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Vincent Ball - One of the best experts on this subject based on the ideXlab platform.
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phase diagram of sodium hexametaphosphate and poly allylamine hydrochloride mixtures and in situ monitoring of step by step Deposition in this polyelectrolyte system
Macromolecular Chemistry and Physics, 2015Co-Authors: Vincent BallAbstract:The step-by-step Deposition of poly(allylamine hydrochloride) (PAH) and sodium hexametaphosphate (PSP) leads to coatings displaying interesting intumescent properties and is a fascinating model system to understand the fundamental Mechanism behind such a Deposition process. In this investigation, the Deposition kinetics of (PAH-PSP)n is followed in situ by means of a quartz crystal microbalance with dissipation monitoring, as a function of NaCl concentration. The evolution of the film Deposition is analyzed in detail and the data are compared with previous data obtained by ellipsometry on dried films. These results are also compared with the expectations from the PAH/PSP phase diagram. The (PAH-PSP)n films are also able to incorporate hexacyanoferrate anions with an amount of an incorporated redox probe reflecting the film thickness as obtained in the presence of eletrolyte solutions of increasing ionic strength. The in situ measurements and the electrochemical probe experiments reveal details of the film Deposition Mechanism that are not accessible by dry-state characterization methods.
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Kinetics of polydopamine film Deposition as a function of pH and dopamine concentration: Insights in the polydopamine Deposition Mechanism
Journal of Colloid and Interface Science, 2012Co-Authors: Vincent Ball, Doriane Del Frari, Valerie Toniazzo, David RuchAbstract:Abstract The formation of “polydopamine” thin films becomes a popular method to confer multifunctionality to solid–liquid interfaces through the available catechol groups of such films. The Mechanism of film formation is, however, not well elucidated, and most investigators use the protocol developed by Messersmith et al. (H. Lee, S.M. Dellatore, W.M. Miller, P.B. Messersmith, Science 318 (2007) 426.) using a dopamine solution at a constant concentration of 2 g L−1 in the presence of Tris(hydroxymethyl aminomethane) at pH 8.5. A particular finding of this initial study was that the film thickness reaches a constant value (almost substrate independent) of about 40 nm. Herein, we investigate the change in the polydopamine film thickness, morphology, surface energy and electrochemical properties as a function of the concentration of the dopamine solution put in the presence of silicon substrates. As a surprising finding, we observe a constant increase in the maximal film thickness with an increase in the dopamine solution between 0.1 and 5 g L−1. The surface morphology is also markedly affected by the concentration of the dopamine solution, whereas the different components of the surface energy stay unaffected by the dopamine solution concentration. In addition, electrochemical impedance spectroscopy shows that the higher the initial dopamine concentration, the more rapidly compact and impermeable films are formed. Finally, we propose a model for the Deposition of polydopamine films taking all our findings into account. This model relies on a rate equation taking into account both attractive and repulsive interactions between small polydopamine aggregates on the surface and in solution.
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Deposition Mechanism and Properties of Thin Polydopamine Films for High Added Value Applications in Surface Science at the Nanoscale
BioNanoScience, 2012Co-Authors: Vincent Ball, Doriane Del Frari, Markus J. Buehler, Valerie Toniazzo, Manoj K Singh, José Joaquin De Almeida Gracio, Marc Michel, David RuchAbstract:Polydopamine films have been introduced by Messersmith eta!. as a possible "versatile" surface function-alization method allowing to coat the surface of almost all known materials even superhydrophobic surfaces. These new kinds of coatings also confer a plethora of functional-ities to the coated materials owing to the complex chemistry of the catechol quinone moieties present on the surfac e of polydopamine. These coatings may hence become an inter-esting alternative to established surface coatings like self-assembled monolayers and polyelectrolyte multilayered films. In this review, we desc ribe the knowledge acquired in the last 3 years about the Deposition Mechanisms of polydopamine films, their properties, and various applications in surface science at the nanoscale.
