Microstructural design of silicon nitride with improved fracture toughness. 1: Effects of grain shape and size

Journal Article · Sun Nov 01 04:00:00 EST 1998 · Journal of the American Ceramic Society

DOI:https://doi.org/10.1111/j.1151-2916.1998.tb02702.x· OSTI ID:289482

Becher, P F; Sun, E Y; Plucknett, K P ^[1]

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1. Oak Ridge National Lab., TN (United States); and others

The use of self-reinforcement by larger elongated grains in silicon nitride ceramics requires judicious control of the microstructure to achieve high steady-state toughness and high fracture strength. With a distinct bimodal distribution of grain diameters, such as that achieved by the addition of 2% rodlike seeds, the fracture resistance rapidly rises with crack extension to steady-state values of up to 10 MPa{center_dot}m{sup 1/2} and is accompanied by fracture strengths in excess of 1 GPa. When the generation of elongated reinforcing grains is not regulated, a broad grain diameter distribution is typically generated. While some toughening is achieved, both the plateau (steady-state) toughness and the R-curve response suffer, and the fracture strength undergoes a substantial reduction. Unreinforced equiaxed silicon nitride exhibits the least R-curve response with a steady-state toughness of only 3.5 MPa{center_dot}m{sup 1/2} coupled with a reduced fracture strength.

• Sponsoring Organization: USDOE
• OSTI ID: 289482
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 11 Vol. 81; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
EXPERIMENTAL DATA
FRACTOGRAPHY
FRACTURE MECHANICS
FRACTURE PROPERTIES
MICROSTRUCTURE
PARTICLE SIZE
POWDERS
SHAPE
SILICON NITRIDES