scholarly journals X-ray nanotomography and electron backscatter diffraction demonstrate the crystalline, heterogeneous and impermeable nature of conodont white matter

2021 ◽  
Vol 8 (8) ◽  
pp. 202013
Author(s):  
Ayse Atakul-Özdemir ◽  
Xander Warren ◽  
Peter G. Martin ◽  
Manuel Guizar-Sicairos ◽  
Mirko Holler ◽  
...  
Keyword(s):  
White Matter ◽  
Electron Backscatter Diffraction ◽  
Pore Network ◽  
Electron Back Scatter Diffraction ◽  
X Ray ◽  
Network Analyses ◽  
Historical Archive ◽  
X Ray Computed ◽  
Ocean Chemistry ◽  
Backscatter Diffraction

Conodont elements, microfossil remains of extinct primitive vertebrates, are commonly exploited as mineral archives of ocean chemistry, yielding fundamental insights into the palaeotemperature and chemical composition of past oceans. Geochemical assays have been traditionally focused on the so-called lamellar and white matter crown tissues; however, the porosity and crystallographic nature of the white matter and its inferred permeability are disputed, raising concerns over its suitability as a geochemical archive. Here, we constrain the characteristics of this tissue and address conflicting interpretations using ptychographic X-ray-computed tomography (PXCT), pore network analysis, synchrotron radiation X-ray tomographic microscopy (srXTM) and electron back-scatter diffraction (EBSD). PXCT and pore network analyses based on these data reveal that while white matter is extremely porous, the pores are unconnected, rendering this tissue closed to postmortem fluid percolation. EBSD analyses demonstrate that white matter is crystalline and comprised of a single crystal typically tens of micrometres in dimensions. Combined with evidence that conodont elements grow episodically, these data suggest that white matter, which comprises the denticles of conodont elements, grows syntactically, indicating that individual crystals are time heterogeneous. Together these data provide support for the interpretation of conodont white matter as a closed geochemical system and, therefore, its utility of the conodont fossil record as a historical archive of Palaeozoic and Early Mesozoic ocean chemistry.

scholarly journals Stable and Metastable Phase Equilibria Involving the Cu6Sn5 Intermetallic

2021 ◽  
Author(s):  
A. Leineweber ◽  
M. Löffler ◽  
S. Martin
Keyword(s):  
Phase Equilibria ◽  
Electron Backscatter Diffraction ◽  
Metastable Phase ◽  
Stable Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Heat Treated ◽  
Ordered Phases ◽  
Backscatter Diffraction ◽  
Kinetics Of

Abstract Cu6Sn5 intermetallic occurs in the form of differently ordered phases η, η′ and η′′. In solder joints, this intermetallic can undergo changes in composition and the state of order without or while interacting with excess Cu and excess Sn in the system, potentially giving rise to detrimental changes in the mechanical properties of the solder. In order to study such processes in fundamental detail and to get more detailed information about the metastable and stable phase equilibria, model alloys consisting of Cu3Sn + Cu6Sn5 as well as Cu6Sn5 + Sn-rich melt were heat treated. Powder x-ray diffraction and scanning electron microscopy supplemented by electron backscatter diffraction were used to investigate the structural and microstructural changes. It was shown that Sn-poor η can increase its Sn content by Cu3Sn precipitation at grain boundaries or by uptake of Sn from the Sn-rich melt. From the kinetics of the former process at 513 K and the grain size of the η phase, we obtained an interdiffusion coefficient in η of (3 ± 1) × 10−16 m2 s−1. Comparison of this value with literature data implies that this value reflects pure volume (inter)diffusion, while Cu6Sn5 growth at low temperature is typically strongly influenced by grain-boundary diffusion. These investigations also confirm that η′′ forming below a composition-dependent transus temperature gradually enriches in Sn content, confirming that Sn-poor η′′ is metastable against decomposition into Cu3Sn and more Sn-rich η or (at lower temperatures) η′. Graphic Abstract

