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International audience; Wetting of polymer-grafted nanoparticles (NPs) in a polymer nanocomposite (PNC) film is driven by a difference in surface energy between components as well as bulk thermodynamics, namely, the value of the interaction parameter, χ. The interplay between these contributions is investigated in a PNC containing 25 wt % polymethyl methacrylate (PMMA)-grafted silica NPs (PMMA-NPs) in poly(styrene-ran-acrylonitrile) (SAN) upon annealing above the lower critical solution temperature (LCST, 160 °C). Atomic force microscopy (AFM) studies show that the areal density of particles increases rapidly and then approaches 80% of that expected for random close-packed hard spheres. A slightly greater areal density is observed at 190 °C compared to 170 °C. The PMMA-NPs are also shown to prevent dewetting of PNC films under conditions where the analogous polymer blend is unstable. Transmission electron microscopy (TEM) imaging shows that PMMANPs symmetrically wet both interfaces and form columns that span the free surface and substrate interface. Using grazingincidence Rutherford backscattering spectrometry (GI-RBS), the PMMA-NP surface excess (Z*) initially increases rapidly with time and then approaches a constant value at longer times. Consistent with the areal density, Z* is slightly greater at deeper quench depths, which is attributed to the more unfavorable interactions between the PMMA brush and SAN segments. The Z* values at early times are used to determine the PMMA-NP diffusion coefficients, which are significantly larger than theoretical predictions. These studies provide insights into the interplay between wetting and phase separation in PNCs and can be utilized in nanotechnology applications where surface-dependent properties, such as wettability, durability, and friction, are important.

The formation and evolution of silicene on ultrathin Au films have been investigated with low energy electron microscopy and diffraction. Careful control of the annealing rate and temperature of Au films epitaxially grown on the Si(111) surface allows for the preparation of a large scale, of the order of cm2, silicene sheets. Depending on the final temperature, three stages of silicene evolution can be distinguished: (i) the growth of the low buckled phase, (ii) the formation of a layered heterostructure of the low buckled and planar phases of silicene and (iii) the gradual destruction of the silicene. Each stage is characterized by its unique surface morphology and characteristic diffraction patterns. The present study gives an overview of structures formed on the surface of ultrathin Au films and morphology changes between room temperature and the temperature at which the formation of Au droplets on the Si(111) surface occurs.

For preparing high-performance electrospun fibers with functional molecules that cannot cross-entangle themselves, such as conductive polymers, promoting the aggregation of functional molecules on the surface by surface segregation is a promising approach. In the present study, electrospun polymethyl methacrylate/polyaniline (PMMA/PANI) fibers were prepared under various conditions, including solution composition, applied voltage, tip-to-collector distance, temperature, humidity, and gas-phase solvent concentration, to examine the effects of the parameters on fiber morphology and surface segregation. The changes in fiber morphology and variations in the intensity of PANI and PMMA’s characteristic bands were investigated with scanning electron microscopy (SEM) and Raman spectroscopy. The results demonstrated that by changing the saturation difference and the viscosity, the amount of PMMA and PANI added significantly influenced whether surface segregation could occur. The effect of other investigated parameters on surface segregation was concluded to alter the molecular migratable time by affecting the jet flight time and the solvent volatilization rate. Among them, increasing the solvent concentration could significantly promote surface segregation without sacrificing morphological advantages. When the solvent concentration increased from 1.4 to 158 mg/m3, the Raman peak intensity ratio of PANI and PMMA increased from 2.91 to 5.05, while the fiber diameter remained essentially constant.

Relative concentrations of nickel and copper at the surface of the ring and centre parts of 1-peso and 2-pesos Argentine coins have been studied by means of X-ray photoemission spectroscopy (XPS). It has been observed Ni-enrichment at the surface of the ring (silvery) part of a 1-peso, minted in 1994, whereas the XPS data reveals lack of nickel at the surface of the centre (silvery) part of a 2-pesos, minted in 2016. This discrepancy is explained by analyzing the XPS peaks of oxygen and carbon, and is suggested to be related to the contamination layer on the surface of the coins. The XPS analysis of the golden parts of the coins, namely the centre part of the 1-peso and the ring part of the 2-pesos coins were inconclusive, due to the small amount of the Ni (nominally %2) used in those parts. The possible oxidations states of the metals at the surface of the untreated and treated coins with the artificial human sweat were also identified. Fil: Gard, Faramarz Sahra. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Materiales (CAC); Argentina Fil: Duffó, Gustavo Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Materiales (CAC); Argentina. Universidad Nacional de San Martín; Argentina Fil: Bergamasco, Pablo. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Materiales (CAC); Argentina Fil: Forlerer, Elena. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Materiales (CAC); Argentina

Membrane fouling is one of the main bottlenecks in membrane separation processes for water purification. Due to the complexity of foulants, engineering the membrane surface to coordinate multi-defense mechanisms is essential for fabricating membranes with broad-spectrum antifouling performance. In this study, we synthesized a heterostructured modifier comprising zwitterionic, fluorine-containing polymeric segments and inorganic silver nanoparticles. The heterostructured modifiers were synergistically segregated to the membrane surface during non-solvent induced phase separation. A dual-heterogeneous surface structure was formed, compromising physicochemical heterogeneity with hydrophilic-low surface energy-antibacterial domains, as well as topological heterogeneity with nanopapillae. Consequently, multi-defense mechanisms including passive fouling resistance, fouling release and active antibacterial mechanisms were integrated to the membrane surface, leading to superior antifouling performances against oil-in-water emulsions with ultralow total flux decline ratio of 3.3% and the flux recovery ratio of nearly 100%, as well as nearly 100% antibacterial activity against E. Coli with an obvious inhibition zone.

