scholarly journals Composition and Pressure Effects on Partitioning of Ferrous Iron in Iron-Rich Lower Mantle Heterogeneities

Minerals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 512
Author(s):  
Susannah M. Dorfman ◽  
Farhang Nabiei ◽  
Charles-Edouard Boukaré ◽  
Vitali B. Prakapenka ◽  
Marco Cantoni ◽  
...  
Keyword(s):  
Lower Mantle ◽  
Ferrous Iron ◽  
Shear Velocity ◽  
Pressure Effects ◽  
Sio2 Content ◽  
Ex Situ ◽  
Mantle Dynamics ◽  
Mantle Heterogeneities ◽  
Transmission Electron ◽  
Laser Heated

Both seismic observations of dense low shear velocity regions and models of magma ocean crystallization and mantle dynamics support enrichment of iron in Earth’s lowermost mantle. Physical properties of iron-rich lower mantle heterogeneities in the modern Earth depend on distribution of iron between coexisting lower mantle phases (Mg,Fe)O magnesiowüstite, (Mg,Fe)SiO3 bridgmanite, and (Mg,Fe)SiO3 post-perovskite. The partitioning of iron between these phases was investigated in synthetic ferrous-iron-rich olivine compositions (Mg0.55Fe0.45)2SiO4 and (Mg0.28Fe0.72)2SiO4 at lower mantle conditions ranging from 33–128 GPa and 1900–3000 K in the laser-heated diamond anvil cell. The resulting phase assemblages were characterized by a combination of in situ X-ray diffraction and ex situ transmission electron microscopy. The exchange coefficient between bridgmanite and magnesiowüstite decreases with pressure and bulk Fe# and increases with temperature. Thermodynamic modeling determines that incorporation and partitioning of iron in bridgmanite are explained well by excess volume associated with Mg-Fe exchange. Partitioning results are used to model compositions and densities of mantle phase assemblages as a function of pressure, FeO-content and SiO2-content. Unlike average mantle compositions, iron-rich compositions in the mantle exhibit negative dependence of density on SiO2-content at all mantle depths, an important finding for interpretation of deep lower mantle structures.

scholarly journals Velocity and density characteristics of subducted oceanic crust and the origin of lower-mantle heterogeneities

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Wenzhong Wang ◽  
Yinhan Xu ◽  
Daoyuan Sun ◽  
Sidao Ni ◽  
Renata Wentzcovitch ◽  
...  
Keyword(s):  
Phase Transition ◽  
Oceanic Crust ◽  
Seismic Tomography ◽  
Lower Mantle ◽  
Shear Velocity ◽  
Calcium Ferrite ◽  
Velocity Anomaly ◽  
Mantle Heterogeneities ◽  
Subducted Oceanic Crust ◽  
Low Shear

AbstractSeismic heterogeneities detected in the lower mantle were proposed to be related to subducted oceanic crust. However, the velocity and density of subducted oceanic crust at lower-mantle conditions remain unknown. Here, we report ab initio results for the elastic properties of calcium ferrite‐type phases and determine the velocities and density of oceanic crust along different mantle geotherms. We find that the subducted oceanic crust shows a large negative shear velocity anomaly at the phase boundary between stishovite and CaCl2-type silica, which is highly consistent with the feature of mid-mantle scatterers. After this phase transition in silica, subducted oceanic crust will be visible as high-velocity heterogeneities as imaged by seismic tomography. This study suggests that the presence of subducted oceanic crust could provide good explanations for some lower-mantle seismic heterogeneities with different length scales except large low shear velocity provinces (LLSVPs).

