Abstract
Multiwalled-carbon-nanotube (MWCNT)-reinforced silicon nitride coatings were grown to evaluate the toughness contribution of nanotubes in a ceramic coating. An MWCNT array was first grown using catalytic chemical vapor deposition of acetylene on a silicon substrate. This aligned MWCNT preform was then infiltrated with an amorphous silicon nitride matrix by low-pressure chemical vapor deposition of dichlorosilane (DCS) and ammonia (NH3). The fracture toughness of this material was determined by generating cracks using nanoindentation and then employing finite-element analysis to estimate the bridging toughness contribution of the MWCNTs. The MWCNT bridging toughness of the composites is determined to be ∼5.6MPam1/2, which is seven times higher than that of the matrix. The interfacial frictional stress is also estimated and ranges from 7 to 20MPa.
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