scholarly journals Single crystal investigation of the YbAl2 compound

2019 ◽  
Vol 85 (9) ◽  
pp. 25-30
Author(s):  
Mykola Manyako ◽  
Dorota Kowalska ◽  
Bohdana Belan ◽  
Roman Gladyshevskii
Keyword(s):  
High Efficiency ◽  
Cold Water ◽  
Structure Type ◽  
Nominal Composition ◽  
Quartz Ampoule ◽  
Tungsten Electrode ◽  
Cubic Symmetry ◽  
Trivalent State ◽  
Diffraction Patterns ◽  
Integrated Intensities

A sample of nominal composition Yb33,3Al66,7 was synthesized from high-purity elements (Yb ≥ 98.9 wt.% and Al ≥ 99.999 wt.%) by arc-melting under a purified argon atmosphere, using Ti as a getter and a tungsten electrode. To achieve high efficiency of the interaction between the components, the sample was melted twice. The ingot was annealed at 500°C in an evacuated quartz ampoule for 720 h and subsequently quenched in cold water. The weight loss during the preparation of the sample was less than 1 % of the total mass, which was 2 g. The chemical composition of the selected crystals was checked with a field-emission scanning electron microscope (FEINovaNanoSEM 230) equipped with an EDS analyzer. Laue and rotation diffraction patterns of selected single crystals showed cubic symmetry. Integrated intensities measured with graphite-monochromatized Мо Kα radiation (l = 0.71073 Å) on an Xcalibur Atlas CCD diffractometer confirmed the cubic lattice. The structure type MgCu2 was assigned and the structure was refined using the program SHELXL (full-matrix least-squares refinement on F2)] with anisotropic displacement parameters for all of the atoms: Pearson symbol cF24, space group Fd-3m, a = 7.7011(4) Å, V = 456.73(7) Å3, Z = 8, R = 0.0261, Rw = 0.0726 for 42 reflections. It is well-known that the trivalent state is usual one for the rare earth metals. The dependence of the mean atomic volume of the RAl2 binary showed of the so-called “valence” fluctuation state for Eu and Yb.

X-Ray Powder Diffraction Data and Crystal Refinement of a New Compound AlCrNi3Pr

2016 ◽  
Vol 850 ◽  
pp. 3-7
Author(s):  
Shu Hui Liu ◽  
Liu Qing Liang ◽  
Chang Sheng Qin ◽  
De Gui Li ◽  
Ling Min Zeng ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Structure Type ◽  
Hexagonal Structure ◽  
Powder Diffraction Data ◽  
Tungsten Electrode ◽  
X Ray ◽  
Diffraction Patterns

Rare earth-transition metal (R-T) intermetallics have been well used because of their excellent properties. The X-ray diffraction patterns of many new phases in the R-T system have not been extensively studied. A new compound AlCrNi3Pr was prepared by arc melting using non-consumable tungsten electrode under argon atmosphere, and then annealed at 1023K for 30 days. The X-ray powder diffraction data of AlCrNi3Pr was collected on a Rigaku SmartLab X-ray powder diffractometer. The powder patterns of the compound were indexed, and the structure refinement by using Rietveld method indicated that the AlCrNi3Pr compound crystallized in the hexagonal structure, space group P6/mmm (No.191) with PrNi5 structure type, a=b=5.0553(9) Ǻ, c=4.0763(6) Ǻ, V=90.22Ǻ3, Z=1, ρx=7.288g cm-3, the Smith–Snyder FOM F30=279.1(0.0044, 32) and the intensity ratio RIR=1.23.

Deviations from Ideal Decagonal Symmetry in Electron Diffraction Patterns of the “Decagonal” Phase in the Al-Co-Cu Alloy System

1991 ◽  
Vol 49 ◽  
pp. 914-915
Author(s):  
Atul S. Ramani ◽  
Earle R. Ryba ◽  
Paul R. Howell
Keyword(s):  
Electron Microscope ◽  
Alloy System ◽  
Nominal Composition ◽  
Dimensional Lattice ◽  
3 Dimensional ◽  
Decagonal Phase ◽  
Cu Alloy ◽  
Transmission Electron ◽  
Lattice Periodicity ◽  
Diffraction Patterns

