ORCID Identifier(s)

0000-0002-7363-9740

Graduation Semester and Year

2019

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry

Department

Chemistry and Biochemistry

First Advisor

Sandy Dasgupta

Second Advisor

Peter Kroll

Abstract

In the field of materials discovery, the appearance of Polymer Derived Ceramics (PDC’s) over 30 years ago represents a breakthrough in materials science and development. The PDC route represents significant advantages in ceramic science and technology. This route enables synthesis of bulk ceramics, fibers, porous ceramics and coating materials that are stable at temperatures up to 2000 oC. PDCs can be separated into binary and ternary systems. Examples of binary systems are silicon carbide (SiC) and silicon nitride (Si3N4 ). Ternary systems include silicon carbonitride (SiCN) and silicon oxycarbide (SiCO). One very important feature of PDCs is their crystallization resistance. For example, silica (SiO2) crystallizes into cristobalite while the SiCO system remains amorphous. Recent insight into the micro and nanostructural features of these materials has provided understanding of the properties of these materials and their applications. The development and applicability of PDC materials is interdisciplinary requiring expertise from physicists, chemists, material scientists, engineers, and mineralogists. In this work, we focus our investigation into the ternary system SiCO. Our objective is to contribute to the field of PDC materials by investigating microstructural, physical and chemical properties of these materials. First, we present the synthesis and characterization of SiCO aerogels and provide insight into the importance of solubility parameters in the microstructural features of these materials. We synthesized SiCO aerogels and reported the importance of polymer solubility and swelling in the microstructural features of these materials. Then, we present the synthesis of ambient dried SiCO ceramics and characterized their microstructural features as well as the adsorption efficiency. We compared the adsorption efficiency of porous SiCO to mesoporous silica and activated carbon. Porous SiCO had outstanding adsorption ability towards methylene blue (MB) and results indicated that highest Specific Surface Area (SSA) is not the most important characteristic in the adsorption of dyes in these materials. To investigate more closely the polymer to ceramic conversion of these SiCO materials, ambient-dried SiCO were annealed in inert atmosphere starting from 400 °C up to 1000 °C. Nitrogen adsorption analysis along with FE-SEM imaging suggest that pore development as well as particle shrinkage of SiCO play a role in the microstructural properties of sol-gel derived SiCO ceramics. Last, to investigate high temperature behavior of SiCO PDC ceramics, we synthesize carbon-rich SiCO bulk ceramics when annealed up to 1500 °C. We obtained information about the phase separation of SiCO ceramics, the increase of SiC crystalline growth and the presence of small and decreasing graphite peaks with increasing annealing temperature. XRD and Raman analysis show increased arrangement of the free carbon phase present in these SiCO ceramics.

Keywords

Silicon oxycarbide, Aerogels

Disciplines

Chemistry | Physical Sciences and Mathematics

Comments

Degree granted by The University of Texas at Arlington

Included in

Chemistry Commons

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