The Lifetime of Silicon Nitride Limited by Cavity Nucleation in the Intergranular Glassy Phase

1992 ◽  
pp. 209-218
Author(s):  
Jianren Zeng ◽  
Isao Tanaka ◽  
Koichi Niihara
Keyword(s):  
Silicon Nitride ◽  
Glassy Phase ◽  
Cavity Nucleation

The microstructure and creep deformation of hot-pressed Si3N4 with different amounts of sintering additives

1996 ◽  
Vol 11 (1) ◽  
pp. 120-126 ◽  
Author(s):  
Sang-Young Yoon ◽  
Takashi Akatsu ◽  
Eiichi Yasuda
Keyword(s):  
Activation Energy ◽  
Silicon Nitride ◽  
Creep Rate ◽  
Grain Boundary ◽  
Apparent Activation Energy ◽  
Creep Test ◽  
Creep Deformation ◽  
Glassy Phase ◽  
Microstructural Observation ◽  
Rate Limiting

Compressive creep deformation of hot-pressed silicon nitride with different amounts of grain boundary glassy phase was investigated at 1300–1400 °C under 30–100 MPa. The stress exponent of the creep rate was determined to be nearly unity. The apparent activation energy of silicon nitride with a larger amount of glassy phase was measured to be about 700 kJ/mole, and that with a smaller amount of glassy phase was found to be 400 kJ/mole. In addition, the microstructural observation found that no cavity appeared and grain boundary glass was recrystallized during creep test. Thus, the rate-limiting steps in solution/precipitation creep mechanism change from the solution-reprecipitation of Si3N4 grains to the diffusion through the grain boundary with increasing the amount of glassy phase.

The Effect of Glass Chemistry on the Microstructub and Properties of Self Reinforced Silicon Nitride

1992 ◽  
Vol 287 ◽  
Author(s):  
Aleksander J. Pyzik ◽  
Daniel F. Carroll ◽  
C. James Hwang
Keyword(s):  
Silicon Nitride ◽  
Glass Matrix ◽  
Glassy Phase ◽  
Large Degree ◽  
Sufficient Condition ◽  
Flexure Strength ◽  
Maximum Flexure ◽  
The Matrix ◽  
Matrix Reinforcement

ABSTRACTThe advantage of self-reinforced silicon nitride is the in-situ control of the microstructure. This control is provided in large degree by the chemistry of glassy phase which can be adjusted to tailor the morphology of silicon nitride grains as well as the matrix - reinforcement interface. The presence of high aspect ratio silicon nitride grains is necessary but not sufficient condition to produce materials with optimum properties. For maximum flexure strength and fracture toughness an optimized glass matrix is required.

scholarly journals Quantitative Estimation of Intergranular Glassy Phase of Silicon Nitride Ceramics

1993 ◽  
Vol 101 (1172) ◽  
pp. 480-483
Author(s):  
Kazumasa TAKATORI ◽  
Shigetaka WADA ◽  
Nobuo KOBAYASHI
Keyword(s):  
Silicon Nitride ◽  
Glassy Phase ◽  
Quantitative Estimation ◽  
Nitride Ceramics

Corrosion of Silicon Nitride Ceramics by Nitric Acid

1992 ◽  
Vol 287 ◽  
Author(s):  
Kunihiko Kanbara ◽  
N. Uchida ◽  
K. Uematsu ◽  
T. Kurita ◽  
K. Yoshimoto ◽  
...  
Keyword(s):  
Weight Loss ◽  
Nitric Acid ◽  
Silicon Nitride ◽  
Glassy Phase ◽  
Strength Loss ◽  
Ionic Species ◽  
Corrosion Layer ◽  
Nitride Ceramics ◽  
Conventional Drying ◽  
Icp Analysis

ABSTRACTCorrosion of silicon nitride was studied in boiling nitric acid to examine its feasibility as a drying pan material in the reprocessing of nuclear fuel. Unlike stainless steel (a conventional drying pan material), the weight loss and strength degradation were negligible in the concentration of nitric acid. The corrosion increased with decreasing concentration of nitric acid. At the concentration of 1-6N, the maximum losses of weight and strength were 0.8% and over 40%, respectively, in 200 h. Ionic species dissolved in nitric acid were determined by ICP analysis and were found to be accurately correlated to the weight loss and thickness of the corrosion layer determined by micrography. In the corrosion layer, grain boundary glassy phase was selectively dissolved. Strength loss was correlated to the weight loss and was ascribed to the reduced load bearing area due to corrosion.

