Effect Of Interfacial Energy Research Articles

Icosahedral supracrystal assembly from polymer-grafted nanoparticles via interplay of interfacial energy and confinement effect.

Self-assembly of nanoparticles (NPs) in drying emulsion droplets paves the way for intricate three-dimensional (3D) superstructures, given the myriad of control parameters for fine-tuning assembly conditions. With their substantial energetic dynamics that are acutely responsive to emulsion confinements, polymeric ligands incorporated into a system can enrich its structural diversity. Here, we demonstrate the assembly of soft polymer-grafted NPs into Mackay icosahedrons beyond spherical body-centered cubic (BCC) packing structures commonly observed for these soft spheres. This behavior is governed by the free energy minimization within emulsions through the interplay of the oil-water interfacial energy and confinement effect as demonstrated by the experimental observations of structural transitions between icosahedrons and BCC crystals and by corresponding free energy calculations. The anisotropic surface of the icosahedral supracrystals provides the capability of guiding the position of a secondary constituent, creating unique hybrid patchy icosahedrons with the potential to develop into multifunctional 3D clusters that combine the benefits of both polymers and conventional colloids.

Ultrahigh thermal conductance of the point contact between amorphous nanowires

Amorphous interfaces/contacts are ubiquitous in numerous micro/nanoelectronic devices and functional composite materials. Traditionally, the thermal resistance of interfaces/contacts was believed to be the primary impediment to heat transport. However, in this study, through measuring thermal resistance between crystalline-amorphous core-shell Ge nanowires, we unveil an ultrahigh thermal conductance across the point contact between the amorphous shell of Ge nanowires with a room-temperature value of 892 MW/m2-K. This value surpasses the typical values observed in point contacts between crystalline nanowires/nanoribbons by one to three orders of magnitude and even exceeds that of epitaxial interfaces between well-lattice-matched materials. Molecular and lattice dynamic simulations further reveal that the observed ultrahigh thermal conductance is attributed to the broadened vibrational bandwidths within the amorphous contact, which facilitates the redistribution of phonon energy into a state conductive to more effective interfacial energy transmission, leading to an enhanced overlap of phonon modes and, consequently, a heightened thermal conductance.

Optofluidic crystallithography for directed growth of single-crystalline halide perovskites

Crystallization is a fundamental phenomenon which describes how the atomic building blocks such as atoms and molecules are arranged into ordered or quasi-ordered structure and form solid-state materials. While numerous studies have focused on the nucleation behavior, the precise and spatiotemporal control of growth kinetics, which dictates the defect density, the micromorphology, as well as the properties of the grown materials, remains elusive so far. Herein, we propose an optical strategy, termed optofluidic crystallithography (OCL), to solve this fundamental problem. Taking halide perovskites as an example, we use a laser beam to manipulate the molecular motion in the native precursor environment and create inhomogeneous spatial distribution of the molecular species. Harnessing the coordinated effect of laser-controlled local supersaturation and interfacial energy, we precisely steer the ionic reaction at the growth interface and directly print arbitrary single crystals of halide perovskites of high surface quality, crystallinity, and uniformity at a high printing speed of 102 μm s−1. The OCL technique can be potentially extended to the fabrication of single-crystal structures beyond halide perovskites, once crystallization can be triggered under the laser-directed local supersaturation.

Extensive tip-splitting of injected organic liquid into an aqueous viscoelastic fluid

The injection of a fluid into another fluid causes a spatiotemporal pattern along the injection front. Viscous fingering is a well-known example when the replaced material is a viscous fluid. Notably, most fluids are, in reality, viscoelastic, i.e., they behave as an elastic solid over short timescales. For this reason, it is important to study the situation when the replaced fluid is viscoelastic. In this study, we observed a dynamics of fluids when an incompressible organic liquid was injected into an oleophilic Hele–Shaw cell filled with an aqueous viscoelastic fluid made of a wormlike micellar solution. We found extensive tip splitting of the injection front, which led to thin fingers with a characteristic size comparable to four times the cell thickness. We examined the material properties and suggest that the thin fingering pattern observed in our system is due to the delamination of viscoelastic fluid from the bottom substrate surface. Our result shows that the effect of interfacial energy in the existing solid layer should be considered in the injection process.

