Structural Dislocation

Recently, Lindoy and Adam and their coworkers conducted a series of investigations on cation discrimination by structural dislocation (Adam et al., 1983a, 1983b, 1986, 1987, 1988 Lindoy, 1989b). Structural dislocation is associated with a sudden change in the K value for cation-macrocycle interaction for a particular metal ion with a series of closely related macrocyclic ligands (Adam et al., 1983b, 1986). In one example, the interaction of 17-, 

and 19-membered dibenzo macrocycles (see 46 52) containing three nitrogen and two oxygen atoms in the ring with Cd and Zn + in 95% CH3OH was examined. The log K values of Cd with the 19-membered macrocycles were considerably lower than expected from the log K values for the 17- and 

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Fig. 12. Derivative curves of EPR in a highly dislocated As-doped germanium crystal grown in a H2 atmosphere. The magnetic field is oriented along the [100] direction. T= 2 K, /= 25.16 GHz. Note the sign reversal of the new lines as compared to the As-donor hyperfine structure. Dislocation density 2 x 104 cm 2. (Courtesy Pakulis and Jeffries, reprinted with permission from the American Physical Society, Pakulis, E.J., Jeffries, C D. Phys. Rev. Lett. (1981). 47, 1859.)...

The temperature increase leads to the release of the volatile components, that causes the formation of empty spots in the solid structure (dislocations). 

During the last decade, numerous reports have appeared of linear defects in GBs in metals observed by TEM. The observed variation in geometry as well as the variation of contrast for various diffracting conditions indicate that a single type of defect cannot account for all the observations. Among the numerous interpretations that have been suggested for the linear defects are (i) absorbed lattice dislocations (ii) steps, at least a few unit cells high, in the boundary plane (iii) structural dislocations in the boundary that accommodate small deviations from the special orien-... 

Streptomycin, 17 Strontium template, 94 Structural dislocations, 12 Sulfamide, 482, 483... 

Some zeolites possess sorption properties close to those of small-pore zeolites, even when they have pore openings exceeding 0.45 nm. This is due to blockage of pores by large cations or structural dislocations. Offretite, zeolite T, ZSM-34, and clinoptilolite belong to this category. 

U.S. intelligence reports of 1961 and 1962 vividly portrayed China s domestic crisis. Mao s ill-conceived development programs had failed dismally, causing not only massive structural dislocation in the economy. 

Thus, as indicated above, in the submicron-sized 3Y-TZP ceramic, the stress-induced cyclic hardening, due to transformation taking place, was higher than under static deformation. NanocrystaUine 3Y-TZP softened cyclically, due to the formation of a large number of microcracks. In the submicron structures, this observation basically reflects the effects of dislocations and dislocation-dislocation interactions. In the nanocrystalline 3Y-TZP ceramic, this greater ability to accommodate plastic strain is probably due to grain-boundary sliding, since in nanocrystalline structures dislocations cannot move, because shp distances are on an atomic scale (hke the dimensions of dislocations themselves). 

As mentioned, the solid electrolytes are sintered metal oxides with mobility of ions where the ionic conductivity is influenced by both the microstructure and geometry. The effects of composition, structure, microstructure, and strain on ionic transport at grain boundary provided complementary tools for futiu-e developments in solid electrolyte materials. Among these, a particular attention was given to the impact on ionic transport of defects in various types of structures, dislocations, grain boundaries, and heterostructure interfaces. The design of such structural properties also considered the achievements of the development in nanotechnologies. 

Apart from its function as a point defects trap, Ti diffuses towards structure dislocations to form Cottrell-type atmospheres that can block the restoration and the rise of the initial lattice. Weertman and Green [41] demonstrated that these dislocations, thus decorated by dense clusters of large solutes such as Ti, become neutral sinks that cause unbiased elimination of point defects and therefore an increase in the resistance to swelling. Furthermore, by screening dislocations from the arrival of point defects, these clusters are probably conducive to mutual recombinations close to the decorated dislocations which will also tend to increase the resistance to swelling ... 

A fraction of the Ti is in the form of fine TiC precipitates and in the presence of phosphorus, in the form of small M2P-type phosphide platelets (Fig. 8.15(b)). These phases can pin the structure dislocations and therefore block restoration of the initial cold working. Once again, they work very favorably on the resistance to swelling because they also act as defect sinks and recombination sites. 

Various defects occur in the sheared structures. Dislocation loops have already been mentioned. Twinning has been observed where the directions of shear planes change. There is also evidence for deviations from strict periodicity in the shear planes. Thus some shear structures have ranges in composition and it is easy to imagine a continuous structural change through such a phase region... 

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