The supports’ tendency to generate oxygen vacancies and the Ni/ZrO2 and Ni/Mg(Al)O catalysts performance in the CO2 methanation

2022 ◽  
Author(s):  
Oliver E Everett-Espino ◽  
Priscila Costa Zonetti ◽  
Rafael Celin Mancera ◽  
Luciano T. Costa ◽  
Odivaldo Cambraia Alves ◽  
...  
Keyword(s):  
Rietveld Refinement ◽  
Oxygen Vacancies ◽  
Co2 Methanation ◽  
Refinement Method

The Ni/ZrO2, Ni/Mg(Al)O, and Ni/SiO2 catalysts were employed in the CO2 methanation. The catalysts were characterized by XPS, XRF, XRD (Rietveld refinement method), TPR, EPR, BET, CO2+H2-TPSR, CO+H2-TPSR, CO2-TPD, CO-TPD,...

Structure identification of Nd1-xYbxFeO3 (x = 0.01, 0.05 and 0.10) using Rietveld refinement method

2021 ◽  
Author(s):  
Eko Hadi Sujiono ◽  
Vicran Zharvan ◽  
Sultra Ade Poetra ◽  
Muthmainnah Muchtar ◽  
Abdi Manab Idris ◽  
...  
Keyword(s):  
Rietveld Refinement ◽  
Structure Identification ◽  
Refinement Method

Developing a method for the evaluation of dislocation parameters from the Rietveld refinement procedure

2016 ◽  
Vol 31 (3) ◽  
pp. 198-204 ◽  
Author(s):  
Saba Khalili ◽  
Vishtasb Soleimanian ◽  
Ali Mokhtari
Keyword(s):  
Dislocation Density ◽  
Rietveld Refinement ◽  
Powder Pattern ◽  
Cubic Crystals ◽  
Linear Defects ◽  
Refinement Method ◽  
Refinement Procedure ◽  
Pattern Modeling ◽  
Structure And Microstructure ◽  
Good Agreement

In this investigation, the ability of Rietveld refinement method was used to simultaneously refine the structure and microstructure and evaluate the linear defects of cubic crystals. To do this, the basis of Stephans theory, about the anisotropic strain broadening, was developed and the values of dislocation density as well as the fraction of dislocation types were estimated. The reliability of this procedure was checked by selecting four different nanocrystaslline samples and evaluating the microstructure of these materials. Finally, the results were compared with those extracted from the whole powder pattern modeling method. Good agreement was achieved between the results of two methods.

Crystal structure, properties, and diffraction data of a new compound Dy5Co6Sn18

2008 ◽  
Vol 23 (1) ◽  
pp. 26-30 ◽  
Author(s):  
Yeqing Chen ◽  
Bing He ◽  
Jiejun He ◽  
Wei He ◽  
Lingmin Zeng ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electrical Resistivity ◽  
Magnetic Susceptibility ◽  
Spin Glass ◽  
Rietveld Refinement ◽  
Ternary Compound ◽  
Diffraction Data ◽  
Freezing Temperature ◽  
Refinement Method ◽  
Structure Properties

A new ternary compound Dy5Co6Sn18 was synthesized and studied. The crystal structure of Dy5Co6Sn18 was determined using the Rietveld refinement method. The compound was found to crystallize in tetragonal space group I41/acd, Tb5Rh6Sn18-type structure, with a=13.5598(3) Å, c=7.1470(5) Å, Z=8, and Dcalc=8.789 g/cm3. Measurements of magnetic susceptibility and electrical resistivity on polycrystalline samples were also performed. The Curie–Weiss law was followed, with θp=−15.7 K and μeff=10.61μB. Dy5Co6Sn18 is a spin-glass with a freezing temperature of 6.5 K.

