Anisotropy of experimentally compressed kaolinite-illite-quartz mixtures

Geophysics ◽  
2009 ◽  
Vol 74 (1) ◽  
pp. D13-D23 ◽  
Author(s):  
Marco Voltolini ◽  
Hans-Rudolf Wenk ◽  
Nazmul Haque Mondol ◽  
Knut Bjørlykke ◽  
Jens Jahren
Keyword(s):  
Single Crystal ◽  
Elastic Properties ◽  
Compaction Pressure ◽  
Clay Content ◽  
Orientation Distribution ◽  
Rietveld Analysis ◽  
Preferred Orientation ◽  
P Wave ◽  
Velocity Anisotropy ◽  
Pole Figures

The anisotropy of physical properties is a well-known characteristic of many clay-bearing rocks. This anisotropy has important implications for elastic properties of rocks and must be considered in seismic modeling. Preferred orientation of clay minerals is an important factor causing anisotropy in clay-bearing rocks such as shales and mudstones that are the main cap rocks of oil reservoirs. The preferred orientation of clays depends mostly on the amount of clays and the degree of compaction. To study the effect of these parameters, we prepared several samples compressing (at two effective vertical stresses) a mixture of clays (illite and kaolinite) and quartz (silt) with different clay/quartz ratios. The preferred orientation of the phases was quantified with Rietveld analysis on synchrotron hard X-ray images. Pole figures for kaolinite and illite display a preferred orientationof clay platelets perpendicular to the compaction direction, increasing in strength with clay content and compaction pressure. Quartz particles have a random orientation distribution. Aggregate elastic properties can be estimated by averaging the single-crystal properties over the orientation distribution obtained from the diffraction data analysis. Calculated P-wave velocity anisotropy ranges from 0% (pure quartz sample) to 44% (pure clay sample, highly compacted), but calculated velocities are much higher than measured velocities. This is attributed to uncertainties about single-crystal elastic properties and oriented micropores and limited grain contacts that are not accounted for in the model. In this work, we present an effective method to obtain quantitative data, helping to evaluate the role of clay percentage and compaction pressure on the anisotropy of elastic properties of clay-bearing rocks.

scholarly journals Preferred orientation of ettringite in concrete fractures

2009 ◽  
Vol 42 (3) ◽  
pp. 429-432 ◽  
Author(s):  
Hans-Rudolf Wenk ◽  
Paulo J. M. Monteiro ◽  
Martin Kunz ◽  
Kai Chen ◽  
Nobumichi Tamura ◽  
...  
Keyword(s):  
Single Crystal ◽  
Elastic Properties ◽  
Elastic Anisotropy ◽  
Rietveld Method ◽  
Orientation Distribution ◽  
Sulfate Attack ◽  
X Ray ◽  
Fracture Surfaces ◽  
Concrete Fractures ◽  
Loss Of Strength

Sulfate attack and the accompanying crystallization of fibrous ettringite [Ca6Al2(OH)12(SO4)3·26H2O] cause cracking and loss of strength in concrete structures. Hard synchrotron X-ray microdiffraction is used to quantify the orientation distribution of ettringite crystals. Diffraction images are analyzed using the Rietveld method to obtain information on textures. The analysis reveals that thecaxes of the trigonal crystallites are preferentially oriented perpendicular to the fracture surfaces. By averaging single-crystal elastic properties over the orientation distribution, it is possible to estimate the elastic anisotropy of ettringite aggregates.

An analysis of preferred orientation in YBa2Cu3O7–x superconducting films deposited by CVD on single-crystal and polycrystalline substrates

1994 ◽  
Vol 9 (4) ◽  
pp. 250-259 ◽  
Author(s):  
E. A. Judson ◽  
D. N. Hill ◽  
R. A. Young ◽  
J. R. Cagle ◽  
W. J. Lackey ◽  
...  
Keyword(s):  
Single Crystal ◽  
Chemical Vapor ◽  
Preferred Orientation ◽  
Superconducting Properties ◽  
High Temperature Anneal ◽  
Pole Figures ◽  
Before And After ◽  
Diffraction Patterns ◽  
A Minor ◽  
Orientation Phenomenon

