Structure three-dimensional interphase

Much of what we need to know abont the thermodynamics of composites has been described in the previous sections. For example, if the composite matrix is composed of a metal, ceramic, or polymer, its phase stability behavior will be dictated by the free energy considerations of the preceding sections. Unary, binary, ternary, and even higher-order phase diagrams can be employed as appropriate to describe the phase behavior of both the reinforcement or matrix component of the composite system. At this level of discussion on composites, there is really only one topic that needs some further elaboration a thermodynamic description of the interphase. As we did back in Chapter 1, we will reserve the term interphase for a phase consisting of three-dimensional structure (e.g., with a characteristic thickness) and will use the term interface for a two-dimensional surface. Once this topic has been addressed, we will briefly describe how composite phase diagrams differ from those of the metal, ceramic, and polymer constituents that we have studied so far. 

Interphase inhibition [52] occurs where the inhibitive layer has a three-dimensional structure situated between the corroding metal and the electrolyte. The interphase layers generally consist of weakly soluble compounds such as oxides, hydroxides, carbonates, inhibitors, etc. and are considered to be porous. Non-porous three-dimensional layers are characteristic of passivated metals. The inhibitive efficiency depends on the properties of the three-dimensional layer, especially on porosity and stability. Interphase inhibition is generally encountered in neutral media, either in the presence or absence of oxygen. In aerated solutions, the inhibitor efficiency may be correlated with the reduction in the oxygen transport limited current at the metal surface. 

In Fig. 20 various optical sections are depicted from a neuron microinjected with Lucifer Yellow, which was located within a thick (>100 im) brain section. The various sections do not show much information, but when they are combined in a reconstruction as shown in Fig. 21, the three-dimensional nature of the structure becomes clear. Similar detailed images are observed for interphase nuclei which have been hybridized with FITC derivatized oligonucleotide probes. Figure 22 displays a reconstruction in which it is quite evident that two... 

Zeolites form another class of materials useful for fundamental studies . As mentioned earlier, zeolites are microporous silica-aluminates with micropores of dimensions comparable to organic molecules. The materials are unique, because these micropores are determined by the three-dimensional crystallographic structure of the material and catalytic events occur at the interphase of zeolite micropore and zeolite lattice. As a result the catalytically active sites are well defined. Zeolites are used in practice in the acidic form or promoted with metal or sulfide particles. High Resolution Electron Microscopy, Neutron Diffraction and Solid State NMR are techniques that arc applied for structural characterization and to study the behaviour of chemisorbed molecules. 

The term interface implies a two-dimensional structure. It is clear in nearly all practical cases in polymer science that the regions between phases are three-dimensional in nature. These regions are also often likely not to be isotropic, but of a compositionally graded nature which means they do not meet the strict definition of a phase. In this chapter, the terms interface and interphase will be used essentially interchangeably. 

In the case of a structural bond, a strong adhesive is of litde value unless the stresses can be transferred via the adhesive from one adherend to the other. The interface or interphase (a three-dimensional interfacial region with properties different from those of either material) between the adhesive and the adherend is critical to this stress transfer. The goal of a surface treatment is to form a strong and stable interface or interphase that is stronger and more durable than the adhesive being used so that joint failure is cohesive within the adhesive, both initially and throughout the joint s service lifetime. 

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