Virginia Tech
Synthesis and characterization of in situ whisker-reinforced glass-ceramics
Abstract
dc:description.abstractThe effects of in situ Ti0₂ whisker reinforcement on mechanical and thermal properties of glass-ceramics in the Li₂O-Al₂0₃-P₂0₆-Si0₂ system were investigated. When Ti0₂ whiskers, having an average aspect ratio of 28, are precipitated from the glass-ceramic matrix, (Li<sub>0.4</sub>,Ca<sub>0.05</sub>)AI(Si<sub>0.75</sub>,P<sub>0.5</sub>)<sub>04.5</sub>, flexural strength is improved from 72 to 134 MPa. Fracture toughness, K<sub>Ic</sub>, is increased from the 1.1 to 1.6 MPa·m<sup>1/2</sup> due to crack deflection by the Ti0₂ whiskers. In situ Ti0₂ whisker-reinforced glass-ceramic exhibits rising fracture resistance, K<sub>R</sub>, with increasing crack extension. The fracture resistance, K<sub>R</sub>, is increased from 1.89 to 2.5 MPa·m<sup>1/2</sup> over the crack extension range range of 40 to 200 μm. The composite shows a narrow failure strength distribution compared to the glass-ceramic without Ti0₂ whisker precipitation. The coefficient of thermal expansion (CTE) changes from -2.8x10⁻⁷/"C to -1.7xl0⁻⁷/°C due to the precipitation of Ti0₂ phase which has a positive CTE (7.3xl0⁻⁶/°C). With the matrix composition, (Li<sub>0.41</sub>,Mg<sub>0.035</sub>)AI(Si<sub>0</sub>0.48</sub>,P<sub>O.52</sub>)O₄, a three-fold increase in flexural strength was observed with a Ti0₂ content of 12 wt%. CTE value of the composite increases linearly from a negative to a positive value with increasing Ti0₂ content up to 12 wt%. The in situ composite containing 8-10 wt% Ti0₂ exhibits near zero CTE values up to l000°C.
Degree
thesis:*- Name thesis:degree_name
- Ph. D.
- Level thesis:degree_level
- doctoral
- Discipline thesis:degree_discipline
- Materials Engineering Science
- Department dc:contributor.department
- Materials Engineering Science
- Grantor dc:publisher
- Virginia Tech
- Year dc:date.issued
- 1993
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Lee, Kyoung-Ho
- Chair dc:contributor.committeechair
-
- Brown, Jesse J., Jr.
- Committee members dc:contributor.committeemember
-
- Gordon, Ronald S.
- Gibbs, Gerald
- Hirschfeld, Deirdre A.
- Reynolds, William T. Jr.
Rights
dc:rights- Statement dc:rights
-
- In Copyright
- Licence dc:rights.uri
- Language dc:language.iso
- en
Identifiers
dc:identifier.*- Dc Identifier Other
- etd-06192006-125732
- OAI identifier oai:identifier
- oai:vtechworks.lib.vt.edu:10919/38638