YBa2Cu3O7–x films were deposited by chemical vapor deposition (CVD) onto single-crystal MgO, single-crystal Al2O3, and polycrystalline Al2O3 substrates, characterized before and after annealing, and tested for their superconducting properties. The preferred orientation in the films was analyzed (i) with pole figures and (ii) by comparison of experimental x-ray powder diffraction patterns with those calculated for the material using the March–Dollase function to model the degree of preferred orientation. Preferred orientation was significant in as-deposited films, with March coefficients ranging from 0.1–0.5 (random orientation would have a coefficient of 1.0). The (006) pole figures of the films on single crystal substrates exhibited uniquely symmetric patterns. On single-crystal MgO before annealing, a minor secondary orientation of (006) poles in the film was observed in a pattern consistent with the symmetry of major crystallographic directions of MgO. On single-crystal Al2O3 after annealing, a “dual orientation” phenomenon was observed. The high-temperature anneal destroyed the orientation and superconducting properties of the CVD films deposited at high temperatures.

Die Struktur epitaktisch aufgedampfter Goldfilme

1976 ◽  
Vol 31 (2) ◽  
pp. 190-195 ◽  
Author(s):  
W. Fischer ◽  
P. Wißmann
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Pole Figure ◽  
Stacking Faults ◽  
Preferred Orientation ◽  
Silicon Substrates ◽  
Gold Films ◽  
Fibre Texture ◽  
Pole Figures ◽  
Sixfold Symmetry

Abstract The texture of 400 Å thick gold films was investigated by plotting the intensities obtained with the help of a texture analyser in a pole figure diagramm. The films had been evaporated under UHV conditions on (111)-, (110)-and (100)-oriented silicon substrates.The gold films always show a preferred (111)-orientation. This preferred orientation, however, may manifest itself in a (111) fibre texture or a single crystal structure due to different orientation and heating pretreatment of the substrate. Quantitative statements are given on crystal misorienta-tion and azimuthal alignment. The sixfold symmetry of the pole figures can be traced back to the influence of twin stacking faults.

Quantitative neutron diffraction texture measurement applied to α-phase alumina and Ti3AlC2

2011 ◽  
Vol 44 (5) ◽  
pp. 1062-1070 ◽  
Author(s):  
JianFeng Zhang ◽  
Erich H. Kisi ◽  
Oliver Kirstein
Keyword(s):  
Single Crystal ◽  
Orientation Distribution ◽  
Distribution Functions ◽  
Pole Density ◽  
Texture Measurement ◽  
Area Detector ◽  
Neutron Diffractometer ◽  
Α Phase ◽  
Pole Figures ◽  
Crystal Properties

Orientation distribution functions, essential for making a quantitative connection between single-crystal and polycrystal properties, have been determined for extruded α-phase alumina, hot-pressed Ti3AlC2and cold isostatically pressed Ti3AlC2using experimental pole figures recorded on the fixed-wavelength neutron diffractometer KOWARI. Some practical improvements to the calculation of the pole-figure density from the raw area-detector data, and for constructing pole figures on ann×n° hemispherical grid, are presented. The textures give some insight into particle flow during manufacture. Directly measured material textures were compared with one-dimensional pole density functions, such as the March and Rietveld functions commonly used for the correction of preferred orientation in Rietveld refinements, as a means of assessing the utility of the latter for the computation of diffraction elastic constants and other polycrystal properties from a given set of single-crystal properties.

scholarly journals Single Crystal Elastic Properties of Hemimorphite, a Novel Hydrous Silicate

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 425
Author(s):  
Yingzhe Li ◽  
Jay D. Bass
Keyword(s):  
Single Crystal ◽  
Elastic Properties ◽  
Wave Velocity ◽  
Elastic Moduli ◽  
Elastic Anisotropy ◽  
Pure Shear ◽  
P Wave ◽  
Upper And Lower Bounds ◽  
Molecular Water ◽  
High Degree

Hemimorphite, with the chemical formula Zn4Si2O7(OH)2·H2O, contains two different types of structurally bound hydrogen: molecular water and hydroxyl. The elastic properties of single-crystal hemimorphite have been determined by Brillouin spectroscopy at ambient conditions, yielding tight constraints on all nine single-crystal elastic moduli (Cij). The Voigt–Reuss–Hill (VRH) averaged isotropic aggregate elastic moduli are KS (VRH) = 74(3) GPa and μ (VRH) = 27(2) GPa, for the adiabatic bulk modulus and shear modulus, respectively. The average of the Hashin–Shtrickman (HS) bounds are Ks (HS) = 74.2(7) GPa and and μ (HS) = 26.5(6) GPa. Hemimorphite displays a high degree of velocity anisotropy. As a result, differences between upper and lower bounds on aggregate properties are large and the main source of uncertainty in Ks and μ. The HS average P wave velocity is VP = 5.61(4) km/s, and the HS S-wave velocity is VS = 2.77(3) km/s. The high degree of elastic anisotropy among the on-diagonal longitudinal and pure shear moduli of hemimorphite are largely explained by its distinctive crystal structure.