Use of the Rietveld refinement method for the preparation of pure lead hexaferrite

2005 ◽  
Vol 59 (5) ◽  
pp. 591-594 ◽  
Author(s):  
S.A. Palomares-Sánchez ◽  
S. Díaz-Castañón ◽  
S. Ponce-Castañeda ◽  
M. Mirabal-García ◽  
F. Leccabue ◽  
...  
Keyword(s):  
Rietveld Refinement ◽  
Pure Lead ◽  
Refinement Method

An analysis of the Rietveld refinement method

1979 ◽  
Vol 12 (6) ◽  
pp. 554-563 ◽  
Author(s):  
M. Sakata ◽  
M. J. Cooper
Keyword(s):  
Rietveld Refinement ◽  
Refinement Method

Qualitative and quantitative phase analyses of Pingguo bauxite mineral using X-ray powder diffraction and the Rietveld method

2007 ◽  
Vol 22 (4) ◽  
pp. 300-302 ◽  
Author(s):  
Liangqin Nong ◽  
Xiying Yang ◽  
Lingmin Zeng ◽  
Jingping Liu
Keyword(s):  
Rietveld Refinement ◽  
Phase Analysis ◽  
Powder Diffraction ◽  
Rietveld Method ◽  
X Ray ◽  
Quantitative Phase ◽  
Qualitative And Quantitative ◽  
Refinement Method ◽  
Quantitative Analyses ◽  
Qualitative Phase

X-ray powder diffraction technique and the Rietveld refinement method have been used successfully for the qualitative and quantitative analyses of Pingguo bauxite from Guangxi, China. Qualitative phase analysis shows that the Pingguo bauxite contains diaspore (AlOOH), hematite (Fe2O3), goethite (FeOOH), anatase (TiO2), and kaolinite (Al2(Si2O5)(OH)4). Quantitative Rietveld refinement shows that the weight concentrations of diaspore, goethite, hematite, anatase, and kaolinite for the Pingguo bauxite are 71.9(4)%, 7.0(8)%, 11.3(7)%, 6.5(6)%, and 3.3(9)%, respectively.

Portland Cement for the Cementing of Oil Wells Developed with the Aid of the Rietveld Refinement Method

2014 ◽  
Vol 805 ◽  
pp. 350-355
Author(s):  
Danielle Nascimento Silva Oliveira ◽  
Gelmires Araújo Neves ◽  
Ulisses Targino Bezerra ◽  
Alexsandra C. Chaves ◽  
B. Silveira Lira
Keyword(s):  
Linear Programming ◽  
Portland Cement ◽  
Rietveld Refinement ◽  
Polycrystalline Materials ◽  
Oil Well ◽  
X Ray Diffraction ◽  
X Ray ◽  
Refinement Method ◽  
Low Levels

The use of the Rietveld refinement method has been highlightened as essential in the characterization of polycrystalline materials. With the aid of this method, combined with the application of the X-ray diffraction, it was possible to develop a type of cement that can temporarily substitute the Portland cement for Oil well. This cement was developed from the mixture of Portland cements commonly found in the market. The cements were passed through various sieves, then characterized by X-ray diffraction, being identified the main phases (C3A, C4AF, C3S and C2S) and quantified by the Rietveld refinement method. With the values obtained in the quantification of the phases, a new cement was made through the method of linear programming. From the results, it was possible to conclude that the developed cement presented a composition (levels of the main phases) that satisfies the requirements of NBR 9831, mainly in relation to the low levels of C3A.

Rietveld Refinement and DC Conductivity of Na0.5K0.5NbO3 Ceramics

2012 ◽  
Vol 585 ◽  
pp. 210-213 ◽  
Author(s):  
Monica Sindhu ◽  
N. Ahlawat ◽  
Sujata Sanghi ◽  
Ashish Agarwal ◽  
A. Ashima ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Rietveld Refinement ◽  
Base Material ◽  
Polycrystalline Sample ◽  
Solid State Reaction Method ◽  
Dc Conductivity ◽  
Potassium Sodium Niobate ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Refinement Method

Potassium Sodium Niobate, Na0.5K0.5NbO3 is a promising base material for lead free piezoceramics. The polycrystalline sample Na0.5K0.5NbO3 was synthesized using solid state reaction method. The crystal structure and phase purity was studied by XRD and analysed using Rietveld refinement method. Good agreement was observed between the observed and calculated patterns in Rietveld refinement. The refinement inferred orthorhombic crystal structure with Amm2 space group. The impedance spectroscopy of the sample was performed in frequency range 10 Hz to 7 MHz in temperature range 573K to 703K. The activation energy was obtained to be 0.67eV from the reciprocal temperature variation of dc conductivity which follows the Arrhenius law.

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