Orientation and morphology

In conclusion, it must be emphasized that although it is convenient for the purpose of constructing models to assume a composite that comprises distinct crystalline and non-crystalline components, on the molecular level a gradual transition must occur, extending over a number of monomer units, between the well-orientated and ordered crystallites and the bulk of the remaining material. 

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Amongst the factors that will influence service performance are the effect of additives and impurities, temperature, detailed geometric size and shape, orientation and morphology, surface condition, energy and speed of any impacting blow, the shape of the impacting instrument, the environment, and strains in the article due to external loads. For this reason it is desirable, but not always feasible, to test prototype articles under conditions as close to service conditions as possible. 

However, the derived value for Ei is usually termed the activation energy E and may contain other contributions in addition to the intrinsic Ei value, such as those arising from the orientation and morphology of the sample. For this reason E is most commonly used. In the case of polycrystalline thin hlms, grain boundaries may have a dominant effect, as will be discussed in Section 6.4, where examples of intrinsically metallic materials behaving as semiconductors will be given. 

The main purpose of the work was to obtain more specific data on orientation and morphology features of the micro- and nanosurfaces emerging under vertices of the right comers of the mask (square-shaped) fabricated on Si (001) when etched in aqueous KOH solutions of various concentrations at various temperatures and mask alignments. 

Figure 5.14. Diagram of a-parameter curves, uniaxial film orientation, and morphology.

The microstructure (texture, orientation) and morphology of diamond films can be controlled by varying the growth parameter a (a=(vioq/vj j j) ), which depends primarily on gas composition and substrate temperature. For fiber-textured films, at low CH4 concentrations and increasing substrate temperatures (a < 1.5), the films exhibit pronounced <110> texture at medium CH4 concentrations and substrate temperatures (1.5 < a < 3), a transition of the fiber axis from <110> to <100> occurs a further increase in CH4 concentrations or decrease in substrate temperatures (a > 3) leads to fine-grained, non-faceted films. 

In solution-deposited fihns on dielectrics, the crystalline orientation and morphology depend considerably on polymer-substrate interaction, which can be controlled by modification of the dielectric surface with a self-assembled monolayer (SAM). Cho et al. have controlled the intermolecnlar interaction at the interface between HT-PHT and the dielectric substrate by using SAMs functionalized with various groups (-NH2, -OH, and -CH3) [24]. They have found that, depending on the properties of substrate surface, HT-PHT nanocrystals in the spin-cast films adopt two different orientations of 7t-conjugated planes — parallel and perpendicular to the substrates. These have field-effect mobilities that differ by more than a factor of four and are as high as 0.28 cm V s for jt-conjugated planes parallel to the substrates. 

The orientation and morphology of thermotropic LCP parts are strongly dependent on the process conditions near the melt temperature because of the inherent molecular anisotropy and very long relaxation times. Random coil thermoplastic polymers are much less dependent on processing history near the melt temperature, and orientation requires a secondary step such... 

For optimum toughening by crack deflection Telle et al. [145] pointed out that geometric factors like grain size, volume fraction, orientation and morphology of the added or in situ grown phases as well as the grain boundary strength have to... 

The shear stress growth on the inception of shear flow may reflect the orientation of the liquid crystalline domains. Orientation seems to occur within less than 2 strain units in shear flow. This primary normal stress difference can exhibit different phenomena from the shear stress response. In particular for the 60 mole % PHB/PET system, values of N are positive and rise gradually to the equilibrium values whereas the 80 mole % PHB/PET system can exhibit negative values of N. Ericksen s transversely isotropic fluid theory can qualitatively handle some of the observed phenomena. Further studies which couple the transient flow behavior to the orientation and morphology need to be carried out. 

The first extensive SEM investigation of PA6/PET-based MFCs and their precursors performed by Evstatiev et al. [82] undoubtedly showed the fibrillar structure of the PET reinforcements preserved after the PA6 matrix isotropization. Since then, electron microscopy has been used to visualize the orientation and morphology of the matrix and reinforcing components in almost every report on MFCs. It is worth noting some more recent studies on MFCs comprising LDPE and PET as matrix and reinforcement, respectively [30,31]. Several microscopic techniques were used, e.g., SEM, polarizing light microscopy (PLM) and TEM. Thus, by SEM it was demonstrated that the isotropic LDPE matrix embedded PET microfibrils with random orientation. Thin slices of PLM and TEM showed the orientation in the machine direction. The latter method also revealed the formation of transcrystalline layers of LDPE on the oriented PET microfibrils. 

Sec. 9.4] Crystal orientation and morphology of poly crystalline deposits 311... 

Temperature. The deposition temperature influences the structure, orientation, and morphology of vacuum-evaporated sexithiophene films. A high degree of orientation can be achieved even in films several micrometers thick deposited above 190 °C. The field effect mobility is enhanced for deposition temperatures close to the melting temperature (290 °C), which is associated with a suitable orientation, sometimes a favorable crystalline structure, and coalescent lamellae morphology [658]. 

Visintin A, CanuUo JC, Triaca WE, Arvia AJ. Changes in real siurface area, crystallographic orientation and morphology of platinum electrodes caused by periodic potential treatments phenomenological approach. J Electroanal Chem 1988 239 67-89. 

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