Mitrofanovite, Pt3Te4, a new mineral from the East Chuarvy deposit, Fedorovo–Pana intrusion, Kola Peninsula, Russia

2018 ◽  
Vol 83 (4) ◽  
pp. 523-530 ◽  
Author(s):  
Victor V. Subbotin ◽  
Anna Vymazalová ◽  
František Laufek ◽  
Yevgeny E. Savchenko ◽  
Chris J. Stanley ◽  
...  
Keyword(s):  
Kola Peninsula ◽  
Electron Backscatter Diffraction ◽  
New Mineral ◽  
Synthetic Analogue ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structural Identity ◽  
Polarised Light ◽  
Fe Alloys ◽  
Backscatter Diffraction

AbstractMitrofanovite, Pt3Te4, is a new telluride discovered in low-sulfide disseminated ore in the East Chuarvy deposit, Fedorovo–Pana intrusion, Kola Peninsula, Russia. It forms anhedral grains (up to ~20 μm × 50 μm) commonly in intergrowths with moncheite in aggregates with lukkulaisvaaraite, kotulskite, vysotskite, braggite, keithconnite, rustenburgite and Pt–Fe alloys hosted by a chalcopyrite–pentlandite–pyrrhotite matrix. Associated silicates are: orthopyroxene, augite, olivine, amphiboles and plagioclase. Mitrofanovite is brittle; it has a metallic lustre and a grey streak. Mitrofanovite has a good cleavage, along {001}. In plane-polarised light, mitrofanovite is bright white with medium to strong bireflectance, slight pleochroism, and strong anisotropy on non-basal sections with greyish brown rotation tints; it exhibits no internal reflections. Reflectance values for the synthetic analogue of mitrofanovite in air (Ro, Re’ in %) are: 58.4, 54.6 at 470 nm; 62.7, 58.0 at 546 nm; 63.4, 59.1 at 589 nm; and 63.6, 59.5 at 650 nm. Fifteen electron-microprobe analyses of mitrofanovite gave an average composition: Pt 52.08, Pd 0.19, Te 47.08 and Bi 0.91, total 100.27 wt.%, corresponding to the formula (Pt2.91Pd0.02)Σ2.93(Te4.02Bi0.05)Σ4.07 based on 7 atoms; the average of eleven analyses on synthetic analogue is: Pt 52.57 and Te 47.45, total 100.02 wt.%, corresponding to Pt2.94Te4.06. The density, calculated on the basis of the formula, is 11.18 g/cm3. The mineral is trigonal, space group R$\overline 3 $m, with a = 3.9874(1), c = 35.361(1) Å, V = 486.91(2) Å3 and Z = 3. The crystal structure was solved and refined from the powder X-ray-diffraction data of synthetic Pt3Te4. Mitrofanovite is structurally and chemically related to moncheite (PtTe2). The strongest lines in the powder X-ray diffraction pattern of synthetic mitrofanovite [d in Å (I) (hkl)] are: 11.790(23)(003), 5.891(100)(006), 2.851(26)(107), 2.137(16)(1013), 2.039(18)(0114), 1.574(24)(0120), 1.3098(21)(0027). The structural identity of natural mitrofanovite with synthetic Pt3Te4 was confirmed by electron backscatter diffraction measurements on the natural sample. The mineral name is chosen to honour Felix P. Mitrofanov, a Russian geologist who was among the first to discover platinum-group element mineralisation in the Fedorova–Pana complex.

scholarly journals Initiation and short crack growth behaviour of environmentally induced cracks in AA5083 H131 investigated across time and length scales

2019 ◽  
Vol 37 (5) ◽  
pp. 469-481 ◽  
Author(s):  
Visweswara C. Gudla ◽  
Alistair Garner ◽  
Malte Storm ◽  
Parmesh Gajjar ◽  
James Carr ◽  
...  
Keyword(s):  
Electron Backscatter Diffraction ◽  
Three Dimensional ◽  
High Strength ◽  
Time Lapse ◽  
Growth Behaviour ◽  
Spectroscopy Analysis ◽  
Crack Growth Behaviour ◽  
Rate Testing ◽  
X Ray Computed ◽  
Backscatter Diffraction

