scholarly journals The effect of the octahedral cations on the dimensions of the palygorskite cell

Clay Minerals ◽  
2007 ◽  
Vol 42 (3) ◽  
pp. 287-297 ◽  
Author(s):  
M. Suárez ◽  
E. García-Romero ◽  
M. Sánchez Del Río ◽  
P. Martinetto ◽  
E. Dooryhée
Keyword(s):  
Analytical Electron Microscopy ◽  
Chemical Compositions ◽  
X Ray Diffraction ◽  
Ionic Radii ◽  
Octahedral Sheet ◽  
X Ray ◽  
Linear Dependency ◽  
Octahedral Cation ◽  
Analytical Electron ◽  
Octahedral Cations

AbstractHigh-resolution synchrotron X-ray diffraction recorded on a collection of palygorskites with different chemical compositions (obtained by analytical electron microscopy) permits unambiguous correlation of the crystallographic parameters a (or a sin β if a monoclinic phase is considered) with the nature of the octahedral sheet, i.e. with both the number of octahedral positions that are occupied and the type of octahedral cation. No significant changes in the lattice parameters b and c are observed. The unit cell modification consists essentially of an expansion in a as the number of cations with larger ionic radii (Mg2+ and Fe3+) predominates over smaller cations (Al3+). A linear dependency of a (or a sin β) on the chemical composition of the octahedral sheet was obtained that can be used for classifying palygorskite into compositional groups, using only conventional diffraction data, without the need for chemical analyses.

Characterization and crystal chemistry of an Fe-rich montmorillonite from Ölberg, Germany

Clay Minerals ◽  
2002 ◽  
Vol 37 (2) ◽  
pp. 283-297 ◽  
Author(s):  
S. Petit ◽  
J . Caillaud ◽  
D. Righi ◽  
J . Madejová ◽  
F. Elsass ◽  
...  
Keyword(s):  
Analytical Electron Microscopy ◽  
Major Constituent ◽  
X Ray Diffraction ◽  
Progressive Reduction ◽  
X Ray ◽  
Octahedral Cation ◽  
Analytical Electron ◽  
Minor Portion ◽  
A Minor ◽  
Two Populations

AbstractAn Fe-rich smectite from Ölberg (Germany) was characterized using X-ray diffraction, infrared spectroscopy and analytical electron microscopy. Progressive reduction of the octahedral charge was performed through the Hofmann & Klemen effect at increasing temperatures. The sample was heterogeneous, consisting of two smectite populations. One population, which comprises a minor portion of the sample, is an ‘Fe3+-montmorillonite’ with little or no tetrahedral charge and Fe3+ as the major octahedral cation. The other population, a major constituent of the sample, contains less Mg and more Al than the first one and exhibits some tetrahedral charge. This fraction may be considered as an inter-grade between nontronite (dominant tetrahedral charge) and Fe3+-montmorillonite (dominant octahedral charge). These two populations may occur as separate particles but also as interstratified layers.

Analysis of IN-SITU Converted Chrysotile Asbestos Fibers in Sprayed on Fireproofing

1998 ◽  
Vol 4 (S2) ◽  
pp. 480-481
Author(s):  
R. L. Sabatini ◽  
Toshi Sugama ◽  
Leonidas Petrakis
Keyword(s):  
Environmental Protection Agency ◽  
Analytical Electron Microscopy ◽  
Polarized Light ◽  
X Ray Diffraction ◽  
Protection Agency ◽  
Glassy Material ◽  
X Ray ◽  
Asbestos Fibers ◽  
Analytical Electron

A BNL-Grace process has been developed to chemically convert in-situ, the chrysotile fibers of sprayed-on fireproofing products to an unregulated glassy material. The effectiveness of this process has been convincingly demonstrated using Analytical Electron Microscopy and X-Ray Diffraction techniques.Asbestos minerals were used in fireproofing materials because of their excellent physical properties including fire resistance, high tensile strength, heat and electrical insulation, and resistance to acids and alkali. But in 1975 the Environmental Protection Agency began regulating materials containing > 1% asbestos.The new in-situ BNL-Grace process, which uses a foamy solution sprayed directly onto asbestos-containing fireproofing chemically digests essentially all the asbestos fibers, transforming them into harmless materials. After treatment, the fireproofing is no longer a regulated material. The process produces essentially no waste.Our problem was to demonstrate that all of the asbestos was converted and that the remaining materials were no longer regulated. Typical analysis methods use conventional optical and Polarized Light Microscopy (PLM) to measure and observe fibers.

