Annealing-induced improvement in thermal conductivity of Si3N4 specimens produced by vat photopolymerization: A comparative study of vat photopolymerization and cold isostatic pressing

This study addresses challenges in manufacturing high-quality silicon nitride (Si 3 N 4 ) products using vat photopolymerization (VPP), a method that enables highly precise and complex manufacturing that was previously unachievable. A comparison of VPP and cold isostatic pressing (CIP) showed that the intergranular phases of VPP samples exhibited continuous network assembly, while the intergranular phases of CIP samples were dispersed and aggregated. For densification, VPP samples required more aggressive sintering conditions and a higher MgO content. This prolonged densification process adversely affected thermal conductivity, only reaching a maximum of 70.91 W m −1 ·K −1 . Through annealing, thermal conductivity of VPP sample improved by 72.44 %, narrowing the gap with CIP sample (90.28 W m −1 ·K −1 ) and reaching up to 96.20 W m −1 ·K −1 . Si 3 N 4 sample exhibiting high flexural strength of 908.28 ± 46.90 MPa were prepared using VPP. This study proposes a viable approach for producing high-performance Si 3 N 4 heat exchangers and other complex devices via VPP.