Cavitation Creep in the Next Generation Silicon Nitride

Lofaj, František; Wiederhorn, Sheldon M.; Long, Gabrielle G.; Jemian, Pete R.; Ferber, Mattison K.

doi:10.1002/9783527612765.ch83

Cited by 7 publications

(3 citation statements)

References 10 publications

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“…From measurements on samples of SN88 with varying amounts of applied creep strain, and using our A-USAXS data analysis method (Jemian et al, 1991), we determined that the population distribution of creep porosity was similar in size (100-600 nm) to that of the secondary phase, while the volume fraction of the creep porosity was a linear function of the applied creep strain. For samples of commercial silicon nitride SN281, where Yb is replaced by Lu, the volume fraction of the creep porosity determined from A-USAXS measurements was remarkably close to zero (Lofaj et al, 2001).…”

Section: Figurementioning

confidence: 84%

Ultra-small-angle X-ray scattering at the Advanced Photon Source

et al. 2009

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The design and operation of a versatile ultra‐small‐angle X‐ray scattering (USAXS) instrument at the Advanced Photon Source (APS) at Argonne National Laboratory are presented. The instrument is optimized for the high brilliance and low emittance of an APS undulator source. It has angular and energy resolutions of the order of 10−4, accurate and repeatable X‐ray energy tunability over its operational energy range from 8 to 18 keV, and a dynamic intensity range of 108 to 109, depending on the configuration. It further offers quantitative primary calibration of X‐ray scattering cross sections, a scattering vector range from 0.0001 to 1 Å−1, and stability and reliability over extended running periods. Its operational configurations include one‐dimensional collimated (slit‐smeared) USAXS, two‐dimensional collimated USAXS and USAXS imaging. A robust data reduction and data analysis package, which was developed in parallel with the instrument, is available and supported at the APS.

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Section: Figurementioning

confidence: 84%

Ultra-small-angle X-ray scattering at the Advanced Photon Source

et al. 2009

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“…By choosing sintering additives which form refractory glassy phases and enhance crystallization, mechanical properties of silicon nitrides can be improved. Presently, the best additive for high temperature use is believed to be lutetia (Lu 2 O 3 ) [5][6][7]. The second aim of this paper is to demonstrate mechanical properties of sinter-forged silicon nitride with lutetia additive.…”

Section: Introductionmentioning

confidence: 99%

High Strength and High Toughness Anisotropic Silicon Nitrides Fabricated by Forging Technique

Kondo

2007

KEM

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Grain alignment control to make anisotropic microstructure is one of the most promising techniques to achieve superior mechanical properties in specific directions. Anisotropic silicon nitrides, which were fabricated by a forging technique, can show superior mechanical properties at room temperature as well as at elevated temperatures. A sinter-forged silicon nitride with yttria and alumina additives exhibited very high strength of 2.1GPa at room temperature, meanwhile that with lutetia additive showed high strength of 700MPa at 1500oC. Anisotropic silicon nitrides are also advantageous to achieve higher fracture energy. Such silicon nitrides can show 3~5 times higher fracture energy than isotropic ones. Sinter-forging technique is also applicable to fabricate porous anisotropic silicon nitrides. In this paper, fabrication and mechanical properties of anisotropic silicon nitrides are briefly described.

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“…An observation that is not well understood is the dramatically improved creep resistance of silicon nitrides densified with Lu 2 O 3 as a sintering aid. Studies on two commercial grades of silicon nitride using Lu 2 O 3 as a sintering aid, SN 281 [20,21,22,23,24,25] and SN 282 [26] (both made by Kyocera Corp, Kyoto, Japan)* indicate a decrease in creep rate and an increase in lifetime over that of other commercial grades of silicon nitride containing sintering aids such as Yb 2 O 3 or Y 2 O 3 . At temperatures greater than 1450 °C, for example, studies show that both SN 281 and SN 282 have a tensile creep resistance as much as four orders of magnitude greater than that of the best commercial grades of silicon nitride [20,26].…”

Section: Introductionmentioning

confidence: 99%

Creep Behavior of Improved High Temperature Silicon Nitride

Wiederhorn

Krause²,

Lofaj³

et al. 2005

KEM

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New data are presented on the tensile creep behavior of silicon nitride sintered with Lu2O3. The data are compared with two earlier sets of data collected on the same material. The older sets gave results that are difficult to explain theoretically: a high value for the stress exponent, n=5.33, and no cavitation. The new set of data also gave no cavitation, but gave a stress exponent, n=1.81, that can be rationalized theoretically in terms of solution-precipitation creep of the silicon nitride grains. An analysis of variance showed that one of the earlier sets of data was statistically consistent with the newer set, whereas the other set of data was not. Combining the two sets of data that agreed statistically yields a consistent picture of creep with a low value of the stress exponent and no cavitation. The stress exponent for the combined set of data is n=1.87±0.48 (95 % confidence limits). The tensile creep mechanism of the silicon nitride containing Lu2O3, solution-precipitation, differs from those of other silicon nitrides, for which tensile creep has been attributed to cavitation. Enhancement of the creep resistance of the silicon nitride sintered with Lu2O3 may be a consequence of the fact that Lu2O3 produces a more deformation resistant amorphous phase at the two grain junctions, than do Y2O3 or Yb2O3. In parallel, reducing the amount of secondary phase below a critical limit, or increasing the viscosity of the two grain boundaries relative to three-grain junctions reduces the ability of the material to cavitate during creep, and forces the creep mechanism to change from cavitation to solution-precipitation.

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Cavitation Creep in the Next Generation Silicon Nitride

Cited by 7 publications

References 10 publications

Ultra-small-angle X-ray scattering at the Advanced Photon Source

Ultra-small-angle X-ray scattering at the Advanced Photon Source

High Strength and High Toughness Anisotropic Silicon Nitrides Fabricated by Forging Technique

Creep Behavior of Improved High Temperature Silicon Nitride

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