengths up to N = 50 effective monomers, the ratio of the Lennard-Jones energy parameter between unlike monomers ([variant_greek_epsilon]AB) and monomers of the same kind ([variant_greek_epsilon]AA = [variant_greek_epsilon]BB) is varied. Various correlation functions are analyzed to study the conditions when (local) Janus-cylinder-type ordering and when (local) microphase separation in the direction along the cylinder axis occurs. Both the analytical theory and the simulations give evidence for short-range order due to a tendency toward microphase separation in the axial direction, with a wavelength proportional to the side chain gyration radius, irrespective of temperature and grafting density, for a wide range of these parameters. [ABSTRACT FROM AUTHOR]

The structural and dynamical properties of macromolecules in confining or crowded environments are different from those in simple bulk liquids. In this paper, both the conformational and diffusional dynamics of globular polymers are studied in solutions containing fixed spherical obstacles. These properties are studied as a function of obstacle volume fraction and size, as well as polymer chain length. The results are obtained using a hybrid scheme that combines multiparticle collision dynamics of the solvent with molecular dynamics that includes the interactions among the polymer monomers and between the polymer beads and obstacles and solvent molecules. The dynamics accounts for hydrodynamic interactions among the polymer beads and intermolecular forces with the solvent molecules. We consider polymers in poor solvents where the polymer chain adopts a compact globular structure in solution. Our results show that the collapse of the polymer chain to a compact globular state is strongly influenced by the obstacle array. A nonmonotonic variation in the radius of gyration with time is observed and the collapse time scale is much longer than that in simple solutions without obstacles. Hydrodynamic interactions are important at low obstacle volume fractions but are screened at high volume fractions. The diffusion of the globular polymer chain among the obstacles is subdiffusive in character on intermediate time scales where the dynamics explores the local structure of the heterogeneous environment. For large polymer chains in systems with high obstacle volume fractions, the chain adopts bloblike conformations that arise from trapping of portions of the chain in voids among the obstacles. [ABSTRACT FROM AUTHOR]

The dynamics of phase separation of thin film binary fluids is investigated via dissipative particle dynamics simulation. We consider both cases of symmetric and asymmetric interactions between the walls and the two components. In the case of walls interacting symmetrically with the two fluid components, corresponding to a nonwetting case, relatively fast kinetics is observed when the average domain size is smaller than the slit thickness. A crossover to a slow Lifshitz–Slyozov growth is observed at late times. Faster dynamics is observed when the walls act as a slip boundary condition to the velocity field. In the case of asymmetric interactions, such that the system is in the wetting regime, the interplay between wetting kinetics and spinodal decomposition leads to rich dynamics. The phase separation proceeds through three stages. During the first stage, the dynamics is characterized as surface-directed spinodal decomposition, with growth of both average domain size and thickness of the wetting layers. The domain morphology is three dimensional and bicontinuous during the first stage, with kinetics reminiscent of that in bulk systems is observed. The second stage of the phase separation is characterized by the breakup of the bicontinuous domain morphology into small tubular domains bridging the two wetting layers and depletion of the core of the film from the wetting component. During this stage, domains with diameter smaller than thickness of the film shrink and disappear while those with diameter larger that the film thickness grow. The third stage is characterized by growth induced by the backflow of A-component from the wetting layers to the core of the film, leading to the decay in the thickness of the film and growth of the domains bridging the wetting layers. At even later times of the third stage, when the wetting layers become very depleted in the wetting component, growth becomes mediated by diffusion followed by collision of the tubular domains. [ABSTRACT FROM AUTHOR]

A unique thermodynamic model of Fermi gases suitable for semiconductor device simulation is presented. Like other models, such as drift diffusion and hydrodynamics, it employs moments of the Boltzmann transport equation derived using the Fermi–Dirac distribution function. However, unlike other approaches, it replaces the concept of an electron thermal conductivity with the heat capacity of an ideal Fermi gas to determine heat flow. The model is used to simulate a field-effect transistor and show that the external current-voltage characteristics are strong functions of the state space available to the heated Fermi distribution. [ABSTRACT FROM AUTHOR]

Delayed hydride cracking (DHC) tests were conducted on a cold-worked Zr–2.5Nb tube with hydrogen at different test temperatures ranging from 100 to 350 °C. Striation spacing corresponding to a critical hydride length increased with temperature, demonstrating that hydride cracking resistance is enhanced with temperature. Nonetheless, the crack growth rate (CGR) had a positive temperature dependence below 300 °C, showing that at temperatures below 300 °C, the CGR is governed by diffusion-controlled hydride growth. At higher temperatures above 300 °C, however, the CGR decreased rapidly, suggesting that the CGR is dictated not by the hydride growth rate but by the hydride cracking rate. This suggestion is evidenced by experiments where the threshold stress intensity factor for DHC or KIH increased sharply above 300 °C. [ABSTRACT FROM AUTHOR]

