Category: LEXI seminar

Date/time: Thursday July 30^th, 10am-12:00

Room: 3008 Calit2 building

Abstract:  3D Image Visualization, Analysis & Model Generation for Materials Applications with Simpleware

This technical seminar is aimed at those interested in visualizing, measuring and meshing of 3D image data to generate 3D Printing, CAD & Finite Element models for leading solvers.  We will demonstrate the ease of obtaining high fidelity meshes from 3D image data, discuss new features of the latest version, and will show the workflow of processing and meshing image data for a variety of applications.

Date/Time: Monday, Dec 8, 11:00 am – 12:00 pm

Venue: ET 331

Presenter: Dr. Paromita Kundu

From External Morphology to Atomic Structure under the Electron Microscope

Paromita Kundu^a,b,c, Stuart Turner^a, Hamed Heidari^a, Sandra Van Aert^a, Sara Bals^a, N. Ravishankar^b and Gustaaf Van Tendeloo^a

^a Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171,  2020 Antwerp, Belgium

^b Materials Research Center, Indian Institute of Science, Bangalore 560012, India

^c Institute of Bioelectronics (PGI-8), Forschungszentrum Jülich, D – 52425 Jülich, Germany

E-mail: paro.124@gmail.com

Abstract: Analysing the external shape and internal arrangement of a nanostructured material can lead us to understand its behaviour and tune its properties. Advanced electron microscopy emerged as a powerful technique to quantify these aspects of a nanostructure.

HRTEM combined with image simulation and exit wave reconstruction can provide information on the local atomic structure, however, with aberration corrected microscopes and advanced analytical methods one can analyse the structure with picometer precision. This method is limited to atomically thin samples. Besides, electron tomography provides a way to reconstruct the 3D volume of the specimen from a series of 2D projection images. In case of nanoscale heterostructures electron tomography is a promising technique to understand the ordering of the heterounits whether the mixing is at atomic level or at the nanoscale.  It allows us to visualize the external morphology as well as derive the real atomic constitution of the nanostructure in 3D using (HR)STEM images taken at a series of tilt angles and from different zone axes, respectively. Here we demonstrate the case of  nanoscale heterostructures and 1D metal wires where HAADF-STEM tomography and aberration corrected high resolution microscopy are used to understand the structure and morphology. We investigated ultrathin gold nanowires to deduce its atomic structure using low dose microscopy and recorded beam induced structural changes at the atomic scale using aberration corrected HRTEM. This shows a relaxed structure extending towards the surface meaning a relatively large strain in the outermost layer of atoms indicating its potential for an efficient catalytic material. At higher dose we observe the dynamics of the atomic columns leading to the breaking of the wires. Other than the atomic structures, in nanohybrids the external combination of the building units is important to characterise as this influences its properties. HAADF-STEM electron tomography on Au-SiO₂ spheres will also be demonstrated. The material is a potential catalyst and the distribution of Au on silica will certainly influence its activity. A 3D reconstruction from a series of HAADF-STEM images renders the volume which shows that the Au is embedded in the outermost layer of the silica spheres. Tomography performed on the intermediate structures formed in the reaction medium reveals that initially a 3D self assembly of Au particles forms, which in the presence of silica precursors results in such spherical morphology. The thermal stability of the structures are investigated and tomography reveals a good stability of the structure, however, at high temperatures the Au particles migrate inside the matrix although the external shape of silica remains intact. Some of these results will be discussed in the presentation.

To help LEXI users understand TEM literatures and operations, 4 lectures as listed below have been scheduled for Nov 14, 19, 21, 26. The lecture time is between 12:30 to 2pm. Lecture room is 1322 Calit2.
Here are the lecture titles:
Lecture1: TEM electron optics- principles and operations
Lecture2: Electron diffraction- principles and applications
Lecture3: TEM image contrast mechanisms
Lecture4: TEM specimen preparation by using FIB techniques

Dear SEM users:

Here is a notice about LEXI seminar:

Title : SEM Basic Concepts and Principles-FEI XL-30 FESEM
Time/date: 2pm-3pm, Jan 30, 2013
Venue: 3008 Calit2
Speaker: Jian-Guo Zheng

Abstract: This seminar aims to help new SEM users understand basic concepts and principles. Using FEI XL-30 FESEM as an example, this seminar is not limited to any particular SEM instrument. The correlation between operations and principles will be covered. This seminar will also illustrate some SEM applications.

If you want to attend this seminar and have not signed up, please visit the link below:
https://docs.google.com/spreadsheet/ccc?key=0AlVa2cfmNf6XdEEtMmZqUnk4Sm5fUU5FdzN6NWRxcmc#gid=0

I would appreciate it if you could forward this notice to anyone who might be interested in. It is free to attend this seminar.

Thanks,

Jian-Guo

The 2nd LEXI seminar about Quanta 3D FEG dualbeam system will be held on Sept 21 (2-3pm) in 3008 Calit2 building. If you have not signed up, here is the link to the sign-up page:
https://docs.google.com/spreadsheet/ccc?key=0AlVa2cfmNf6XdEEtMmZqUnk4Sm5fUU5FdzN6NWRxcmc#gid=0
See you on this Friday.
Jian-Guo Zheng