University of Connecticut OpenCommons@UConn Doctoral Dissertations University of Connecticut Graduate School 8-26-2014 Development of New Matrix and Interfacial Materials for Ceramic Matrix Composites Gavin C. Richards University of Connecticut - Storrs, [email protected] Follow this and additional works at: https://opencommons.uconn.edu/dissertations Recommended Citation Richards, Gavin C., "Development of New Matrix and Interfacial Materials for Ceramic Matrix Composites" (2014). Doctoral Dissertations. 522. https://opencommons.uconn.edu/dissertations/522 Development of New Matrix and Interfacial Materials for Ceramic Matrix Composites Gavin C. Richards, PhD University of Connecticut, 2014 Pre-ceramic polymers are attractive, low cost materials for the manufacture of ceramic fibers and matrix materials in Ceramic Matrix Composites (CMCs). A new pre-ceramic polymer, an ethanol-modified polyvinylsilazane (PVSZ), was synthesized and characterized. The PVSZ polymer has been previously shown to be a viable precursor for silicon nitride and silicon carbide based ceramics, but lacked stability when exposed to air. The PVSZ polymer was synthesized via the ammonolysis of trichlorovinylsilazane in tetrahydrofuran (THF), and then reacted with ethanol to form the ethanol-modified PVSZ. The PVSZ polymer and ethanol- modified PVSZ resin were each characterized with Attenuated Total Reflectance spectroscopy (ATR), 1H Nuclear Magnetic Resonance ( 1H-NMR), and Gel Permeation Chromatography (GPC), Thermogravimetric Analysis (TGA), Residual Gas Analysis (RGA), and X-Ray Powder Diffraction (XRD) of the ceramic char after pyrolysis in various atmospheres. A second new modified PVSZ was also synthesized. Rather than use ethanol, a second silane monomer was added during synthesis, with the intent of stabilizing the polymer without incorporating oxygen. The new end cap modified PVSZ (EC-PVSZ) was characterized using the same methods outlined for the ethanol-modified PVSZ. Both modified systems demonstrated improved shelf-life. Chemical Vapor Deposition (CVD) was employed to deposit ZnO/SiO 2 interfacial coatings onto Nextel-440™ fabric. A new low pressure CVD (LP-CVD) furnace was designed I Gavin C. Richards – University of Connecticut, 2014 to deposit SiO 2 under reduced pressure. The effects of temperature, precursor amounts, and coating thicknesses were examined to optimize the mechanical strength of the coated fabric. Tensile testing of the fibers was used to evaluate the impact of the coating processes on the fabric’s strength. Coated fabric was evaluated by X-Ray Diffraction, Scanning Auger Microscopy (SAM), and Scanning Electron Microscopy (SEM). II Development of New Matrix and Interfacial Materials for Ceramic Matrix Composites Gavin C. Richards B.S., Binghamton University, 2008 A Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy at the University of Connecticut 2014 III Copyright by Gavin C. Richards 2014 IV APPROVAL PAGE Doctor of Philosophy Dissertation Development of New Matrix and Interfacial Materials for Ceramic Matrix Composites Presented by Gavin C. Richards Major Advisor _____________________________________ Steven L. Suib Associate Advisor ______________________________________ Christian Brückner Associate Advisor ______________________________________ Nicholas E. Leadbeater Associate Advisor ______________________________________ Edward J. Neth Associate Advisor ______________________________________ Mark W. Peczuh University of Connecticut 2014 V Dedicated to my Mother and Father VI Acknowledgements I would like to thank my major advisor, Dr. Steven L. Suib, for his support and guidance over the years. As I have grown as a graduate student, I now understand the importance of many of the lessons he taught early on. I extend my gratitude to Dr. Michael A. Kmetz, for giving me the push that I sometimes required. His experimental and philosophical approaches to problems will be dutifully remembered. I would also like to thank my committee members, Dr. Christian Brückner, Dr. Nicholas Leadbeater, Dr. Edward Neth, and Dr. Mark Peczuh. I would like to give special acknowledgement to Dr. Justin Reutenauer, a lab member who was both mentor and friend for the majority of my career at UConn. I would also like to thank my fellow graduate students Dr. Timothy Coons, Samuel Frueh, Rebecca Gottlieb, and Shannon Poges for their assistance with this research. I would also recognize my two undergraduate researchers, Christopher Monteleone and Kenneth Petroski, for both their assistance with research, and for keeping the lab a lively place. Lastly, I would like to thank my family and friends. Without their continued support, none of this would have been possible. VII TABLE OF CONTENTS Chapter 1 Introduction ………………………………………………………………...