The Growth and Perfection of Single Crystals of Trinitrotoluene (TNT)

1992 ◽  
Vol 296 ◽  
Author(s):  
Hugh G. Gallagher ◽  
John N. Sherwood
Keyword(s):  
Stacking Faults ◽  
Acetate Solution ◽  
Ethyl Acetate Solution ◽  
Growth Behaviour ◽  
Seeded Growth ◽  
Burgers Vector ◽  
X Ray ◽  
Monoclinic Form ◽  
Growth Defects ◽  
Residual Growth

AbstractA study has been made of the crystal growth behaviour and perfection of TNT. Depending on the purity and the solvent used, crystallisation from solution yields material of monoclinic, twinned monoclinic or orthorhombic forms. Of these only the monoclinic form was suitable for detailed study by X-ray topographic techniques. The crystals of the orthorhombic form were too small and imperfect for examination.Seeded growth from ethyl acetate solution yielded lamellar twinned crystals in which the twin density was low. Under ideal conditions, relatively perfect samples could be obtained in which the dominant residual growth defects were stacking faults of Burgers vector b ½ [001] and dislocations.

Dislocations in YBa2Cu3O7−δ (δ = 0.77)

1990 ◽  
Vol 48 (4) ◽  
pp. 72-73
Author(s):  
Yimei Zhu ◽  
Hong Zhang ◽  
A.R. Moodenbaugh ◽  
M. Suenaga
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Displacement Vector ◽  
Stacking Faults ◽  
Spot Size ◽  
Convergent Beam Electron Diffraction ◽  
Burgers Vector ◽  
Beam Electron ◽  
X Ray ◽  
Convergent Beam

Abundant dislocations and dislocations associated with stacking faults were observed and characterized in YBa2Cu3O7−δ (δ= 0.77). The crystallographic orientation of the dislocation and the fault were analyzed using Kikuchi patterns matched with computer generated Kikuchi maps. The Burgers vector of the dislocation and the displacement vector of the fault were determined by using the g·b = 0 and g · R=0 criteria.Bulk samples of YBa2Cu3O7 were produced by standard pressing and sintering up to 970 °C. Samples were heated in air, then quenched into liquid nitrogen to reduce oxygen content. Subsequent anneal at 200 ° C took place with samples sealed in silica with 1/2 atm. of argon. TEM specimens were thinned by ion mill and examined in a JEOL 2000FX electron microscope operating at 200kv.X-ray powder diffraction and convergent beam electron diffraction with 200 Å spot size show that YBa2Cu3O6.23 has a tetragonal structure.

Direct Observation of Stacking Fault Nucleation from Deflected Threading Dislocations with Burgers Vector c+a in PVT Grown 4H-SiC

2014 ◽  
Vol 1693 ◽  
Author(s):  
Fangzhen Wu ◽  
Huanhuan Wang ◽  
Balaji Raghothamachar ◽  
Michael Dudley ◽  
Stephan G. Mueller ◽  
...  
Keyword(s):  
Direct Observation ◽  
Basal Plane ◽  
Stacking Faults ◽  
Stacking Fault ◽  
Formation Mechanisms ◽  
Threading Dislocations ◽  
Burgers Vector ◽  
X Ray ◽  
Transmission Geometry ◽  
Made In

ABSTRACTIn our previous studies [1-3], four kinds of stacking faults in 4H-SiC bulk crystal have been distinguished based on their contrast behavior differences in synchrotron white beam x-ray topography images. These faults are Shockley faults, Frank faults, Shockley plus c/2 Frank faults, and Shockley plus c/4 Frank faults. Our proposed formation mechanisms for these stacking faults involve the overgrowth of the surface outcrop associated with threading screw dislocations (TSDs) or threading mixed dislocations (TMDs) with Burgers vector of c+a by macrosteps and the consequent deflection of TSDs or TMDs onto the basal plane. Previous synchrotron x-ray topography observations were made in offcut basal wafers using transmission geometry. In this paper, further evidence is reported to confirm the proposed stacking fault formation mechanism. Observations are made in axially cut slices with surface plane {11-20}. Several kinds of stacking faults are recognized and their contrast behavior agrees with the four kinds previously reported. Direct observation is obtained of a Shockley plus c/4 Frank stacking fault nucleating from a TMD deflected onto the basal plane. The contrast from stacking faults on the basal plane in the axial slices is enhanced by recording images after rotating the crystal about the active -1010 reflection vector enabling a broader projection of the basal plane.

