Coherency Strain Energy in any Crystal System: Applications to in Situ Observations of Cigm in Calcite

1990 ◽  
Vol 205 ◽  
Author(s):  
R.S. May ◽  
B. Evans
Keyword(s):  
Driving Force ◽  
Migration Rate ◽  
Strain Energy ◽  
Solute Concentration ◽  
Coherency Strain ◽  
Solute Diffusion ◽  
Boundary Orientation ◽  
In Situ Observations ◽  
And Migration

AbstractIn situ observations of CIGM in CaCO3 bicrystals with a SrCO3 solute source were made. The change in boundary orientation and migration rate were compared with solute concentration. The liquid film model for coherency strain Induced migration was generalized to any non-cubic system and applied to CaCO3-SrCO3. The coherent layer was modeled as a thin film on an infinite half-space. The strain energy was found from solution of the Hooke's law expressions transformed to the appropriate coordinate system. For triclinic or monoclinic films the strain tensor was found by an eigenvector decomposition of the transformation matrix that defined the lattice parameter change with composition. High anisotropy of Vegard's law constants for CaCO3-SrCO3 caused (111) to have the lowest coherency strain per unit solute. Surfaces perpendicular to (111) in coherent equilibria were predicted to have half the solute concentration and three times the migration driving force of those perpendicular to (111). However, no correlation between solute concentration and boundary orientation was observed. Ambiguous and contradictory evidence for a relationship between solute concentration, boundary orientation, and migration rate was found. The self-stress state of a grain boundary in a solute diffusion field may be better modelled as hydrostatic rather than plane stress. Hydrostatic compression may interact with the boundary excess volume and cause a PV driving force for migration. Predictions based on coherent equilibrium at a surface have not been tested for that geometry in calcite; they should be tested before they are applied to grain boundaries.

In-Situ High Temperature Optical Microscopic Observations of Crystallization Mechanism in NdBa2Cu3Ox

1999 ◽  
Vol 569 ◽  
Author(s):  
D.K. Aswal ◽  
M. Shinmura ◽  
Y Hayakawa ◽  
M. Kumagawa
Keyword(s):  
High Temperature ◽  
Cooling Rate ◽  
Liquidus Line ◽  
Solute Diffusion ◽  
Limiting Factor ◽  
Layer By Layer ◽  
Temperature Solution ◽  
In Situ Observations ◽  
Rate Limiting

ABSTRACTThe pseudo-binary NdBa2Cu3O-Ba3Cu10O13phase diagrams and the crystallization of NdBa2Cu3Ox have been in-situ observed using high-temperature optical microscopy in air and under three different reduced oxygen atmospheres namely, 1%, 0.1% and 0.0097% oxygen in argon. The liquidus line was found to become narrower both in composition and temperature with reducing oxygen content in the atmosphere. These results suggested that while in air NdBa2Cu3Ox can be crystallized from both high-temperature solution and peritectic melt; under reduced oxygen atmospheres the crystallization of NdBa2Cu3Ox is only possible from a peritectic melt. The in-situ observations of crystallization of NdBa2Cu3Ox from high-temperature solutions revealed that the growth mechanism changes from 3D via 2D layer-by-layer to continuos dendritic growth with increasing cooling rate. On the other hand, the NdBa2Cu3Ox crystallization from a peritectic melt involved two distinct steps (i) conversion of Nd4Ba2Cu2Ox into NdBa2Cu3Ox and (ii) nucleation and growth of NdBa2Cu3Ox The growth morphology in this case was independent of the cooling rate. This result and the direct observation of the dissolution of Nd4Ba2Cu2Ox into the liquid suggested that the solute diffusion is the rate-limiting factor.

Faceting and Migration of Low Angle Tilt Grain Boundaries in Pure Aluminum

2007 ◽  
Vol 558-559 ◽  
pp. 903-908
Author(s):  
Dirk M. Kirch ◽  
Bing Bing Zhao ◽  
Dmitri A. Molodov ◽  
Günter Gottstein
Keyword(s):  
Grain Boundaries ◽  
Driving Force ◽  
Rotation Angle ◽  
Boundary Energy ◽  
Pure Aluminum ◽  
Boundary Surface ◽  
Structural Behavior ◽  
Grain Boundary Energy ◽  
And Migration

The kinetic and structural behavior of symmetrical <100> tilt grain boundaries with rotation angles 8.4°, 12.0°, 14.3° and 16.0° were investigated in-situ in a hot stage SEM in the temperature range between 380°C and 640°C. The results revealed that depending on the rotation angle the boundary either remained straight, became faceted or curved under the driving force provided by the boundary surface tension during high temperature annealing. The transition “facetedcurved boundary” was also found to depend on temperature. The observed behavior is attributed to the anisotropy of grain boundary energy with respect to boundary inclination.

