Biomedical Engineering Reference
In-Depth Information
4.24 Influence of different rare earths on (a) the friction coefficient and
(b) the specific wear rate of Si 3 N 4 monoliths and Si 3 N 4 -SiC composites.
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It is well known that the bonding strength between Si 3 N 4 grains and grain
boundary phases increases with the decreasing ionic radius of RE 3+ .
Therefore the highest bonding strength in Si 3 N 4 containing Lu 2 O 3 as a
sintering additive restricts dropping of the individual silicon nitride grains
during the wear experiment. This fact, together with its high hardness and
fracture toughness values, are the reasons why Si 3 N 4 doped with Lu
exhibited the best wear resistance among all the studied monolithic
materials. The addition of SiC nanoparticles in this class of materials
leads to lower fracture resistance. However, the composites exhibited higher
wear resistance in comparison with that of monolithic Si 3 N 4 . This is
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