Crystallization of grain boundary phases in silicon nitride with low additive contents by microwave annealing

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Microwave annealing of dense Si{sub 3}N{sub 4}-4% Y{sub 2}O{sub 3} materials showed improvements over conventional heating. Increases in fracture toughness were observed for annealing between 1200--1650C. The high temperature strength was related to the residual {alpha}-Si{sub 3}N{sub 4} content which is indicative of a finer average grain size in the specimens. The high temperature dynamic fatigue showed increased stress to failure for specimens microwave annealed between 1400--1550C for periods >5 h. Silicon nitrides with different sintering additives would require different conditions for optimum crystallization. While there were some observed property improvements, they were not so dramatic to justify abandoning conventional ... continued below

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11 p.

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Tiegs, T. N.; Ploetz, K. L.; Kiggans, J. O. & Yeckley, R. L. June 1, 1993.

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Microwave annealing of dense Si{sub 3}N{sub 4}-4% Y{sub 2}O{sub 3} materials showed improvements over conventional heating. Increases in fracture toughness were observed for annealing between 1200--1650C. The high temperature strength was related to the residual {alpha}-Si{sub 3}N{sub 4} content which is indicative of a finer average grain size in the specimens. The high temperature dynamic fatigue showed increased stress to failure for specimens microwave annealed between 1400--1550C for periods >5 h. Silicon nitrides with different sintering additives would require different conditions for optimum crystallization. While there were some observed property improvements, they were not so dramatic to justify abandoning conventional over microwave heating. The Si{sub 3}N{sub 4}-4% Y{sub 2}O{sub 3} materials used in the study were developed for elevated temperature use and already posses excellent good high temperature strength, fatigue resistance and creep properties. This is due to the very refractory nature of the grain boundary phases and the small quantity of secondary phase present. However, microwave annealing of these materials may be necessary in applications where the maximum in fracture toughness and fatigue resistance are required and thus justifies its use.

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11 p.

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OSTI; NTIS; GPO Dep.

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  • 95. annual meeting of the American Ceramic Society,Cincinnati, OH (United States),18-22 Apr 1993

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  • Other: DE93015801
  • Report No.: CONF-930438--24
  • Grant Number: AC05-84OR21400
  • Office of Scientific & Technical Information Report Number: 10162794
  • Archival Resource Key: ark:/67531/metadc1387317

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  • June 1, 1993

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  • Nov. 28, 2018, 2:33 p.m.

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  • Dec. 12, 2018, 3:03 p.m.

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Tiegs, T. N.; Ploetz, K. L.; Kiggans, J. O. & Yeckley, R. L. Crystallization of grain boundary phases in silicon nitride with low additive contents by microwave annealing, article, June 1, 1993; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc1387317/: accessed March 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.