Microstructural Contributions to the Fracture Resistance of Silicon Nitride Ceramics

Becher, Paul; Hwang, Shyh‐Lung; Hua, Lin; Tiegs, T.N.

doi:10.1007/978-94-011-0992-5_6

Cited by 51 publications

(32 citation statements)

References 18 publications

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“…This may arise from bending components which develop upon crack opening on an inclined bridging site. 26 A larger diameter of the acicular crystals in the present 3D-random material may also enhance the probability of crystallographic defects and, thus, lead to a statistically lower crystal strength. However, the micrometer-scale resolution of the present stress analysis by Raman spectroscopy does not allow us to…”

Section: (2) Stereological Assessment Of the Bridging Zonementioning

confidence: 98%

Raman Microprobe Evaluation of Bridging Stresses in Highly Anisotropic Silicon Nitride

Pezzotti

Ichimaru

Ferroni

et al. 2001

Journal of the American Ceramic Society

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The microscopic bridging stress distribution developed behind the crack tip of a highly anisotropic silicon nitride has been measured along the crack profile using Raman microprobe spectroscopy with a micrometer spatial resolution. The neartip rising R-curve behavior and the crack-opening displacement (COD) profile of the material were also determined and discussed in comparison with the Raman microstress data. A comparison with the fracture behavior of a previously investigated silicon nitride material with a three-dimensional random microstructure is also proposed. According to this set of micro/macroscopic fracture characterizations, a self-consistent view of toughening behavior in silicon nitride ceramics is obtained, and the role on toughness of anisotropically oriented acicular grains clarified. In agreement with previous studies, it is confirmed that crack-face bridging is the most effective mechanism for toughening silicon nitride ceramics.

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Section: (2) Stereological Assessment Of the Bridging Zonementioning

confidence: 98%

Raman Microprobe Evaluation of Bridging Stresses in Highly Anisotropic Silicon Nitride

Pezzotti

Ichimaru

Ferroni

et al. 2001

Journal of the American Ceramic Society

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“…The toughening of Si3N4 ceramics seems to be based on crack wake mechanisms such as crack bridging, grain rotation, or pull-out and it scales with (diameter of the elongated grains)l/Z [7]. The dependency on the aspect ratio of the elongated grains is still not well understood due to the lack of enough experimental data, but observations reveal that coarse grained materials exhibit a higher fracture toughness than fine grained ones and their fracture resistances increases with crack propagation (R-curve behaviour).…”

Section: Microstructural Developmentmentioning

confidence: 99%

“…In both cases a weak interface is required in order to provide a transgranular fracture mode [6]. The interface strength can be controlled by the composition of the sintering additives which form an amorphous grain boundary layer between silicon nitride grains [7]. However, there seems to be a contradiction between the development of high strength and high-toughness Si3Nq-ceramics and high-temperature resistant materials because of the fact that the grain boundary is on one hand responsible for the excellent properties at low temperatures, but it limits on the other hand the properties at temperatures above its softening point.…”

Section: Introductionmentioning

confidence: 99%

Relationship between microstructure and mechanical properties of silicon nitride ceramics

Hoffmann¹

1995

Pure and Applied Chemistry

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Abstract; The microstructure of silicon nitride ceramics is related to the mechanical properties. It is demonstrated that the room temperature strength and toughness is determined by size and morphology of the Si3N4 grains and the grain boundary phase. The high temperature properties are mainly controlled by the composition and properties of the grain boundary. The grain boundary crystallization, as one strategy for the development of high-temperature resistant materials, is analysed with respect to the phase relationships between Si3N4 and the additives and the impossibility of a complete devitrification. It is shown that small amounts of impurities in the starting powder can be enriched in thin grain boundary films and degrade the high-temperature properties.

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“…The fracture strength depends on the interface strength; a weak interface is required to induce transgranular fracture. The interface strength is determined by the additive composition and impurities [75]. Another particularly difficult compromise exists between the requirement for sinterability and grain anisotropy, favored by the liquid-phase assisted sintering, and requirement of high-temperature strength and creep resistance that is limited by the viscous flow of the silicate liquid.…”

Section: Sintering Chemistry Of Additives In Bulk Nitride Ceramicsmentioning

confidence: 99%

Chemical research needed to improve high-temperature processing of advanced ceramic materials (Technical report)

Kolář

2000

Pure and Applied Chemistry

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Republication or reproduction of this report or its storage and/or dissemination by electronic means is permitted without the Chemical research needed to improve high-temperature processing of advanced ceramic materialsAbstract: Of the principal classes of engineering materials, ceramics are in many ways the most interesting and challenging. Many properties, or combination, of properties, not achievable with other classes of materials give ceramics enormous technical potential. The main obstacles that prevent the wider use of ceramics include insufficient reliability, reproducibility, and high cost. The physical basis of the processing steps is well established, however, the chemical reactions which occur during the high-temperature processing frequently influence the densification process and microstructure development of ceramics in an unpredictable way. Therefore, an ability to understand and control the chemical processes that occur during ceramic processing are necessary to advance and open up new uses for technical ceramics. The aim of this present report, resulting from discussions of an ad hoc group of ceramists and chemists, is to expose the areas of chemical research that can most benefit the processing, and further the use, of ceramic materials.

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Microstructural Contributions to the Fracture Resistance of Silicon Nitride Ceramics

Cited by 51 publications

References 18 publications

Raman Microprobe Evaluation of Bridging Stresses in Highly Anisotropic Silicon Nitride

Raman Microprobe Evaluation of Bridging Stresses in Highly Anisotropic Silicon Nitride

Relationship between microstructure and mechanical properties of silicon nitride ceramics

Chemical research needed to improve high-temperature processing of advanced ceramic materials (Technical report)

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