Macrotexture Study of Non- and Sintered Pure Nb and Nb3Sn Using Orientation Distribution Function

2014 ◽  
Vol 896 ◽  
pp. 638-641
Author(s):  
Kholifatul Aniswatin ◽  
Doty Dewi Risanti ◽  
Andika Widya Pramono
Keyword(s):  
Distribution Function ◽  
Orientation Distribution Function ◽  
Elevated Temperatures ◽  
Sintered Sample ◽  
Orientation Distribution ◽  
Preferred Orientation ◽  
Sintering Process ◽  
Specific Direction ◽  
Pole Figures ◽  
Compacting Pressure

This research uses pellets of non- and sintered pure Nb and the superconducting intermetallic compound of Nb3Sn. Sintering was undertaken at 700 °C for 96 hours. The texture data were obtained by using XRD Brüker D8 Advance equipped with gonio-texture and interpreted into namely inverse pole figures, pole figures, and orientation distribution function (ODF). In general, the pole figure analysis indicates that sintering process can lead to a change in the crystal orientation distribution from symmetric or random orientation into preferred orientation. Uni-axial compacting pressure in samples prior to sintering favors the appearance of a preferred orientation on a specific direction. However, this texture is not only retained upon subsequent sintering, but can become much more pronounced or weaker due to the crystal growth occurring at elevated temperatures. The main feature of initial texture for pure compacted Nb obtained in this study is Brass, S, and Copper with Brass being the maximum, whereas Cube and Goss appear as minor components. Upon sintering, it has been found that S, Brass, and Copper retained as the dominant ones, with S has been developed and being the maximum. On the contrary, a significant change in texture upon sintering has been obtained for Nb3Sn, namely Copper, S and Brass components with minor Cube and Goss components for initial condition, and Copper, Goss and Brass with minor Cube and S components for sintered sample. It is noted that the Copper intensity of Nb3Sn decreases from 50.4 to 39.3 multiple of random distribution (m.r.d) for the initial and upon sintering conditions, respectively.

Modeling the effects of microscale fabric complexity on the anisotropy of the Eagle Ford Shale

2016 ◽  
Vol 4 (2) ◽  
pp. SE17-SE29 ◽  
Author(s):  
Qi Ren ◽  
Kyle T. Spikes
Keyword(s):  
Clay Minerals ◽  
Elastic Properties ◽  
Elastic Anisotropy ◽  
Anisotropy Parameter ◽  
Clay Content ◽  
Preferred Orientation ◽  
Eagle Ford Shale ◽  
Eagle Ford ◽  
Clay Concentration ◽  
Anisotropic Elastic

Microscale fabric influences the elastic properties of rock formations. The complexity of the microscale fabric of shale results from composition, platy clay minerals, kerogen, and their preferred orientation patterns. This microscale fabric is also the likely cause of the elastic anisotropy of the rock. In this paper, we have developed a comprehensive three-step rock-physics approach to model the anisotropic elastic properties of the Upper Eagle Ford Shale. We started with anisotropic differential effective medium modeling, followed by an orientation correction, and then a pressure adjustment. This method accounts for the microscale fabric of the rock in terms of the complex composition, shape, and alignment of clay minerals, pore space, and kerogen. In addition, we accounted for different pressure-dependent behaviors of P- and S-waves. Our modeling provides anisotropic stiffnesses and pseudologs of anisotropy parameters. The modeling results match the log measurements relatively well. The clay content, kerogen content, and porosity decreased the rock stiffness. The anisotropy increases with kerogen content, but the influence of clay content was more complex. Comparing the anisotropy parameter pseudologs with clay content shows that clay content increases anisotropy at small concentrations; however, the anisotropy stays constant, or even slightly decreases, as the clay content continues to increase. This result suggests that the preferred orientation of clay clusters is preserved at low clay concentration but vanishes at high clay concentration. This method could also be applied to other shales with carefully chosen parameters to model anisotropic elastic properties.

