Enhancing the Flexural Strength of AlN with an Additional Cross-Linking Mechanism in the Aqueous Isobam Gelling System

Abstract

Isobam is widely used for fabricating ceramics through spontaneous gelation and has attracted considerable interest. However, the disadvantage of the Isobam system is the low gelation strength. The effects of suitable additives and the mechanism by which they effectively enhance the green body strength and the rheological behavior of an aluminum nitride (AlN) slurry with 50 vol% solid loading were investigated using polyethyleneimine (PEI), hydantoin epoxy resin, and trimethylolpropane triglycidyl ether (TMPGE). Results showed that the additives acted as both dispersants and cross-linkers in the AlN suspension using the Isobam gelling system. The flexural strength of the AlN green body increased by 42%, 204%, and 268% with the addition of 1 wt% PEI, 1 wt% hydantoin epoxy resin, and 0.5 wt% TMPGE, respectively. After sintering at 1700 °C, the AlN ceramic with 0.5 wt% TMPGE had flexural strength and thermal conductivity of 235 MPa and 166.44 W/(m·K), respectively, showing superior performance to the ceramics without additives.