Influence of coupled dissolution-precipitation processes on the pore structure, characteristics, and evolution of tight sandstone: A case study in the upper Paleozoic reservoir of Bohai Bay Basin, eastern China

Due to the limitations of pore throat characterization techniques, in-depth studies on the evolution and influencing variables of tight sandstone reservoirs remain lacking, despite the importance of pore structure in evaluating their storage and seepage capacities. In this study, the effect of coupled dissolution–precipitation on the heterogeneity of the pore structure of tight sandstone was investigated using advanced techniques in conjunction with traditional geochemical analyses. The primary reasons for the variability in tight sandstone pore structure were different diagenetic processes and tectonic evolution. In tight sandstones, numerous burial phases led to a significant loss of porosity. However, tight sandstones that have been successively leached by meteoric water and deep burial organic acid have improved secondary pore space due to Yanshan tectonic uplift and Himalayan tectonic burial. The redistribution or blockage of pore space can occur as a result of dissolved material migrating and re-precipitating in tight sandstones that have been deeply buried and altered by organic acidic fluids. Furthermore, nuclear magnetic resonance cryoporometry and nuclear magnetic resonance experiments were used to provide precise and accurate quantitative analysis for discussing the evolution of pore structure by complex dissolution–precipitation process within the pore scale. The formation of good pore structure was mainly dependent on the increase in pore volume generated by dissolution in the submicron and micron range (less than 10 μm). Due to interfacial energy effects, authigenic minerals precipitated preferentially in macropores, resulting in a preponderance of microporosity and small changes in porosity but at least an order of magnitude reduction in permeability. This study provides a reliable reference for genesis analysis and evaluation of tight sandstones as well as a new perspective for understanding the formation and evolution of complex pore structures.

Precipitation strengthening of Cu–Ni–Si-based alloys: Experimental and computational insights

The effects of interfacial energy on precipitation behavior and physical properties of Cu–Ni–Si–(Co) alloys were investigated. The Cu–1.3Ni–0.3Si and Cu–1.3Ni–0.6Si–1.0Co alloys (in weight %) were prepared by combined cold-rolling and aging processes. The addition of Co promoted the formation of (Ni,Co)2Si by replacing Ni with Co in Ni2Si. Ab initio calculations demonstrated that the small addition of Co considerably reduced the interfacial energy between the Cu matrix and (Ni,Co)2Si, which effectively decreased the activation energy for precipitation. As a result, the precipitation of fine rod-shaped (Ni,Co)2Si was accelerated during the aging process and the number density of the precipitates increased up to 9.0 × 1010 cm−2. The nano-scale (Ni,Co)2Si precipitates with an average size of 13.5 nm strengthened the alloy properly through the Orowan mechanism without much loss of electrical conductivity. The maximum hardness and electrical conductivity were 220 Hv and 51 % International Annealed Copper Standard, respectively, for the Cu–1.3Ni–0.6Si–1.0Co alloy aged for 4 h at 420 °C.

Solution-Processed 1D Wurtzite ZnS Nanostructures with Controlled Crystallographic Orientation and Tunable Band-Edge Emission.

