Glide Mechanisms of Dislocations in NiAl

1998 ◽  
Vol 552 ◽  
Author(s):  
D. Caillard
Keyword(s):  
Room Temperature ◽  
Cross Slip ◽  
Friction Forces ◽  
Temperature Range ◽  
Controlling Mechanism ◽  
Atomistic Calculations ◽  
Good Agreement

ABSTRACTThe glide properties of <001> dislocations have been studied by in situ straining experiments at and below room temperature, with the aim of studying slip, cross-slip, Peierls friction forces, and pinning at small obstacles. Most results are in a good agreement with atomistic calculations. It is concluded that unpinning from small extrinsic obstacles is probably the rate controlling mechanism in this temperature range and in the soft orientation.

In Situ Deep Level Transient Spectroscopy of Defect Evolution in Silicon Following Ion Implantation at 80 K

1998 ◽  
Vol 532 ◽  
Author(s):  
C. R. Cho ◽  
R. A. Brown ◽  
O. Kononchuk ◽  
N. Yarykin ◽  
G. Rozgonyi ◽  
...  
Keyword(s):  
Deep Level Transient Spectroscopy ◽  
Room Temperature ◽  
Deep Level ◽  
Temperature Range ◽  
Type Silicon ◽  
Defect Annealing ◽  
Interstitial Defects ◽  
Transient Spectroscopy ◽  
Dlts Spectra

ABSTRACTThe evolution of defects in Czochralski and epitaxial p- and n-type silicon wafers following irradiation with He. Si or Ge ions at 80 K has been investigated by in situ deep level transient spectroscopy (DLTS). Defect annealing and formation reactions have been observed over the temperature range 80–350 K. In p-type silicon, new species-dependent levels are observed immediately after implantation, but these levels anneal out at or below room temperature. The wellknown divacancy and interstitial defects, usually reported after room temperature implantation, are revealed in the DLTS spectra only upon annealing at 160–200 K. In n-type silicon, vacancy-oxygen pairs are observed immediately after implantation. However, vacancy-related defects continue to form over a broad temperature range in samples implanted with Si or Ge. These observations are consistent with a model whereby vacancies and interstitials are released from defect clusters at temperatures >200 K to form divacancies and other defect pairs which are stable at room temperature.

Vapour growth, morphology, absolute structure and pyroelectric coefficient of meta-nitroaniline single crystals

2019 ◽  
Vol 52 (3) ◽  
pp. 564-570 ◽  
Author(s):  
Rolf Hesterberg ◽  
Michel Bonin ◽  
Martin Sommer ◽  
Matthias Burgener ◽  
Bernhard Trusch ◽  
...  
Keyword(s):  
Room Temperature ◽  
Vapour Phase ◽  
Pyroelectric Coefficient ◽  
Growth Speed ◽  
Published Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
Absolute Structure ◽  
Good Agreement

The growth speed of (hkl) faces in the vapour phase, the absolute structure obtained by X-ray crystallography, and the value and the sign of the pyroelectric coefficient of meta-nitroaniline (mNA) were analysed in detail. The in situ observation of morphologically well developed faces of several mNA crystals growing in evacuated ampoules reveals no pronounced growth speed anisotropy for polar faces defining the unique axis 2 of the mm2 group. Scanning pyroelectric microscopy confirms mono-domain mNA crystals. X-ray measurements in the space group Pca21 show that the molecular planes coincide with the {\bar 211} and {\bar 2\bar 1\bar 1} faces, and the nitro groups cover the {201} face in the opposite direction to the crystal tip, characterizing the polar habitus studied here. At room temperature, the sign of the pyroelectric coefficient is positive for a measured effective value of 6.3 µC m−2 K−1, in good agreement with values reported by other authors. From previous elastic and piezoelectric published data, the secondary pyroelectric effect was calculated to be positive and far greater than the effective one, yielding a negative value for the primary pyroelectric coefficient.

scholarly journals DFT-based calculations of silicon complex structures in the KF-KCl-K2SiF6 and KF-KCl-K2SiF6-SiO2 melts

