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The adsorbed film of Sodium Hexadecyl Sulfate (SHS) at the dodecane - water interface showed a first-order phase transition to a surface frozen monolayer upon cooling by the lateral van der Waals attraction between their hydrophobic tails and those of hexadecanol (C16OH) incorporated from the dodecane phase. The surface freezing transition of the SHS - C16OH monolayer was then utilized to stabilize an oil-in-water (OW) emulsion. The obtained results were compared to those examined previously for the cetyltrimethylammonium chloride (CTAC) - C16OH surface frozen monolayer. The main conclusion of this study was that the interfacial density of SHS significantly increased at the surface freezing by the cooperative adsorption with C16OH which gave rise to a higher surface freezing temperature (35°C) compared to CTAC (25°C). The formation of the surface freezing monolayer in the ambient temperature range could have a significant importance when it is applied to practical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] Currently, the bulk thermodynamic properties of an arbitrary liquid mixture of oligomers are accessible with reasonable accuracy through popular 3D statistical models (SAFT, Flory-Huggins) under a wide range of conditions. These models are implemented in widely available software suites used for process design. The hypothesis investigated here is that the same is, in principle, achievable with monolayers of mixed surfactants on liquid surfaces. A molecular thermodynamic theory of the adsorption of alkylphenoxypolyethoxyethanols, C n H 2 n +1 C 6 H 4 (OC 2 H 4) m OH, on fluid interfaces is presented. It covers homologues of m = 0–10; water|alkane and water|gas interfaces; single surfactants and surfactant mixtures. The adsorption behaviour has been predicted as a function of the structure of the ethoxylated surfactants and the model has been validated against tensiometric data for forty systems. All values of the adsorption parameters have been either predicted, independently determined, or at least compared to a theoretical estimate. The single surfactant parameters have been used to predict the properties of 'normal' Poisson distributed mixtures of ethoxylates, in good agreement with literature data. Partitioning between water and oil, micellization, solubility and surface phase transitions are also discussed. [ABSTRACT FROM AUTHOR]

When n-alkanes or n-alcohols coexist with surfactants that have similar chain lengths, they can form mixed surface-frozen films at the oil-water interface. In this review, we first explain the basic characteristics of this surface freezing transition mainly from a thermodynamic viewpoint. Then, we discussed the effect of surface freezing of a cationic surfactant (cetyltrimethylammonium chloride: CTAC) with tetradecane, hexadecane, or hexadecanol on the kinetic stability of the oil-in-water (O/W) emulsions. We show that the surface frozen film not only increases the kinetic stability of the O/W emulsions but also stably encapsulates coexisting organic molecules in the oil core. Finally, we will introduce one of our recent works in which we observed that the exchange between silica nanoparticles and CTAC molecules occurs at the surface of Pickering emulsions when the oil-water interfacial tension is lowered by the surface freezing. The resulting detachment of silica particles from the oil-water interface broke the Pickering emulsion. The advantages of controlling the stability of O/W emulsions via the use of surface-frozen film are discussed in comparison with normal surfactant emulsifiers in the conclusion part of the review. [Display omitted] • Adsorbed CTAC film underwent a first-order freezing transition upon cooling. • Surface-frozen film covering the OW emulsions enhanced their kinetic stability. • Coexisting organic molecules were expelled from the oil-water interface at surface freezing. • Interfacial tension drop by surface freezing induces the Pickering emulsion breaking. [ABSTRACT FROM AUTHOR]

A possible TOF-SIMS analysis of surface phase transitions has recently been proposed for limited cases such as polymers and ionic liquids. In the present study, we have extended this analysis to quench-condensed noble gas films. The newly developed cryogenic TOF-SIMS allowed both measurements of TOF-SIMS below 4 K, and low-energy ion scattering spectroscopy that is used to prepare a clean surface. It was found that the TOF-SIMS intensity variation by increasing the temperature at a constant ramp rate (temperature-programmed TOF-SIMS) shows steep changes due to sublimation. Thus, the possibility of analyzing the surface phase transition at the local region defined by the incident ion beam of (cryogenic) TOF-SIMS was demonstrated in the present study., (© 2024 John Wiley & Sons Ltd.)

