Depth profiling of clear coil coating by confocal Raman microscopy

Confocal Raman microscopy (CRM) has been demonstrated to be very effective in the analysis of the distribution of chemical moieties within polymeric coil coatings. To verify the compatibility of CRM with commercial coil coatings, a multi-layer coil coating system was prepared and depth profiled by CRM with both dry and immersion oil objectives (non-destructive method). The cross-section of the same sample was then scanned by CRM (destructive method). It was found that the CRM depth profiling resolution was affected by both the intrinsic and extrinsic factors of the objective lens. The use of an immersion oil objective improved depth resolution and minimised the refraction effect, however the oil contaminated the coating surface. The dry method yielded the lowest depth resolution but was completely non-destructive. The CRM lateral scanning of the sample cross-section yielded the most accurate depth profile information; however, the destructive nature of this method is a major disadvantage. It was also found that pigments incorporated in the coil coating formulation affected the CRM depth profiling accuracy due to the strong Raman scattering of these materials.     

Photothermal imaging of dehydrochlorination in poly(vinyl chloride) films

Impulse (time domain) laser photopyroelectric effect spectrometry uses the time dependence of heat diffusion in an irradiated sample to infer optical and thermal property depth distributions in the sample. This method was used in conjunction with a recently reported method of inverse problem theory to recover the depth dependence of optical absorption in photodegraded thin films of poly(vinyl chloride) (PVC) on a depth scale of a few tens of microns. The thin films were photodegraded under broadband ultraviolet light prior to photothermal analysis to induce subsurface profiles of visible absorption arising from the depth dependence of light initiated dehydrochlorination reactions in the films. Optical depth profile reconstructions could be made in samples that had undergone mild degradation only and where the absence of significant thermal effusivity changes accompanying degradation could be confirmed. Reconstructed optical transmission profiles were compared with optical transmission micrographs and were shown to resolve features that arise from the depth dependence of photo-induced dehydrochlorination reactions in the films. The extent of these latter reactions is controlled by the depth dependence of the oxygen concentration in the films.     

Confocal Raman study of poly(ethylene terephthalate) fibres dyed in supercritical carbon dioxide: dye diffusion and polymer morphology

Confocal Raman microscopy (CRM) has been used to extract dye diffusion data from poly(ethylene terephthalate) (PET) fibres dyed with Disperse Yellow 23 under supercritical CO₂ conditions. Spectral information as a function of depth was measured in a non-destructive manner using dry and oil objectives in confocal Raman mode. Mapping along the radius of the fibre cross-section was performed and compared to the data from the confocal measurements. A significant dye concentration gradient has been observed along the line normal to the fibre surface which the data from the oil confocal measurements accurately describes to a depth of 45 μm. The effect of the supercritical CO₂ dyeing process on the fibre morphology has also been evaluated using CRM.     

Fluorine depth profiling by high-resolution 1D magnetic resonance imaging

High-resolution magnetic resonance imaging (MRI) has been used, for the first time, to measure fluorine concentration profiles with a high spatial resolution (5 μm) along the full film depth of fluorinated polyurethane films. The MRI fluorine profiles were consistent with the results obtained by X-ray photoelectron spectroscopy (XPS) in combination with microtoming. MRI is a nondestructive and potentially quantitative technique for probing the spatial distribution of small quantities of fluorine in coatings and multi-layered systems.     

Spatial depth profiling of chromophores in thin polymer films using photopyroelectric spectroscopy

Frequency domain photopyroelectric effect spectrometry (FD-PPES) is a recent spectroscopic technique that may be used to recover depth profiles of optical absorption in thin films on a noncontact and nondestructive basis. In this work a series of well characterized thermally homogeneous samples were prepared that exhibited continuous or discrete subsurface profiles of optical absorption. Multifrequency FD-PPES measurements made on these samples were compared to theory using a heat transfer model, which we have developed for a multilayer thermally homogeneous absorber. Excellent agreement between experiment and theory was obtained for these model studies. While both phase and magnitude channels of the FD-PPES response give depth profiling information, the phase response is especially sensitive to variations in the subsurface profile of optical absorption. By means of the phase response it is possible to determine the number and spatial positions of absorbers in a series of discrete absorbing layers. The FD-PPES. technique has excellent potential for analysis and nondestructive evaluation of polymer films.     

