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This content will become publicly available on October 31, 2018

Title: In-situ 3D visualization of composite microstructure during polymer-to-ceramic conversion

One route for producing fiber-reinforced ceramic-matrix composites entails repeated impregnation and pyrolysis of a preceramic polymer in a fiber preform. The process relies crucially on the development of networks of contiguous cracks during pyrolysis, thereby allowing further impregnation to attain nearly-full densification. The present study employs in-situ x-ray computed tomography (XCT) to reveal in three dimensions the evolution of matrix structure during pyrolysis of a SiC-based preceramic polymer to 1200 °C. Observations are used to guide the development of a taxonomy of crack geometries and crack structures and to identify the temporal sequence of their formation. A quantitative analysis is employed to characterize effects of local microstructural dimensions on the conditions required to form cracks of various types. Complementary measurements of gas evolution and mass loss of the preceramic polymer during pyrolysis as well as changes in mass density and Young's modulus provide context for the physical changes revealed by XCT. Furthermore, the findings provide a foundation for future development of physics-based models to guide composite fabrication processes.
Authors:
ORCiD logo [1] ; ORCiD logo [1]
  1. Univ. of California, Santa Barbara, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 144; Journal Issue: C; Journal ID: ISSN 1359-6454
Publisher:
Elsevier
Research Org:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). Advanced Light Source
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; X-ray computed tomography (XCT); Polymer derived ceramic (PDC); Ceramic matrix composite (CMC); Precursor impregnation and pyrolysis (PIP); Preceramic polymer
OSTI Identifier:
1409336