The adsorbed film of Sodium Hexadecyl Sulfate (SHS) at the dodecane - water interface showed a first-order phase transition to a surface frozen monolayer upon cooling by the lateral van der Waals attraction between their hydrophobic tails and those of hexadecanol (C16OH) incorporated from the dodecane phase. The surface freezing transition of the SHS - C16OH monolayer was then utilized to stabilize an oil-in-water (OW) emulsion. The obtained results were compared to those examined previously for the cetyltrimethylammonium chloride (CTAC) - C16OH surface frozen monolayer. The main conclusion of this study was that the interfacial density of SHS significantly increased at the surface freezing by the cooperative adsorption with C16OH which gave rise to a higher surface freezing temperature (35°C) compared to CTAC (25°C). The formation of the surface freezing monolayer in the ambient temperature range could have a significant importance when it is applied to practical applications.

[Display omitted] We present a theory of the adsorption behaviour and phase transitions in monolayers of perfluoroalkylated alcohols, n-C n F 2 n + 1 C m H 2 m OH , at the water∣oil interface, and validate it for a range of temperatures and surfactant structures. The reason for the observed cohesive behaviour is identified as dispersion attraction between the fluorocarbon blocks. The London constant is determined from the increment of the lateral attraction parameter with the size of the fluorocarbon chain. The monolayers exhibit phase transition from liquid expanded state to van der Waals crystal. However, they are supercritical with respect to the gas–liquid transition. For the description of the liquid phase, we use the sticky disc model – fluid monolayer made of hard discs interacting with a short-ranged sticky potential. For the crystalline phase, a two-dimensional cell model is developed using the same interaction potential. This new model coincides with the empirical equation of state of Jura and Harkins, and ascribes physical meaning to its parameters. We extend the theory of Ivanov et al. for the adsorption constant K a to diblock molecules; it predicts accurately the dependence of K a and the adsorption heat on the surfactant structure. An invariant phase diagram of the monolayers is constructed. [ABSTRACT FROM AUTHOR]

In this work, computer modeling of the surface phase transition in semi-infinite antiferromagnetic systems under the influence of external magnetic field is carried out. Cases of different values for the surface exchange integral and exchange integral for interaction between surface spins and the first subsurface layer are considered. For the surface phase transition, as for the bulk transition, the Néel temperature decreases with increasing magnetic-field intensity according to the quadratic law. The rate of decrease in the transition temperature is determined by the ratio of exchange integrals on the surface and in the bulk. For each ratio of the exchange integrals, there is a magnetic-field intensity limit above which the surface of the system does not transit into the antiferromagnetic phase. The limiting value of the magnetic field for the surface transition is no lower than the same value for the bulk. There is an interval of the magnetic-field intensity in which the antiferromagnetic ordering of spins is possible only in a thin surface layer. A tricritical point on the system phase diagram is present at the same value of the ratio of the exchange integrals for all magnetic-field-intensity values. The tricritical temperature also decreases in accordance with quadratic law with increasing magnetic-field intensity. [ABSTRACT FROM AUTHOR]

Surface phase transitions in surfactant adsorption layers are known to affect the dynamic properties of foams and to induce surface nucleation in freezing emulsion drops. Recently, these transitions were found to play a role in several other phenomena, opening new opportunities for controlling foam and emulsion properties. This review presents a brief outlook of the emerging opportunities in this area. Three topics are emphasized: (1) the use of surfactant mixtures for inducing phase transitions on bubble surfaces in foams; (2) the peculiar properties of natural surfactants saponins, which form extremely viscoelastic surface layers; and (3) the main phenomena in emulsions, for which the surface phase transitions are important. The overall conclusion from the reviewed literature is that surface phase transitions could be used as a powerful tool to control many foam and emulsion properties, but we need deeper understanding of the underlying phenomena to fully explore these opportunities. Image 1 [ABSTRACT FROM AUTHOR]

