Development of zirconium carbide suspensions for stereolithography 3D printing
Creators: name: Wirkijowski, Eliza Nina
Publisher: name: No Publisher Supplied
Year: 2024

description: This thesis outlines the process of developing zirconium carbide photocurable suspensions for use in additive manufacturing via a stereolithography apparatus. This study addresses the challenges in developing and printing with such materials, including the high density and poor stability of ZrC suspensions, refractive index difference between the ceramic and resin impacting cure depth, and platform and subsequent layer-to-layer adhesion. Development of suspensions followed a formulation previously developed for Si3N4, but changes had to be made to achieve a stable suspension. Adjustments were made in the dispersant type and content, particle size distribution, and solids content in the suspension. The impact of these changes on suspension dispersion were studied and dispersion was optimized using these parameters. Initial studies of the relationship between energy dose and cure depth of these iterations of the suspension were investigated. Though lower solids content suspensions had higher cure depth, the higher solids content of 20 vol% ZrC was selected to mitigate future densification issues. The effect of increasing the fines content in the particle size distribution on cure depth behavior was also studied. Initial formulation printing attempts were performed. Due to the low cure depth of the suspension, layers did not successfully adhere to the platform when printing with this formulation. Adjustments were made to the formulation and to the curing wavelength of the light to investigate the effects on cure depth and eventual printability. Resins were developed using two additional photoinitiators, and varied contents of photoinitiator were studied across all three photoinitiators studied. Suspensions were formulated using 3-6 wt% photoinitiator resins, and the cure depths of each were studied with increasing energy dose. Suspensions were cured using both 405 nm and 385 nm projectors. It was determined that suspensions containing 5 wt% Omnirad-819 (IGM Resins, Netherlands) had the greatest average cure depth of 19 μm at the highest energy dose when curing with the 405 nm projector. Initial layer adhesion to the platform was successful using an energy dose of 9020 mJ/cm2, or 100 second cure time at 80% power, and was further improved when the print platform was heated. Tension was formed between the film and the platform as the layers had a tendency to adhere to the film. As a result, problems arose when attempting to cure subsequent layers at this power and time setting. Using the maximum cure time of 120 seconds did not result in layer-to-layer adhesion, and layers remained adhered to the platform. Increasing the projector’s power to 85% resulted in successful adhesion of the layers, but cure times had to be reduced to prevent the projector from overheating. Layer-to-layer adhesion was found to be successful at lower cure times. A higher energy density was necessary to achieve subsequent layer adhesion when compared to initial layer adhesion. The tension effect between the layer and the film resulted in some damage as the film jogged, so adjustments were made to the platform up and down speed and distance to improve the adhesion to the previous layer and minimize damage. These findings indicate that printing with high refractive index ceramics using stereolithography processes is possible with limitations, and further work must be performed to determine how to improve print quality and efficiency when using materials such as zirconium carbide.