57 research outputs found
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Plasma Spraying of Kaolinite for Preparing Reactive Alumino-Silicate Glass Coatings
Thermally treated kaolinite is used to develop a range of alumino-silicate-based precursor materials but its behavior during plasma spraying has not been well-researched. In this study, two types of kaolinite samples were investigated in the form of low defect (KGa-1b) and high defect (KGa-2) varieties. The extreme temperatures of the plasma stream (up to 20 000 K) induced flash melting to produce a highly porous alumino-silicate glass without any crystallization of new AlâSi oxide minerals. The glass is comprised largely of intact or deformed spheres (average diameters 1.14â1.44 ÎŒm), which indicates rapid quenching and solidification before impact. The subspherical structures contain up to 40 % closed pore space caused by the rapid escape of water during melting. The low-density, porous alumino-silicate glass coatings with predicted specific surface areas (>0.95 m2/g) and hardnesses >1.8 GPa represent a potentially reactive but physically stable substrate ideal for further chemical functionalization
Origin and significance of clayâcoated fractures in mudrock fragments of the SAFOD borehole (Parkfield, California)
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95148/1/grl21674.pd
Simulating permeability reduction by clay mineral nanopores in a tight sandstone by combining computer X-ray microtomography and focussed ion beam scanning electron microscopy imaging
Computer X-ray microtomography (”XCT) represents a powerful tool for investigating the physical properties of porous rocks. While calculated porosities determined by this method typically match experimental measurements, computed permeabilities are often overestimated by more than 1 order of magnitude. This effect increases towards smaller pore sizes, as shown in this study, in which nanostructural features related to clay minerals reduce the permeability of tight reservoir sandstone samples. Focussed ion beam scanning electron microscopy (FIB-SEM) tomography was applied to determine the permeability effects of illites at the nanometre scale, and NavierâStokes equations were applied to calculate the permeability of these domains. With these data, microporous domains (porous voxels) were defined using microtomography images of a tight reservoir sample. The distribution of these domains could be extrapolated by calibration against size distributions measured in FIB-SEM images. For this, we assumed a mean permeability for the dominant clay mineral (illite) in the rock and assigned it to the microporous domains within the structure. The results prove the applicability of our novel approach by combining FIB-SEM with X-ray tomographic rock core scans to achieve a good correspondence between measured and simulated permeabilities. This methodology results in a more accurate representation of reservoir rock permeability in comparison to that estimated purely based on ”XCT images
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Porosity and distribution of water in perlite from the island of Milos, Greece
A perlite sample representative of an operating mine in Milos was investigated with respect to the type and spatial distribution of water. A set of different methods was used which finally provided a consistent view on the water at least in this perlite. Infrared spectroscopy showed the presence of different water species (molecular water and hydroxyl groups / strongly bound water). The presence of more than 0.5 mass% smectite, however, could be excluded considering the cation exchange capacity results. The dehydration measured by thermal analysis occurred over a wide range of temperatures hence confirming the infrared spectroscopical results. Both methods point to the existence of a continuous spectrum of water binding energies. The spatial distribution of water and/or pores was investigated using different methods (CT: computer tomography, FIB: scanning electron microscopy including focused ion beam technology, IRM: infrared microscopy). Computer tomography (CT) showed large macropores (20 â 100 ÎŒm) and additionally revealed a mottled microstructure of the silicate matrix with low density areas up to a few ÎŒm in diameter. Scanning electron microscopy (FIB) confirmed the presence of ÎŒm sized pores and IRM showed the filling of these pores with water. In summary, two types of pores were found. Airfilled 20 â 100 ÎŒm pores and ÎŒm-sized pores disseminated in the glass matrix containing at least some water. Porosity measurements indicate a total porosity of 26 Vol%, 11 Vol% corresponding to the ÎŒm-sized pores. It remains unsolved wether the water in the ÎŒm-sized pores entered after or throughout perlite formation. However, the pores are sealed and no indications of cracks were found which indicated a primary source of the water, i.e. water was probably entrapped by quenching of the lava. The water in these pores may be the main reason for the thermal expandability which results in the extraordinarily porous expanded perlite building materials