We study the Bose-Einstein condensation in a tight-binding model with a hopping rate enhanced only on a surface. We show that this model exhibits two different critical phenomena depending on whether the hopping rate on the surface ts exceeds the critical value 5t / 4, where t is the hopping rate in the bulk. For ts/t<5/4, normal Bose-Einstein condensation occurs, while the Bose-Einstein condensation for ts/t≥5/4 is characterized by the spatial localization of the macroscopic number of particles at the surface. By exactly calculating the surface free energy, we show that for ts/t<5/4, the singularity of the surface free energy stems from diverging the correlation length in the bulk, while for ts/t≥5/4, it is induced by the coupling effects between the bulk and surface. [ABSTRACT FROM AUTHOR]

Surfaces are key elements of nanomaterials and catalysts. The main thermodynamic properties of surfaces are their chemical composition and energy. To determine the composition of the surface, there are a number of effective methods such as AES, XPS, TEM. Direct measurements of the interfacial free energy of “solid-gas” interface are practically not carried out. This is related to experimental difficulties. We have developed a method for in situ measurements of the surface energy of solid metals and alloys. We conducted the experiments on two-component Cu-based systems in an inert or reducing gas atmosphere. The measurements on Cu [Ag] and Cu [Co] solid solutions show the presence of phase transitions on the surfaces. The isotherms of the surface energy have singularities (the minimum in the case of copper solid solutions with silver and the maximum in the case of solid solutions with cobalt). In both cases, the surface phase transitions lead to the surface miscibility gap: a monolayer (multilayer) formation (Cu-Ag) or formation of nanoscale particles (Cu-Co). In accordance with the bulk phase diagrams, the concentration and temperature of the surface phase transitions correspond to the solid solution in the bulk. Experiments on similar systems (Cu-Fe, Cu-Pb) lead to the conclusion that in all peritectic systems, an increase in the surface energy by adding a component with a higher melting point and surface phase transitions “surface solid solution—two-phase surface with particles” should be expected. In eutectic systems, the component with a lower melting point decreases the surface energy and forms continuous layers. [ABSTRACT FROM AUTHOR]

Monte-Carlo computer simulation is employed to investigate the surface phase transition (PT) in the 3D semibounded antiferromagnetic Ising model. Simulation is performed at different ratios of exchange integrals on the system surface and in its bulk. The dependence between the PT temperature and the distance to the surface is studied. When the ratio of exchange integrals is less than 1.38, the PT temperature is found to increase with distance from the surface. A comparison with the results of a real experiment is carried out. The simulation results are demonstrated to be in qualitative and quantitative agreement with experimental data. [ABSTRACT FROM AUTHOR]

Phase transitions have been computer-simulated using the Monte Carlo method in the three-dimensional antiferromagnetic Ising model for the various ratios of the exchange integrals calculated over the surface and bulk of the system. The phase diagram of the system has been constructed. It has been shown that the phase diagram contains a phase in which the ordering of spins located on the surface takes place at a temperature below the Néel temperature. Contrary to the ferromagnetic Ising model, lines of phase transitions intersect at the tetracritical rather than tricritical point. The dependence of the surface critical exponents on the ratio of the exchange integrals has been obtained. It has been discovered that, at a ratio of the exchange integrals less than a certain value, the surface phase transition exhibits attributes of the phase transition of the third order. [ABSTRACT FROM AUTHOR]

We have measured surface energy in two-component Cu-based systems in H 2 + Ar gas atmosphere. The experiments on solid Cu [Ag] and Cu [Co] solutions show presence of phase transitions on the surfaces. Isotherms of the surface energy have singularities (the minimum in the case of copper solid solutions with silver and the maximum in the case of solid solutions with cobalt). In both cases, the surface phase transitions cause deficiency of surface miscibility: formation of a monolayer (multilayer) (Cu-Ag) or of nanoscale particles (Cu-Co). At the same time, according to the volume phase diagrams, the concentration and temperature of the surface phase transitions correspond to the solid solution within the volume. The method permits determining the rate of diffusional creep in addition to the surface energy. The temperature and concentration dependence of the solid solutions’ viscosity coefficient supports the fact of the surface phase transitions and provides insights into the diffusion properties of the transforming surfaces. [ABSTRACT FROM AUTHOR]

