Characterization of SiC Ceramic Tube Prepared by the Combined CVI and CVD Process

2014 ◽  
Vol 94 ◽  
pp. 38-42 ◽  
Author(s):  
Ji Yeon Park ◽  
Dae Jong Kim ◽  
Weon Ju Kim
Keyword(s):  
High Temperature ◽  
Composite Layer ◽  
Ductile Failure ◽  
Fission Products ◽  
Chemical Vapor ◽  
High Strength ◽  
Fuel Cladding ◽  
Loss Of Coolant Accident ◽  
Safety Margins ◽  
Structural Applications

SiCf/SiC composites are one of the candidates for high temperature structural applications because of their high strength and corrosion resistance under severe conditions and stability under neutron irradiation [1~3]. A silicon carbide fuel cladding for the light water cooled reactors (LWRs) may allow a number of advances, including: the increased safety margins under transients and accident scenarios, such as loss of coolant accident; the improved resource utilization via a higher burn-up beyond the present limit of 62 GWd/MTU; and improved waste management [3~5]. Some components of SiCf/SiC composite will be applied as tubular geometry for the high-temperature core parts. The proposed design of an advanced LWR fuel cladding, referred to as Triplex, consists of three layers: an inner SiC monolith, a central SiCf/SiC composite, and an outer dense SiC evrionmental barrier coating. The inner SiC layer provides the strength and hermeticity to contain fission products. The SiCf/SiC composite layer fabricated by the CVI process provides a pseudo-ductile failure mode. The outer SiC thin coating layer protects against corrosion [5]. The chemical vapor deposition (CVD) technique is an effective approach for the fabrication of SiCf/SiC composite and coated SiC monolith [6]. To increase the homogeneity of the microstructure and the deposition rate of a SiC tube, the process parameters should be optimized and modified.

Dependence of Tensile Strength on Geometrical Interface Conditions of Bonded Dissimilar Materials

2013 ◽  
Author(s):  
Masayoshi Tateno ◽  
Eiichiro Yokoi
Keyword(s):  
High Temperature ◽  
Structural Design ◽  
Dissimilar Materials ◽  
High Strength ◽  
Interface Conditions ◽  
Engineering Structures ◽  
Fine Ceramic ◽  
Bonded Interface ◽  
Structural Applications ◽  
Structural Parts

Many engineering structures applied for generating energy are said to have been requiring high strength under high temperature conditions. Fine ceramic is expected to be useful in structural applications in various industries by joining to metals. Ceramic can be used in structural parts for engineering where resistance to high temperature and/or high strength are required from the viewpoint of the optimum structural design. Use of ceramic for engineering structures by joining to metal generates a bonded interface between the ceramic and metal.

Dislocation loops in α-silicon nitride single crystals

1992 ◽  
Vol 50 (1) ◽  
pp. 342-343
Author(s):  
H. Suematsu ◽  
J. J. Petrovic ◽  
T. E. Mitchell
Keyword(s):  
High Temperature ◽  
Silicon Nitride ◽  
Single Crystals ◽  
Mass Production ◽  
High Strength ◽  
Deformation Characteristics ◽  
Dislocation Loops ◽  
Production Lines ◽  
Compressor Rotor ◽  
Structural Applications

Silicon nitride(Si3N4) is well known to be a most promising ceramic material for high temperature structural applications. It has high strength even at 1200°C and its fracture toughness is about 5 to 7 MPa•m½. Si3N4 has been manufactured on mass production lines as the compressor rotor for turbo chargers. For high temperature use, it is important to know the deformation characteristics of the material and the role played by dislocations and other defects. However, research on the nature of defects in Si3N4 has been limited considering the importance of Si3N4. In this study, we have examined defects in single crystals of Si3N4.

Dislocation structures in titanium aluminides deformed at 815°C

1990 ◽  
Vol 48 (4) ◽  
pp. 984-985
Author(s):  
W.T. Donlon ◽  
W.E. Dowling ◽  
J.E. Allison
Keyword(s):  
High Temperature ◽  
Automobile Industry ◽  
Titanium Aluminides ◽  
Thermomechanical Processing ◽  
High Strength ◽  
Fatigue Properties ◽  
Major Drawback ◽  
Cast Material ◽  
Heat Treated ◽  
Structural Applications

Ordered (L10) intermetallic γ-TiAl alloys are candidates for high temperature structural applications in the automobile industry because of their low density and high strength at elevated temperature. The major drawback of these materials is their low ductility at ambient temperature. Improvements in low temperature ductility may be achieved without sacrificing the desired high temperature performance by optimizing the microstructure through thermomechanical processing. This investigation measured the tensile and fatigue properties of an “as-cast” and cast plus heat treated Ti-48A1-1V-0.2C (at%) alloy at 25 and 815°C.The microstructure of both samples consisted of primary γ grains with an average intercept size of 100 μm, and regions of a γ matrix with α2 lathes. The vol% of the primary γgrains was 40% and 85% in the “as-cast” and cast plus heat treated samples, respectively. Figure 1 shows the microstructure of the “as-cast” material.

Eutectoid Phase Transformations in Nb-Silicide In-Situ Composites

2002 ◽  
Vol 753 ◽  
Author(s):  
B. P. Bewlay ◽  
S. D. Sitzman ◽  
L. N. Brewer ◽  
M. R. Jackson
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Low Temperature ◽  
Phase Transformations ◽  
Oxidation Resistance ◽  
High Strength ◽  
Eutectoid Decomposition ◽  
In Situ Composites ◽  
Structural Applications

ABSTRACTNb-silicide based composites have excellent potential for future high-temperature structural applications. Nb-silicide composites possess Nb together with high-strength silicides, such as Nb5Si3 and Nb3Si. Alloying elements such as Ti and Hf, are added to obtain a balance of properties such as creep performance and oxidation resistance. In Nb-silicide composites generated from Nb-rich binary Nb-Si alloys, Nb3Si is unstable and experiences eutectoid decomposition to Nb and Nb5Si3. The present paper describes a low temperature eutectoid phase transformation during which (Nb)3Si decomposes into (Nb) and (Nb)5Si3, where the (Nb)5Si3 possesses the hP16 structure, as opposed to the tI32 structure observed in binary Nb5Si3.

