Determination of Residual Strains in an Al-SiCw Composite Using CBED

1990 ◽  
Vol 48 (2) ◽  
pp. 502-503
Author(s):  
S.J. Rozeveld
Keyword(s):  
Thermal Expansion ◽  
Electron Diffraction ◽  
Small Area ◽  
Room Temperature ◽  
Mechanical Response ◽  
Experimental Measurements ◽  
The Matrix ◽  
Residual Strains ◽  
Matrix Dislocation

It is well established that large stresses may be introduced into Al-SiCw composites by thermal cycling. Due to the large difference in thermal expansion of Al and SiC, a temperature change of ~200°C is sufficient to generate dislocations in the matrix. Dislocation production does not relieve all of the stress and residual strains, which are slightly below the yield point, can remain in the matrix. Although these residual strains will influence both the aging characteristics of the matrix and mechanical response of the composite, very few experimental measurements have been made of the local residual strains in Al-SiCw composites.The purpose of this investigation was to determine the magnitude of residual strains around individual whiskers in an Al-10 vol.% SiCw composite, which was annealed at 505°C and quenched to room temperature. Convergentbeam electron diffraction (CBED) was used for this investigation since all the information in a CBED pattern originates from a small area defined by the incident probe.

Space Group Determination of the Room-Temperature Phase ofα '-NaV2O5Using Convergent-Beam Electron Diffraction

2000 ◽  
Vol 69 (7) ◽  
pp. 1939-1941 ◽  
Author(s):  
Kenji Tsuda ◽  
Shuichi Amamiya ◽  
Michiyoshi Tanaka ◽  
Yukio Noda ◽  
Masahiko Isobe ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Room Temperature ◽  
Convergent Beam Electron Diffraction ◽  
Temperature Phase ◽  
Beam Electron ◽  
Space Group ◽  
Convergent Beam

Confirmation of the new technique for measuring the linear thermal expansion of silicon

1993 ◽  
Vol 8 (1) ◽  
pp. 36-38 ◽  
Author(s):  
Liu Fengchao
Keyword(s):  
Thermal Expansion ◽  
Room Temperature ◽  
Accurate Determination ◽  
Linear Thermal Expansion ◽  
Linear Expansion Coefficient ◽  
X Ray ◽  
High Purity Silicon ◽  
Different Temperatures ◽  
Better Than

This paper further confirms that the direct measurement of diffraction angles at different temperatures by using the X-ray diffractometer is better than measurement of the lattice parameters for the rapid and accurate determination of the linear thermal expansion of silicon. High purity silicon has the linear expansion coefficient, α= (2.45±0.05) × 10−6/°C at room temperature. This value does not change for doped P-type and N-type silicon.

scholarly journals Ab initio structure determination of nanocrystals of organic pharmaceutical compounds by electron diffraction at room temperature using a Timepix quantum area direct electron detector. Corrigendum

2018 ◽  
Vol 74 (6) ◽  
pp. 709-709 ◽  
Author(s):  
E. van Genderen ◽  
M. T. B. Clabbers ◽  
P. P. Das ◽  
A. Stewart ◽  
I. Nederlof ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Ab Initio ◽  
Structure Determination ◽  
Room Temperature ◽  
Pharmaceutical Compounds ◽  
Acta Cryst ◽  
Electron Detector ◽  
Ab Initio Structure

Corrections are made to Table 1 in the article by van Genderen et al. [Acta Cryst. (2016), A72, 236–242].

scholarly journals A Comparison of Structure Determination of Small Organic Molecules by 3D Electron Diffraction at Cryogenic and Room Temperature

Symmetry ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 2131
Author(s):  
Taimin Yang ◽  
Steve Waitschat ◽  
Andrew Kentaro Inge ◽  
Norbert Stock ◽  
Xiaodong Zou ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Data Collection ◽  
Data Quality ◽  
Structure Determination ◽  
Room Temperature ◽  
Organic Molecules ◽  
Small Organic Molecules ◽  
3D Electron ◽  
Cryogenic Conditions

