Polymer-Derived Silicon Carbide Fibers with Improved Thermomechanical Stability

1992 ◽  
Vol 271 ◽  
Author(s):  
W. Toreki ◽  
C. D. Batich ◽  
M. D. Sacks ◽  
M. Saleem ◽  
G. J. Choi
Keyword(s):  
Silicon Carbide ◽  
Polymer Fibers ◽  
Low Oxygen ◽  
X Ray Diffraction ◽  
Silicon Carbide Fibers ◽  
Surface Areas ◽  
Weight Losses ◽  
Dry Spinning ◽  
Scanning Auger Microprobe ◽  
Strength Retention

ABSTRACTContinuous silicon carbide fibers (”UF fibers”) with low oxygen content (∼2 wt%) were prepared by dry spinning of high molecular weight polycarbosilane solutions and subsequent pyrolysis of the polymer fibers. Room temperature mechanical properties were similar to those of commercially-available Nicalon™ fibers, as average tensile strengths as high as 3 GPa were obtained for some batches with fiber diameters in the range ∼10–15 μm Furthermore, UF fibers showed significantly better thermomechanical stability compared to Nicalon™, as indicated by lower weight losses, lower specific surface areas, and improved strength retention after heat treatment at temperatures up to 1700°C. UF fibers were also characterized by elemental analysis, X-ray diffraction, and scanning Auger microprobe. Strategies were suggested for achieving further improvements in thermomechanical stability.

Polymer-Derived Silicon Carbide Fibers with Near-Stoichiometric Composition and Low Oxygen Content

1994 ◽  
Vol 365 ◽  
Author(s):  
Michael D. Sacks ◽  
Gary W. Scheiffele ◽  
Mohamed Saleem ◽  
Gregory A. Staab ◽  
Augusto A. Morrone ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Oxygen Content ◽  
Stoichiometric Composition ◽  
Alpha Phase ◽  
Minor Amount ◽  
Low Oxygen ◽  
Silicon Carbide Fibers ◽  
Fine Grain ◽  
Transmission Electron ◽  
A Minor

ABSTRACTFine-diameter (∼ 10–15 µm), polymer-derived SiC fibers were characterized. The average tensile strength of the fibers was ∼ 2.8 GPa, although some lots had average strengths exceeding 3.5 GPa. Microstructure observations showed that fibers had fine grain sizes (mostly ∼0.05–0.2 µm), high densities (∼3.1–3.2 g'cm3), and small residual pore sizes (≤0.1 µm). Elemental analysis showed that fibers had near-stoichiometric composition. Electron and X-ray diffraction analyses indicated that fibers were primarily beta silicon carbide, with a minor amount of the alpha phase. A small amount of graphitic carbon was detected in some samples using high resolution transmission electron microscopy. The residual oxygen content in the fibers was ≤0.1 wt%. Fibers exhibited good thermomechanical stability, as heat treatment at 1800°C for 4h in argon resulted in only an ∼ 8% decrease in strength.

Polymer-derived silicon carbide fibers with low oxygen content and improved thermomechanical stability

1994 ◽  
Vol 51 (2) ◽  
pp. 145-159 ◽  
Author(s):  
William Toreki ◽  
Christopher D Batich ◽  
Michael D Sacks ◽  
Mohamed Saleem ◽  
Guang J Choi ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Oxygen Content ◽  
Low Oxygen ◽  
Silicon Carbide Fibers

scholarly journals Materials Stress Diagnostics by X-Ray and Acoustic Techniques

2014 ◽  
Vol 59 (2) ◽  
pp. 437-441 ◽  
Author(s):  
J.T. Bonarski ◽  
L. Tarkowski ◽  
S. Pawlak ◽  
A. Rakowska ◽  
Ł. Major
Keyword(s):  
Silicon Carbide ◽  
Extreme Values ◽  
Acoustic Tomography ◽  
Structural Elements ◽  
X Ray Diffraction ◽  
Near Surface ◽  
X Ray ◽  
Surface Areas ◽  
Acoustic Techniques ◽  
Calculation Procedures

Abstract Performed investigations and obtained results concerned the analysis of residual stresses in near-surface areas of coppercorundum (Cu-Al2O3) composite and silicon carbide (SiC) samples. X-ray diffraction and acoustic tomography techniques, as well as the suitable calculation procedures, allowed to locate sample-areas with extreme values of stresses residing in the examined materials. The registered texture-stress characteristics reflects inhomogeneity of the samples structure identified by means of acoustic tomography. Obtained results provide valuable information on anisotropy of physical properties of structural elements produced by the technologies applied to the examined samples.

Oxidation of Low-Oxygen Silicon Carbide Fibers (Hi-Nicalon) in Carbon Dioxide

2001 ◽  
Vol 84 (12) ◽  
pp. 2975-2980 ◽  
Author(s):  
Toshio Shimoo ◽  
Takehiro Morita ◽  
Kiyohito Okamura
Keyword(s):  
Carbon Dioxide ◽  
Silicon Carbide ◽  
Low Oxygen ◽  
Silicon Carbide Fibers

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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