Deshmukh, Pushkarraj Vasant
(2008)
DESIGN AND DEVELOPMENT OF AN ENVIRONMENTAL CELL FOR DYNAMIC IN SITU OBSERVATION OF GAS-SOLID REACTIONS AT ELEVATED TEMPERATURES.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
In situ monitoring of events in transmission electron microscopy provides information on how materials behave in their true state while varying environmental conditions (i.e. temperature and pressure) and exposure to reactant gas mixtures. In-situ results are usually different from static, post-reaction observations because they provide valuable real time - rather than post mortem - information. To facilitate applications that demand in situ observations, a transmission electron microscope specimen holder assembly has been developed in this dissertation. This assembly incorporates a gas flow and heating mechanism along with a novel window-type environmental cell. A controlled mixture of up to four different gases can be circulated through the cell during an experiment. In addition, the specimen can be heated up to a temperature of 1500 °C using a specially designed carbon dioxide laser mechanism. This heating technique provides major advantages over conventional methods in terms of product life, specimen heating time and design size. The cell design incorporates a gas reaction chamber less than 1 mm in height, enclosed between a pair of 20 nm thick silicon nitride windows. The chamber can accommodate a specimen or a grid having a diameter of 3 mm and thicknesses in the range of 50 to 100 microns. The volume for the gas environment within the chamber is approximately 3 mmc and the gas path length is less than 1 mm. This holder has been designed by incorporating cutting edge heating and MEMS technology to achieve excellent resolution along with a low thermal drift. Successful application of the holder has been shown to provide scientists with an economical alternative to dedicated transmission electron microscopes for a vast array of in situ applications. These applications include understanding the basic material properties, catalysis reactions, semiconductor device development, and nano structure fabrication.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
10 June 2008 |
| Date Type: |
Completion |
| Defense Date: |
3 April 2008 |
| Approval Date: |
10 June 2008 |
| Submission Date: |
23 March 2008 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Mechanical Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
DTEM; E-Cell; Environmental Cell; Heating holders; Laser heating; TEM; Window type; Catalysis; ETEM; Specimen holders |
| Other ID: |
http://etd.library.pitt.edu/ETD/available/etd-03232008-142852/, etd-03232008-142852 |
| Date Deposited: |
10 Nov 2011 19:32 |
| Last Modified: |
15 Nov 2016 13:37 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/6562 |
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