ChemInform Abstract: Crystallization Behavior and Polytype Transformation of Polymer- Derived Silicon Carbide.

ChemInform ◽  
2010 ◽  
Vol 28 (22) ◽  
pp. no-no
Author(s):  
H.-P. MARTIN ◽  
E. MUELLER ◽  
G. IRMER ◽  
F. BABONNEAU
Keyword(s):  
Silicon Carbide ◽  
Crystallization Behavior ◽  
Polytype Transformation

6H to 3C Polytype Transformation in Silicon Carbide

1999 ◽  
Vol 38 (Part 2, No. 1A/B) ◽  
pp. L27-L29 ◽  
Author(s):  
Svitlana I. Vlaskina ◽  
Dong Hyuk Shin
Keyword(s):  
Silicon Carbide ◽  
Polytype Transformation

Nonequiaxial Grain Growth and Polytype Transformation of Sintered α-Silicon Carbide and β-Silicon Carbide

2003 ◽  
Vol 86 (12) ◽  
pp. 2222-2224 ◽  
Author(s):  
Hidehiko Tanaka ◽  
Naoto Hirosaki ◽  
Toshiyuki Nishimura ◽  
Dong-Woo Shin ◽  
Sam-Shik Park
Keyword(s):  
Silicon Carbide ◽  
Grain Growth ◽  
Polytype Transformation

One of Many Sources of Defect Generation in SiC

2000 ◽  
Vol 640 ◽  
Author(s):  
Igor I. Khlebnikov ◽  
Tangali S. Sudarshan ◽  
Yuri I. Khlebnikov ◽  
Colin Wood
Keyword(s):  
Silicon Carbide ◽  
Grown Crystal ◽  
Stable Phase ◽  
Planar Defects ◽  
Defect Generation ◽  
Unique Material ◽  
Polytype Transformation ◽  
Many Sources ◽  
The Given ◽  
First Time

ABSTRACTSilicon carbide is a unique material for the study of process of defect generation and crystallization. In this paper, for the first time, we report the observation of the entrapment of whiskers and dendrites (tree-like defects) within the volume of the growing monocrystalline SiC. The encapsulation of the tree-like defects in the volume of the grown crystal leads to solid state polytype transformation. According to Oswald rule, the most probable transformation sequence is as follows: 2H→3C→xR→4H, 6H until a stable phase is established for the given conditions of crystal growth. We observe that the entrapments of tree-like defects are the source of SiC defects such as micropipes and planar defects. It is very likely that the above process is also the source of dislocations. Practically, every branch of the tree-like structure generates the above mentioned defects (micropipes, planar defects, etc.). Our investigation (by EDAX) shows that the chemical composition of the tree-like defect is the same as that of bulk SiC. In this paper, we will present the mechanism of the entrapment of the tree-like defects in the bulk crystal.

Crystallisation behaviour and polytype transformation of polymer-derived silicon carbide

1997 ◽  
Vol 17 (5) ◽  
pp. 659-666 ◽  
Author(s):  
Hans-Peter Martin ◽  
Eberhard Müller ◽  
Gert Irmer ◽  
Florence Babonneau
Keyword(s):  
Silicon Carbide ◽  
Crystallisation Behaviour ◽  
Polytype Transformation

Irradiation behavior of pyrolytic silicon carbide

1983 ◽  
Vol 41 ◽  
pp. 72-73
Author(s):  
R. J. Lauf
Keyword(s):  
Silicon Carbide ◽  
Fission Products ◽  
Thermodynamics And Kinetics ◽  
Neutron Fluences ◽  
Fuel Particles ◽  
Sic Coatings ◽  
Irradiation Behavior ◽  
Kinetics Of ◽  
Htgr Fuel

Fuel particles for the High-Temperature Gas-Cooled Reactor (HTGR) contain a layer of pyrolytic silicon carbide to act as a miniature pressure vessel and primary fission product barrier. Optimization of the SiC with respect to fuel performance involves four areas of study: (a) characterization of as-deposited SiC coatings; (b) thermodynamics and kinetics of chemical reactions between SiC and fission products; (c) irradiation behavior of SiC in the absence of fission products; and (d) combined effects of irradiation and fission products. This paper reports the behavior of SiC deposited on inert microspheres and irradiated to fast neutron fluences typical of HTGR fuel at end-of-life.

Microstructural Evaluation of Silicon Carbide Whisker Reinforced Alumina Fabricated with Carbon-Coated Whiskers

1991 ◽  
Vol 49 ◽  
pp. 920-921
Author(s):  
K. B. Alexander ◽  
P. F. Becher
Keyword(s):  
Silicon Carbide ◽  
High Resolution Electron Microscopy ◽  
Ceramic Composites ◽  
Interface Debonding ◽  
Resolution Electron ◽  
Microstructural Evaluation ◽  
Carbon Coated ◽  
Electron Energy Loss ◽  
Interfacial Films ◽  
Debonding Process

The presence of interfacial films at the whisker-matrix interface can significantly influence the fracture toughness of ceramic composites. The film may alter the interface debonding process though changes in either the interfacial fracture energy or the residual stress at the interface. In addition, the films may affect the whisker pullout process through the frictional sliding coefficients or the extent of mechanical interlocking of the interface due to the whisker surface topography.Composites containing ACMC silicon carbide whiskers (SiCw) which had been coated with 5-10 nm of carbon and Tokai whiskers coated with 2 nm of carbon have been examined. High resolution electron microscopy (HREM) images of the interface were obtained with a JEOL 4000EX electron microscope. The whisker geometry used for HREM imaging is described in Reference 2. High spatial resolution (< 2-nm-diameter probe) parallel-collection electron energy loss spectroscopy (PEELS) measurements were obtained with a Philips EM400T/FEG microscope equipped with a Gatan Model 666 spectrometer.

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.

TEM of grain growth and phase transformations during creep of SCS-6 silicon carbide fibers

1995 ◽  
Vol 53 ◽  
pp. 350-351
Author(s):  
L. A. Giannuzzi ◽  
C. A. Lewinsohn ◽  
C. E. Bakis ◽  
R. E. Tressler
Keyword(s):  
Silicon Carbide ◽  
Creep Rate ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Primary Creep ◽  
Excess Carbon ◽  
Silicon Carbide Fibers ◽  
Sic Fiber ◽  
Carbon Core ◽  
Grain Width

The SCS-6 SiC fiber is a 142 μm diameter fiber consisting of four distinct regions of βSiC. These SiC regions vary in excess carbon content ranging from 10 a/o down to 5 a/o in the SiC1 through SiC3 region. The SiC4 region is stoichiometric. The SiC sub-grains in all regions grow radially outward from the carbon core of the fiber during the chemical vapor deposition processing of these fibers. In general, the sub-grain width changes from 50nm to 250nm while maintaining an aspect ratio of ~10:1 from the SiC1 through the SiC4 regions. In addition, the SiC shows a <110> texture, i.e., the {111} planes lie ±15° along the fiber axes. Previous has shown that the SCS-6 fiber (as well as the SCS-9 and the developmental SCS-50 μm fiber) undergoes primary creep (i.e., the creep rate constantly decreases as a function of time) throughout the lifetime of the creep test.

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