English
 
Help Privacy Policy Disclaimer
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT

Released

Journal Article

In Situ Observations of Phase Transitions in Metastable Nickel (Carbide)/Carbon Nanocomposites

MPS-Authors
/persons/resource/persons21743

Knop-Gericke,  Axel
Inorganic Chemistry, Fritz Haber Institute, Max Planck Society;

/persons/resource/persons22071

Schlögl,  Robert
Inorganic Chemistry, Fritz Haber Institute, Max Planck Society;

External Resource
No external resources are shared
Fulltext (restricted access)
There are currently no full texts shared for your IP range.
Fulltext (public)

acs.jpcc.6b01555.pdf
(Publisher version), 6MB

Supplementary Material (public)

Bayer et al - in-situ Ni-C nanocomposites_SI.pdf
(Supplementary material), 168KB

Citation

Bayer, B. C., Bosworth, D. A., Michaelis, F. B., Blume, R., Habler, G., Abart, R., et al. (2016). In Situ Observations of Phase Transitions in Metastable Nickel (Carbide)/Carbon Nanocomposites. The Journal of Physical Chemistry C, 120(39), 22571-22584. doi:10.1021/acs.jpcc.6b01555.


Cite as: https://hdl.handle.net/11858/00-001M-0000-002B-4976-7
Abstract
Nanocomposite thin films comprised of metastable metal-carbides in a carbon matrix have a wide variety of applications ranging from hard coatings to magnetics and energy storage and conversion. While their deposition using non-equilibrium techniques is established, the understanding of the dynamic evolution of such metastable nanocomposites under thermal equilibrium conditions at elevated temperatures during processing and during device operation remains limited. Here, we investigate sputter deposited nanocomposites of metastable Ni carbide (Ni3C) nanocrystals in an amorphous carbon (a-C) matrix during thermal post-deposition processing via complementary in-situ X-ray diffractometry, in-situ Raman spectroscopy and in-situ X-ray photoelectron spectroscopy. At low annealing temperatures (300 °C) we observe isothermal Ni3C decomposition into face-centered-cubic Ni and amorphous carbon, however, without changes to the initial finely structured nanocomposite morphology. Only for higher temperatures (400-800 °C) Ni-catalyzed isothermal graphitization of the amorphous carbon matrix sets in, which we link to bulk-diffusion-mediated phase separation of the nanocomposite into coarser Ni and graphite grains. Upon natural cooling, only minimal precipitation of additional carbon from the Ni is observed, showing that even for highly carbon saturated systems precipitation upon cooling can be kinetically quenched. Our findings demonstrate that phase transformations of the filler and morphology modifications of the nanocomposite can be decoupled which is advantageous from a manufacturing perspective. Our in-situ study also identifies the high carbon content of the Ni filler crystallites at all stages of processing as the key hallmark feature of such metal-carbon nanocomposites that governs their entire thermal evolution. In a wider context, we also discuss our findings with regard to the much debated potential role of metastable Ni3C as a catalyst phase in graphene and carbon nanotube growth.