scholarly journals Silicon in Fe-Si Alloys: Correction of X-Ray Intensities for Preferred Orientation

1997 ◽  
Vol 29 (1-2) ◽  
pp. 77-87
Author(s):  
M. O. Figueiredo ◽  
F. Margarido
Keyword(s):  
Preferred Orientation ◽  
Correction Procedure ◽  
X Ray Diffraction ◽  
Silicon Phase ◽  
X Ray ◽  
Orientation Effects ◽  
Profile Fitting ◽  
Previous Algorithm ◽  
Texture Effect ◽  
Diffraction Patterns

A texture effect in the silicon phase of industrial Fe-Si alloys was noticed in the X-ray diffraction patterns through the reinforcement of the 111 reflection. A similar effect was also apparent in a commercial silicon standard pellet used as reference material and supposed to be texture-free.A quick correction procedure to account for preferred orientation effects was developed, based on a previous algorithm currently applied for the automatic profile fitting of powder diffractometer data. “Modified Wilson plots” are established for visualizing the efficiency of texture correction according to the proposed method.

Sinterbility of (Bi4-xLax)Ti3O12 Ceramics

2008 ◽  
Vol 55-57 ◽  
pp. 841-844 ◽  
Author(s):  
Pasinee Siriprapa ◽  
Anucha Watcharapasorn ◽  
Sukanda Jiansirisomboon
Keyword(s):  
Grain Orientation ◽  
Sintering Temperature ◽  
Orthorhombic Phase ◽  
Preferred Orientation ◽  
Doping Content ◽  
X Ray Diffraction ◽  
Microstructural Investigation ◽  
X Ray ◽  
Lanthanum Titanate ◽  
Diffraction Patterns

This research studied the effects of sintering temperature and La3+ doping content on phase, microstructure and densification of bismuth lanthanum titanate (Bi4-xLaxTi3O12; BLT) ceramics when x = 0, 0.25, 0.5, 0.75 and 1.0, respectively. The BLT powders were prepared using a mixed-oxide method. The mixtures were calcined at 750°C for 4 h before being pressed and sintered at 1000-1150°C for 4 h. The result of phase analysis by X–ray diffraction (XRD) indicated the existence of orthorhombic phase for all sintering temperatures. The XRD peak intensities of the ceramics showed preferred orientation of a particular set of {00l}-type planes. The ceramics mainly composed of plate-like grains. Increasing the sintering temperature increased grain size and increased preferred grain orientation. The present of La3+ in BLT ceramics reduced preferred orientation especially at higher sintering temperature. Results of microstructural investigation agreed well with X-ray diffraction patterns.

Comments on determining X-ray diffraction-based volume fractions of retained austenite in steels

2001 ◽  
Vol 16 (4) ◽  
pp. 198-204 ◽  
Author(s):  
C. K. Lowe-Ma ◽  
W. T. Donlon ◽  
W. E. Dowling
Keyword(s):  
Retained Austenite ◽  
Volume Fraction ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
X Ray ◽  
Profile Fitting ◽  
Diffraction Peaks ◽  
Diffraction Patterns ◽  
Heat Treatment Regimes ◽  
Integrated Intensities

Retained austenite is an important characteristic of properly heat-treated steel components, particularly gears and shafts, that will be subjected to long-term use and wear. Normally, either X-ray diffraction or optical microscopy techniques are used to determine the volume percent of retained austenite present in steel components subjected to specific heat-treatment regimes. As described in the literature, a number of phenomenological, experimental, and calculation factors can influence the volume fraction of retained austenite determined from X-ray diffraction measurements. However, recent disagreement between metallurgical properties, microscopy, and service laboratory values for retained austenite led to a re-evaluation of possible reasons for the apparent discrepancies. Broad, distorted X-ray peaks from un-tempered martensite were found to yield unreliable integrated intensities whereas diffraction peaks from tempered samples were more amenable to profile fitting with standard shape functions, yielding reliable integrated intensities. Retained austenite values calculated from reliable integrated intensities were found to be consistent with values obtained by Rietveld refinement of the diffraction patterns. The experimental conditions used by service laboratories combined with a poor choice of diffraction peaks were found to be sources of retained austenite values containing significant bias.

