Film formation

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Structure dependent growth control in nanowire synthesis via on film formation of nanowires

Structure dependent growth control in nanowire synthesis via on film formation of nanowires

On-film formation of nanowires, termed OFF-ON, is a novel synthetic approach that produces high-quality, single- crystalline nanowires of interest. This versatile method utilizes stress-induced atomic mass flow along grain boundaries in the polycrystalline film to form nanowires. Consequently, controlling the magnitude of the stress induced in the films and the microstructure of the films is important in OFF-ON. In this study, we investigated various experimental growth parameters such as deposition rate, deposition area, and substrate structure which modulate the microstructure and the magnitude of stress in the films, and thus significantly affect the nanowire density. We found that Bi nanowire growth is favored in thermodynamically unstable films that facilitate atomic mass flow during annealing. A large film area and a large thermal expansion coefficient mismatch between the film and the substrate were found to be critical for inducing large compressive stress in a film, which promotes Bi nanowire growth. The OFF-ON method can be routinely used to grow nanowires from a variety of materials by tuning the material-dependent growth parameters.
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Dynamics of polymer film formation during spin coating

Dynamics of polymer film formation during spin coating

(Received 24 May 2014; accepted 17 September 2014; published online 26 September 2014) Standard models explaining the spin coating of polymer solutions generally fail to describe the early stages of film formation, when hydrodynamic forces control the solution behavior. Using in situ light scattering alongside theoretical and semi-empirical models, it is shown that inertial forces (which initially cause a vertical gradient in the radial solvent velocity within the film) play a signif- icant role in the rate of thinning of the solution. The development of thickness as a function of time of a solute-free liquid (toluene) and a blend of polystyrene and poly(methyl methacrylate) cast from toluene were fitted to different models as a function of toluene partial pressure. In the case of the formation of the polymer blend film, a concentration-dependent (Huggins) viscosity formula was used to account for changes in viscosity during spin coating. A semi-empirical model is intro- duced, which permits calculation of the solvent evaporation rate and the temporal evolution of the solute volume fraction and solution viscosity. V C 2014 Author(s). All article content, except where
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Controlling the Passive Oxide Film Formation on Indium Electrode in Na2B4O7 Solutions

Controlling the Passive Oxide Film Formation on Indium Electrode in Na2B4O7 Solutions

examined [28]. Complex structural characterizations of the anodically formed indium oxide film have been studied using galvanostatic [28], cyclic voltammetry and impedance spectroscopy [29] techniques. It has been found that the behavior of indium during anodic oxidation resembles in many aspects the kinetics of anodization of valve metals (e.g. Ta, Zr, Ti, Al, Sb, Bi). This conclusion has been deduced from the linearity between the current density and (i) the oxide formation rate ; (ii) the reciprocal capacity (the unitary formation rate); (iii) the potential drop across the oxide layer. The kinetics and chemical stability of potentiostatically formed indium oxide films were discussed by Saidman et al. [30] as a function of potential domain, time diffusing process, and hydroxide concentration. It has been concluded that the surface indium oxide film undergoes reductive decomposition to pure metallic indium in the solid phase, via the solid-state mechanism [30]. Thus, it is possible to generate an oxide- free indium surface in situ, by applying a sufficiently negative potential. This, together with the fact that indium has a large hydrogen evolution overpotential, is the basis for a possible application of indium as a cathode catalyst material [31]. Saidman et al. [30, 32] also discussed the kinetics and chemical stability of potentiostatically formed oxide films as a function of potential domain, time diffusing process, and hydroxide concentration. Munoz and Bessone [33] reported on the cathodic behavior of indium in the presence of chloride ions. The hydrogen evolution reaction and the effects of local alkalization, Cl - ions concentration and the presence of surface oxide were analyzed. The data show the presence of a cathodic current density plateau (cd), this latter being attributed to a possible catalytic effect exerted by the oxide layer on the hydrogen evolution reaction. An increase of Cl - ions concentration generates a shift of the cd plateau towards lower cathodic cd values. The appearance of a rise in the anodic cd at a potential close to -1.1 V was found to be dependent of the Cl - ions concentration and to be controlled by mass transfer. The aim of the present work is to shed more light on the oxide film formation and growth on an indium electrode in sodium borate solutions. The effect of the some factors, e.g., solution concentration (1 x 10 -4 – 1 x10 -1 M), and pH (9.13-11.49), as well as, temperature changes (25-55 o C) on the initial rate of oxide film growth are examined. The effect of addition of some aggressive salts such as, NaCl, NaBr and NaI on the stability of the oxide film formed is also examined.
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The Effect of Acetic Acid on Film Formation in Carbon Dioxide Corrosion