The paper reviews the most important achievements in the study of the surface-reconstruction phase transition on the low-index single crystals of Pt, Ir, and Au. A number of methods very sensitive to the surface layers are used to study the stable and metastable structures of the (100), (110), and (111) faces. Detailed consideration of the kinetics, critical parameters, activation energy, and geometrical models for 2D-surface phase transitions are presented. Main theoretical results based on the Ising 2D-model, calculations of the free energy with an embedded-atom method, and equilibrium Monte Carlo simulations are also given.

Abstract: Alkane droplets on aqueous solutions of surfactants exhibit a first-order wetting transition as the concentration of surfactant is increased. The low-concentration or “partial wetting” state corresponds to an oil lens in equilibrium with a two-dimensional dilute gas of oil and surfactant molecules. The high-concentration or “pseudo-partial wetting” state consists of an oil lens in equilibrium with a mixed monolayer of surfactant and oil. Depending on the combination of surfactant and oil, these mixed monolayers undergo a thermal phase transition upon cooling, either to a frozen mixed monolayer or to an unusual bilayer structure in which the upper leaflet is a solid layer of pure alkane with hexagonal packing and upright chains while the lower leaflet remains a disordered liquid-like mixed monolayer. Additionally, certain long-chain alkanes exhibit a surface freezing transition at the air–oil interface where the top monolayer of oil freezes above its melting point. In this review, we summarize our previous studies and discuss how these wetting and surface freezing transitions influence the line tension of oil lenses from both an experimental and theoretical perspective. [Copyright &y& Elsevier]

The structure of the clean Ge(110) surface is characterized between room temperature and the Ge melting temperature using scanning tunneling microscopy (STM) and low energy electron diffraction (LEED) and microscopy (LEEM). Rapid cooling from high temperature (~800°C) to room temperature yielded a surface composed of the c(8×10) reconstruction, {17 15 1} facets, and a previously unreported (8×2) reconstruction. Heating from room temperature to above 430°C extinguishes some, but not all, high-order LEED spots, indicating the presence of ordering up to at least 650°C. LEED observations of the phase transition between the c(8×10) and a disordered phase differ from earlier work but are consistent with previously published STM data. [ABSTRACT FROM AUTHOR]

Charged organic adsorbates play an important role in a number of electrochemical reactions, e.g. as additives for metal plating relevant for device fabrication in the semiconductor industry. Fundamental investigations are mandatory in order to acquire profound knowledge of the structural and electronic properties of these layers parallel and perpendicular to the surface, and to finally achieve a deeper mechanistic understanding of the kinetics of involved charge transfer reactions taking place at these complex metal/organic/electrolyte interfaces. A key structural motif of these interfaces consists in 'paired' (inorganic)anion/(organic)cation layers that can have an enormous stability even during an ongoing charge transfer reaction. In this contribution we present and discuss a selected case study on the co-adsorption of halide anions and cationic organic molecules that exhibit a pronounced redox activity. It will be demonstrated that their phase behavior at the interface crucially depends on both their particular redox-state and the surface concentration of the halide counter ions. The subtle balance between adsorbate–adsorbate and adsorbate–substrate interaction of the poly-cationic organic layer can be carefully controlled by potential dependent anion adsorption and desorption processes through the organic layer. This process can be followed by in situ high-resolution scanning tunnelling microscopy, while additional information about the structural and chemical state of the respective phase is obtained from in situ X-ray diffraction and ex situ photoelectron spectroscopy.