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dopamine melanin film Deposition depends on the used oxidant and buffer solution
Langmuir, 2011Co-Authors: Falk Bernsmann, Vincent Ball, Valerie Toniazzo, Marc Michel, Frederic Addiego, Arnaud Ponche, Jose Joaquin De Almeida Gracio, David RuchAbstract:The Deposition of “polydopamine” films, from an aqueous solution containing dopamine or other catecholamines, constitutes a new and versatile way to functionalize solid−liquid interfaces. Indeed such films can be deposited on almost all kinds of materials. Their Deposition kinetics does not depend markedly on the surface chemistry of the substrate, and the films can reach thickness of a few tens of nanometers in a single reaction step. Up to now, even if a lot is known about the oxidation Mechanism of dopamine in solution, only little information is available to describe the Deposition Mechanism on surfaces either by oxidation in solution or by electroDeposition. The Deposition kinetics of melanin was only investigated from dopamine solutions using oxygen or ammonium persulfate as an oxidant and from a tris(hydroxymethyl) aminomethane (Tris) containing buffer solutions at pH 8.5. Many other oxidants could be used, and the buffer agent containing a primary amine group may influence the Deposition process. ...
Daniel Lincot - One of the best experts on this subject based on the ideXlab platform.
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a better understanding of the growth Mechanism of zn s o oh chemical bath deposited buffer layers for high efficiency cu in ga s se 2 solar cells
Physica Status Solidi (a), 2008Co-Authors: C Hubert, N Naghavi, Arnaud Etcheberry, O Roussel, Dimitrios Hariskos, Michael Powalla, O Kerrec, Daniel LincotAbstract:In the field of Cu(Ga,In)(S,Se) 2 photovoltaic technology, zinc sulphide based buffer layers prepared by Chemical Bath Deposition (CBD) have already demonstrated their potential to replace CdS. This paper aims on a better understanding of Deposition Mechanism of the Zn(S,O,OH) buffer layers. First, the influence of Deposition parameters is studied from solution chemistry considerations by constructing solubility diagrams of ZnS, ZnO, and Zn(OH) 2 . Experimental studies are then carried out by the in situ quartz crystal microgravimetry (QCM) technique. A global equation for the growth rate is derived from these experiments. The morphology and composition of Zn(S,O,OH) films are then determined using scanning electron microscopy and X-ray photoelectron spectroscopy techniques. Electro-deposited-CIS/Zn(S,O,OH)/ZnO and co-evaporated-CIGS/Zn(S,O,OH)/ZnO cells were prepared with efficiencies similar to that of reference CBD CdS buffer layers.
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temperature effects on zno electroDeposition
Electrochimica Acta, 2005Co-Authors: A Goux, Thierry Pauporte, J Chivot, Daniel LincotAbstract:Abstract A thermochemical study of the temperature effects on the Zn–Cl–H 2 O system by means of potential–pH, solubility and species repartition diagrams is presented with the view to better understand the effect of temperature on the Deposition Mechanism and composition of zinc oxide thin films. These calculations have been completed by film preparation at different temperatures between room temperature and 90 °C. Below 34 °C, we observe the absence of continuous film growth and surface passivation. The oxide nucleation and film growth start above 34 °C, whereas the optimum film transparency and crystallinity is obtained from 40 °C. Above, the main effect of the temperature is to raise the film texturation with the c -axis perpendicular to the substrate surface.
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mechanistic study of cathodic electroDeposition of zinc oxide and zinc hydroxychloride films from oxygenated aqueous zinc chloride solutions
Journal of The Electrochemical Society, 1998Co-Authors: S Peulon, Daniel LincotAbstract:Films of zinc oxide and related compounds [ZnO, ZnO x (OH) y , Zn(OH) x Cl y ] are electrodeposited cathodically in aqueous zinc chloride solutions using dissolved oxygen as a precursor. The influence of the precursor concentrations, pH, and Deposition temperature on the growth, composition, and properties of the films are investigated by means of in situ techniques : voltammetry, electrochemical quartz-crystal microgravimetry, surface pH, and ex situ techniques: X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy. The Deposition Mechanism is analyzed in terms of electrochemically induced surface precipitation due to an increase of local pH resulting from the oxygen reduction reaction. This approach allows us to explain the formation of either zinc hydroxychloride compounds or zinc oxide from their calculated solubility diagrams. In conditions of the formation of ZnO, a dramatic effect of temperature is observed, with a transition between amorphous insulating zinc oxyhydroxide to well-crystallized and conducting zinc oxide when the temperature increases (T transition 50 °C).