The influence of nitrogen incorporation on the optical properties of anodic Ta2O5

Anodic oxides were grown on sputter-deposited Ta in different aqueous solutions. A photoelectrochemical investigation was performed in order to estimate the band gap of the films as a function of the anodizing bath composition and formation voltage, i.e. thickness. Photoelectrochemical results provided evidence of sub-band gap photocurrent for films formed in a bath containing ammonium ions at pH 9. Elemental depth profiles obtained by glow discharge optical emission spectroscopy revealed the presence of nitrogen species in the outer part of the anodic films, which is bonded to Ta according to XPS analysis. A mechanism of nitrogen incorporation is proposed in order to account for the pH dependence of film composition.     

A depth-resolved look at the network development in alkyd coatings by confocal Raman microspectroscopy

The formation of molecular networks related to the consumption of unsaturated carbon-carbon double bonds (CC) during oxidative drying of alkyd coating films incorporating unsaturated fatty acids was studied. The concentration of CC bonds was measured as a function of drying time and distance from the exposed film surface (depth) using confocal Raman microspectroscopy (CRM). The change in spatial distribution of the CC double bond concentration across the film cross section provides information on the kinetics of the oxidative cross-linking process in the alkyd films. It was found that the CC bond consumption is not homogeneous across the depth of the drying film. The results obtained allowed us to quantitatively monitor the progress of the drying process and the movement of the ‘drying front’ within the coating films. The drying profiles suggest that oxygen penetration into the coating film is a rate-limiting factor in the drying process. Depth profiles during the film forming process develop due to local variations in the oxygen solubility, diffusion coefficient of oxygen, and available amount of double bonds for cross-linking. The influence of several industrially relevant factors, like oil length of the alkyd resin, thickener, solvent, and drier on the film formation process is discussed. Depth resolution of the analytical approach and spatial accuracy of confocal Raman microspectroscopy are also treated.     

Improving the formation and protective properties of silane films by the combined use of electrodeposition and nanoparticles incorporation

The electrodeposition and nano-silica incorporation were used together to prepare the novel composite dodecyltrimethoxysilane/SiO₂ thin films from silane sol-gel system on aluminum substrate. The results showed that both the two techniques can improve the films formation and their protectiveness. The influences of the deposition potential and the silica content in silane solution were investigated. A “critical deposition potential” and a “critical silica content” were both observed, under which the obtained silane films had the highest protective properties. The enhancement in film thickness has been detected by these two techniques from the elemental depth profiles of silane films as measured by secondary-ion mass spectroscopy (SIMS). Current-time curves were on-line recorded on aluminum electrodes in silane solutions. As compared with that in blank solution, the current response was found to be larger in silica-contained precursor, probably suggesting that the silica particles participate in the film deposition.     

APPLICATION OF LASER DIAGNOSTIC TECHNIQUES FOR THE EXAMINATION OF LIQUID FUEL SPRAY STRUCTURE

Results are presented on the spatial distribution of droplet mean size and number density obtained from a hollow-cone kerosene spray, introduced into nonswirling and swirling flow fields. An ensemble light scattering technique, based on measurement of the polarization ratio, has been employed to determine local droplet characteristics in both dense and dilute regions of the spray. The measurements are complemented with Lorenz-Mie calculations of the scattering characteristics for a polydispersion of droplets; the calculations were carried out for different mean sizes and refractive indices. The results reveal that the degree of swirl imparted to the surrounding air flow has a strong influence on spray structure. For all conditions examined the droplet mean size is found lo be larger on the spray boundary than towards the centerline. Droplet mean size is also found to increase with axial distance at all radial positions of the spray; this trend is attributed to the vaporization of smaller droplets and/or possible coalescence between the droplets.

In addition to the ensemble technique, measurements have also been obtained with the phase/Doppler interferometry and light intensity deconvolution techniques under identical experimental conditions. The droplet mean sizes obtained with the ensemble approach are in general smaller than those measured with the phase/Doppler technique; however, general features of the radial profiles obtained with both techniques are similar. The deconvolution technique also indicates the presence of smaller size droplets and supports the results obtained with the ensemble technique. The selective sensitivity of these sizing techniques to different ranges of droplet size and number density is discussed.     

