scholarly journals Stacking Fault Energy of Si Nanocrystals Embedded in SiO2

2011 ◽  
Vol 2011 ◽  
pp. 1-3 ◽  
Author(s):  
Y. Q. Wang ◽  
W. S. Liang ◽  
G. G. Ross
Keyword(s):  
Stacking Faults ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
High Temperature Annealing ◽  
Hrtem Image ◽  
Burgers Vector ◽  
Transmission Electron ◽  
Hrtem Observation ◽  
Si Nanocrystals ◽  
Perfect Dislocation

Si nanocrystals (Si nc) were produced by the implantation of Si+ into a SiO2 film on (100) Si, followed by high-temperature annealing. High-resolution transmission electron microscopy (HRTEM) observation has shown that a perfect dislocation (Burgers vector b=(1/2)〈110〉) can dissociate into two Shockley partials (Burgers vector b=(1/6)〈112〉) bounding a strip of stacking faults (SFs). The width of the SFs has been determined from the HRTEM image, and the stacking fault energy for Si nc has been calculated. The stacking fault energy for Si nc is compared with that for bulk Si, and the formation probability of defects in Si nc is also discussed. The results will shed a light on the dissociation of dislocations in nanoparticles.

Dislocations and stacking faults in stainless steel

1957 ◽  
Vol 240 (1223) ◽  
pp. 524-538 ◽  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Stainless Steel ◽  
Grain Boundaries ◽  
Stacking Faults ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Thin Sections ◽  
Partial Dislocations ◽  
Transmission Electron

Further experiments by transmission electron microscopy on thin sections of stainless steel deformed by small amounts have enabled extended dislocations to be observed directly. The arrangement and motion of whole and partial dislocations have been followed in detail. Many of the dislocations are found to have piled up against grain boundaries. Other observations include the formation of wide stacking faults, the interaction of dislocations with twin boundaries, and the formation of dislocations at thin edges of the foils. An estimate is made of the stacking-fault energy from a consideration of the stresses present, and the properties of the dislocations are found to be in agreement with those expected from a metal of low stacking-fault energy.

Observation and analysis of extended dislocations in an Al–Pd–Mn icosahedral quasicrystal by transmission electron microscopy

1995 ◽  
Vol 10 (11) ◽  
pp. 2742-2748 ◽  
Author(s):  
Jianglin Feng ◽  
Renhui Wang ◽  
Mingxing Dai
Keyword(s):  
Physical Space ◽  
Stacking Fault ◽  
Icosahedral Quasicrystal ◽  
Burgers Vector ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Perfect Dislocation ◽  
Complementary Space ◽  
Convergent Beam ◽  
First Time

Extended dislocations including partial dislocations and a stacking fault in Al70Pd20Mn10 icosahedral quasicrystal have been observed and identified for the first time. The diffraction contrast and defocus convergent-beam electron diffraction experiments show that the dissociation of the extended dislocations is of the form 1/2<1 −2 0 0 −2 1> → 1/4<1 −3 1 −1 −1 1>+ 1/4<1 −1 −1 1 −xs3 1> with a stacking fault between these two partial dislocations. For the partial dislocations, the Burgers vector components in physical space b¶part are along different fivefold axes with a magnitude of 0.17 nm, which is about one seventh of that in complementary space. For the perfect dislocation, the Burgers vector component in physical subspace b¶perf is along a twofold axis with a magnitude of 0.183 nm, which is about an eleventh of that in complementary space.

On the determination of stacking-fault energy from dislocation nodes observed by TEM

1994 ◽  
Vol 52 ◽  
pp. 686-687
Author(s):  
Paulo J. Ferreira
Keyword(s):  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Radius Of Curvature ◽  
Bright Field ◽  
Burgers Vector ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Fundamental Understanding ◽  
Line Direction

A fundamental understanding of the mechanical and physical behaviour of metals requires a knowledge of the stacking-fault energy (SFE). This aspect is important because the possibility of cross-slip and thus plastic deformation is a function of the SFE of the material. Impurities may segregate to the faults and change the SFE, which may affect the mechanical behaviour. For low SFE’s materials, the SFE can be determined rather accurately from transmission electron microscopy evaluation of the radius of curvature of dislocation nodes formed by the attractive interaction of dislocations (Fig. 1).This work is directed towards applying the T.E.M. technique to determine the SFE of a 310S stable austenitic stainless steel. The specimens were observed in a JEOL 4000 microscope operated at an accelerating voltage of 200 kV, and equipped with a double tilt stage. Conventional two beam bright field images were used to determine the Burgers vector and line direction of the partial dislocations.

