Athermal Motion of Grain Boundaries, Twins and Triple Junctions in Zn

2004 ◽  
Vol 467-470 ◽  
pp. 801-806 ◽  
Author(s):  
Vera G. Sursaeva
Keyword(s):  
Thermal Expansion ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Triple Junction ◽  
Triple Junctions ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
The Difference ◽  
The Individual ◽  
Individual Grains

When a bicrystal or polycrystal are subjected to a change in temperature, the individual responses of the two adjoining crystals may differ in a manner, which tends to produce a dilatational mismatch along grain boundaries. If compatibility is to be retained along the interface, an additional set of stresses must then be generated in order to conserve this compatibility. ‘Compatibility stresses’ will also be generated whenever a polycrystal is heated or cooled and the thermal expansion coefficients of the individual grains are different due to thermal expansion anisotropy. In such cases adjacent grains will attempt to change dimensions and develop mismatches by amounts controlled by the parameter Δa*ΔΤ, where Δa is the difference between the thermal expansion coefficients in the appropriate directions, and ΔΤ is the temperature change. These ‘compatibility stresses’ may be relieves if grain boundary motion, triple junction migration and grain growth are possible. These ‘compatibility stresses’ may play important role in the kinetic behavior of the microstructure ranging from influencing the behavior of lattice dislocations near the grain boundaries to promoting grain boundary and triple junction dragging or moving. The motion of the ‘special’ grain boundaries, triple junctions with ‘special’ grain boundaries and twins under the influence of internal mechanical stresses is the main subject of this paper.

Study of the Ti-Mn-Al-Si-O-S Complex Inclusions Inducing Intragranular Acicular Ferrite

2012 ◽  
Vol 535-537 ◽  
pp. 620-627 ◽  
Author(s):  
Chengwei Yang ◽  
Min Jiang ◽  
Xinhua Wang ◽  
Tie Ou
Keyword(s):  
Thermal Expansion ◽  
Confocal Laser ◽  
Complex Inclusion ◽  
Inclusion Formation ◽  
The Core ◽  
Thermal Expansion Coefficients ◽  
Intragranular Acicular Ferrite ◽  
Expansion Coefficients ◽  
The Difference ◽  
Confocal Laser Microscope

High temperature confocal laser microscope, FE-SEM-EDS and EPMA were utilized to study the Ti-Mn-Al-Si-O-S complex inclusion inducing IAF in Ti deoxidized steel. FactStage was also used to calculate the thermodynamics of inclusion formation. It was demonstrated that when the cooling rate is fixed to 5°C/s, IAF can be induced by complex inclusions which act as the core of IAF at 609°C. Microstructure of the complex inclusions is complicated. These inclusions are consisted of the TiOx-MnO core which is surrounded by MnO-Al2O3-SiO2 complex inclusions and small amount of MnS. The reason that Ti-Mn-Al-Si-O-S complex inclusions can induce IAF is that a Mn-depleted zone is formed by the core TiOx-MnO and the MnS around it. Meanwhile, the difference between MnO-Al2O3-SiO2 and austenite thermal expansion coefficients is tremendous is another principle element for the IAF formation.

Thermodynamics of Epitaxial Ferroelectric Films.

1995 ◽  
Vol 401 ◽  
Author(s):  
S. B. Desu ◽  
V. P. Dudkevich ◽  
P. V. Dudkevich ◽  
I. N. Zakharchenko ◽  
G. L. Kushlyan
Keyword(s):  
Thermal Expansion ◽  
Phase Transitions ◽  
Misfit Dislocations ◽  
Ferroelectric Films ◽  
Growth Stresses ◽  
Substrate Interaction ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
The Difference ◽  
Film Substrate

AbstractThe problem of phase transitions and physical properties of the BaTiO3-type films on the (001) single-crystal substrates of the cubic syngony was solved in the limits of the Landau- Devonshire thermodynamics. The thermoelastic film-substrate interaction caused by the difference between thermal expansion coefficients was strictly taken into consideration. The model was based on the following assumptions: 1) the film is closely conjugated with the substrate; 2) the film is sufficiently “thick”to find itself unstrained at the growth temperature Ts, ( growth stresses were compensated by misfit dislocations ), and 3) the film is sufficiently “thin, and the stresses arising at the temperatures T>Ts may be considered to be uniform.

