Nitrogen self‐diffusion in silicon nitride

1976 ◽  
Vol 65 (7) ◽  
pp. 2668-2671 ◽  
Author(s):  
Kazunori Kijima ◽  
Shin‐ichi Shirasaki
Keyword(s):  
Silicon Nitride ◽  
Self Diffusion

Diffusion in Isotope Heterostructures Investigated by Neutron Reflectometry

2009 ◽  
Vol 289-292 ◽  
pp. 697-703 ◽  
Author(s):  
Erwin Hüger ◽  
Jochen Stahn ◽  
Udo Geckle ◽  
Michael Bruns ◽  
Harald Schmidt
Keyword(s):  
Thin Films ◽  
Silicon Nitride ◽  
Amorphous Silicon ◽  
Model System ◽  
Neutron Reflectometry ◽  
Diffusion In Solids ◽  
Amorphous Silicon Nitride ◽  
Self Diffusion

Studies of self-diffusion in solids are presented, which are based on neutron reflectometry. For the application of this technique the samples under investigation are prepared in form of isotope heterostructures. These are nanometer sized thin films, which are chemically completely homogenous, but isotope modulated. Using this method, diffusion lengths in the order of 1 nm and below can be detected which allows to determine ultra low diffusivities in the order of 10-25 m2/s. For the model system amorphous silicon nitride we demonstrate how the structure of the isotope hetrostructures (triple layers or multilayers) influences the efficiency of diffusivity determination.

Self-diffusion of silicon-30 and nitrogen-15 in α phase silicon nitride

1988 ◽  
Vol 105-106 ◽  
pp. 47-54 ◽  
Author(s):  
Kirsten P. Kunz ◽  
Vinod K. Sarin ◽  
Robert F. Davis ◽  
Scott R. Bryan
Keyword(s):  
Silicon Nitride ◽  
Self Diffusion ◽  
Α Phase

scholarly journals Structural relaxation and self-diffusion in covalent amorphous solids: Silicon nitride as a model system

2007 ◽  
Vol 102 (4) ◽  
pp. 043516 ◽  
Author(s):  
H. Schmidt ◽  
W. Gruber ◽  
T. Gutberlet ◽  
M. Ay ◽  
J. Stahn ◽  
...  
Keyword(s):  
Silicon Nitride ◽  
Structural Relaxation ◽  
Amorphous Solids ◽  
Model System ◽  
Self Diffusion

Influence of Sintering Aids on the Sintering and Conductivity Properties of Si3N4 Composites

2016 ◽  
Vol 697 ◽  
pp. 457-461
Author(s):  
Yong Jiang ◽  
Lan Er Wu ◽  
Wan Xiu Hai
Keyword(s):  
Diffusion Coefficient ◽  
Rare Earth ◽  
High Temperature ◽  
Silicon Nitride ◽  
Light Rare Earth ◽  
Sintering Aids ◽  
Si3n4 Ceramic ◽  
Sintering Aid ◽  
Self Diffusion ◽  
Self Diffusion Coefficient

Silicon nitride (Si3N4) is one of the most important engineering materials. The developing trend of Si3N4 ceramic should be its composite with reinforce phase. However, due to its low self-diffusion coefficient at high temperature, the Si3N4 is very hard to be densified without sintering aids. In the present work, the Y2O3 and light rare-earth oxides of La series (La2O3, CeO2, Pr2O3, Sm2O3) and AlN, Al2O3, MgO, CaCO3 were chosen to be sintering aids. Their effect on the sintering of Si3N4 composite was studied. The results showed that the Y2O3 was the best sintering aid in all members, and the Y2O3-La2O3-AlN ternary composition was the best formula.

