Film gradation

An interesting question that arises is what happens when a thick adsorbed film (such as reported at for various liquids on glass [144] and for water on pyrolytic carbon [135]) is layered over with bulk liquid. That is, if the solid is immersed in the liquid adsorbate, is the same distinct and relatively thick interfacial film still present, forming some kind of discontinuity or interface with bulk liquid, or is there now a smooth gradation in properties from the surface to the bulk region This type of question seems not to have been studied, although the answer should be of importance in fluid flow problems and in formulating better models for adsorption phenomena from solution (see Section XI-1). 

In this section, a visual and colorimetric NH4+ sensing film was described. The observed color gradation was suitable for human visual perception over a wide dynamic range. This NH4+ sensing film is useful for routine semiquantification of NH4+. 

The degraded film specimens often impart an iridescent color. This effect may be attributed to the interference of visible light due to diffused reflection between the protuberances formed on the surface of the films, which is interpretable in terms of a thin-layered gradation of the refractive index near the film surface. 

The linear part in which the film is used. The steepness of the curve is the gradation (hard films with strong contrast have steep curves). The slope is related to the grain size. 

Possibly the most convenient direct route to polyacetylene, namely the polymerisation of cyclooctatetraene (COT), was introduced by Grubbs and co-workers [4], They initially showed that polyacetylene can be obtained via ROMP of COT using the very active Schrock type tungsten hexafluoro-t-butoxide initiator W(=CHR)(OC(Cp3)2 CH3 )2(=NAr). A freestanding film was obtained when the monomer was polymerised as the neat liquid. A random copolymer was obtained from the polymerisation of a mixture of COT and 1,5-cyclooctadiene (COD) and, as expected, a gradation in colour and Raman shift showed that the conjugation length of the polyene sequences increased with COT... 

It was seen in Section 2.4 that through-thickness variation in properties can significantly modify the in-plane normal stress. However, compositional gradation does not markedly alter the propensity for curvature bifurcation compared to that seen in a film-substrate system comprising homogeneous layers (Finot and Suresh 1996). 

The features of deformation of the fihn ubstrate system observed here are indicative of the deformation modes which can be observed. Although the range of parameter space which has been considered in detail is quite limited, any departure from a uniformly strained layer can be taken into account through the net membrane force in the film in most cases provided that the film is thin compared to the substrate. Other modes of deformation may be found by considering noncircular substrates, materials with different moduli, films with gradation in mismatch strain for properties, and other possibilities. 

Examples of material systems within this category include a uniformly strained layer covered or capped with an unstrained layer of uniform thickness, a film in which the mismatch with respect to the substrate varies continuously across the thickness due to compositional gradation, and a film which comprises a periodic arrangement of many thin layers of alternating mismatch strain, a so-called strained superlattice structure. Conditions for dislocation formation in such structures are examined in this section. 

It was necessary to secure a suitable on-/off-voltage difference (margin) in those multiline displays and the PI alignment film stabilized the low inclination angle of liquid crystal molecules. After that, thin-film transistor electrodes were developed that enable minute gradation of the pixels. Color filters attached on the opposite electrode enabled large screen flat-panel color TVs were realized. But stUl, it is the polyimide alignment film on both electrodes that could achieve the stable orientation of the LC molecules. 

A unique chemical polymerization technique for CP composites is solution evaporative polymerization. To cite an example, Han et al. [III.45] took a solution of FeCl3 (the oxidant) and PVA (the host polymer) in methanol, then added pyrrole monomer thereto. The oxidation potential of the solution, and hence the polymerization, could be changed and controlled via the proportion of FeClj to PVA as well as via evaporation of the solvent, and was optimally ca. +500 mV vs. SCE. Thus, simple casting of a film from this solution yielded P(Py) composite. The percolation threshold, for a saturation conductivity of ca. 10 S/cm, was claimed to be very sharp, at 5 w/w%. A method which appears to be a combination of solution evaporative polymerization and monomer-sorption polymerization is that carried out by Morita et al. [344] A P(Py)/PMMA composite, with nonhomogenous composition (a gradation of PMMA and P(Py) concentrations) was obtained in 0.1 to 10 pm thickness and 10 to 10 S/cm conductivity from combination of 2-butanone solutions of pyrrole, PMMA and benzoic acid with aqueous solutions of potassium persulfate. 

Buffer layer (cleaning, etching) An interfacial layer of material that has properties or crystal structure, intermediate between the film and the substrate materials, and allows the gradation of properties between the two materials. See also Compliant layer. 

Diffusion-type interface (film formation) When the interfacial material (interphase material), formed during the deposition of A onto B along with subsequent diffusion, consists of an alloy of A and B with a gradation in composition. See also Interface Interphase material Kirkendall porosity. 

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