scholarly journals The parisite–(Ce) enigma: challenges in the identification of fluorcarbonate minerals

2020 ◽  
Author(s):  
Manuela Zeug ◽  
Lutz Nasdala ◽  
Martin Ende ◽  
Gerlinde Habler ◽  
Christoph Hauzenberger ◽  
...  
Keyword(s):  
Structure Refinement ◽  
X Ray Diffraction ◽  
Height Ratio ◽  
Raman Spectroscopic ◽  
Spectroscopic Analyses ◽  
Transmission Electron ◽  
Correct Assignment ◽  
Disordered Layer ◽  
Stacking Patterns ◽  
Insight Into

Abstract A multi-methodological study was conducted in order to provide further insight into the structural and compositional complexity of rare earth element (REE) fluorcarbonates, with particular attention to their correct assignment to a mineral species. Polycrystals from La Pita Mine, Municipality de Maripí, Boyacá Department, Colombia, show syntaxic intergrowth of parisite–(Ce) with röntgenite–(Ce) and a phase which is assigned to B3S4 (i.e., bastnäsite-3–synchisite-4; still unnamed) fluorcarbonate. Transmission electron microscope (TEM) images reveal well-ordered stacking patterns of two monoclinic polytypes of parisite–(Ce) as well as heavily disordered layer sequences with varying lattice fringe spacings. The crystal structure refinement from single crystal X-ray diffraction data – impeded by twinning, complex stacking patterns, sequential and compositional faults – indicates that the dominant parisite–(Ce) polytype M1 has space group Cc. Parisite–(Ce), the B3S4 phase and röntgenite–(Ce) show different BSE intensities from high to low. Raman spectroscopic analyses of parisite–(Ce), the B3S4 phase and röntgenite–(Ce) reveal different intensity ratios of the three symmetric CO3 stretching bands at around 1100 cm−1. We propose to non-destructively differentiate parisite–(Ce) and röntgenite–(Ce) by their 1092 cm−1 / 1081 cm−1 ν1(CO3) band height ratio.

scholarly journals Synthesis and Characterization of K-Ta Mixed Oxides for Hydrogen Generation in Photocatalysis

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Beata Zielińska ◽  
Ewa Mijowska ◽  
Ryszard J. Kalenczuk
Keyword(s):  
Diffuse Reflectance ◽  
Hydrogen Generation ◽  
Mixed Oxides ◽  
X Ray Diffraction ◽  
X Ray ◽  
Raman Spectroscopic ◽  
Photocatalytic Hydrogen Generation ◽  
Irregular Structure ◽  
Transmission Electron

K-Ta mixed oxides photocatalysts have been prepared by impregnation followed by calcination. The influence of the reaction temperature (450°C–900°C) on the phase formation, crystal morphology, and photocatalytic activity in hydrogen generation of the produced materials was investigated. The detailed analysis has revealed that all products exhibit high crystallinity and irregular structure. Moreover, two different crystal structures of potassium tantalates such as KTaO3and K2Ta4O11were obtained. It was also found that the sample composed of KTaO3and traces of unreacted Ta2O5(annealed at 600°C) exhibits the highest activity in the reaction of photocatalytic hydrogen generation. The crystallographic phases, optical and vibronic properties were examined by X-ray diffraction (XRD) and diffuse reflectance (DR) UV-vis and resonance Raman spectroscopic methods, respectively. Morphology and chemical composition of the produced samples were studied using a high-resolution transmission electron microscope (HR-TEM) and an energy dispersive X-ray spectrometer (EDX) as its mode.

Ideal and Real Structure of Ti5O4(PO4)4: X-ray and HRTEM Investigations

1998 ◽  
Vol 54 (6) ◽  
pp. 722-731 ◽  
Author(s):  
F. Reinauer ◽  
R. Glaum
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Structure Refinement ◽  
Ideal Structure ◽  
Crystal Data ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
The Ideal

