Palaeoweathering in slates from the Iberian Hercynian Massif (Spain): investigation by TEM of clay mineral signatures

Clay Minerals ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 435-451 ◽  
Author(s):  
M. A. Vicente ◽  
F. Elsass ◽  
E. Molina ◽  
M. Robert
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Climatic Conditions ◽  
Subtropical Climate ◽  
Lower Stage ◽  
Transmission Electron ◽  
Analytical Electron ◽  
Tropical Areas ◽  
Well Differentiated ◽  
Confined Environment

AbstractPalaeoweathering profiles are widely represented in the Iberian meseta. Transmission electron microscopy (TEM) and analytical electron microscopy (AEM) were used to describe the mechanisms governing the processes involved in the formation of one of these weathering profiles developed over slates of the Iberian Hercynian Massif. Three well-differentiated weathering stages were distinguished, based upon well-defined mineralogical signatures characteristic of primary or secondary minerals. The lower stage is characterized by fresh green slates composed of Fe-chlorite, micas, quartz and feldspars. The soft slates represent an intermediate weathering stage. A confined environment has permitted the development of smectite from the different primary phyllosilicates, both by neoformation of montmorillonite and transformation into beidellite. In the upper part of the profile, the red slates are the most weathered. A tropical or subtropical climate has resulted in the formation of kaolinite and abundant iron oxides over several metres. The present study demonstrates that the three identified weathering stages were formed under the same climatic conditions. Such ‘toposequences’ are developed at the present time in tropical areas (Bocquier, 1971).

Evidence of a Precursor in the Neoformation of Palygorskite — New Data by Analytical Electron Microscopy

Clay Minerals ◽  
1994 ◽  
Vol 29 (2) ◽  
pp. 255-264 ◽  
Author(s):  
M. Suarez ◽  
J. M. Martin Pozas ◽  
M. Robert ◽  
F. Elsass
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Arid Environment ◽  
Relative Increase ◽  
Climatic Conditions ◽  
Early Diagenesis ◽  
Alluvial Fan ◽  
Transmission Electron ◽  
Analytical Electron ◽  
Small Basin

AbstractThe rocks of the palygorskite deposit at Bercimuel (Segovia, Spain) have been studied by transmission electron microscopy and microanalysis. These rocks correspond to the zone of convergence of two alluvial fan systems that have filled the small basin of the River Riaza and would originally have been composed of illite and quartz silts. Among the accumulations of palygorskite it is possible to observe surrounded particles of micromicas that have undergone dissolution and opening thereby giving rise to disordered illite-smectite mixed-layer clays. This process continued up to the individualization of structural relics formed of units of 1–5 layers. At the same time, the chemical composition was modified with a loss of K and Al and a relative increase in Si and Mg, progressively evolving towards the composition of palygorskite. The paleogeographic position of the deposits, and the climatic conditions (arid environment), appear to be the dominant factors in the neoformation of palygorskite by alteration of the original sediments. The basic mineralogical process could be referred to as ‘early diagenesis’ in the formation of calcretes.

The effect of small additions of Cu on precipitation in Al-Mg-Si alloys

1990 ◽  
Vol 48 (2) ◽  
pp. 442-443
Author(s):  
M. Tamizifar ◽  
G. Cliff ◽  
R.W. Devenish ◽  
G.W. Lorimer
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Scanning Transmission Electron Microscope ◽  
Argon Atmosphere ◽  
Age Hardening ◽  
X Ray ◽  
Transmission Electron ◽  
Heat Treated ◽  
Analytical Electron ◽  
Scanning Transmission

Small additions of copper, <1 wt%, have a pronounced effect on the ageing response of Al-Mg-Si alloys. The object of the present investigation was to study the effect of additions of copper up to 0.5 wt% on the ageing response of a series of Al-Mg-Si alloys and to use high resolution analytical electron microscopy to determine the composition of the age hardening precipitates.The composition of the alloys investigated is given in Table 1. The alloys were heat treated in an argon atmosphere for 30m, water quenched and immediately aged either at 180°C for 15 h or given a duplex treatment of 180°C for 15 h followed by 350°C for 2 h2. The double-ageing treatment was similar to that carried out by Dumolt et al. Analyses of the precipitation were carried out with a HB 501 Scanning Transmission Electron Microscope. X-ray peak integrals were converted into weight fractions using the ratio technique of Cliff and Lorimer.

scholarly journals Analytical High-resolution Electron Microscopy Reveals Organ-specific Nanoceria Bioprocessing

2017 ◽  
Vol 46 (1) ◽  
pp. 47-61 ◽  
Author(s):  
Uschi M. Graham ◽  
Robert A. Yokel ◽  
Alan K. Dozier ◽  
Lawrence Drummy ◽  
Krishnamurthy Mahalingam ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Analytical Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Dark Field ◽  
Transmission Electron ◽  
Analytical Electron ◽  
Organ Specific

This is the first utilization of advanced analytical electron microscopy methods, including high-resolution transmission electron microscopy, high-angle annular dark field scanning transmission electron microscopy, electron energy loss spectroscopy, and energy-dispersive X-ray spectroscopy mapping to characterize the organ-specific bioprocessing of a relatively inert nanomaterial (nanoceria). Liver and spleen samples from rats given a single intravenous infusion of nanoceria were obtained after prolonged (90 days) in vivo exposure. These advanced analytical electron microscopy methods were applied to elucidate the organ-specific cellular and subcellular fate of nanoceria after its uptake. Nanoceria is bioprocessed differently in the spleen than in the liver.