Transmission Electron Microscopy of Epitaxial silicides grown by ultra high vacuum deposition

1989 ◽  
Vol 47 ◽  
pp. 462-463
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
High Vacuum ◽  
High Energy ◽  
Energy Electron ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Transmission Electron

The silicides CoSi2 and NiSi2 are both metallic with the fee flourite structure and lattice constants which are close to silicon (1.2% and 0.6% smaller at room temperature respectively) Consequently epitaxial cobalt and nickel disilicide can be grown on silicon. If these layers are formed by ultra high vacuum (UHV) deposition (also known as molecular beam epitaxy or MBE) their thickness can be controlled to within a few monolayers. Such ultrathin metal/silicon systems have many potential applications: for example electronic devices based on ballistic transport. They also provide a model system to study the properties of heterointerfaces. In this work we will discuss results obtained using in situ and ex situ transmission electron microscopy (TEM).In situ TEM is suited to the study of MBE growth for several reasons. It offers high spatial resolution and the ability to penetrate many monolayers of material. This is in contrast to the techniques which are usually employed for in situ measurements in MBE, for example low energy electron diffraction (LEED) and reflection high energy electron diffraction (RHEED), which are both sensitive to only a few monolayers at the surface.

A New Method of Wafer Level Plan View TEM Sample Preparation by DualBeam

2008 ◽  
Author(s):  
Hyoung H. Kang ◽  
Michael A. Gribelyuk ◽  
Oliver D. Patterson ◽  
Steven B. Herschbein ◽  
Corey Senowitz
Keyword(s):  
Sample Preparation ◽  
Ex Situ ◽  
Wafer Level ◽  
Cross Sectional ◽  
Plan View ◽  
Manufacturing Line ◽  
Transmission Electron ◽  
Thin Lamella ◽  
Preparation Techniques

Abstract Cross-sectional style transmission electron microscopy (TEM) sample preparation techniques by DualBeam (SEM/FIB) systems are widely used in both laboratory and manufacturing lines with either in-situ or ex-situ lift out methods. By contrast, however, the plan view TEM sample has only been prepared in the laboratory environment, and only after breaking the wafer. This paper introduces a novel methodology for in-line, plan view TEM sample preparation at the 300mm wafer level that does not require breaking the wafer. It also presents the benefit of the technique on electrically short defects. The methodology of thin lamella TEM sample preparation for plan view work in two different tool configurations is also presented. The detailed procedure of thin lamella sample preparation is also described. In-line, full wafer plan view (S)TEM provides a quick turn around solution for defect analysis in the manufacturing line.

scholarly journals Dual Electrochemical Treatments to Improve Properties of Ti6Al4V Alloy

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2479
Author(s):  
Stefano Rossi ◽  
Luciana Volgare ◽  
Carine Perrin-Pellegrino ◽  
Carine Chassigneux ◽  
Erick Dousset ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Combined Treatment ◽  
Amorphous Film ◽  
Amorphous Layer ◽  
Good Alternative ◽  
Surface Treatments ◽  
Ex Situ ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Fluid Environment

Surface treatments are considered as a good alternative to increase biocompatibility and the lifetime of Ti-based alloys used for implants in the human body. The present research reports the comparison of bare and modified Ti6Al4V substrates on hydrophilicity and corrosion resistance properties in body fluid environment at 37 °C. Several surface treatments were conducted separately to obtain either a porous oxide layer using nanostructuration (N) in ethylene glycol containing fluoride solution, or bulk oxide thin films through heat treatment at 450 °C for 3 h (HT), or electrochemical oxidation at 1 V for 3 h (EO), as well as combined treatments (N-HT and N-EO). In-situ X-ray diffraction and ex-situ transmission electron microscopy have shown that heat treatment gave first rise to the formation of a 30 nm thick amorphous layer which crystallized in rutile around 620 °C. Electrochemical oxidations gave rise to a 10 nm thick amorphous film on the top of the surface (EO) or below the amorphous nanotube layer (N-EO). Dual treated samples presented similar results with a more stable behavior for N-EO. Finally, for both corrosion and hydrophilicity points of view, the new combined treatment to get a total amorphous N-EO sample seems to be the best and even better than the partially crystallized N-HT sample.

