Structures of Orthorhombic and Cubic Dicadmium Stannate by Rietveld Refinement

1990 ◽  
Vol 5 (1) ◽  
pp. 36-40 ◽  
Author(s):  
M.E. Bowden ◽  
C. M. Cardile
Keyword(s):  
Detection Limit ◽  
Spinel Structure ◽  
Structural Changes ◽  
Colour Change ◽  
Rietveld Analysis ◽  
Hydrogen Gas ◽  
X Ray ◽  
Uniform Contraction ◽  
Reitveld Analysis ◽  
Diffraction Patterns

AbstractThe structures of orthorhombic (a=5.5686(2)Å, b=9.8946 (2)Å, c=3.19369(12Å) and cubic (a=9.177(3)Å) Cd2SnO4were refined by Rietveld analysis of X-ray powder diffraction patterns. Both of these polymorphs were chemically treated with hydrogen gas mixtures at 400°C, resulting in a colour change from yellow to green. Small structural changes were observed for the orthorhombic material, which underwent a uniform contraction (≈0.02%) of cell size and movement of some oxygen atoms towards the tin atoms. Evidence for loss of structural oxygen was sought, but could not be found above the detection limit of 0.3%. Cubic Cd2SnO4possesses the spinel structure with a large (at least 65%) degree of inversion. Samples prepared with a smaller cell have so far proved unsuitable for Reitveld analysis.

scholarly journals PECHINI SYNTHESIS AND CHARACTERIZATION OF Eu3+ DOPED ZnCo2O4 SPINELS

2005 ◽  
Vol 03 (2) ◽  
pp. 24-29
Author(s):  
P.M. PIMENTEL ◽  
A.M.G. PEDROSA ◽  
H.K.S. SOUZA ◽  
C.N.S. JÚNIOR ◽  
R.C.A. PINTO ◽  
...  
Keyword(s):  
Spinel Structure ◽  
Pechini Method ◽  
Synthesis Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Spinel Oxides ◽  
Diffraction Patterns ◽  
Pechini Synthesis ◽  
Spinel Structures

Spinel oxides with the composition ZnCo2O4 and ZnCo2O4:Eu3+ have been synthesized by the Pechini method and characterized by X-ray diffraction, infrared spectroscopy, thermal analysis and scanning electron microscopy. IR spectroscopy revealed the presence of n1 and n2 bands, typical of spinel structures. The formation of monophase cubic spinel structure was confirmed by X-ray diffraction patterns. Extra lines corresponding to other phase has been observed in the powders calcined at 900 ºC. The results showed the extremely lower synthesis temperature than those presents in conventional methods.

Influence of Aging Time on the Structural Changes of Cassava Thermoplastic Starch

2012 ◽  
Vol 1372 ◽  
Author(s):  
José H. Mina ◽  
Alex Valadez ◽  
Pedro J. Herrera-Franco ◽  
Tanit Toledano
Keyword(s):  
Yield Stress ◽  
Amorphous Phase ◽  
Structural Changes ◽  
Thermoplastic Starch ◽  
X Ray Diffraction ◽  
X Ray ◽  
Second Stage ◽  
Diffraction Patterns ◽  
Type V ◽  
Stress Drops

ABSTRACTIn this work the change in the structural properties of cassava (manihot sculenta Crantz) thermoplastic starch (TPS) under controlled environment (humidity and temperature) was studied. Fourier Transform Infrared spectroscopy (FTIR) and X-ray diffraction (XRD) results showed an evident increasing in the amorphous phase of the TPS regarding the native starch. There was a relative decrease of the band at 1047 cm-1 associated to crystalline structure of starch compared to the amorphous peak at 1022 cm-1. The X-ray diffraction patterns confirmed the increment of the amorphous phase in the TPS samples. Likewise the X-ray diffraction patterns shows evidence of residual type C crystallinity and the formation of a new crystalline phase type VH due to the orientation induced in plasticization process. In first stage of conditioning the tensile yield stress drops from 7.5 drops to 0.5 MPa and the break strain increases 1000%. At the same time it seems that the crystallinity of the samples increases as was evidenced by the gradually increasing of the FTIR band at 1047 cm-1. In a second stage, the yield stress increases, the break strain drops and the crystallinity continue growing steadily. These findings suggest that coexist two phenomena simultaneously in the samples. A phenomenon of re-crystallization (retrogradation) that tends to make the material more stiff and a process of plasticization that tends to softening it. It seems that the latter mechanism predominates in the first stage, at short times, and the former in the second stage, at older times.