A Study on Metal-Ceramic Thermal Expansion Compatibility

2014 ◽  
Vol 216 ◽  
pp. 85-90
Author(s):  
Marian Miculescu ◽  
Mihai Branzei ◽  
Florin Miculescu ◽  
Daniela Meghea ◽  
Marin Bane
Keyword(s):  
Thermal Expansion ◽  
Bonding Strength ◽  
Linear Thermal Expansion ◽  
Metal Bonding ◽  
Thermal Expansion Coefficients ◽  
Metal Ceramic ◽  
Thermal Compatibility ◽  
Expansion Coefficients ◽  
The Difference ◽  
Dental Applications

Push rod method for determining linear thermal expansion using vertical differential dilatometer was used in the study of the thermal compatibility of metal-ceramic systems for dental applications. The purpose of this study consisted in evaluating the effectiveness of dental coating by determining the ceramic metal bonding strength of metal-ceramic couples (Ni-Cr and Co-Cr alloy coated with dental ceramic) and correlation with the difference of linear thermal expansion coefficients of metals and ceramics.

Triple Junction Controlled Grain Growth

2004 ◽  
Vol 467-470 ◽  
pp. 1093-1098 ◽  
Author(s):  
Vladimir Yu. Novikov
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Growth Kinetics ◽  
Triple Junction ◽  
Nanocrystalline Materials ◽  
Triple Junctions ◽  
Restricted Mobility ◽  
Triple Junction Mobility ◽  
Grain Diameter

Grain growth in 2D polycrystals was simulated under the supposition that triple junctions possess a restricted mobility and so impede the migration of grain boundaries. A parameter 0 L = 0 D m taking into account the effect of triple junctions was varied in the range from 0.003 to 270 (m is the ratio of the triple junction mobility to that of grain boundary and 0 D the initial grain diameter). It was shown that at 0 L <0.4–0.5, i.e. at a small 0 D and small m, the growth kinetics becomes linear. It is supposed that the effect of triple junctions on grain growth can be observed in nanocrystalline materials.

Thermal Stability of the Structural and Electronic Properties of Strain Symmetrized Sim Gen Superlattices and Ungraded, Nearly Relaxed Si1−x Gex

1992 ◽  
Vol 281 ◽  
Author(s):  
P. A. Dafesh ◽  
P. M. Adams ◽  
V. Arbet-Engels ◽  
K. L. Wang
Keyword(s):  
Thermal Expansion ◽  
Energy Shift ◽  
Buffer Layers ◽  
X Ray ◽  
Lattice Constants ◽  
Thermal Expansion Coefficients ◽  
Structural And Electronic Properties ◽  
Expansion Coefficients ◽  
The Difference ◽  
Anneal Temperature

ABSTRACTIn this study, photoreflectance (PR) spectroscopy and x-ray rocking curves measurements were used to study the variation in strain configuration, defect propagation, structural properties and direct electronic transition energies in Sim Gen superlattices (SL) and nearly relaxed Si1−x Gex buffer layers grown on < 100 > Si as a function of annealing temperature. The in-plane (a│) and perpendicular (a┴) lattice constants of the alloy buffer layers are found to vary only slightly with anneal temperature, TA, up to a temperature To. For TA To, the in-plane strain changed from roughly zero a│ ≈ a┴ (relaxed) or a┴ > a│ (compressive) to a┴ > a│ (tensile). This change in strain configuration is believed to be caused by the difference in thermal expansion coefficients between the epilayer and the Si substrate. The anneal temperature T0 is also correlated with the disappearance of higher order x-ray harmonics from the SL. This point was also correlated with a large energy shift and broadening of the PR spectra from the SL. The shift in energy of the PR spectra is explained in terms of the interdiffusion of Si and Ge at SL heterointerfaces, and to a lesser degree, the strain induced by the above mentioned difference in thermal expansion coefficients. The PR spectra of the alloy E0 transitions are also observed to shift to higher energy with increasing TA.

