Characterization of High Temperature Strength of Si3N4Composite Ceramics According to the Amount of SiO2Nano Colloidal Added

2009 ◽  
Vol 33 (11) ◽  
pp. 1233-1238 ◽  
Author(s):  
Ki-Woo Nam ◽  
Kun-Chan Lee
Keyword(s):  
High Temperature ◽  
High Temperature Strength

SYNTHESIS AND CHARACTERIZATION OF Si3N4@Al(OH)3–Y(OH)3 CORE-SHELL COMPOSITE PARTIC3LES

2008 ◽  
Vol 15 (05) ◽  
pp. 581-585 ◽  
Author(s):  
JIE-GUANG SONG ◽  
GANG-CHANG JI ◽  
SHI-BIN LI ◽  
LIAN-MENG ZHANG
Keyword(s):  
High Temperature ◽  
High Performance ◽  
Ceramic Materials ◽  
Composite Particles ◽  
Core Shell ◽  
High Temperature Strength ◽  
Bet Analysis ◽  
Co Precipitation ◽  
Shell Composite

Silicon nitride ( Si 3 N 4) has attracted substantial interest because of its extreme chemical and physical properties, but the sintering densification of Si 3 N 4 is difficult, and it is easily oxidized in the high-temperature air to impact high-temperature strength, which restricts its applied range. In order to decrease the oxidization and improve the strength of Si 3 N 4 at high temperature, the surface of Si 3 N 4 is coated with Al ( OH )3 and Y ( OH )3 to synthesis Si 3 N 4@ Al ( OH )3– Y ( OH )3 core-shell composite particles. Through TEM, XRD, and BET analysis, when pH is about 9, Si 3 N 4@ Al ( OH )3– Y ( OH )3 core-shell composite particles are successfully synthesized by co-precipitation methods. Coating layer is about 200 nm, which is compaction and conformability. Dispersion of coated Si 3 N 4 with Al ( OH )3 and Y ( OH )3 particles are very good. Synthesis of Si 3 N 4@ Al ( OH )3– Y ( OH )3 core-shell composite powder will lay the foundation for preparing high-performance YAG/Si 3 N 4 multiphase ceramic materials.

TEM studies of dislocations in deformed Ga1-xInxAs single crystals

1988 ◽  
Vol 46 ◽  
pp. 900-901
Author(s):  
R. S. Rai ◽  
S. Guruswamy ◽  
K. T. Faber ◽  
J. P. Hirth
Keyword(s):  
High Temperature ◽  
Dislocation Density ◽  
Single Crystals ◽  
Dark Field ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
High Temperature Strength ◽  
Density Reduction ◽  
Transmission Electron

The perfection of GaAs single crystals can be controlled by doping the GaAs with In, at a level of about 5x1019-1x1020/cm3, in single crystals grown by the LEC process. It has been observed that In doping at this level reduces the grown in dislocation density from 104-l05 to ≤ 102/cm2 and results in a large increase in high temperature strength . However, the role of In in dislocation density reduction is not clearly understood. Therefore, a systematic study has been performed with the help of high temperature deformation of In-doped and undoped GaAs single crystals followed by dislocation structural characterization by transmission electron microscopy of the deformed specimens. Here, some results of dislocation studies performed by TEM are descri bed.Samples were examined in a JEOL JEM 200CX transmission electron microscope equipped with a double tilt goniometer stage. The standard g.b criterion was employed for characterization of dislocations. Dark-field weak beam pictures were taken for characterization of partial dislocations and dipoles.

scholarly journals High Temperature Behavior of Al-7Si-0.4Mg Alloy with Er and Zr Additions

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 879
Author(s):  
Elisabetta Gariboldi ◽  
Chiara Confalonieri ◽  
Marco Colombo
Keyword(s):  
High Temperature ◽  
Eutectic Silicon ◽  
A356 Alloy ◽  
Minor Element ◽  
High Temperature Strength ◽  
Creep Tests ◽  
Casting Alloys ◽  
Compression Creep ◽  
Tension And Compression

In recent years, many efforts have been devoted to the development of innovative Al-based casting alloys with improved high temperature strength. Research is often oriented to the investigation of the effects of minor element additions to widely diffused casting alloys. The present study focuses on Al-7Si-0.4Mg (A356) alloy with small additions of Er and Zr. Following previous scientific works on the optimization of heat treatment and on tensile strength, creep tests were carried out at 300 °C under applied stress of 30 MPa, a reference condition for creep characterization of innovative high-temperature Al alloys. The alloys containing both Er and Zr displayed a lower minimum creep strain rate and a longer time to rupture. Fractographic and microstructural analyses on crept and aged specimens were performed to understand the role played by eutectic silicon, by the coarse intermetallics and by α-Al matrix ductility. The creep behavior in tension of the three alloys has been discussed by comparing them to tension and compression creep curves available in the literature for Al-7Si-0.4Mg improved by minor elemental additions.

