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Powder Processing, Rheology, and Mechanical Properties of Feedstock for Fused Deposition of Si 3 N 4 Ceramics
Author(s) -
Rangarajan Sriram,
Qi Gang,
Venkataraman Natesan,
Safari Ahmad,
Danforth Stephen C.
Publication year - 2000
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2000.tb01446.x
Subject(s) - materials science , extrusion , raw material , rheology , composite material , viscosity , ceramic , shear rate , shear thinning , chemistry , organic chemistry
Fused deposition of ceramics (FDC) is a technique in which green parts are fabricated directly from CAD designs. The feedstock for FDC is a 1.778 mm diameter filament that requires a low viscosity and high column strength. This study explores the powder processing science, as well as the rheological and mechanical properties required for a successful FDC feedstock material. GS44 Si 3 N 4 powders were dispersed in RU9 binder using oleyl alcohol (OA). The viscosity of the RU9/OA/Si 3 N 4 mixture was measured as a function of temperature, solids loading, and OA concentration. The mechanical properties of the filament feedstock were evaluated in compression to establish FDC process limits. The feedstock material shows a shear thinning behavior with OA acting mainly as a plasticizer. The viscosity of GS44‐filled RU9 decreases with temperature, and increases with solids content. At 185°C and 55 vol% loading, the viscosity was found to be in the range of 49–7 Pa·s for a corresponding shear rate of 70–1128 s − 1 . This was sufficiently low for FDC. Based on pressure requirements for FDC extrusion (Δ P ), and maximum sustainable stress without buckling by the filament (σ E ), it has been found that for successful FDC of RU955, 1.1Δ P < σ E .