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Jacob N. Israelachvili - One of the best experts on this subject based on the ideXlab platform.
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real time monitoring of aluminum crevice corrosion and its inhibition by vanadates with multiple beam interferometry in a surface forces apparatus
Journal of The Electrochemical Society, 2015Co-Authors: Buddha Ratna Shrestha, Jacob N. Israelachvili, Qingyun Hu, Theodoros Baimpos, Kai Kristiansen, Markus ValtinerAbstract:Author(s): Shrestha, BR; Hu, Q; Baimpos, T; Kristiansen, K; Israelachvili, JN; Valtiner, M | Abstract: © The Author(s) 2015. Crevice corrosion (CC) of metals remains a serious concern for structural materials. Yet a real-time in situ visualization of corrosion, and its inhibition within a confined geometry, remains challenging. Here, we present how multiple-beam interferometry in a Surface Forces Apparatus can be utilized to directly visualize corrosion processes in real-time and with Angstrom resolution within welldefined confinement geometries. We use atomically smooth muscovite mica surfaces to form round-shaped ∼1000 μm2 crevices on aluminum. After exposure to NaCl solutions we can detect and track active sites of aluminum corrosion within this confined geometry. CC of aluminum randomly initiates in the confined crevice mouth, where the distance between apposing surfaces is between 20-300 nm. We can directly track oxide dissolution/formation, and corrosion-rates as well as their retardation due to sodium vanadate inhibitors present in solution. Formation of a compacted oxide layer effectively inhibits CC in 5 mM NaCl solutions with 2.5 mM of added NaVO3, while inhibition rapidly breaks down at chloride concentrations above 50 mM. Breakdown of the inhibition-layers is initiated by rapid dissolution of the protective oxide within the confined zone. Our technique may be adapted for monitoring CC, corrosion inside of crack-tips, and evaluation of inhibitor efficiencies in a variety of metals.
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adhesion and surface interactions of a self healing polymer with multiple hydrogen bonding groups
Advanced Functional Materials, 2014Co-Authors: Ali Faghihnejad, Kathleen E. Feldman, Matthew V. Tirrell, Jacob N. Israelachvili, Edward J Kramer, Jing Yu, Craig J Hawker, Hongbo ZengAbstract:Author(s): Faghihnejad, A; Feldman, KE; Yu, J; Tirrell, MV; Israelachvili, JN; Hawker, CJ; Kramer, EJ; Zeng, H | Abstract: The surface properties and self-adhesion mechanism of self-healing poly(butyl acrylate) (PBA) copolymers containing comonomers with 2-ureido-4[1H]-pyrimidinone quadruple hydrogen bonding groups (UPy) are investigated using a surface forces apparatus (SFA) coupled with a top-view optical microscope. The surface energies of PBA-UPy4.0 and PBA-UPy7.2 (with mole percentages of UPy 4.0% and 7.2%, respectively) are estimated to be 45-56 mJ m-2 under dry condition by contact angle measurements using a three probe liquid method and also by contact and adhesion mechanics tests, as compared to the reported literature value of 31-34 mJ m-2 for PBA, an increase that is attributed to the strong UPy-UPy H-bonding interactions. The adhesion strengths of PBA-UPy polymers depend on the UPy content, contact time, temperature and humidity level. Fractured PBA-UPy films can fully recover their self-adhesion strength to 40, 81, and 100% in 10 s, 3 h, and 50 h, respectively, under almost zero external load. The fracture patterns (i.e., viscous fingers and highly "self-organized" parallel stripe patterns) have implications for fabricating patterned surfaces in materials science and nanotechnology. These results provide new insights into the fundamental understanding of adhesive mechanisms of multiple hydrogen-bonding polymers and development of novel self-healing and stimuli-responsive materials. © 2014 WILEY-VCH Verlag GmbH a Co. KGaA, Weinheim.