Al-Ti-based alloys are of enormous technical relevance due to their specific properties. For studies in atomic dynamics, surface physics and industrial processing the precise knowledge of the thermophysical properties of the liquid phase is crucial. In the present work, we systematically measure mass density, ρ (g cm−3), and the surface tension, γ (N m−1), as functions of temperature, T, and compositions of binary Al-Ti melts. Electromagnetic levitation in combination with the optical dilatometry method is used for density measurements and the oscillating drop method for surface tension measurements. It is found that, for all compositions, density and surface tension increase linearly upon decreasing temperature in the liquid phase. Within the Al-Ti system, we find the largest values for pure titanium and the smallest for pure aluminum, which amount to ρ(L,Ti) = 4.12 ± 0.04 g cm−3 and γ(L,Ti) = 1.56 ± 0.02 N m−1; and ρ(L,Al) = 2.09 ± 0.01 g cm−3 and γ(L,Al) = 0.87 ± 0.06 N m−1, respectively. The data are analyzed concerning the temperature coefficients, ρ T and γ T, excess molar volume, V E, excess surface tension, γ E, and surface segregation of the surface active component, Al. The results are compared with thermodynamic models. Generally, it is found that Al-Ti is a highly nonideal system.

The segregation kinetics of surface-active, residual elements are investigated in an in situ study of annealing scrap-based silicon electrical steel sheet where the arsenic (As) surface segregation is highlighted. During annealing in the temperature range of 300&ndash, 950 &deg, C, different kinds of interactions between the segregated residual elements were observed. Attractive interactions between the segregands produced co-segregation, e.g., between Sn and Sb, whereas repulsive interactions resulted in site competition, e.g., between Sn and As. These competing interactions are strongly time dependent. In spite of there being twice as much Sn compared to As in the bulk material, the As prevailed in the surface enrichments of the polycrystalline silicon steel at 950 &deg, C. The intensity of the As surface segregation in the temperature range 800&ndash, C is proportional to the calculated amount of &gamma, austenite phase in the (&alpha, + &gamma, ) steel matrix. The detected phenomenon of the As versus Sn site competition could be valuable for the texture design and surface engineering of silicon steels with a thermodynamically stable two-phase (&alpha, ) region.

The alloy Au-Ag system is an important noble bimetallic phase, both historically (as "Electrum") and now especially in nanotechnology, as it is applied in catalysis and nanomedicine. To comprehend the structural characteristics and the thermodynamic stability of this alloy, a knowledge of its phase diagram is required that considers explicitly its size and shape (morphology) dependence. However, as the experimental determination remains quite challenging at the nanoscale, theoretical guidance can provide significant advantages. Using a regular solution model within a nanothermodynamic approach to evaluate the size effect on all the parameters (melting temperature, melting enthalpy, and interaction parameters in both phases), the nanophase diagram is predicted. Besides an overall shift downward, there is a "tilting" effect on the solidus-liquidus curves for some particular shapes exposing the (100) and (110) facets (cube, rhombic dodecahedron, and cuboctahedron). The segregation calculation reveals the preferential presence of silver at the surface for all the polyhedral shapes considered, in excellent agreement with the latest transmission electron microscopy observations and energy dispersive spectroscopy analysis. By reviewing the nature of the surface segregated element of different bimetallic nanoalloys, two surface segregation rules, based on the melting temperatures and surface energies, are deduced. Finally, the optical properties of Au-Ag nanoparticles, calculated within the discrete dipole approximation, show the control that can be achieved in the tuning of the local surface plasmon resonance, depending of the alloy content, the chemical ordering, the morphology, the size of the nanoparticle, and the nature of the surrounding environment.

In this paper the surface zone formation during direct chill casting of aluminum billets, produced by the air slip technology, is discussed. The shell zone depth and compositions have been quantitatively studied, and the surface microstructures of 6060, 6005 and 6082 alloys are compared and coupled to surface appearances. The understanding of the results is based on the exudation of liquid metal through the mushy zone and the fact that the exudate liquid is contained within a surface oxide skin, and the oxide skin movements are coupled to various surface appearances. The major defects that occur during billet castings are different kinds of vertical drags or horizontal bandings, also called lapping. The structures coupled to these defects and theories for their formation are discussed.

cited By 11; International audience; Surface segregation designates the phenomenon of variation in chemical composition between the surface and the bulk of an alloy, which can have a beneficial or detrimental effect on its physical and chemical properties. This is even more pronounced in nanoalloys, i.e., alloy systems comprised of nanoparticles, with significant surface-to-volume ratios. In this case study we demonstrate the element-specific Cr segregation in Ni-rich NiCr alloy nanoparticles and nanogranular films grown by gas-phase synthesis methods. In situ annealing measurements (300-800 K), performed under vacuum using aberration-corrected environmental transmission electron microscopy (E-TEM), and vibrating sample magnetometry (VSM) revealed progressive Cr segregation with annealing temperature and subsequent complete transformation into core-satellite structures at 700 K. Simultaneously, atomistic computer simulations (molecular dynamics (MD) and Metropolis Monte Carlo (MMC)) elucidated the resultant structures, explaining the driving force behind segregation energetically. Most importantly, we emphasize the significant effects of Cr segregation on magnetic properties, namely, (i) the highly nonsaturated M-H loops (below the Néel temperature of antiferromagnetic Cr) with reduced coercivities and (ii) the uncompensated high Curie temperatures, TC, compared to the NiCr bulk, which approach bulk Ni values upon annealing. Both are clear evidence that the distribution of Cr in the nearest-neighbor shells of Ni atoms differs from that of the bulk NiCr alloy, reconfirming our structural findings.