The Effect of Acetic Acid on Film Formation in Carbon Dioxide Corrosion

scale formation[18]. At low temperatures, corrosion rates increase because of high solubility of the FeCO film. As temperature increases (around 60-80°C) the iron 3 carbonate layer becomes more adherent to the metal surface and more protective in nature resulting in a decrease of the corrosion rate. Under this condition, dense crystalline films are formed which often give good protection. The effect film formation on corrosion rate at different temperatures is proposed by DeWaard and Milliams, shown in Figure 2.4 below.
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Electrochemical Analysis of Passivation Film Formation on Steel Rebar in Concrete

Electrochemical Analysis of Passivation Film Formation on Steel Rebar in Concrete

Different methods have been established for analysis of the stainless steel materials [7, 8]. Among them, electrochemical approach has been found more reliable. Studies showed the successful application of an electrochemical method for analyzing passivation film formation at different materials such as iron [9, 10], carbon steel [11, 12] and stainless steel [13-15]. On the other hand, X- ray photoelectron spectroscopy analysis has been found more accurate for composition status analysis. Analysis of the passivation film on the steel rebar was very complicated because many parameters could affect its performance including temperature, oxygen content, pH condition, type of electrolyte and composition of the alloy [16].
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Experimental and numerical investigations of oil film formation and friction in a piston ring-liner contact

Experimental and numerical investigations of oil film formation and friction in a piston ring-liner contact

If an array of the successive pulses of interest (i.e. pulse (II) in Fig. 6a) individually captured by the sensors is analyzed, the film thickness values at the fixed sensor locations can be obtained. These film thickness values can be superimposed on a single graph. Fig. 7 shows the measurements of film thickness as the ring reciprocates at 2.5 Hz under a normal load of 80 N. In the figure, the ring starts its travel from TDC to BDC, thus it is initially captured by sensor 1 (i.e. close to TDC). As the ring moves from one sensing area to the next, the other sensors detect the ring re- spectively. This roughly provides an overview of lubricant film formation over the stroke. It is notable that the film thickness data from cy- cle to cycle was very repeatable. The horizontal axis in the figure is given in terms of pulse num- ber, however this could be converted to time if the pulse rate (indicating how many ultrasound pulses are sent through the liner specimen in a second) is known. In this case the pulse rate is 2000 pulses per second. This was also confirmed because it can be seen in the figure that two and
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Surface Modification of Iron for Corrosion Protection: Kinetics of Anodic Film Formation and Electroreduction

Surface Modification of Iron for Corrosion Protection: Kinetics of Anodic Film Formation and Electroreduction

The majority of work in the first area is devoted to the study of oxide film formation/passivation and the characterization of the structural and electronic properties of the passive film, especially in near neutral borate buffer solutions 1-14. There are several advantages of using this electrolyte solution: (a) the borate ions posses the adsorption affinity much smaller than other anions [14, (b) the oxide layer is chemically stable in a wide potential range [4], (c) the active to passive transition occurs with small current densities [2,3], and (d) the potential drop in the Helmholtz layer is constant and depends only on the pH, and any change of the electrode potential causes a change of the potential drop in the oxide 11.
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Differential dehydration effects on globular proteins and intrinsically disordered proteins during film formation

Differential dehydration effects on globular proteins and intrinsically disordered proteins during film formation

