Session: Research Posters

Paper Number: 114122

114122 - Assessing the High-Temperature Suitability of Sic Fiber-Reinforced Quaternary Ceramic Matrix Composites 

Ceramic matrix composites (CMCs) are suitable candidates for aerospace and aircraft components due to the composites’ lightweight structure, high mechanical strength, and high-temperature stability. Compared to the more traditionally used polymer matrix composite, CMCs have shown much higher mechanical stability and strength at high temperatures. This is mainly due to the presence of nanodomains in the ceramic microstructure. These nanodomains are a few nanometers in length and allow for the ceramic material to remain amorphous at high temperatures (1000 – 1800 °C) with little to no crystallization. CMCs have also shown higher oxidation resistance, due to the formation of an oxide layer on the ceramic interface. In the case of precursor-derived ceramics (PDCs), the oxidation resistance increases with the amount of free carbon in the nanostructure, which is parabolically related. In this context, Si-based PDCs have processing flexibility that allows to achieve desired shape and control of the final ceramic product. PDCs have shown high resistance to various loads, deformation, and creep. In this study, SiCN/SiC, Si(B)CN/SiC, and Si(Hf)CN/SiC CMC mini-composites were fabricated with SiC fiber reinforcement using polysilazane-based single-source liquid precursors. The samples used for mechanical testing were fabricated using individual bundles of non-woven SiC fibers. All fibers were positioned in the same direction and each sample was cut to 4 cm in length. Samples used for oxidation testing, on the other hand, were circular in shape and woven in a perpendicular, 90° fiber orientation. A polysilazane-based precursor was mixed with boron and hafnium-containing precursors to synthesize Si(B)CN and Si(Hf)CN polymeric precursors.  The homogenous solutions of the precursors were then allowed to infiltrate the fibers via a drop-coating process. The coated Fibers were cross-linked at 180 °C for 16 h and later pyrolyzed at 800 °C for 30 min in an inert atmosphere to achieve CMC mini-composites. The crosslinked precursor to ceramic yield was observed to be as high as 90% when the procedure was carried out in an inert environment. The fabricated composites then underwent various characterization techniques including SEM for surface morphology observation, XPS for surface composition analysis, FTIR and Raman Spectroscopy for molecular structure characterization. The Si(B)CN/SiC contained Si-N and B-N bonds, while Si-N and Hf-O-Si bonds were observed for the Si(Hf)CN/SiC sample with uniform and dense surfaces. An oxidation study of the Si(Hf)CN/SiC mini-composites showed higher stability compared to SiCN/SiC and
Si(B)CN/SiC mini-composites up to 1500 °C. Structural and compositional changes of the oxidized samples were also investigated via XPS and SEM analyses.

Presenting Author: Mohammed Rasheed Kansas State University

Presenting Author Biography: Mohammed is an undergraduate researcher in the Mechanical and Nuclear Engineering department of Kansas State University.

Authors:

Shakir Bin Mujib Kansas State University
Mohammed Rasheed Kansas State University
Gurpreet Singh Kansas State University