1D compound semiconductor nanomaterials possess unique physicochemical properties that strongly depend on their size, composition, and structures. ZnS has been widely investigated as one of the most important semiconductors, and the control of crystallographic orientation of 1D ZnS nanostructures is still challenging and crucial to exploring their anisotropic properties. Herein, a solution-processed strategy is developed to synthesize 1D wurtzite (w-)ZnS nanostructures with the specific <002> and <210> orientations by co-decomposing the copper dibutyldithiocarbamate {[(C4 H9 )2 NCS2 ]2 Cu, i.e., R2 Cu} and zinc dibutyldithiocarbamate (R2 Zn) precursors in the mixed solvents of oleylamine and 1-dodecanethoil. A solution-solid-solid (SSS)-Oriented growth mechanism is proposed, which includes oriented nucleation dominated and SSS growth dominated stages. The crystallographic orientation mainly depends on the interfacial energy and ligand effect. The 1D w-ZnS nanostructures with controlled crystallographic orientation display unique morphologies, i.e., <002>-oriented w-ZnS nanorod enclosed with {110} facets while <210>-oriented w-ZnS nanobelt enclosed with wide (002) and narrow (110) facets. The bandgap of 1D w-ZnS nanostructures can be tuned from 3.94 to 3.82eV with the crystallographic growth direction varied from <002> to <210>, thus leading to the tunable band-edge emission from ≈338 to ≈345nm.

Effects of interfacial energy on interfacial strength and work of adhesion in bcc-Fe tilt interfaces: A molecular dynamic study

Interfaces have been observed to play a vital role in improving the mechanical properties of layered structures. Many studies have indicated that at atomic scale, the interfacial energy can significantly influence the interface adhesion and hence, the mechanical properties. To investigate the relationship between the interfacial energy, atomic configuration, and tensile behaviour, we conducted molecular dynamics (MD) simulations of bcc-Fe interfaces. A total of 108 symmetric and asymmetric tilt interfaces on the <100> and <110> axes were constructed to achieve various interfacial energies. It was observed that the interfacial energy was dominated by the coherence of the interfacial atomic configuration. The tensile simulation results showed an approximately linear relationship between the interfacial strength and interfacial energy. This suggests that interfacial energy is the dominant factor. However, a higher variation in the interfacial energy effects on the work of adhesion was observed. This occurred because both interfacial energy and interfacial deformation behaviour affected the work of adhesion. In addition, twinning deformation and interfacial dislocations were observed in the low-energy coherent and high-energy disordered interfaces, respectively. This indicates that the interfacial atomic configuration determines the deformation behaviour, which, in turn, causes the interfacial property variations.

CNT effective interfacial energy and pre-exponential kinetic factor from measured NaCl crystal nucleation time distributions in contracting microdroplets.

Nucleation, the birth of a stable cluster from a disorder, is inherently stochastic. Yet up to date, there are no quantitative studies on NaCl nucleation that accounts for its stochastic nature. Here, we report the first stochastic treatment of NaCl-water nucleation kinetics. Using a recently developed microfluidic system and evaporation model, our measured interfacial energies extracted from a modified Poisson distribution of nucleation time show an excellent agreement with theoretical predictions. Furthermore, analysis of nucleation parameters in 0.5, 1.5, and 5.5 pl microdroplets reveals an interesting interplay between confinement effects and shifting of nucleation mechanisms. Overall, our findings highlight the need to treat nucleation stochastically rather than deterministically to bridge the gap between theory and experiment.

Antisolvent crystallization of ammonium dihydrogen phosphate (ADP) from aqueous solutions containing Al(III) and Fe(III) impurities by addition of ethanol