The degradation mechanism of La0.6Sr0.4Co0.2Fe0.8O3 − δ (LSCF) electrode is investigated by examining its electrochemical behavior under equilibrium potential at elevated temperature and corresponding surface compositional changes. Diluted nitric acid etching treatment is conducted to confirm the correlation between the surface changes and the variation of electrochemical performance. It has been shown that the increase of polarization resistance of LSCF electrode has a linear dependence on the square root of time and arises from degradation of mass transfer process taking place at the gas-solid interface of electrode, such as oxygen adsorption/desorption and surface diffusion. Comparison of the behavior of the electrode before and after nitric acid treatment shows that the presence of surface inhibited species can account for the above observations. This inhibited species is confirmed by X-ray photoelectron spectroscopy to be a surface segregated Sr-based material, which supports the claim that surface Sr segregation is detrimental. A further lifespan study of LSCF electrode up to 158 h under 1 A/cm2 electrolysis current demonstrates that the current can improve and stabilize the performance, which could be ascribed to the removal of surface Sr species due to the incorporation of surface Sr back into the lattice of LSCF. NRF (Natl Research Foundation, S’pore) Published version

Lattice strain is a relatively unexplored route to modify the degradation effects in functional oxides for high temperature electrochemical devices. In this paper, we present results on the segregation of Gd to the surface of strained Gd0.1Ce0.9O2-δ films using low energy ion scattering to assess the surface composition. The potential for strain-modified segregation is discussed as well as the challenges in studying and implementing it. This article is protected by copyright. All rights reserved.

Epitaxial strain alters the physical properties of thin films grown on single crystal substrates. Thin film oxides are particularly apt for strain engineering new functionalities in ferroic materials. In the case of La2/3Ca1/3MnO3 (LCMO) thin films, here we show the first experimental images obtained by electron holography demonstrating that epitaxial strain induces the segregation of a flat and uniform nonferromagnetic layer with antiferromagnetic (AFM) character at the top surface of a ferromagnetic (FM) layer, the whole film being chemical and structurally homogeneous at room temperature. For different substrates and growth conditions the tetragonality of LCMO at room temperature, defined as τ = |c – a|/a, is the driving force for a phase coexistence above an approximate critical value of τC ≈ 0.024. Theoretical calculations prove that the increased tetragonality changes the energy balance of the FM and AFM ground states in strained LCMO, enabling the formation of magnetically inhomogeneous states. This work gives the key evidence that opens a new route to synthesize strain-induced exchanged-biased FM–AFM bilayers in single thin films, which could serve as building blocks of future spintronic devices., This work was supported by Spanish Ministry of Science through projects No. MAT2011-28532-C03-02 and MAT2011-27553-C02 including FEDER funding, by the Aragon Regional Government through projects E26 and CTPP4/11, by the Universidad de Zaragoza through the contract PIF-UZ-2009-CIE-02, and by the European Union under the Seventh Framework Programme under a contract for an Integrated Infrastructure Initiative Reference 312483-ESTEEM2.

In the present paper, the formation of columnar and layered structure during co-deposition of binary thin films is analyzed by kinetic modeling. The kinetic model is based on phase field theory and involves the main processes taking place during binary film growth: adsorption, phase separation, Gibbsian surface segregation, surface and bulk diffusion. The process of phase separation is defined by the Cahn&ndash, Hilliard equation, which describes well the kinetics of formation of nanoparticles in binary system with a limited solubility of components. The formation of columns and layers can occur only if other processes such as diffusion and segregation take place. In this paper, the most attention is paid to the formation of multilayered structures during binary components co-deposition, which is experimentally observed, but whose mechanism of formation is not well understood. In the work presented, the mechanism of formation of layers is shown, and the conditions at which this mechanism starts to work are formulated. It is shown that very important aspects are surface segregation of one of the components and depth dependent diffusion.

This special issue “Polymeric Materials: Surfaces, Interfaces and Bioapplications” was proposed to cover all the aspects related to recent innovations on surfaces, interfaces and bioapplications of polymeric materials. The collected articles show the advances in polymeric materials, which have tremendous applications in agricultural films, food packaging, dental restoration, antimicrobial systems and tissue engineering. We hope that readers will be able to enjoy highly relevant topics that are related to polymers. Therefore, we hope to prove that plastics can be a solution and not a problem., This research was funded by MINECO, Project MAT2016-78437-R, the Agencia Estatal de Investigación (AEI, Spain) and Fondo Europeo de Desarrollo Regional (FEDER, EU)., We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)

X-ray photoelectron spectroscopy (XPS) has been used to explore the cation rearrangement between the surface and bulk of grains and the surface chemical states of Ce, Mn, Co, Sr, and O ions in the single phase CeO 2 -based solid solutions and in the two phase (100 − x )La 0.6 Sr 0.4 CoO 3 – x CeO 2 (LSCC x ) and (100 − x )La 0.8 Sr 0.2 MnO 3 – x CeO 2 (LSMC x ) composites. The well-resolved Ce 3 d 5/2 and Ce 3 d 3/2 spin–orbit components were determined to study the Ce 4+ to Ce 3+ electronic transition at the surface. The surface of the LSCC x and LSMC x ( x = 8–40 mol%) composites is depleted in cerium. Both Ce 4+ and Ce 3+ cations were revealed. The surface fraction of Ce 4+ cations increases with the rise in CeO 2 content in both systems, but it is higher by about a factor of two in the LSCC composites. A strong enrichment of the surface by Co cations was observed for the composites LSCC x ( x = 8–40 mol%), implying that the presence of cerium could facilitate the Co surface segregation. A slight Sr surface enrichment compared to the nominal stoichiometry was found for La 0.6 Sr 0.4 CoO 3 , CeO 2 -based solid solutions, LSCC57, and LSMC x ( x = 10–57) composites. In contrast, the surface of the LSCC x ( x = 10–37) composites is slightly depleted in strontium cations. The O 1 s spectra of the LSCC and LSMC composites contain several contributions associated with the lattice oxygen related to the phases with the perovskite and fluorite structures as well as with different surface states. Their contributions vary with CeO 2 content and a chemical origin of the transition metal cations on the B-site in the perovskite structure. The Ce 2 (CO 3 ) 3 -based phase seems to exist at the surface of grains and crystallites in the LSCC57 and LSCM composites.

