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Constrained sintering of alumina stripes on rigid substrates: Effect of substrate roughness and coating

: Jamin, C.; Rasp, T.; Kraft, T.; Guillon, O.


Journal of the American Ceramic Society 98 (2015), No.12, pp.3988-3995
ISSN: 0002-7820
Deutsche Forschungsgemeinschaft DFG
GU 993/2-2
Deutsche Forschungsgemeinschaft DFG
KR 1729/10-2
Journal Article
Fraunhofer IWM ()

Micromolding in capillaries has been used to fabricate alumina stripes on smooth (Ra = 0.5 nm) and rough substrates (Ra = 900 nm). Different lateral (10-500 μm) and vertical stripe dimensions (8-27 μm) were used to study the influence of substrate roughness (smooth and rough sapphire) and substrate material (platinum coated and plain sapphire) on sintering behavior. Alumina stripes experience edge delamination during sintering on a rigid substrate independent of substrate roughness. However, enhanced substrate roughness reduced delamination length by half and lowered lateral strains by up to 0.10. Grooves in the rough substrate were found to be responsible for this feature as they act as crack propagation barriers and generate local density minima. Accompanying discrete element simulations revealed a localized triaxial stress state at the grooves of a sinusoidal-shaped substrate interface as the main cause of the density minima. Platinum interlayers also resulted in reduced delamination by 40% in some stripe geometries while density was enhanced by 4% and lateral strains doubled in some geometries. Creep of the metal layer during sintering is thought to be the reason for this seemingly contradictory behavior.