Effective domains, textures

Meanwhile, in domain-rich ferroelectric devices, besides the need for a direct visualization of internal residual stresses, a direct experimental assessment of domain texture and distribution is desirable, in order to control functional outputs. For example, a size effect on the ferroelectric phase transition in thin films may lead to a critical size of few tens of nanometers, below which the ferroelectric transition vanishes. 

The domain structure and crystalline texture of AB and ABA type block copolymers of ethylene oxide (EO) and isoprene (Is) are studied, and the effects of the casting solvents and the fractional compositions of each block segment are determined. The domain structures of EO-Is copolymers are essentially identical to those of EO-Is-EO copolymers, but they strongly depend on the fractional compositions and the casting solvents. The role of casting solvent in the different domain formation mechanisms is interpreted in terms of an interrelation of two binodal surfaces that represent the critical concentration for crystallization of the EO segment and the critical concentration for micelle formation of the incompatible EO and Is segments. 

Breeze Additives. Optical microscopy of the Six Bells (CR 301a), Cortonwood (CR 401) and Maltby (CR 502) cokes with the A170 pitch coke breeze additives shows that the breeze additives with predominantly flow domain anisotropy optical texture are easily distinguishable from the surrounding coal coke of predominantly fine-grained mosaics. The effect of carbonization to 1200 K upon the petroleum coke breeze is to increase progressively the number and size of fissures within the breeze particles. 

Practical polymer processing operations, such as extrusion and injection, are complex processes highly dependent on the conditions of shear, extensional stress and temperature. It has now been realized that shear stress and extensional stress have different effects on the orientation of PLGs. Nematic PLCs have a polydomain texture and each domain consists of mesogens with the same local orientation. The directions of these domains are randomly aligned while in a quiescent state. Only if a stress is applied are the domains oriented in one direction. As Ide and Ophir [6] and Viola et ah [7] have pointed out, shear stress is related to rotational motion (torque), and its application will result in a tumbling flow of PLC domains. Only once the shear stress has reached a critical value will it break down the domains and lead to a uniform molecular orientation. In contrast, extensional stress tends to orient the domains in one direction without breaking down the domains even if the stress is low. Viola et ah [7] also considered that shear flow induces sheet-like textures while extensional flow induces fiber-like textures. Therefore there will be differences in the hierarchical and fibrillar structures acquired in different fibrication processes. 

The first section details the purely intrinsic response of ferroelectrics and discusses their anisotropic properties, the useful application of which can be controlled by the correct orientation of a sin e crystal or by texturing a polycrystalline material. Attention is then focused on one of the most significant extrinsic contributions to the polarization response of ferroelectrics, namely the motion of domain walls. The effect of the domain wall contribution can be controlled by the hardening-softening of... 

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