Laser-induced alloying effects on the composition and structure of different Ni/Ti multilayer structures were studied. Thin films composed of one, five, and ten (Ni/Ti) bilayers were deposited by DC ion sputtering on (1 0 0) Si wafers. Laser irradiations were performed by 150 ps pulses of a Nd:YAG laser operating at 1064 nm. The samples were characterized by Rutherford backscattering spectrometry (RBS), Auger electron spectroscopy (AES), X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). At a laser fluence of 0.9 J cm(-2), interaction between Ni and Ti layers was initiated, and NiTi alloy formed in 5- and 10-bilayered samples. Progressed alloying was achieved at a laser fluence of 1.2 J cm(-2). The alloy was formed mostly within the heat affected zone (HAZ) of the sample. Surface segregation of titanium was followed by formation of a 25 nm thin TiO2 film on the surface of the multilayered structures. In addition, parallel periodic surface structures on the surfaces of the 5- and 10-bilayered samples were clearly recorded. Their period in the case of the 5-bilayered system (0.77 mu m) agrees very well with the predictions of the common theory, whereas, in the case of the 10-bilayered system, two periods of such structures are observed (1.43 mu m and 0.4 mu m), and none of them coincides with the prediction. (C) 2012 Elsevier B. V. All rights reserved.

CuNi bimetallic alloy particles supported on CeO2 are prepared by coprecipitation of the corresponding salt precursors followed by calcination and hydrogen reduction. The supported alloy particles are characterized by PXRD, H2-TPR, XPS, XANES and EXAFS techniques. The PXRD study shows that copper rich oxide phases supported on CeO2 are reduced at 200 �C. However, complete reduction of CuO-NiO phases occurs at 450 �C forming CuNi alloy particles on CeO2. The H2-TPR results show that mixed oxides are reduced at higher temperatures than pure components indicating strong wetting between oxide components and CeO2. The Ni 2p XPS shows stronger interaction between Ni2+ and CeO2 support. XANES and EXAFS studies show the formation of CuNi alloy particles with small surface segregation of Cu. The catalytic activity of the supported CuNi alloy particles is studied by non-oxidative dehydrogenation of cyclohexanol to cyclohexanone reaction. The effect of temperature, contact time and time on stream are examined to gain insights into the catalytic activity of the CeO2 supported CuNi alloy catalysts. Among all the CuNi alloy compositions, CuNi(1:1)/CeO2 catalyst shows higher catalytic activity and selectivity to cyclohexanone. Formation of stable CuNi alloy particles on CeO2 by alloy-redox support interaction and segregation of Cu are crucial factors for catalytic activity. � 2012 Elsevier B.V.

Self-assembled InAs/CaAs quantum dot (QD) heterostructures grown by solid state molecular beam epitaxy (MBE) were subjected to growth ripening pause of comparatively shorter durations (0-50 s) at the growth temperature (520 degrees C). The islands are found to increase in size with the growth pause and correspondingly their density decreases. Though the photoluminescence spectra of the islands subjected to growth pause is found to follow conventional QD systems, a contradiction is noticed in the calculated values of the activation energy of the dots. We ascribed this contradiction due to the poor crystalline quality of the ripened QDs as a result of desorption and sublimation of indium during the pause at high growth temperature. (C) 2011 Elsevier Ltd. All rights reserved.

The systems containing highly reactive element such as Ti are the most difficult to be determined experimentally and therefore, it is often necessary to estimate the missing values by theoretical models. The thermodynamic data of the Al–Ti system are scarce, its phase diagram is still incomplete and there are very few data on the thermophysical properties of Al–Ti melts. The study on surface, dynamic and static structural properties of liquid Al–Ti alloys has been carried out within the framework of the Compound Formation Model. In spite of the experimental difficulties, the surface tension of liquid Al–2 at.%Ti alloy has been measured over a temperature range by the pinned drop method.

Cataloged from PDF version of article. In the current contribution, we provide a direct demonstration of the thermally induced surface structural transformations of an alkaline-earth oxide/transition metal oxide interface that is detrimental to the essential catalytic functionality of such mixed-oxide systems toward particular reactants. The BaO(x)/TiO(2)/Pt(111) surface was chosen as a model interfacial system where the enrichment of the surface elemental composition with Ti atoms and the facile diffusion of Ba atoms into the underlying TiO(2) matrix within 523-873 K leads to the formation of perovskite type surface species (BaTiO(3)/Ba(2)TiO(4)/Ba(x)Ti(y)O(z)). At elevated temperatures (T > 973 K), excessive surface segregation of Ti atoms results in an exclusively TiO(2)/TiO(x)-terminated surface which is almost free of Ba species. Although the freshly prepared BaO(x)/TiO(2)/Pt(111) surface can strongly adsorb ubiquitous catalytic adsorbates such as NO(2) and CO(2), a thermally deactivated surface at T > 973 K practically loses all of its NO(2)/CO(2) adsorption capacity due to the deficiency of surface BaO(x) domains.

The use of the sequential electroless plating method allowed us to obtain the PdAgCu ternary alloy on top of dense stainless steel (SS) 316 L disks. The XRD analysis indicated that initially the nucleation of the two phases of the alloy (FCC and BCC) takes place, but the FCC/BCC ratio increases with the annealing time at 500 °C in H2 stream. After 162 h, the film contained only the FCC phase, which presents promising properties to be applied in the synthesis of hydrogen selective membranes. SEM cross-section results showed that a dense, continuous, defect-free film was deposited on top of the SS support, and the EDS data indicated that no significant gradient was present on the thickness of the film. XPS and LEIS allowed us to determine that Cu and Ag surface segregation takes place after annealing up to 500 °C/5 days. In the top-most surface layer, Ag enrichment takes place as determined by ARXPS experiments which can be the result of the lower surface tension of Ag compared to that of Cu and Pd. Increasing the annealing temperature results in an increase of the Ag surface segregation while the Cu concentration in the top-most surface layer decreases. Fil: Tarditi, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina Fil: Cornaglia, Laura Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina

An attempt has been made to predict the segregation of carbon in continuously annealed hot-rolled low-carbon aluminum-killed steel (LCAK) through thermodynamic calculations. It is found that the surface carbon content calculated by the Guttmann model is comparable with the experimental results for inert atmosphere condition, whereas a large discrepancy is observed for the conventional continuous annealing furnace atmosphere. The main reason for this difference is the water-gas reaction that takes place on the surface of the steel sheet. It is proposed that this reaction, along with furnace atmosphere, determines the extent of carbon content on the sheet's surface. Based on this, the surface carbon content for various furnace conditions could be predicted. � 2010 Elsevier B.V.

