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C. Eisenmenger-Sittner, B. Schwarz, J. Hell, E. Neubauer:
"Application of Vacuum Based Processes for the Production of Metal Matrix Composites";
Poster: IUVSTA SPECIAL SYMPOSIUM, Seoul / Südkorea; 18.09.2006 - 19.09.2006.

Application of Vacuum Based Processes for the Production of Metal Matrix Composites

C. Eisenmenger-Sittner1, B. Schwarz1, J. Hell1, E. Neubauer2
1Institute of Solid State Physics, Vienna University of Technology, Vienna, Austria
2ARC Seibersdorf Research, Dept. Materials Research, A-2444 Seibersdorf

Metal-Matrix-Composites (MMC's) represent a material class with mechanical and thermal properties which are tuneable by the ratio of the constituents. Their main field of application are environments where the matching of thermomechanical characteristics is crucial. Carbon-fiber reinforced copper carbon MMC's are potential materials for heat sinks in high performance electronic components or fusion reactor components. These applications require a reliable joining of the two components which is a difficult task due to the immiscibility and the chemical inertness of Cu and C relative to each other. A commonly known route to produce Cu-C MMC's is the electrochemical coating of short C-fibers (approx. 0.5 mm length, 7-10 µm diameter) with copper and then consolidating the material by various compaction techniques as e.g. unidirectional hot pressing.
Within this presentation a different approach is chosen. It makes use of the potential of vacuum based techniques to overcome the problem of joining Cu and C. A wetting promoting Mo-interlayer is sputter deposited first on plane C-Substrates. By melting small Cu-Particles on uncoated and coated C-substrates within a commercially available High Vacuum (HV) -plant the excellent properties of the Mo-layer as wetting agent are shown.
After these basic investigations the crucial step is the uniform deposition of the Mo-interlayer on short Carbon fibers. For this purpose a special deposition system with rotating drums was constructed which allows for a reasonably uniform coating of granular and fibrous materials with dimensions in the µm scale. With this system short C-fibers with approx. 0.5 mm length and 7-10 µm diameter were coated with Mo. The uniformity of the coating was evaluated in an optical microscope. Batches of fibers, one with and one without Mo-interlayer were coated with Cu in the same deposition system. These fibers were heat treated at 800°C under HV and the Cu-coating was characterized in respect to de-wetting from the Carbon fibers within a Scanning Electron Microscope (SEM). While clear evidence of de-wetting and agglomeration was observed on the SEM images of uncoated fibers, the Cu-layer recrystallized, but remained continuous on the Mo-coated fibers.
These results show that the combination of vacuum based techniques for the production and characterization of coatings on plane and also on irregular, granular substrates may serve as an important tool for the development and manufacturing of new composite materials.