Polymer Derived Nitride CMCs for Advanced High-Temperature Wave-Transparent Applications

Significance 

For high-temperature applications, ceramic matrix composites containing a continuous ceramic fiber fabric wave-transparent material have been seen to be quite promising. For their reinforcement, quartz fiber is so far the most common material owing to its exemplary thermal shock resistance and dielectric properties. However, it encounters a critical drawback in terms of undergoing crystallization at temperatures above 1100 °C which leads to severe strength degradation. Fortunately, recent technological advances have led to the development of aluminosilicate fibers such as Nextel™ 440, which possess desirable dielectric, mechanical, thermal properties, high structural stability and strength retention at relatively high temperatures. Composites composed of aluminosilicate fibers and nitride matrix have been hypothesized to be adequate to overcome the limits of silica fiber reinforced ceramic matrix composites. Unfortunately, little has been done to verify and ascertain this hypothesis into a fact with regard to the desirable attributes enlisted earlier.

To this note, scientists at National University of Defense Technology led by Professor Bin Li and Dr Duan Li from the Science and Technology on Advanced Ceramic Fibers and Composites Laboratory investigated the properties of Nextel™ 440 fiber reinforced nitride matrix (N440/Nitride) composites. They used the precursor infiltration and pyrolysis route to fabricate the reinforced matrix nitride composites. Their work is currently published in the research journal, Ceramics International.

The research team looked in details on the structure, composition and mechanical strength of the Nextel™ 440 fiber. Next, they fabricated the N440/ Nitride composites using the precursor infiltration and pyrolysis route. Lastly, they systematically evaluated the mechanical, thermophysical and dielectric properties of the fabricated composites using various techniques.

The authors observed that original N440 fiber had a tensile strength retention rate of 35.1% at 1400 °C. Following various tests, they noted that the flexural strength of the N440/Nitride composites could achieve 76.0 MPa at room temperature thereby indicating a good fiber/matrix interface and toughness. Further investigations showed that even after heating to 1400 °C, the composites still possessed up to 67.4% of original flexural strength. It was also seen that the elevated temperatures caused strong fiber matrix connection and severe fiber degradation.

In a nutshell, Dr Duan Li, Professor Bin Li and colleagues study successfully presented the fabrication and rigorous testing of the Nextel™ 440 fiber reinforced nitride matrix (N440/Nitride) composites. In general, it was seen that the fabricated composite possessed an overall good performance with regard to thermal conductivity, specific heat, mechanical strength and overall structural stability. Regardless, it is still important to note that further improvement can be conducted by adjusting the porosity of the composites to acquire a lower ε and tan δ with balanced mechanical properties. Altogether, the excellent overall performance could enable the N440/Nitride composites utilization in advancing high-temperature wave-transparent applications.

Polymer Derived Nitride CMCs for Advanced High-Temperature Wave-Transparent Applications - Advanced Engineering

About the author

Prof Bin Li received the BE and the PhD degrees from National University of Defense Technology (NUDT), Changsha, China, in 2003 and 2007, respectively, in both materials science and engineering. From 2007, he has been working at the State Key Laboratory of Advanced Ceramic Fibers and Composites, NUDT. He is a Member of the Institute of Physics (MInstP) and a Member of IEEE.

He holds a visiting scientist position at the Department of Materials Science and Metallurgy, University of Cambridge, and a visiting fellowship at the Wolfson College, University of Cambridge. He has coauthored more than 100 peer-reviewed papers.

His research group focuses on element organic monomers, polymers, and polymer derived ceramics; ceramic films and ceramic matrix composites; thermal protection materials and ultrahigh temperature ceramics; and crystallography and molecular dynamics.

Email: [email protected]

About the author

Dr Duan Li received the BS and the MS degrees from the NUDT, in 2009 and 2011, respectively. In 2012 he was fully funded by a Marie Curie project and started his PhD study (2012-2016) in Materials Science in Stockholms Universitet, Sweden. From 2016 he moved to Changsha and worked as a lecturer at the State Key Laboratory of Advanced Ceramic Fibers and Composites, NUDT. He has authored/co-authored more than 30 papers in international refereed journals. His current research interests include polymer derived ceramics (PDCs) & composites, nitride/oxynitride ceramics, as well as advanced sintering techniques.

Email: [email protected]

Reference

Duan Li, Bin Li*, Yuanyi Zheng, Shitao Gao, Xuejin Yang. On the mechanical, thermophysical and dielectric properties of Nextel™ 440 fiber reinforced nitride matrix (N440/Nitride) composites. Ceramics International, volume 44 (2018) page 6137–6143.

Go To Ceramics International

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