| 1. |
- Jämting, A., et al.
(author)
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Mechanical characterization of kappa and alpha alumina films on hardmetals using indentation methods
- 1995
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In: Journal of Hard Materials. - 0954-027X. ; 6:2, s. 67-87
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Journal article (peer-reviewed)abstract
- The mechanical properties of thin films of two allotropic modifications of alumina have been examined. These coatings were chemically vapour deposited onto cemented carbide substrates and the film thickness was 6 and 4 μm respectively for the alpha and kappa alumina. Indentations on the films and substrate were conducted with an ultra microindentation system using diamond Berkovich and small, spherical-tipped indenters. Analysis of the data showed differences between the two different allotropes. The kappa alumina was slightly harder than the alpha phase, although the modulus showed the opposite response. The resultant spherical indentation-induced stress-strain curves for the films are also compared with those of the cemented carbide substrate. SEM pictures of the indentations revealed evidence for both brittle and plastic behaviour of the alumina films
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| 2. |
- Nilsson, M., et al.
(author)
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A Critical Appraisal of the Interfacial Toughness of Ceramic Matrix Composites Using Indentation Techniques
- 1999
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In: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 161-163:675-680, s. 675-680
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Journal article (peer-reviewed)abstract
- Advanced ceramic matrix composites provide a challenge for both manufacturer and user necessitating better techniques to critically appraise their properties. Interfacial toughness and the change of this property with application time at elevated temperature in hostile environments is of paramount importance for structural integrity/reliability of these materials. The present study investigates two such composite systems; a mullite matrix reinforced with silicon carbide fibres, and a novel oxide composite using sapphire fibres within an alumina-zirconia matrix. The interfacial toughness between the fibres and matrix was evaluated using nano- and micro-indentation fracture toughness methodologies. The results are interpreted in terms of recent theoretical interfacial fracture mechanics analysis by Hutchinson and Suo[1] for cracks approaching and extending along an interface. Nano-indentation has also been used to evaluate the intrinsic elastic/plastic properties of the CMC materials
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| 3. |
- Westman, Anna-Karin, et al.
(author)
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Ultra-micro indentation technique used for examination of mechanical properties close to a HIPed surface of silicon nitride
- 1998
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In: Journal of the European Ceramic Society. - 0955-2219 .- 1873-619X. ; 18:7, s. 879-890
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Journal article (peer-reviewed)abstract
- Ultra-micro indentation using both pointed and spherical tipped indenters has been used to characterize mechanical properties of silicon nitride densified by glass encapsulated hot isostatic pressing (HIP). Young's modulus and hardness have been studied as a function of distance to the interface between silicon nitride and the encapsulation glass. The Young's modulus values are 10 to 20% lower in the close vicinity of the silicon nitride surface compared to bulk values. At distances of 75 to 150 microns from the glass-silicon nitride interface, bulk values are measured. The differences in hardness values between the region close to the surface and the bulk is less pronounced. A possible explanation for these gradients is formation of new phases at the surface of the silicon nitride. Routines for the calibration of both the pointed and spherical tipped indenters are presented
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