Defects in Germanium Nanocrystals Produced by Ion Implantation

2013 ◽  
Vol 709 ◽  
pp. 148-152
Author(s):  
Yu Juan Zhang ◽  
Lei Shang
Keyword(s):  
Electron Microscopy ◽  
Light Emission ◽  
Stacking Faults ◽  
Implantation Dose ◽  
Defect Structures ◽  
High Temperature Annealing ◽  
Planar Defects ◽  
Transmission Electron ◽  
Microstructural Defects ◽  
Germanium Nanocrystals

Germanium nanocrystals (Ge-nc) were produced by the implantation of Ge+ into a SiO2 film deposited on (100) Si, followed by a high-temperature annealing. High-resolution transmission electron microscopy (HRTEM) has been used to investigate the defect structures inside the Ge-nc produced by different implantation doses (1×1016, 2×1016, 4×1016 and 8×1016 cm-2). It has been found that the planar defects such as nanotwins and stacking faults (SFs) are dominant in Ge-nc (60%) for the samples with implantation doses higher than 2×1016 cm-2, while for the sample with an implantation dose lower than 1×1016 cm-2, fewer planar defects are observed in the Ge-nc (20%). The percentages of nanotwins in the planar defects are 87%, 77%, 67% and 60% in four samples, respectively. The twinning structures include single twins, double twins and multiple twins. We also found that there are only SFs in some nanocrystals, and in others the SFs coexist with twins. These microstructural defects are expected to play an important role in the light emission from the Ge-nc.

Evolution of the microstructure and its parameters in copper-aluminum polycrystalline alloys during active plastic deformation with different stacking-fault energy

2021 ◽  
pp. 43-47
Author(s):  
N.A. Koneva ◽  
◽  
L.I. Trishkina ◽  
T.V. Cherkasova ◽  
A.N. Solov’ev ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Deformation Degree ◽  
Transmission Electron Microscopy Analysis ◽  
Al Content ◽  
Polycrystalline Alloys ◽  
Transmission Electron ◽  
Electron Microscopy Analysis ◽  
Copper Aluminum

Evolution of the dislocation structure during active plastic deformation was carried out in copper-aluminum alloys with Al content of 0.5-14 at. % using transmission electron microscopy. Analysis of the types of the dislocation substructure as a function of the alloying element content and deformation degree was conducted. The following parameters of the defect substructure were measured: average scalar dislocation density, curvature-torsion of the crystal lattice and microtwin density. The effect of stacking fault energy on accumulation of defects in the alloys was observed and evaluated.

scholarly journals Dissociation Behavior of Dislocations in Ice

Crystals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 386
Author(s):  
Takeo Hondoh
Keyword(s):  
Basal Plane ◽  
Dislocation Line ◽  
Stacking Faults ◽  
Physical Models ◽  
Time Constants ◽  
Burgers Vector ◽  
Partial Dislocations ◽  
Perfect Dislocation ◽  
Low Energies ◽  
Dissociated State

Dislocations in ice behave very differently from those in other materials due to the very low energies of stacking faults in the ice basal plane. As a result, the dislocations dissociate on the basal plane, from a perfect dislocation into two partial dislocations with equilibrium width we ranging from 20 to 500 nm, but what is the timescale to reach this dissociated state? Using physical models, we estimate this timescale by calculating two time-constants: the dissociation-completing time td and the dissociation-beginning time tb. These time constants are calculated for two Burgers vectors as a function of temperature. For perfect dislocations with Burgers vector <c + a>, td is more than one month even at the melting temperature TM, and it exceeds 103 years below −50 ℃, meaning that the dissociation cannot be completed during deformation over laboratory timescales. However, in this case the beginning time tb is less than one second at TM, and it is within several tens of minutes above −50 ℃. These dislocations can glide on non-basal planes until they turn to the dissociated state during deformation, finally resulting in sessile extended dislocations of various widths approaching to the equilibrium value we. In contrast, for perfect dislocations with Burgers vector <a>, td is less than one second above −50 ℃, resulting in glissile extended dislocations with the equilibrium width we on the basal plane. This width is sensitive to the shear stress τ exerted normal to the dislocation line, leading to extension of the intervening stacking fault across the entire crystal grain under commonly accessible stresses. Also, due to the widely dissociated state, dislocations <a> cannot cross-slip to non-basal planes. Such behavior of extended dislocations in ice are notable when compared to those of other materials.

