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Microstructural analysis of silicon carbide monofilaments
R. A. Shatwell1, K. L. Dyos, C. Prentice
1Mechanical Sciences Sector, DERA Farnborough, Hampshire, GU14 0LX, U.K.; Manchester Materials Science Centre, UMIST/University of Manchester, Manchester, M1 7HS, U.K.
Journal of Microscopy
|February 24, 2001
Summary
Raman spectroscopy is a cost-effective method to analyze silicon carbide (SiC) monofilaments, complementing transmission electron microscopy (TEM). This technique reveals amorphous carbon and silicon, and crystallite orientation, crucial for understanding SiC monofilament properties.
Area of Science:
- Materials Science
- Nanotechnology
- Ceramics Engineering
Background:
- Understanding process-property relationships in monofilaments is vital for material development.
- Transmission electron microscopy (TEM) is effective but limited by speed and cost for routine analysis.
- Investigating alternative, economical techniques is necessary for microstructure characterization.
Purpose of the Study:
- To evaluate Raman spectroscopy as a complementary technique to TEM for SiC monofilament analysis.
- To characterize the microstructure of SiC monofilaments using multiple analytical methods.
- To correlate microstructural features with material properties and processing.
Main Methods:
- Comparative analysis using Transmission Electron Microscopy (TEM), Electron Microprobe Analysis, Raman Microprobe Analysis, Thermogravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC).
- Raman spectroscopy to identify amorphous carbon (C) and silicon (Si) phases.
- TGA and DSC to study thermal behavior and reactions with gaseous species.
- Polarized Raman scattering to determine crystallite orientation.
Main Results:
- Raman spectroscopy successfully identified amorphous C and Si, which were undetectable by electron or X-ray diffraction.
- Differential Scanning Calorimetry (DSC) detected free silicon in DERA Sigma SM1140+ at ~1400°C.
- Thermogravimetric Analysis (TGA) revealed oxidation behavior: Textron SCS-6 and Ultra-SCS lost weight (C oxidation), while Sigma gained weight (SiO2 formation).
- Raman peak separations correlated with stacking fault density in SiC crystallites.
- Polarized Raman scattering indicated a predominant <111> crystallite orientation along the radius for SM1140+ and SCS-6, with potential mixed orientations in Ultra-SCS.
Conclusions:
- Raman spectroscopy is a valuable, cost-effective tool for characterizing SiC monofilaments, offering complementary information to TEM.
- The study elucidated phase composition, thermal stability, and crystallite orientation in different SiC monofilaments.
- Findings provide insights into SiC monofilament microstructure, aiding in process optimization and material design.