Thickness Alteration of Grain-Boundary Amorphous Films during Creep of a Multiphase Silicon Nitride Ceramic

Sodium ion-conductive silicon nitride ceramic with Na2O–Al2O3–SiO2 glass as the grain boundary phase was fabricated by adding Na2CO3, Al2O3, and SiO2 as sintering additives. The electrical conductivity was two and four orders of magnitude higher than that of Si3N4 ceramic with Y2O3 and Al2O3 additives at 100 and 1000°C, respectively. This result clearly indicates that ionic conductivity can be provided to insulating structural ceramics by modification of the grain boundary phase without dispersion of conductive particles.

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On the Effect of Local Grain-Boundary Chemistry on the Macroscopic Mechanical Properties of a High-Purity Y2O3-Al2O3-Containing Silicon Nitride Ceramic: Role of Oxygen

Journal of the American Ceramic Society ◽

10.1111/j.1551-2916.2005.00412.x ◽

2005 ◽

Vol 88 (7) ◽

pp. 1900-1908 ◽

Cited By ~ 11

Author(s):

A. Ziegler ◽

J. M. McNaney ◽

M. J. Hoffmann ◽

R. O. Ritchie

Keyword(s):

Mechanical Properties ◽

Silicon Nitride ◽

Grain Boundary ◽

High Purity ◽

Silicon Nitride Ceramic ◽

Boundary Chemistry

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Examination of Fracture Interfaces in Silicon Nitride

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113925 ◽

1975 ◽

Vol 33 ◽

pp. 60-61

Author(s):

Nancy J. Tighe

Keyword(s):

Silicon Nitride ◽

Grain Boundary ◽

Crack Growth ◽

Subcritical Crack Growth ◽

Slow Crack Growth ◽

Ceramic Materials ◽

Grain Boundary Sliding ◽

Boundary Phase ◽

Turbine Engines ◽

Boundary Sliding

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

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Phase Relationship Studies of Silicon Nitride System—A Key to Materials Design

MRS Proceedings ◽

10.1557/proc-287-39 ◽

1992 ◽

Vol 287 ◽

Cited By ~ 2

Author(s):

T.S. Yen ◽

W.Y. Sun

Keyword(s):

Elevated Temperature ◽

Silicon Nitride ◽

Grain Boundary ◽

Phase Behavior ◽

Phase Diagrams ◽

Room Temperature ◽

Phase Relationship ◽

Materials Design ◽

Basic Approach ◽

System A

ABSTRACTAdditions and revisions to several of the most important phase diagrams and phase behavior diagrams in the silicon nitride field are reviewed in this work, with emphasis on the Y-Si-A1-O-N system. This information is further used to make observations on the promising silicon nitride systems containing either highly refractory grain boundary phases or compatible matrix phases of desirable properties. Examples are provided to illustrate the advantage of such a basic approach to materials design. Hardness, toughness, strength at room temperature and elevated temperature and even sinterability can all be improved by adopting such an approach.

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Experiment on Foreign Object Damage of Gas Turbine-Grade Silicon Nitride Ceramic

Volume 2: Aircraft Engine; Marine; Microturbines and Small Turbomachinery ◽

10.1115/98-gt-399 ◽

1998 ◽

Cited By ~ 3

Author(s):

Hiro Yoshida ◽

Takashi Nakashima ◽

Makoto Yoshida ◽

Yasushi Hara ◽

Toru Shimamori

Keyword(s):

Elevated Temperature ◽

Silicon Nitride ◽

Elevated Temperatures ◽

Tensile Load ◽

Strength Degradation ◽

Spall Fracture ◽

Silicon Nitride Ceramic ◽

Impact Tests ◽

The Impact ◽

Bending Fracture

A new high quality turbine system using monolithic silicon-nitride ceramic is under development. In this study particle impact tests of the silicon-nitride have been tried at room and elevated temperatures with and without tensile load, which simulates centrifugal force of blade rotation. In the experiment 1 mm diameter particle is impacted at velocities up to 900 m s−1. In this paper, critical velocities for bending fracture and Hertzian cracks are examined. Moreover, strength degradation at elevated temperature and spall fracture of the blade are discussed. The main results are: 1) The bending fracture mode critical impact velocity for soft particles is higher than that for hard particles. 2)The impact parameter ϕ for initiation of Hertzian cracks ranges 1.08×10−5 – 1.56×10−5 for the materials tested. 3)Strength degradation at elevated temperature was clearly observed. 4) In the impact tests on blades spall fracture, which was caused by interaction of stress waves, appeared.

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