scholarly journals Ex-situ and In-situ Microstructure Investigations of AM Part and Powders

2021 ◽  
Author(s):  
M. Albu ◽  
S. Mitsche ◽  
M. Nachtnebel ◽  
R. Krisper ◽  
M. Dienstleder ◽  
...  
Keyword(s):  
Microstructural Analysis ◽  
Atomic Resolution ◽  
Ex Situ ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Eutectic Si ◽  
Coarse Microstructure ◽  
Amorphous Si ◽  
Scanning Electron

This paper presents an advanced microstructural analysis of the AlSiMg, Ti64 and N700 powders used for additive manufacturing. The internal microstructure of the regular and irregular powder grains were characterized down to atomic resolution by using scanning electron microscopy and high resolution scanning transmission electron microscopy.The accretionary forms on top of the irregular AlSiMg powder grains exhibit a slightly coarse microstructure with a network of eutectic Si consisting of nano-crystallites, suggestinga slower cooling than the grain itself that contain a predominately amorphous Si network. A nm thin amorphous C layer on the surface of some Ti64 plasma atomized powder grains promoted the attachment of satellites and growth of envelopes. In case of gas atomized N700 powder grains, we identified thin oxide and carbon amorphous layers as well as metal segregations at the interface between the grain body and the accretionary forms.

Atomic-resolution Studies of Ca3Co4O9 using in-situ Scanning Transmission Electron Microscopy

2008 ◽  
Vol 14 (S2) ◽  
pp. 436-437 ◽  
Author(s):  
G Yang ◽  
Y Zhao ◽  
K Sader ◽  
A Bleloch ◽  
RF Klie
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
New Mexico ◽  
Scanning Transmission Electron Microscopy ◽  
Atomic Resolution ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

High-resolution backscattered electron images in the scanning electron microscope

1992 ◽  
Vol 50 (2) ◽  
pp. 1608-1609
Author(s):  
Oliver C. Wells ◽  
P.C. Cheng
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Scanning Electron Microscope ◽  
Transmission Electron Microscope ◽  
Scanning Transmission Electron Microscope ◽  
Atomic Resolution ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Backscattered Electron ◽  
Scanning Electron

In this discussion the words “high resolution imaging” of a solid sample in the scanning electron microscope (SEM) mean that details can be resolved that are considerably smaller than the penetration depth of the incident electron beam (EB) into the specimen. “Atomic resolution” in either the transmission electron microscope (TEM) or scanning transmission electron microscope (STEM) means that columns of atoms are resolved.Image contrasts in the backscattered electron (BSE) image are strongly affected by the specimen tilt and by the position and energy sensitivity of the BSE detector. The expression “BSE image” generally implies that the specimen is normal to the beam and the detector is above it. This shows compositional variations in the specimen with a spatial resolution limited by the spreading of the EB during the initial stages of penetration. This is similar in basic principle to the Z-Contrast method in the STEM that shows atomic resolution from a thinned single crystal mounted in the magnetic field of the focusing lens.

In Situ WetSTEM Observation of Gold Nanorod Self-Assembly Dynamics in a Drying Colloidal Droplet

2014 ◽  
Vol 20 (2) ◽  
pp. 385-393 ◽  
Author(s):  
Filip Novotný ◽  
Petr Wandrol ◽  
Jan Proška ◽  
Miroslav Šlouf
Keyword(s):  
Electron Microscopy ◽  
Self Assembly ◽  
Direct Method ◽  
Local Heating ◽  
Ex Situ ◽  
Transmission Electron ◽  
Nanoparticle Interactions ◽  
Scanning Transmission ◽  
Important Challenge

AbstractDirect in situ visualization of nanoparticles in a liquid is an important challenge of modern electron microscopy. The increasing significance of bottom-up methods in nanotechnology requires a direct method to observe nanoparticle interactions in a liquid as the counterpart to the ex situ electron microscopy and indirect scattering and spectroscopy methods. Especially, the self-assembly of anisometric nanoparticles represents a difficult task, and the requirement to trace the route and orientation of an individual nanoparticle is of highest importance. In our approach we utilize scanning transmission electron microscopy under environmental conditions to visualize the mobility and self-assembly of cetyltrimethylammonium bromide (CTAB)-capped gold nanorods (AuNRs) in an aqueous colloidal solution. We directly observed the drying-mediated AuNR self-assembly in situ during rapid evaporation of a colloidal droplet at 4°C and pressure of about 900 Pa. Several types of final AuNR packing were documented including side-by-side oriented chains, tip-to-tip loosely arranged nanorods, and domains of vertically aligned AuNR arrays. The effect of local heating by electron beam is used to qualitatively asses the visco-elastic properties of the formed AuNR/CTAB/water membrane. Local heating induces the dehydration and contraction of a formed membrane indicated either by its rupture and/or by movement of the embedded AuNRs.

scholarly journals Study of Phase Transition in MOCVD Grown Ga2O3 from κ to β Phase by Ex Situ and In Situ Annealing

Photonics ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 17
Author(s):  
Junhee Lee ◽  
Honghyuk Kim ◽  
Lakshay Gautam ◽  
Kun He ◽  
Xiaobing Hu ◽  
...  
Keyword(s):  
Phase Transition ◽  
Thermal Annealing ◽  
Chemical Vapor ◽  
Ex Situ ◽  
Organic Chemical ◽  
Β Phase ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Metal Organic

We report the post-growth thermal annealing and the subsequent phase transition of Ga2O3 grown on c-plane sapphire substrates by metal organic chemical vapor deposition (MOCVD). We demonstrated the post-growth thermal annealing at temperatures higher than 900 °C under N2 ambience, by either in situ or ex situ thermal annealing, can induce phase transition from nominally metastable κ- to thermodynamically stable β-phase. This was analyzed by structural characterizations such as high-resolution scanning transmission electron microscopy and x-ray diffraction. The highly resistive as-grown Ga2O3 epitaxial layer becomes conductive after annealing at 1000 °C. Furthermore, we demonstrate that in situ annealing can lead to a crack-free β-Ga2O3.

Sign in / Sign up

Export Citation Format

Share Document