X-ray diffraction patterns of LuNi2B2C and YNi2B2C

1996 ◽  
Vol 11 (2) ◽  
pp. 88-90 ◽  
Author(s):  
W. Wong-Ng ◽  
R. Cava ◽  
J. J. Krajewski ◽  
W. F. Peck
Keyword(s):  
Preferred Orientation ◽  
Specimen Preparation ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Arc Melting ◽  
Melting Technique ◽  
Diffraction Patterns

Reference X-ray diffraction patterns for the quarternary intermetallic superconductor phases of compositions LuNi2B2C and YNi2B2C are reported. Both materials were synthesized by the arc-melting technique. The patterns of these metallic phases exhibit preferred orientation in an ordinarily pressed sample, which was minimized through special specimen preparation. The observed intensities and the calculated values for both phases agree reasonably well with each other. Both compounds were refined in the space group I4/mmm, with a=3.4647(1) Å and c=10.6330(4) Å for LuNi2B2C and a=3.5271(1) Å, c=10.5361(7) Å for YNi2B2C.

Micro X-ray diffraction on capillary powder samples: a novel and effective technique for overcoming preferred orientation

2001 ◽  
Vol 34 (5) ◽  
pp. 663-665 ◽  
Author(s):  
P. Bergese ◽  
E. Bontempi ◽  
I. Colombo ◽  
L. E. Depero
Keyword(s):  
Structural Parameters ◽  
Preferred Orientation ◽  
X Ray Diffraction ◽  
Rapid Preparation ◽  
X Ray ◽  
Polymeric Carriers ◽  
Powder Samples ◽  
Promising Solution ◽  
Diffraction Patterns ◽  
Analytical Approaches

In past years, both experimental and analytical approaches have been developed for eliminating preferred orientation effects on powder X-ray diffraction patterns. The state of the art does not allow one to face the problem without difficult sample treatments, mechanical randomization, pole-figure study or pattern fitting based on the Rietveld approach. These methods are time consuming or need the knowledge of all the structural parameters, and, moreover, must be managed by specialized operators. Besides, none of the above techniques can be applied to powder samples of drugs loaded into polymeric carriers, the diffraction patterns of which present a structured amorphous halo from which the crystalline drug peaks rise up. In this paper, it is shown that micro X-ray diffraction on capillary powder samples, combined with a two-dimensional detector, is a promising solution to preferred orientation problems, since it provides easy and rapid preparation of randomly oriented powder samples, fast measurements (acquisition times of a few minutes) and correct powder diffraction patterns.

Parallel-beam X-ray diffractometry using X-ray guide tubes

2000 ◽  
Vol 33 (2) ◽  
pp. 389-391 ◽  
Author(s):  
Toyoko Yamanoi ◽  
Hiromoto Nakazawa
Keyword(s):  
Large Diameter ◽  
Preferred Orientation ◽  
X Rays ◽  
X Ray Diffraction ◽  
Parallel Beam ◽  
X Ray ◽  
Orientation Effects ◽  
Powder Samples ◽  
Xrd Patterns ◽  
Integrated Intensities

A parallel-beam X-ray diffraction geometry using X-ray guide tubes is proposed to eliminate preferred-orientation effects in powder X-ray diffraction (XRD) patterns and for new applications of XRD. A bundle of X-ray guide tubes (polycapillaries) is used to provide an intense quasi-parallel (approximately 0.2° divergence) and large-diameter (approximately 20 mm) beam of X-rays needed for parallel-beam diffractometry. Mica and silicon particles were agitated inside a cylindrical chamber by a steady flow of N2gas so that they were randomly oriented. The quasi-parallel incident X-ray beam passed through the cloud of floating particles. The diffracted X-rays were detected using a standard 2θ diffractometer. The integrated intensities observed agree well with those calculated from the known model of the crystal structure. This result demonstrates that this type of diffractometry is capable of avoiding preferred-orientation effects and of collecting XRD data for moving powder samples.

scholarly journals Quantitative analysis of turbostratically disordered nontronite with a supercell model calibrated by the PONKCS method

2012 ◽  
Vol 45 (6) ◽  
pp. 1295-1302 ◽  
Author(s):  
Xiaodong Wang ◽  
Robert D. Hart ◽  
Jian Li ◽  
Robbie G. McDonald ◽  
Arie van Riessen
Keyword(s):  
Structural Model ◽  
Preferred Orientation ◽  
Quantitative Phase Analysis ◽  
X Ray Diffraction ◽  
Orientation Effects ◽  
Physically Based ◽  
Quantitative Results ◽  
Diffraction Patterns ◽  
Xrd Patterns ◽  
Supercell Model

