ChemInform Abstract: Hot Pressing of Silicon Nitride with Mixed Rare-Earth Oxide Additives

Fracture toughness of hot-pressed silicon nitride and Si3N4+SiC nanocomposites prepared with different rare-earth oxides (La2O3, Sm2O3, Y2O3, Yb2O3, Lu2O3) sintering additives have been investigated by Chevron Notched Beam, Indentation Strength and Indentation Fracture techniques. The fracture toughness values of composites were lower due to the finer microstructures and the lack of toughening mechanisms. In the Si3N4 with higher aspect ratio (Lu or Yb additives) crack deflection occurred more frequently compared to the Si3N4 doped with La or Y, which was responsible for the higher fracture toughness.

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Fabrication and Properties of Si3N4 with Rare Earth Apatite Grain Boundary Phases

MRS Proceedings ◽

10.1557/proc-287-353 ◽

1992 ◽

Vol 287 ◽

Cited By ~ 1

Author(s):

Terry N. Tiegs ◽

Stephen D. Nunn ◽

Kristin L. Ploetz ◽

Paul A. Menchoffer ◽

Claudia A. Walls

Keyword(s):

Rare Earth ◽

Silicon Nitride ◽

Grain Boundary ◽

Ambient Temperature ◽

Rare Earth Oxide ◽

High Toughness ◽

The Rare Earth

ABSTRACTThe rare earth-oxide and nitride apatites were examined as grain boundary phases in silicon nitride to assess their potential for developing high toughness materials using gas-pressuresintering. Densification was dependent on the quantity of additives used with high densities achieved at equivalent oxygen contents of ∼8%. Fracture toughnesses (KIc) up to 8-10 MPa√m were obtained for some compositions. Ambient temperature flexural strengths were in the range of 400-720 MPa; however, the strengths atelevated temperatures (1200ºC) were reduced from these values.

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ChemInform Abstract: OXIDATION OF SILICON NITRIDE SINTERED WITH RARE EARTH OXIDE ADDITIONS

Chemischer Informationsdienst ◽

10.1002/chin.198544030 ◽

1985 ◽

Vol 16 (44) ◽

Author(s):

D. M. MIESKOWSKI ◽

W. A. SANDERS

Keyword(s):

Rare Earth ◽

Silicon Nitride ◽

Rare Earth Oxide

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Influence of various rare-earth oxide additives on microstructure and mechanical properties of silicon nitride based nanocomposites

Materials Science and Engineering A ◽

10.1016/j.msea.2010.04.069 ◽

2010 ◽

Vol 527 (18-19) ◽

pp. 4771-4778 ◽

Cited By ~ 26

Author(s):

Peter Tatarko ◽

Štefánia Lojanová ◽

Ján Dusza ◽

Pavol Šajgalík

Keyword(s):

Mechanical Properties ◽

Rare Earth ◽

Silicon Nitride ◽

Rare Earth Oxide ◽

Microstructure And Mechanical Properties

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Characterization of rare-earth doped Si3N4/SiC micro/nanocomposites

Processing and Application of Ceramics ◽

10.2298/pac1001025t ◽

2010 ◽

Vol 4 (1) ◽

pp. 25-32 ◽

Cited By ~ 6

Author(s):

Peter Tatarko ◽

Stefánia Lojanová ◽

Ján Dusza ◽

Pavol Sajgalík

Keyword(s):

Fracture Toughness ◽

Rare Earth ◽

Silicon Nitride ◽

Rare Earth Elements ◽

Ionic Radius ◽

Bending Strength ◽

Rare Earth Oxide ◽

Positive Influence ◽

The Matrix

Influence of various rare-earth oxide additives (La2O3, Nd2O3, Sm2O3, Y2O3, Yb2O3 and Lu2O3) on the mechanical properties of hot-pressed silicon nitride and silicon nitride/silicon carbide micro/nano-composites has been investigated. The bimodal character of microstructures was observed in all studied materials where elongated ?-Si3N4 grains were embedded in the matrix of much finer Si3N4 grains. The fracture toughness values increased with decreasing ionic radius of rare-earth elements. The fracture toughness of composites was always lower than that of monoliths due to their finer Si3N4/SiC microstructures. Similarly, the hardness and bending strength values increased with decreasing ionic radius of rare-earth elements either in monoliths or composites. On the other hand, the positive influence of finer microstructure of the composites on strength was not observed due to the present defects in the form of SiC clusters and non-reacted carbon zones. Wear resistance at room temperature also increased with decreasing ionic radius of rare-earth element. Significantly improved creep resistance was observed in case either of composite materials or materials with smaller radius of RE3+. .

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