Determination of layer-charge density of expandable 2:1 clay minerals in soils and loess sediments using the alkylammonium method

Clay Minerals ◽  
1985 ◽  
Vol 20 (3) ◽  
pp. 291-300 ◽  
Author(s):  
G. Rühlicke ◽  
E. A. Niederbudde
Keyword(s):  
Charge Density ◽  
Clay Minerals ◽  
Adsorption Properties ◽  
Layer Charge ◽  
Basal Spacing ◽  
Adsorption Method ◽  
Resolution Electron ◽  
Fine Clay ◽  
High Resolution Electron Micrographs

AbstractThe alkylammonium adsorption method for the determination of layer-charge density was slightly modified and applied to mixtures of expandable clay minerals (i.e. predominantly 18 Å minerals after glycerol sorption) from two loess samples and two soils (Haplaquept and Aquentic Chromudert) having different K-adsorption properties. The layer-charge density of the so-called 18 Å minerals from these sediments and soil samples varied between −0·23 and −0·85 per formula unit, which suggested the presence of different amounts of vermiculite within the 18 Å minerals. The amounts of these vermiculites were related to K-fixing and K-buffering properties of the different samples. High-resolution electron micrographs of vermiculites saturated with tetradecylammonium exhibited a basal spacing of 25 Å. It was confirmed, that the alkylammonium ions in the interlayers of the vermiculites formed a paraffin-type structure. In the fine clay from the loess samples an interstratification of vermiculite and illitic layers was observed.

Problems in layer-charge determination of montmorillonites

Clay Minerals ◽  
1976 ◽  
Vol 11 (3) ◽  
pp. 173-187 ◽  
Author(s):  
G. Lagaly ◽  
M. Fernandez Gonzalez ◽  
Armin Weiss
Keyword(s):  
Particle Size ◽  
Density Distribution ◽  
Charge Density ◽  
Layer Charge ◽  
Charge Density Distribution ◽  
Charge Distributions ◽  
Charge Determination

AbstractSpanish montmorillonites from Frente Archidona were used to demonstrate the determination of charge density, CEC and, in mixtures, the montmorillonite content by the aikylammonium method. Special attention is directed to heterogeneous montmorillonites and the determination of the charge density distribution. Some problems which arise by application of the method are discussed: relations between layer charge and cation densities, particle size corrections, microstructures and unsymmetric charge distributions in the interlayer spaces.

The use of HREM in studying clay minerals

1990 ◽  
Vol 48 (4) ◽  
pp. 490-491
Author(s):  
Quan Qing Chen ◽  
Xing Lu
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Clay Minerals ◽  
High Resolution Electron Microscopy ◽  
Crystal Structure Analysis ◽  
Simulated Image ◽  
Left Handed ◽  
Resolution Electron ◽  
Fine Clay ◽  
Mixed Layers

A wider scope of clay research has been opened by investigators in various branches of science and technology due to their increasing interest in such materials. Electron microscope is one of the important methods for studying clay and clay minerals. Although a previous contribution of electron microscopy was to clarify the morphology and later electron diffraction (ED) of fine clay particles.However with the continous improvement of instrument and high resolution electron microscopy (HREM) techniques has provided more detailed information of clay minerals. This paper presents the use of HREM in stúdying clay minerals among our research.1. Analysis of the structure of clay minerals Recent advances in crystal structure analysis have indicated that disordered features are commonly revealed to various extents in clay mineral structure, such as polytypes,stacking disorders,mixed-layers.......etc. When the fraction of disordered feature is rather low, which cannot be distinguished by other method such as x-ray diffraction,however by using HREM lattice imaging, ED, and computer simulating (CS), which can be distinguished distinctly and sensitively. Fig.1a shows the structure of kaolinite with enantio morphic types i.e. left-handed and right-handed kaolinite. The computer simulated image (CSI) and electron diffraction pattern (EDP) are included for interpretation. It was also found that dickite is exhibited as intergrowth or stacking faults in the koalinite.

scholarly journals Layer charge robust delamination of organo-clays

RSC Advances ◽  
2018 ◽  
Vol 8 (50) ◽  
pp. 28797-28803 ◽  
Author(s):  
Matthias Daab ◽  
Natalie J. Eichstaedt ◽  
Andreas Edenharter ◽  
Sabine Rosenfeldt ◽  
Josef Breu
Keyword(s):  
Charge Density ◽  
Clay Minerals ◽  
Layer Charge ◽  
Osmotic Swelling

Bulky but hydrophilic organo-cations as interlayer ions of clay minerals allow repulsive osmotic swelling irrespective of the layer charge density.