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Importance of Pico-Scale Topography of Surfaces for Adhesion, Friction, and Failure
MRS Bulletin, 2005Co-Authors: Jacob N. IsraelachviliAbstract:This article is an edited transcript based on the MRS Medal Award presentation given by Jacob N. Israelachvili on December 1, 2004. at the Materials Research Society Fall Meeting in Boston. An expanded article on this topic will be published in the August 2005 issue of the Journal of Materials Research. Recent experimental results have shown how surface texture, surface energy, and the bulk properties of materials can affect their adhesion and friction and, in turn, determine some of the fundamental differences between modes of failure of materials. Theoretical modeling and computer simulations. among other methods. provide examples and comparisons of surfaces that are rough or smooth, hard or soft (for example, viscoelastic), adhesive or non-adhesive, and dry (unlubricated) or lubricated. Such studies clarify the molecular and atomic basis of many well-established adhesion and tribological laws and empirical observations, revealing insights and relationships between nanoscale (molecular) and macroscale processes. Also of critical importance are the effects that occur at the sub-nanoscale, that is, in the sub-angstrom or picoscale regime. It is demonstrated and argued that the ultrafine picoscale details of a surface lattice, or its roughness. can be the most important factor in determining its friction (and mode II fracture), whereas such effects are quantitatively less important for adhesion and mode I fracture processes.
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Putting Liquids Under Molecular-Scale Confinement
Science (New York N.Y.), 2001Co-Authors: Jacob N. Israelachvili, Delphine GourdonAbstract:When a liquid is confined, for example, between two surfaces, its properties change as the confined region approaches molecular dimensions. Such confinement-induced changes play an important role in diverse areas from geology to biology. In their Perspective, [Israelachvili and Gourdon][1] highlight the report by [ Heuberger et al .][2], who have devised an extended surface forces apparatus (eSFA) that allows highly accurate measurements of the forces and densities of confined liquids. [1]: http://www.sciencemag.org/cgi/content/full/292/5518/867 [2]: http://www.sciencemag.org/cgi/content/short/292/5518/905
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Polymer-Cushioned Bilayers. I. A Structural Study of Various Preparation Methods Using Neutron Reflectometry
Biophysical journal, 1999Co-Authors: Joyce Y. Wong, Jacob N. Israelachvili, Jaroslaw Majewski, Markus Seitz, Chad K. Park, G. S. SmithAbstract:This neutron reflectometry study evaluates the structures resulting from different methods of preparing polymer-cushioned lipid bilayers. Four different techniques to deposit a dimyristoylphosphatidylcholine (DMPC) bilayer onto a polyethylenimine (PEI)-coated quartz substrate were examined: 1) vesicle adsorption onto a previously dried polymer layer; 2) vesicle adsorption onto a bare substrate, followed by polymer adsorption; and 3, 4) Langmuir-Blodgett vertical deposition of a lipid monolayer spread over a polymer-containing subphase to form a polymer-supported lipid monolayer, followed by formation of the outer lipid monolayer by either 3) horizontal deposition of the lipid monolayer or 4) vesicle adsorption. We show that the initial conditions of the polymer layer are a critical factor for the successful formation of our desired structure, i.e., a continuous bilayer atop a hydrated PEI layer. Our desired structure was found for all methods investigated except the horizontal deposition. The interaction forces between these polymer-supported bilayers are investigated in a separate paper (Wong, J. Y., C. K. Park, M. Seitz, and J. Israelachvili. 1999. Biophys. J. 77:1458-1468), which indicate that the presence of the polymer cushion significantly alters the interaction potential. These polymer-supported bilayers could serve as model systems for the study of transmembrane proteins under conditions more closely mimicking real cellular membrane environments.
Regine Von Klitzing - One of the best experts on this subject based on the ideXlab platform.
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Experimental evaluation of additional short ranged repulsion in structural oscillation forces
Soft matter, 2018Co-Authors: Sebastian Schön, Regine Von KlitzingAbstract:The paper addresses additional short ranged repulsion in structural oscillation forces between silica surfaces across a suspension of silica nanoparticles. Fit and prediction of the structural oscillation forces usually involve an exponentially decreasing harmonic as introduced by Israelachvili [Israelachvili, Intermolecular & surface forces, Academic Press, San Diego, USA, 1985]. Recently we demonstrated, for aqueous suspensions of silica nanoparticles at various concentrations, that this fit equation is insufficient to describe the structural oscillation forces in its whole range [Schon et al., Beilstein J. Nanotechnol., 2018, 9, 1095–1107]. An additional force acting on short separations leads to the fit parameters scattering widely as well as being dependent on each other and the starting point of the fit. An additional repulsive term was introduced to solve these problems. The additional repulsive force has also been observed by others, in ionic liquids and polyelectrolyte solutions at high ionic strength. It was attributed to the diffusive double layer forces. The rise of the additional repulsion with increasing particle concentration seems to conflict with this interpretation. In this work, colloidal probe atomic force microscopy is used in aqueous suspensions of silica nanoparticles to investigate other contributing factors such as the increasing hydrodynamic drag in the normal direction to the confining surface with increasing particle concentration. A kinetic component to the structural oscillation forces is observed. Furthermore, sodium chloride is used to adjust the ionic strength of two different concentrated silica nanoparticle suspensions. For these systems the additional decay length is compared to the Debye length in the range from low to high ionic strength. A master curve of the additional decay length over Debye length at different ionic strengths, approach speed and particle concentration is produced. It affirms the link between the two and the connection between the additional force and the diffusive double layer forces. The increasing trend for the additional repulsion with increasing particle concentration reveals a synergistic effect of diffusive double layer forces and structural oscillation forces at low to medium ionic strength, which cannot be observed at high ionic strength.