Galvanized hot rolled steel sheets are inferior to cold rolled sheets because of the segregation of carbides at the surface/sub-surface region. In order to change the distribution of the carbides at the surface/sub-surface region, continuous annealing/reheating operation is carried out at different temperatures prior to the galvanizing operation. The reheating temperature maintained in continuous annealing line is the main factor which redistributes the carbides at the surface/sub-surface region. At intercritical annealing temperature all the carbides get dissolved into the matrix and the surface became suitable for galvanizing reaction. The reducing atmosphere also plays an important role to remove all the room temperature oxides present at the surface. Thus, a combination of proper temperature and reducing atmosphere leads to the proper galvanizing on the hot rolled steel surface. � 2009 Elsevier B.V. All rights reserved.

The thermodynamic properties of liquid In-Sn alloys indicate a weak interactions between unlike atoms. The new In, Sn and In-Sn surface tension experimental data set obtained by the large-drop method over the temperature range 523-923 K together with the literature data on different thermophysical properties substantiate a nearly ideal mixing behaviour of these alloys. A low interaction energies do not effect the composition dependence of thermophysical properties, in particular the surface tension and the surface segregation. In order to estimate the effects of the short-range order phenomenon on the surface properties of In-Sn liquids, the QCA (quasi chemical approximation) for the regular solution model and the CFM (compound formation model) have been applied. In the same framework the transport properties and the structural characteristics of liquid In-Sn alloys have also been analysed.

Here we describe the synthesis of polyfluoro-acridines functionalised with perfluoro-alkyl and perfluoro-alkoxy chains, obtained by Ullmann coupling reaction or aromatic nucleophilic substitution. Surface wettability of PMMA is changed by doping with tetrafluoro-perfluorodecyl-acridine, as shown by AFM and contact angle measurements.

Nichrome coatings have been deposited using the d.c. sputtering of the target (80% Ni-20% Cr wt.) by Ar+ ions at a working pressure of 10(-1) Pa and at room temperature. After the air exposure of samples at room temperature, their phase composition and structure was studied by X-ray diffraction, while the surface elemental composition was determined by low energy ion scattering (LEIS) and Auger electron spectroscopy (AES). AES has been also used for the bulk composition analysis. There is a significant difference between the compositions of the surface and of the bulk. Surface segregation of chromium was observed using both LEIS and AES, and it was found that the chromium concentration increases with that of oxygen adsorbed at the surface during the air exposure. The nichrome surface composition is qualitatively the same as in the case of its exposure to O-2 at room temperature, but significantly different from that of the thermally annealed nichrome to 400 degrees C in air. (c) 2006 Elsevier B.V. All rights reserved. 22nd International Conference on Atomic Collisions in Solids, Jul 21-26, 2006, Tech Univ Berlin, Berlin, Germany

International audience; In order to determine the energetic driving forces for surface segregation in bimetallic clusters, we use a combined approach coupling numerical simulations within an N-body interatomic potential and a lattice-gas model. This approach, which has been used successfully to study both the superficial segregation in semi-infinite alloys and the intergranular segregation, allows us to determine the relative contributions of the three elementary driving forces for the different sites of the cluster surface (vertices, edges and facets) in both dilute limits for the Cu-Ag system. We show that the segregation hierarchy based on broken-bond argument (preferential segregation to the vertex sites, less to edge sites, and least to facet sites) is not at all universal. In particular, unusual hierarchies are predicted when the sizes of the constituents are strongly different. Furthermore, we compare the segregation driving forces for cubo-octahedral and icosahedral clusters. They are similar for the vertex sites and edge sites, whereas they differ significantly for the sites of the triangular facets. The segregation of the species with the largest atomic radius (Ag) is indeed largely enhanced in the icosahedral structure due to dilations of the orthoradial distances.

The changes in the surface composition of a Pt(50)Rh(50)(100) alloy due to an ongoing 2H(2) + O(2)--2H(2)O chemical reaction have been studied in situ. Exploiting the high-energy resolution and surface sensitivity of synchrotron radiation core-level spectroscopy it was possible to monitor the population of the two transitions metals atoms at the gas-surface interface. Sequences of fast high-resolution core-level spectra of the Rh3d(5/2), Pt4f(7/2), and O1s core levels showed a continuous exchange of atoms between the first and subsurface layers. An unexpected Pt surface enrichement was found under slightly oxidizing conditions, opposite to what found in a highly oxidizing atmosphere.

