Journal ArticleDOI
Microstructural Development During Gas‐Pressure Sintering of α‐Silicon Nitride
Mamoru Mitomo,Satoshi Uenosono +1 more
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TLDR
In this article, the diameters and aspect ratios of hexagonal grains in the sintered materials were measured on polished and etched surfaces, and the fracture toughness of gas-pressure-sintered Si3N4 ceramics was not related to the α content in the starting powder or the aspect ratio of the grains, but to the diameter of the large grains.Abstract:
Gas-pressure sintering of α-Si3N4 was carried out at 1850 ° to 2000°C in 980-kPa N2. The diameters and aspect ratios of hexagonal grains in the sintered materials were measured on polished and etched surfaces. The materials have a bimodal distribution of grain diameters. The average aspect ratio in the materials from α-Si3N4 powder was similar to that in the materials from β-Si3N4 powder. The aspect ratio of large and elongated grains was larger than that of the average for all grains. The development of elongated grains was related to the formation of large nuclei during the α-to-β phase transformation. The fracture toughness of gaspressure-sintered materials was not related to the α content in the starting powder or the aspect ratio of the grains, but to the diameter of the large grains. Crack bridging was the main toughening mechanism in gas-pressure-sintered Si3N4 ceramics.read more
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Journal ArticleDOI
Microstructure Control of Silicon Nitride by Seeding with Rodlike β‐Silicon Nitride Particles
TL;DR: In this paper, the effect of seeding on microstructure development and mechanical properties of silicon nitride was investigated by the use of morphologically regulated rodlike β-Si3N4 singlecrystal particles with a diameter of 1 μm and a length of 4 μm as seed crystals.
Book ChapterDOI
Silicon Nitride Ceramics
G. Petzow,M. Herrmann +1 more
TL;DR: In this paper, the interrelation between pure Si3N4, the densification of the powder including the role of sintering additives, microstructural engineering, physicochemical properties of the sintered Si3n4 ceramics (SSN, GPSN, HPSN, HIP-SSN and HIP-SN) are described in more detail and compared to reaction-bonded RBSN, which are produced by nitridation of silicon powders.
Journal ArticleDOI
Mechanical properties of silicon nitride-based ceramics and its use in structural applications at high temperatures
TL;DR: In this paper, the room temperature and high-temperature properties of Si 3 N 4 based ceramics are discussed and described in more detail, and a variety of interesting properties can be specifically designed to produce a given behavior profile.
Journal ArticleDOI
Effect of Initial α‐Phase Content on Microstructure and Mechanical Properties of Sintered Silicon Carbide
TL;DR: In this paper, the effects of initial α-phase content on the microstructure and the mechanical properties of the liquid phase-sintered and subsequently annealed materials were investigated.
Journal ArticleDOI
Relationship between Microstructure, Toughening Mechanisms, and Fracture Toughness of Reinforced Silicon Nitride Ceramics
TL;DR: In this article, pull-out and elastic bridging were most frequently observed as the toughening mechanisms in samples with fine-grained microstructures having needlelike {beta}-Si{sub 3}N{sub 4} grains with diameters of 1 microm.
References
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Journal ArticleDOI
Crack deflection processes—I. Theory
TL;DR: In this article, a fracture mechanics approach has been used to predict fracture toughness increases due to crack deflection around second phase particles, based on a determination of the initial tilt and the maximum twist of the crack front between particles.
Journal ArticleDOI
Toughening Behavior in Whisker-Reinforced Ceramic Matrix Composites
TL;DR: In this article, the authors analyzed the toughening behavior of a bridging zone immediately behind the crack tip of a SiC-whisker-reinforced ceramics.
Journal ArticleDOI
Crack deflection processes—II. Experiment
TL;DR: In this article, particle morphology and size were examined with respect to toughening by crack deflection in a series of hot-pressed silicon nitrides comprised of rod-shaped grains of various aspect ratios and a barium-alumino-silicate glass ceramic containing spherulites.
Journal ArticleDOI
Hot-pressing and the ?-? phase transformation in silicon nitride
TL;DR: In this article, the authors measured the kinetics of densification and the phase transformation in hot-pressing of silicon nitride ceramics using magnesia as additive, and found that the rate was proportional to the amount of additive.