Investigation of Glasses Using Surface Profiling by Spectrochemical Analysis of Sputter-Induced Radiation: I, Surface Profiling Technique with High In-Depth Resolution

Experimental equipment was developed to investigate concentration gradients in solid surface layers; the radiative de-excitation of elements and molecules which are ejected from the ion beam-bombarded solid and the luminescence excitation within the surface layer are recorded spectrographically. Examples show how elemental composition profiles can be calibrated with respect to depth. An in-depth resolution of a few nanometers can be obtained. The original profiles are distorted by energy and charge transfer and by other peculiarities connected with ion-beam etching; the extent to which these distortions must be taken into consideration in interpreting the results is discussed. Interdiffusion-controlled solid-state reactions of thin oxide films with a glass substrate were investigated. Advantages and disadvantages of the method for analysis and concentration profiling of glass surfaces and oxide layers on glasses in glass research and industry are discussed.     

Raman Spectroscopy of Laminated Polymer Films by Integrated Optical Techniques

Raman spectra have been observed from two adjacent thin polymer films and the interfacial region. This has been made possible by the application of integrated optical techniques to Raman spectroscopy. The observed Raman spectra have their strongest intensity contributions from regions near the optical field intensity maxima, which can occur in either film or at the interface. Both the optical intensity and the scattering volume are increased significantly and Raman spectra with good signal-to-noise ratios can be obtained. The method will be briefly illustrated and spectra for a thin film of poly(styrene) on a film of polyvinyl alcohol) will be shown for various (modes) optical profiles.     

Multilayer method as a tool for depth dependent polymer film photodegradation studies

A new polymer film destructive depth profiling protocol is presented for the analysis of photo‐ and thermally degraded thin films on the depth scale of less than 100 microns. The method, demonstrated here on thin films of poly(vinyl chloride) (PVC), provides a means of preparation of thin laminates of high optical quality comprised of many (>20) thin layers of individual thickness less than 15 microns. The constituent layers are fused together under appropriate pressure, temperature and time treatment to yield a film assembly of high optical quality that behaves like a uniform single layer during photodegradation exposure, but which may still be separated after treatment. Compared to previous techniques, this new method is relatively simple and non‐labor intensive. Film adhesive properties are controlled to within ± 5% Concentration depth profiles of polymer photolysis products were reconstructed by analyzing each of the separated layers using UV‐visible spectrophotometry. The continuity of these film assemblies with respect to mechanical properties, adhesive properties and the depth distribution of key photolysis reagents and products was confirmed using photothermal and reference microscopy techniques. Optical absorption depth profiles examined in UV‐ photodegraded poly(vinyl chloride) (PVC) films exhibited the classic dependencies expected in the presence of nitrogen and oxygen atmospheres.     

The behavior of incorporated impurities in tantalum anodic oxide films at the dielectric breakdown

Distribution profiles of incorporated impurities in anodic oxide films of tantalum were investigated before and after the dielectric breakdown of the film as a function of the depth of the film for incorporation of phosphorus, sulfur and chlorine. The in-depth distribution profiles of the incorporated impurities dramatically changed at the breakdown of the oxide films. However, the trend of the change was quite different among the incorporated impurities; chlorine is concentrated in the interior of the film, but phosphorus and especially sulfur showed tendencies to be swept into electrolytes. The ionization of the film seems to be responsible for these phenomena.     

Application of the SIMS Method in Studies of Cr Segregation in Cr-Doped CoO: I, Aspects of Quantitative Analysis

Aspects of calibration of intensities of SIMS secondary ions vs concentration as well as sputtering time vs depth are considered for Cr-doped CoO. Advantages and limitations of the SIMS method in quantitative analysis of segregation-induced concentration profiles in oxide crystals are discussed. The studies indicate a substantial effect due to charging the surface during sputtering. The depth calibration was performed by using the Ta₂O₅/Ta system as a standard. Good depth resolution was revealed. The calibration dependence of Cr intensities on concentration is characterized by a wide scatter of data caused by charging the surface. Very good shape reproducibility of the intensity ratio vs depth profiles was revealed. Therefore, normalized intensity ratios can be used for calibration.     

Synthesis and properties of castor oil-based waterborne polyurethane cloisite 30B nanocomposite coatings

Waterborne polyurethane dispersions (WPUDs) were synthesized successfully from castor oil-based polyol, isophorone diisocyanate and dimethylol propionic acid with NCO/OH ratio of 1.5. Different weight percentages of cloisite 30B (1, 2, and 3 wt%) were loaded with WPUDs to prepare nanocomposite films. Prepared prepolymer and nanocomposite films were characterized using FTIR, XRD, SEM, TEM, DSC, and TGA techniques, and coating properties, such as pencil hardness, abrasion resistance, impact resistance, and contact angle, were evaluated. The results obtained from different amounts of clay loading were compared with the pristine castor oil-based WPUDs. The FTIR spectra deconvolution technique was used to study the hydrogen bonding effect within the polymer with an increase in clay content. TGA analysis showed that the thermal stability of WPUDs increases with cloisite 30B (C30B) content. The surface morphology and hydrophilicity/hydrophobicity nature of the nanocomposite films were characterized using scanning electron microscopy and contact angle measurement. The results obtained from tensile tests indicated that the mechanical property of the dispersion system improved with C30B content. A high-performance castor oil-based nanocomposite coating with low volatile organic component can be targeted as an outcome of this work.     

