ENGS 88 Honors Thesis (AB Students)
Author ORCID Identifier
Degree Program
A.B.
Year of Graduation
2024
Faculty Advisor
Dr. Yan Li
Document Type
Thesis (Senior Honors)
Publication Date
Spring 6-5-2024
Abstract
Polymer-derived ceramics (PDCs) have found a wide range of uses typically being in high temperature or corrosive environments. Some of the current applications are in aerospace, energy storage and microelectromechanical devices. One growing interest is in additively manufacturing PDCs, as they can be printed in the polymer state, then heat treated to form a ceramic. This allows for complex, or small geometries, to be manufactured and aids in decreasing the complexity of the manufacturing process compared to traditional sintering techniques. However, one limitation of PDCs is the large shrinkage of the material and or the increased porosity due to volatile gases leaving during heat treatment, as the polymer transforms into a ceramic. These limitations can be overcome by the addition of fillers, such as passive fillers. Inert passive fillers reduce the shrinkage by reducing the percentage of preceramic polymer that undergoes shrinkage during pyrolysis. Another benefit of passive fillers is their ability to alter the properties of the bulk material.
In this study, the PDC of interest is silicon oxycarbide (SiOC) and the passive filler used is barium titanate (BTO). This passive filler has been shown to give SiOC preceramic polymers a piezoelectric effect when pyrolyzed at temperatures below 500 ℃ . Above this temperature, SiOC becomes conductive and unusable as a piezoelectric material. This study uses this composite in its amorphous ceramic/glass form. This study has found that the addition of a non-conductive filler, BTO, functions as a catalyst for conductive pathways increasing the conductivity of SiOC ceramics compared to samples of pure SiOC pyrolyzed at the same temperature. More generally, this study found that increasing pyrolysis temperature from 800 ℃ to 1200 ℃ increased conductivity with the largest increase being ~172-fold. Then increasing the w.t.% of BTO content in the polymer formulation from 0 to 50 increased the conductivity by ~2.67-fold. All samples were 3D printed using a digital light processing (DLP) printer so that future research on this material can implement small design features and metastructure designs.
Dartmouth Digital Commons Citation
Henry, Jace R., "Mechanical and Electrical Characterization of Conductive Polymer-Derived Ceramic Composite" (2024). ENGS 88 Honors Thesis (AB Students). 36.
https://digitalcommons.dartmouth.edu/engs88/36