The crystal structure of pentatitanium tetraoxide tetrakis(phosphate), Ti5O4(PO4)4, has been determined and refined from X-ray diffraction single-crystal data [P212121 (No. 19), Z = 4, a = 12.8417 (12), b = 14.4195 (13), c = 7.4622 (9) Å (from Guinier photographs); conventional residual R 1 = 0.042 for 2556 Fo > 4σ(Fo ), R 1 = 0.057 for all 3276 independent reflections; 282 parameters; 29 atoms in the asymmetric unit of the ideal structure]. The structure is closely related to those of β-Fe2O(PO4)-type phosphates and synthetic lipscombite, Fe3(PO4)4(OH). While these consist of infinite chains of face-sharing MO6 octahedra, in pentatitanium tetraoxide tetrakis(phosphate) only five-eighths of the octahedral voids are occupied according to □3Ti5O4(PO4)4. Four of the five independent Ti4+O6 show high radial distortion [1.72 ≤ d(Ti−O) ≤ 2.39 Å] and a typical 1 + 4 + 1 distance distribution. The fifth Ti4+O6 is an almost regular octahedron [1.91 ≤ d(Ti−O) ≤ 1.98 Å]. Partial disorder of Ti4+ over the available octahedral voids is revealed by the X-ray structure refinement. High-resolution transmission electron microscopy (HRTEM) investigations confirm this result.

scholarly journals MINERALOGICAL AND SPECTROSCOPIC STUDY OF NESQUEHONITE SYNTHESIZED BY REACTION OF GASEOUS CO2 WITH MG CHLORIDE SOLUTION

2017 ◽  
Vol 50 (4) ◽  
pp. 2009
Author(s):  
V. Skliros ◽  
A. Anagnostopoulou ◽  
P. Tsakiridis ◽  
M. Perraki
Keyword(s):  
Scanning Transmission Electron Microscopy ◽  
Chloride Solution ◽  
Raw Material ◽  
X Ray Diffraction ◽  
X Ray ◽  
Raman Spectroscopic ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Permanent Storage ◽  
Ir And Raman

Nesquehonite, a hydrous carbonate with promising uses such as building raw material and treatment of wastewaters, was synthesized under low pressure conditions by reaction of gaseous CO2 with Mg chloride solution and it was studied by means of X-Ray Diffraction, optical and scanning/transmission electron microscopy, and FTIR and Raman spectroscopic methods. Synthesized nesquehonite forms elongated fibers, exhibiting transparent to translucent diaphaneity and vitreous luster. It is characterized by high crystallinity. IR and Raman spectroscopy indicated the presence of OHand HCO3 - in the crystal structure of nesquehonite. The nesquehonite synthesis described herein constitutes a potential permanent storage of CO2 emissions.

scholarly journals In-site Preparation and Characterization Catalytic- Composite Used for Plastic Waste Degradation to Fuel.

2021 ◽  
Author(s):  
Ameen Abdelrahman ◽  
Asmaa S. Hamouda ◽  
A.H. Zaki
Keyword(s):  
Fixed Bed ◽  
Plastic Waste ◽  
High Density ◽  
Fixed Bed Reactor ◽  
Composite Catalyst ◽  
X Ray Diffraction ◽  
Spectroscopic Analyses ◽  
Transmission Electron ◽  
Waste Degradation ◽  
Gasification Reaction

Abstract In order to get renewable energy from plastic waste, it should find a pathway or create a new composite that is thermally stable, non-toxic, environmentally inexpensive, and highly efficient. Thus, in our research, we work with composite materials that provide a hetero catalyst designed to crack Polyethylene high Density ( PEHD) , which is composed of Metals (Mn, Ag) in Nano scales , and Graphene impregnated inside the PEG matrix. In order to evaluate fabricated composite catalyst, to be applicable on conversion plastic polyethylene high density to gases yields and solid char carbon using pyrolysis and gasification reaction . the process were carried out inside the fixed bed reactor. Various characteristics have been conducted for final products (gases and black char), further spectroscopic analyses like Ultraviolet–visible spectroscopy (UV) , Cyclic voltammetry (CV) , Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD ), and Thermogravimetric analysis (TGA) were investigated for the new composite.

Structural Characterization of Crystalline Si-C-N Films

1997 ◽  
Vol 498 ◽  
Author(s):  
E. G. Wang ◽  
Cheng-Zhang Wang ◽  
Changfeng Chen ◽  
Yan Chen
Keyword(s):  
Electron Microscopy ◽  
Structural Characterization ◽  
Chemical Vapor ◽  
First Principles Calculations ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Hot Filament ◽  
Microscopy Images ◽  
Insight Into

ABSTRACTHigh quality crystalline Si-C-N films on silicon substrate have been synthesized by bias-assisted hot filament chemical vapor deposition (CVD) using a gas mixture of nitrogen and methane. Scanning electron microscopy images show that the Si-C-N clusters are composed of many columnar crystals with hexagonal facets. X-ray diffraction and transmission electron microscopy analyses confirm the formation of Si-C-N crystals with lattice parameters a=7.06Å and c=2.72Å. First principles calculations are performed for β-Si3–nCnN4 (n=0,1,2,3). The calculated results support the experimental structural characterization and provide further insight into the property of the system. With increasing amount of C substitution, the bulk modulus progressively increases to 4.44 Mbar, comparable to that of diamond (4.43 Mbar), and both a and c are reduced but the ratio c/a shows little variation.