LUKENS LT-75HS

Alloy Digest ◽  
1968 ◽  
Vol 17 (11) ◽  
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
High Strength ◽  
Heat Treating ◽  
Strength Properties ◽  
Notch Toughness ◽  
Steel Company ◽  
Fine Grain ◽  
Temperature Performance ◽  
Structural Applications

Abstract Lukens LT-75HS is a quenched and tempered, fine grain, notch-tough, carbon steel having good impact and notch-toughness properties. It is engineered specifically for use in pressure vessel and structural applications requiring high strength properties and guaranteed notch toughness. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on low and high temperature performance as well as forming, heat treating, and joining. Filing Code: CS-28. Producer or source: Lukens Steel Company.

CRUCIBLE AFC-77

Alloy Digest ◽  
1968 ◽  
Vol 17 (5) ◽  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Martensitic Stainless Steel ◽  
High Strength ◽  
Heat Treating ◽  
Steel Company ◽  
Heat Treated ◽  
Structural Applications ◽  
Crucible Steel ◽  
Oxidation And Corrosion

Abstract Crucible AFC-77 is a precipitation-hardenable martensitic stainless steel which retains good mechanical properties at operating temperatures up to 1200 F. The alloy can be heat treated to high strength levels while exhibiting good oxidation and corrosion resistance. It is recommended for high temperature structural applications as well as hot work applications such as extrusion tooling, die casting dies and glass molds. This datasheet provides information on composition, physical properties, hardness, and tensile properties as well as fracture toughness and creep. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SS-209. Producer or source: Crucible Steel Company of America.

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.

Crystallization sequence of an A1N-Y2O3-SiO2 glass-ceramic

1986 ◽  
Vol 44 ◽  
pp. 446-447
Author(s):  
T.R. Dinger ◽  
G. Thomas
Keyword(s):  
High Temperature ◽  
Glass Ceramic ◽  
Crystallization Behavior ◽  
High Stress ◽  
Crystallization Sequence ◽  
Sio2 Glass ◽  
Structural Applications ◽  
Ceramic Precursors

The use of Si3N4, alloys for high temperature, high stress structural applications has prompted numerous studies of the oxynitride glasses which exist as intergranular phases in their microstructures. Oxynitride glasses have been investigated recently in their bulk form in order to understand their crystallization behavior for subsequent Si3N4 applications and to investigate their worth as glass-ceramic precursors. This research investigates the crystallization sequence of a glass having a normalized composition of Y26Si30Al11 ON11 and lying in the A1N-Y2O3-SiO2 section of the Y-Si-Al-O-N system. Such glasses exist as intergranular phases in the technologically important Y2O3/Al2O3-fluxed Si3N4 alloys.

In situ observation of the martensitic transformation in (Mg,Y)-PSZ

1986 ◽  
Vol 44 ◽  
pp. 500-501
Author(s):  
R-R. Lee
Keyword(s):  
Martensitic Transformation ◽  
High Strength ◽  
Nucleation And Growth ◽  
In Situ Observation ◽  
Considerable Potential ◽  
Transmission Electron ◽  
Structural Applications ◽  
Applied Stresses ◽  
Kinetics Of

Partially-stabilized ZrO2 (PSZ) ceramics have considerable potential for advanced structural applications because of their high strength and toughness. These properties derive from small tetragonal ZrO2 (t-ZrO2) precipitates in a cubic (c) ZrO2 matrix, which transform martensitically to monoclinic (m) symmetry under applied stresses. The kinetics of the martensitic transformation is believed to be nucleation controlled and the nucleation is always stress induced. In situ observation of the martensitic transformation using transmission electron microscopy provides considerable information about the nucleation and growth aspects of the transformation.

Electron energy loss near edge structures of intermetallic alloys and grain boundaries in NiAl

1996 ◽  
Vol 54 ◽  
pp. 522-523
Author(s):  
G.A. Botton ◽  
C.J. Humphreys
Keyword(s):  
High Temperature ◽  
Transition Metal ◽  
Energy Loss ◽  
Grain Boundaries ◽  
Industrial Applications ◽  
Edge Structure ◽  
Structural Applications ◽  
Yield Behaviour ◽  
Late Transition ◽  
Metal Aluminides

Transition metal aluminides are of great potential interest for high temperature structural applications. Although these materials exhibit good mechanical properties at high temperature, their use in industrial applications is often limited by their intrinsic room temperature brittleness. Whilst this particular yield behaviour is directly related to the defect structure, the properties of the defects (in particular the mobility of dislocations and the slip system on which these dislocations move) are ultimately determined by the electronic structure and bonding in these materials. The lack of ductility has been attributed, at least in part, to the mixed bonding character (metallic and covalent) as inferred from ab-initio calculations. In this work, we analyse energy loss spectra and discuss the features of the near edge structure in terms of the relevant electronic states in order to compare the predictions on bonding directly with spectroscopic experiments. In this process, we compare spectra of late transition metal (TM) to early TM aluminides (FeAl and TiAl) to assess whether differences in bonding can also be detected. This information is then discussed in terms of bonding changes at grain boundaries in NiAl.

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