Investigation of the products of reaction of (Sc, Y)2O3 and (Sc, Dy)2O3 mixed crystals with carbon in proportions corresponding to the formation of M15C19 phase

1984 ◽  
Vol 49 (4) ◽  
pp. 944-953 ◽  
Author(s):  
Bohumil Hájek ◽  
Pavel Karen ◽  
Vlastimil Brožek
Keyword(s):  
Quantitative Phase Analysis ◽  
Stoichiometric Ratio ◽  
X Ray Diffraction ◽  
Complex Phase ◽  
Gaseous Products ◽  
Hydrolysis Method ◽  
Phase Systems ◽  
Diffraction Patterns ◽  
Products Of Reaction

Scandium, yttrium, and dysprosium formates were subjected to reaction with carbon in a stoichiometric ratio of M2O3 : C = 1 : (83/15) at 1 650 °C and 1 Pa for 40 h to give products containing typical phases of Sc2OC and Sc15C19, Y2OC and YC2, and Dy2OC and DyC2, respectively (Y2OC and Dy2OC Fm3m, a = 494.7 ± 0.2 and 495.0 ± 0.2 pm, respectively). The mixed scandium-yttrium or scandium-dysprosium carbides prepared under the same conditions did not exhibit diffraction patterns of the M15C19 carbides, and were constituted by mixed dicarbide and mixed oxide-carbide crystals. Yttrium and, to a greater extent, dysprosium are preferentially located in the dicarbide structure, whereas scandium occupies more the oxide-carbide structure. The mixed scandium-dysprosium carbide (Sc0,94Dy0,06)15C19 (P421c, a = 753 ± 1 pm, c = 1 506 ± 3 pm) starts to form at temperatures above the melting temperature of the mixture (1750-1800 °C). The composition of the gaseous products of hydrolysis is consistent with the phase composition of the samples. The method of quantitative phase analysis based on the GLC analysis of the gases evolved on the hydrolysis is employed for the analysis of complex phase systems. In addition to chemical and X-ray diffraction analysis, the hydrolysis method is also applied to the determination of additional products.

Investigation of the products of carbothermal reduction of yttrium oxide by the hydrolysis method

1984 ◽  
Vol 49 (4) ◽  
pp. 936-943 ◽  
Author(s):  
Bohumil Hájek ◽  
Pavel Karen ◽  
Vlastimil Brožek
Keyword(s):  
Yttrium Oxide ◽  
Carbothermal Reduction ◽  
Stoichiometric Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hydrolysis Method ◽  
Sample Decomposition ◽  
Products Of Reaction ◽  
Hydrolysis Of ◽  
Lower Carbon

For the investigation of the products of reaction of yttrium oxide with carbon mixed in various proportions, the chemical and X-ray diffraction methods of analysis were combined with the gas chromatographic analysis of the mixture of hydrocarbons and hydrogen formed on the sample decomposition with water. The carboreduction of Y2O3 was examined at relatively low temperatures, convenient for obtaining the reaction intermediates in higher yields. At 1 600 °C and pressures of 10-3 Pa the reduction of a mixture of Y2O3 with carbon in a stoichiometric ratio of 1 : 7 yields YC2 in equilibrium with 20% of Y2OC phase. At lower carbon contents (down to the Y2O3 : C ratio of 1 : 2) tha fraction of the Y2OC phase increases up to approximately 30%. In addition to Y2O3, the reaction mixture contains also Y2C, Y2OC and a phase giving propyne on hydrolysis. The presence of traces of C3 hydrocarbons and small amounts of methane in the product of hydrolysis of the carbide sample prepared by the carbothermal reduction of the oxide can be explained in terms of the occurrence of the Y15C19 phase, probably substituted in part by oxygen, and of the Y2OC phase. The results are compared with those obtained previously for the Sc2O3 + C system.

scholarly journals Born out of Fire and Ice: Polymorph Studies of the Antiviral Famciclovir

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 129
Author(s):  
Liana Vella-Zarb ◽  
Ulrich Baisch
Keyword(s):  
Variable Temperature ◽  
Chemical Properties ◽  
Crystal Form ◽  
X Ray Diffraction ◽  
Crystal Forms ◽  
X Ray ◽  
Physical Chemical ◽  
Diffraction Patterns ◽  
Crystalline Forms

There is much interest and focus on solid forms of famciclovir. However, in spite of the abundance of reported differences in oral bioavailability, compressibility, and other physical–chemical properties of the various crystal forms of this drug, very little precise structural analysis is available in the literature to date. The form used in the commercial formulation is the anhydrous form I. Patents and patent applications report three different anhydrous crystalline forms on the basis of unindexed powder diffraction patterns. Single-crystal and variable-temperature X-ray diffraction experiments using the commercially available anhydrous form of famciclovir were carried out and led not only to the crystal structure determination of the anhydrous form I, but also to discovery of a new crystal form of anhydrous famciclovir from powder data.