Hakite from Příbram, Czech Republic: compositional variability, crystal structure and the role in Se mineralization

2016 ◽  
Vol 80 (6) ◽  
pp. 1115-1128 ◽  
Author(s):  
P. Škácha ◽  
J. Sejkora ◽  
L. Palatinus ◽  
E. Makovicky ◽  
J. Plášil ◽  
...  
Keyword(s):  
Czech Republic ◽  
Diffraction Data ◽  
Empirical Formula ◽  
Structure Refinement ◽  
Sensu Stricto ◽  
Electron Diffraction Data ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Precession Electron Diffraction ◽  
Dominant Member

AbstractHakite, ideally Cu10Hg2Sb4Se13, is a Se-dominant member of the tetrahedrite group occurring at only a few localities in the World. A new occurrence of this mineral in the Příbram uranium and base-metal ore district, Central Bohemia, Czech Republic, is reported in this paper. Hakite was found to be locally abundant and was identified in several samples with Se mineralization. Three chemically distinct types of hakite were distinguished based on electron microprobe study, Hg-rich hakite (hakitesensu stricto), Zn-rich hakite and Cd-rich hakite. Hg-hakite dominates among the samples studied. Its average empirical formula based on 29 apfu (n= 54) is (Cu5.61Ag0.39)∑6.00Cu4.00(Hg1.61Zn0.20Cu0.19Cd0.15Fe0.04)∑2.19(Sb3.85As0.28)∑4.13(Se11.55S1.14)∑12.69. Less common is the Zn-hakite, (Cu5.80Ag0.20)∑6.00Cu4.00(Zn1.33Hg0.42Cd0.22Cu0.18Fe0.01)∑2.16(Sb3.85As0.26)∑4.11(Se10.92S1.81)∑12.73(n= 22), and rare Cd-hakite has an empirical formula (n= 7) of (Cu5.84Ag0.16)∑6.00Cu4.00(Cd1.27Zn0.60Cu0.10Hg0.07Fe0.02)∑2.06(Sb4.00As0.19)∑4.19(Se12.14S0.61)∑12.75. The refined unit cell of Hg-hakite from Příbram, obtained from powder X-ray diffraction data, isa= 10.8783(3) Å withV= 1287.3(1) Å3(Z= 4, for the cubic space groupI4̄3m). Structure refinement from the precession electron diffraction data collected on the transmission electron microscope (R= 24.4% for 424 observed reflections), confirmed that hakite is isostructural with tetrahedrite. The evolution of hydrothermal fluids, from which Se mineralization formed, suggests a distinct enrichment in sulfur and depletion in selenium over the time span of crystallization.

Fabrication of SnS2 Flower Like Nanoflake Assemblies Through Thermal Evaporation

2007 ◽  
Vol 7 (12) ◽  
pp. 4540-4545 ◽  
Author(s):  
Subhajit Biswas ◽  
Soumitra Kar ◽  
Tandra Ghoshal ◽  
Subhadra Chaudhuri
Keyword(s):  
Thermal Evaporation ◽  
Growth Direction ◽  
Vapor Concentration ◽  
X Ray Diffraction ◽  
Electron Microscopic ◽  
X Ray ◽  
Raman Spectroscopic ◽  
Transmission Electron ◽  
Scanning Electron Microscopic ◽  
The Individual

Uniform as well as flower like patterns of SnS2 nanoflakes were produced by a thermal evaporation process. Interpenetrating phenomenon was observed between the individual nanoflakes during the course of their lateral growth. The interpenetrating growth and controlled vapor concentration as well as the substrate temperature leads to the formation of flower like assemblies of SnS2 nanoflakes. Morphology and growth mechanism of the nanostructures were studied by scanning electron microscopic observations at different stages of the nanoflake growth. The produced nanoflakes were characterized by X-ray diffraction, scanning and transmission electron microscopy, and Raman spectroscopic measurements. SnS2 nanoflakes were perfectly single crystalline and growth direction of the nanoflakes was along the {101}-lattice plane.