Nitrogen self-diffusion in silicon nitride thin films probed with isotope heterostructures

2004 ◽  
Vol 85 (4) ◽  
pp. 582-584 ◽  
Author(s):  
H. Schmidt ◽  
G. Borchardt ◽  
M. Rudolphi ◽  
H. Baumann ◽  
M. Bruns
Keyword(s):  
Thin Films ◽  
Silicon Nitride ◽  
Self Diffusion

Lattice Imaging of Grain Boundaries in Ceramics

1977 ◽  
Vol 35 ◽  
pp. 114-115
Author(s):  
D. R. Clarke ◽  
G. Thomas
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Grain Boundaries ◽  
High Temperature Strength ◽  
Current Interest ◽  
Lattice Imaging ◽  
Special Significance ◽  
Structural Applications ◽  
Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

TEM Studies of Grain Boundary Films in Si3N4 Ceramics

1991 ◽  
Vol 49 ◽  
pp. 930-931
Author(s):  
H.-J. Kleebe ◽  
J.S. Vetrano ◽  
J. Bruley ◽  
M. Rühle
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Hot Isostatic Pressing ◽  
Amorphous Film ◽  
Liquid Phase Sintering ◽  
Second Phase ◽  
High Temperature Mechanical Properties ◽  
Triple Points ◽  
Boundary Films

It is expected that silicon nitride based ceramics will be used as high-temperature structural components. Though much progress has been made in both processing techniques and microstructural control, the mechanical properties required have not yet been achieved. It is thought that the high-temperature mechanical properties of Si3N4 are limited largely by the secondary glassy phases present at triple points. These are due to various oxide additives used to promote liquid-phase sintering. Therefore, many attempts have been performed to crystallize these second phase glassy pockets in order to improve high temperature properties. In addition to the glassy or crystallized second phases at triple points a thin amorphous film exists at two-grain junctions. This thin film is found even in silicon nitride formed by hot isostatic pressing (HIPing) without additives. It has been proposed by Clarke that an amorphous film can exist at two-grain junctions with an equilibrium thickness.

Electron Microscopy of Silicon Nitride-Based Ceramics

1991 ◽  
Vol 49 ◽  
pp. 926-927
Author(s):  
Gareth Thomas
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Silicon Nitride ◽  
World Wide ◽  
Sintering Temperature ◽  
Liquid Phase Sintering ◽  
High Temperature Strength ◽  
Sintering Additives ◽  
Glass Forming ◽  
Dense Product

Silicon nitride and silicon nitride based-ceramics are now well known for their potential as hightemperature structural materials, e.g. in engines. However, as is the case for many ceramics, in order to produce a dense product, sintering additives are utilized which allow liquid-phase sintering to occur; but upon cooling from the sintering temperature residual intergranular phases are formed which can be deleterious to high-temperature strength and oxidation resistance, especially if these phases are nonviscous glasses. Many oxide sintering additives have been utilized in processing attempts world-wide to produce dense creep resistant components using Si3N4 but the problem of controlling intergranular phases requires an understanding of the glass forming and subsequent glass-crystalline transformations that can occur at the grain boundaries.

Examination of Fracture Interfaces in Silicon Nitride

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.

Tensile Creep of Y-Si3N4: II. Cavitation

1991 ◽  
Vol 49 ◽  
pp. 972-973 ◽  
Author(s):  
B. J. Hockey ◽  
S. M. Wiederhorn
Keyword(s):  
Silicon Nitride ◽  
Creep Rupture ◽  
Tensile Creep ◽  
Sintering Aids ◽  
Microstructural Changes

ATEM has been used to characterize three different silicon nitride materials after tensile creep in air at 1200 to 1400° C. In Part I, the microstructures and microstructural changes that occur during testing were described, and consistent with that description the designations and sintering aids for these materials were: W/YAS, a SiC whisker reinforced Si3N4 processed with yttria (6w/o) and alumina (1.5w/o); YAS, Si3N4 processed with yttria (6 w/o) and alumina (1.5w/o); and YS, Si3N4 processed with yttria (4.0 w/o). This paper, Part II, addresses the interfacial cavitation processes that occur in these materials and which are ultimately responsible for creep rupture.

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