Experimental results of a study of the effect of concentration of Al(III) and Fe(III) ions on the metastable zone width (MSZW) of aqueous ADP saturated solutions, as determined by the maximum antisolvent content Δxmax in them for spontaneous three-dimensional (3D) nucleation, by feeding ethanol antisolvent to them at different rates RA and the nucleation and growth of crystals from these solutions are described and discussed. Crystal structure and segregation coefficients of impurity in the crystals were also studied by X-ray diffraction analysis and microwave plasma atomic absorption spectrometry, respectively. It was observed that: (1) the value of Δxmax for spontaneous 3D nucleation increases with an increase in ethanol feeding rate RA as well as impurity concentration ci, (2) the morphology and size of the ADP crystals changes with an increase in impurity concentration ci and antisolvent feeding rate RA, and (3) the effective segregation coefficients keff of the impurities in ADP crystals at a constant RA of ethanol feeding decreases with an increase in impurity concentration ci in the solution. The experimental data of the dependence of Δxmax on RA for solutions containing different impurity concentration ci were analyzed according to the approach based on the classical theory for 3D nucleation to calculate values of the preexponential factor A and the effective interfacial energy γeff of the theory, those of the morphology of ADP crystals from consideration of adsorption of impurity particles on the surfaces of growing crystals, and those of the dependence of segregation coefficient keff of the impurities on their concentration ci in the solution using a model based on competitive adsorption of solute and impurity molecules. It is argued that the formation of 3D nuclei of ADP during MSZW measurements and growth of these ADP nuclei as large crystals from aqueous solutions containing impurities and segregation of impurities in the crystals may be explained from consideration of different rates of ligand exchange of the surface-adsorbed complexes formed by interaction between univalently-charged cation complex present in aqueous solution and the H2PO4− ions of kinks in steps.

Interfacial and rheological investigation of enhanced oil recovery agents derived from Spirulina biomass

This study investigates interfacial and rheological properties of novel, Spirulina-based fluids developed for potential use in enhanced oil recovery (EOR) applications. The purpose of this investigation is to determine the driving mechanism(s) behind the EOR performance of these materials after a previous study concluded that the EOR fluids are a promising technology with up to 96% recovery of the original oil in place (OOIP). It was then hypothesized that the EOR mechanism arose from the interfacial energy effects and/or the rheological properties. In this study, Arthrospira platensis (Spirulina) biomass is modified by different denaturants (sodium hydroxide, citric acid, and urea) and tested for a wide range of interfacial and rheological properties. The interfacial properties include surface tension, interfacial tension with hydraulic oil, contact angle against silicon dioxide, and work of adhesion between the fluid and the silicon dioxide surface. The rheology focuses on determining fluid viscoelastic properties and flow behaviors. Additionally, this study compares and correlates the results amongst each other, which also includes pH, EOR performance, and denaturant concentration.The EOR performance of these fluids strongly correlates with the increased viscosity, reduced interfacial tension (IFT), and increased wettability in the EOR fluids. All of the investigated EOR solutions reduced the IFT. Most of the EOR solutions were found to be mostly shear-thinning with shear-thickening approximately in the 2,000–5,000 s−1 range. From the results, it is concluded that the performance of the different types of EOR fluids is based on different mechanisms. Sodium hydroxide-based fluids are driven by increased low-shear viscosity, reduced IFT, alkaline pH shift, and improved wettability. The citric acid-based fluids do not exhibit high viscosity values in the low shear range, which indicates that their EOR performance seems to be driven by reduced IFT, acidic pH shift, improved wettability, and increased fluid rigidity by the generation of crosslinks in the macromolecular structure. Urea-based fluids did not exhibit improved viscosity, which means that their modest EOR performance is likely driven by reduced IFT and improved wettability. While a shear-thickening rheology is often considered to be a mechanism for improving EOR, it is concluded that the shear-thickening effect is not a dominant mechanism for these fluids, especially since the highest performing EOR fluid (highest NaOH concentration) did not display shear thickening.

Assessment of interfacial energy effect on finite fracture behavior of composite adhesively bonded joints under four-point bending

Due to their remarkable advantages, composite adhesively bonded joints are intensively used in many engineering fields. There are many investigations performed by researchers to study the fracture behavior of the adhesively bonded joints. However, there exist discrepancies between the numerical predictions and the experimental results in some cases. This paper reports an investigation on the finite fracture behavior of composite adhesively bonded joints subjected to four-point bending. Experiments are performed for composite adhesively bonded joints with four different configurations. The fracture behavior is observed experimentally by utilizing a high-speed camera. The failure analysis employing the energy-stress coupled criterion is performed. The experimental results are compared with the numerical predictions by using an experimental-based approach where both geometric nonlinearity and interfacial energy are considered. Numerical illustrations are carried out to assess the effect of interface energy, geometric nonlinearity, joint type and dimensions on the fracture behavior of the considered bonded joints.