Structure refinement of the layered composite crystal Sc2B1.1C3.2 in a five-dimensional formalism

2001 ◽  
Vol 57 (4) ◽  
pp. 449-457 ◽  
Author(s):  
Mitsuko Onoda ◽  
Ying Shi ◽  
A. Leithe-Jasper ◽  
Takaho Tanaka
Keyword(s):  
Structural Parameters ◽  
Structure Refinement ◽  
Three Dimensional ◽  
Layered Composite ◽  
Layered Compound ◽  
X Ray Diffraction ◽  
X Ray ◽  
Composite Crystal ◽  
The Difference ◽  
Insight Into

The crystal structure of a layered compound Sc2B1.1C3.2, scandium boride carbide (M r = 140.43), has been re-refined as a commensurate composite crystal using 1795 single-crystal X-ray diffraction intensities with I > 2\sigma(I) collected by Shi, Leithe-Jasper, Bourgeois, Bando & Tanaka [(1999), J. Solid State Chem. 148, 442–449]. The crystal is composed of two layered subsystem structures, i.e. Sc—C—Sc sandwiches and graphite-like layers of the composition B1/3C2/3. The structure refinement was performed in a five-dimensional formalism based on the trigonal superspace group P\bar{3}m1(p00)(0p0)0m0. The unit cell and other crystal data are a = b = 3.387 (1), c = 6.703 (2) Å, V = 66.59 (1) Å3, \boldsigma_{1} = (9/7 0 0), \boldsigma_{2} = (0 9/7 0), Z = 1, D x = 3.501 Mg m−1. Two different three-dimensional sections through the superspace were analyzed, corresponding to two different superstructure models, one with P\bar{3}m1 and the other with P\bar{3}m1. A random distribution of B and C was assumed in the graphite-like layer and 41 structural parameters were introduced. R F /wR F } were 0.0533/0.0482 and 0.0524/0.0476, respectively, for the first and second models. Although the difference between these R F or wR F values was too fine to exclude one of the models definitely, the advantages of using a superspace group were obvious. It not only brought about better convergence of refinement cycles by virtue of fewer parameters, but also gave an insight into the problem of symmetry of the superstructure.

scholarly journals Calcite Nanocrystals Investigated Using X-ray Absorption Spectroscopy

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 490
Author(s):  
Varsha Singh ◽  
Anil Kumar Paidi ◽  
Cheol-Hwee Shim ◽  
So Hee Kim ◽  
Sung Ok Won ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Shape Change ◽  
Spectroscopic Studies ◽  
X Ray Diffraction ◽  
X Ray ◽  
Raman Spectroscopic ◽  
Coordination Numbers ◽  
Transmission Electron ◽  
Local Electronic Structure ◽  
X Ray Absorption

For the present work, calcite nanocrystals were grown by annealing precursors at 500 °C. These precursors were obtained by three different thermal schemes. Among these schemes, two involve heating at 100 °C for 16 h and 16 + 24 h, respectively. In the third scheme, heating was performed at 100 °C for 16 h, followed by annealing at 300 °C for 24 h. X-ray diffraction studies, followed by Fourier transform infrared and Raman spectroscopic studies, exhibited the formation of calcite phase of calcium carbonate. Transmission electron microscopy showed that particle sizes of synthesized calcite nanocrystals were in the range of 25–40 nm. Onsets of shape change were also observed with different thermal schemes, using these measurements. X-ray absorption spectroscopy envisaged that the coordination numbers of Ca-O and Ca-Ca shell were not influenced by the thermal schemes; however, bond lengths of these shells were modified. This study in the near edge region evidenced the manifestation of a local electronic structure of calcite when kept in an open environment, depending upon different thermal schemes.

Effect of Ultraviolet Irradiation on Photo-Physical and Surface Electronic Properties of MoS2

2020 ◽  
Vol 20 (10) ◽  
pp. 6500-6504
Author(s):  
Vijendra Kumar ◽  
R. K. Shukla ◽  
Jyoti Shakya
Keyword(s):  
Electronic Properties ◽  
Uv Light ◽  
X Ray Diffraction ◽  
Kelvin Probe ◽  
Kelvin Probe Microscopy ◽  
Raman Spectroscopic ◽  
Transmission Electron ◽  
Chemical Exfoliation ◽  
Before And After ◽  
Probe Sonication

In this study, exfoliation of molybdenum disulfide (MoS2) using the chemical exfoliation method was successfully achieved via probe sonication followed by centrifugation. The observed ultravioletvisible (UV-Vis) spectra of the MoS2 dispersions indicated the presence of a few layers of MoS2. The morphological, structural, optical and surface electronic properties before and after UV light irradiation were investigated by the technique of X-ray diffraction, the Raman spectroscopic measurements, transmission electron microscopy (TEM), and the scanning Kelvin probe microscopy (SKPM). It was observed that after UV irradiation, the Fermi level moves towards the valence band.

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