2019 ◽  
Vol 84 (10) ◽  
pp. 1129-1142 ◽  
Author(s):  
Alexey Vorob’ev ◽  
Andrey Isakov ◽  
Alexander Galashev ◽  
Yuri Zaikov
Keyword(s):  
First Principles ◽  
Potassium Ions ◽  
Complex Structures ◽  
Bond Lengths ◽  
Temperature Range ◽  
In Situ Data ◽  
The Stability ◽  
Complex Anions ◽  
Good Agreement

The length and energy of bonds in the complex anions of silicon formed in KF?KCl?K2SiF6 and KF?KCl?K2SiF6?SiO2 melts were evaluated using the method of first-principles molecular dynamics, accomplished by means of the Siesta program. The effect of K+ (from the second coordination sphere) on the stability of these complexes was studied. The bond lengths in the silicon complexes was found to change with increasing amount of the potassium ions. It was established that the following complexes [SiO4]4-, [SiO3F]3- and [SiF6]2- are the most stable in KF?KCl?K2SiF6 and KF?KCl? ?K2SiF6?SiO2 melts. The [SiO4]4- and [SiF6]2- complexes are thermally stable in the molten salt in the temperature range of 923?1073 K, whereas the [SiF7]3- structure, which is typical for the lattice of crystalline K3SiF7, is unstable in this temperature range. In the KF?KCl?K2SiF6?SiO2 melts, conditions above 1043 K were created allowing the transformation of [Si?3F]3- into [SiO4]4-. Within the studied temperature mode, the Si?F bond length is in the range 1.5? ?1.9 ? and the Si?O bond lengths is 1.5?1.7 ?. The obtained results are in a good agreement with in situ data of Raman spectroscopy for the KF?KCl?K2SiF6 and KF?KCl?K2SiF6?SiO2 melts.

scholarly journals Thermal Conductivity of Cu-Cr-Zr-Ti Alloy in the Temperature Range of 300–873 K

2012 ◽  
Vol 2012 ◽  
pp. 1-4 ◽  
Author(s):  
S. Chenna Krishna ◽  
N. Supriya ◽  
Abhay K. Jha ◽  
Bhanu Pant ◽  
S. C. Sharma ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Room Temperature ◽  
Ofhc Copper ◽  
Ti Alloy ◽  
Phonon Thermal Conductivity ◽  
Temperature Range ◽  
Transmission Electron

In the present investigation, thermal conductivity of Cu-Cr-Zr-Ti alloy was determined as the product of the specific heat (), thermal diffusivity (), and density () in the temperature range of 300–873 K. The experimental results showed that the thermal conductivity of the alloy increased with increase in temperature up to 873 K and the data was accurately modeled by a linear equation. For comparison, thermal conductivity was also evaluated for OFHC copper in the same temperature range. The results obtained were discussed using electrical conductivity and hardness measurements made at room temperature. Transmission electron microscopy (TEM) was done to understand the microstructural changes occurring in the sample after the test. Wiedemann-Franz-Lorenz law was employed for calculating electronic and phonon thermal conductivity using electrical conductivity. On the basis of studies conducted it was deduced that in situ aging may be one of the reasons for the increase in thermal conductivity with temperature for Cu-Cr-Zr-Ti alloy.

A Tem Study of the Dislocation Structure in a Ni3Al-Based Alloy at Temperatures Below the Peak in Flow Stress

1990 ◽  
Vol 213 ◽  
Author(s):  
Mao Wen ◽  
Dongliang Lin
Keyword(s):  
Flow Stress ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Cross Slip ◽  
Directionally Solidified ◽  
Temperature Range ◽  
Weak Beam

ABSTRACTDislocation structure in a directionally solidified Ni3Al-based alloy deformed at temperatures below the peak in flow stress has been studied by the weak beam TEM technique. At room temperature, the screw superdislocations are partly transformed into Kear-Wilsdorf configurations. With increasing temperatures, the transformed Kear-Wilsdorf parts increase until the temperature reaches 450°C, at which the screw superdislocations are wholly transformed. Bending of the Kear-Wilsdorf configurations on {0101} planes is observed at 450°C, which is believed to be the cause of interaction of Kear-Wilsdorf configurations with superkinks. The Contribution of superkink motion to deformation is discussed. The results suggest that deformation in this temperature range occurs primarily by the slip of non-screw components on {lll} planes, which is consistent with the widely accepted cross slip pinning model.

