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Spark plasma sintering novel tooling design: Temperature uniformization during consolidation of silicon nitride powder

: Giuntini, Diletta; Räthel, Jan; Herrmann, Mathias; Michaelis, Alexander; Haines, Christopher D.; Olevsky, Eugene Al

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Journal of the Ceramic Society of Japan 124 (2016), Nr.4, S.403-414
ISSN: 0912-9200
ISSN: 0914-5400
ISSN: 1348-6535
ISSN: 1882-0743
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IKTS ()
field-assisted sintering techniques; finite-element modeling; silicon nitride; spark plasma sintering; Rapid Tooling

Spark Plasma Sintering (SPS) of silicon nitride is affected by temperature non-uniformities within the powder compact, resulting in density and microstructure inhomogeneities. A double-pyrometer experimental setup reveals a temperature disparity of 100-200° C between the overheated outer surface of the die and the bottom of the upper punch, as a consequence of the electric current concentration through the die's wall characterizing the SPS of non-conductive powders utilizing conventional SPS tooling. A novel tooling design, consisting in the tailored drilling of axial cylindrical or ring-shaped holes within the punch, is individuated and optimized through a campaign of fully-coupled thermal, electrical and mechanical finite element simulations. The analysis of the numerical results, experimentally assessed, allows for a comprehensive understanding of the phenomena underlying radial temperature distributions in SPS and leads to the development of a technological solution for the uniformization of temperature distribution.