In this article, some views on the nature of incoherent interphase interfaces, and their role in the nucleation and growth
processes governing the evolution of microstructure in solid-state diffusional transformations (reconstructive transformations),
are explored. It is argued that essentially incoherent interfaces can be involved in the initiation and propagation of polymorphic
transformations and massive transformations as well as in various precipitation phenomena in metallic and ceramic systems.
Similar views have already been advanced earlier in connection with studies of massive transformations. Faceting along the
interphase interface during nucleation and growth can derive from thermodynamic, kinetic, and crystallographic factors independent
of the bicrystallography of the conjugate phases. This idiomorphic behavior can be relevant to both intergranular and intragranular
phase formation. The concept of one-dimensional (1-D) commensuration of phases through plane edge-to-edge/row matching is
an interesting extension of the classic ideas of coherency and bicrystallography and potentially important in characterizing
the behavior of certain types of boundaries. However, the general importance of these geometrical relations in real and reciprocal
space will depend on the depth of the energy wells in orientation space associated with these special boundaries.
This article is based on a presentation made in the “Hume-Rothery Symposium on Structure and Diffusional Growth Mechanisms
of Irrational Interphase Boundaries,” which occurred during the TMS Winter meeting, March 15–17, 2004, in Charlotte, NC, under
the auspices of the TMS Alloy Phases Committee and the co-sponsorship of the TMS-ASM Phase Transformations Committee. 相似文献
Our earlier experimental studies of the solid-phase reduction of disseminated lump ores demonstrate that an oxide lattice transforms into a metal lattice via the saturation of the oxide crystal lattice by charged oxygen vacancies. Low-charge metal cations appear in the oxide crystal lattice, and they are related to oxygen vacancies by the condition of local electrical neutrality. As oxygen vacancies are accumulated (i.e., during reduction), the number of oxygen vacancy-low charge cation complexes in the initial oxide increases. The total composition of the oxide phase in the range of a crystal lattice of a certain type changes continuously from the initial oxide to the end product of reduction, i.e., to the lower oxide or a metal. Therefore, it is necessary to determine the thermal characteristics of not only all possible stoichiometric compounds in the M-O system but also MOx oxides of variable compositions. Equations for calculating the standard heat capacities of complex stoichiometric oxides and oxides of variable compositions in the Fe-O-Ti system are derived using a mathematical model developed earlier, and these characteristics are calculated. 相似文献
A technology for the synthesis of synthetic minerals (using the example of spinels) using a low-temperature plasma flame is developed. The diagnostic properties of spinels are identified. 相似文献
From the technical and economic points of view, systems integration, and packaging represent a crucial step in the production of microsystems. Compared to purely silicon- or glass-based systems, the variety of materials and geometries available for purely polymer microfluidic systems is much larger, due to the outstanding material properties. Moreover, polymers may be shaped and joined by comparably simple methods. Examples are polymer microreplication as well as various bonding methods. With them, complete polymer microsystems can be integrated. In addition, a number of established, compatible processes are available for the integration of functional elements that may also be made of other materials.
Methods for finding the parameters (energies and capture coefficients for electrons and holes) of the levels involved in the formation of the recombination flux are suggested. The temperature variation of these parameters for AlGaN/InGaN/GaN and InGaN/SiC structures is discussed. The parameters of the levels responsible for tunneling recombination are determined. 相似文献
Magnetic fluids are now widely used to implement transducer architectures. These fluids have valuable properties compared to traditional materials. In this column, a brief overview of magnetic fluids and their traditional uses in the field of transducers are given and some applications developed at the DIEES laboratory at the University of Catania, Italy are presented 相似文献