Morphology of the Separated Phases

The nucleating character of the different rare-earth fluorides is strongly different and dramatically affects the morphology of the separated phases. For instance, the respective 

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The reduction is combined with a chemical vapor transport of tungsten via the volatile W02(0H)2. The morphology of the solid phases changes significantly. The reaction can be separated into three sequential stages ... 

The morphology of blends may be complex. The addition of compatibilizer not only affects the size and shape of the separated phases (the macromorphology), but it may also affect the crystalline form, the size of crystalline entities, as well as the total crystallinity (the micromorphology). In a blend of two semicrystalline polymers, e.g., PE/PP, four phases may coexist ... 

Despite of the fact that the morphology of the separating systems of two kinds may not differ essentially, the phase identification of the kind of transition is absolutely necessary to control the system structure with the aim of optimizing the technology of making polymer materials and improving their service properties. 

Phase separation in bulk mixtures commonly leads to an isotropic, disordered morphology of the coexisting phases [34]. The presence of a surface can significantly alter the phase-separation process, however [35,36]. 

Mechanical properties of mbber-modifted epoxy resins depend on the extent of mbber-phase separation and on the morphological features of the mbber phase. Dissolved mbber causes plastic deformation and necking at low strains, but does not result in impact toughening. The presence of mbber particles is a necessary but not sufficient condition for achieving impact resistance. Optimum properties are obtained with materials comprising both dissolved and phase-separated mbber (305). 

Consequently, interpenetrating phase-separated D/A network composites, i.e. bulk heterojunction , would appear to be ideal photovoltaic materials [5]. By controlling the morphology of the phase separation into an interpenetrating network, one can achieve a high interfacial area within a bulk material. Since any point in the composite is within a few nanometers of a D/A interface, such a composite is a bulk D/A heterojunction material. If the network in a device is bicontinuous, as shown in Figure 15-26, the collection efficiency can be equally efficient. 

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