Deflection of Threading Dislocations with Burgers Vector c/c+a Observed in 4H-SiC PVT–Grown Substrates with Associated Stacking Faults

2012 ◽  
Vol 717-720 ◽  
pp. 347-350 ◽  
Author(s):  
Sha Yan Byrapa ◽  
Fang Zhen Wu ◽  
Huan Huan Wang ◽  
Balaji Raghothamachar ◽  
Gloria Choi ◽  
...  
Keyword(s):  
Detailed Analysis ◽  
Basal Plane ◽  
Stacking Faults ◽  
Image Contrast ◽  
Threading Dislocations ◽  
Burgers Vector ◽  
Calculated Phase ◽  
X Ray ◽  
White Beam ◽  
Contrast Studies

A review is presented of Synchrotron White Beam X-ray Topography (SWBXT) studies of stacking faults observed in PVT-Grown 4H-SiC crystals. A detailed analysis of various interesting phenomena were performed and one such observation is the deflection of threading dislocations with Burgers vector c/c+a onto the basal plane and associated stacking faults. Based on the model involving macrostep overgrowth of surface outcrops of threading dislocations, SWBXT image contrast studies of these stacking faults on different reflections and comparison with calculated phase shits for postulated fault vectors, has revealed faults to be of basically four types: (a) Frank faults; (b) Shockley faults; (c) Combined Shockley + Frank faults with fault vector s+c/2; (d) Combined Shockley + Frank faults with fault vector s+c/4.

Synthesis and X-ray diffraction data of 1-N-(3-pyridylmethyl)aminonaphthalene hydrochloride

2014 ◽  
Vol 29 (2) ◽  
pp. 186-189
Author(s):  
L.R. Morantes ◽  
C.F. Medina ◽  
J.A. Henao ◽  
V.V. Kouznetsov ◽  
H.A. Camargo
Keyword(s):  
Hydrochloric Acid ◽  
Anhydrous Methanol ◽  
Acetate Solution ◽  
Ethyl Acetate Solution ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Monoclinic System ◽  
Polycrystalline Solid ◽  
X Ray ◽  
Cell Parameters

The title compound 1-N-(3-pyridylmethyl)aminonaphthalene hydrochloride (C16H15N2Cl) was obtained by a reaction of α-naphthylamine (1) and N-pyridincarboxaldehyde (2) in anhydrous ethanol in the first step. The formed imine (3) was reduced with sodium borohydride in anhydrous methanol to give the product 1-N-(3-pyridylmethyl)aminonaphthalene (4). Finally, the hydrochloride was prepared by addition of a hydrochloric acid–ethyl acetate solution (ratio 1:3) with constant stirring and maintaining the temperature between 0 and 5 °C, obtaining a yellow polycrystalline solid corresponding to the respective derivative (5). The X-ray powder diffraction pattern for the new compound (5) was obtained. The compound (5) crystallizes in a monoclinic system with the space group P21/m (No. 11) and refined unit-cell parameters: a = 16.257 (8) Å, b = 9.236 (7) Å, c = 13.221 (6) Å, β = 94.87° (5), Z = 6, and V = 1978 (1) Å3.

