Anisotropy of elastic modules of the planes of a hexagonal crystal and damage of titanium sheets

2021 ◽  
Vol 28 (3) ◽  
Keyword(s):  
Hexagonal Crystal ◽  
Elastic Modules

Origin of the alternate bright/dark contrast in HREM images of hexagonal crystals, particularly 6H-SiC

1993 ◽  
Vol 51 ◽  
pp. 914-915
Author(s):  
J.S. Bow ◽  
R.W. Carpenter ◽  
M.J. Kim
Keyword(s):  
High Resolution ◽  
Incident Beam ◽  
Hexagonal Crystal ◽  
Detailed Explanation ◽  
Similar Character ◽  
High Resolution Images ◽  
The Difference ◽  
Zigzag Shape ◽  
Hexagonal Crystals ◽  
Dark Contrast

A prominent characteristic of high-resolution images of 6H-SiC viewed from [110] is a zigzag shape with a period of 6 layers as shown in Fig.1. Sometimes the contrast is same through the 6 layers of (0006) planes (Fig.1a), but in most cases it appears as in Fig.1b -- alternate bright/dark contrast among every three (0006) planes. Alternate bright/dark contrast is most common for the thicker specimens. The SAD patterns of these two types of image are almost same, and there is no indication that the difference results from compositional ordering. O’Keefe et al. concluded this type of alternate contrast was due to crystal tilt in thick parts of the specimen. However, no detailed explanation was given. Images of similar character from Ti3Al, which is also a hexagonal crystal, were reported by Howe et al. Howe attributed the bright/dark contrast among alternate (0002) Ti3Al planes to phase shifts produced by incident beam tilt.

The crystallography characteristic of (Mn,Fe)S single crystal

1990 ◽  
Vol 48 (4) ◽  
pp. 898-899
Author(s):  
Jiang Xishan
Keyword(s):  
Single Crystal ◽  
Cast Steel ◽  
Point Group ◽  
Central Area ◽  
Hexagonal Crystal ◽  
Growth Step ◽  
Left And Right ◽  
Relationship Of ◽  
Fcc Structure ◽  
New Discovery

This paper reports the growth step pattern and morphology at equilibrium and growth states of (Mn,Fe)S single crystal on the wall of micro-voids in ZG25 cast steel by using scanning electron microscope. Seldom report was presented on the growth morphology and steppattern of (Mn,Fe)S single crystal.Fig.1 shows the front half of the polyhedron of(Mn,Fe)S single crystal,its central area being the square crystal plane,the two pairs of hexagons symmetrically located in the high and low, the left and right with a certain, angle to the square crystal plane.According to the symmetrical relationship of crystal, it was defined that the (Mn,Fe)S single crystal at equilibrium state is tetrakaidecahedron consisted of eight hexagonal crystal planes and six square crystal planes. The macroscopic symmetry elements of the tetrakaidecahedron correpond to Oh—n3m symmetry class of fcc structure,in which the hexagonal crystal planes are the { 111 } crystal planes group,square crystal plaits are the { 100 } crystal planes group. This new discovery of the (Mn,Fe)S single crystal provides a typical example of the point group of Oh—n3m.

Pharmaceutico- Analytical Study of Abhra Sindoora

2018 ◽  
Vol 3 (4) ◽  
Author(s):  
Dr. Jyothi B. ◽  
Dr. M. V. Sobagin ◽  
Dr. M.C. Patil
Keyword(s):  
Analytical Study ◽  
Current Trend ◽  
Drug Analysis ◽  
Sem Analysis ◽  
Secondary Amines ◽  
Particle Analysis ◽  
Hexagonal Crystal ◽  
Xrd Study ◽  
Edxrf Analysis ◽  
Working Standards

Background: Abhra Sindoora[1] (ABS) is a unique Rasa Yoga with having more potent and indication in Tridoshahara, Swasa, Kasa etc. It is one of the important classical Kupipakva Rasayana containing Hingulotha Parada (purified mercury), Shuddha Gandhaka (purified sulfur) and Dhanyabhraka in 1:1:1 proportion. Aim: Pharmaceutico-Analytical study of Abhra Sindoora. Materials and Methods: Hingulotha Parada (purified mercury), Shuddha Gandhaka (purified sulfur) and Dhanyabhraka are used to prepare Kajjali and lavigated with Vatankura (leaf buds of Ficus bengalensis), Swarasa (juice) and Arka (Calotrapis procera) ksheera (milk). This Kajjali is processed by Kupipakva method. Results and Conclusion: The current trend in applied instrumental medical research encourages good medical practice, clinical and research based drug analysis. The main aim of analytical study is to find out working standards for the formulations and safe use of therapeutics. Abhra Sindoora was prepared in 48 hours with 28% yield. It was also characterized by using modern instrumental analysis like XRD, SEMEDX, EDXRF, FTIR and PARTICLE ANALYSIS. The SEM analysis evaluated that prepared Abhra Sindoora has particles in nanometers, least being 14.87nm. SEMEDX study confirmed the presence of C, O, Si, S, K, and HgM. XRD study confirmed the presence of Hg3.00S3.00 in hexagonal crystal system. The EDXRF analysis evaluated the presence of K, Ca, Ti, Mn, Fe, S, Br and Hg. FTIR analysis shows organic compounds with functional groups like secondary amines, Nitro, Carboxylic acids, Bromine, Esters, Alkines, and Iodides etc.