Donage and in Situ Annealing During Ion Implantation

1982 ◽  
Vol 14 ◽  
Author(s):  
D. K. Sadana ◽  
J. Washburn ◽  
P. F. Byrne ◽  
N. W. Cheung
Keyword(s):  
Ion Implantation ◽  
Room Temperature ◽  
Amorphous Region ◽  
Ion Beams ◽  
Temperature Range ◽  
Transmission Electron ◽  
Annealing Effects ◽  
Relative Narrowing ◽  
Crystalline Matrix

ABSTRACTFormation of amorphous (α) layers in Si during ion implantation in the energy range 100 KeV–11MeV and temperature range liquid nitrogen (LN)-100°C has been investigated.Cross-sectional transmission electron microscopy (XTEM) shows that buried amorphous layers can be created for both room temperature (RT) and LN temperature implants, with a wider 100 percent amorphous region for the LN cooled case. The relative narrowing of the α layer during RT implantation is attributed to in situ annealing. Implantation to the same fluence at temperatures above 100°C does not produce αlayers. To further investigate in situ annealing effects, specimens already containing buried α layers were further irradiated with ion beams in the temperature range RT-400°C. It was found that isolated small α zones (< 50 Å diameter)embedded in the crystalline matrix near the two α/c interfaces dissolved into the crystal but the thickness of the 100 percent α layer was not appreciably affected by further implantation at 200°C. A model for in situ annealing during implantation is presented.

In Situ TEM Observations of Cross-Slip Mechanisms in NiAl with a Soft Orientation

1996 ◽  
Vol 460 ◽  
Author(s):  
C. Vailhe ◽  
J. Douin ◽  
D. Caillard
Keyword(s):  
Single Crystals ◽  
Room Temperature ◽  
Cross Slip ◽  
In Situ Tem ◽  
In Situ Experiments ◽  
Crystallographic Planes

ABSTRACTIn situ experiments have been conducted in NiAl single crystals in the soft orientation, at room temperature, in order to investigate the glide process of [100] dislocations. The results show that dislocations have a kinked shape in agreement with what is expected from anisotropie elasticity. Intensive cross-slip is observed, leading to slip in non-crystallographic planes and dipole formation. The ductility of the alloy is then discussed.

Dislocation structures around SiO2 Particles in aged Cu-Cr-SiO2

1978 ◽  
Vol 36 (1) ◽  
pp. 594-595
Author(s):  
N.J. Long ◽  
M.H. Loretto ◽  
C.H. Lloyd
Keyword(s):  
Flow Stress ◽  
Single Crystals ◽  
Room Temperature ◽  
Thin Foil ◽  
Age Hardening ◽  
Dispersion Strengthening ◽  
Accurate Picture ◽  
The Matrix ◽  
Very High ◽  
Good Agreement

IntroductionThere have been several t.e.m. studies (1,2,3,4) of the dislocation arrangements in the matrix and around the particles in dispersion strengthened single crystals deformed in single slip. Good agreement has been obtained in general between the observed structures and the various theories for the flow stress and work hardening of this class of alloy. There has been though some difficulty in obtaining an accurate picture of these arrangements in the case when the obstacles are large (of the order of several 1000's Å). This is due to both the physical loss of dislocations from the thin foil in its preparation and to rearrangement of the structure on unloading and standing at room temperature under the influence of the very high localised stresses in the vicinity of the particles (2,3).This contribution presents part of a study of the Cu-Cr-SiO2 system where age hardening from the Cu-Cr and dispersion strengthening from Cu-Sio2 is combined.