The “decagonal” phase in the Al-Co-Cu system of nominal composition Al65CO15Cu20 first discovered by He et al. is especially suitable as a topic of investigation since it has been claimed that it is thermodynamically stable and is reported to be periodic in the dimension perpendicular to the plane of quasiperiodic 10-fold symmetry. It can thus be expected that it is an important link between fully periodic and fully quasiperiodic phases. In the present paper, we report important findings of our transmission electron microscope (TEM) study that concern deviations from ideal decagonal symmetry of selected area diffraction patterns (SADPs) obtained from several “decagonal” phase crystals and also observation of a lattice of main reflections on the 10-fold and 2-fold SADPs that implies complete 3-dimensional lattice periodicity and the fundamentally incommensurate nature of the “decagonal” phase. We also present diffraction evidence for a new transition phase that can be classified as being one-dimensionally quasiperiodic if the lattice of main reflections is ignored.

Characterization of image plates for neutron diffraction

2009 ◽  
Vol 42 (5) ◽  
pp. 749-757 ◽  
Author(s):  
Clive Wilkinson ◽  
Mogens S. Lehmann ◽  
Flora Meilleur ◽  
Matthew P. Blakeley ◽  
Dean A. A. Myles ◽  
...  
Keyword(s):  
Point Spread Function ◽  
X Rays ◽  
Image Plate ◽  
Point Spread ◽  
Spread Function ◽  
Luminescent Signal ◽  
Diffraction Patterns ◽  
Integrated Intensities ◽  
Ccd Detectors ◽  
Lower Limits

A method to measure the overall gain and point-spread function of an image-plate detector system (converter, phosphor, readout electronics) online from single-crystal diffraction patterns is derived. Only with a knowledge of these quantities can one estimate without bias the true standard deviations of the observed integrated intensities of Bragg reflections measured with such a detector. The gain corrected for the point-spread function should ideally be approximately 1.0 to avoid loss of data or precision due to the upper and lower limits of digitization of the diffraction patterns. The gain and the point-spread function are derived for several configurations of the three neutron Laue image-plate diffractometers, LADI, VIVALDI and LADI-III, at the Institut Laue–Langevin. The detective quantum efficiencies (DQE) of these instruments have been measured to be 0.16 (1), 0.57 (2) and 0.46 (3), respectively. It has also been found that the DQE is effectively constant for different times of exposure, despite the fading of the photostimulated luminescent signal during that time. While the results described in this paper concern neutron detection by image plates, the method is equally valid for other integrating detectors and radiations,e.g.CCD detectors and X-rays.

scholarly journals Research and Development of a Novel TIG Welding Torch for Joining Thin Sheets

2019 ◽  
Vol 9 (23) ◽  
pp. 5260 ◽  
Author(s):  
Ngo Huu Manh ◽  
Nguyen Van Anh ◽  
Nguyen Van Tuan ◽  
Bin Xu ◽  
Murata Akihisa
Keyword(s):  
Welding Current ◽  
Optical Microscope ◽  
Electron Back Scatter Diffraction ◽  
Weld Bead ◽  
Tig Welding ◽  
Bottom Surface ◽  
Thin Sheets ◽  
Tungsten Electrode ◽  
Welding Torch ◽  
Diffraction Patterns

This paper aims to develop a novel tungsten inner gas (TIG) welding torch in order to join thin sheets efficiently. Using a narrowing nozzle (constricted nozzle) inside a conventional TIG torch can critically improve the position accuracy of the tungsten electrode and also the arc plasma characteristics and heat input density. In order to evaluate the efficiency of this new torch, weld bead appearance and cross-section images were examined by an optical microscope, scanning electron microscope (SEM), and electron back scatter diffraction patterns (EBSD). The results showed that in all cases, the weld bead profile was stable without undercut and burn-through. Full penetration weld was seen. The width of weld bead on the bottom surface was increased much in comparison to conventional TIG welding. However, the results from SEM and EBSD images indicated that in the case of low welding current, the blowholes were found out on the side of the thinner material (SS400). The penetration of SUS430 material to SS400 material was not good. It seems that no fusion of SUS430 material to SS400 at the bottom surface can be seen. Meanwhile, no blowholes were seen in the case of high welding current. The penetration was better, and the fusion was reached on the bottom surface.