Abstract: Development of surface morphology in Si molecular beam epitaxy on mesa-structured Si(111) at temperatures around the (7×7)-“1×1” surface phase transition was studied by atomic force microscopy. Significant changes in surface morphology were found for a small increase in temperature near the surface phase transition, accompanied by a strong increase in step-free area dimension. This behavior is reported for the first time for epitaxial silicon growth, but supports earlier in situ studies of the thermal decay of 2-dimensional islands and voids on Si(111) close to the surface phase transition using low energy electron microscopy by Hibino et al. (Phys. Rev. B 63, 245402, 2001). The observed changes in surface morphology clearly demonstrate the interplay of crystal growth and the surface phase transformation. In particular, the simultaneous appearance of two surface phases under certain conditions and their specific influence on the growth behavior are discussed with regard to this matter. [Copyright &y& Elsevier]

The temperature-dependent conformational states of a monolayer film of ethylene glycol monododecyl ether (CE) at the air/water interface have been investigated using ellipsometry, surface tension, external reflection-absorption FTIR spectroscopy and two-dimensional infrared (2DIR) correlation analysis. The ellipticity coefficients and the entropy associated with CE adsorption changed almost discontinuously at certain temperatures, which manifested the interfacial phase transitions. The phase transition and coexistence of two phases were further clarified using 2DIR correlation analysis with temperature perturbation. The asynchronous correlation maps revealed that both bands of asymmetric and symmetric C-H stretching vibration in one-dimensional IR were split into two components, which confirmed the coexistence of two phases at the interface. [ABSTRACT FROM AUTHOR]

The reconstruction of SrTiO3(111) polar surface is investigated by scanning tunneling microscopy (STM) and electron diffractions. The (4×4), (6×6) and (5×5) reconstructions are prepared, and the evolution between them can be reversely controlled by adjusting the deposition dosage of Sr or Ti. Based on the STM height analysis and the optimal deposition dosage to obtain the monophased reconstructions, we conclude that the (4×4) reconstruction is based on SrO3 termination while the (6×6) and (5×5) are based on Ti termination. Their different polar compensation mechanisms as well as adsorption behaviors are also discussed. [ABSTRACT FROM AUTHOR]

Surface phase transitions of Lennard–Jones (LJ) based two- and four-site associating fluids have been studied for various associating strengths using grand-canonical transition matrix Monte Carlo simulations. Our results suggest that, in the case of a smooth surface, represented by a LJ 9-3-type potential, multiple-site associating fluids display a prewetting transition within a certain temperature range. However, the range of the prewetting transition decreases with increasing associating strength and increasing number of sites on the fluid molecules. With the addition of associating sites on the surface, a quasi-2D vapor–liquid transition may appear, which is observed at a higher surface site density for weaker associating fluids. The prewetting transition at lower associating strength is found to shift towards the quasi-2D vapor–liquid transition with increasing surface site density. However, for highly associating fluids, the prewetting transition is still intact, but shifts slightly towards the lower temperature range. Adsorption isotherms, chemical potentials and density profiles are used to characterize surface phase transitions. [ABSTRACT FROM PUBLISHER]

Abstract: The surface phase transition (SPT) line has been calculated at the Ga-rich side of the binary Ga–Tl system. The liquid alloys at a given temperature can be divided into the following four different regions as a function of Tl-content of the alloy: (i) at very low Tl-content one bulk Ga-rich alloy is obtained not covered by any nano-layer, (ii) at a somewhat higher Tl-content one bulk Ga-rich liquid phase is obtained, covered by a Tl-rich nano-layer, (iii) at medium Tl-content two bulk liquids are obtained, (iv) at high Tl-content one Tl-rich liquid is obtained with no nano-layer on it. An improved version of the Ga–Tl phase diagram is offered, showing the equilibrium SPT line and the region of the Ga-rich bulk liquid, covered by a Tl-rich nano-layer. The presence of the latter changes some physical properties of the system. Particularly, the temperature coefficient of the surface tension changes from a low negative value to a high positive value when increasing the Tl-composition of the alloy and the SPT line is crossed. The position of the SPT line is essential to control Marangoni convection in liquid monotectic alloys. [Copyright &y& Elsevier]