scholarly journals Feedbacks between a non-Newtonian upper mantle, mantle viscosity structure and mantle dynamics

2020 ◽  
Vol 224 (2) ◽  
pp. 961-972
Author(s):  
A G Semple ◽  
A Lenardic
Keyword(s):  
Upper Mantle ◽  
Lower Mantle ◽  
Mantle Convection ◽  
Mantle Flow ◽  
Mantle Dynamics ◽  
Plate Motions ◽  
Low Viscosity ◽  
Mantle Viscosity ◽  
Flow Feature ◽  
Mantle Rheology

SUMMARY Previous studies have shown that a low viscosity upper mantle can impact the wavelength of mantle flow and the balance of plate driving to resisting forces. Those studies assumed that mantle viscosity is independent of mantle flow. We explore the potential that mantle flow is not only influenced by viscosity but can also feedback and alter mantle viscosity structure owing to a non-Newtonian upper-mantle rheology. Our results indicate that the average viscosity of the upper mantle, and viscosity variations within it, are affected by the depth to which a non-Newtonian rheology holds. Changes in the wavelength of mantle flow, that occur when upper-mantle viscosity drops below a critical value, alter flow velocities which, in turn, alter mantle viscosity. Those changes also affect flow profiles in the mantle and the degree to which mantle flow drives the motion of a plate analogue above it. Enhanced upper-mantle flow, due to an increasing degree of non-Newtonian behaviour, decreases the ratio of upper- to lower-mantle viscosity. Whole layer mantle convection is maintained but upper- and lower-mantle flow take on different dynamic forms: fast and concentrated upper-mantle flow; slow and diffuse lower-mantle flow. Collectively, mantle viscosity, mantle flow wavelengths, upper- to lower-mantle velocities and the degree to which the mantle can drive plate motions become connected to one another through coupled feedback loops. Under this view of mantle dynamics, depth-variable mantle viscosity is an emergent flow feature that both affects and is affected by the configuration of mantle and plate flow.

A Comparison of in- and ex-situ Shear Bands in Metallic Glass by Transmission Electron Microsopy

2021 ◽  
Author(s):  
Harald Rösner ◽  
Christian Kübel ◽  
Stefan Ostendorp ◽  
Gerhard Wilde
Keyword(s):  
Metallic Glass ◽  
Shear Bands ◽  
Ex Situ ◽  
Transmission Electron

Initial Dynamic Susceptibility of Maghemite Nanoparticles Dispersed in Surface-Treated Polymeric Template

2021 ◽  
Vol 21 (11) ◽  
pp. 5694-5697
Author(s):  
A. F. R. Rodriguez ◽  
R. F. Lacerda ◽  
L. E. Maggi ◽  
Hory Mohammadpour ◽  
Mohammad Niyaifar ◽  
...  
Keyword(s):  
Ex Situ ◽  
Transmission Electron Microscopy Data ◽  
Dynamic Susceptibility ◽  
Maghemite Nanoparticles ◽  
X Ray Diffraction ◽  
Chemical Treatments ◽  
Dynamical Susceptibility ◽  
Transmission Electron ◽  
Microscopy Data ◽  
Polymeric Template

Magnetic nanocomposites based on maghemite nanoparticles supported (ex situ route) on styrene- divinilbenzene (Sty-DVB) copolymer templates were produced and characterized for their structure and morphology. The as-produced nanocomposites were further chemically-treated with different oxidant agents and surface-coated with stearic acid. X-ray diffraction and transmission electron microscopy data show that the incorporated nanoparticles are preserved despite the aggressive chemical treatments employed. From the dynamical susceptibility measurements performed on the nanocomposites, the values of the saturation magnetization (76 emu/g) and the effective magnetic anisotropy (1.7 × 104 J/m3) were obtained, in excellent agreement with the values reported in the literature for maghemite. This finding strongly supports the preservation of the magnetic properties of the supported nanosized maghemite throughout the entire samples’ processing.

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