Aluminum substrate, oxide-covered

The present study was initiated to provide a direct comparison of IETS and IR spectra for an identical molecule adsorbed on an aluminum oxide covered, evaporated aluminum substrate. Further, it was of interest to see if a weakly acidic C-H bond, such as that present in 1,3-dialkanediones, would show dissociative chemisorption similar to the well-known chemisorptions of Bronsted acids containing acidic O-H bonds (see above). The molecules chosen for this study were acetic acid and 2,4-pentanedione. Both oxide covered copper and aluminum were used as substrates in order to see the effects of substrate oxide on the chemisorption spectra. 

Recently, Giza et al. showed that the increase of surface hydroxyls on oxide-covered aluminum by water plasmas substantially increased the kinetics of chemical binding of organophosphonic acids to the substrate [113]. 

Although the above experiments involved exposure to the environment of unbonded surfaees, the same proeess oeeurs for buried interfaces within an adhesive bond. This was first demonstrated by using electrochemical impedance spectroscopy (EIS) on an adhesive-covered FPL aluminum adherend immersed in hot water for several months [46]. EIS, which is commonly used to study paint degradation and substrate corrosion [47,48], showed absorption of moisture by the epoxy adhesive and subsequent hydration of the underlying aluminum oxide after 100 days (Fig. 10). After 175 days, aluminum hydroxide had erupted through the adhesive. 

Table 10 presents the parameters of various metallic substrates. It can be seen that the most appropriate are those made of aluminum covered by anodic oxides. 

This model may possibly be adapted to metal-water thermal explosions if one assumes that there are reactions between the molten metal and water (and substrate) that form a soluble salt bridge across the interface between the two liquids. This salt solution would then be the material which could superheat and, when finally nucleated, would initiate the thermal explosion. As noted, the model rests on the premise that there are chemical reactions which occur very quickly between metal and water to form soluble products. There is experimental evidence of some reactions taking place, but the exact nature of these is not known. Perhaps, in the case of aluminum, the hydroxide or hydrated oxides form. With substrates covered by rust or an inorganic salt [e.g., Ca(OH)2], these too could play an important role in forming a salt solution. 

The schematic design of a polymer solar cell is displayed in Fig. 8 the photoactive layer is usually sandwiched between an indium tin oxide (ITO)-covered substrate (glass or plastic) and a reflective aluminum back electrode. As the ITO substrate is transparent, illumination takes place from this side... 

It is also vital that a constant supply of aluminum is guaranteed through the diffusion from the substrate in order to ensure the surface is totally covered with alumina. Otherwise Cr203 and Fe-Cr spinel would be obtained mainly. The addition of the already mentioned RE in contents of less than 0.1% increase the resistance to oxidation of the Fe-Cr-Al alloys. Moreover the alumina grains are reduced in size. 

The rate of electron transfer reactions (ETRs) is strongly influenced by the surface composition of the metal. As most materials are covered by oxides, their electronic properties will determine the rate of ETR. Therefore, metals that are covered by electron conducting or semiconducting oxides such as iron or zinc will show a higher ETR rate at the substrate-polymer interface in comparison to materials that form highly insulating oxides such as aluminum. 

Originally, a donor-acceptor bilayer device of two films was used as an n-p junction in solar cells. Thus, they were fabricated as sandwich structures. An example would be one where a transparent substrate is first coated with a conductor, like indium-tin oxide. A conducting polymer like, poly (ethylene dioxythiphene), doped with polystyrene-sulfonic acid, would then be applied from and aqueous solution. The indium-tin oxide acts as an electrode for hole injection or extraction. The polymer is then covered with a conductor, an aluminum foil. The doped polymer can be illustrated as follows ... 

Metal monoliths were obtained from Emitec (Germany). They were subjected to high-temperature treatment by the supplier. The cell density of the monoliths used is approximately 4(X) cpsi. The monoliths consist of an iron-chrome-aluminum alloy which provides the surface with a textured whisker structure after suitable treatment. These whiskers, shown in Figure 8, act as anchors for the washcoat when deposited onto the substrate. Tbe whiskers consist of aluminum oxide, completely covering the metal surface. This is shown by the data in Table 2, giving the results of EDX and XPS analyses of the whiskers-covered metal surface. 

Fig. 30.20 Construction of the PLED Glass substrate/ transparent electrode indium-tin oxide (lTO)/hole transport layer (HTL)/active layer (parahexaphenyl PHP)/electron transport layer (ETL)/aluminum (Al). The blue PHP electroluminescence emission light is converted by covering the PHP OLED with a green dye layer (to give a green emission color) and a red dye layer together with a suitable dielectric filter (to give a red emission color).

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