Abstract: Globular proteins composed of different secondary structures and fold types were exam- ined by synchrotron radiation circular dichroism spectroscopy to determine the effects of dehydra- tion on their secondary structures. They exhibited only minor changes upon removal of bulk water during film formation, contrary to previously reported studies of proteins dehydrated by lyophiliza- tion (where substantial loss of helical structure and gain in sheet structure was detected). This near lack of conformational change observed for globular proteins contrasts with intrinsically dis- ordered proteins (IDPs) dried in the same manner: the IDPs, which have almost completely unor- dered structures in solution, exhibited increased amounts of regular (mostly helical) secondary structures when dehydrated, suggesting formation of new intra-protein hydrogen bonds replacing solvent-protein hydrogen bonds, in a process which may mimic interactions that occur when IDPs bind to partner molecules. This study has thus shown that the secondary structures of globular and intrinsically disordered proteins behave very differently upon dehydration, and that films are a potentially useful format for examining dehydrated soluble proteins and assessing IDPs structures. Keywords: globular proteins; intrinsically disordered proteins; synchrotron radiation circular dichro- ism (SRCD) spectroscopy; dehydration; unfolding; folding; secondary structure
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Dynamics of polymer film formation during spin coating

Dynamics of polymer film formation during spin coating

(Received 24 May 2014; accepted 17 September 2014; published online 26 September 2014) Standard models explaining the spin coating of polymer solutions generally fail to describe the early stages of film formation, when hydrodynamic forces control the solution behavior. Using in situ light scattering alongside theoretical and semi-empirical models, it is shown that inertial forces (which initially cause a vertical gradient in the radial solvent velocity within the film) play a signif- icant role in the rate of thinning of the solution. The development of thickness as a function of time of a solute-free liquid (toluene) and a blend of polystyrene and poly(methyl methacrylate) cast from toluene were fitted to different models as a function of toluene partial pressure. In the case of the formation of the polymer blend film, a concentration-dependent (Huggins) viscosity formula was used to account for changes in viscosity during spin coating. A semi-empirical model is intro- duced, which permits calculation of the solvent evaporation rate and the temporal evolution of the solute volume fraction and solution viscosity. V C 2014 Author(s). All article content, except where
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The Impact of Asphaltene Chemistry and Solvation on Emulsion and Interfacial Film Formation

The Impact of Asphaltene Chemistry and Solvation on Emulsion and Interfacial Film Formation

reached very near the solubility limit where the largest aggregates were formed. These aggregates approached their limit of solubility and were prone to interfacial adsorption. At low aromaticity, AH Soluble formed stronger emulsions than the Whole or Precipitate fraction. This stability shift was caused by the greater availability of material still soluble to adsorb and stabilize oil-water interfaces. As toluene concentration was lowered and more precipitates formed the emulsion stability fell. AH Soluble formed stable emulsions over a very narrow heptol range, while increased solubility from 40 to 45 % (v/v) toluene led to slightly smaller aggregates (less than 35 Å) and a dramatic drop in stability. AH Precipitate asphaltenes formed the weakest emulsions due to large aggregate formation and low surface activity. Both AH Soluble and Whole form smaller aggregates and have a lower % toluene solubility limit than the other asphaltenes investigated here. In addition, the emulsions formed appear to be quite weak due to high asphaltene solubility and low polarity. Even though AH Precipitate asphaltenes are slightly enriched with aromatic carbon and polar nitrogen resulting in slightly larger aggregates, the degree of interfacial film formation and cohesion is still low.
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Study of Bi film Formation on Different Carbon Based Electrodes for Possible Applicability in Electroanalytical Determination of Cysteine

Study of Bi film Formation on Different Carbon Based Electrodes for Possible Applicability in Electroanalytical Determination of Cysteine