Transient Phase Formation During the Growth of Epitaxial CoSi2 by Annealing of Co/Ti Bi-Layers on (100) Si

1995 ◽  
Vol 402 ◽  
Author(s):  
D. J. Miller ◽  
T. I. Selinder ◽  
K. E. Gray
Keyword(s):  
Electron Microscopy ◽  
Reaction Pathway ◽  
Spinel Phase ◽  
Analytical Electron Microscopy ◽  
Inert Gases ◽  
Native Oxide ◽  
Transient Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Analytical Electron

AbstractPhase evolution during the annealing of Co/Ti bi-layers on (100) Si has been studied by x-ray diffraction and analytical electron microscopy. X-ray diffraction performed in situ during annealing revealed a reaction pathway involving the formation of a transient phase when epitaxial CoSi2 films were grown. Analytical electron microscopy was used to identify this phase as a spinel-related phase, isostructural with Co2TiO4. This phase grows as a result of the presence of the Ti interlayer and a small amount of oxygen from the annealing ambient. Annealing in vacuum or other purified inert gases yielded polycrystalline CoSi2 films which form via a different reaction pathway that does not involve a spinel phase. This spinel phase may serve both to reduce the native oxide from the underlying Si substrate and to control interdiffusion between Si and Co during the reaction, thereby promoting epitaxial growth.

Effect of additives on the polytypic transformation of pressureless sintered silicon carbide

1984 ◽  
Vol 42 ◽  
pp. 414-415
Author(s):  
S. Shinozaki ◽  
W. T. Donlon ◽  
C. R. Peters ◽  
R. M. Williams ◽  
B. N. Juterbock
Keyword(s):  
Silicon Carbide ◽  
Analytical Electron Microscopy ◽  
Metallic Aluminum ◽  
X Ray Diffraction ◽  
X Ray ◽  
Effect Of Additives ◽  
Heat Treated ◽  
Analytical Electron ◽  
Boundary Chemistry ◽  
Sintered Silicon

The influence of metallic aluminum (Al) and silicon (Si) additives on the polytype distributions in silicon carbide (SiC) has been investigated. Tajima and Kingery and Shinozaki and Kinsman have shown, respectively, that 4H polytype becomes predominant when SiC materials are heat-treated in Al- or Si-rich environments. Quantitative x-ray diffraction analysis of polytype distributions has revealed that when β-SiC powder with an Al addition is sintered near 1950°C, the 15R polytype increases considerably and the 4H polytype becomes predominant above 1950°C. The correlations between polytype distributions in SiC grains and grain boundary chemistry have been studied using analytical electron microscopy.

Analytical Electron Microscopy of Automotive Catalysts

1987 ◽  
Vol 45 ◽  
pp. 198-199
Author(s):  
Y. L. Chen ◽  
B. R. Powell
Keyword(s):  
Automotive Industry ◽  
Catalyst Deactivation ◽  
Analytical Electron Microscopy ◽  
Particle Growth ◽  
X Ray Diffraction ◽  
Engine Exhaust ◽  
X Ray ◽  
Exhaust Gases ◽  
Analytical Electron ◽  
Catalyst Poisons

The automotive industry uses catalytic converters to reduce the amounts of regulated emissions that are released to the atmosphere from engine exhaust gases. However, given the presence of catalyst poisons in the exhaust gases and operating temperatures in the converter that frequently exceed 700 °C, durability is a major concern for the catalyst. A detailed understanding of the catalyst deactivation mechanisms (poisoning and particle growth of noble metal particles) is essential to the development of more durable catalysts.Most studies of catalyst deactivation have relied on bulk analytical characterization techniques such as chemisorption, chemical analysis, and x-ray diffraction. Unfortunately, these conventional techniques yield ambiguous and incomplete information about the catalyst because they fail to give a description of the catalyst at the microscopic level where catalysis occurs.