High-temperature strength characterization of advanced 9Cr-ODS ferritic steels

2009 ◽  
Vol 510-511 ◽  
pp. 115-120 ◽  
Author(s):  
S. Ukai ◽  
S. Ohtsuka ◽  
T. Kaito ◽  
H. Sakasegawa ◽  
N. Chikata ◽  
...  
Keyword(s):  
High Temperature ◽  
Ferritic Steels ◽  
High Temperature Strength ◽  
Strength Characterization

scholarly journals Recent Advances and Developments in Refractory Alloys

1993 ◽  
Vol 322 ◽  
Author(s):  
T.G. Nieh ◽  
J. Wadsworth
Keyword(s):  
High Temperature ◽  
Refractory Metal ◽  
Metal Alloys ◽  
High Temperature Strength ◽  
Refractory Alloys ◽  
Aerospace Applications ◽  
Wide Range ◽  
Recent Developments ◽  
Refractory Metal Alloys

AbstractRefractory metal alloys based on Mo, W, Re, Ta, and Nb (Cb) find applications in a wide range of aerospace applications because of their high melting points and high-temperature strength. In this paper, we present recent progress in the understanding and applications of these alloys. Recent studies to improve the oxidation and mechanical behavior of refractory metal alloys, and particularly Nb alloys, will also be discussed. Some Re structures, for extremely high temperature applications (> 2000°C), made by CVD and P/M processes, are also illustrated. Interesting work on the development of new W alloys (W-HfC-X) and the characterization of some commercial refractory metals, e.g., K-doped W, TZM, and Nb-l%Zr, continues. Finally, recent developments in high temperature composites reinforced with refractory metal filaments, and refractory metal-based intermetallics, e.g., Nb3A1, Nb2Be17, and MoSi2, are briefly described.

Influence of Thermo-Mechanical Processing on the Microstructure of Beryllia Dispersed Nickel Alloys

1973 ◽  
Vol 31 ◽  
pp. 184-185
Author(s):  
M.S. Grewal ◽  
S.A. Sastri ◽  
N.J. Grant
Keyword(s):  
High Temperature ◽  
Nickel Alloys ◽  
Thermomechanical Processing ◽  
Cold Work ◽  
High Temperature Strength ◽  
Strengthening Effect ◽  
Mechanical Processing ◽  
Uniform Dispersion ◽  
Oxide Particles ◽  
Nickel Base

Currently there is a great interest in developing nickel base alloys with fine and uniform dispersion of stable oxide particles, for high temperature applications. It is well known that the high temperature strength and stability of an oxide dispersed alloy can be greatly improved by appropriate thermomechanical processing, but the mechanism of this strengthening effect is not well understood. This investigation was undertaken to study the dislocation substructures formed in beryllia dispersed nickel alloys as a function of cold work both with and without intermediate anneals. Two alloys, one Ni-lv/oBeo and other Ni-4.5Mo-30Co-2v/oBeo were investigated. The influence of the substructures produced by Thermo-Mechanical Processing (TMP) on the high temperature creep properties of these alloys was also evaluated.

Application of TEM to Deformation, Wear, and Fracture of Ceramics

1974 ◽  
Vol 32 ◽  
pp. 472-473
Author(s):  
B. J. Hockey
Keyword(s):  
Wear Resistance ◽  
High Temperature ◽  
Mechanical Behavior ◽  
Brittle Materials ◽  
High Temperature Strength ◽  
Wide Range ◽  
Corrosive Environments ◽  
Further Development

Ceramics, such as Al2O3 and SiC have numerous current and potential uses in applications where high temperature strength, hardness, and wear resistance are required often in corrosive environments. These materials are, however, highly anisotropic and brittle, so that their mechanical behavior is often unpredictable. The further development of these materials will require a better understanding of the basic mechanisms controlling deformation, wear, and fracture.The purpose of this talk is to describe applications of TEM to the study of the deformation, wear, and fracture of Al2O3. Similar studies are currently being conducted on SiC and the techniques involved should be applicable to a wide range of hard, brittle materials.

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.

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