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| SEM image of diamond - SiC composites. [Author: mkwiel] |
Below you can find a small fragment of my article about SiC nanowires. It is published in Diamond & Related Materials 17 (2008) 84–89
Raman spectroscopy has been successfully used to evaluate stress in chemical vapor deposited diamond films [1–5]. The technique has been used by many authors and is attractive because it is non-destructive, requires little sample preparation, and when combined with a confocal microscope it can probe an area as small as 1 micron in diameter. The Raman diamond F2g peak frequency position and broadening have been used to evaluate stress in diamond films. Stress mapping of CVD diamond has been obtained by scanning a laser beam across the sample [5]. Despite considerable success of that method in stress characterization in CVD films, no attempt has been made to study stress in diamond composites. Diamond–silicon carbide composites are produced under high pressure, high temperature conditions, usually by the infiltration technique [6,7]. Diamond powder is placed on top of the silicon layer and then the system is compressed to about 8 GPa and temperature is raised to a value above the melting point of silicon. Liquid silicon penetrates pores between diamond crystals, reaching even the smallest cavities due to external pressure and strong capillary forces. When diamond crystals are surrounded by silicon they are believed to be under hydrostatic conditions. Silicon reacts with carbon atoms from the diamond phase forming silicon carbide. Because of different densities of silicon carbide and silicon the volume of the system changes and diamond crystals are no longer under pure hydrostatic conditions. Furthermore, differences in thermal expansion coefficients of diamond and silicon carbide and their different compressibilities strain diamond composites when temperature and pressure in the reaction chamber are decreased.
Raman spectroscopy has been successfully used to evaluate stress in chemical vapor deposited diamond films [1–5]. The technique has been used by many authors and is attractive because it is non-destructive, requires little sample preparation, and when combined with a confocal microscope it can probe an area as small as 1 micron in diameter. The Raman diamond F2g peak frequency position and broadening have been used to evaluate stress in diamond films. Stress mapping of CVD diamond has been obtained by scanning a laser beam across the sample [5]. Despite considerable success of that method in stress characterization in CVD films, no attempt has been made to study stress in diamond composites. Diamond–silicon carbide composites are produced under high pressure, high temperature conditions, usually by the infiltration technique [6,7]. Diamond powder is placed on top of the silicon layer and then the system is compressed to about 8 GPa and temperature is raised to a value above the melting point of silicon. Liquid silicon penetrates pores between diamond crystals, reaching even the smallest cavities due to external pressure and strong capillary forces. When diamond crystals are surrounded by silicon they are believed to be under hydrostatic conditions. Silicon reacts with carbon atoms from the diamond phase forming silicon carbide. Because of different densities of silicon carbide and silicon the volume of the system changes and diamond crystals are no longer under pure hydrostatic conditions. Furthermore, differences in thermal expansion coefficients of diamond and silicon carbide and their different compressibilities strain diamond composites when temperature and pressure in the reaction chamber are decreased.
In this study we use Raman microspectroscopy of diamond crystals in composites to provide information on the magnitude and distribution of residual stress and apply the results to optimize sintering conditions. We will discuss the effects of the sintering parameters such as pressure, temperature, and the initial crystal size of diamond powder on residual stress in composites.
If you are interested of full text of this article, please let me know in comments, write your email and I will sent it to you. Best Regards.
If you are interested of full text of this article, please let me know in comments, write your email and I will sent it to you. Best Regards.
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