Modulating Exchange Bias, Anisotropic Magnetoresistance, and Planar Hall Resistance of Flexible Co/MnN Epitaxial Bilayers on Mica by Bending Strain.

The integration of ferromagnetic/antiferromagnetic bilayers with exchange bias effect on flexible substrates is crucial for flexible spintronics. Here, the epitaxial Co/MnN bilayers are deposited on mica by facing-target sputtering. A large in-plane exchange bias field (HEB) of 1800 Oe with a coercive field (HC) of 2750 Oe appears in the Co (3.8 nm)/MnN (15.0 nm) bilayer at 5 K after field cooling from 300 to 5 K. Effective interfacial exchange energy Jeff of the Co/MnN bilayer is 0.83 erg/cm2. The strain-induced maximum increase of HEB and HC reaches 18% and 21%, respectively, in the Co(3.8 nm)/MnN(15.0 nm) bilayer. Strain-modulated HEB is attributed to the change of interfacial exchange coupling between Co and MnN layers. HEB is inversely proportional to Co thickness but independent of MnN thickness. The change of HEB is less than 5% after 100 bending cycles, indicating mechanical durability. The out-of-plane exchange bias also appears since Co spins are not fully reversed due to the strong pinning effect. Anisotropic magnetoresistance (AMR) and planar Hall resistance (Rxy) show obvious hysteresis due to HEB. Exchange bias-induced phase difference of AMR and Rxy almost remains unchanged at different bending strains. The results provide the basis for understanding the bending strain tailored exchange bias.

A novel computational model for isotropic interfacial energies in multicomponent alloys and its coupling with phase-field model with finite interface dissipation

• A CALPHAD model for isotropic interfacial energies was developed and programmed. • Direct coupling between interfacial energy model and phase-field model was realized. • Isotropic interfacial energy databases in Ni-Al-Cr systems were established. • 3-D phase-field simulations of γ dendritic growth in two Ni alloys were conducted. • Effect of different interfacial energies on γ dendritic growth was analyzed. In this work, a novel computational model for the description of the temperature- and composition-dependent isotropic interfacial energy in multicomponent alloys was first developed in the framework of the CALculation of PHAse Diagram (CALPHAD) approach and implemented in a home-made code. By linking to the open-source code for interfacial energy calculation in alloys, OpenIEC, the databases for isotropic γ /liquid and γ / γ' interfacial energies in Ni-Al, Ni-Cr, Al-Cr, and Ni-Al-Cr systems were then efficiently established. After that, a direct coupling strategy between the current CALPHAD interfacial energy database and the phase-field model with finite interface dissipation was proposed and applied to three-dimensional (3-D) phase-field simulations of the primary γ dendritic growth in both Ni-Al and Ni-Al-Cr alloys during isothermal solidification. The effect of the interfacial energy on the morphology, tip growth rate, and partitioning coefficients in primary γ dendrites of binary Ni-Al and ternary Ni-Al-Cr alloys was investigated by comprehensively comparing the phase-filed simulation results using the composition-/temperature-dependent interfacial energies with those using the constant value. It is anticipated that the presently developed CALPHAD model for interfacial energy is of general validity for different multicomponent alloys and should be integrated with the phase-field model for quantitative simulation of their microstructure evolution.

Dissolution behavior, thermodynamic and kinetic analysis of malonamide by experimental measurement and molecular simulation

In this study, the solid structure, dissolution behavior, thermodynamic properties and nucleation kinetics of malonamide were explored. Firstly, the Hirshfeld surface analysis and molecular electrostatic potential surface were plotted to reveal the percentage contribution of various intermolecular contacts and location of the strongest hydrogen bond. Next, the solubility of malonamide in 12 solvents was determined by dynamic method at temperatures from 278.15 K to 318.15 K. Four thermodynamic models were applied to analyze solubility results. In addition, the thermodynamic properties were calculated to further analyze and discuss the dissolution behavior of malonamide. Moreover, the physicochemical properties of solvents were explored to express the solvent effects. The results illustrate “like dissolves like”, “mass transfer” and “solvent-solute interaction” rules play the synergistic effects on the dissolution process. The molecular dynamic simulation, including radial distribution function analysis and solvent free energy, was used to further explain the dissolution behavior. At last, the nucleation rate and effective interfacial energy in methanol solvent was measured and calculated to reveal the nucleation behavior.