We study the formation of nanoholes and quantum rings in GaAs and AlGaAs surfaces by local droplet etching with InxGa1-x. The rings are crystallized from droplet material and surround the nanohole openings. In particular, the influence of the In content x on density, diameter, and depth of the nanoholes is investigated. Our data establish an exponential dependence of these quantities on x, which is quantitatively reproduced by a model that considers different surface diffusion energy barriers for Ga and In. By etching with pure In, hole densities as low as 5×106 cm-2 have been achieved. In addition, for low In content incompletely removed initial droplets are visible on the surface. These droplets are not visible on samples with x>0.5 which indicates a higher desorption rate of In compared to Ga. As a consequence, even in the case of etching with InGa the quantum rings consist of nearly pure GaAs. This is confirmed by photoluminescence experiments of quantum rings overgrown with AlGaAs barrier material. [ABSTRACT FROM AUTHOR]

With a view to investigate the influence of nanosize on thermopower behavior of Nd0.67Sr0.33MnO3 manganites, a systematic investigation of their temperature dependent thermoelectric power (TEP) studies has been undertaken. For this purpose, the samples with different particle sizes were prepared by the sol-gel method by sintering at four different temperatures (viz., 800, 900, 1000, and 1100 °C). The average crystallite sizes were calculated using a modified Scherrer’s formula. The ferromagnetic metallic (FMM) part of the TEP data were fitted to an equation containing diffusion, magnon drag, and phonon drag terms. The relative weights of these contributions were estimated and it has been found that the magnon drag contribution predominantly contributes to the TEP in the FMM region. The phonon drag process in the samples of the present investigation is found to be dominant along the direction of cell parameter “a” than the other two directions. Finally, the paramagnetic insulting part of the TEP data has been analyzed by using small polaron hopping mechanism. [ABSTRACT FROM AUTHOR]

Phase behavior of diblock copolymer/homopolymer blends (AB/C) is investigated theoretically. The study focuses on a special case where all three binary pairs, A/B, B/C, and C/A, are miscible. Despite the miscibility of the binary pairs, a closed-loop immiscible region exists in the AB/C blends when the A/C and B/C pair interactions are sufficiently different. Inside the closed-loop, the system undergoes microphase separation, exhibiting different ordered structures. This phenomenon is enhanced when the homopolymer (C) interacts more strongly to one of the blocks (A or B). [ABSTRACT FROM AUTHOR]

A systematic time-of-flight quasielastic neutron scattering (TOF-QENS) study on diffusion of n-alkanes in a melt is presented for the first time. As another example of a medium-chain molecule, coenzyme Q10 is investigated in the same way. The data were evaluated both in the frequency and in the time domain. TOF-QENS data can be satisfactorily described by different models, and it turned out that the determined diffusion coefficients are largely independent of the applied model. The derived diffusion coefficients are compared with values measured by pulsed-field gradient nuclear magnetic resonance (PFG-NMR). With increasing chain length, an increasing difference between the TOF-QENS diffusion coefficient and the PFG-NMR diffusion coefficient is observed. This discrepancy in the diffusion coefficients is most likely due to a change of the diffusion mechanism on a nanometer length scale for molecules of medium-chain length. [ABSTRACT FROM AUTHOR]

The effects of tetrafluoromethane (CF4) plasma treatment of indium-tin-oxide (ITO) anode on indium diffusion into a poly(3,4-ethylene dioxythiophene):poly(styrene sulphonate) (PEDOT:PSS) layer were studied. Auger electron spectroscopy (AES) depth profile showed that 0.2 at. % indium was present in the PEDOT:PSS layer when ITO was not plasma treated. The plasma treatment of ITO increased the indium concentration to ∼6 at. %. The increase in indium can be explained by an oxygen deficiency in the CF4 plasma treated ITO. The presence of indium in the PEDOT:PSS layer showed a correlation with performance degradation of polymer light-emitting diodes. [ABSTRACT FROM AUTHOR]

Cu–Pd thin-film diffusion couples (individual layer thicknesses of 50 nm) have been prepared by dc-magnetron sputtering on silicon substrates coated with a thin amorphous Si3N4 layer. Stress evolution, microstructural development, and phase formation during interdiffusion have been investigated employing Auger-electron spectroscopy (in combination with sputter-depth profiling), x-ray diffraction, wafer curvature measurements and transmission electron microscopy. Upon annealing at relatively low temperatures (175–250 °C) for durations up to 10 h, considerable diffusional intermixing occurs. Interdiffusion is accompanied by sequential formation of new phases. First, Cu3Pd forms; subsequently, CuPd forms and grows at the expense of Cu3Pd, which has been interpreted as a consequence of interface thermodynamics. Annealing leads to a slight sharpening of the pre-existing {111}-fiber textures and a little increase in the average grain size. A combination of ex situ (x-ray diffraction) and in situ (wafer curvature) stress measurements revealed that tensile stresses are generated during annealing. The obtained stress results have been discussed in the light of possible mechanisms of stress generation, and the dominant sources of stress buildup and relaxation have been identified. [ABSTRACT FROM AUTHOR]