AbstractEnvironmentally induced cracking (EIC) in a sensitized high-strength AA5083 H131 alloy has been investigated using time-lapse synchrotron X-ray computed tomography combined with post-mortem correlative characterization. Small corrosion features deliberately introduced in a pre-exposure step were found to be the site of initiation for over 95% of the 44 EIC cracks that developed under slow strain rate testing. Detailed analysis using three-dimensional electron backscatter diffraction and energy-dispersive spectroscopy analysis of a single crack confirmed the intergranular nature of the cracks from the start and that the pre-exposure corrosion was associated with an α-AlFeMnSi particle cluster. It also appears that several cracks may have initiated at this site, which later coalesced to form the 300-μm-long crack that ultimately developed. Of further note is the fact that initiation of the EIC cracks across the sample started below the yield strength and continued beyond the ultimate tensile strength. The most rapid crack propagation occurred during sample extension following a period of fixed displacement.

scholarly journals Diffracting-grain identification from electron backscatter diffraction maps during residual stress measurements: a comparison between the sin2ψ and cosα methods

2019 ◽  
Vol 52 (4) ◽  
pp. 828-843 ◽  
Author(s):  
Dorian Delbergue ◽  
Damien Texier ◽  
Martin Lévesque ◽  
Philippe Bocher
Keyword(s):  
Residual Stress ◽  
Grain Size ◽  
Tilt Angle ◽  
Measurement Errors ◽  
Electron Backscatter Diffraction ◽  
Measurement Techniques ◽  
Single Exposure ◽  
X Ray ◽  
Electron Backscatter ◽  
Backscatter Diffraction

X-ray diffraction (XRD) is a widely used technique to evaluate residual stresses in crystalline materials. Several XRD measurement methods are available. (i) The sin2ψ method, a multiple-exposure technique, uses linear detectors to capture intercepts of the Debye–Scherrer rings, losing the major portion of the diffracting signal. (ii) The cosα method, thanks to the development of compact 2D detectors allowing the entire Debye–Scherrer ring to be captured in a single exposure, is an alternative method for residual stress measurement. The present article compares the two calculation methods in a new manner, by looking at the possible measurement errors related to each method. To this end, sets of grains in diffraction condition were first identified from electron backscatter diffraction (EBSD) mapping of Inconel 718 samples for each XRD calculation method and its associated detector, as each method provides different sets owing to the detector geometry or to the method specificities (such as tilt-angle number or Debye–Scherrer ring division). The X-ray elastic constant (XEC) ½S 2, calculated from EBSD maps for the {311} lattice planes, was determined and compared for the different sets of diffracting grains. It was observed that the 2D detector captures 1.5 times more grains in a single exposure (one tilt angle) than the linear detectors for nine tilt angles. Different XEC mean values were found for the sets of grains from the two XRD techniques/detectors. Grain-size effects were simulated, as well as detector oscillations to overcome them. A bimodal grain-size distribution effect and `artificial' textures introduced by XRD measurement techniques are also discussed.

Comparison of Workability of ZK60A Alloy Depending on Casting Methods

2012 ◽  
Vol 630 ◽  
pp. 35-40
Author(s):  
K.H. Jung ◽  
B. Ahn ◽  
S. Lee ◽  
D.S. Choi ◽  
Y.S. Lee ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Continuous Casting ◽  
Elevated Temperatures ◽  
Electron Backscatter Diffraction ◽  
Die Casting ◽  
Inspection System ◽  
Compression Tests ◽  
X Ray ◽  
Electron Backscatter ◽  
Backscatter Diffraction

In this research, the effect of casting methods on the workability of magnesium alloy ZK60A was investigated by comparing two different billets, fabricated by semi-continuous casting and die casting. To determine the workability of the materials, uniaxial compression tests were conducted at different elevated temperatures and strain rate of 0.01/s. In addition, the X-ray inspection system and electron backscatter diffraction (EBSD) were employed to compare their internal defects and microstructures, respectively. The workability of ZK60A depending on the casting methods is discussed based on the obtained experimental results.

