6. Grain Boundary Chemistry of SiC-Based Armor

  1. Lisa Prokurat,
  2. Andrew Wereszczak and
  3. Edgar Lara-Curzio
  1. Edgardo Pabit1,
  2. Kerry Siebein1,
  3. Darryl P. Butt1,
  4. Helge Heinrich2,
  5. Darin Ray3,
  6. Sarbjit Kaur3,
  7. R. Marc Flinders3 and
  8. Raymond A. Cutler3

Published Online: 26 MAR 2008

DOI: 10.1002/9780470291368.ch6

Advances in Ceramic Armor II: Ceramic Engineering and Science Proceedings, Volume 27, Issue 7

Advances in Ceramic Armor II: Ceramic Engineering and Science Proceedings, Volume 27, Issue 7

How to Cite

Pabit, E., Siebein, K., Butt, D. P., Heinrich, H., Ray, D., Kaur, S., Flinders, R. M. and Cutler, R. A. (2008) Grain Boundary Chemistry of SiC-Based Armor, in Advances in Ceramic Armor II: Ceramic Engineering and Science Proceedings, Volume 27, Issue 7 (eds L. Prokurat, A. Wereszczak and E. Lara-Curzio), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470291368.ch6

Author Information

  1. 1

    University of Florida Materials Science and Engineering Department Gainesville, Florida 32611

  2. 2

    University of Central Florida AMPAC Orlando, Florida 32816

  3. 3

    Ceramatec, Inc. 2425 South 900 West Salt Lake City, Utah 84119

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 2006

ISBN Information

Print ISBN: 9780470080573

Online ISBN: 9780470291368

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Keywords:

  • precracked beam;
  • electron microscopy;
  • grain boundary;
  • aluminum-containing samples;
  • chemistry

Summary

Fourteen SiC-based materials were processed by hot pressing. The single-edge precracked beam (SEPB) fracture toughness varied from 2.4 to 6.8 MPa-m1/2 and fracture modes changed from transgranular to intergranular. Grain boundaries and triple points were analyzed using high-resolution transmission electron microscopy combined with energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS) using an energy-filtered approach. The objective of this study was to compare the grain boundary chemistry of these materials and determine how it affected fracture mode.

In all samples containing Al, AlN or Al2O3, oxygen was associated with aluminum at the grain boundaries. Chemical analysis of the hot pressed bulk material showed that O levels ranged between 0.3 and 1.1 wt. %, whereas N levels were as high as 1.5 %. In all of the aluminum-containing samples, the Al and O concentrated at triple points and penetrated along most grain boundaries regardless of the fracture mode. Nitrogen in the AIN-doped samples was difficult to detect by EDS or EELS at 2200°C, suggesting that it diffused into the 4H or 6H polytypes during sintering. Likewise, it was generally difficult to detect the O or Al in solid solution within the SiC grains.

Simultaneous boron and carbon additions lowered the fracture toughness when either Al or A1N were used at the same cation content. Triple point and grain boundary chemistries, however, were similar to those where no B and C were added. This was primarily due to the enhanced early densification, which resulted in higher amounts of O and N in these compositions. Quantitative fracture mode did not correlate with grain size and grain boundary chemistry, as had been expected.