A Method for Quantitative Phase Analysis of Silicon Nitride by X-Ray Diffraction

1990 ◽  
Vol 5 (3) ◽  
pp. 121-124 ◽  
Author(s):  
David J. Devlin ◽  
Kamal E. Amin
Keyword(s):  
Silicon Nitride ◽  
Iterative Method ◽  
Calibration Curve ◽  
Quantitative Measurement ◽  
Quantitative Phase Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Pure Phases ◽  
Yttrium Disilicate

AbstractThe relative intensities ratios for the determination of the relative amounts of alpha and beta phases in silicon nitride and the relative amounts of delta yttrium disilicate (Y2Si2O7) and nitrogen apatite [Y5(SiO4)3N] are reported. These constants were determined using an iterative method applicable when the pure phases are not easily prepared. In addition, a calibration curve was obtained for the quantitative measurement of free silicon in silicon nitride over the range 0 to 0.3% by weight of Si.

scholarly journals Synthesis of the Modifications of Ca2SiO4 and the Determination of their Powder X-ray Diffraction Patterns

1963 ◽  
Vol 71 (806) ◽  
pp. 63-68 ◽  
Author(s):  
Goro YAMAGUCHI ◽  
Yoshio ONO ◽  
Shigeo KAWAMURA ◽  
Yoshiaki SODA
Keyword(s):  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Patterns

Synthesis and Crystal Structure Determination of Cyclosporin H

2000 ◽  
Vol 65 (8) ◽  
pp. 1317-1328 ◽  
Author(s):  
Alexandr Jegorov ◽  
Ladislav Cvak ◽  
Aleš Husek ◽  
Petr Šimek ◽  
Anna Heydová ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Amino Acids ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Synthesis And Crystal Structure ◽  
X Ray ◽  
Acid Catalyzed ◽  
Products Of Reaction ◽  
Cyclosporin H

Acid-catalyzed degradation of cyclosporin A was studied in various solvents and products of reaction were monitored by HPLC. Identification of amino acids and their chirality were determined after hydrolysis and derivatization by GC-MS. Cyclosporin H was isolated as the principal product and its structure was determined by X-ray diffraction: Cyclosporin H- diethyl ether-water (1 : 0.5 : 1) crystallizes in the monoclinic space group I2 with a = 12.338(2) Å, b = 18.963(2) Å, c = 34.074(3) Å, β = 96.47(2)°, Z = 4, and V = 7 921.4(17) Å3.

Effects of Internal Standards and Peak Profile Functions on Quantitative XRD Phase Analysis of Cement and its Hydrates

2011 ◽  
Vol 492 ◽  
pp. 424-428
Author(s):  
Yong Qi Wei ◽  
Wu Yao ◽  
Wei Wang
Keyword(s):  
Phase Analysis ◽  
Internal Standard ◽  
Direct Determination ◽  
Quantitative Phase Analysis ◽  
X Ray Diffraction ◽  
Profile Function ◽  
Internal Standards ◽  
Refinement Method ◽  
Xrd Phase Analysis

Quantitative X-Ray diffraction (QXRD) combined with the Rietveld refinement method allows direct determination of crystalline phase content of cement and its hydrates. However, relatively precise results need the correction of proper internal standards and the use of matched peak profile functions with masterly refinement strategies. The aim of this paper is to research and discuss effects of these factors on the quantitative phase analysis results. For this purpose, different internal standards and peak profile functions with corresponding refinement strategies were attempted in experiments and refinements. The results indicate that Al2O3as internal standard is more suitable for cement and its hydrates than ZnO, and the better peak profile function is CW function 2 rather than function 3 in GSAS.

scholarly journals An investigation of goethite-seeded Al(OH)3precipitation usingin situX-ray diffraction and Rietveld-based quantitative phase analysis

2010 ◽  
Vol 43 (3) ◽  
pp. 466-472 ◽  
Author(s):  
Nathan A. S. Webster ◽  
Ian C. Madsen ◽  
Melissa J. Loan ◽  
Robert B. Knott ◽  
Fatima Naim ◽  
...  
Keyword(s):  
Phase Analysis ◽  
Process Equipment ◽  
Quantitative Phase Analysis ◽  
X Ray Diffraction ◽  
Subsequent Formation ◽  
Bayer Liquor ◽  
Quantitative Phase ◽  
Kinetic Information ◽  
Absolute Phase

Anin situX-ray diffraction investigation of goethite-seeded Al(OH)3precipitation from synthetic Bayer liquor at 343 K has been performed. The presence of iron oxides and oxyhydroxides in the Bayer process has implications for alumina reversion, which causes significant process losses through unwanted gibbsite precipitation, and is also relevant for the nucleation and growth of scale on mild steel process equipment. The gibbsite, bayerite and nordstrandite polymorphs of Al(OH)3precipitated from the liquor; gibbsite appeared to precipitate first, with subsequent formation of bayerite and nordstrandite. A Rietveld-based approach to quantitative phase analysis was implemented for the determination of absolute phase abundances as a function of time, from which kinetic information for the formation of the Al(OH)3phases was determined.

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