White matter imaging of ethanol-fixed rat brain by phase-contrast X-ray computed tomography

2021 ◽  
pp. 028418512110307
Author(s):  
Thet-Thet- Lwin ◽  
Akio Yoneyama ◽  
Shogo Kokubo ◽  
Hiroko Maruyama ◽  
Kazuyuki Hyodo ◽  
...  
Keyword(s):  
White Matter ◽  
Phase Contrast ◽  
Three Dimensional ◽  
Image Contrast ◽  
Cerebral White Matter ◽  
Tissue Fixation ◽  
X Ray ◽  
Density Values ◽  
X Ray Computed ◽  
Formalin Fixed

Background Phase-contrast X-ray computed tomography imaging (PCI) based on crystal X-ray interferometry can detect minute density differences within biological soft tissues without contrast agents. Ethanol fixation yields increased tissue-background density differences due to the dehydrating and delipidifying effects of ethanol. Purpose To obtain high image contrast of cerebral white matter structures in PCI, tissue fixation using ethanol and routinely used formalin have been examined. Material and Methods Ethanol-fixed (EF) (n = 4) and formalin-fixed (FF) (n = 4) rat brains were imaged by crystal X-ray interferometry-based PCI. Tissue staining/microscopy was also performed for histological comparison and myelin density evaluation. Three-dimensional white matter tract images were reconstructed. Results Superior image contrast was obtained in the images of EF brains (EF images) compared to those of formalin-fixed brains (FF images), particularly for white matter structures. Significant density differences between the white matter structures and hippocampus ( P < 0.01)/thalamus ( P < 0.001) were observed in the EF, but not FF, images. Ethanol fixation enhanced the image contrast of white matter tracts by approximately sixfold compared to formalin fixation, and close agreement (r2 = 0.97; P < 0.05) between the density values on the CT images and the myelin density values in histological images was observed for the EF brains. Three-dimensional reconstruction of the white matter tracts was possible from the EF images, but not FF images. Conclusion Ethanol fixation resulted in marked contrast enhancement of cerebral white matter structures in PCI. Thus, high-resolution PCI using ethanol for tissue fixation could be valuable for experimental neurological studies and postmortem neuropathology evaluation.

scholarly journals Effects of Annealing Temperature on Recrystallization Texture and Microstructure Uniformity of High Purity Tantalum

Metals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 75 ◽  
Author(s):  
Jialin Zhu ◽  
Chao Deng ◽  
Yahui Liu ◽  
Nan Lin ◽  
Shifeng Liu
Keyword(s):  
Low Temperature ◽  
Electron Backscatter Diffraction ◽  
Stored Energy ◽  
X Ray Diffraction ◽  
Center Layer ◽  
X Ray ◽  
Texture Intensity ◽  
Low Temperature Annealing ◽  
Transmission Electron ◽  
Backscatter Diffraction

One hundred and thirty-five degree clock rolling significantly improves the texture homogeneity of tantalum sheets along the thickness, but a distinctly fragmented substructure is formed within {111} (<111>//normal direction (ND)) and {100} (<100>//ND) deformation grains, which is not suitable to obtain a uniform recrystallization microstructure. Thus, effects of different annealing temperatures on the microstructure and texture heterogeneity of tantalum sheets along the thickness were investigated by X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Results show that the texture distribution along θ-fiber and γ-fiber is irregular and many large grains with {111} orientation develop during annealing at high temperature. However, low-temperature annealing can not only weaken the texture intensity in the surface and the center layer but also introduce a more uniform grain size distribution. This result can be attributed to the subgrain-nucleation-dominated recrystallization mechanism induced by recovery at low temperature, and moreover, a considerable decline of recrystallization driving force resulting from the release of stored energy in the deformation matrix.

Sign in / Sign up

Export Citation Format

Share Document