Kazuhiro Ogawa - One of the best experts on this subject based on the ideXlab platform.
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elucidation of cold spray Deposition Mechanism by auger electron spectroscopic evaluation of bonding interface oxide film
Acta Materialia, 2019Co-Authors: Yuji Ichikawa, Kazuhiro Ogawa, Ryotaro Tokoro, Masatoshi TannoAbstract:Abstract The relationship between the cold spray Deposition Mechanism, microstructure, and strength of the resulting film must be understood for this innovative process to be practical. Previous studies have suggested that the coating Mechanism is reliant on breaking the natural oxide film such that metallic bonding occurs through direct contact between the metal surfaces. In this study, the proposed model was experimentally verified by a small tensile adhesion test and auger electron spectroscopy analysis of the bonding interface. Since shear deformation does not occur at the tip (south pole) of the incoming particle, the oxide film is not broken, such that the bonding strength is weak. In contrast, at the outer edge of the particle, metallic bonding occurs, attaining a level of strength that exceeds that of the base material due to the huge plastic deformation. This phenomenon is known as the “south-pole problem,” and can lead to a decrease in the overall adhesion strength despite the local adhesion being strong. However, detailed observations revealed, in parts of the deposits, particles that had adhered across their entire surface. This suggests that, provided the collision state can be controlled, it is possible to overcome the south-pole problem and improve the adhesion strength.
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Understanding Deposition Mechanism in cold sprayed ultra high molecular weight polyethylene coatings on metals by isolated particle Deposition method
Additive Manufacturing, 2018Co-Authors: Kesavan Ravi, Tiana Deplancke, Kazuhiro Ogawa, Jean-yves Cavaille, Olivier LameAbstract:Abstract The cold spray has been shown to be one of the promising additive manufacturing technologies to process Ultra High Molecular Weight Polyethylene (UHMWPE)-metal integrated systems by successfully being able to coat UHMWPE on metals using fumed nano-alumina (FNA) as UHMWPE particle surface modifiers. However, the exact Mechanism of UHMWPE Deposition and role of FNA was widely unknown. This study aims at identifying the fundamental parameters involved in high strain-rate UHMWPE Deposition and their role in successful adhesion by a technique called Isolated Particle Deposition (IPD). Major parameters that influenced the UHMWPE Deposition efficiency significantly were the particle temperature and velocity and net surface activity of FNA. The stored elastic energy of UHMWPE decreases with increase in temperature, and the Deposition criterion for a successful UHMWPE Deposition is not to have net stored elastic energy after impact. Effect of FNA was seen in generating H-bonds that helped to establish bridge bond at UHMWPE-substrate interface.
J Robertson - One of the best experts on this subject based on the ideXlab platform.
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Deposition Mechanism of hydrogenated amorphous silicon
Journal of Applied Physics, 2000Co-Authors: J RobertsonAbstract:The surface and subsurface processes occurring during the growth of hydrogenated amorphous silicon (a-Si:H) are analyzed to understand how dangling bond defects and weak bonds form. It is found that the abstraction and addition of adsorbed SiH3 radicals gives a surface defect density which decreases continuously with decreasing temperature with no minimum near 250 °C. Hence it cannot be the process that defines defect densities in the bulk. Hydrogen elimination to create the bulk Si–Si network occurs because the chemical potential of hydrogen causes the expulsion of hydrogen from the bulk. Hydrogen elimination is the rate-limiting step at lower temperatures, as its diffusion is slow. The difficulty of eliminating hydrogen leads to the formation of weak bonds. Weak bonds arise at higher Deposition temperatures from thermal disorder. The dangling bond defects arise from weak bonds by the defect pool process, and this process must continue at lower temperatures than normal in the growth zone. Plasma processe...
