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Synthesis and tribology of Sialon/TiB2 ceramic composites
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Jones, Alan Hywel (1997) Synthesis and tribology of Sialon/TiB2 ceramic composites. PhD thesis, University of Warwick.
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WRAP_thesis_Jones_1997.pdf - Submitted Version Download (23Mb) | Preview |
Official URL: http://webcat.warwick.ac.uk/record=b1362827~S1
Abstract
The inclusion of TiB2 particles in a Si3N4 or sialon matrix has the potential to
improve the materials properties over those of the Si3N4 alone. The combination
of the excellent properties of sialon and the high hardness of the TiB2 makes
these materials potentially suitable for tribological applications. This research
has investigated the use of chemical reactions that can take place during
sintering to synthesise TiB2 from TiN and BN. The reactions not only produce
TiB2 but simultaneously synthesise the matrix material. The sialon matrix is
used as a flexible receptor for excess nitrogen and oxygen.
Using such reactions, sialonlTiB 2
composites were successfully produced by
both hot pressing and pressureless sintering. It was shown that these materials
achieve densities close to the theoretical and contain only the required phases of
TiB2 and ~ sialon. Pressureless sintered materials also contain residual sintering
aid as an intergranular phase.
The composites wee characterised with respect to their microstructure,
hardness, fracture toughness and tribological properties. A specially designed
wear test apparatus was constructed for the tribological testing. The pin-on-disc
apparatus was capable of testing the small volumes of material (minimum
diameter of disc ~ 15mm) typically produced at the development stage.
The materials were found to have high hardness and reasonable fracture
toughness which was attributed primarily to the properties of the matrix phase
with some possible toughening from the presence of TiB 2 . Tribological testing
revealed high dry sliding coefficients of friction (Jl) for the composites sliding
on themselves and reasonable values for the wear coefficient (k) were measured.
Wear was found to be dominated by tribochemical reactions forming tribofilms
which act to reduce wear of the disc. However, the presence of TiB2 was not
seen to contribute directly to the tribological properties of these materials and
the usefulness of this type of composite is questioned.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QC Physics | ||||
Library of Congress Subject Headings (LCSH): | Composite materials, Ceramic-matrix composites, Ceramics -- Research , Tribology -- Research | ||||
Official Date: | September 1997 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Physics | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Sponsors: | Lewis, Mike, Prof. | ||||
Extent: | xiii, 199 leaves : illustrations | ||||
Language: | eng |
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