X-ray powder diffraction study of K2MSiO4, M=Mg, Zn, Co, Cd

1996 ◽  
Vol 11 (1) ◽  
pp. 51-55 ◽  
Author(s):  
W. A. Dollase
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Site Occupancy ◽  
Cubic Phase ◽  
Variable Degree ◽  
Cubic Symmetry ◽  
X Ray ◽  
Constrained Model ◽  
Diffraction Patterns

The title materials are stuffed cristobalites possessing moderate to extreme pseudosymmetry. On the bases of their X-ray powder diffraction patterns, the Mg, Zn, and Cd compounds had been previously reported as cubic and, more recently, the Zn phase as orthorhombic. Newly measured X-ray powder diffraction data demonstrate that all (including the hitherto unknown Co analog) have the Pca21 structure of Na2BeSiO4 at room temperature, but with a widely variable degree of cubic pseudosymmetry. Observed X-ray diffraction data are in good agreement with those calculated by the Rietveld method using a constrained model with Pca21 M2+/Si site occupancy and pseudocentrosymmetric Pcab atom locations. For the most nearly cubic phase, the Cd compound, there is too little deviation in the pattern from cubic symmetry to support atom coordinate refinement even with the constrained model. In these derivatives of the stuffed cristobalite structure family, M2+ and Si atoms form an ordered tetrahedral array which avoids M2+–O–M2+ connections. Potassium atoms fill all of the intervening large cavity sites.

Ca10V5.2Fe0.8O24, a Novel Oxometalate with Discrete Complex Anions

2003 ◽  
Vol 58 (11) ◽  
pp. 1112-1116 ◽  
Author(s):  
Kurt O. Kleppa ◽  
Norbert A. Harringer ◽  
Hubert Preßlinger
Keyword(s):  
Crystal Structure ◽  
Single Crystals ◽  
Bond Distance ◽  
Structure Type ◽  
The Other ◽  
Nominal Composition ◽  
Average Bond ◽  
Complex Anions ◽  
Trigonal Prismatic ◽  
Discrete Complex

Abstract Lustrous needle shaped prismatic single crystals of the new compound Ca10V5.2Fe0.8O24 were obtained out of a sample with nominal composition Ca2Fe1.6V0.4O5 prepared at 1400 °C. The crystals are opaque and stable to humid air. Ca10V5.2Fe0.8O24 crystallizes with a new structure type, space group Pnma with a = 6.803(3), b = 16.015(8), c = 10.418(7)Å , Z = 2, R = 0.041. The crystal structure is characterized by two mononuclear tetrahedral species, MO4, which differ significantly from each other with respect to their M-O bond lengths. One with an average bond distance of 1.709(8)Å represents an orthovanadate ion. The other with a significantly larger value d(M-O) = 1.744(6) Å corresponds to a mixed occupation of its centre according to [V0.8Fe0.2O4]3.5−. In the crystal structure the complex anions are arranged in separate sheets parallel to the (010) plane. They are separated from each other by three crystallographically independent Ca2+ ions which are each coordinated by 7 oxygen atoms in distorted pentagonal bipyramidal and trigonal prismatic configurations, respectively.

X-Ray Powder Diffraction Data and Crystal Refinement of Ternary Compound Ti4ZrSi3

2020 ◽  
Vol 841 ◽  
pp. 99-102
Author(s):  
Liu Qing Liang ◽  
Yan Ying Wei ◽  
De Gui Li
Keyword(s):  
Ternary Compound ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Structure Type ◽  
Hexagonal Structure ◽  
Powder Diffraction Data ◽  
Tungsten Electrode ◽  
X Ray

Ternary compound Ti4ZrSi3 was prepared by arc melting using a non-consumable tungsten electrode under argon atmosphere, then annealed at 1023K for 30 days, the X-ray powder diffraction data of Ti4ZrSi3 was collected on a Rigaku SmartLab X-ray powder diffractometer. The powder patterns of the compound were indexed and structure refinement by using Rietveld method indicate that the Ti4ZrSi3 compound crystallizes in the hexagonal structure, space group P6/mcm (No.193) with Mn5Si3 structure type, a=b=7.5759(3) Ǻ, c=5.2162(2) Ǻ, V=259.28Ǻ3, Z=2, ρx=4.779g cm-3, the Smith–Snyder FOM F30=148.7(0.0064, 46) and the intensity ratio RIR=1.37. The Rietveld refinement results were Rp = 0.0836, Rwp= 0.1092.

