Oxide morphology

Fig. 3. Wedge test crack length as a function of maximum Cu buildup at the oxide-metal interface. The adhesive was Cytec FM-123. The surfaces were prepared with the Forest Products Laboratory etch. The oxide morphology was kept constant. Data are from Ref. 115].

Fig. 34. PAA aluminum surface covered with a thin layer of grease that masks the oxide morphology.

Review of Different Aspects of Aluminum Oxide Morphology... 

For galvanostatic anodization a first potential maximum is again observed at about 19 V, and the thickness of the anodic oxide at this maxima has been determined to be about 11 nm, as shown in Fig. 5.4. Note that these values correspond to an electric field strength of about 17 MV cm4. The first maximum may be followed by several more, as shown in Fig. 5.1c and d. Note that these pronounced maxima become smeared out or even disappear for an increase in anodization current density (Fig. 5.Id), a reduction in temperature (Fig. 5.1c), or an increase in electrolyte resistivity. The latter value is usually too large for organic electrolytes to observe any current maxima. A dependence of these maxima on crystal orientation [Le4] or doping kind and density [Pa9] is not observed. The rich structure of the anodization curves is interpreted as transition of the oxide morphology and is discussed in detail in the next section. 

Oxide Morphology, Chemical Composition and Electrical Properties I 83... 

Other models are based on electric breakdown of the oxide [Fo2, Chl2]. It is not clear whether this breakdown should be thought of in terms of an electronic or an ionic effect. However, in both cases breakdown may cause a degradation in the oxide morphology, which leads to an enhanced etch rate. An electric field strength in the order of 10 MV cm4, the observation of an electroluminescent burst associated with the current peak of the oscillation, and the presence of an electronic component in the interface current are in favor of this model [CalO, Chl2]. 

Substrate Characterization. Venables et al. (2.) have described the FPL oxide morphology using STEM In the SEM mode. Figure 1 Is an Isometric representation of the FPL surface. In contrast, the SAA process produces a much thicker oxide layer, Isometrlcally represented In Fig. 2. 

Fig. 15a and b. Perspective of the proposed (Venables et al.52) oxide morphology produced on aluminium by the a) FPL and b) PAA processes52. (Reprinted with permission from Chapman and Hall LTD.)... 

In a study to clarify the nitrogen effect [60] protective alumina scales were observed to form on TiAl (52 at% Al), exposed in Oz, up to 1000°C. However, the same exposures conducted in air resulted in the formation of Ti02-rich scales which grew at rates orders of magnitude faster than pure alumina scales and even trace amounts of N2 influenced the oxidation morphology, Fig. 16. The rate of oxidation increased continually as increasing amounts of N2 were added to pure 02 at 900 °C. The addition of... 

Fig. 31. Schematic diagram of the oxidation morphology and cracking observed in orthorhombic alloy/SiC composites (left) and the oxidation rates of the composites over the temperature range 500-900 °C (right).

Fig.33. Schematic diagrams of the development of the oxidation morphology on MoSt, at temperatures of 600°C and higher (top) and the temperature range around 500°C (bottom).

Fig.35. Oxidation morphology development for MoSi2 at 500°C with application of NaF (after Cockeram and Rapp).

Fig.37. Schematic diagram of the oxidation morphology developed 011 a MoSi,-HfB, composite ai 1200°C.

The oxidation morphology may be examined by a wide range of techniques depending on the particular type of information being sought. The following procedure... 

It is assumed that the reader is familiar with the techniques of optical microscopy. There are, however, a number of other specialized techniques, which are useful for examining various features of oxidation morphologies. These techniques mainly generate information from interactions between the specimen and an incident beam of electrons, photons, or ions. The basis for the various techniques will be described here. Examples of their application will be presented in subsequent chapters. 

The following is a brief description of the electron-optical and other specialized techniques, which may be used for examining oxidation morphologies, and the type of information which may be obtained from each technique. The reader is directed to the texts and reviews, referenced for each technique, for a more detailed description. 

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