Self-organized nanocolumnar structure in superhard TiB{sub 2} thin films
- Department of Physical Metallurgy and Materials Testing, University of Leoben, A-8700 Leoben (Austria)
TiB{sub 2} thin films are well known for their high hardness which makes them useful for wear-resistant applications. Overstoichiometric TiB{sub 2} deposited at 300 deg. C by nonreactive sputtering has been shown to exhibit superhardness (H{>=}40 GPa), while the hardness of their bulk stoichiometric counterparts is {approx}25 GPa. We show, using high-resolution transmission electron microscopy, that overstoichiometric TiB{sub 2.4} layers have a complex self-organized columnar nanostructure. The {approx}20 nm wide columns, encapsulated in excess B and oriented along 0001, consist of a bundle of {approx}5 nm diameter TiB{sub 2} subcolumns separated by an ultrathin B-rich tissue phase. The nanocolumnar structure, which is thermally stable to postannealing temperatures up to 700 deg. C, inhibits nucleation and glide of dislocations during hardness indentation measurements, while the high cohesive strength of the B-rich tissue phase prevents grain-boundary sliding. The combination of these effects results in the observed superhardness of {approx}60 GPa.
- OSTI ID:
- 20637041
- Journal Information:
- Applied Physics Letters, Vol. 86, Issue 13; Other Information: DOI: 10.1063/1.1887824; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
- Country of Publication:
- United States
- Language:
- English
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