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effects of Deposition temperature on the properties of hydrogenated tetrahedral amorphous carbon
Journal of Applied Physics, 1997Co-Authors: S Sattel, J Robertson, H EhrhardtAbstract:The properties of hydrogenated carbon films deposited from a highly ionized hydrocarbon plasma beam are studied as a function of Deposition temperature. At low temperatures, the films have high sp3 bonding, density, and compressive stress and are very smooth. Two transition temperatures are observed, a lower transition T1 around 250 °C, dependent on ion energy, due to graphitization of C–C bonds, and a higher one T2 at about 450 °C due to the loss of hydrogen. The roughness rises at T1 and falls above T2. These transitions are used to understand the subplantation Deposition Mechanism. The optical gap varies differently, decreasing gradually across T1 due to ordering of sp2 sites. We also report the temperature dependence of the x-ray diffraction, Raman spectrum, elastic modulus, hardness, substrate adhesion, friction coefficient, refractive index, and paramagnetic defect density. The friction coefficient of ta-C:H is low (0.05–0.1), and is maintained at ambient humidities, unlike for a-C:H. The friction m...
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the Deposition Mechanism of diamond like a c and a c h
Diamond and Related Materials, 1994Co-Authors: J RobertsonAbstract:Diamond-like carbon (DLC) is a dense, partially sp3 bonded metastable phase of non-crystalline carbon or hydrogenated amorphous carbon formed by the Deposition from medium energy (50–500 eV) ion beams. The sp3 bonding arises from C ions entering subsurface atomic sites and producing a quenched-in density increase. The process has an optimum ion energy of about 100 eV because the C ions must have sufficient energy to penetrate the surface, but any excess energy could anneal out the density increment. The process is an ion-induced compression of sp2 a-C into the denser sp3 phase. Deposition of a-C: H is more complex, involving a growth step, ion-induced dehydrogenation and ion-induced compression of the C-C skeleton. In the growth step, ions incorporate directly into the films whereas slow neutral species first form an adsorbed layer which then may incorporate into the bulk. Ion bombardment causes dehydrogenation by the preferential displacement of hydrogen and compresses sp2 sites into sp3 sites, forming extra bonds in the C-C skeleton, as in a-C.
Kunihito Koumoto - One of the best experts on this subject based on the ideXlab platform.
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site selective Deposition of magnetite particulate thin films on patterned self assembled monolayers
Chemistry of Materials, 2004Co-Authors: Tsuyoshi Nakanishi, Yoshitake Masuda, Kunihito KoumotoAbstract:Magnetite micropatterns were successfully fabricated by the site-selective Deposition technique using self-assembled monolayers (SAMs) as templates. Magnetite particles were selectively deposited on Pd catalysts which were adsorbed to the −NH2-terminated surface of a SAM, in an aqueous solution containing iron nitrate and dimethylamine−borane. Pd colloid catalyst particles were adhered to the amino group of a patterned SAM by electrostatic interaction. Crystalline Fe3O4 (magnetite) particulate films were then deposited on amino-group regions by the effect of metal Pd catalyst. Site-selective Deposition of crystalline Fe3O4 was thus realized in an aqueous solution. The Deposition Mechanism of Fe3O4 is discussed in detail in comparison with the Deposition of γ-FeOOH in the solution.
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Deposition Mechanism of anatase tio2 on self assembled monolayers from an aqueous solution
Chemistry of Materials, 2003Co-Authors: Yoshitake Masuda, Won-seon Seo, T Sugiyama, Kunihito KoumotoAbstract:The nucleation and growth process of anatase TiO2 on several kinds of self-assembled monolayers (SAMs) in an aqueous solution has been evaluated in detail. Homogeneously nucleated TiO2 particles and amino groups of SAM showed negative or positive ζ potential in the solution, respectively. The adhesion of TiO2 particles to the amino group surface by attractive electrostatic interaction caused rapid growth of TiO2 thin films in the supersaturated solution at pH 2.8. On the other hand, TiO2 was deposited on SAMs without the adhesion of TiO2 particles regardless of the type of SAM in the solution at pH 1.5 whose degree of supersaturation is low as a result of a high concentration of H+. Additionally, the orientation of films deposited on all SAMs was shown to be improved by enlarging the reaction time regardless of the kind of SAM or pH. It is conjectured that the adsorption of anions to specific crystal planes caused c-axis orientation of anatase TiO2.