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A simple extension of the commonly used fitting equation for oscillatory structural forces in case of silica nanoparticle suspensions.
Beilstein journal of nanotechnology, 2018Co-Authors: Sebastian Schön, Regine Von KlitzingAbstract:Background: The ordering of molecules or particles in the vicinity of a confining surface leads to the formation of an interfacial region with layers of decreasing order normal to the confining surfaces. The overlap of two interfacial regions gives rise to the well-known phenomenon of oscillatory structural forces. These forces are commonly fitted with an exponentially decaying harmonic oscillation as introduced by Israelachvili (Israelachvili, J. N. Intermolecular & surface forces; Academic Press: San Diego, CA, USA, 1985). From the fit three important parameters are obtained, namely wavelength, amplitude and decay length, which are related to the period, the strength and the correlation length of the oscillatory structural forces, respectively. The paper addresses structural forces between a silica microsphere and a silicon wafer across silica nanoparticle suspensions measured with a colloidal probe AFM. Using the simple fitting procedure with three parameters often leads to underestimation of actually measured forces. The deviation of the fit from the experimental data is especially pronounced at small distances of the confining surfaces and at high concentrations of silica nanoparticles. As a consequence, the parameters of the common fit equation vary with the starting point of the fit. Although the wavelength is least affected and seems to be quite robust against the starting point of the fit, all three parameters show distinct oscillations, with a period similar to the wavelength of the oscillatory structural forces themselves. The oscillations of amplitude and decay length, which are of much higher magnitude, show a phase shift of 180° implying not only a dependence on the starting point of the fit but also on each other. The range affected by this systematic deviation of the fit parameters is much larger than the optically perceived mismatch between fit and experimental data, giving a false impression of robustness of the fit. Results: By introducing an additional term of exponentially decaying nature the data can be fitted accurately down to very small separations and even for high silica nanoparticle concentrations (10 wt %). Furthermore wavelength, amplitude and decay length become independent of the starting point of the fit and in case of the latter two of each other. The larger forces at small separations indicate a more pronounced ordering behavior of the particles in the final two layers before the wall. This behavior is described by the proposed extension of the common fit equation. Conclusion: Thus, the extension increases the accessible data range in terms of separation and concentration and strongly increases the accuracy for all fitting parameters in the system studied here.
Nick Zagorski - One of the best experts on this subject based on the ideXlab platform.
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Profile of Jacob N. Israelachvili
Proceedings of the National Academy of Sciences of the United States of America, 2006Co-Authors: Nick ZagorskiAbstract:Someday, roles may change, and Israelachvili may himself be the topic of a future science history aficionado. After a distinguished research career in Europe and Australia, Israelachvili has been a professor of chemical engineering at the University of California, Santa Barbara (Santa Barbara, CA) for the past 20 years, studying the various interactions between molecules and surfaces, principally in a liquid environment. His work in determining the theoretical basis and dynamics of forces that contribute to friction, fluidity, adhesion, and repulsion has wide-ranging applications in areas including medicine, geology, and food science. Israelachvili has designed or improved several instruments that enable direct force measurements as well as authored the definitive textbook on this field, Intermolecular and Surface Forces, in 1985 (1). In 2004, he was elected to both the American Physical Society and the National Academy of Sciences for his research contributions.
Jan Kevelam - One of the best experts on this subject based on the ideXlab platform.
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Formation and stability of micelles and vesicles
Current Opinion in Colloid and Interface Science, 1996Co-Authors: Jan B. F. N. Engberts, Jan KevelamAbstract:Recent studies on the self-assembly of novel catanionic, bolaform and gemini surfactants provide evidence that the Israelachvili packing parameter approach can often be successfully used to predict the morphology of surfactant aggregates on the basis of the geometrical properties of the surfactant molecules. Furthermore, combined theoretical and experimental efforts have provided a consistent picture of the requirements for spontaneous vesicle formation which, in addition to a favorable packing parameter of the individual surfactant molecules, calls for a nonideal mixing of the bilayer components in order to provide the bilayer with a nonzero spontaneous curvature.
