scholarly journals Microstructural evolution in the fine-grained region of the Siple Dome (Antarctica) ice core

2011 ◽  
Vol 57 (206) ◽  
pp. 1046-1056 ◽  
Author(s):  
R.W. Obbard ◽  
K.E. Sieg ◽  
I. Baker ◽  
D. Meese ◽  
G.A. Catania
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Electron Backscatter Diffraction ◽  
Ice Core ◽  
Axis Orientation ◽  
Fine Grained ◽  
Depth Analysis ◽  
Siple Dome ◽  
Mean Grain Size

AbstractAn in-depth analysis of seven samples from the Siple Dome (Antarctica) ice core, using optical microscopy and electron backscatter diffraction, illustrates rotational recrystallization or polygonization in the fine-grained region of the core between 700 and 800 m. Between 640 and 700 m, the microstructure is characterized by a bimodal grain-size distribution and a broken girdle fabric with evidence of polygonization. From 727 to 770 m, mean grain size decreases and a single-maximum fabric is found, and, by 790 m, mean grain size has again increased and a multiple-maxima fabric manifests itself. We compare grain-size distribution, c- and a-axis orientation, and misorientation between adjacent grains. We found that misorientations between adjacent grains in the 727–770 m region were predominantly low-angle and typically around a common a-axis, suggesting polygonization. This conclusion is supported by radar evidence of a physical disturbance at 757 m, which may be correlated with higher than usual strain in the 700–800 m range. Below 770 m, larger less regular misorientations and textural evidence show that migration recrystallization is the primary recrystallization mechanism.

scholarly journals MINERAL COMPOSITION OF SOME LATGALE LAKE SEDIMENTS

2019 ◽  
Vol 1 ◽  
pp. 304
Author(s):  
Rasma Tretjakova ◽  
Andris Karpovičs
Keyword(s):  
Grain Size ◽  
Lake Sediments ◽  
Size Distribution ◽  
Clay Minerals ◽  
Mineral Composition ◽  
Grain Size Distribution ◽  
Sandy Loam ◽  
Clay Fraction ◽  
Fine Grained ◽  
Two Samples

Our research is focused on sedimentological conditions and postdepositional changes of recent fine grained lake sediments. We used bulk sediment mineralogical composition and grain size distribution as indicators to identify sediment source areas and possible changes during Holocene. We analysed fine grained (clayey) sediments from three Latgale lakes - Zeili, Pauguļi and Plusons, situated in Latgale upland. Lake sediments cover Late Pleistocene glacial deposits – loam and sandy loam. Bulk mineral composition of 6 sediment samples was determined by X-ray diffraction (XRD). Sediments contained typical minerals found in surrounding glacial sediments: rock-forming minerals as quartz, plagioclase, albite, enstatite, dolomite, calcite, and clay minerals - illite, kaolinite. To identify postdepositional changes in lake sediments of Holocene age clay minerals in clay fraction (<2 mkm) should be analysed. Particularly illite, smectite mixed layered minerals - illite/smectite (I/Sm) and chlorite. Additionally, grain size distribution of studied lake sediments was analysed. Accordingly, our studied sediments are clays, silty clays and clayey silts with bimodal particle distribution, except two samples from Zeiļi and Plusons with unimodal distribution.

scholarly journals Assessment and Analysis of Precambrian Basement Soil Deposits Using Grain Size Distribution

2020 ◽  
Vol 66 (4) ◽  
pp. 235-243
Author(s):  
Gideon Layade ◽  
Charles Ogunkoya ◽  
Victor Makinde ◽  
Kehinde Ajayi
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Textural Properties ◽  
Soil Samples ◽  
Sieve Analysis ◽  
Precambrian Basement ◽  
Statistical Parameters ◽  
Fine Grained ◽  
Transportation History

AbstractThe article presents the grain size distribution of soil samples from the Precambrian basement within the purview of the textural properties, deduced transportation history and the numerical assessments using statistical parameters. The fourteen soil samples collected from the study area were subjected to sieve analysis in the laboratory for the determination of their grain size distribution. The statistical parameters’ study includes the graphic mean, skewness, sorting and kurtosis. The result of the analysis of the soil samples ranged from coarse to fine-grained samples, moderately and poorly sorted, positively and negatively skewed and the kurtosis also shows leptokurtic as the most dominant which suggests the samples poorly distributed and moderately sorted at the centre of the grain size distribution. These results also suggest the geological environment of the soil samples could be responsible for the poorly and moderately sorted exhibited by the samples deposited in the location.

Changes in Grain Size Distribution of a Submicron Grained Al-Sc Alloy during High Temperature Annealing

2006 ◽  
Vol 519-521 ◽  
pp. 1617-1622 ◽  
Author(s):  
N. Burhan ◽  
Michael Ferry
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Elevated Temperatures ◽  
Large Fraction ◽  
Direct Consequence ◽  
Size Distributions ◽  
Grain Coarsening ◽  
Fine Grained ◽  
Grain Size Distributions

Severe plastic straining is an established method for producing submicron grain (SMG) structures in alloys. However, the development of such a fine grained structure in single-phase alloys is usually futile if they are to be exposed or processed at elevated temperatures. This is a direct consequence of the natural tendency for rapid and substantial grain coarsening which completely removes the benefits obtained by grain refinement. This problem may be avoided by the introduction of nanosized, highly stable particles in the metal matrix. In this work, a SMG structure was generated in an Al-0.3 wt.% Sc alloy by Equal Channel Angular Pressing (ECAP). The alloy was prepared initially to produce a fine grained microstructure exhibiting a large fraction of high angle grain boundaries and a dispersion of nanosized Al3Sc particles. The evolution of microstructure during annealing at temperatures up to 550 °C was examined in detail and grain size distributions generated from the data. It was shown that grain coarsening is rapid at temperatures above 450 °C and the initial log-normal grain size distribution exhibiting low variance and skewness was altered considerably. The statistical information generated from the grain size distributions confirms that discontinuous grain coarsening occurs in this alloy only at temperatures greater than 500 °C.

