Nanostructured materials from the Ti-Si-C system are of growing interest as multifunctional ceramic coatings in electrical and tribological applications. We have previously demonstrated beneficial electrical contact properties and a ductile deformation behavior for Ti-Si-C nanocomposite thin films deposited by magnetron sputtering from a Ti3SiC2 compound target [1] at substrate temperature below 300 °C [2]. Here, we report on detailed characterization of the microstructure of Ti-Si-C nanocomposites. As evidenced by XRD, TEM, and XPS, the Ti-Si-C films consist of TiC nanocrystallites (<20 nm), encapsulated by an interfacial tissue phase of amorphous SiC. The nc-TiC/a-SiC nanocomposite exhibited nanoindentation hardness and elastic-modulus values of 20 GPa and 290 GPa, respectively. Furthermore, in order to isolate and probe the TiC/SiC interface structure, we prepared planar interfaces in the form of TiC(111)/SiC multilayers by magnetron sputtering from Ti, Si, and C targets onto Al2O3(0001) substrates kept at temperatures below 500 °C. While SiC normally grows amorphously at these low temperatures, we demonstrate epitaxial stabilization of up to 2-nm-thick cubic (3C-)SiC in the multilayer structure. An implication is that epitaxial stabilization of the tissue phase may add an important design opportunity for strengthening of nanocomposite materials, due to the coherent crystalline interface with strong interfacial bonding between the nanocrystalline grains and the tissue phase.
[1] Maxthal® 312, courtesy of Kanthal AB
[2] P. Eklund et al J. Vac. Sci. Technol. B 23 2486 (2005)
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