We studied selective area growth modeling and characterization of the AlGaInAs material system. We used a three-dimensional vapor phase diffusion model to extract the effective diffusion lengths of Al, Ga, and In species from measured thickness profiles of the three binaries AlAs, GaAs, and InP. Our growth conditions yield to 50, 85, and 10 μm for Al, Ga, and In, respectively. Based on these values, we achieved a precise prediction of AlGaInAs thickness, composition, band gap, and biaxial strain variations in different selective area growth conditions. Particular attention was paid to the influence of neighboring cells in the case of high mask density. This configuration occurs in practical component mask layout. High mask density leads to interferences between masked cells and enhances the effect of the long diffusion length of aluminum and gallium species. Then, the biaxial strain is tensile shifted and the band gap is blue shifted in the vicinity of a mask, compared to reference material features grown away from the mask. High-resolution micro-photoluminescence and optical interferometer microscopy measurements confirmed the validity of simulated band gap and thickness variations for both bulk and multi-quantum well layers. [ABSTRACT FROM AUTHOR]

The F effect in crystalline Si is quantified by monitoring defects and B diffusion in samples implanted with 25 keV F+ and/or 40 keV Si+. We estimate that about +0.4 Si interstitials are generated per implanted F+ ion, in agreement with the value resulting from the net separation of Frenkel pairs. For short annealings, B diffusion is lower when F+ is coimplanted with Si+ than when only Si+ is implanted, while for longer annealings, B diffusion is higher. This is consistent with a lower but longer-lasting Si interstitial supersaturation set by the additional defects generated by the F+ implant. [ABSTRACT FROM AUTHOR]

The effects of photoirradiation on the interfacial chemical reactions between indium tin oxide (ITO) films and layers of triphenylamine tetramer (TPTE) were investigated by using in situ x-ray photoelectron spectroscopy (XPS). Thin TPTE layers deposited onto sputter-deposited ITO films were irradiated with violet light-emitting diodes (peak wavelength: 380 nm). Shifts in the peak positions of spectral components that originated in the organic layer toward the higher binding-energy side were observed in the XPS profiles during the early stages of irradiation. No further peak shifts were observed after additional irradiation. An increase in the ratio of the organic component in the O 1s spectra was also observed during the photoirradiation. The ratio of the organic component increased in proportion to the cube root of the irradiation time. These results suggest that photoirradiation induces an increase in the height of the carrier injection barrier at the interface between TPTE and ITO in the early stages of the irradiation, possibly due to the rapid diffusion controlled formation and growth of an oxidized TPTE layer, which is considered to act as a high resistance layer. [ABSTRACT FROM AUTHOR]

We present direct measurements of spatial and spectral resolution of cryogenic distributed readout imaging detectors (DROIDs). The spatial and spectral resolutions have been experimentally determined by scanning a 10 μm spot of monochromatic visible light across the detector. The influences of the photon energy, bias voltage, and absorber length and width on the spatial and spectral resolutions have been examined. The confinement of quasiparticles in the readout sensors (superconducting tunnel junctions) as well as the detector’s signal amplitude can be optimized by tuning the bias voltage, thereby improving both the spatial and spectral resolutions. Changing the length of the absorber affects the spatial and spectral resolutions in opposite manner, making it an important parameter to optimize the DROID for the application at hand. The results have been used to test expressions for photon energy, position, and spatial and spectral resolutions which have been derived by using an existing one-dimensional model. The model is found to accurately describe the experimental data, but some limitations have been identified. In particular, the model’s assumption that the two sensors have identical response characteristics and noise, the approximation of the detailed quasiparticle dynamics in the sensors by border conditions, and the use of a one-dimensional diffusion process is not always adequate. [ABSTRACT FROM AUTHOR]

