Verification of the elastic constants for α-Al2O3using high-resolution neutron diffraction

2010 ◽  
Vol 44 (1) ◽  
pp. 216-218 ◽  
Author(s):  
Erich H. Kisi ◽  
Christopher J. Howard ◽  
Jianfeng Zhang
Keyword(s):  
High Resolution ◽  
Neutron Diffraction ◽  
Single Crystal ◽  
Elastic Constants ◽  
Diffraction Method ◽  
Polycrystalline Sample ◽  
Lattice Strains ◽  
Recent Suggestion

Precise lattice strains measured using high-resolution neutron diffraction from a solid polycrystalline sample are used to explore the single-crystal elastic constants of α-Al2O3(corundum). The analysis confirms a recent suggestion that, contrary to the long-accepted view, the sign ofs14should be negative. It also indicates that the magnitude ofs13should be adjusted from −0.38 × 10−12to −0.47 × 10−12 Pa−1. It is found that, micromechanically, the polycrystal responds to stress in a manner very close to the Reuss limit. The results confirm the applicability of the diffraction method, which could prove useful when other techniques give ambiguous results.

Single Crystal Elastic Constants of the MAX Phase Ti3AlC2 Determined by Neutron Diffraction

2010 ◽  
Vol 638-642 ◽  
pp. 2417-2422 ◽  
Author(s):  
Oliver Kirstein ◽  
Jian F. Zhang ◽  
Erich H. Kisi ◽  
D.P. Riley ◽  
M.J. Styles ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Elastic Constants ◽  
Compressive Load ◽  
Polycrystalline Sample ◽  
Max Phase ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Diffraction Peaks ◽  
Good Agreement

The ternary ceramic Ti3AlC2 has an interesting combination of electrical, thermal and mechanical properties. Single crystal elastic constants under the Reuss approximation for the micromechanical state were obtained by analysing the shifts of neutron diffraction peaks while a polycrystalline sample was subjected to a compressive load varying from 5 to 300 MPa. The values of Young’s modulus and Poisson’s ratio computed from the single crystal compliances are in good agreement with those obtained directly from strain gauges and from the average changes in the a and c unit cell parameters.

Localization of Stresses in Polycrystalline Grains Measured by Neutron Diffraction and Predicted by Self-Consistent Model

2011 ◽  
Vol 681 ◽  
pp. 103-108
Author(s):  
Anita Gaj ◽  
Lea le Joncour ◽  
Andrzej Baczmanski ◽  
Sebastian Wroński ◽  
Benoit Panicaud ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Load Transfer ◽  
Diffraction Method ◽  
Lattice Strains ◽  
Consistent Model ◽  
Self Consistent ◽  
Main Component ◽  
Critical Resolved Shear Stress ◽  
Elastic Lattice

Time of flight neutron diffraction method was applied to measure elastic lattice strains in austenitic steel during "in situ" tensile test. Comparing experimental data with self-consistent model, the critical resolved shear stress and hardening parameters were determined for polycrystalline grains. The result allowed us to determine the main component of the stress localization tensor, relating the rate of grain stress with the applied macrostress rate. The evolution of concentration tensor in function of the applied macrostress was analyzed. Finally, the load transfer between grains during yielding of the sample was studied.

3C-SiC Buffer Layers Converted from Si at a Low Temperature

1999 ◽  
Vol 572 ◽  
Author(s):  
H. M. Liaw ◽  
S. Q. Hong ◽  
P. Fejes ◽  
D. Werho ◽  
H. Tompkins ◽  
...  
Keyword(s):  
High Resolution ◽  
Low Temperature ◽  
Single Crystal ◽  
Misfit Dislocation ◽  
Surface Region ◽  
Buffer Layers ◽  
Misfit Dislocations ◽  
Lattice Strains ◽  
High Resolution Tem ◽  
Sic Films

ABSTRACTWe have obtained single-crystal 3C-SiC films via conversion of the surface region of Si (111) and (100) wafers at 970 °C by reaction with C2H4 in an MBE reactor. The major defects in the films were clusters, voids, and misfit dislocations. Investigation by high resolution TEM images showed low lattice strains in the epitaxial layer due to the formation of 1 misfit dislocation for every 4 to 5 regular SiC planes that are bonded to Si at the interface. The clusters and voids often occurred in pairs. A model for forming the void-cluster pairs is suggested.

Double Bent Crystal Monochromator for High Resolution Neutron Powder Diffraction

2013 ◽  
Vol 28 (S2) ◽  
pp. S351-S359 ◽  
Author(s):  
P. Mikula ◽  
M. Vrána ◽  
J. Šaroun ◽  
B.S. Seong ◽  
W. Woo
Keyword(s):  
High Resolution ◽  
Neutron Diffraction ◽  
Powder Diffraction ◽  
Angular Resolution ◽  
Polycrystalline Sample ◽  
Neutron Powder Diffraction ◽  
Diffraction Experiment ◽  
Neutron Diffraction Experiment ◽  
Bent Crystal ◽  
Neutron Wavelength

Recent results of focusing and reflectivity properties of the dispersive double-bent-crystal monochromator have shown that it could be succesfully used in high resolution neutron diffraction experiment. By using a standard polycrystalline sample of α-Fe, the resolution of the diffraction performance in the vicinity of the scattering angle 2θS = 90o for the neutron wavelength λ= 0.162 nm was tested in detail. It has been found that for thin (1.3 mm) bent second crystal the angular resolution represented by FWHM of diffraction profiles was 1x10−3 rad for 211 and 200 reflections and about 3x10−3 rad for 220 reflection.

scholarly journals High-resolution single-crystal neutron diffraction to 10 GPa

2011 ◽  
Vol 67 (a1) ◽  
pp. C527-C527
Author(s):  
C. L. Bull ◽  
K. Komatsu ◽  
M. Guthrie ◽  
R. J. Nelmes ◽  
J. S. Loveday ◽  
...  
Keyword(s):  
High Resolution ◽  
Neutron Diffraction ◽  
Single Crystal ◽  
Resolution Single

Single Crystal Time-of-Flight Neutron Diffraction

2002 ◽  
Vol 85 (4) ◽  
pp. 297-318 ◽  
Author(s):  
J. Peters ◽  
W. Jauch
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Three Dimensional ◽  
Time Of Flight ◽  
Diffraction Method ◽  
Neutron Sources ◽  
X Ray ◽  
Sorting Technique ◽  
History Of ◽  
Neutron Diffraction Method

The last century has seen a large development in diffraction techniques. The time-of-flight neutron diffraction method is now so advanced that it provides high precision results for position and thermal parameters, which are complementary to other diffraction results from X-ray sources. Here we review the history of neutron sources, the difficulties encountered with the time-of-flight technique and an outlook for applications. In this context, we will show the limitations of existing neutron sources and the expected advantages of new spallation neutron sources. An overview of all corrections to be taken into account with the wavelength-sorting technique will be presented as well as actual results, how to overcome such problems, and the special difficulty of integration of three-dimensional Bragg peaks.

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