Modeling and simulation of octahedral Pb inclusions in Al

1995 ◽  
Vol 53 ◽  
pp. 646-647
Author(s):  
S.Q. Xiao ◽  
S. Paciornik ◽  
R. Kilaas ◽  
E. Johnson ◽  
U. Dahmen
Keyword(s):  
Total Sample ◽  
Inclusion Size ◽  
Zone Axis ◽  
Sample Thickness ◽  
Solidification Behavior ◽  
Axis Orientation ◽  
Resolution Electron ◽  
The Matrix ◽  
High Resolution Electron Micrographs

Pb inclusions in Al have been extensively studied for their unusual melting/solidification behavior. Pb inclusions have a cube on cube parallel orientation relationship with the Al matrix and assume cuboctahedral shapes faceted on {111} and {100}. Al and Pb are both fcc structures but with very different lattice parameters: aAl = 0.405 nm, apb = 0.495 nm. Thus 5 Al spacings match approximately 4 Pb spacings giving rise to a moire pattern visible in HREM images.High resolution electron micrographs in the <110> zone axis orientation were recorded on the Berkeley ARM at an accelerating voltage of 800 kV. In this orientation the cuboctahedra project as truncated parallelograms as shown in Fig. 1. Although the four (111) interfaces revealed in Fig. 1 are imaged edge-on, the Al lattice overlaps the Pb lattice above and below, because the other four (111) interfaces are inclined. Therefore, even though the (111)Al lattice is clearly resolved, the determination of inclusion size is not straightforward because the contrast depends on defocus (Δf), particle size (s), depth of the inclusion in the matrix (z) and total sample thickness (t).

The High Resolution Appearance of Biological Substrates

1969 ◽  
Vol 27 ◽  
pp. 416-417
Author(s):  
Glen B. Haydon
Keyword(s):  
High Resolution ◽  
Phase Image ◽  
Biological Structure ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Resolution Electron ◽  
Discrete Structures ◽  
Large Phase ◽  
Biological Substrates ◽  
High Resolution Electron Micrographs

High resolution electron microscopic study of negatively stained macromolecules and thin sections of tissue embedded in a variety of media are difficult to interpret because of the superimposed phase image granularity. Although all of the information concerning the biological structure of interest may be present in a defocused electron micrograph, the high contrast of large phase image granules produced by the substrate makes it impossible to distinguish the phase ‘points’ from discrete structures of the same dimensions. Theory predicts the findings; however, it does not allow an appreciation of the actual appearance of the image under various conditions. Therefore, though perhaps trivial, training of the cheapest computer produced by mass labor has been undertaken in order to learn to appreciate the factors which affect the appearance of the background in high resolution electron micrographs.

Feasibility of Molecular Structure Determination With a High Resolution Electron Microscope

1968 ◽  
Vol 26 ◽  
pp. 338-339
Author(s):  
T. A. Welton
Keyword(s):  
Electron Microscope ◽  
Substrate Surface ◽  
Helical Axis ◽  
Base Plane ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
High Degree ◽  
Degree Of Order ◽  
Purine Pyrimidine

An ultimate design goal for an improved electron microscope, aimed at biological applications, is the determination of the structure of complex bio-molecules. As a prototype of this class of problems, we propose to examine the possibility of reading DNA sequence by an imaginable instrument design. This problem ideally combines absolute importance and relative simplicity, in as much as the problem of enzyme structure seems to be a much more difficult one.The proposed technique involves the deposition on a thin graphite lamina of intact double helical DNA rods. If the structure can be maintained under vacuum conditions, we can then make use of the high degree of order to greatly reduce the work involved in discriminating between the four possible purine-pyrimidine arrangements in each base plane. The phosphorus atoms of the back bone form in projection (the helical axis being necessarily parallel to the substrate surface) two intertwined sinusoids. If these phosphorus atoms have been located up to a certain point on the molecule, we have available excellent information on the orientation of the base plane at that point, and can then locate in projection the key atoms for discrimination of the four alternatives.

High-resolution electron microscopy of the atomic structure of some grain boundaries in Au

1986 ◽  
Vol 44 ◽  
pp. 414-415
Author(s):  
W. Krakow ◽  
D. A. Smith
Keyword(s):  
Atomic Structure ◽  
High Resolution Electron Microscopy ◽  
Image Features ◽  
Image Feature ◽  
Resolution Electron ◽  
Tilt Boundaries ◽  
Processing Techniques ◽  
Atom Position ◽  
Structure Configuration

The successful determination of the atomic structure of [110] tilt boundaries in Au stems from the investigation of microscope performance at intermediate accelerating voltages (200 and 400kV) as well as a detailed understanding of how grain boundary image features depend on dynamical diffraction processes variation with specimen and beam orientations. This success is also facilitated by improving image quality by digital image processing techniques to the point where a structure image is obtained and each atom position is represented by a resolved image feature. Figure 1 shows an example of a low angle (∼10°) Σ = 129/[110] tilt boundary in a ∼250Å Au film, taken under tilted beam brightfield imaging conditions, to illustrate the steps necessary to obtain the atomic structure configuration from the image. The original image of Fig. 1a shows the regular arrangement of strain-field images associated with the cores of ½ [10] primary dislocations which are separated by ∼15Å.

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