Silica fracture
| Autor: | J. K. West, L. L. Hench |
|---|---|
| Rok vydání: | 1994 |
| Předmět: |
Materials science
Contraction (grammar) Silicon Mechanical Engineering Fast fracture chemistry.chemical_element Ring (chemistry) Transition state Crystallography chemistry.chemical_compound chemistry Mechanics of Materials Siloxane Fracture (geology) General Materials Science Molecular orbital Composite material |
| Zdroj: | Journal of Materials Science. 29:3601-3606 |
| ISSN: | 1573-4803 0022-2461 |
| DOI: | 10.1007/bf00357324 |
| Popis: | A quantitative ring contraction model for the fracture of amorphous silica is described based upon AM-1 semiempirical molecular orbital calculations of strained three- and four-fold silica rings and a five-fold ring-chain structure. The fracture barrier for five-fold ring-chain structures is 103 kcal/mol. The barrier for fracture of a three-fold ring is 96 kcal/mol. Fracture by contraction of four-fold rings has a lower energy barrier of 77 kcal/mol due to formation of pentacoordinate silicon transition states which produce trisiloxane rings and a broken siloxane bond. Thus, the ring contraction model predicts that a crack will follow a path which depends on the distribution of four-fold (or larger) rings in vacuum or fast fracture |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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