The bismuth film formation from acid nitrate solution on glassy carbon electrode (GCE), graphite electrode (GPE) and on an assembly of carbon fiber microelectrodes (CFME) were studied utilizing cyclic voltammetry (CV) and chronoamperometry (CA). Voltamemetric data obtained with all three electrodes indicate that bismuth electrodeposition is controlled by diffusion of Bi 3+ . In the case of GCE and GPE Bi 3+ diffusion coefficient was calculated using Randles-Sevcik equation. Analysis of the experimental current transients, obtained with GCE and GPE, revealed that increment of Bi 3+ concentration changes nucleation mechanism from three-dimensional (3D) progressive nucleation toward instantaneous. Transients obtained with CFME, at different Bi 3+ concentrations, suggesting only 3D instantaneous nucleation mechanism. Obtained data were used for preparation of appropriate Bi layer on CFME (Bi-film/CFME) for electroanalytical determination of cysteine by using square wave cathodic stripping voltammetry (SWCSV). Optimization of the SWCSV parameters have resulted in good linearity over examined concentration range of 1.0 μmol dm -3 to 10.0 μmol dm -3 , with detection limit of 0.028 μmol dm -3
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UNDERSTANDING ALUMINUM ANODIC OXIDE FILM FORMATION: IMPROVING ENGINEERING PROPERTIES THROUGH MICROSTRUCTURAL MODIFICATION

UNDERSTANDING ALUMINUM ANODIC OXIDE FILM FORMATION: IMPROVING ENGINEERING PROPERTIES THROUGH MICROSTRUCTURAL MODIFICATION

Based upon the ideas proposed in the Constraint Concept of Film Formation [6], in order to modify an anodic finish, change must be introduced that is electroactive or “charged” in nature. Therefore, one can change the external electrical parameters of the anodization process, or change the electrolyte through the introduction of a supplementary counter ion. The counter ion can be active or passive, or completely inert. Active counter ions will facilitate finish growth, as with an oxalate ion. Passive counter ions will react with the pore wall but oxidize immediately as with a chromate ion, limiting finish growth. An inert additive may be a surface active agent that although soluble in the electrolyte, does not participate in the anodization reaction at all. These additions serve, through esterification or similar reaction, to buffer the heat of reaction that occurs with alloy additions, interfacial defects and contamination and help prevent finish damage due to resistance heating.
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In situ simultaneous photovoltaic and structural evolution of perovskite solar cells during film formation

In situ simultaneous photovoltaic and structural evolution of perovskite solar cells during film formation

In summary, we investigate the performance of perovskite solar cells during the formation of the perovskite starting from the earliest stages of its conversion from the precursors and solvent to the fully formed perovskite and during its degradation employing simultaneous Grazing Incidence Wide Angle X-ray Scattering and current–voltage measurements on films annealed in situ and deposited on interdigitated back-contact substrates. This suite of analyses allows establishing a direct correlation between the crystallographic and photovoltaic properties of work- ing solar cells. The remarkably clean semiconductor behaviour of perovskites is evidenced by the high photovoltages measured at the first stages of perovskite conversion from precursors, at the percolation threshold for bulk conductance. Open circuit voltages reach maximum value before the precursor has fully converted into perovskite, when the fraction of precursor and perovskite crystals are comparable. Short circuit currents and power conver- sion efficiencies follow a trend similar to that of the perovskite Fig. 3 Normalized short circuit current and open circuit voltage of IBC
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Catalysing surface film formation

Catalysing surface film formation

Despite its importance, this SEI is not a rationally designed material with tailored composition and structure. Instead, a good portion of experimental luck helped discover that certain organic-solvent based electrolytes decompose into a film that does this job. Soon, a few additives were discovered that helped improve and stabilize the SEI over longer terms 2 . Nowadays, the initial so-called

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The impact of high frequency high current perturbations on film formation at the negative electrode electrolyte interface

The impact of high frequency high current perturbations on film formation at the negative electrode electrolyte interface

Long term ageing experimental results show that degradation resulting from coupled DC and AC current waveforms lead to additional degradation of lithium-ion batteries above that experienced through pure DC cycling. More profoundly, such experiments show a dependency of battery degradation on the frequency of AC perturbation. This paper addresses the underlying causality of this frequency dependent degradation. Cell autopsy techniques, namely X-ray photoelectron spectroscopy (XPS) of the negative electrode surface film, show growth of surface film components with the superimposition of an AC waveform. XPS results show that high frequency AC perturbations lead to the increased formation of a passivating film. In order to determine the cause of this increased film formation, a heterogeneous electrochemical model for the LiNiCoAlO 2 /C 6 lithium ion battery coupled with governing equations for
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Model and experiments to determine lubricant film formation and frictional torque in aircraft landing gear pin joints