The adsorption of oxygen and potassium on the two-phase system: carbide-modified stepped-W(100) surface (CMT) in contact with the solid solution of carbon in bulk tungsten, was investigated by AES and WF measurements. The CMT surface shows metallic behavior judging from its interaction with K. The expected dissociative adsorption of oxygen appears to occur with 1-theta kinetics, possibly via a molecularly chemisorbed state. The "dispersed phase two-phase" model is clearly applicable when oxygen adsorbs on the K-pre-covered carbide. The initial sticking coefficient of oxygen increases drastically from the dispersed to the condensed phase, at least four-fold with respect to so on the clean carbide. It is proposed that this two-phase carbon system can be advantageous compared with the bulk carbide since it can easily regenerate the surface if the latter is depleted from carbon. Surface Review and Letters

The Si/Ge/Si(0 0 1) multilayer with about 1 ML Ge layer is fabricated by evaporating Si overlayer on a Ge/Si(0 0 1) surface at 20–300 °C. The depth profile of the Ge atoms is observed by high-resolution Rutherford backscattering spectroscopy to investigate the possibility of Ge delta doping in Si. The observed profile of the Ge atoms spreads over several atomic layers even at 20 °C and a significant amount of Ge is located in the surface layer at higher temperatures. The results at 20–150 °C are well explained with two-layer model for surface segregation of the Ge atoms and the segregation rates are estimated. The activation energy for surface segregation of Ge atoms in amorphous Si is evaluated to be 0.035 eV, which is much smaller than the value reported for Si deposition at 500 °C. The small activation energy suggests that local heating during the Si deposition is dominant at low temperature.

LaAlO$_{3}$ and NdGaO$_{3}$ thin films of different thickness have been grown by pulsed laser deposition on TiO$_2$-terminated SrTiO$_{3}$ single crystals and investigated by soft X-ray photoemission spectroscopy. The surface sensitivity of the measurements has been tuned by varying photon energy $h\nu$ and emission angle $\Theta$. In contrast to the core levels of the other elements, the Sr $3d$ line shows an unexpected splitting for higher surface sensitivity, signaling the presence of a second strontium component. From our quantitative analysis we conclude that during the growth process Sr atoms diffuse away from the substrate and segregate at the surface of the heterostructure, possibly forming strontium oxide.

Magnesium surface segregation and oxidation were investigated in Al–Mg alloys with a surface texture characterized by branched and dendritic disordered features of low Mg concentration having a lateral 2-D fractal dimension D B ≈1.77. Phase separation of areas with high (∼38% at.) and low (∼14% at.) Mg content allows direct observation of distinct differences in Mg surface segregation and oxidation across disordered phase boundaries. Nanometer scale lateral observation of these phenomena is feasible due to the nanometer spot size (∼15–20 nm) of the electron beam. Preferential surface oxidation, which is manifest even up to temperatures close to the melting point of Al and Mg, is shown to be strongly correlated laterally with the Mg content.

Thermally detected optical absorption measurements have been performed at liquid helium temperature in order to study the effects of In segregation on the optical properties of InxGa1-xAs/GaAs quantum wells grown by molecular-beam epitaxy under various growth conditions. The experimental data are analysed using a kinetic model explicitly including the growth parameters. The variation of the In surface segregation with substrate temperature and growth rate is investigated. This work demonstrates that a way to limit segregation is to prevent the system from reaching thermodynamic equilibrium by choosing low growth temperatures or high growth rates. It is shown, however, that growth temperature is the most efficient parameter to kinetically limit the exchange process. (C) 1997 Elsevier Science S.A.

6 páginas, 5 figuras., The presence of an Au surfactant overlayer allows the growth of high-quality Fe thin layers on Au(100) at 420 K to a depth of at least 70 Å. The surfactant layer can be removed from the surface by gentle ion sputtering. After this removal, Au is still found within the Fe film, as judged by a 0.3 eV shift to lower binding energies of the Au 4f photoemission peak. Quantification of the XPS signal indicates that the total atomic concentration of Au diluted within the Fe layer is 3%, i.e. much higher than the bulk solubility at 420 K. We suggest that relaxation of the strain causes the enhanced solubility of Au in the Fe layer., This work has been financed by the DGICyT through projects PB94-1527 and PB92-0167. One of us (J.E.O) thanks the Basque Government for financial support.

The highly hydrophobic nature of the PVDF membrane makes it prone to fouling. One approach to mitigate fouling is to alter membrane via surface modification. Under optimum conditions of membrane fabrication, in-situ membrane surface modification may achieve as a result of the spontaneous migration of hydrophilic/low surface energy component to the membrane upper surface; so-called surface segregation. Non-polar low surface energy polymers, such as polysiloxane, could render the surface with permanent fouling release ability. However, they cannot spontaneously segregate onto the polymer-water interface during phase separation due to the unfavorable solution thermodynamics. While some hydrophilic polymers such as polyethylene glycol (PEG) may improve the surface hydrophilicity and inhibit the adsorption and deposition of foulant onto surface, their low compatibility with the membrane matrix and consequent depletion during filtration process is considered as drawback. In this study, commercial SiO2 nanoparticles were chemically functionalized by silane coupling agent, which were then specifically designed either to form non-polar hydrophobic PDMS chains or PEG molecules on their surface. Modified nanoparticles were directly dispersed in casting solution and modified SiO2/PVDF blend membranes were prepared. These membranes were characterized with a wide range of techniques. Membrane performance was assessed by static protein adsorption and filtration experiments using BSA as a model foulant. Some of the highlights are as follows: Surface functionalized SiO2 nanoparticles SiO2-COOH significantly improved the dispersion of particle in membrane matrix and the membrane with 2 wt.% nanoparticle loading showed more than 30% increase in flux recovery compared with control membrane and 20% improvement than membrane prepared with 2 wt.% unmodified SiO2; With addition of only 0.5 wt.% surface modified SiO2 nanoparticles SiO2-COOH-PEG into the membrane solution, the resulting PVDF blend membrane showed 27% improvement in flux recovery after physical cleaning compared with the PVDF/unmodified SiO2 membrane. The conclusion is that the modified SiO2 nanoparticles acted as a carrier facilitated the migration of PDMS or PEG molecules that were encapsulated on SiO2 to the surface of the membrane, thus contribution to the change of surface composition of the membrane and therefore enhance the membrane fouling resistance property.

Surface tension measurements are a central task in the study of surfaces and interfaces. For liquid metals, they are complicated by the high temperatures and the consequently high reactivity characterising these melts. In particular, oxidation of the liquid surface in combination with evaporation phenomena requires a stringent control of the experimental conditions, and an appropriate theoretical treatment. Recently, much progress has been made on both sides. In addition to improving the conventional sessile drop technique, new containerless methods have been developed for surface tension measurements. This paper reviews the experimental progress made in the last few years, and the theoretical framework required for modelling and understanding the relevant physico-chemical surface phenomena.