Formation Mechanism of Stacking Faults in PVT 4H-SiC Created by Deflection of Threading Dislocations with Burgers Vector c+a

2011 ◽  
Vol 679-680 ◽  
pp. 269-272 ◽  
Author(s):  
Michael Dudley ◽  
Huan Huan Wang ◽  
Fang Zhen Wu ◽  
Sha Yan Byrapa ◽  
Balaji Raghothamachar ◽  
...  
Keyword(s):  
Stacking Faults ◽  
Growth Conditions ◽  
Vapor Transport ◽  
Physical Vapor Transport ◽  
Threading Dislocations ◽  
Stress Growth ◽  
Burgers Vector ◽  
X Ray ◽  
Dislocation Behavior ◽  
New Generation

Synchrotron White Beam X-ray Topography studies are presented of dislocation behavior and interactions in a new generation of seventy-six millimeter diameter, 4H-SiC wafers grown using Physical Vapor Transport under specially designed low stress conditions. Such low stress growth conditions have enabled reductions of dislocation density by two or three orders of magnitude compared to the lowest previously reported levels [1]. In this paper, detailed topography analysis will be presented of the deflection of threading dislocations with Burgers vectors of c and c+a onto the basal plane leading to reductions of the density of such dislocations down to levels of ~187 cm-2. The deflection of the latter type of dislocations produces complex faulted defect configurations and models for their creation are presented and discussed.

Synthesis and X-Ray Crystal Structure Analysis of 1,4-Epoxy-4-methyl- 1H,4H-2,3-benzodioxepin

2011 ◽  
Vol 66 (4) ◽  
pp. 419-424
Author(s):  
David S. Giera ◽  
Lothar Hennig ◽  
Thomas Gelbrich ◽  
Christoph Schneider
Keyword(s):  
Crystal Structure ◽  
Structure Analysis ◽  
Crystal Structure Analysis ◽  
Acetate Solution ◽  
Enantiomerically Pure ◽  
X Ray ◽  
Monoclinic Form ◽  
Secondary Ozonide ◽  
Orthorhombic Modification ◽  
Polymorphic Forms

Ozonolysis of 2-methyl-1H-indene (1) afforded the stable secondary ozonide 1,4-epoxy-4-methyl- 1H,4H-2,3-benzodioxepin (2). This compound crystallizes in two polymorphic forms, depending on the solvent used. The monoclinic form 2a containing two symmetry-independent molecules (enantiomers) is obtained by crystallization from dichloromethane. In contrast, the orthorhombic modification 2b is obtained from ethyl acetate solution and crystallizes as a conglomerate of enantiomerically pure single crystals. Additionally, the ring-opened product 2-(2-oxopropyl)benzoic acid (3) was obtained and investigated by X-ray crystal structure analysis.

Defect structures of Nb1+αS2 sulfidation scales

1992 ◽  
Vol 50 (1) ◽  
pp. 38-39
Author(s):  
Chuxin Zhou ◽  
L. W. Hobbs
Keyword(s):  
Stacking Faults ◽  
Rhombohedral Structure ◽  
Stacking Sequence ◽  
Defect Structures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Plane Normal ◽  
Lower Case ◽  
Sulfur Layer ◽  
Two Phases

One of the major purposes in the present work is to study the high temperature sulfidation properties of Nb in severe sulfidizing environments. Kinetically, the sulfidation rate of Nb is satisfactorily slow, but the microstructures and non-stoichiometry of Nb1+αS2 challenge conventional oxidation/sulfidation theory and defect models of non-stoichiometric compounds. This challenge reflects our limited knowledge of the dependence of kinetics and atomic migration processes in solid state materials on their defect structures.Figure 1 shows a high resolution image of a platelet from the middle portion of the Nb1+αS2 scale. A thin lamellar heterogeneity (about 5nm) is observed. From X-ray diffraction results, we have shown that Nb1+αS2 scale is principally rhombohedral structure, but 2H-NbS2 can result locally due to stacking faults, because the only difference between these 2H and 3R phases is variation in the stacking sequence along the c axis. Following an ABC notation, we use capital letters A, B and C to represent the sulfur layer, and lower case letters a, b and c to refer to Nb layers. For example, the stacking sequence of 2H phase is AbACbCA, which is a ∼12Å period along the c axis; the stacking sequence of 3R phase is AbABcBCaCA to form an ∼18Å period along the c axis. Intergrowth of these two phases can take place at stacking faults or by a shear in the basal plane normal to the c axis.

