Pyrolysis of 3D Printed Photopolymers: Characterization and Process Development

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3D printing has shown to be instrumental in the development of complex structures that have been previously unobtainable through traditional manufacturing processes. Photopolymers have been used in lithography-based 3D printing techniques for decades and have shown to be easily printed from the micro to macro scales. The thermal decomposition, or pyrolysis, of patterned photopolymers of microscale and mesoscale has been shown to create carbon devices such as carbon micro electromechanical systems (MEMS) and electrodes. In this dissertation, I present the characterization of pyrolyzed photopolymers 3D printed via stereolithography (SLA) and two-photon polymerization (2PP). Furthermore, processes in which to bolster the material properties of the pyrolyzed materials was examined.First, I study the effects of increasing the pyrolysis temperature on 2PP photopolymers and how this changes the electrical conductivity and microstructure of the material. From this it was shown the ability to vary the conductivity of 3D printed and pyrolyzed glassy carbon parts by up to 500X through only the temperature of pyrolysis, including reaching conductivities an order of magnitude higher than previously reported work. By extending the characterization of pyrolyzed photopolymers to SLA photopolymers I am able to further develop a generalized understanding of the electrical and microstructural properties of pyrolyzed 3D printed photopolymers. Further, demonstrate a metric in which to understand the deformation of the material during pyrolysis and perform an electrical and microstructural study of the material. Secondly, I investigate increasing the electrical and mechanical properties of pyrolyzed photopolymers through metals deposition via electroplating. In doing so I introduce a novel technique on which to electrodeposit on the surface of pyrolyzed SLA and 2PP 3D printed parts. Metallizing these pyrolyzed samples showed to increase both the electrical conductivity and ultimate strength of both pyrolyzed photopolymers. Lastly, I looked at increasing the stiffness of the pyrolyzed photopolymers through the addition of hBN filler into the precursor photopolymer. In doing so I examine the manufacturing of the composite hBN containing photopolymers for 3D printing with SLA and 2PP systems. Following 3D printing and pyrolysis of the hBN/photopolymer composite compositional and microstructural analysis is performed. Mechanical testing of the pyrolyzed composites shows that a slight increase in the stiffness of the material is observed. I have shown the ability to control the electrical conductivity and microstructure of pyrolyzed 3D printed photopolymers through pyrolysis temperature. Through the addition of metals via electroplating I demonstrate a process by which to increase the electrical conductivity and ultimate strength of pyrolyzed photopolymers and through the addition of hBN into the precursor photopolymer I have shown a way to increase the stiffness of the pyrolyzed materials. These processes have already demonstrated the ability to 3D printed electrical devices and have laid out a groundwork for future development of 3D printed electronics, energy-storage devices, and shielding.