A Microstructural Study of Hot Pressed and Reactive Sintered Beta-Silicon Nitride Coated with Alumina

1997 ◽  
Vol 3 (S2) ◽  
pp. 735-736
Author(s):  
G. Ghosh ◽  
S. Vaynman ◽  
M. E. Fine
Keyword(s):  
Silicon Nitride ◽  
Glassy Phase ◽  
Phase Particle ◽  
High Strength ◽  
High Fracture Toughness ◽  
Boundary Phase ◽  
High Fracture ◽  
Engineering Applications ◽  
Particle Coating ◽  
Blending Method

Silicon nitride-based or SiAlON ceramics are increasingly being considered for many engineering applications due to their low density, high strength, and high modulus. For many engineering applications SiAlON ceramics are required to have, among many other properties, both high fracture toughness and good tribological properties. Typically, an interlocking microstructure consisted of β-Si3N4 and/or β'-SiAlON grains is produced, by sintering Si3N4 with desirable additive(s), with a residual glassy or partly crystalline grain boundary phase. The fracture process in such a microstructure is predominantly intergranular, the cracks tend to follow a tortuous path. However, the presence of an intergranular glassy phase causes rapid deterioration of properties at temperature above the glass transition temperature. Therefore, in order to improve high-temperature properties of these ceramics it is desirable to minimize, and if possible to eliminate, the intergranular glassy phase. Particle coating techniques are receiving increasing attention as they are convenient ways of incorporating sintering aids/dopants more uniformly than conventional powder blending method.

Hot-Pressed Silicon Nitride Ceramics With Rare-Earth Oxides Additives

1985 ◽  
Author(s):  
Xu Youren ◽  
Huang Liping ◽  
Fu Xiren ◽  
Yen Tungsheng
Keyword(s):  
Fracture Toughness ◽  
Rare Earth ◽  
Silicon Nitride ◽  
Room Temperature ◽  
Glassy Phase ◽  
Rare Earth Oxides ◽  
Bend Strength ◽  
Silicon Nitride Ceramic ◽  
X Ray ◽  
Nitride Ceramics

A hot-pressed silicon nitride ceramic material with rare-earth oxides additive has been processed, its bend strength maintains 800–900 MPa up to 1300°C and measures 680 MPa at 1400°C, its fracture toughness at room temperature is 4.38–4.96 MPam. X-ray, SEM, EDS and electron probe analyses reveal that the microstructure of this material is composed of fine β-Si3N4 grains, α-Si3N4 whiskers, small tetragonal lanthanide crystals and La-containing glassy phase. Observation on fracture surface shows that the fracture path is mainly transcrystalline up to 1400°C. The effects of additives on strength and fracture toughness of HPSN obtained are also discussed.

Grain boundary glassy phase and abnormal grain growth of silicon nitride ceramics

2001 ◽  
Vol 27 (5) ◽  
pp. 603-605 ◽  
Author(s):  
Haitao Yang ◽  
Lin Gao ◽  
Gangqin Shao ◽  
Runze Xu ◽  
Peiyun Huang
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Grain Growth ◽  
Glassy Phase ◽  
Abnormal Grain Growth ◽  
Nitride Ceramics

The Use of Organometallic Precursors to Silicon Nitride as Binders

1988 ◽  
Vol 121 ◽  
Author(s):  
Stuart T. Schwab ◽  
Cheryl R. Blanchard-Ardid
Keyword(s):  
High Temperature ◽  
Silicon Nitride ◽  
Glassy Phase ◽  
Ceramic Powder ◽  
Ceramic Component ◽  
High Temperature Properties ◽  
Preceramic Polymers ◽  
Final Microstructure ◽  
Binder Material ◽  
Organometallic Precursors

ABSTRACTCurrent techniques of advanced ceramic component fabrication are based on pressureless green body consolidation technology in which voids often remain in the final microstructure. Much of this residual porosity is created when the organic binder used to consolidate the ceramic powder burns off on sintering. A new concept in the field of ceramic processing is the use of an organometallic binder material which will pyrolyze on sintering and convert into a predetermined ceramic. Silicon nitride (Si3N4) is a ceramic material in great demand for elevated temperature applications because of its excellent high temperature properties. At the present time, silicon nitride cannot be successfully processed without the use of costly pressure sintering (e.g., hot pressing), or the addition of a glassy phase, which degrades the high temperature properties.Various preceramic polymers to be used as binders for cold pressing operations have been synthesized and studied. It has been demonstrated that these polymers may be dissolved in an appropriate organic solvent and mixed with a powder. Removal of the solvent yields homogeneous mixtures which may be consolidated into highly dense (> 66% of theoretical) green bodies. The ceramic yields of these polymers have also been determined.

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