Papers by Keyword: Misfit

Abstract: By means of different cooling methods, microstructure observation and X-ray diffraction analysis, an investigation has been made into the influences of the cooling methods on the microstructure and lattice parameters of FGH95 superalloy. The results shown that, after the solution treated alloy is cooled at different mediums, fine γ′phase and carbide particles dispersedly distribute in the grain and coarser γ′phase discontinuously precipitates along grain boundaries. After X-ray diffraction analyzed, the γ and γ′phases in “molten salt cooling” alloy possess larger lattice parameters, and a bigger lattice misfit exists in the interface between the γ and γ′phases.

Abstract: Manufacturing resource planning (MRPII) system which is the core information system that supports the operations of manufacturing organization, are often failed to meet estimated benefits, impeding operational performance and strategic advantages, due to the misfit between the structure modeled in the system and the actual structure of manufacturing environment it intended to represent. Furthermore, disputations upon whether organizational adaptation is always superseding other misfit resolving strategies have increasingly exposed. Hence, this paper presents an operational framework – taxonomy model of MRPII misfit to be applied in a case study which involves three small and medium manufacturing organizations in Malaysia, with the purpose of systematically classify MRPII misfits, and subsequently to identify appropriate misfit resolving strategy (system modification or organization adaptation) based on the specificity of the misfit. The implications of each type of MRPII misfit have been discussed from the perspectives of degree of misfit severity, risk of the MRPII system, organizational discretion on structural change, and most importantly the misfit resolving strategy. In addition, the planned methodology of the case study is presented, in details of selection of case companies and data analysis method. The findings of this proposed study is expected to serve as general guidelines or basics that can be referred by adopting organization to build their resolving strategy, according to the specificity of MRPII misfit situation which they encountered.

Abstract: Interfacial dislocations are frequently observed to form during 4H-SiC epitaxy and thermal annealing. This report attempts to establish the correlation between the distribution of interfacial dislocations and the thermal stress induced by a radial temperature gradient. In addition, it is argued that they are misfit dislocations formed by the interaction between thermal strain and misfit strain.

Abstract: The influence of an external stress on the nucleation and growth of disk-shaped G.P. zones has been investigated for a Cu-1.2wt%Be-0.1wt%Co alloy aged at 220 °C. A compressive stress applied in the [001] direction during aging preferentially accelerates the nucleation and growth of the G.P. zones perpendicular to the [001] axis, whereas a tensile stress does not significantly affect those of G.P. zones. The promotion of the nucleation and growth of the G.P. zones perpendicular to the compressive-stress axis can be well understood through the interaction energy between the applied stress and the misfit strains of G.P. zones. The critical diameter of the disk-shaped G.P. zone nucleus was estimated as about 1.3 nm from evaluation of the interaction energy.

Abstract: Semiconductor nanostructures are interesting objects for many microelectronic and optoelectronic applications. Nevertheless, to use them, it is necessary to control their size, their density and their spatial distribution. In the last decade, many researches have been done to control these parameters. One of these researches is the elaboration of a functional substrate inducing a lateral self-organization of nanostructures. The organization driving force is the strain field induced on the surface by a buried dislocations network. The purpose of this work is the numerical resolution, in the case of anisotropic elasticity, of the problem of a misfit dislocation located between an infinite substrate and two-layer composite. The elastic fields of stresses are calculated for various orientations of the Burgers vector, by inversion of 30x30 arrays of linear equations. The composite NiSi2/Si / (001) GaAs, that made the object of several investigations, is treated like example.

Abstract: Epitaxial group-III nitride films, although in single crystalline form, contain still a large number of threading dislocations. These set limits to performance and lifetime of devices, notably to high power structures like lasers. The strategy in material development was and will be (at least until lattice-matched substrates become available) to reduce the dislocation densities. The present contribution elaborates on possible dislocation origination mechanisms that determine the population of dislocations in the epitaxial layers. These mechanisms can be controlled to a certain degree by proper deposition procedures. The achieved dislocation populations then determine the processes that can reduce the dislocation densities during growth of the epitaxial layers. The mutual annihilation of threading dislocations is rather efficient although affected by the glide properties of the growing epitaxial crystal and the thermal stresses during the cooling down after growth.