Model and experiments to determine lubricant film formation and frictional torque in aircraft landing gear pin joints

In order to determine the friction coefficient using equation (10) the film thickness and proportions of liquid and solid contact are needed. One approach of doing this has been developed by Lu et al [3] and Gelinck & Schipper [11], who set up a mixed lubrication model to calculate Stribeck curves for line contacts. In this paper, this model was chosen to establish a friction and lubrication model for the pin joint. As in the mixed lubrication regime both elastohydrodynamic lubrication (EHL) and asperity contact exist to support the total load. So in this lubrication model the elastohydrodynamic lubrication theory and rough surface contact theory are needed. The following part explains this mixed lubrication model.
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In situ simultaneous photovoltaic and structural evolution of perovskite solar cells during film formation

In situ simultaneous photovoltaic and structural evolution of perovskite solar cells during film formation

Metal-halide perovskites show remarkably clean semiconductor behaviour, as evidenced by their excellent solar cell performance, in spite of the presence of many structural and chemical defects. Here, we show how this clean semiconductor performance sets in during the earliest phase of conversion from the metal salts and organic-based precursors and solvent, using simultaneous in-situ synchrotron X-ray and in-operando current-voltage measurements on films prepared on interdigitated back-contact substrates. These structures function as working solar cells as soon as sufficient semiconductor material is present across the electrodes. We find that at the first stages of conversion from the precursor phase, at the percolation threshold for bulk conductance, high photovoltages are observed, even though the bulk of the material is still present as precursors. This indicates that at the earliest stages of perovskite structure formation, the semiconductor gap is already well-defined and free of sub-gap trap states. The short-circuit current, in contrast, continues to grow until the perovskite phase is fully formed, when there are bulk pathways for charge diffusion and collection. This work reveals important relationships between the precursors conversion and device performance and highlights the remarkable defect tolerance of perovskite materials.
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Film formation and some structural features of hemicellulose fractions from Pinus densiflora leaves

Film formation and some structural features of hemicellulose fractions from Pinus densiflora leaves

break of films from AHC, AHC-X (with 1 % lecithin), and AHC-M are summarized in Table 3. No significant dif- ferences in tensile properties were observed between the three fractions. The average tensile strength of AHC was 43 MPa, which was lower than that previously reported for xylan films without additives (52 MPa from rye endosperm arabinoxylan film; a 20–25 lm thick film [27] and 50 MPa from barley husk arabinoxylan film; a 49 ± 7-lm thick film [28]). No significant difference in elongation at break was observed between the three fractions. The average elongation at break of films from the AHC series ranged between 2 and 2.5 %. A decrease in tensile strength and an increase in elongation at break are observed when the amount of plasticizer additives is increased [6, 7, 9]. Thus, previous reports suggest that by selecting appropriate additives, the properties of hemicellulose films from P. densiflora leaves can be improved.
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Film formation of non planar phthalocyanines on copper(i) iodide

Film formation of non planar phthalocyanines on copper(i) iodide

are 6.6, 11.0 and 18.2 nm respectively. At 25 nm there are still areas of the CuI lm which appear bare as the islands of the VOPc have not yet coalesced. Although it is possible that continuous layers of VOPc form over the CuI lm the visibility of VOPc islands at thicknesses as low as 1 nm suggests that a Volmer–Weber growth mode is dominant in the formation of VOPc lms on CuI.

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Phenomena of Intergranular Liquid Film Formation in Technology

Phenomena of Intergranular Liquid Film Formation in Technology

The fundamental properties of the solid crystalline materials i.e. phenomena of first-order phase transition of grain boundary with formation of two-dimensional quasi-liquid phase have described with means of the funda- mental equations of film thermodynamics. The obtained generalized equation had been used for the calculating of the phase transition temperature T Sf of grain boundary for some metals. The obtained values found within the

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