Additive manufacturing of SiC whiskers-based structures for high temperature applications

• Main Author: Goh, Jaslyn Jie Lin
• Other Authors: Gan Chee Lip
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering
• Online Access: https://hdl.handle.net/10356/176144
• Institution: Nanyang Technological University

State-of-the-art technologies have resulted in an increase in the structural and functional requirements of advanced ceramics like SiC whiskers (SiCw) based structures, calling for unique structures that exhibit complex geometries. 3D printing processes such as vat photopolymerization (VPP), or specifically stereolithography (SLA) provides a means of overcoming the inherent limitations of conventional ceramics manufacturing processes as it is generally not constrained by geometry and can produce multi-material structures. However, VPP technology faces the challenge of having to balance the high refractive index and UV absorption of ceramic particles. Hence, this study aims to develop a photocurable resin (PCR) without the solid loading of ceramic particles in the 3D paste and explore the process parameters necessary for the growth of SiCw. Firstly, a systematic analysis on the effect of monomers with different functionalities and double bond densities was done to ensure minimal weight loss. The PCR with the best thermal stability (Tmax) and least weight loss (high R%) required synergy between double bond density, functionality and the presence of aromatic rings. Here, the TMTPA – Benzyl PCR achieved the highest Tmax of 466.11 °C and R% of 10.16 % in the ratio 4:6. Following that, 3D printing and carbonization parameters were optimized to yield structures with the best geometric fidelity and least weight loss. By analysing the effect of layer height, gas flow rate and the addition of photoabsorbers, greater geometric fidelity can be achieved via each layer being thinner, having a low gas flow rate and, the addition of photoabsorbers. Lastly, SiCw were grown in the carbothermal reduction phase, with extensive networks of continuous linear and curved nanowires ranging from 38 - 90 nm. However, an EDX elemental map further reveals the presence of unreacted Si and O on the surface of the structure; indicative of the incomplete conversion to SiCw. Nonetheless, this paves a way for the 3D printing of SiCw via SLA without the need for solid loading of ceramic particles.