[30] A general purpose, computer-configurable television area detector for X-ray diffraction applications

1985 ◽  
pp. 486-510 ◽  
Author(s):  
Kenneth Kalata
Keyword(s):  
General Purpose ◽  
X Ray Diffraction ◽  
X Ray ◽  
Area Detector ◽  
General Purpose Computer ◽  
Purpose Computer

Separation of Broad Crystalline and Amorphous X-Ray Diffraction Peaks

1980 ◽  
Vol 24 ◽  
pp. 239-243
Author(s):  
O. W. Marks ◽  
D. K. Smith ◽  
M. D. Chris
Keyword(s):  
Computer Program ◽  
General Purpose ◽  
Polymer Mixtures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fitting Procedure ◽  
Computer Input ◽  
Overlapped Peaks ◽  
General Purpose Computer ◽  
Polymer Crystallinity

Separating overlapped peaks is a part of many x-ray diffraction analyses, for example, polymer crystallinity. Natta [1] defined a method for polypropylene in 1957. His method was computerized at the Hercules Research Center in 1960 with an automatic “curve follower” which punched paper tape for the computer. A later method deviated fTom Natta's method by approximating the amorphous curve with a fixed shape and a height chosen to best fit the diffraction data from 2θ = 7.5 through 10. degrees. Neither of these methods worked on “smectic” polymer samples, i.e., composed of very small crystallites. Also, a different computer program was used for each different polymer, so a general purpose computer program was developed using a peak profile method. This method has been used en polymer mixtures and copolymers of ethylene, propylene, and butene; and on cellulose, modified cellulose, and catalysts. The selection of a profile function is discussed in the next section. In later sections, the background, the fitting procedure, and computer input and output are discussed.

Polyhedral characteristics of the cosalite-type crystal structures

2019 ◽  
Vol 57 (5) ◽  
pp. 647-662
Author(s):  
Sabina Kovač ◽  
Predrag Dabić ◽  
Aleksandar Kremenović ◽  
Aleksandar Pačevski ◽  
Ljiiljana Karanović ◽  
...  
Keyword(s):  
Crystal Data ◽  
Chemical Formula ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Area Detector ◽  
Octahedral Sites ◽  
Distorted Octahedral ◽  
Cation Substitutions ◽  
Type Crystal

Abstract The crystal structure of cosalite from the Trepča orefield was refined in the orthorhombic space group Pnma [a = 23.7878 (9), b = 4.0566 (3), c = 19.1026 (8) Å, V = 1843.35 (17) Å3, Z = 2] from single-crystal data (MoKα X-ray diffraction, CCD area detector) to the conventional R1 factor 0.031 for 1516 unique reflections with I > 2σ(I). The chemical formula (Cu0.15Ag0.24)+(Fe0.19Pb7.20)2+(Bi7.06Sb1.06)3+S20, calculated on the basis of 20 S atoms per formula unit, was determined by WDX. The unit cell contains 18 + 2 symmetrically nonequivalent atomic sites: 10 occupied by S; two by pure Pb (Pb3 and Pb4); one by pure Bi (Bi1); two by a combination of Bi and small amounts of Sb (Bi2/Sb2, Bi4/Sb3); two by Pb and Bi, and in one of these also by a small amount of Ag [Me1 = Pb2 >> Bi5 > Ag1, Me3 = Pb1 >> Bi3]; and finally one site, Me2 (Bi6 >> □), is partly occupied by Bi and partly split into an additional two adjacent trigonal planar “interstitial positions”, Cu1 and Cu2, where small amounts of Cu, Ag, and Fe can be situated. All atoms are at 4c special positions at y = 0.25 or 0.75. The structure consists of slightly to moderately distorted MeS6 octahedra sharing edges, bicapped trigonal PbS8 coordination prisms, and fairly distorted Cu1S6 and Cu2S4 polyhedra. The effects of the cation substitutions, bond valence sums, and the polyhedral characteristics are compared with other published cosalite-type structures. Among known cosalite-type structures, the largest volume contraction is shown by sample 4 (Altenberg) and involves the replacement of large cations (Bi3+ and Pb2+) by the smaller Sb3+, as well as Cu+ and Ag+. These replacements are reflected in the variations of individual Me–S bond distances, which are accompanied by variations in average Me–S distances. The degree of polyhedral distortion, Δ, progressively increases for the four Bi-hosting sites of nine cosalite-type structures: Me2 < Bi2 < Bi1 < Bi4. The Bi4 and Me3 are the most and the Me1 and Me2 are the least distorted octahedral sites of the nine cosalite-type structures.

