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MECHANICAL PROPERTIES OF YTTRIA-STABILIZED ZIRCONIA CERAMICS
by
Mahmood R Shirooyeh A
A Dissertation Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(MATERIALS SCIENCE)
December 2011
Copyright 2011 Mahmood R Shirooyeh A
Object Description
| Title | Mechanical properties of yttria-stabilized zirconia ceramics |
| Author | Shirooyeh A., Mahmood R. |
| Author email | shirooye@usc.edu;shirooyeh@gmail.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Materials Science |
| School | Viterbi School of Engineering |
| Date defended/completed | 2011-08-08 |
| Date submitted | 2011-10-03 |
| Date approved | 2011-10-03 |
| Restricted until | 2012-04-03 |
| Date published | 2012-04-03 |
| Advisor (committee chair) | Langdon, Terence G. |
| Advisor (committee member) |
Goo, Edward K. Sammis, Charles G. |
| Abstract | Superplasticity is a well-known characteristic of Y₂O₃-stabilized tetragonal zirconia (3Y-TZP) ceramic composites at elevated temperatures. The present investigation was originated to evaluate the potential of producing zirconia ceramics suitable for achieving superplasticity. ❧ High purity 3 mol% Y₂O₃-stabilized tetragonal zirconia (3Y-TZP) ceramic composites containing 20 wt% alumina were successfully consolidated by application of Cold Isostatic Pressing (CIP) followed by a subsequent sintering process. Constant-stress tensile creep experiments at elevated temperatures were conducted in order to examine plastic deformation behavior of the material. In addition to mechanical testing data, the microstructure observations confirmed superplastic properties of the ceramic composite. ❧ It is also known that in order to attain High Strain Rate Superplasticity (HSRS) in zirconia ceramics, it is essential to retain a stable fine-grained microstructure at high temperatures. Experiments have confirmed that adding a second soft phase such as spinel can facilitate to reach high strain-rate superplasticity in zirconia ceramics by suppressing grain growth during sintering process and enhancing cation diffusion. ❧ In the present investigation, homogenous 3Y-TZP ceramic composite powders containing 30 vol% MgAl₂O₄ spinel were successfully prepared through both physical-based and chemical-based methods. An electric current-activated method known as Spark Plasma Sintering (SPS) was employed for powder consolidation process. This is a very rapid electric current-activated sintering technique having a heating rate of 300 K/min. The powder preparation and consolidation steps were carried out over a wide range of conditions to ensure a homogenous nanocomposite. The experiments showed that fully-dense zirconia ceramics with an average initial grain size of the order of ~100 nm can be sintered at the relatively low processing temperature of 1373 K in 10 min. ❧ In order to study the superplastic behavior of the nanocomposite, creep tensile tests were performed in a temperature range of 1623—1723 K under different stress levels. Deformation mechanisms were investigated by detailed microstructure observations and quantitative evaluation of crystallite orientations using scanning electron microscopy and synchrotron radiation techniques. |
| Keyword | ceramic; creep; superplasticity; SPS; yttria-stabilized tetragonal zirconia |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m |
| Contributing entity | University of Southern California |
| Rights | Shirooyeh A., Mahmood R. |
| Physical access | The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright. The original signature page accompanying the original submission of the work to the USC Libraries is retained by the USC Libraries and a copy of it may be obtained by authorized requesters contacting the repository e-mail address given. |
| Repository name | University of Southern California Digital Library |
| Repository address | USC Digital Library, University of Southern California, University Park Campus MC 7002, 106 University Village, Los Angeles, California 90089-7002, USA |
| Repository email | cisadmin@dots.usc.edu |
| Archival file | uscthesesreloadpub_Volume71/etd-ShirooyehA-305.pdf |
Description
| Title | Page 1 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@dots.usc.edu |
| Full text | MECHANICAL PROPERTIES OF YTTRIA-STABILIZED ZIRCONIA CERAMICS by Mahmood R Shirooyeh A A Dissertation Presented to the FACULTY OF THE USC GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (MATERIALS SCIENCE) December 2011 Copyright 2011 Mahmood R Shirooyeh A |