Two calibration-based quantitative X-ray diffraction (XRD) models for turbostratically disordered Bulong nontronite, the PONKCS (partial or no known crystal structure) approach and the supercell structural model, were compared in terms of the accuracy and refinement error from Rietveld quantitative phase analysis. The PONKCS approach achieved improved nontronite quantitative results with synchrotron diffraction patterns compared with those achieved with laboratory XRD data as a result of better data quality and the use of Debye–Scherrer geometry with significantly reduced preferred orientation effects. The introduction of a peak shape modifier (spherical harmonics) to correct the quantification result is mainly useful for laboratory XRD patterns containing nontronite collected from Bragg–Brentano geometry with appreciable preferred orientation effects. A novel calibration approach for the nontronite supercell model was developed, based on the Rietveld quantitative formula in theTOPASsymbolic computation system. The calibrated supercell model achieved better accuracy (deviation within 1 wt%) and lower refinement error than the PONKCS approach because the physically based description of turbostratic disorder requires fewer refinable parameters than the PONKCS approach. The drawbacks and limitations of the supercell approach are also discussed.

A Study of Cuban Todorokite

1961 ◽  
Vol 5 ◽  
pp. 117-126
Author(s):  
G. M. Faulring
Keyword(s):  
Preferred Orientation ◽  
Optical Data ◽  
X Ray Diffraction ◽  
Random Orientation ◽  
Sodium Potassium ◽  
X Ray ◽  
Cell Dimensions ◽  
Diffraction Patterns ◽  
High Degree ◽  
Manganese Oxide Mineral

AbstractTodorokite is a hydrated manganese oxide mineral containing small amounts of sodium, potassium, calcium, barium, magnesium, iron, and aluminum. From the reports of other investigators and observations in our laboratories, todorokite appears to be a more widely occurring mineral than generally recognized.It was found by X-ray diffraction that a sample of todorokite from Charco Redondo, Cuba, had a high degree of preferred orientation and that milling for a prolonged period of time was necessary to obtain random orientation in a mounted specimen. The position of the preferred orientation direction with respect to the X-ray beam is the principal factor determining the relative intensities on an X-ray diffraction pattern. Based on fiber data, the unit cell of todorokite is considered to be pseudo-orthorhombic or triclinic with α, β, and γ angles varying slightly from 90° and cell dimensions of a0 = 9.65A, b0 = 10.29A, and c0 = 2.84A, This deviation from orthogonality may account for the diffuse and distinct reflections typical of X-ray diffraction patterns of todorokite. Optical data and a hypothesized paragenesis of Cuban todorokite are also included.

Minimization of Preferred Orientation in Powders by Spray Drying

1978 ◽  
Vol 22 ◽  
pp. 77-87 ◽  
Author(s):  
Steven T. Smith ◽  
Robert L. Snyder ◽  
W. E. Brownell
Keyword(s):  
Diffraction Analysis ◽  
Spray Drying ◽  
Preferred Orientation ◽  
X Ray Diffraction ◽  
Simple Method ◽  
X Ray ◽  
Orientation Effects ◽  
Spray Dried

The spray drying of powders is a method of forming spherical or torroidal shaped agglomerates. A relatively simple method is given for preparing spray dried samples of the quantities used in x-ray diffraction analysis. This technique is shown to minimize preferred orientation effects on diffraction intensities from materials of widely differing symmetry and crystallite habit.

Determination of nanoparticle structure type, size and strain distribution from X-ray data for monatomic f.c.c.-derived non-crystallographic nanoclusters

2003 ◽  
Vol 36 (5) ◽  
pp. 1148-1158 ◽  
Author(s):  
Antonio Cervellino ◽  
Cinzia Giannini ◽  
Antonietta Guagliardi
Keyword(s):  
Structure Type ◽  
X Ray Diffraction ◽  
Debye Function ◽  
X Ray ◽  
Profile Fitting ◽  
Type Size ◽  
Nanoparticle Structure ◽  
Diffraction Patterns ◽  
Specific Material ◽  
Log Normal

Whole-profile-fitting least-squares techniques are applied to simulated and experimental X-ray diffraction patterns of monatomic face-centred cubic (f.c.c.)-derived non-crystallographic nanoclusters to extract structure and size information. Three main structure types have been considered (cuboctahedral, icosahedral and decahedral). Nanocluster structure models have been generated within an original mathematical approach so as to be independent of a specific material. For each structure type, a log-normal size distribution is assumed and a phenomenological function is introduced to model possible additional size-related strain effects. The Debye function method (modified to increase computational efficiency) has been used to obtain the diffracted intensities of the nanocluster. Tests revealed the effectiveness of the method to recognize the structure types correctly and to estimate with good accuracy structure concentrations and size distributions. Application to a thiol-passivated gold nanoparticle sample is presented.

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