Mixed-layer mica-chlorite in very low-grade metaclastites from the Malàguide Complex (Betic Cordilleras, Spain)

Clay Minerals ◽  
2001 ◽  
Vol 36 (3) ◽  
pp. 307-324 ◽  
Author(s):  
M. D. Ruiz Cruz
Keyword(s):  
Electron Microscopy ◽  
Mixed Layer ◽  
Analytical Electron Microscopy ◽  
Low Grade ◽  
X Ray ◽  
Betic Cordilleras ◽  
Transmission Electron ◽  
Analytical Electron ◽  
Microscopy Data ◽  
Ray Patterns

AbstractMixed-layered phyllosilicates with composition intermediate between mica and chlorite were identified in very low-grade metaclastites from the Malàguide Complex (Betic Cordilleras, Spain), and studied by X-ray diffraction, and transmission and analytical electron microscopy. They occur both as small grains in the rock matrix, and associated with muscovitechlorite stacks. Transmission electron microscope observations revealed a transition from chlorite to ordered 1:1 interstratifications through complex 1:2 and 1:3 interstratifications. Analytical electron microscopy data indicate a composition slightly different from the sum of discrete trioctahedral chlorite and dioctahedral mica. The types of layer transitions suggest that mixed-layer formation included two main processes: (1) the replacement of a brucite sheet by a cation sheet in the chlorite structure; and (2) the precipitation of mica-like layers between the chlorite layers. The strongest diffraction lines in oriented X-ray patterns are: 12.60 Å (002), 7.98 Å (003), 4.82 Å (005) and 3.48 Å (007).

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.

Structural study of deactivation of gallosilicate catalysts

1993 ◽  
Vol 51 ◽  
pp. 726-727
Author(s):  
C. Choi-Feng ◽  
J. B. Hall ◽  
B. J. Huggins ◽  
D. Li ◽  
J. A. Kaduk ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Molecular Sieves ◽  
Molecular Sieve ◽  
Analytical Electron Microscopy ◽  
Light Olefins ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Analytical Electron ◽  
Low Reaction Temperature ◽  
Different Temperatures

Gallosilicate molecular sieves with an MFI structure are very promising catalysts for upgrading light olefins and paraffins to aromatics. Gallosilicate catalysts are quite stable at low reaction temperature, however, when subjected to high temperature, gallosilicate catalysts deactivate rapidly. The activity and selectivity of these catalysts are greatly influenced by both framework and non-framework gallium. Although the framework gallium imparts acidity to the sieve, the nature of the non-framework gallium is unclear. In the present study, combined techniques of analytical electron microscopy (AEM), high resolution transmission electron microscopy (HREM) and X-ray diffraction (XRD) have been applied to study the fate of framework and non-framework gallium in progressively deactivated gallosilicate molecular sieve catalysts. To study this progressive process, fresh gallosilicate molecular sieve and the gallosilicate catalysts (with 40% Cab-O-Sil matrix) subjected to steaming treatments at different temperatures and durations were characterized.The microstructure of fresh gallosilicate catalysts consists of highly crystalline molecular sieve which is uniformly distributed in the amorphous supporting matrix (Fig. 1).

An Illuminating System of a 100-kV Analytical Electron Microscope with a Field-Emission Electron Gun

1990 ◽  
Vol 48 (1) ◽  
pp. 122-123
Author(s):  
A. Delong ◽  
J. Chmelík ◽  
V. Kolařík
Keyword(s):  
Electron Microscopy ◽  
Field Emission ◽  
Analytical Electron Microscopy ◽  
Electron Gun ◽  
Transmission Mode ◽  
Resolving Power ◽  
Objective Lens ◽  
Transmission Electron ◽  
Analytical Electron ◽  
Illuminating System

Our aim was to design a microscope for application in both the classical transmission electron microscopy (CTEM) and in the analytical electron microscopy having in the scanning modes (SEM, STEM) a resolving power approaching that in the CTEM. The problem can be optimally solved by using the field emission source of electrons. The illuminating system and the objective lens have the following parameters:a) The resolving power of the objective lens in the transmission mode is as high as 3.5 Å.b) The optical aberrations of the pre—field of the objective lens and of the set of condenser lenses allow a resolution of approx. 5 Å to be achieved in the scanning mode.c) The illuminated area of the specimen observed in the transmission mode is large enough to allow operation with the objective lens switched on at a magnification 1000 x.

Sign in / Sign up

Export Citation Format

Share Document