Composite/inhomogeneous film

NH groups left available for further interaction with PSS. The transfer was very poor in both cases and resulted in inhomogeneously coloured films. However, the simple alternation of TB and PAA yields much better quality films although still patchy. Further work in this direction is underway. We hope to produce composite PESA films containing different pairs enzyme/indicator for the development of optical enzyme sensor-array in near future. 

Due to the compositional inhomogeneity, it has been found that applying a significant bias on the electrode can induce changes in the resistance of a LSCF film decreasing the resistance by a cathodic treatment and vice versa increasing the resistance by an anodic treatment. XPS (X-ray photoelectron spectroscopy) measurements showed that the changes in resistance were correlated with the surfece composition of Sr. The cathodic treatment increases the Sr surface composition and decreases the resistance and vice versa for an anodic treatment [41]. 

Because the cast films are relatively thin, the optical density of the light absorbing species can he low and can vary with time of exposure. Additionally, the depth penetration of the absorbed light can be inhomogeneous in some systems. However, thin films can be mounted directly in UV/visible or infrared spectrometers, and so the course of the photopolymerization (and the rate) can be monitored directly in some systems. The most common observation made is the disappearance of monomer (e.g., loss of double bond absorption in the IR) as a function of irradiation time. It must be emphasized that in most thin film compositions important industrially, the monomers used are multifunctional. The polymer which results is then highly cross-linked and simple kinetic arguments are usually not valid. 

We conclude that the microscopic etch mechanism must be the same for single crystals and sputter deposited, polycrystalline ZnO Al. For the latter, the tendency for crater formation is masked by inhomogeneous chemical or physical properties like porosity, composition or, in case of dynamic deposition, multilayered ZnO Al films. This multilayer structure results from the fact that structural properties of ZnO Al deposited by a sputter process varies depending on the position of the film relative to the race track of the sputter target [131,132]. This dependence is important for the etch rate of in-line sputter deposited films [133]. 

Figure 4. Inhomogeneity of silica-aluminas prepared by various methods. A series of 17 commercial samples of silica-aluminas from seven different producers was submitted to microanalysis. All of them showed considerable fluctuations of composition at the scale of several tens of nanometers to several micrometers. These samples were prepared by coprecipitation or by the sol-gel method. It is not known whether some of these samples were prepared from alkoxides. Smaller but significant fluctuations at the micrometer scale were also observed for two laboratory samples prepared from alkoxides. The samples were dispersed in water with an ultrasonic vibrator. A drop of the resulting suspension was deposited on a thin carbon film supported on a standard copper grid. After drying, the samples were observed and analyzed by transmission electron microscopy (TEM) on a JEOL-JEM 100C TEMSCAN equiped with a KEVEX energy dispersive spectrometer for electron probe microanalysis (EPM A). The accelerating potential used was 100 kV.

Materials Analysis. The next level of complexity involves the measurement of dielectric properties for the determination of composition and microstructure as well as thicknesses. Thin films are typically microscopically inhomogeneous with substantial fractions of grain boundaries and voids, so their dielectric properties are rarely equal to those of the corresponding materials in bulk form. As an example, the pseudodielactric function <(> film deposited by low pressure... 

The analysis of the obtained data shows that the optimal content of rubber in the composition is from 8.5 to 10.5 mass%. Rubber content of less than 8.5 mass% causes discontinuance of the film structure of the polymeric matrix and pore formation, while more than 10.5 mass% provides an unstable inhomogeneous structure of the mixture during formation. 

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