Micro-fabrication of glassy carbon with low shrinkage and high char yield using high-performance photocurable phthalonitrile (PN) resins

Abstract

Glassy carbons (GCs) are a significant class of materials that have attracted considerable attention in many scientific and technical fields due to their great thermal and chemical stability, excellent biocompatibility, and remarkable thermal and electrical conductivity. However, the thermal resistance and brittle nature of GCs pose limitations on their processing using conventional techniques such as melting extrusion or sintering. 3D printing as a rapidly developing technology advances product fabrication in prototyping and tooling provides a revolutionizing alternative of material processing with the advantage of accurately producing complex structures/shapes. This study demonstrates the micro-fabrication of GC objects based on novel photocurable high-performance phthalonitrile (PN) resins with a vat photopolymerization printing technology named as projection micro stereolithography (PμSL). In initial, soluble acrylate PN monomers are successfully developed and subsequently formulated into photopolymerizable resins. The resultant resins show excellent thermal and mechanical properties with Tg around 300 °C and flexural strength of 150 MPa after post thermal treatment. Being fabricated into 3D structures via PμSL printing, the obtained PN based objects are converted to GC products through pyrolysis in inert atmosphere with high char yield and low shrinkage. As a result, diverse microscale 3D GC objects are achievable and exhibit excellent structural integrity and fidelity. Our approach develops the micro-fabrication of dense and complex structured GC for the first time, providing a versatile functional platform for advancing next generation applications in medical tools, electrochemistry and precision micro-moulding as well as in energy and aerospace technologies.