The atomic structure and stoichiometry of a solid surface dictates its physical and chemical properties, and hence plays a crucial role in the performance of a material in technological applications. Indeed, in the field of surface science, a significant proportion of studies address the determination of surface atomic geometries and associated phase transitions. From the theoretical side, the desire is to obtain a first-principles based description that can accurately predict arbitrary surface structures and phase transitions under various conditions, such as temperature, partial pressure, and adparticle coverage. In the present paper, we discuss recent theoretical approaches through various examples, which address this goal. In particular, ab initio atomistic thermodynamics, which affords determination of the surface free energy as a function of relevant atom chemical potentials, and varying pressure and temperature conditions, as well as more powerful schemes that combine first-principles quantum mechanical calculations with statistical mechanics, namely, the lattice-gas or cluster-expansion approach in combination with Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

Abstract: Scanning tunneling microscopy (STM) has been used to study the various possible structures of adsorbed Bi on the Cu(100) surface, after equilibration at a temperature of 520K. All of the structures previously identified by X-ray diffraction (lattice gas, c(2×2), c(9√2×√2)R45°, and p(10×10), in order of increasing Bi-coverage) were found to be present on a single sample produced by diffusing Bi onto the Cu(100) surface from a 3-d source. By investigating the possible coexistence of various pairs of phases, it was demonstrated that the c(2×2) phase transforms to the c(9√2×√2)R45° phase by a first order transition, whereas the transition from c(9√2×√2)R45° to p(10×10) is continuous. In addition, the structure of surface steps was studied as a function of Bi-coverage. The results showed that the presence of Bi changes the nature of the step–step interactions at the Cu(100) surface from repulsive to attractive. The attractive step–step interactions transform any small deviations from the nominal (100) orientation of the Cu substrate into (310) microfacets. When compared with the known equilibrium crystal shape (ECS) of Bi-saturated Cu, the observed microfaceting may imply that the ECS of Cu–Bi alloys is temperature dependent. [Copyright &y& Elsevier]

Abstract: The c(5√2×√2)R45°-Pb/Cu(100) surface phase is investigated by means of angle resolved ultraviolet photoemission and low energy electron diffraction in the temperature range between 300 and 550K. We identify and characterize a temperature-induced surface phase transition at 440K from the room temperature c(5√2×√2) R45° phase to a (√2×√2)R45° structure with split superstructure spots. The phase transition is fully reversible and takes place before the two-dimensional melting of the structure at 520K. The electronic structure of the split (√2×√2)R45° phase is characterized by a metallic free-electron like surface band. This surface band is backfolded with c(5√2×√2)R45° periodicity phase at room temperature, giving rise to a surface band gap at the Fermi energy. We propose that a gain in electronic energy explains in part the stability of the c(5√2×√2)R45° phase. [Copyright &y& Elsevier]

Abstract: The surface phase transition between GaAs(001)-c(4×4) and -(2×4)β2 surfaces is systematically investigated by using our ab initio-based approach. The phase diagram calculations for the c(4×4) surfaces as functions of temperature and As pressure reveal that three kinds of c(4×4) surfaces consisting of Ga–As dimers and/or Ga–Ga dimers become stable near the phase transition temperature. The electron counting Monte Carlo simulation and ab initio calculations are also performed to investigate the structural change of the c(4×4) surface after predepositing a 0.5 monolayer of Ga on the three kinds of c(4×4) surfaces. The calculated results suggest that the c(4×4) surfaces consisting of three Ga–As dimers or one Ga–Ga dimer and two Ga–As dimers in the (4×4) surface unit cell possibly change their structures to (2×4)β2 structures with Ga–As surface dimers. The conventional (2×4)β2 surface consisting of As dimers finally appears due to destabilization of Ga–As dimers at high temperature and high pressure. [Copyright &y& Elsevier]

