A Novel Cell for Studying Ionic Transport in Powders During Compaction and Its Application to Lithium Silicate Glass Powder

2015 ◽  
Vol 229 (9) ◽  
Author(s):  
Dawid Murawski ◽  
Sebastian Roß ◽  
Harald Behrens

AbstractA new cell was developed to study the behavior of powders during axial compaction at temperatures up to 950 K and pressures up to 1 GPa. Electrical conductivity of the sample is measured by impedance spectroscopy. Change of sample volume can be simultaneously monitored using linear variable differential transducers. Flushing with gases allows pre-conditioning of material surfaces before compaction. The cell was tested with two different grain size fractions (60–150 μm and 200–250 μm) of lithium trisilicate glass in the brittle deformation range (315 K) and in the partially plastic deformation range (ca. 660 K). The DC conductivity increases linearly with pressure up to 750 MPa at about 660 K. Lower conductivity for the smaller grain size fraction under these conditions is attributed to higher shares of pores between the grains, acting as resistors.

2021 ◽  
Author(s):  
Julian Hülscher ◽  
Edward R. Sobel ◽  
Niklas Kallnik ◽  
J. Elis Hoffmann ◽  
Ian L. Millar ◽  
...  

<p>Sedimentary archives are the main source of information for climatic and tectonic changes in Earth’s history. We investigate how the tectonically triggered early (28±1 Ma) exhumation of the Tauern Window in the Eastern European Alps is recorded in the Oligocene/Miocene Northern Alpine Foreland Basin (NAFB) in Upper Austria. We combined Nd isotopic compositions on clay-sized bulk sediment and of sand-sized single-grain apatites with additional trace-element geochemistry, fission track (AFT) and U-Pb dating to investigate the timing of when this tectonic signal reaches the sediment archive within these different grain-size fractions.</p><p>This well-investigated basin offers an excellent opportunity to investigate environmental signal propagation. From ~27 to 19 Ma, a deep-marine basin-axial, gravity-flow dominated channel controlled the West to East directed sediment transport in the Upper Austrian NAFB. The sediments were sourced in the Eastern and Central Alps. At 19 Ma, channel sedimentation ceased and clinoforms prograded from the southern margin northward into the basin. This change in sediment-routing direction cut off the Central Alpine sediment source.</p><p>Drill cuttings of one well on the northern basin slope and drill cores from 12 wells were sampled for clay and the single-grain analysis. Clay eNd values remain stable around -9.7 (±0.5) from 27 to 19 Ma but increase afterwards to -8.7 (±0.2) at 18.3 Ma. In contrast, apatite single-grain results significantly change at 23.3±0.3 Ma from a domination of apatites from low-grade (<upper amphibolite-facies) metamorphic sources, Permo-Mesozoic and late Variscan U-Pb ages and AFT ages >40 Ma to a domination of high-grade metamorphic apatites with late Variscan U-Pb ages and an increasing number of AFT ages <30 Ma. The high-grade metamorphic apatites have slightly more positive eNd values (-2.2 ± 3.9) than the low-grade metamorphic apatites (-4.4 ± 4.2).</p><p>The changes in the single-grain data sets have been previously interpreted to mirror the exposure of a new Upper Austroalpine nappe as a consequence of the ongoing early Tauern Window exhumation. The total signal lag time between the beginning of the exhumation and the arrival of the signal within the apatite assemblage in the sedimentary archive is therefore 3.4 to 6 Myrs. The clay eNd values do not record this change in provenance at 23.3±0.3 Ma as they stayed stable until 19 Ma when they increased slightly. This might point towards a delayed recording of the provenance change revealed at 23.3±0.3 Ma by the apatites. The difference in signal recording is caused by the characteristics of the applied methods. Whereas single-grain distributions of orogen-wide sediment-routing systems can be dominated by geographically small areas with high erosion rates and high mineral fertility, bulk-rock methods integrate over the entire drainage area, a process that diminishes extreme values. The disconnection of the Central Alpine sediment source at 19 Ma, increased the relative proportion of the more positive eNd values of the Upper Austroalpine Nappe in the drainage area, leading to an increase in clay eNd values in our data set. Our results show that different information from the hinterland is recorded in the different grain-size fractions and methods.</p>


2007 ◽  
Vol 36 (4) ◽  
Author(s):  
Barbara Radke ◽  
Grażyna Dembska ◽  
Barbara Aftanas ◽  
Aneta Kowalczyk ◽  
Jerzy Bolałek

Spatial distribution of labile and total forms of copper and zinc in sediments from the Port of GdanskSediment cores were collected from a number of sites in the Port of Gdansk in 1997 and 1998. The samples were segregated by depth then dried, homogenised and sieved into four grain size fractions (>2.00 mm, 2.00 - 0.063 mm, 0.063 - 0.032 mm, and 0.032 mm) Small-grained sand with a low admixture of silt predominated in all samples, whilst the amount of organic matter and water varied between samples. The 2.00 - 0.063 mm size fraction was the most abundant; and also showed the highest accumulation of trace metals. In the >2.00 mm size fraction the mean concentration of labile forms of copper was 9.06 mg kg


2020 ◽  
Author(s):  
Zhongyuan Wang ◽  
Yongqiu Wu

<p>Desert (sandland) margin is the transition region from inner aeolian landforms  to other landforms outside, while it remains as an ambiguous conception in previous researches. Accurately delineating its boundary line and realizing the characteristics of the particle size distribution of surface aeolian sands in margin area can help us understand the formation of modern boundary of desert (sandland). In this research, the criteria of identification of the boundary were proposed and the boundary line was extracted quantitative. Then systematic analyses of grain size of aeolian sand in margin were conducted. Together with the morphologic type, activity and the geomorphological location of collected dunes, the factors controlled the particle-size distributions had also been analyzed. The results reveal the following: (1) There is notable difference in grain size characteristics of aeolian sand between inside and outside of Mu Us sandland. The outside samples are finer than inside. Additionally, the aeolian sand covering on loess is always more poorly sorted and with different grain size fraction composition. (2) The controlling factors on particle size distribution are different in different downwind margins. In southwest margin, the grain size characteristics of aeolian sand are influenced by time and degree of stabilization of sampled dune and locally topographic relief; From the estuary of Lu River to Yuxi River, sediment transport by wind is affected by topographic obstacles including both valley and loess gully. Meanwhile, the small dunefields in Loess Plateau outside of Mu Us sandland may originate from a local alluvial source; In northeast downwind margin, the grain size characteristics of aeolian sand covering on loess are determined by regional gully erosion after its deposition.</p>


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