3D electron diffraction (3D ED), also known as micro-crystal electron diffraction (MicroED), is a rapid, accurate, and robust method for structure determination of submicron-sized crystals. 3D ED has mainly been applied in material science until 2013, when MicroED was developed for studying macromolecular crystals. MicroED was considered as a cryo-electron microscopy method, as MicroED data collection is usually carried out in cryogenic conditions. As a result, some researchers may consider that 3D ED/MicroED data collection on crystals of small organic molecules can only be performed in cryogenic conditions. In this work, we determined the structure for sucrose and azobenzene tetracarboxylic acid (H4ABTC). The structure of H4ABTC is the first crystal structure ever reported for this molecule. We compared data quality and structure accuracy among datasets collected under cryogenic conditions and room temperature. With the improvement in data quality by data merging, it is possible to reveal hydrogen atom positions in small organic molecule structures under both temperature conditions. The experimental results showed that, if the sample is stable in the vacuum environment of a transmission electron microscope (TEM), the data quality of datasets collected under room temperature is at least as good as data collected under cryogenic conditions according to various indicators (resolution, I/σ(I), CC1/2 (%), R1, Rint, ADRA).

Post-Weld Heat Treatment Stress Relaxation in Zircaloy 4 Plasma Welds

2006 ◽  
Vol 524-525 ◽  
pp. 491-496 ◽  
Author(s):  
Javier R. Santisteban ◽  
L. Fernández ◽  
H. Corso ◽  
R.L. Martínez ◽  
L. Boccanera ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Room Temperature ◽  
Longitudinal Direction ◽  
Post Weld Heat Treatment ◽  
Steady Increase ◽  
Compressive Stresses ◽  
Heat Treated ◽  
Residual Strains ◽  
Weld Heat

We have studied the effect of a post-weld heat treatment on plasma arc welds on Zircaloy 4 plates. The samples consist of two 100 mm long, 50 mm wide, and 6.25 mm thick plates, welded along the rolling (longitudinal) direction. The heat-treatment consisted of a steady increase in temperature from room temperature to 450oC over a period of 4.5 hours; followed by cooling with an equivalent cooling rate. Residual strains and stresses along the longitudinal, transverse and normal directions on an as-welded and a heat-treated specimen were measured by neutron diffraction on the ENGIN-X beamline at the Isis Facility, Rutherford Laboratory, UK. Peak tensile stresses of (105±25) MPa were found in the as-welded specimen, which were reduced to (70±20) MPa after the heat-treatment. Thermal compressive stresses of (-80±20) MPa were found along the normal direction, which were not affected by the heat treatment. The use of a full-pattern Rietveld refinement for the determination of bulk strains in Zircaloy specimens is also discussed.

Determination of crystal symmetry for Bi4Ti3O12-based ferroelectrics by using electron diffraction

2013 ◽  
Vol 46 (3) ◽  
pp. 798-800 ◽  
Author(s):  
Wanneng Ye ◽  
Chaojing Lu ◽  
Peng You ◽  
Kun Liang ◽  
Yichun Zhou
Keyword(s):  
Electron Diffraction ◽  
Room Temperature ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Space Groups ◽  
Electron Diffraction Technique ◽  
Convergent Beam

In recent years, inconsistent space groups of monoclinicB1a1 and orthorhombicB2cbhave been reported for the room-temperature ferroelectric phases of both Bi4Ti3O12and lanthanide-substituted Bi4Ti3O12. In this article, the electron diffraction technique is employed to unambiguously clarify the crystal symmetries of ferroelectric Bi4Ti3O12and Bi3.15Nd0.85Ti3O12single crystals at room temperature. All the reflections observed from the two crystals match well with those derived fromB1a1, but the observed reflections 010, 030, {\overline 2}10 and {\overline 2}30 should be forbidden in the case ofB2cb. This fact indicates that both the ferroelectrics are of the space groupB1a1 rather thanB2cb, which is confirmed by convergent-beam electron diffraction observations. On the basis of the monoclinic space groupB1a1, the lattice parameters of both the ferroelectrics were calculated by the Rietveld refinement of powder X-ray diffraction data.

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