Formation and Characteristics of Thin Films of ZrO2-8 mol % Y2O3 Solid Electrolytes

2004 ◽  
Vol 97-98 ◽  
pp. 153-158 ◽  
Author(s):  
Darius Milčius ◽  
L.L. Pranevičius ◽  
V. Širvinskaitė ◽  
T. Šalkus ◽  
A. Kežionis ◽  
...  
Keyword(s):  
Thin Films ◽  
Solid Electrolytes ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
Dc Magnetron Sputtering ◽  
Cubic Symmetry ◽  
X Ray ◽  
Pulsed Dc ◽  
Pulsed Dc Magnetron Sputtering ◽  
Diffraction Patterns

Thin films of ZrO2-8mol%Y2O3 have been deposed by pulsed DC magnetron sputtering method. The substrates of Ni-cermet and alloy-600 for the films were used. The results of the investigation of the X-ray diffraction patterns and SEM showed that the films are nanocrystalline and belong to cubic symmetry. The relaxation process is related to the ion transport in thin films. The results of the investigation of the temperature dependencies of thin films ionic conductivity (σ) showed that the dependence σ(T) is caused by the temperature dependence of oxygen vacancy mobility, while the number of charge carriers remains constant with temperature.

TexPat – a program for quantitative analysis of oblique texture electron diffraction patterns

2004 ◽  
Vol 219 (1) ◽  
Author(s):  
Peter Oleynikov ◽  
Sven Hovmöller ◽  
Xiaodong Zou ◽  
Anatoliy P. Zhukhlistov ◽  
Maxim S. Nickolsky ◽  
...  
Keyword(s):  
Automated Detection ◽  
Unit Cell ◽  
Published Data ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Symmetry Properties ◽  
Speed Up ◽  
Diffraction Patterns ◽  
Integrated Intensities

AbstractWe have developed a program – TexPat for quantification of texture patterns in order to facilitate, speed up and improve the accuracy of this analytical method. The program introduces new approaches for automated detection of centre and symmetry axes and simplifies the process of indexing and calculating the unit cell parameters. The main algorithm of the program uses the symmetry properties of the texture pattern images. The successive steps help to process the reflections of the pattern using the peak shape extracted from well-separated peaks. The program generates a list of unit cell parameters, all processed reflections with Miller indices and their integrated intensities. The quality of the results obtained by TexPat is compatible with published data.

Biology and Physiology of Feeding in Adult Lampreys

1980 ◽  
Vol 37 (11) ◽  
pp. 1751-1761 ◽  
Author(s):  
G. J. Farmer
Keyword(s):  
Growth Rates ◽  
High Efficiency ◽  
Cold Water ◽  
Feeding Habits ◽  
Maximum Growth ◽  
Sea Lamprey ◽  
Food Material ◽  
Sea Lampreys ◽  
Host Mortality ◽  
Host Fishes

Although landlocked sea lampreys (Petromyzon marinus) attack all but a few of the smallest teleosts in the Great Lakes, the large cold-water species have received the most predation. Information on the feeding habits of anadromous lampreys is limited, but they probably are not specific in their choice of hosts. Species differences exist in the relative proportions of blood and muscle tissue which are consumed. The landlocked sea lamprey primarily feeds on the blood of host fishes at rates of 3–30% of its wet body weight∙d−1 (10 °C). The estimated gross conversion efficiency for this species feeding ad libitum at 10 °C is 39%. This relatively high efficiency is partly attributable to the nature of their blood diet which results in small fecal energy losses of about 3.4% of intake energy. Maximum growth rates occur at 20 °C for sea lampreys of 10–30 g initial weight and at 15 °C for lampreys of 30–90 g. At all experimental temperatures (5–20 °C), growth rates decline with increases in lamprey weight. Increases in sea lamprey weight and in water temperature up to 20 °C cause the rate of host mortality to rise suggesting that, under natural conditions, mortality is seasonal. Landlocked sea lampreys show a preference for specific areas on their hosts, select larger hosts more frequently, and are not attracted to hosts that have lampreys feeding on them. Such strategies serve to maximize food intake and prolong host survival while ensuring food material of constant energy content.Key words: adult lampreys, feeding, hosts, growth rate, temperature, host mortality, behavior

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