Nickel-containing montmorillonites and chlorites from Brazil, with remarks on schuchardtite

1975 ◽  
Vol 40 (310) ◽  
pp. 141-152 ◽  
Author(s):  
G. W. Brindley ◽  
Jefferson V. De Souza
Keyword(s):  
Structural Formula ◽  
Layer Charge ◽  
Basal Spacing ◽  
Chemical Compositions ◽  
X Ray Diffraction ◽  
Octahedral Sheet ◽  
X Ray ◽  
Crystalline Forms ◽  
Polytype Structure ◽  
Good Agreement

SummaryClay-like, hydrous nickel silicates from Niquelandia, Goias, Brazil, and from Jacupiranga, São Paulo, Brazil, arc examined by X-ray diffraction, chemical analysis, and thermogravimetric methods. The nickel silicates from Niquelandia are ferric iron montmorillonites, with nickel in the octahedral positions and, to a lesser extent, in interlayer positions. The chemical compositions of samples dried at 110°C average (Mg0.15Ni0.08Ca0.015Na0.005) (Fe0.92IIIFe0.025IIAl0.55Mg0.37Ni0.22) (Si3.88Al0.12)O10(OH)2(H2O)0.93. The layer charge originates largely in the octahedral sheet. The cation-exchange capacities average 107 me/100 g clay (110°C). These minerals differ from non-tronites, in which the layer charge originates mainly in the tetrahedral sheets.The nickel silicates from Jacupiranga resemble chlorites, with a non-expanding basal spacing of 14·2-14·3 Å. The better crystalline forms give X-ray data in good agreement with a la polytype structure, which is consistent with their formation by low-temperature processes. Chemical formulae derived on the basis of O10(OH)8 give an average of 5·47 cations in octahedral positions. Thermogravimetric measurements show up to 4% H2O lost between 110 and 500 °C. These results suggest a partial vermiculitization of the interlayer sheets. A new method of calculating a structural formula is developed that gives an interlayer composition of the form R1.75(OH)3.75(H2O)1.14, with (OH + H2O)/R = 2·80, which approaches the ratio for a dioctahedral sheet structure.A comparison of these defect chlorites with available data on schuchardtites shows many similarities; however, schuchardtite is not yet sufficiently well denned for the Jacupiranga chlorites to be given this name.

Origin of mixed-layered (R1) muscovite-chlorite in an anchizonal slate from Puncoviscana Formation (Salta Province, Argentina)

Clay Minerals ◽  
2005 ◽  
Vol 40 (3) ◽  
pp. 317-332 ◽  
Author(s):  
M. Do Campo ◽  
F. Nieto
Keyword(s):  
Electron Microscopy ◽  
Mixed Layer ◽  
Analytical Electron Microscopy ◽  
Aqueous Fluid ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Analytical Electron ◽  
Dioctahedral Mica ◽  
Mixed Layering