Abstract: When a surface active component (B) is being gradually added to a component with a higher surface tension (A) at any constant temperature (being lower than the so-called surface critical point, ) in any A–B system with a miscibility gap, the first order surface phase transition (SPT) will occur at a certain bulk concentration of component B, within a one-phase, A-rich liquid region of the phase diagram. This SPT is connected with an abrupt change of the surface concentration of component B from a low value to a high value, i.e. with the formation of a thin film of a B-rich layer on the surface of the A-rich bulk liquid alloy. In this paper a general method is developed, based on the Butler equation, to calculate the equilibrium SPT line for any monotectic system, using optimized CALPHAD thermodynamic properties of the liquid alloy and the surface tension and molar volume values of the pure components, as initial data. This new SPT line should be included in all equilibrium phase diagrams with miscibility gaps, for which the point appears in the A-rich one-phase liquid region of the diagram. The behavior of liquid alloys is expected to be qualitatively different on the two sides of the SPT line. The temperature coefficient of the surface tension is shown to change its sign from negative to positive in the vicinity of the SPT line, which has a serious impact on the Marangoni convection of the alloy. The method is validated on the Ga–Pb system, for which a reasonable agreement is found between the calculated SPT line and the experimentally determined points, as published in 1998 by Chatain, Wynblatt and co-workers. The method of calculation is shown to be applicable for multi-component liquid alloys and solid solutions, as well. [Copyright &y& Elsevier]

The Ag/Si(1 1 1) √ of 3×√ of 3 structure is known as a honeycomb-chained-triangle (HCT) structure at room temperature and an inequivalent-triangle (IET) structure at low temperature (∼60 K). In this work, surface phase transition of Ag/Si(1 1 1) √ of 3×√ of 3 HCT to IET structure is studied by reflection high-energy electron diffraction (RHEED). Temperature dependence of RHEED rocking patterns were measured during cooling process of substrate, and the following results are obtained. RHEED rocking curves show continuous change during cooling process of the substrate and temperature dependence of rod intensities show discontinuity in their gradient at 150 K. Streak intensities of fractional spots at low temperature increases at low temperature, which suggests smaller domain size of √ of 3×√ of 3 structure caused by HCT to IET phase transition. It is concluded that critical temperature of structural phase transition from HCT to IET structure is 150 K. In addition, atomic arrangement of HCT structure at just above the critical temperature is different from that at room temperature but similar to IET structure just below the critical temperature except for stable rotation angle of Ag/Si triangles. It is considered that order–disorder transition of IET structure occurs at lower temperature than 120 K. [Copyright &y& Elsevier]

The surface phase transition of GaAs (0 0 1) from the As-rich 2×4 surface to the Ga-rich 4×2 surface and the reverse transition were analyzed in real-time using time-resolved core-level photoelectron spectroscopy incorporating the photoelectron diffraction effect. From the analysis of the time dependence of core-level photoelectron intensities and spectra, we found a large anisotropy in the intensities and spectra caused by the photoelectron diffraction effect. This anisotropy in the intermediate state of the transition from the 2×4 to the 4×2 differs from that of the reverse transition, indicating that the surface phase transition pathways differ. [Copyright &y& Elsevier]

The growth of epitaxial monolayers of perylene on Au(1 1 0) was investigated by means of scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). The preparation was done by molecular beam epitaxy (MBE). The experimental setup allowed us to perform LEED or STM measurements during evaporation. The pattern of the adsorbed perylene molecules shows several dosage-induced structural transitions, leading to a final coincident monolayer structure with uniform domain orientation and a low density of antiphase boundaries. The underlying Au(1 1 0) interface exhibits several different reconstructions, depending on the perylene coverage. [Copyright &y& Elsevier]

In the present paper, we investigate in deeper detail some features of the bistable behavior observed in micellar aggregates of gangliosides. In these systems, a collective transition takes place connected to different possible conformations of the glycosidic headgroup and resulting in different aggregation numbers for different thermal hystories. Light scattering experiments performed on mixed micelles indicate that it is the aggregated structure which dictates the conformation a ganglioside monomer assumes, among the allowed ones. Moreover, density measurements confirm the results previously obtained by DSC and show that the conformation of the hydrophobic tails at a given temperature is coupled to that of the headgroup. NMR measurements are consistent with previous results and, on a more local scale, indicate that the hydration of the ganglioside molecule is affected by the conformational transition. [Copyright &y& Elsevier]