Surface Characterization of Carbon-Bearing Magnetite (CBM) and Carbon-Bearing Ni(II)-Ferrite (CBNF)

1994 ◽  
Vol 344 ◽  
Author(s):  
T. Sano ◽  
K. Akanuma ◽  
M. Tsuji ◽  
Y. Tamaura
Keyword(s):  
Photoelectron Spectroscopy ◽  
Spinel Structure ◽  
Surface Characterization ◽  
Carbon Deposition ◽  
X Ray Diffraction ◽  
Xps Spectra ◽  
X Ray ◽  
Oxygen Ions ◽  
Diffraction Patterns

AbstractOxygen-deficient magnetite (ODM; Fe3O4-δ, δ>0) synthesized by reduction of magnetite with H2 at 300°C decomposed CO2 to carbon with an efficiency of nearly 100% at 300°C. In this reaction, two oxygen ions of the CO2 were incorporated into the spinel structure of ODM and carbon was deposited on the surface of ODM with zero valence to form visible particles. The particles of carbon separated from ODM were studied by Raman, energy-dispersive X-ray and wave-dispersive X-ray spectroscopies. The carbon which had been deposited on the ODM was found to be a mixture of graphite and amorphous carbon in at least two levels of crystallization. X-ray photoelectron spectroscopy and X-ray diffraction patterns of the carbon-bearing magnetite (CBM) showed no indication of carbide (Fe3C) or metallic iron (α-Fe) phase formation. In the C 1s XPS spectra of the CBM, no peaks were observed which could be assigned to CO2 or CO. X-ray diffractometry, chemical analysis and TG-MS measurement showed that the carbon-bearing Ni(II)-ferrite (CBNF) (Ni(II)/Fetotal = 0.15) synthesized by the carbon deposition reaction from CO2 with the H2-reduced Ni(II)-ferrite was represented by (Ni0.28Fe2.72O4.00)1-δ (Ni2+06.9Fe2+2.31O3.00)δCτ (δ= 0.27, τ= 0.17). The carbon of the CBNF gave the CIOlayer-like oxide containing some Ni2+ ions.

Development of an in situ synchrotron X-ray total scattering setup under pressurized hydrogen gas

2018 ◽  
Vol 51 (3) ◽  
pp. 796-801 ◽  
Author(s):  
Kouji Sakaki ◽  
Hyunjeong Kim ◽  
Akihiko Machida ◽  
Tetsu Watanuki ◽  
Yoshinori Katayama ◽  
...  
Keyword(s):  
Pair Distribution Function ◽  
Hydrogen Gas ◽  
Ex Situ ◽  
Sample Holder ◽  
Hydrogen Storage Materials ◽  
X Ray Diffraction ◽  
Total Scattering ◽  
X Ray ◽  
Diffraction Patterns

This article describes the development of an in situ gas-loading sample holder for synchrotron X-ray total scattering experiments, particularly for hydrogen storage materials, designed to collect diffraction and pair distribution function (PDF) data under pressurized hydrogen gas. A polyimide capillary with a diameter and thickness of 1.4 and 0.06 mm, respectively, connected with commercially available Swagelok fittings was used as an in situ sample holder. Leakage tests confirmed that this sample holder allows 3 MPa of hydrogen gas pressure and 393 K to be achieved without leakage. Using the developed in situ sample holder, significant background and Bragg peaks from the sample holder were not observed in the X-ray diffraction patterns and their signal-to-noise ratios were sufficiently good. The PDF patterns showed sharp peaks in the r range up to 100 Å. The results of Rietveld and PDF refinements of Ni are consistent with those obtained using a polyimide capillary (1.0 mm diameter and 0.04 mm thickness) that has been used for ex situ experiments. In addition, in situ synchrotron X-ray total scattering experiments under pressurized hydrogen gas up to 1 MPa were successfully demonstrated for LaNi4.6Cu.

Update in a Rietveld analysis program for x-ray powder spectro-diffractometry

2003 ◽  
Vol 18 (1) ◽  
pp. 32-35 ◽  
Author(s):  
Yanan Xiao ◽  
Fujio Izumi ◽  
Timothy Graber ◽  
P. James Viccaro ◽  
Dale E. Wittmer
Keyword(s):  
Computer Program ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Analysis ◽  
Anomalous Scattering ◽  
Analysis Program ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Synchrotron Light ◽  
Diffraction Patterns

A computer program for refining anomalous scattering factors using x-ray powder diffraction data was revised on the basis of the latest version of a versatile pattern-fitting system, RIETAN-2000. The effectiveness of the resulting program was confirmed by applying it to simulated and measured powder-diffraction patterns of Mn3O4 taken at a synchrotron light source.