AbstractMica-chlorite mixed-layering was identified by X-ray diffraction (XRD) as a major or subordinate constituent in several slates of the Puncoviscana Formation from Sierra de Mojotoro (Eastern Cordillera, NW Argentina). In order to determine the crystallochemical characteristics of these mixed-layered sequences and interpret their petrological meaning, anchizonal slate P90 was chosen for TEM observations. In this slate, dioctahedral mica and chlorite form interleaved phyllosilicate grains (IPG) or stacks, up to 110 um long, preferentially oriented with (001) planes at a high angle to the slaty cleavage but also oblique to S0.In agreement with XRD results, the main phyllosilicates identified by transmission electron microscopy (TEM) were dioctahedral mica and random mixed-layer muscovite-chlorite, with chlorite in subordinate amounts and scarce smectite. In the lattice-fringe images of mixed-layer packets, a sequence of irregular stacking that produced apparent 24 Å (10 + 14) layers was observed, but it was frequently possible to distinguish the 10 Å layers from adjacent 14 Å layers. In nearly all packets, 14 Å layers prevail, exhibiting 14 Å:10 Å ratios between 1:1 and 3:1. Some elongated lenticular fissures which are probably a consequence of layer collapse caused by the TEM vacuum were identified in these packets. The straight, continuous appearance of lattice fringes plus the scarce evidence of collapsed layers identified suggest that these packets correspond principally to mixed-layer muscovite-chlorite, which is confirmed by analytical electron microscopy analyses. However, smectite-like layers are probably the third component of some of these mixed-layer sequences, which may account for their high Si and low (Fe + Mg) contents, their low interlayer charge in relation to theoretical interlayer muscovite-chlorite, and for the presence of Ca in the interlayer site.Textural relationships between chlorite and muscovite packets in IPG along with the observed transformations from 14 Å to 10 Å along the layer, is compatible with a prograde metamorphic replacement of chlorite in stacks by dioctahedral mica layers, probably in the presence of an aqueous fluid.

X-ray diffraction effect on EDX quantitative analysis of crystals

1984 ◽  
Vol 42 ◽  
pp. 580-581
Author(s):  
T. Tanji ◽  
K. Yada
Keyword(s):  
Thin Film ◽  
Quantitative Analysis ◽  
Analytical Electron Microscopy ◽  
Diffraction Effect ◽  
X Ray Diffraction ◽  
Accurate Analysis ◽  
X Ray ◽  
Analytical Electron ◽  
Narrow Area ◽  
Good Agreement

Analytical electron microscopy with energy dispersive x-ray analyzer (EDX) has been value for the elemental analysis. It has an advantage to be able to analyze the very narrow area of the specimen and is used often for the study of localization of the components. In the case of the quantitative analysis of bulky specimens theoretical approximations for the absorption effect and the fluorescent excitation have been almost established. For thin film specimens spectra obtained by TEM or STEM have only to be corrected on the effect of atomic number (Thin Film Approximation), although for more accurate analysis and for the thickish specimen above-mentioned two effects which, strongly depend on the thickness have to be taken into account. Some reports have shown good agreement with the results of quantitative analysis by EDX and that of chemical analysis, whereas it is observed sometimes that the results obtained are distributed more than several atomic percent.

Sublattice occupancies of Pd in Cu0.5Au0.5−xPdx alloys by ALCHEMI

1989 ◽  
Vol 47 ◽  
pp. 234-235
Author(s):  
J. Bentley ◽  
K. Hisatsune
Keyword(s):  
Analytical Electron Microscopy ◽  
Axial Ratio ◽  
Theoretical Modelling ◽  
X Ray Diffraction ◽  
Ion Milling ◽  
X Ray ◽  
Analytical Electron ◽  
The Face ◽  
Face Centered ◽  
Palladium Content

The composition dependence of the lattice parameters of Cu0.5Au0.5−xPdx (0<x<0.25) alloys with the face-centered tetragonal ordered L10 structure has been measured by X-ray diffraction. The results confirm the behavior reported earlier by Nakahigashi et al. Whereas the unit cell volume decreases monotonically with increasing palladium content, the axial ratio c/a exhibits a maximum at about 4 at. % Pd, corresponding to local minimum and maximum values for a and c, respectively. In theoretical modelling of this behavior it was assumed that Pd atoms were randomly interchangeable with only Au atoms. Several techniques, including the ALCHEMI method, are being used to measure directly the sublattice occupancy of palladium.Electropolishing with various solutions failed to produce good quality specimens for analytical electron microscopy (AEM). Ion milling of specimens previously electropolished with an electrolyte of 10% perchloric acid in acetic acid was more successful. Analyses were performed with Philips EM400T/FEG and CM12/STEM instruments and EDAX 9100/70 and 9900 energy dispersive X-ray microanalysis systems.

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