Sebastian Schön - One of the best experts on this subject based on the ideXlab platform.
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Experimental evaluation of additional short ranged repulsion in structural oscillation forces
Soft matter, 2018Co-Authors: Sebastian Schön, Regine Von KlitzingAbstract:The paper addresses additional short ranged repulsion in structural oscillation forces between silica surfaces across a suspension of silica nanoparticles. Fit and prediction of the structural oscillation forces usually involve an exponentially decreasing harmonic as introduced by Israelachvili [Israelachvili, Intermolecular & surface forces, Academic Press, San Diego, USA, 1985]. Recently we demonstrated, for aqueous suspensions of silica nanoparticles at various concentrations, that this fit equation is insufficient to describe the structural oscillation forces in its whole range [Schon et al., Beilstein J. Nanotechnol., 2018, 9, 1095–1107]. An additional force acting on short separations leads to the fit parameters scattering widely as well as being dependent on each other and the starting point of the fit. An additional repulsive term was introduced to solve these problems. The additional repulsive force has also been observed by others, in ionic liquids and polyelectrolyte solutions at high ionic strength. It was attributed to the diffusive double layer forces. The rise of the additional repulsion with increasing particle concentration seems to conflict with this interpretation. In this work, colloidal probe atomic force microscopy is used in aqueous suspensions of silica nanoparticles to investigate other contributing factors such as the increasing hydrodynamic drag in the normal direction to the confining surface with increasing particle concentration. A kinetic component to the structural oscillation forces is observed. Furthermore, sodium chloride is used to adjust the ionic strength of two different concentrated silica nanoparticle suspensions. For these systems the additional decay length is compared to the Debye length in the range from low to high ionic strength. A master curve of the additional decay length over Debye length at different ionic strengths, approach speed and particle concentration is produced. It affirms the link between the two and the connection between the additional force and the diffusive double layer forces. The increasing trend for the additional repulsion with increasing particle concentration reveals a synergistic effect of diffusive double layer forces and structural oscillation forces at low to medium ionic strength, which cannot be observed at high ionic strength.
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A simple extension of the commonly used fitting equation for oscillatory structural forces in case of silica nanoparticle suspensions.
Beilstein journal of nanotechnology, 2018Co-Authors: Sebastian Schön, Regine Von KlitzingAbstract:Background: The ordering of molecules or particles in the vicinity of a confining surface leads to the formation of an interfacial region with layers of decreasing order normal to the confining surfaces. The overlap of two interfacial regions gives rise to the well-known phenomenon of oscillatory structural forces. These forces are commonly fitted with an exponentially decaying harmonic oscillation as introduced by Israelachvili (Israelachvili, J. N. Intermolecular & surface forces; Academic Press: San Diego, CA, USA, 1985). From the fit three important parameters are obtained, namely wavelength, amplitude and decay length, which are related to the period, the strength and the correlation length of the oscillatory structural forces, respectively. The paper addresses structural forces between a silica microsphere and a silicon wafer across silica nanoparticle suspensions measured with a colloidal probe AFM. Using the simple fitting procedure with three parameters often leads to underestimation of actually measured forces. The deviation of the fit from the experimental data is especially pronounced at small distances of the confining surfaces and at high concentrations of silica nanoparticles. As a consequence, the parameters of the common fit equation vary with the starting point of the fit. Although the wavelength is least affected and seems to be quite robust against the starting point of the fit, all three parameters show distinct oscillations, with a period similar to the wavelength of the oscillatory structural forces themselves. The oscillations of amplitude and decay length, which are of much higher magnitude, show a phase shift of 180° implying not only a dependence on the starting point of the fit but also on each other. The range affected by this systematic deviation of the fit parameters is much larger than the optically perceived mismatch between fit and experimental data, giving a false impression of robustness of the fit. Results: By introducing an additional term of exponentially decaying nature the data can be fitted accurately down to very small separations and even for high silica nanoparticle concentrations (10 wt %). Furthermore wavelength, amplitude and decay length become independent of the starting point of the fit and in case of the latter two of each other. The larger forces at small separations indicate a more pronounced ordering behavior of the particles in the final two layers before the wall. This behavior is described by the proposed extension of the common fit equation. Conclusion: Thus, the extension increases the accessible data range in terms of separation and concentration and strongly increases the accuracy for all fitting parameters in the system studied here.