Effective interfacial energy band engineering strategy toward high-performance triboelectric nanogenerator

Provided that electron transition ascribed to overlapping electron dominates the mechanism of contact electrification of triboelectric nanogenerators (TENGs), the electron transfer process occurs due to the built-up electric field between the triboelectrification surface and bottom electrode. In this work, we embed a solution-processed high-permittivity electron blocking layer (HPEBL) of LaZrO into the classical contact-separation mode TENG to build an energy barrier (ΔE > 1.3 eV) between ITO and PDMS, which could effectively block the transportation of electrons towards the bottom electrode. The surface potential decline rate of PDMS is obviously suppressed, extending the half-charge decay time by ∼3.1 times. A La0.1Zr0.9Ox HPEBL based TENG (H-TENG) demonstrates the electrical outputs with 215 V, 96.3 mA m−2 and 243.3 μC/m−2. Under the external load of 100 MΩ, the average gravimetric/volumetric power density and energy conversion efficiency can be calculated to be 59.34 μW g−1, 152.5 μW cm−3 and 39.2%, respectively. Furthermore, the dielectric behaviors of LaZrO thin films are investigated by metal–insulator-metal (MIM) devices. The Poole-Frenkel (PF) emission is found to dominate the leakage mechanism of LaZrO during operation. Consequently, increasing the relative permittivity and reducing the trap density could be indicated as the optimization orientation of HPEBL.

On the nucleation of ikaite (CaCO3x6H2O) – A comparative study in the presence and absence of mineral surfaces

The formation of ikaite (CaCO3x6H2O) was studied in the presence and absence of quartz and mica surfaces using desupersaturation curves from cryo-mixed-batch-reactor experiments. Upon nucleation and growth within the reactor, the solution approached solubility of the precipitating carbonate phase. For ikaite, a solubility constant of log Ksp ikaite = −7.3 ± 0.1 was found (T = 0 °C). At supersaturations Ωikaite < 15, the nucleation of ikaite was significantly promoted by the presence of quartz or mica. This promotion prevented a competing nucleation of anhydrous calcium carbonates. In the presence of quartz or mica, therefore, ikaite forms over a much broader supersaturation range than in the absence. Similarly strong promotors of ikaite nucleation rather than anhydrous carbonate nucleation were previously attributed to calcite-inhibiting substances only.At supersaturations Ωikaite ≥ 8, application of classical nucleation theory on induction periods of ikaite formation yielded an effective interfacial energy of 15 ± 3 mJ/m2. Compared to data of anhydrous CaCO3 phases, this interfacial energy is low and expresses the highly hydrated character of ikaite. At supersaturations Ωikaite ≥ 18, a transient amorphous phase appeared besides ikaite.Our results show that a comprehensive understanding of ikaite formation in natural settings requires consideration not only of supersaturation and presence of calcite-inhibitors but also of the presence or absence of mineral surfaces capable of promoting heterogeneous nucleation of ikaite.

