Phase Relationship Studies of Silicon Nitride System—A Key to Materials Design

1992 ◽  
Vol 287 ◽  
Author(s):  
T.S. Yen ◽  
W.Y. Sun
Keyword(s):  
Elevated Temperature ◽  
Silicon Nitride ◽  
Grain Boundary ◽  
Phase Behavior ◽  
Phase Diagrams ◽  
Room Temperature ◽  
Phase Relationship ◽  
Materials Design ◽  
Basic Approach ◽  
System A

ABSTRACTAdditions and revisions to several of the most important phase diagrams and phase behavior diagrams in the silicon nitride field are reviewed in this work, with emphasis on the Y-Si-A1-O-N system. This information is further used to make observations on the promising silicon nitride systems containing either highly refractory grain boundary phases or compatible matrix phases of desirable properties. Examples are provided to illustrate the advantage of such a basic approach to materials design. Hardness, toughness, strength at room temperature and elevated temperature and even sinterability can all be improved by adopting such an approach.

Perplastic SiAION—A Bird's Eye View of Silicon Nitride Ceramics

1992 ◽  
Vol 287 ◽  
Author(s):  
I-Wei Chen ◽  
Shyh-Lung Hwang
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Large Strain ◽  
Phase Relationship ◽  
Phase Evolution ◽  
Low Flow ◽  
Microstructural Development ◽  
Oxide Melt ◽  
Grain Boundary Characteristics ◽  
Boundary Characteristics

ABSTRACTSuperplastic Sialons have very fine microstructures containing submicron grains and transient phases. Fabrication of these materials requires processing at relatively low temperatures. As a result, different stages of phase evolution, including oxide melt formation, nitride dissolution, a′ and β′-SiAlON nucleation, and Sialon growth with and without concurrent deformation, can be captured in the development of these materials. In addition, only very low flow stresses are required for large strain deformation which, in turn, allows grain boundary and liquid phase processes to be manifested in the deformation behavior. Highlights of investigation of these aspects are reviewed here to shed light on the phase relationship, microstructural development, and grain boundary characteristics of silicon nitride.

scholarly journals Hot Pressed Silcon Nitride for Gas Turbine Applications

1972 ◽  
Author(s):  
M. L. Torti ◽  
G. Q. Weaver ◽  
D. W. Richerson
Keyword(s):  
Elevated Temperature ◽  
Silicon Nitride ◽  
Thermal Shock ◽  
Gas Turbine ◽  
Thermal Shock Resistance ◽  
Room Temperature ◽  
Promising Candidate ◽  
Shock Resistance ◽  
Room Temperature Strength

The high strengths now attainable with hot pressed silicon nitride combined with its good oxidation and thermal shock resistance make it a most promising candidate for advanced gas turbine hot components. This form of silicon nitride has flexural strengths of 110,000 psi at room temperature and 60,000 psi at 1200 C. A recent experimental version of the system has exhibited room temperature strength of 145,000 psi and elevated temperature (1200 C) strength of 100,000 psi. This may be the highest strength reported on any material at this elevated temperature.

Joining of silicon nitride ceramics for high-temperature applications

2000 ◽  
Vol 15 (1) ◽  
pp. 136-141 ◽  
Author(s):  
Rong-Jun Xie ◽  
Mamoru Mitomo ◽  
Li-Ping Huang ◽  
Xi-Ren Fu
Keyword(s):  
High Temperature ◽  
Silicon Nitride ◽  
Grain Boundary ◽  
Bond Strength ◽  
Room Temperature ◽  
Hot Isostatic Pressing ◽  
Joint Zone ◽  
Nitride Ceramics ◽  
High Bond ◽  
High Bond Strength

A refractory silicon nitride joint, which contains β–Si3N4 grains and grain boundary amorphous phase in the joined layer, was developed with the aid of a ceramic adhesive based on the system Si3N4–Y2O3–SiO2–Al2O3. The similarity in chemistry and microstructure between the parent ceramic and the joint zone indicates that the joining mechanism is the same as that involved in the sintering of Si3N4. The resultant joint exhibits a high bond strength of 550 MPa at 25 °C and retains a strength of 332 MPa at 1000 °C. Post-joining hot-isostatic pressing was applied to strengthen the joint, resulting in increased strengths of 668 MPa at room temperature and 464 MPa at 1000 °C.