Overlapping Shockley/Frank Faults in 4H-SiC PiN Diodes

2006 ◽  
Vol 527-529 ◽  
pp. 383-386 ◽  
Author(s):  
Mark E. Twigg ◽  
Robert E. Stahlbush ◽  
Peter A. Losee ◽  
Can Hua Li ◽  
I. Bhat ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Light Emission ◽  
Stacking Faults ◽  
Dark Field ◽  
Pin Diodes ◽  
Plan View ◽  
Planar Defects ◽  
Burgers Vector ◽  
Partial Dislocations ◽  
Transmission Electron

Using light emission imaging (LEI), we have determined that not all planar defects in 4H-SiC PiN diodes expand in response to bias. Accordingly, plan-view transmission electron microscopy (TEM) observations of these diodes indicate that these static planar defects are different in structure from the mobile stacking faults (SFs) that have been previously observed in 4H-SiC PiN diodes. Bright and dark field TEM observations reveal that such planar defects are bounded by partial dislocations, and that the SFs associated with these partials display both Frank and Shockley character. That is, the Burgers vector of such partial dislocations is 1/12<4-403>. For sessile Frank partial dislocations, glide is severely constrained by the need to inject either atoms or vacancies into the expanding faulted layer. Furthermore, these overlapping SFs are seen to be fundamentally different from other planar defects found in 4H-SiC.

THE STACKING-FAULT ENERGY IN α-SILVER – TIN ALLOYS

1967 ◽  
Vol 45 (2) ◽  
pp. 787-795 ◽  
Author(s):  
A. W. Ruff Jr. ◽  
L. K. Ives
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Pure Silver ◽  
Tin Alloys ◽  
Transmission Electron ◽  
Direct Measurements ◽  
Extended Dislocation

Direct measurements by transmission electron microscopy on extended dislocation nodes in alloys of tin in silver have led to values for the intrinsic stacking-fault energy. The values decreased smoothly from 23 erg/cm2 for pure silver to 4.2 erg/cm2 for 7.8 at.% tin. The results are compared with previous determinations in other silver-base alloys.

Stacking Faults in Crystals

1968 ◽  
Vol 26 ◽  
pp. 250-251
Author(s):  
P. C. J. Gallagher
Keyword(s):  
Stacking Faults ◽  
Elastic Equilibrium ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Major Influence ◽  
Face Centered Cubic ◽  
Degree Of Dissociation ◽  
Partial Dislocations ◽  
Layer Structures ◽  
Face Centered

Stacking faults are an important substructural feature of many materials, and have been widely studied in layer structures (e.g. talc) and in crystals with hexagonal and face centered cubic structure. Particular emphasis has been placed on the study of faulted defects in f.c.c. alloys, since the width of the band of fault between dissociated partial dislocations has a major influence on mechanical properties.Under conditions of elastic equilibrium the degree of dissociation reflects the balance of the repulsive force between the partials bounding the fault, and the attractive force associated with the need to minimize the energy arising from the misfits in stacking sequence. Examples of two of the faulted defects which can be used to determine this stacking fault energy, Υ, are shown in Fig. 1. Intrinsically faulted extended nodes (as at A) have been widely used to determine Υ, and examples will be shown in several Cu and Ag base alloys of differing stacking fault energy. The defect at B contains both extrinsic and intrinsic faulting, and readily enables determination of both extrinsic and intrinsic fault energies.

Sign in / Sign up

Export Citation Format

Share Document