An Efficient Method for Calculating Damped Critical Speeds of Rotor-Bearing Systems

1991 ◽  
Author(s):  
D. Z. Wang ◽  
D. L. Taylor
Keyword(s):  
Element Model ◽  
General Purpose ◽  
Critical Speeds ◽  
Rotor Bearing ◽  
General Purpose Computer ◽  
System Equations ◽  
Newton Raphson ◽  
Reported Data ◽  
Derivatives Of ◽  
Purpose Computer

Abstract This paper describes an analytical approach for calculating the damped critical speeds of multi-degree-of-freedom rotor-bearing systems. It is shown that to calculate the critical speeds is equivalent to finding the roots of a proposed matrix algebraic equation. The technique employes a Newton-Raphson scheme and the derivatives of eigenvalues. The system left eigenvectors are used to simplify the calculations. Based on this approach, a general-purpose computer program was developed with a finite element model of rotor-bearing systems. The program automatically generates system equations and finds the critical speeds. The program is applied to analyze a turbomachine supported by two cylindrical oil-film Journal bearings. The results are compared with reported data and the agreements are very good.

scholarly journals A prototype handheld X-ray diffraction instrument

2018 ◽  
Vol 51 (6) ◽  
pp. 1571-1585 ◽  
Author(s):  
Graeme Hansford
Keyword(s):  
Sample Preparation ◽  
Mineralogical Composition ◽  
General Purpose ◽  
Performance Criteria ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fine Grained ◽  
Back Reflection ◽  
Promising Area ◽  
Sample Position

A conceptual design for a handheld X-ray diffraction (HHXRD) instrument is proposed. Central to the design is the application of energy-dispersive XRD (EDXRD) in a back-reflection geometry. This technique brings unique advantages which enable a handheld instrument format, most notably, insensitivity to sample morphology and to the precise sample position relative to the instrument. For fine-grained samples, including many geological specimens and the majority of common alloys, these characteristics negate sample preparation requirements. A prototype HHXRD device has been developed by minor modification of a handheld X-ray fluorescence instrument, and the performance of the prototype has been tested with samples relevant to mining/quarrying and with an extensive range of metal samples. It is shown, for example, that the mineralogical composition of iron-ore samples can be approximately quantified. In metals analysis, identification and quantification of the major phases have been demonstrated, along with extraction of lattice parameters. Texture analysis is also possible and a simple example for a phosphor bronze sample is presented. Instrument formats other than handheld are possible and online process control in metals production is a promising area. The prototype instrument requires extended measurement times but it is argued that a purpose-designed instrument can achieve data-acquisition times below one minute. HHXRD based on back-reflection EDXRD is limited by the low resolution of diffraction peaks and interference by overlapping fluorescence peaks and, for these reasons, cannot serve as a general-purpose XRD tool. However, the advantages ofin situ, nondestructive and rapid measurement, tolerance of irregular surfaces, and no sample preparation requirement in many cases are potentially transformative. For targeted applications in which the analysis meets commercially relevant performance criteria, HHXRD could become the method of choice through sheer speed and convenience.

Multipurpose diffractometer for in situ X-ray crystallography of functional materials

2021 ◽  
Vol 54 (3) ◽  
Author(s):  
Semën Gorfman ◽  
David Spirito ◽  
Netanela Cohen ◽  
Peter Siffalovic ◽  
Peter Nadazdy ◽  
...  
Keyword(s):  
Electric Field ◽  
Materials Science ◽  
Functional Materials ◽  
X Ray Diffraction ◽  
Reciprocal Space Mapping ◽  
X Ray ◽  
X Ray Crystallography ◽  
Area Detector ◽  
Characterization Of Materials

Laboratory X-ray diffractometers play a crucial role in X-ray crystallography and materials science. Such instruments still vastly outnumber synchrotron facilities and are responsible for most of the X-ray characterization of materials around the world. The efforts to enhance the design and performance of in-house X-ray diffraction instruments benefit a broad research community. Here, the realization of a custom-built multipurpose four-circle diffractometer in the laboratory for X-ray crystallography of functional materials at Tel Aviv University, Israel, is reported. The instrument is equipped with a microfocus Cu-based X-ray source, collimating X-ray optics, four-bounce monochromator, four-circle goniometer, large (PILATUS3 R 1M) pixel area detector, analyser crystal and scintillating counter. It is suitable for a broad range of tasks in X-ray crystallography/structure analysis and materials science. All the relevant X-ray beam parameters (total flux, flux density, beam divergence, monochromaticity) are reported and several applications such as determination of the crystal orientation matrix and high-resolution reciprocal-space mapping are demonstrated. The diffractometer is suitable for measuring X-ray diffraction in situ under an external electric field, as demonstrated by the measurement of electric-field-dependent rocking curves of a quartz single crystal. The diffractometer can be used as an independent research instrument, but also as a training platform and for preparation for synchrotron experiments.

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