Precipitation Upon Hot Strip Mill Conditions of a Ti-IF Steel

2001 ◽  
Vol 7 (S2) ◽  
pp. 508-509
Author(s):  
W. Regone ◽  
A. M. 𝚓orge Júnior ◽  
O. Balancin
Keyword(s):  
Hot Strip Mill ◽  
Interstitial Free ◽  
If Steel ◽  
Precipitation Sequence ◽  
Hexagonal Crystal Structure ◽  
Hexagonal Crystal ◽  
Hot Strip ◽  
Hot Torsion ◽  
And Diffusion ◽  
Interstitial Elements

Upon hot strip mill of titanium Interstitial Free (IF) steels, during cooling from austenite to ferrite region, the level of interstitial elements not removed by steelmaking process is dropped down by Ti that combines with N, C and S. Some authors [1-3] have reported that the traditional precipitation sequence TiN, TiS, Ti4C2S2 and TiC occurs with freestanding particles formed by nucleation and growth processes. Other authors [4] have indicated that the transformation from TiS to Ti4C2S2 may be considered as a hybrid of shear and diffusion, i.e., faulted Ti8S9 (9R) + 10[Ti] + 9[C] → 41/2Ti4C2S2 (or H for its hexagonal crystal structure). At low temperature (≤930°C), the stabilization process continues through epitaxial growth of carbides on H phase. to study the evolution of precipitation upon hot strip mill conditions, samples of a Ti - IF steel were subjected to double straining tests [5] by means of a computerized hot torsion machine, at 1000 °C and 920 °C, with strain rate of 1 s-1 and interpass times ranging from 0.5 to 100 s.

scholarly journals Two-dimensional mobile breather scattering in a hexagonal crystal lattice

2021 ◽  
Vol 103 (2) ◽  
Author(s):  
Jānis Bajārs ◽  
J. Chris Eilbeck ◽  
Benedict Leimkuhler
Keyword(s):  
Crystal Lattice ◽  
Two Dimensional ◽  
Hexagonal Crystal

Crystallographic Origin of the Alternate Bright/Dark Contrast in 6H-SiC and other Hexagonal Crystal HREM Images

1996 ◽  
Vol 2 (2) ◽  
pp. 63-78
Author(s):  
J.S. Bow ◽  
R.W. Carpenter ◽  
M.J. Kim
Keyword(s):  
Crystal Thickness ◽  
Material System ◽  
Hrem Image ◽  
Hexagonal Crystal ◽  
Cubic Crystals ◽  
Unit Cells ◽  
Crystal Model ◽  
Scattering Potential ◽  
Diffraction Patterns ◽  
Image Simulations

Alternating bright/dark anomalous subunitcell contrast in HREM images along or near the close-packed direction of 6H-SiC, Ti5Si3, α-Ti, and 4H-SiC, all of which are hexagonal, was examined using computer-generated crystal models, HREM image simulations, and digital diffractograms from the corresponding experimental images. The primary variables were crystal tilt and thickness. Crystal model projections showed that the scattering potential was smeared anisotropically within the unit cells by small crystal tilts, which reproduced the experimentally observed anomalous subunit-cell contrast modulations in the corresponding simulations. The effect increased with thickness, but it did not occur in exact zone axis simulations for any crystal thickness. Structural considerations indicated that the contrast resulted from tilt-induced violations of Gjonnes-Moodie dynamical extinctions and excitation of kinematically forbidden reflections in the imaging zone. Digital diffractograms from experimental HREM images confirmed their presence in the imaging zone diffraction patterns. These effects were absent in HREM images from cubic crystals in this material system because the structurally induced requisite kinematically forbidden reflections do not occur in the imaging zone.

scholarly journals Threading Dislocations Piercing the Free Surface of an Anisotropic Hexagonal Crystal: Review of Theoretical Approaches

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Salem Neily ◽  
Sami Dhouibi ◽  
Roland Bonnet
Keyword(s):  
Free Surface ◽  
Fourier Series ◽  
Dislocation Core ◽  
Surface Region ◽  
Double Fourier Series ◽  
Threading Dislocations ◽  
Core Size ◽  
Hexagonal Crystal ◽  
Integral Formalism ◽  
Theoretical Approaches

Inclined threading dislocations (TDs) piercing the oriented free surface of a crystal are currently observed after growth of oriented thin films on substrates. Up to date the unique way to treat their anisotropic elastic properties nearby the free surface region is to use the integral formalism, which assumes no dislocation core size and needs numerical double integrations. In a first stage of the work, a new and alternative approach to the integral formalism is developed using double Fourier series and the concept of a finite core size, which is often observed in high-resolution transmission electron microscopy. In a second stage, the integral formalism and the Fourier series approaches are applied to the important case of a TD piercing the basal free surface of a hexagonal crystal. For this particular geometry, easy-to-use expressions are derived and compared to a third approach previously known for a plate-like crystal. Finally, the numerical interest and the convergence of these approaches are tested using the basal free surface of the GaN compound, in particular for TDs with Burgers vectors c and (a + c).

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