Engineering self-floating Fe2O3/N,O-doped carbon foam as a bifunctional interfacial solar evaporator for synergetic freshwater production and advanced oxidation process

Interfacial solar-driven water evaporation is an appealing technology to mitigate freshwater crisis mainly caused by increasingly aggravated water pollution. Unfortunately, when polluted water is used, toxic organic pollutants might remain or even get enriched, leading to more serious water pollution. Herein, a self-floating bifunctional Fe2O3/N,O-doped carbon foam (FCF) evaporator is easily prepared by carbonization of waste polyester for simultaneous interfacial solar-driven water production and photocatalytic degradation of organic pollutants. The as-prepared FCF possesses low heat conductivity (0.074 W m−1 K−1), 3D interconnected pores, abundant functional groups as well as super-hydrophilicity, which impart FCF with fast water transport, high light absorptivity (98%), good photothermal conversion, and low vaporization enthalpy. Therefore, FCF presents high evaporation performance, e.g., 2.50 kg m−2 h−1 under 1 Sun irradiation, outperforming many advanced solar evaporators. Furthermore, the synergistic effect of heteroatom-doped carbon foam, Fe2O3 nanoparticle, and interfacial thermal energy is certified on the activation of peroxymonosulfate (PMS) to form diverse reactive oxide species (e.g., SO4•−), which promote the degradation of diverse organic dyes or mixed dyes. Compared with FCF and PMS systems, the rate constant of FCF + PMS system (3.79 ×10−2 min−1) is enhanced by 173.8 and 1.6 times, respectively. In outdoor experiments, the amount of freshwater production from per meter square (13 kg) satisfies with 5 adults’ daily water demand, and the dye degradation efficiency reaches 99.8%. The integration of advanced oxidation process into interfacial solar evaporation offers a promising strategy to simultaneously solve freshwater scarcity and sewage disposal.

Nanoparticle layer via UV-induced directional migration of iron-doped titania nanoparticles in polyvinyl butyral films and superior UV-stability

The migration of nanoparticles in polymer matrix is significant for the structure and performance of polymer nanocomposites after the initial formation. However, the understanding and controlling of migration of nanoparticles in polymer matrix remains a challenge. Herein, we report using ultraviolet (UV) light to perform the directional migration of inorganic nanoparticles in polymer film, generating an ultrathin (100–200 nm) nanoparticle layer on the light exposure surface of the film. The prepared iron-doped titania nanoparticles (Fe–TiO 2 ) are initially uniformly dispersed into polyvinyl butyral (PVB) film, and homogeneous distribution remains unchanged even after thermal treatment. However, the UV irradiation induces the directional migration of nanoparticles towards the illuminated surface. The mechanism indicates that the directional migration of nanoparticles is related with the increase of interfacial energy and conformational entropic effect between Fe–TiO 2 and PVB upon UV irradiation. The formed nanoparticle layer endowed the PVB/Fe–TiO 2 film with superior UV-stability. Our work extends the study of controlling migration of nanoparticles in polymer matrix by applying external stimuli, and provides a novel strategy for the functionalization of polymer nanocomposite materials. • Iron-doped TiO 2 nanoparticles with low photocatalytic activity is prepared. • UV-induced unidirectional migration of iron-doped TiO 2 nanoparticles in polyvinyl butyral is firstly reported. • The mechanism of UV-induced migration of nanoparticles is investigated in detail. • A nanoparticle layer formed on the exposed surface by UV-induced unidirectional migration of nanoparticles. • Nanoparticle layer imparted superior UV-stability to polymer nanocomposite film.

Simulation on in-situ crystal growth of lead-free solder Sn-57Bi alloy

Lead-free solder Sn-57Bi alloy is a good candidate material for electronic packaging. However, it is difficult to observe in-situ crystal growth process of Sn-57Bi alloy at high temperature and pressure environment. In this paper, based on the Monte Carlo method with the effect of volumetric and interfacial free energy taken into consideration quantitatively, a probability model for eutectic growth is established to simulate the in-situ crystal growth of Sn-57Bi alloy. The in-situ crystal growth of Sn-57Bi alloy at different undercoolings is studied. The simulation result shows the coupled growth of two phases in eutectic alloys, along with that lamellar spacing decreases and growth velocity increases with the increase of undercooling, agreeing with the reported experimental works on the eutectic growth. This work presents a good method to study the in-situ crystal growth process of alloys.