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Novel carbon nanotube reinforced polymer derived ceramics by FAST
sintering processing
Niko Mantzel1, Stefan Rannabauer1, Ethel C. Bucharsky2, Karl G. Schell2,
Michael J. Hoffmann2, Michael Scheffler1*
1
Otto-von-Guericke University Magdeburg, Institute of Materials and Joining Technology
D-39106 Magdeburg, Germany
2
Karlsruhe Institute of Technology (KIT), Institute for Applied Materials – Ceramics in Mechanical Engineering
D-76131, Karlsruhe, Germany
ABSTRACT
CNT (carbon nanotube) reinforced composite ceramics are supposed to show excellent
mechanical properties. CNTs embedded in a ceramic matrix represent a high density of high
modulus fibers in a matrix material which may result in high bending strength, high hardness and
high fracture toughness. However, problems have been addressed in handling, compounding into
a matrix and at least of the price of CNTs. Another disadvantage is the liberation of CNTs into
the atmosphere during processing.
A possible way to avoid some of these problems is the in situ generation of CNTs within a
ceramic matrix. During the pyrolysis of preceramic polymers hydrocarbons are generated, and
the presence of a suitable catalyst in the matrix may be used to convert the evolving
hydrocarbons into CNTs. This was shown for a polysilsesquioxane resulting in a composite
material composed of a polymer derived ceramic (PDC) matrix with CNTs in open pores or
cracks formed during pyrolysis. After milling this composite material, sintering by a field
assisted sintering technology (FAST) was shown to result in a CNT reinforced PDC material.
In a very first attempt a series of CNT-PDC composites were manufactured resulting in ceramic
bodies with a Weibull modulus of about 17 and a corresponding strength of 109 MPa as
measured by a ball-on-3-balls test. The porosity was 10 % and the (micro) hardness exceeded
1400 HV 0.4/5. For comparison, a reference samples without catalyst and thus without CNTs
resulted in a higher porosity and a corresponding strength of only 89 MPa. This new
combination of the PDC route with in situ CNT formation and FAST processing might be a
possible route to manufacture dense PDCs with tailored properties in the SiOC system.
Keywords: polymer derived Ceramics, carbon nanotubes, FAST sintering
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