Otoconia perfect/imperfect crystals

1994 ◽  
Vol 52 ◽  
pp. 42-43
Author(s):  
César D. Fermin ◽  
Dale Martin
Keyword(s):  
Image Processing ◽  
Room Temperature ◽  
Phosphotungstic Acid ◽  
Gallus Domesticus ◽  
Crystal Matrix ◽  
Organic Templates ◽  
Image Processing Algorithms ◽  
Processing Algorithms ◽  
Diffraction Patterns

Otoconia of higher vertebrates are interesting biological crystals that display the diffraction patterns of perfect crystals (e.g., calcite for birds and mammal) when intact, but fail to produce a regular crystallographic pattern when fixed. Image processing of the fixed crystal matrix, which resembles the organic templates of teeth and bone, failed to clarify a paradox of biomineralization described by Mann. Recently, we suggested that inner ear otoconia crystals contain growth plates that run in different directions, and that the arrangement of the plates may contribute to the turning angles seen at the hexagonal faces of the crystals.Using image processing algorithms described earlier, and Fourier Transform function (2FFT) of BioScan Optimas®, we evaluated the patterns in the packing of the otoconia fibrils of newly hatched chicks (Gallus domesticus) inner ears. Animals were fixed in situ by perfusion of 1% phosphotungstic acid (PTA) at room temperature through the left ventricle, after intraperitoneal Nembutal (35mg/Kg) deep anesthesia. Negatives were made with a Hitachi H-7100 TEM at 50K-400K magnifications. The negatives were then placed on a light box, where images were filtered and transferred to a 35 mm camera as described.

In Situ Localization of PPAR Gamma and Uncoupling Protein in Mouse Embryo Sections Using Digoxigenin-Labeled Riboprobes

1996 ◽  
Vol 54 ◽  
pp. 32-33
Author(s):  
C. Jennermann ◽  
S. A. Kliewer ◽  
D. C. Morris
Keyword(s):  
Alkaline Phosphatase ◽  
Room Temperature ◽  
Uncoupling Protein ◽  
Ppar Gamma ◽  
Nuclear Hormone Receptor ◽  
Full Length ◽  
Northern Analysis ◽  
Peroxisome Proliferator

Peroxisome proliferator-activated receptor gamma (PPARg) is a member of the nuclear hormone receptor superfamily and has been shown in vitro to regulate genes involved in lipid metabolism and adipocyte differentiation. By Northern analysis, we and other researchers have shown that expression of this receptor predominates in adipose tissue in adult mice, and appears first in whole-embryo mRNA at 13.5 days postconception. In situ hybridization was used to find out in which developing tissues PPARg is specifically expressed.Digoxigenin-labeled riboprobes were generated using the Genius™ 4 RNA Labeling Kit from Boehringer Mannheim. Full length PPAR gamma, obtained by PCR from mouse liver cDNA, was inserted into pBluescript SK and used as template for the transcription reaction. Probes of average size 200 base pairs were made by partial alkaline hydrolysis of the full length transcripts. The in situ hybridization assays were performed as described previously with some modifications. Frozen sections (10 μm thick) of day 18 mouse embryos were cut, fixed with 4% paraformaldehyde and acetylated with 0.25% acetic anhydride in 1.0M triethanolamine buffer. The sections were incubated for 2 hours at room temperature in pre-hybridization buffer, and were then hybridized with a probe concentration of 200μg per ml at 70° C, overnight in a humidified chamber. Following stringent washes in SSC buffers, the immunological detection steps were performed at room temperature. The alkaline phosphatase labeled, anti-digoxigenin antibody and detection buffers were purchased from Boehringer Mannheim. The sections were treated with a blocking buffer for one hour and incubated with antibody solution at a 1:5000 dilution for 2 hours, both at room temperature. Colored precipitate was formed by exposure to the alkaline phosphatase substrate nitrobluetetrazoliumchloride/ bromo-chloroindlylphosphate.

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