Temperature dependent rotational diffusion of a nonpolar solute, 9-phenylanthracene (9-PA), and a dipolar solute, rhodamine 110 (R110), has been examined in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim+][PF6-]) and in a conventional solvent, glycerol. This study has been undertaken to explore how parameters such as solvent size and free volume influence solute rotation in the case of a nonpolar solute, 9-PA. To understand the role of specific solute-solvent interactions, similar measurements have been performed with a dipolar analogue, R110. It has been observed that the viscosity normalized reorientation times of 9-PA are longer by a factor of 1.4–1.6 in glycerol compared to those in [bmim+][PF6-]. While the most commonly used Stokes-Einstein-Debye hydrodynamic theory is not successful in explaining this experimental observation, Gierer-Wirtz and Dote-Kivelson-Schwartz quasihydrodynamic theories could rationalize this trend, albeit in a qualitative manner. Rotational diffusion of R110, on the other hand, follows an exactly opposite trend compared to 9-PA. The normalized reorientation times of R110 are longer by a factor of 1.3–1.4 in [bmim+][PF6-] compared to glycerol, which is due to the formation of stronger solute-solvent hydrogen bonds between the positively charged R110 and the ionic liquid. [ABSTRACT FROM AUTHOR]

Diffusion experiments of phosphorus (P), arsenic (As), and antimony (Sb) in high purity germanium (Ge) were performed at temperatures between 600 and 920 °C. Secondary ion mass spectrometry and spreading resistance profiling were applied to determine the concentration profiles of the chemically and electrically active dopants. Intrinsic and extrinsic doping conditions result in a complementary error function and box-shaped diffusion profiles, respectively. These profiles demonstrate enhanced dopant diffusion under extrinsic doping. Accurate modeling of dopant diffusion is achieved on the basis of the vacancy mechanism taking into account singly negatively charged dopant-vacancy pairs and doubly negatively charged vacancies. The activation enthalpy and pre-exponential factor for dopant diffusion under intrinsic condition were determined to 2.85 eV and 9.1 cm2 s-1 for P, 2.71 eV and 32 cm2 s-1 for As, and 2.55 eV and 16.7 cm2 s-1 for Sb. With increasing atomic size of the dopants the activation enthalpy decreases. This is attributed to differences in the binding energy of the dopant-vacancy pairs. [ABSTRACT FROM AUTHOR]

Irradiation of germanium (Ge) isotope heterostructures with 2.5 MeV protons have been performed at 550 °C. The applied proton flux was varied between 1.0 and 1.5 μA leading to various rates of Frenkel pair production. After irradiation, concentration profiles of the Ge isotopes were recorded by means of secondary ion mass spectrometry (SIMS). An inhomogeneous broadening of the isotope structure was observed. In addition to the effect of irradiation enhanced self-diffusion, an influence of the formation of microscopic defects on the detected broadening was ascertained. Atomic force and scanning electron microscopy show that the microscopic defects are most probably resulting from an aggregation of vacancies formed during irradiation. Numerical analysis of Ge profiles not disturbed by microdefect formation indicates a significant contribution of self-interstitials to self-diffusion under irradiation. [ABSTRACT FROM AUTHOR]

Simulations are performed to investigate the uniqueness of simultaneous determination of electronic transport properties (the carrier lifetime, the carrier diffusivity, and the front surface recombination velocity) of silicon wafers by laterally resolved modulated free carrier absorption (MFCA) and multiparameter fitting. The dependences of MFCA amplitude and phase on these transport properties at different pump-probe-beam separations and modulation frequencies are analyzed. The uncertainties of the fitted parameter values are analyzed by investigating the dependences of a mean square variance including both the amplitude error and phase error on corresponding electronic transport parameters. Simulation results show that the electronic transport parameters can be determined accurately through fitting experimental MFCA data carrying both frequency- and space-domain information of carrier diffusion to a rigorous MFCA model. Among the three transport parameters, the carrier diffusivity can be determined most precisely, with an uncertainty of less than ±5%, due to the highest sensitivity of the laterally resolved MFCA signal to the diffusivity. The highly accurate determination of the diffusivity further improves the precision of the carrier lifetime and the front surface recombination velocity values simultaneously determined via multiparameter fitting. Experiments were performed with a silicon wafer and the results were in good agreement with the theoretical simulations. [ABSTRACT FROM AUTHOR]

The adsorption and desorption kinetics of N2 on porous amorphous solid water (ASW) films were studied using molecular beam techniques, temperature programed desorption (TPD), and reflection-absorption infrared spectroscopy. The ASW films were grown on Pt(111) at 23 K by ballistic deposition from a collimated H2O beam at various incident angles to control the film porosity. The experimental results show that the N2 condensation coefficient is essentially unity until near saturation, independent of the ASW film thickness indicating that N2 transport within the porous films is rapid. The TPD results show that the desorption of a fixed dose of N2 shifts to higher temperature with ASW film thickness. Kinetic analysis of the TPD spectra shows that a film thickness rescaling of the coverage-dependent activation energy curve results in a single master curve. Simulation of the TPD spectra using this master curve results in a quantitative fit to the experiments over a wide range of ASW thicknesses (up to 1000 layers, ∼0.5 μm). The success of the rescaling model indicates that N2 transport within the porous film is rapid enough to maintain a uniform distribution throughout the film on a time scale faster than desorption. [ABSTRACT FROM AUTHOR]