An In-Situ Study of Velocity/Driving Force Relations for Interfacial Migration

1985 ◽  
Vol 62 ◽  
Author(s):  
Woonsup park ◽  
Samuel M. Allen
Keyword(s):  
Driving Force ◽  
Thin Foil ◽  
Al Alloys ◽  
Proportionality Constant ◽  
In Situ Study ◽  
Domain Structures ◽  
Transmission Electron ◽  
And Migration ◽  
Kinetics Of

ABSTRACTThe migration kinetics of antiphase boundaries (APBs) in long-range ordered Fe-Al alloys are analyzed using in-situ hot-stage transmission electron microscopy, making it possible to observe the interfacial migration directly as it occurs. The observed domain structures are essentially two dimensional due to the thin foil configuration of the specimen, facilitating analytical interpretation of the data. By measuring the local curvatures and migration distances from a series of micrographs taken at a constant temperature, the proportionality constant relating velocity to curvature can be determined. This proportionality constant, called the mobility for APB migration, is found to be independent of the curvature for <100> APBs in Fe-27 atomic percent Al at 745K, having the value of 4.8×10−19 m2/s.

Biomimetic materials

2018 ◽  
Author(s):  
Julian Vincent
Keyword(s):  
Hydrogen Bonds ◽  
Driving Force ◽  
Strain Energy ◽  
Molecular Level ◽  
Biological Materials ◽  
Low Energy ◽  
Stress Concentrations ◽  
Liquid Crystallinity ◽  
Biomimetic Materials

Biological materials present the conventional materials scientist with alternative ways of achieving durability, recyclability, and adaptability. Technical materials are commonly designed to resist the initiation of cracks; biological materials control disaster by initiating failure where it can be more closely controlled and the strain energy can be more easily absorbed, at the same time controlling shape so that stress concentrations are avoided in sensitive areas. Most materials are hydrated and soft, achieving stiffness by dehydration and mineralization. The low energy of the predominant hydrogen bonds allows relatively easy breakdown and recycling of the units of biological materials. Since most biological materials are metabolically accessible (obvious exceptions are keratins and wood) they can be recycled and repaired in situ, adapting the organism to changing circumstances internally and externally. At the molecular level, liquid crystallinity is a driving force.

Coherency strain energy as a driving force for discontinuous ordering

1997 ◽  
Vol 37 (3) ◽  
pp. 245-251 ◽  
Author(s):  
E. Rabkin ◽  
V. Semenov ◽  
W. Gust
Keyword(s):  
Driving Force ◽  
Strain Energy ◽  
Coherency Strain

In situ observations of electromigration induced void behavior

1995 ◽  
Vol 53 ◽  
pp. 244-245
Author(s):  
T. Marieb ◽  
J. C. Bravman ◽  
P. Flinn ◽  
D. Gardner ◽  
M. Madden
Keyword(s):  
Electron Microscopy ◽  
Void Nucleation ◽  
Plan View ◽  
Transmission Electron ◽  
Nucleation Sites ◽  
Microelectronics Industry ◽  
In Situ Observations ◽  
Backscatter Electron Detector ◽  
Voltage Scanning

Electromigration and stress voiding have been active areas of research in the microelectronics industry for many years. While accelerated testing of these phenomena has been performed for the last 25 years[1-2], only recently has the introduction of high voltage scanning electron microscopy (HVSEM) made possible in situ testing of realistic, passivated, full thickness samples at high resolution.With a combination of in situ HVSEM and post-testing transmission electron microscopy (TEM) , electromigration void nucleation sites in both normal polycrystalline and near-bamboo pure Al were investigated. The effect of the microstructure of the lines on the void motion was also studied.The HVSEM used was a slightly modified JEOL 1200 EX II scanning TEM with a backscatter electron detector placed above the sample[3]. To observe electromigration in situ the sample was heated and the line had current supplied to it to accelerate the voiding process. After testing lines were prepared for TEM by employing the plan-view wedge technique [6].

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