3D printing of functional chemically bonded phosphate ceramics

• Main Author: Gonzales, Paula Germaine
• Other Authors: Nripan Mathews
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Materials::Ceramic materials
• Online Access: https://hdl.handle.net/10356/156232
• Institution: Nanyang Technological University

With the development in material science and engineering, additive manufacturing of ceramics has become the latest trend in research. However, aside from the challenge to print complex ceramics structures with well-defined features, traditional ceramics also bring harm to the environment. Thus, research on chemically bonded phosphate ceramics is quickly advancing to provide more sustainable ceramic materials that offer a diverse range of applications in the advanced manufacturing industry. In this study, the fabrication, characterisation, and analysis of alumina ceramics have been investigated to achieve a material that is printable with good microstructure and mechanical properties. The ultimate goal was to formulate an alumina slurry that is 3D printable and to produce highly dense and functional alumina ceramics. This was achieved by exploring different compositions of phosphate gel and Al_2 O_3, utilising various moulds, and mixing methods. Additionally, the reduction of Al_2 O_3 particle size through the ball milling process was also studied to determine the overall effect on the morphology and density of alumina ceramics. The introduction of mechanical fillers such as wollastonite and glass nanoparticles was also investigated to further broaden the functions of alumina ceramics. Results obtained from experiments show that alumina slurry consisting of 58% phosphate gel and 42% Al_2 O_3 with an average particle size of 99.94 µm has a viscosity that was suitable for 3D printing. The slurry was mixed and defoamed using a thinky mixer machine for 1 minute and 30 seconds, respectively. The alumina slurry was able to extrude a well-defined layered structure with excellent shape retention. The usage of gypsum as a base mould has also produced an alumina ceramic with high density and reduced pore size and distribution. The 5 wt.% of glass nanoparticles showed an increase in ultimate compressive strength and flexural strength. Based on experimental observations, it was concluded that alumina chemically phosphate ceramics were considered suitable for 3D printing. Due to the limited time, not all wollastonite concentrations could be investigated in this project. Future studies on the characterisation of 3D printed alumina ceramics are recommended to investigate its printing suitability.