………01 1.1 Ceramic Matrix Composites (CMCs)..………………………………………………………01 1.2 Reinforcing Materials………………………………………………………………………..01 1.3 Interfaces…………………………………………………………………………………….05 1.4 Chemical Vapor Deposition (CVD)…………………………………………………………09 1.5 Matrix………………………………………………………………………………………...11 1.6 Chemical Vapor Infiltration (CVI)…………………………………………………………..12 1.7 Polymer Impregnation and Pyrolysis (PIP)………………………………………………….12 1.8 Pre-Ceramic Polymers……………………………………………………………………….14 1.9 Composite Testing…………………………………………………………………………...18 Chapter 2 Resin System Prepared via Ethanol Additions to Polyvinylsilazane……………22 2.1 Polysilazanes…………………………………………………………………………………22 2.2 Experimental…………………………………………………………………………………23 2.2.1 PVSZ Synthesis……………………………………………………………………23 2.2.2 Alcohol Additions…………………………………………………………………25 2.2.3 Solid Monolith Formation…………………………………………………………26 2.2.4 Silver Nitrate Additions………………………………….………………………..26 2.3 Characterization………………………………………………………………………...……27 2.4 Results………………………………………………………………………………………..28 2.4.1 Ethanol Additions………………………………………………………………….28 2.4.2 Attenuated Total Reflectance Spectroscopy……………………………………….28 2.4.3 Nuclear Magnetic Resonance……………………………………………………...29 2.4.4 Gel Permeation Chromatography………………………………………………….31 2.4.5 Viscosity………………………………………………………………………...…31 VIII 2.4.6 Residual Gas Analysis……………………………………………………………..31 2.4.7 Chlorine Detection………………………………………………………………....33 2.4.8 Thermo-Gravimetric Analysis……………………………………………………..34 2.4.9 X-Ray Diffraction……………………………………………………...…………..35 2.5 Discussion……………………………………………………………………………………39 2.6 Conclusions…………………………………………………………………………………..42 Chapter 3 Deposition and Characterization of a ZnO / SiO 2 Duplex Interfacial Coating on Oxide Fiber ……………………………………………………………………………………...44 3.1 Oxide Interfaces……………………………………………………………………………...44 3.2 Experimental…………………………………………………………………………………45 3.3 Characterization……………………………………………………………………………...48 3.4 Results………………………………………………………………………………………..48 3.4.1 X-Ray Diffraction………………………………………………………………….48 3.4.2 Scanning Auger Microscopy……………………………………………………….50 3.4.3 Scanning Electron Microscopy…………………………………………………….51 3.4.4 Effect of Precursor Mass on Coating Thickness…………………………………...53 3.4.5 Effect of Deposition Time on Coating Thickness………………………………….54 3.4.6 Tensile Testing……………………………………………………………………..54 3.5 Discussion……………………………………………………………………………………55 3.6 Conclusions…………………………………………………………………………………..57 Chapter 4 Synthesis and Characterization of an End-Capped Polyvinylsilazane………….58 4.1 Polysilazanes Continued……………………………………………………………………..58 4.2 Experimental…………………………………………………………………………………59 4.2.1 End-Capped Polyvinylsilazane Synthesis………………………………………….59 4.2.2 Stability Study……………………………………………………………………...61 IX 4.3 Characterization……………………………………………………………………………...61 4.4 Results………………………………………………………………………………………..62 4.4.1 Stability Study……………………………………………………………………...62 4.4.2 Attenuated Total Reflectance Spectroscopy……………………………………….63 4.4.3 Gel Permeation Chromatography………………………………………………….64 4.4.4 Residual Gas Analysis……………………………………………………………..65 4.4.5 Thermo-Gravimetric Analysis………………….……………………………...…..66 4.4.6 X-Ray Diffraction……………………………………………………...…………..70 4.5 Discussion……………………………………………………………………………………74 4.6 Conclusions…………………………………………………………………………………..76 Chapter 5 Conclusions and Future Work ……………………………………..……………...77 5.1 Conclusions…………………………………………………………………………………..77 5.2 Future Work………………………………………………………………………………….78 References ……………………………………………………………………………………….80 X LIST OF FIGURES Figure 1.1 Composite exhibiting catastrophic brittle failure…………………………………….06 Figure 1.2 Composite exhibiting fiber pullout and crack bridging………………………………07 Figure 1.3 Fabrication of a CMC via polymer impregnation and pyrolysis……………………..13 Figure 1.4 Synthesis of a polysilane via the Wurtz reaction…………….……………………….15 Figure 1.5 Kumada rearrangement of a polycarbosilane………………………………………...15 Figure 1.6 Ammonolysis of a dichlorosilane…………………………………………………….16 Figure 1.7 Cross-linking of polysilazanes……………………………………………………….17 Figure 1.8 Aminolysis of a dichlorosilane……………………………………………………….17 Figure 1.9 Hydrazinolysis of a dichlorosilane…………………………………………………...18 Figure 1.10 Tow mount for Instron ® testing……………………………………………………..19 Figure 1.11 Tensile strength of Nextel-440™ fabric…………………………………………….20 Figure 1.12 Three point bend test apparatus and necessary dimensions………………………...21 Figure 2.1 Ammonolysis of vinyltrichlorosilane………………………………………………...24 Figure 2.2 Diagram of reactor vessel used to synthesize polyvinylsilazane……………………..25 Figure 2.3 Setup to monitor chlorine evolution from PVSZ…………………………………….27 Figure 2.4 ATR spectra of PVSZ, PVSZ with 15 wt% EtOH, and PVSZ with 50 wt% EtOH….29 Figure