An irreversible disappearance of the mechanical loss peak of an yttria-doped silicon nitride

2004 ◽  
Vol 19 (9) ◽  
pp. 2532-2535 ◽  
Author(s):  
T. Akatsu ◽  
Y. Kawakami ◽  
Y. Tanabe ◽  
E. Yasuda ◽  
K. Yamada ◽  
...  
Keyword(s):  
Silicon Nitride ◽  
Internal Friction ◽  
Grain Boundary ◽  
Thermal Cycling ◽  
Room Temperature ◽  
Loss Peak ◽  
Mechanical Loss ◽  
Sintering Aid ◽  
Doped Silicon ◽  
Integrated Intensity

The internal friction of a silicon nitride with a sintering aid of yttrium oxide was measured from room temperature to 1400 °C. A mechanical loss peak was typically observed at 1000 °C on heating the as-sintered specimen; however, it disappeared on cooling. Also, the peak was not observed upon heating a specimen that had been heated above 1400 °C. When we carried out thermal cycling, raising terminal temperatures from 1050 to 1400 °C, the integrated intensity of the peak gradually decreased due to the progressive crystallization of a grain-boundary amorphous phase.

Dependence of Intergranular Fracture on Boundary Topography and Cohesion

1973 ◽  
Vol 31 ◽  
pp. 150-151
Author(s):  
J. E. Doherty ◽  
A. F. Giamei ◽  
B. H. Kear ◽  
C. W. Steinke
Keyword(s):  
Grain Boundary ◽  
Room Temperature ◽  
Nickel Base Superalloy ◽  
Boundary Shear ◽  
Room Temperature Ductility ◽  
Solid Solution Matrix ◽  
Nickel Base ◽  
Solution Matrix ◽  
Different Levels ◽  
Base Superalloy

Recently we have been investigating a class of nickel-base superalloys which possess substantial room temperature ductility. This improvement in ductility is directly related to improvements in grain boundary strength due to increased boundary cohesion through control of detrimental impurities and improved boundary shear strength by controlled grain boundary micros true tures.For these investigations an experimental nickel-base superalloy was doped with different levels of sulphur impurity. The micros tructure after a heat treatment of 1360°C for 2 hr, 1200°C for 16 hr consists of coherent precipitates of γ’ Ni3(Al,X) in a nickel solid solution matrix.

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.

Characterization of intergranular cuprous oxide in polycrystalline YBa2Cu3O7-x

1988 ◽  
Vol 46 ◽  
pp. 880-881
Author(s):  
Bradley L. Thiel ◽  
Chan Han R. P. ◽  
Kurosky L. C. Hutter ◽  
I. A. Aksay ◽  
Mehmet Sarikaya
Keyword(s):  
Grain Boundary ◽  
Cuprous Oxide ◽  
Room Temperature ◽  
Boundary Phase ◽  
Spectroscopic Techniques ◽  
Transition Width ◽  
Practical Applications ◽  
Thin Foils ◽  
Superconducting Oxides

The identification of extraneous phases is important in understanding of high Tc superconducting oxides. The spectroscopic techniques commonly used in determining the origin of superconductivity (such as RAMAN, XPS, AES, and EXAFS) are surface-sensitive. Hence a grain boundary phase several nanometers thick could produce irrelevant spectroscopic results and cause erroneous conclusions. The intergranular phases present a major technological consideration for practical applications. In this communication we report the identification of a Cu2O grain boundary phase which forms during the sintering of YBa2Cu3O7-x (1:2:3 compound).Samples are prepared using a mixture of Y2O3. CuO, and BaO2 powders dispersed in ethanol for complete mixing. The pellets pressed at 20,000 psi are heated to 950°C at a rate of 5°C per min, held for 1 hr, and cooled at 1°C per min to room temperature. The samples show a Tc of 91K with a transition width of 2K. In order to prevent damage, a low temperature stage is used in milling to prepare thin foils which are then observed, using a liquid nitrogen holder, in a Philips 430T at 300 kV.

Imidazole Promoted Efficient Anomerization of β-D-Glucose Pentaacetate in Organic Solutions and Solid State

2019 ◽  
Author(s):  
Meifeng Wang ◽  
Liyin Zhang ◽  
Yiqun Li ◽  
Liuqun Gu
Keyword(s):  
Solid State ◽  
Organic Solvents ◽  
Room Temperature ◽  
Materials Design ◽  
The Future ◽  
Organic Solutions ◽  
Glucose Pentaacetate

<p></p>Anomerization of glycosides were rarely performed under basic condition due to lack of efficiency. Here an imidazole promoted anomerization of β-D-glucose pentaacetate was developed; and reaction could proceed in both organic solvents and solid state at room temperature. Although mechanism is not yet clear, this unprecedent mild anomerization in solid state may open a new promising way for stereoseletive anomerization of broad glucosides and materials design in the future..

Room-temperature grain boundary diffusion data measured from historical artifacts

2005 ◽  
Vol 96 (10) ◽  
pp. 1187-1192 ◽  
Author(s):  
Raymond J. Kremer ◽  
Mysore A. Dayananda ◽  
Alexander H. King
Keyword(s):  
Grain Boundary ◽  
Room Temperature ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Diffusion Data
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