Mineralogical and textural discrimination of loess derived from a tephra near Rotorua, New Zealand

Soil Research ◽  
1988 ◽  
Vol 26 (2) ◽  
pp. 301 ◽  
Author(s):  
LA Benny ◽  
NM Kennedy ◽  
JH Kirkman ◽  
RB Stewart
Keyword(s):  
Grain Size ◽  
New Zealand ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Field Observations ◽  
Mean Grain Size ◽  
Mean Size ◽  
The Mean ◽  
Grain Size Parameters

Grain size parameters and clay mineralogical analyses were used to characterize and compare Okareka Ash and post-Okareka tephric loess sampled at eight sites on a transect in Rotorua district, North Island, New Zealand. Grain size distribution analyses show consistently lower mean size and better sorting of the tephric loess compared with the Okareka Ash. The mean grain size of the loess is strongly influenced by the mean grain size of the tephra. Trends in the distribution of biotite and halloysite support the grain size distribution analyses. Taken with field observations, the analytical evidence allows differentiation between Okareka Ash and overlying associated tephric loess.

A new easy-to-use tool for grain size distribution analysis

2020 ◽  
Author(s):  
Yuming Liu ◽  
Xingxing Liu ◽  
Youbin Sun
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Quaternary Geology ◽  
Distribution Analysis ◽  
Lacustrine Deposits ◽  
Mean Grain Size ◽  
Different Types ◽  
Geological Information ◽  
End Members

&lt;p&gt;Grain size distribution (GSD) data have been widely used in Earth sciences, especially Quaternary Geology, due to its convenience and reliability. However, the usages of GSD are still oversimplified. The geological information contained in GSD is very abundant, but only some simplified proxies (e.g. mean grain size) are widely used. The most important reason is that GSD data are hard to interpret and visualize directly.&lt;/p&gt;&lt;p&gt;To overcome this, some researchers have developed the methods to unmix the mixed multi-modal GSD to some components to make the interpretation and visualization easier. These methods can be divided into two routes. One is end-member analysis (EMA) which takes a batch of samples for the calculation of the end-members. Another is called single-specimen unmixing (SSU) (Sun et al., 2002) which treats each sample as an individual. The key difference between the two routes is that whether the end-members of a batch of samples are consistent. EMA believes that the end-members between different samples are consistent, the variations of GSD are only caused by the changing of fractions of the end-members. On the contrary, SSU has no assumption on the end-members, i.e. it admits that the end-members may vary between different samples. Some mature tools (Paterson and Heslop, 2015; Dietze and Dietze, 2019) taking the EMA route have appeared, but there is no available public and easy-to-use tool for SSU.&lt;/p&gt;&lt;p&gt;Here we introduce a free and open-source GUI tool which is called QGrain, it can help researchers to analyze the GSD data easily and bring new insights for the interpretation of GSD. QGrain is based on SSU but applied some algorithms (e.g. data preprocessing and global optimization) to improve its precision and robustness. It supports Lognormal or Weibull as the base distribution and it is easy to add more base distributions. QGrain can handle different types of sediments (e.g. aeolian, fluvial and lacustrine deposits). QGrain can export all detailed data and generate the charts automatically.&lt;/p&gt;

Ordering and Grain Growth Kinetics in CoPt Thin Films

1995 ◽  
Vol 398 ◽  
Author(s):  
R. A. Ristau ◽  
K. Barmak ◽  
D. W. Hess ◽  
K. R. Coffey ◽  
M. A. Parker ◽  
...  
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Growth ◽  
Grain Size Distribution ◽  
Volume Fraction ◽  
Domain Size ◽  
Face Centered Cubic ◽  
Temperature Range ◽  
Mean Grain Size ◽  
The Mean

ABSTRACTOrdering and grain growth have been studied in a 10 nm thick CoPt alloy film of equiatomic composition annealed in the temperature range 550–700°C by quantifying ordered domain size, volume fraction ordered, grain size, and grain size distribution. Ordering occurs by nucleation and growth of Ll0 ordered domains, with a mean size of 3 nm at 550°C and 19 nm at 700°C. The volume percent ordered shows a dramatic increase from <y1% to approximately 28% between the two extremes of annealing temperature. The mean grain size of the as-deposited films is 5 nm and the entire film is face-centered cubic. Upon annealing in the temperature range 550–600°C, the mean grain size reaches a stagnation limit of 27 nm and the grain size distribution is log-normal. Grain growth resumes beyond 600°C and the mean grain size reaches as high as 55 nm at 700°C. The increase in the coercivity of the annealed films follows the increase in the ordered fraction more closely than the increase in grain size. The shape of the M-H loop shows evidence of coupling between the magnetically hard (ordered) and soft (disordered) regions.

scholarly journals Influence of Grain Size Distribution on Estimation of Mean Grain Size

1988 ◽  
Vol 52 (9) ◽  
pp. 835-842 ◽  
Author(s):  
Yoshimasa Takayama ◽  
Tatsumi Tozawa ◽  
Hajime Kato ◽  
Norio Furushiro ◽  
Shigenori Hori
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Mean Grain Size
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