Defect Reduction by Thermal Cyclic Growth in GaAs Grown on Si by Movpe

1993 ◽  
Vol 325 ◽  
Author(s):  
W. KÜrner ◽  
R. Dieter ◽  
K. Zieger ◽  
F. Goroncy ◽  
A. DÖrnen ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Thermal Stress ◽  
Dislocation Density ◽  
Lattice Mismatch ◽  
Gaas Layer ◽  
Defect Reduction ◽  
Thermal Expansion Coefficients ◽  
Related Defect ◽  
Expansion Coefficients ◽  
The Difference

AbstractThe growth of GaAs epilayers on Si should combine the advantages of both materials. The lattice mismatch and the difference in thermal expansion coefficients, however, result in the yet unsolved problems of high dislocation density and thermal stress in the GaAs layer. Recently, considerable improvements have been achieved by a ‘thermal cyclic growth’ (TCG) process. In this study we focus on the reduction of high defect concentration and dislocation density. The improvement of the epilayer quality is verified by DLTS, PL and DCXD. Results of TEM and DLTS measurements lead to the identification of a dislocation related defect.

Microstructure and Magnetic Properties of NdFeB Magnets Using Fluorides Nano-Coated Process

2010 ◽  
Vol 638-642 ◽  
pp. 1357-1361 ◽  
Author(s):  
Matahiro Komuro ◽  
Yuichi Satsu ◽  
Hiroyuki Suzuki
Keyword(s):  
Magnetic Properties ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Triple Junction ◽  
Aging Process ◽  
Triple Junctions ◽  
Ndfeb Magnets ◽  
Fcc Structure ◽  
Microstructure And Magnetic Properties

Nd2Fe14B magnets could be sintered using terbium fluoride coated Nd2Fe14B powders. Fluorine atoms were segregated at the triple junctions and grain boundary after sintering and aging process. NdOF with fcc structure was grown at the triple junction. Terbium atoms were also distributed near grain boundaries by interdiffusion between the fluoride and Nd2Fe14B. No fluorine atoms were detected in Nd2Fe14B phase. The coercivity for 0.5wt% terbium fluoride coated magnet showed 1.23 MA/m which was 1.2 times higher than that for non-coated magnet with 1.04MA/m. The distribution of terbium and fluorine atoms increases the coercivity without reduction of remanence.

scholarly journals High Resolution Electron Microscopy of Grain Boundaries in Nanophase Palladium

1989 ◽  
Vol 153 ◽  
Author(s):  
G. J. Thomas ◽  
R. W. Siegel ◽  
J. A. Eastman
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Lattice Structure ◽  
High Resolution Electron Microscopy ◽  
Coarse Grained ◽  
Resolution Electron ◽  
The Individual ◽  
Individual Grains

AbstractUsing high resolution electron microscopy, consolidated nanophase palladium samples were examined following electrolytic thinning after a hydriding - dehydriding cycle at 310 K. Due to the small size and random orientations of the individual grains, a large number of grain boundaries were available for examination. Some of these yielded adequate imaging conditions to allow observation of the lattice structure in the grain boundary regions. Image simulations were performed to determine the sensitivity of the technique to lattice disorder. The results of these studies suggest that grain boundary structures in nanophase palladium are similar to those in conventional coarse-grained polycrystals.

The influence of the sapphire substrate on the temperature dependence of the GaN bandgap

1999 ◽  
Vol 572 ◽  
Author(s):  
Joachim Krüiger ◽  
Noad Shapiro ◽  
Sudhir Subramanya ◽  
Yihwan Kim ◽  
Henrik Siegle ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Temperature Dependence ◽  
Sapphire Substrate ◽  
Measured Temperature ◽  
Temperature Range ◽  
Thermal Expansion Coefficients ◽  
Small Influence ◽  
Expansion Coefficients ◽  
The Difference ◽  
First Time

ABSTRACTThis paper analyses the influence of the sapphire substrate on stress in GaN epilayers in the temperature range between 4K and 600K. Removal of the substrate by a laser assisted liftoff technique allows, for the first time, to distinguish between stress and other material specific temperature dependencies. In contrast to the prevailing assumption in the literature, that the difference in the thermal expansion coefficients is the main cause for stress it is found that the substrate has a rather small influence in the examined temperature range. The measured temperature dependence of stress is in contradiction to the published values for the thermal expansion coefficients for sapphire and GaN.

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