X-ray powder diffraction analysis of the heteropoly-molybdate (MoO2)0.5PMo14O42

2003 ◽  
Vol 18 (3) ◽  
pp. 236-239 ◽  
Author(s):  
L. Marosi ◽  
J. Cifré ◽  
C. Otero Areán
Keyword(s):  
Catalytic Activity ◽  
Diffraction Analysis ◽  
Computer Modeling ◽  
Powder Diffraction ◽  
Rietveld Analysis ◽  
Nitrogen Atmosphere ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Patterns

The new heteropoly blue compound (MoO2)0.5PMo14O42, which is relevant in the context of catalytic activity of heteropoly-molybdates, was prepared by controlled thermolysis of (NH4)3PMo12O40 at 730 K in a nitrogen atmosphere. Powder X-ray diffraction analysis showed that this compound has a cubic unit cell, space group Pn3m (No. 224), with ao=11.795(2) Å, Z=2 and DXR=4.2466 g cm−3. Computer modeling and Rietveld analysis of powder diffraction patterns led to a proposed structure of the corresponding Keggin-cage unit PMo14O42.

scholarly journals Iron-containing phases in metallurgical and coke dusts as well as in bog iron ore

Nukleonika ◽  
2017 ◽  
Vol 62 (2) ◽  
pp. 187-195 ◽  
Author(s):  
Tadeusz Szumiata ◽  
Marzena Rachwał ◽  
Tadeusz Magiera ◽  
Katarzyna Brzózka ◽  
Małgorzata Gzik-Szumiata ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Spinel Structure ◽  
Iron Ore ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mineral Phases ◽  
Coke Plants ◽  
Wide Range ◽  
Specific Magnetic Susceptibility ◽  
Diffraction Patterns

Abstract Several samples of dusts from steel and coke plants (collected mostly with electro filters) were subjected to the investigation of content of mineral phases in their particles. Additionally, sample of bog iron ore and metallurgical slurry was studied. Next, the magnetic susceptibility of all the samples was determined, and investigations of iron-containing phases were performed using transmission Mössbauer spectrometry. The values of mass-specific magnetic susceptibility χ varied in a wide range: from 59 to above 7000 × 10−8 m-3·kg−1. The low values are determined for bog iron ore, metallurgical slurry, and coke dusts. The extremely high χ was obtained for metallurgical dusts. The Mössbauer spectra and X-ray diffraction patterns point to the presence of the following phases containing iron: hematite and oxidized magnetite (in coke and metallurgical dusts as well as metallurgical slurry), traces of magnetite fine grains fraction (in metallurgical dusts), amorphous glassy silicates with paramagnetic Fe3+ and Fe2+ ions, traces of pyrrhotite (in coke dusts), α-Fe and nonstoichiometric wüstite (in metallurgical slurry), as well as ferrihydrite nanoparticles (in bog iron ore). For individual samples of metallurgical dusts, the relative contributions of Fe2+/3+ ions in octahedral B sites and Fe2+ ions in tetrahedral A sites in magnetite spinel structure differs considerably.

A Rietveld-analysis program for X-ray powder spectro-diffractometry

1999 ◽  
Vol 14 (2) ◽  
pp. 106-110 ◽  
Author(s):  
Yanan Xiao ◽  
Shinjiro Hayakawa ◽  
Yohichi Gohshi ◽  
Masaharu Oshima ◽  
Fujio Izumi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Absorption Edge ◽  
Rietveld Method ◽  
Rietveld Analysis ◽  
Anomalous Scattering ◽  
Analysis Program ◽  
X Ray ◽  
Diffraction Patterns ◽  
X Ray Absorption

In order to exploit X-ray powder spectro-diffractometry, the program RIETAN-97ß for refining crystal structure and lattice parameters by the Rietveld method was modified extensively. The resulting software can be used to refine anomalous scattering factors, fr and fi, for specified crystallographic sites near the X-ray absorption edge of a particular element. The effectiveness of the modified software was tested by using powder diffraction patterns simulated by the original RIETAN-97ß software and a series of measured powder diffraction patterns of Fe3O4 with incident X-ray energies near the absorption edge of iron.

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