scholarly journals Structure of aqueous sodium acetate solutions by X-Ray scattering and density functional theory

2020 ◽  
Vol 92 (10) ◽  
pp. 1627-1641
Author(s):  
Guangguo Wang ◽  
Yongquan Zhou ◽  
He Lin ◽  
Zhuanfang Jing ◽  
Hongyan Liu ◽  
...  
Keyword(s):  
Sodium Acetate ◽  
Density Functional ◽  
Hydration Shell ◽  
Ion Pair ◽  
Water Molecules ◽  
Sodium Acetate Solution ◽  
Acetate Solution ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

AbstractThe structure of aq. sodium acetate solution (CH3COONa, NaOAc) was studied by X-ray scattering and density function theory (DFT). For the first hydrated layer of Na+, coordination number (CN) between Na+ and O(W, I) decreases from 5.02 ± 0.85 at 0.976 mol/L to 3.62 ± 1.21 at 4.453 mol/L. The hydration of carbonyl oxygen (OC) and hydroxyl oxygen (OOC) of CH3COO− were investigated separately and the OC shows a stronger hydration bonds comparing with OOC. With concentrations increasing, the hydration shell structures of CH3COO− are not affected by the presence of large number of ions, each CH3COO− group binds about 6.23 ± 2.01 to 7.35 ± 1.73 water molecules, which indicates a relatively strong interaction between CH3COO− and water molecules. The larger uncertainty of the CN of Na+ and OC(OOC) reflects the relative looseness of Na-OC and Na-OOC ion pairs in aq. NaOAc solutions, even at the highest concentration (4.453 mol/L), suggesting the lack of contact ion pair (CIP) formation. In aq. NaOAc solutions, the so called “structure breaking” property of Na+ and CH3COO− become effective only for the second hydration sphere of bulk water. The DFT calculations of CH3COONa (H2O)n=5–7 clusters suggest that the solvent-shared ion pair (SIP) structures appear at n = 6 and become dominant at n = 7, which is well consistent with the result from X-ray scattering.

scholarly journals Dislocation Arrangement in a Thick LEO GaN Film on Sapphire

2000 ◽  
Vol 5 (S1) ◽  
pp. 97-103
Author(s):  
Kathleen A. Dunn ◽  
Susan E. Babcock ◽  
Donald S. Stone ◽  
Richard J. Matyi ◽  
Ling Zhang ◽  
...  
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Threading Dislocations ◽  
X Ray Diffraction ◽  
Burgers Vector ◽  
X Ray ◽  
The Third ◽  
Dislocation Arrangement ◽  
Image Position ◽  
Gan Film

Diffraction-contrast TEM, focused probe electron diffraction, and high-resolution X-ray diffraction were used to characterize the dislocation arrangements in a 16µm thick coalesced GaN film grown by MOVPE LEO. As is commonly observed, the threading dislocations that are duplicated from the template above the window bend toward (0001). At the coalescence plane they bend back to lie along [0001] and thread to the surface. In addition, three other sets of dislocations were observed. The first set consists of a wall of parallel dislocations lying in the coalescence plane and nearly parallel to the substrate, with Burgers vector (b) in the (0001) plane. The second set is comprised of rectangular loops with b = 1/3 [110] (perpendicular to the coalescence boundary) which originate in the coalescence boundary and extend laterally into the film on the (100). The third set of dislocations threads laterally through the film along the [100] bar axis with 1/3<110>-type Burgers vectors These sets result in a dislocation density of ∼109 cm−2. High resolution X-ray reciprocal space maps indicate wing tilt of ∼0.5º.

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