scholarly journals Lattice-Preferred Orientation and Seismic Anisotropy of Minerals in Retrograded Eclogites from Xitieshan, Northwestern China, and Implications for Seismic Reflectance of Rocks in the Subduction Zone

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 380
Author(s):  
Jaeseok Lee ◽  
Haemyeong Jung
Keyword(s):  
Subduction Zones ◽  
Seismic Anisotropy ◽  
Seismic Velocity ◽  
Northwest China ◽  
Preferred Orientation ◽  
P Wave ◽  
Contact Boundary ◽  
Seismic Properties ◽  
Velocity Anisotropy ◽  
Lattice Preferred Orientation

Various rock phases, including those in subducting slabs, impact seismic anisotropy in subduction zones. The seismic velocity and anisotropy of rocks are strongly affected by the lattice-preferred orientation (LPO) of minerals; this was measured in retrograded eclogites from Xitieshan, northwest China, to understand the seismic velocity, anisotropy, and seismic reflectance of the upper part of the subducting slab. For omphacite, an S-type LPO was observed in three samples. For amphibole, the <001> axes were aligned subparallel to the lineation, and the (010) poles were aligned subnormal to foliation. The LPOs of amphibole and omphacite were similar in most samples. The misorientation angle between amphibole and neighboring omphacite was small, and a lack of intracrystalline deformation features was observed in the amphibole. This indicates that the LPO of amphibole was formed by the topotactic growth of amphibole during retrogression of eclogites. The P-wave anisotropy of amphibole in retrograded eclogites was large (approximately 3.7–7.3%). The seismic properties of retrograded eclogites and amphibole were similar, indicating that the seismic properties of retrograded eclogites are strongly affected by the amphibole LPO. The contact boundary between serpentinized peridotites and retrograded eclogites showed a high reflection coefficient, indicating that a reflected seismic wave can be easily detected at this boundary.

MISORIENTATION DISTRIBUTION FUNCTION FOR CUBIC CRYSTALS

2019 ◽  
Vol 85 (5) ◽  
pp. 28-32
Author(s):  
A. S. Kolyanova ◽  
Y. N. Yaltsev
Keyword(s):  
Distribution Function ◽  
Grain Boundaries ◽  
Orientation Distribution ◽  
Recrystallization Annealing ◽  
Misorientation Distribution ◽  
Cubic Crystals ◽  
Special Boundaries ◽  
Pole Figures ◽  
Two Samples ◽  
Euler Space

A calculation method for obtaining the misorientation distribution function (MDF) for cubic crystals which can be used to estimate the presence or absence of special boundaries in the materials is presented. The calculation was carried out for two samples of Al-Mg-Si alloy subjected to various mechanical and thermal treatments: the first sample is subjected to rolling; the second sample is subjected to recrystallization annealing. MDF is calculated for each sample; the results are presented in the Euler space and in the angle-axis space. The novelty of the method consists in the possibility of gaining data on the grain boundaries from X-ray texture analysis without using electron microscopy. A calculation involving only mathematical operations on matrices was performed on the basis of the orientation distribution function restored from incomplete pole figures. It is shown that no special boundaries are observed in the deformed sample, whereas in the recrystallized alloy, special boundaries are detected at Ʃ = 23, 13, and 17. The shortcoming of the proposed method can be attributed to the lack of accurate data on grain boundaries, since all possible orientation in the polycrystal should be taken into account in MDF calculation.

Measurement of growth rates for single crystals and pressed tablets of CuSO4.5 H2O on a rotating disc

1989 ◽  
Vol 54 (11) ◽  
pp. 2951-2961 ◽  
Author(s):  
Miloslav Karel ◽  
Jaroslav Nývlt
Keyword(s):  
Growth Rate ◽  
Single Crystal ◽  
Single Crystals ◽  
Growth Rates ◽  
Diffusion Coefficients ◽  
Preferred Orientation ◽  
Rotating Disc ◽  
Dissolution Rates ◽  
Rates Of Growth ◽  
Good Agreement

Measured growth and dissolution rates of single crystals and tablets were used to calculate the overall linear rates of growth and dissolution of CuSO4.5 H2O crystals. The growth rate for the tablet is by 20% higher than that calculated for the single crystal. It has been concluded that this difference is due to a preferred orientation of crystal faces on the tablet surface. Calculated diffusion coefficients and thicknesses of the diffusion and hydrodynamic layers in the vicinity of the growing or dissolving crystal are in good agreement with published values.

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