Cracking during pyrolysis of preceramic polymers within glass microtubes

Journal Article · 19 January 2022 · Journal of the American Ceramic Society

DOI: https://doi.org/10.1111/jace.18326 · OSTI ID:1841296

Larson, Natalie M.  ^[1]; Summers, William D.  ^[2]; Zok, Frank W.  ^[2]

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1. Materials Department University of California Santa Barbara California USA, Lawrence Berkeley National Laboratory Berkeley California USA
2. Materials Department University of California Santa Barbara California USA

Abstract Cracking of preceramic polymers during pyrolysis under highly‐constrained conditions is examined by X‐ray computed tomography of fine glass microtubes containing the pyrolyzing material. The microtubes represent model geometries that mimic the long channels between fibers during production of ceramic composites by precursor impregnation and pyrolysis. Complementary fracture mechanics analyses of interface cracking and crack kinking are used to glean insights into the conditions under which periodic alternating cracks form. A key finding is that alternating cracks are an inherent feature of constrained pyrolysis . This feature is attributable in large part to the high energy release rates for interface cracks to kink into the pyrolyzing material under the hydrostatic tension developed during pyrolysis. It also requires interfaces with toughness comparable to that of the pyrolyzing material, to prevent large‐scale interface separation. The results further indicate the need for small uniform spaces for pyrolysis within fiber preforms in order to produce networks of fine periodic pyrolysis cracks; these networks in turn facilitate impregnation and pyrolysis in subsequent processing cycles.

• Sponsoring Organization: USDOE
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1841296
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 5 Vol. 105; ISSN 0002-7820
• Publisher: Wiley-BlackwellCopyright Statement
• Country of Publication: United States
• Language: English