We present a comprehensive study of the structural and electronic properties of ultrathin films containing graphene layers synthesized by chemical vapor deposition (CVD) based surface segregation on polycrystalline Ni foils then transferred onto insulating SiO2/Si substrates. Films of size up to several mm's have been synthesized. Structural characterizations by atomic force microscopy (AFM), scanning tunneling microscopy (STM), cross-sectional transmission electron microscopy (XTEM) and Raman spectroscopy confirm that such large scale graphitic thin films (GTF) contain both thick graphite regions and thin regions of few layer graphene. The films also contain many wrinkles, with sharply-bent tips and dislocations revealed by XTEM, yielding insights on the growth and buckling processes of the GTF. Measurements on mm-scale back-gated transistor devices fabricated from the transferred GTF show ambipolar field effect with resistance modulation ~50% and carrier mobilities reaching ~2000 cm^2/Vs. We also demonstrate quantum transport of carriers with phase coherence length over 0.2 $\mu$m from the observation of 2D weak localization in low temperature magneto-transport measurements. Our results show that despite the non-uniformity and surface roughness, such large-scale, flexible thin films can have electronic properties promising for device applications., Comment: This version (as published) contains additional data, such as cross sectional TEM images

GaN/AlN multiple quantum wells (MQWs), designed for intersubband (ISB) absorption in the telecommunication range, are grown by molecular beam epitaxy. We demonstrate that the use of both AlN template and optimized growth temperature allows to reach ISB transition energy in the telecom range, i.e. above 0.8 eV (lambda = 1.55 mu m). Absorption spectra exhibit narrow linewidth (< 50 meV) with a relative energy broadening of 8%. An electro-optical modulator based on electron tunnelling in coupled QWs is then fabricated. A modulation bandwidth of 2 GHz at -3 dB cut off frequency is achieved for 15x15 mu m(2) mesas. We show that the modulation rate is limited by the device geometry rather than by the material quality, which makes this technology a good candidate for THz regime.

A smectic polystyrene–poly(perfluorooctylethyl acrylate) block copolymer was synthesized by atom transfer radical polymerization and blended with a thermoplastic elastomer SEBS in different compositions. The mesophase structure and transition temperatures were investigated by DSC and WAXD. Thin films of the block copolymer and the blends exhibited large contact angles with both water and n-hexadecane, which resulted in low solid surface tensions. XPS findings at different photoemission angles confirmed the effective surface segregation of the mesogenic chains of the fluorinated polymer block.

Coupling electron microscopy techniques with insitu heating ability allows us to study phase transformations on the single-nanoparticle level. We exploit this setup to study disorder-to-order transformation of Pt-Fe alloy nanoparticles, a material that is of great interest to fuel-cell electrocatalysis and ultrahigh density information storage. In contrast to earlier reports, we show that Fe (instead of Pt) segregates towards the particle surface during annealing and forms a Fe-rich FeOx outer shell over the alloy core. By combining both exsitu and insitu approaches to probe the interplay between ordering and surface-segregation phenomena, we illustrate that the surface segregation of Fe precedes the ordering process and affects the ordered phase evolution dramatically. We show that the ordering initiates preferably at the pre-existent Fe-rich shell than the particle core. While the material-specific findings from this study open interesting perspectives towards a controlled phase evolution of Pt-Fe nanoalloys, the characterization methodologies described are general and should prove useful to probing a wide-range of nanomaterials. Surface-segregation vs atomic-ordering: By using atomic-resolution imaging and electron energy loss spectroscopy and employing both exsitu and insitu approaches, an ongoing interplay between segregation and ordering during the thermal annealing of Pt - Fe alloy nanoparticles is studied. Findings reveal a surface segregation of Fe that is in contrast to earlier reports suggesting Pt surface segregation.

Surface segregation is the key to understanding the surface tension γ of alloys. The basic phenomena can be demonstrated qualitatively by using the ideal solution model. For a binary system, this model is first used to explain the temperature dependence of the surface tension. A simple criterion is established for sign reversal of the temperature coefficient. The ideal solution model is then extended to include the effect of compound formation. A simple explicit equation is proposed which fits existing data surprisingly well.

The present work represents an experimentally based investigation of the applicability of a statistical mechanical theory in conjunction with a compound formation model (CFM) to describe surface properties of Pb-Bi liquid alloys. The surface tension of molten Pb, Bi and Pb-Bi alloys has been measured by the sessile-drop method over the range of temperatures. The results obtained show general agreement with other reported measurements on pure elements and their alloys as well as with calculated surface tension values. Based on the phase diagram evidence about the existence of the ƒÕ-Pb3Bi intermetallic compound, the phenomenon of compound formation in Pb-Bi liquid alloys has been analysed through the study of surface properties (surface tension and surface composition) and microscopic functions (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) in the frame of compound formation model (CFM).

