Thesis--University of Florida. / Description based on print version record. Manuscript copy. Vita. Bibliography: leaves 126-127.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 56-57). Also available on the World Wide Web.

Single crystals of cobalt have been deformed in tension over the temperature range 20°C to 600°C. On heating a transformation from the hexagonal close packed (hep) structure to the face centred cubic (fee) structure occurs at 430°C. The deformation behaviour in the hep phase has been compared to that for other hep metals, and it has been shown that only basal slip occurs even in unfavourable orientations. Twinning may occur, but has not been found to be associated with an increase in the work hardening rate. Similarly the properties in the fee phase have been compared to those of fee metals. The effect of deformation on the transformation has been studied on specimens which have been thermally cycled through the transformation during tensile tests. It has been found that the (111)/ (0001) transformation habit plane may be controlled by deformation. Recrystallisation may occur if two slip systems operate, but this is a function of crystal orientation. Slip may be induced on an unfavourably orientated glide plane in the fee phase, and this indicates that deformation dislocations on the (0001)[subscript: h], /(111)[subscript: c] plane are not affected by the transformation. However, glide dislocations on any {111} plane, which does not form the basal plane on cooling do not affect the work hardening behaviour in the hep phase. In previously deformed specimens, the flow stress is a function only of the deformation history, i.e. the yield point in the hep phase may be raised by a factor of 10 or the yield point in the fee phase may be lowered by a factor of 3. However, the work hardening rate depends only on the crystal structure and is always higher (by 20 to 100 times) in the fee phase than in the hep phase. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The recovery of mechanical properties following deformation of single crystal cadmium has been studied. Such recovery has been observed above 0.26 TM [subscript omitted] (-120°C). Crystals covering a range of orientation were deformed in tension at -196°C and recovered at elevated temperatures. Transmission electron microscopy to relate tensile and recovery behaviour to dislocation structures was found to be impossible. It was observed that work hardening during the initial portion of the easy glide region is completely recoverable. At higher strains in easy glide, a portion of the work hardening was not recoverable. It is believed that in this latter section, dislocations are generated on the second order pyramidal system {1122} <1123>. These dislocations will combine with basal dislocations to form stable obstacles in the lattice which will be responsible for the non-recoverable work hardening. The end of easy glide was found to occur at x = 20°, independent of recovery or initial orientation. This phenomenon is associated with flow on the second order pyramidal system which will produce a much higher density of obstacles at this point, resulting in a higher work hardening rate. Recovery in stage II was observed to increase the amount of strain attainable. It was also observed that while recovery up to intermediate strains in stage II affected only basal dislocations, both basal and pyramidal dislocations appear to be recovered at high strains. Pyramidal dislocations may recover by the processes observed by Price. The rate controlling mechanism for yield and flow of cadmium single crystals is thought to be one of the non-conservative motion of jogs. An attempt was made to calculate an activation energy for the recovery process, but the data did not yield any meaningful numbers. This may be a result of the definition of recovery adopted for this work. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The microwave dielectric constant and conductivity of MEM(TCNQ)₂ were studied in the neighbourhood of the monomer to dimer transition at 61°C using cavity-perturbation techniques at 9 GHz. The conductivity was found to be in general agreement with four-probe d.c. results. Thus, doubts about the reliability of the d.c. measurements above the destructive transition have been removed. The complex dielectric constant of TTF-TCNQ at liquid helium temperatures was studied using dielectric resonance techniques. Some anomalies regarding the interpretation of the dielectric resonance mode plots were resolved. Values for Є’ of (3.0±0.4)X10³ and for Є’of greater than 9 were implied by the results. Finally, preliminary results and proposed directions for a bolometric absorption measurement in TTF-TCNQ in the microwave bands are presented. This technique may prove useful for the direct observation of the pinned charge density wave in TTF-TCNQ. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Thesis (Ph.D.)--Kent State University, 2007. / Title from PDF t.p. (viewed Nov. 21, 2007). Advisor: Robert J Twieg. Keywords: phenylpyridine LCs, thiophene-pyridine LCs, pyridinyl stannanes, selective Negishi coupling, liquid crystal semiconductors, smectic liquid crystals. Includes bibliographical references (p. 356-363).

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