Microstructural design of silicon nitride with improved fracture toughness: I, Effects of grain shape and size
| Autor: | Eul-Son Kang, Ellen Y. Sun, Chun-Hway Hsueh, Kevin P. Plucknett, Shirley B. Waters, C. Gary Westmoreland, Paul F. Becher, Manuel E. Brito, Hua-Tay Lin, Kiyoshi Hirao, K. B. Alexander |
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| Zdroj: | Scopus-Elsevier ResearcherID |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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