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