The influence of the gas composition in the reducing atmospheres of bright annealing on the surface and corrosion characteristics of super duplex stainless steel tubes was investigated using a variety of experimental and analytical methods. This study showed that the addition of N 2 to the reducing atmosphere increased [N] pick up on the surface, promoting the phase transition to a single γ phase with a fine-sized δ remaining along the grain boundary of γ. The increase in partial pressure of N 2 in the reducing atmosphere resulted in a thicker single γ phase with Cr 2 N precipitates along the grain boundary of γ. The corrosion resistance decreased substantially as a result. On the other hand, after annealing in 100% H 2 at 1100 °C, some cracks with phase transformation to ɛ-martensite were formed mainly on the top surface region. The corrosion resistance of the annealed sample could be recovered only when the degraded surfaces had been removed, exposing the original phase structure with equivalent phase fractions of δ and γ. Based on the experimental results, more desirable bright annealing conditions for steel tubes with superior corrosion resistance are proposed. • Effects of bright annealing conditions on the surface properties of SDSS were examined. • The N 2 addition to the reducing atmosphere promoted the phase transition (γ + δ → γ). • The thicker γ phase with Cr 2 N precipitates is, more susceptible to pitting corrosion. • Bright annealing with 100% H 2 at 1100 °C causes H-induced cracking on outer-surface. [ABSTRACT FROM AUTHOR]

Mixed adsorbed film of cationic surfactant and linear alkane at the air-water interface shows two-dimensional phase transition from surface liquid to surface frozen states upon cooling. This surface phase transition is accompanying with the compression of electrical double layer due to the enhancement of counterion adsorption onto the adsorbed surfactant cation and therefore induces the thinning of the foam film at fixed disjoining pressures. However, by increasing the disjoining pressure, surfactant ions desorb from the surface to reduce the electric repulsion between the adsorbed films on the both sides of the foam film. As a result, the foam film stabilized by the surfactant-alkane mixed adsorbed films showed unique thickening transition on the disjoining pressure isotherm due to the back reaction to the surface liquid films. In this review, we will summarize all these features based on the previously published papers and newly obtained results. Unlabelled Image • Mixed adsorbed film of surfactant and alkane shows freezing transition upon cooling. • Surface freezing transition induces thinning transition of foam film. • Unique foam film thickening is observed with increasing disjoining pressure. • Mechanical strength of surface frozen film stabilizes the oil-in-water emulsions. [ABSTRACT FROM AUTHOR]

In-depth understanding interfacial failures and differentiating their contributions to the overall performance decay are in urgent need for cell design and optimization. Herein, with the focus on the frequently observed surface phase transition layer (SPTL) of LiCoO 2 layered cathode and by virtue of electrochemical tests and microstructure analysis, we systematically investigate the structural and chemical properties of LiCoO 2 SPTL under different cycling conditions and reveal that the LiCoO 2 SPTL does not contribute performance decay significantly. In comparison with Ni-contained LiNi 1-x-y Mn x Co y O 2 layered cathodes, LiCoO 2 SPTL shows two distinctive features. One is the porous morphology due to severe surface corrosion/dissolution and the other is the spinel-like lattice structure. The porous surface layer enables a percolating surface diffusion and the spinel structure offers a bulk diffusion for Li ions, which jointly leads to a minor blocking effect of Li ion during its intercalation/deintercalation. We experimentally verified that the LiCoO 2 SPTL is formed in the discharging process, particularly at lower discharge voltages. Our work deepens the understanding on the LiCoO 2 SPTL and its effect on the overall performance decay, which sheds new lights on the interfacial failures of layered cathodes. • Highlighted the difference of LiCoO 2 surface layer cycled at different voltages. • LiCoO 2 surface phase transition layer is formed during the discharge process. • LiCoO 2 surface layer is morphologically and structurally different from NMC. • LiCoO 2 surface phase transition layer has minor blocking effect to Li-ion. [ABSTRACT FROM AUTHOR]