The self-assembly blends of cellulose propionate (CP) and fluorine (F)-containing cellulose derivatives was examined on a model system of solvent cast films. The F-containing derivatives were either high molecular weight statistical cellulose esters with a number of F-containing substituent evenly distributed along the backbone (F-esters), or F-terminated CP-segments with exactly one F-containing endgroup. The F-esters were synthesized in a homogeneous phase and identified by 19F-NMR. Thermal analysis showed improved thermal stability of the F-esters when compared to F-free derivatives. 1-monohydroxy functionalized CP-segments were synthesized by HBr depolymerization using either a commercially available CP with residual OH-groups or a perpropionylated CP (CTP). The hydrolysis using the commercial CP yielded only segments of a minimum DP of 50 and the Mark-Houwink constant declined from 1 to 0.6. The results indicate that in the presence of free hydroxyls branches are formed by transglycosidation. The hydrolysis from perpropionylated CP resulted in segments with a minimum DP of 7, which is in accordance to previous studies. F-terminated CP segments were synthesized by coupling of the appropriate F-containing alcohol to the CP segment via toluene diisocyanate. Solutions containing F-terminated CP-segments showed typical critical micelle behavior. The critical micelle concentration depended on the molecular weight of the CP segment and the type of F-containing endgroup. The micelles are thought to consist of a core of the F-endgroups and a corona made-up of CP. Films containing the oligomers cast from micellar solution revealed a linear decrease in wetting force according to the blend composition of the oligomer, i.e. behavior according to the rule of mixing. This indicated the absence of surface segregation of the F-endgroup and it is explained with the fact that the micellar structure is retained in the solid state, suppressing surface segregation. The solid state micelles were visualized as dome-like protrusions by height image atomic force microscopy. In systems blended with CP the distance between the protrusions was found to increase with increasing CP content which was explained by a dilution process. Films containing F-esters were characterized by wetting force measurements and x-ray photoelectron spectroscopy (XPS). The wetting force decreased dramatically at low blend content of the F-ester and at the same time an F surface-concentration higher then expected from the blend composition was found by XPS. This indicated self-assembly by surface segregation of the F-containing species during film formation. The extent of surface segregation was found to depend on the type of the F-ester group as well as on the blend concentration of the F-ester. Dynamic wetting force measurements revealed hysteresis in films containing either F-esters or F-terminated CP segments. The hysteresis was found to be both kinetic (water sorption and reorganization) and thermodynamic (surface roughness and surface coverage with F-moieties) in nature. Consecutive force loops revealed an increase in the wetting force (advancing and receding) with increasing loop number, indicating the increased hydrophobicity of the surface. The force increase was determined to be due to water sorption as well as due to surface reorganization. An increase in the size of the F-groups signified a decrease in reorganization rate due to a decreased mobility of the group. The process of reorganization was fully reversible, a behavior which is congruent with the definition of smart behavior. Ph. D.

The interaction of O with UHV cleaved TaSe2 and WSe2, previously intercalated in situ with Na, was studied by synchrotron radiation in the region 30 80 eV. The observed strong fluctuations of the Na 2p emissions relative to the metal 4f ones are explained in terms of deintercalation of Na, in the tendency to form NaxOy surface oxides, along with clustering as oxides are forming. The deintercalation is proposed to occur in two stages: a fast one attributed to the lowering of the near surface potential due to the O?Na interaction and a slow one due to volume diffusion. Surface Science

The energetics of mixing and structural arrangement in liquid Al-Cr and Cr-Ni alloys has been analysed through the study of surface properties (surface tension and surface segregation), dynamic properties (chemical diffusion) and microscopic functions (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) in the framework of statistical mechanical theory in conjunction with quasi-lattice theory. The Al-Cr phase diagram exhibits the existence of different intermetallic compounds in the solid state, while that of Cr-Ni is a simple eutectic-type phase diagram at high temperatures and includes the low-temperature peritectoid reaction in the range near a CrNi(2) composition. Accordingly, the mixing behaviour in Al-Cr and Cr-Ni alloy melts was studied using the complex formation model in the weak interaction approximation and by postulating Al(8)Cr(5) and CrNi(2) chemical complexes, respectively, as energetically favoured.

F. J. Palomares and C. Munuera Instituto de Ciencia de Materiales de Madrid (CSIC), Cantoblanco, 28049 Madrid, Spain C. Martínez Boubeta and A. Cebollada Instituto de Microelectrónica de Madrid IMM (CNM-CSIC), Isaac Newton 8, P.T.M. 28760 Madrid, Spain The chemical nature of the different interfaces and possible segregation effects are studied in fully epitaxial Fe/MgO/Fe (001) oriented heterostructures fabricated by combined sputtering plus laser ablation deposition techniques. Auger electron spectroscopy depth profiling experiments showed that the interfaces of the MgO spacer with the Fe layers are different, the inner MgO/Fe being spatially broader and with an FeO interlayer, while that of the outer Fe/MgO is spatially narrower with no evidence of FeO formation. This spatial and chemical asymmetry is interpreted in terms of the different deposition procedures, which affect the formation of both interfaces. No Fe segregation in the MgO layers or MgO segregation in the Fe films is observed., This work was supported by the Spanish MCyT.

Stacked layers of self-assembled In(Ga)As quantum rings on GaAs grown by solid source molecular beam epitaxy are studied by ex situ atomic force microscopy (AFM), low temperature photoluminescence (PL) and cross-sectional transmission electron microscopy (XTEM). The influence of the strain field and InAs segregation on the surface morphology, optical properties and vertical ordering of three quantum ring layers is analyzed for GaAs spacers between layers from 1.5 to 14 nm. AFM and PL results show that samples with spacers >6 nm have surface morphology and optical properties similar to single layers samples. XTEM results on samples with 3 and 6 nm GaAs spacers show that the rings are preserved after capping with GaAs, and evidence the existence of vertically ordered quantum rings., This work was supported by Spanish MCyT under NANOSELF project sTIC2002-04096d, by NANOMAT project of the EC Growth Program sContract No. G5RD-CT-2001-00545d and by the SANDiE Network of excellence sContract No. NMP4-CT-2004-500101d. The authors also thank the Junta de Andalucía sPAI research group TEP- 0120d. TEM measurements were carried out in the DMESCCYT. The authors acknowledge P. Offermans and P. Koenraad for fruitful discussions.

X-ray photoelectron spectroscopy and Auger electron spectroscopy analyses of an Sn-5at.%Sb mixed oxide catalyst showed that activation leads to an increase in concentration of antimony on its surface. This surface segregation is induced by the presence of oxygen in the gas phase. The active catalyst probably contains both antimony(V) and antimony(III) in addition to antimony(V) in solid solution with SnO 2 .