Controlled Elemental Depth Profile in Sol–Gel-Derived PZT Films

Elemental depth profiles of PZT films prepared by two sol–gel formulations, differing in the zirconium precursor stabilization, were investigated by SIMS analysis. Early decomposition of the zirconium precursor yielded opposing gradients of zirconium and titanium, while simultaneous late decomposition of zirconium and titanium precursors provided profile uniformity. The gradients formed during initial crystallization are irreversible. Both types of films showed excellent hysteresis; however, uniform films exhibited a much higher dielectric constant, indicating superior piezoelectric properties. Non-uniform films displayed a complex CV pattern, consistent with an inhomogeneous structure. Finally, thermal decomposition of the individual metal precursors is crucial for controlling film uniformity.     

Resonance raman spectroscopy of polydiacetylene langmuir-blodgett films

Resonance Raman excitation profiles of two vibrational modes have been measured for Langmuir-Blodgett films of a polydiacetylene. The polymer films were formed by exposing multilayer samples of the Cd salt of 10,12-pentacosadiynoic acid to ultraviolet radiation. Raman spectra were measured for incident laser photon energies between 1.85 and 2.20 eV (670-564 nm), the region over which the films exhibited optical absorption associated with an electronic transition of the π-electrons on the conjugated backbone. The excitation profiles have been used to determine both the strength of the vibronic coupling and the differences in vibrational frequency between the ground and excited states. The results are in reasonable agreement with those obtained previously for polydiacetylene single crystals.     

Cross-sectional hydrogen content and mass density profiles of diamond-like carbon film by neutron and X-ray reflectivity

The cross-sectional profiles of hydrogen content and mass density of diamond-like carbon (DLC) film were investigated using X-ray and neutron reflectivity. DLC films were prepared using a plasma CVD technique by varying the H₂/(H₂ + CH₄) ratio gas source from 0 to 0.9. The cross-sectional hydrogen content and mass density profiles of the films were calculated by neutron and X-ray reflectivity, and the results were compared with those from elastic recoil detection analysis (ERDA).The fitted simulation showed that the mass density gradually decreased with increasing depth, whereas the hydrogen content increased with depth. In both ERDA and reflectivity measurements, the average hydrogen content was more than 30% in all films and tended to increase with the H₂/(CH₄ + H₂) ratio. However, there was a difference in hydrogen content values between the two analyses ranging from 5.1 % to 8.5%.     

Study of oriented block copolymers films obtained by roll-casting

Roll-casting orientation of cylinder microphase separated poly(styrene-b-butadiene-b-styrene) triblock copolymers, was analyzed. The mechanical anisotropy of roll-cast films, defined as the ratio of Young's modulus obtained parallel and perpendicular to poly(styrene) cylinders, is similar for samples prepared using a dimensionless minimum gap between rolls higher than approximately 0.02. The orientation of samples was also characterized by measuring the full width at the half intensity maximum of small angle X-ray scattering intensity circle profiles and showed good correlation with modulus measurements. Blends of triblock and diblock with up to 60 wt[percnt] of diblock show orientation as good as the neat triblock sample.     

Fabrication and Structural Control of Fe/Ti Oxide Thin Films with Graded Compositional Profiles by Liquid Phase Deposition

Fe/Ti oxide films with graded composition profiles have been prepared from aqueous metal-fluoro complex solutions by the liquid phase deposition method. Films were deposited from a solution, in which the (NH₄)₂TiF₆ solution was added under a controlled flow rate into the FeOOH–NH₄F·HF solution. Transmission electron microscopy and X-ray microanalysis of the films revealed that the composition and graded profile of the deposited films in depth direction could be controlled by adjusting the mixing conditions of the reacting solution. Along with the change in composition, the microstructure of the films changes from microcrystalline β-FeOOH at the base to nanocrystalline anatase TiO₂ near the surface.