Details microstructure

Until the early 1970s, the absence of suitable techniques for probing the detailed microstructure of polymers or for examining the selectivity and rates of radical reactions prevented the traditional view front being seriously questioned. In more recent times, it has been established that radical reactions, more often than not, are under kinetic rather than thermodynamic control and the preponderance of... 

Establishment of the detailed microstructure of PVC has attracted considerable interest. This has been spurred by the desire to rationalize the poor thermal stability of the polymer (Chapter 1). Many reviews have appeared on the chemical microstruclure of PVC and the mechanisms of defect group formation.56 60... 

Subsequent studies of the physical properties of this series of E-V copolymers obtained via the (n-Bu)3SnH reduction of PVC have revealed that their properties, both in the solid state and in solution, are sensitive to their detailed microstructure (7-10). These observations prompted the present study concerning the mechanisms of the reductive dechlorination of PVC with (n-Bu)3SnH. 

The physical properties (7-10) of our E-V copolymers are sensitive to their microstructures. Both solution (Kerr effect or electrical birefringence) and solid-state (crystallinity, glass-transitions, blend compatibility, etc.) properties depend on the detailed microstructures of E-V copolymers, such as comonomer and stereosequence distribution. I3C NMR analysis (2) of E-V copolymers yields microstructural information up to and including the comonomer triad level. However, properties such as crystallinity depend on E-V microstructure on a scale larger than comonomer triads. 

The earliest models of fuel-cell catalyst layers are microscopic, single-pore models, because these models are amenable to analytic solutions. The original models were done for phosphoric-acid fuel cells. In these systems, the catalyst layer contains Teflon-coated pores for gas diffusion, with the rest of the electrode being flooded with the liquid electrolyte. The single-pore models, like all microscopic models, require a somewhat detailed microstructure of the layers. Hence, effective values for such parameters as diffusivity and conductivity are not used, since they involve averaging over the microstructure. 

The kinetics of formation of this zirconium diboride platelet reinforced zirconium carbide have been discussed, as have possible formation mechanisms [36] and detailed microstructural and orientation relationships between the phases [37]. These materials, in addition to being very refractory, are quite hard. Potential applications typically involve wear resistance, either at low to moderate temperatures or for short times at very high temperatures, such as in biomedical and rocket nozzle or rocket motor application [35]. 

Detailed microstructural investigation [12] revealed enhanced precipitation of Nd-rich phases at the SiC/matrix interfaces in the QE 22 -SiC composite after T6 heat treatment and during creep (Fig. 9). Such precipitation can detrimentally affect the creep behavior in a similar way as to fiber-reinforced composites. Further, Moll et al. [11] have proposed that poor creep resistance of the QE 22-SiC composite may be explained by taking into account interfacial sliding as an additional creep mechanism... 

The multiplet and multiplet-clustering analysis methods have been used to resolve the detailed microstructure of the seismic line which appeared at the early stage of the stimulation. The microstructure consists of the sub parallel multiplet planes. This result suggests that natural joints which are oriented to the directions most easy to slip, were stimulated by the injection. Because the structure developed stepwise corresponding to the... 

Thin films of the 1-2-3 superconductor were prepared on zirconla and alumina substrates by adding ca. 10% solutions of the citric acld/ethylene glycol precursor to the surface of the substrate followed by drying and pyrolysis in oxygen to 950 C. XRD patterns indicate that the 1-2-3 orthorhombic phase is the only crystalline phase formed under these conditions. Detailed microstructural and physical property studies of these films are in progress. 

Collins has reported the synthesis of a related class of metallocenes (43), some of which form elastomeric, stereoblock polypropylene when activated by The elastomeric properties of the polymer formed using 43 (M = Hf, X = SiMe2 7)xn = 25 °C) were far superior to those formed by the other metallocenes in the study. The polymers made using 42 and 43 have similar microstructures, as well as physical and mechanical properties. However, after detailed microstructural analysis of the polymer the authors proposed an alternate mechanism of stereocontrol to Chien s site epimerization model (Scheme... 

Both PNIPAAm and PVME exhibit unique thermo-shrinking properties. Thus, as an aqueous solution is heated beyond a certain point, the polymer shrinks and a phase separation occurs. This temperature is commonly referred to as the lower critical solution temperature (LCST). For PNIPAAm, it lies between ca. 30 and 35°C, the exact temperature being a function of the detailed microstructure of the macromolecule. Below LCST, the polymer is soluble in the aqueous phase, as the chains are extended and surrounded by water molecules. Above the LCST, the polymer becomes insoluble and phase separation occurs. Because of the abrupt nature of these transitions and their reversibility (which allows repeated thermal switching) these polymers have stirred up particular interest in the field of science and engineering since their first appearance in the open literature in 1956. 

The function h r, r ) accounts for the possibility that due to hysteresis effects, the interface does not advance completely to pores with capillary radius with increasing S, it depends on the detailed topology of the pore space and, thus, demands more detailed microstructure characterization. T is a factor of order 1, depending on pore geometry and wetting properties. 

Joos, J., Carraro, T., Weber, A. Ivers-Tiffee, E. Reconstruction of porous electrodes by FIB/SEM for detailed microstructure modeling. Journal of Power Sources, doi 10.1016/j.jpowsour.2010.10.006 (2010). 

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