Hydrogen and 40Ar/39Ar isotope evidence for multiple and protracted paleofluid flow events within the longâlived North Anatolian Keirogen (Turkey)
We present a new approach to identifying the source and age of paleofluids associated with lowâtemperature deformation in the brittle crust, using hydrogen isotopic compositions (ÎŽD) and 40Ar/39Ar geochronology of authigenic illite in clay gougeâbearing fault zones. The procedure involves grainâsize separation, polytype modeling, and isotopic analysis, creating a mixing line that is used to extrapolate to ÎŽD and age of pure authigenic and detrital material. We use this method on samples collected along the surface trace of today's North Anatolian Fault (NAF). ÎŽD values of the authigenic illite population, obtained by extrapolation, are â89â±â3â°, â90â±â2â°, and â97â±â2â° (VSMOW) for samples KSL, RES4â1, and G1G2, respectively. These correspond to ÎŽD fluid values of â62â° to â85â° for the temperature range of 125°Câ±â25°, indistinguishable from presentâday precipitation values. ÎŽD values of the detrital illite population are â45â±â13â°, â60â±â6â°, and â64â±â6â° for samples KSL, G1G2, and RES4â1, respectively. Corresponding ÎŽD fluid values at 300°C are â26â° to â45â° and match values from adjacent metamorphic terranes. Corresponding clay gouge ages are 41.4â±â3.4 Ma (authigenic) and 95.8â±â7.7 Ma (detrital) for sample G2 and 24.6â±â1.6 Ma (authigenic) and 96.5â±â3.8 Ma (detrital) for sample RES4â1, demonstrating a long history of meteoric fluid infiltration in the area. We conclude that today's NAF incorporated preexisting, weak clayârich rocks that represent earlier mineralizing fluid events. The samples preserve at least three fluid flow pulses since the Eocene and indicate that meteoric fluid has been circulating in the upper crust in the North Anatolian Keirogen since that time.Key Points:Illite preserves the hydrogen isotopic signature and age of paleofluids in the earth's upper crustThree fluid events are pinpointed in the NAKThe NAF exploited zones of preexisting weak clay material during its formationPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/112210/1/ggge20754.pd
Constraints on mineralization, fluidârock interaction, and mass transfer during faulting at 2â3 km depth from the SAFOD drill hole
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94888/1/jgrb15975.pd
Influence of phyllosilicate mineral assemblages, fabrics, and fluids on the behavior of the Punchbowl fault, southern California
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95206/1/jgrb13457.pd
The Development of Criminal Style in Adolescence and Young Adulthood: Separating the Lemmings from the Loners
Despite broad consensus that most juvenile crimes are committed with peers, many questions regarding developmental and individual differences in criminal style (i.e., co-offending vs. solo offending) remain unanswered. Using prospective 3-year longitudinal data from 937 14- to 17-year-old serious male offenders, the present study investigates whether youths tend to offend alone, in groups, or a combination of the two; whether these patterns change with age; and whether youths who engage in a particular style share distinguishing characteristics. Trajectory analyses examining criminal styles over age revealed that, while most youth evinced both types of offending, two distinct groups emerged: an increasingly solo offender trajectory (83%); and a mixed style offender trajectory (17%). Alternate analyses revealed (5.5%) exclusively solo offenders (i.e., only committed solo offenses over 3Â years). There were no significant differences between groups in individualsâ reported number of friends, quality of friendships, or extraversion. However, the increasingly solo and exclusively solo offenders reported more psychosocial maturity, lower rates of anxiety, fewer psychopathic traits, less gang involvement and less self reported offending than mixed style offenders. Findings suggest that increasingly and exclusively solo offenders are not loners, as they are sometimes portrayed, and that exclusively solo offending during adolescence, while rare and previously misunderstood, may not be a risk factor in and of itself
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