Please use this identifier to cite or link to this item:
http://theses.ncl.ac.uk/jspui/handle/10443/1949
Title: | Silicon carbide alloys |
Authors: | Patience, Margaret MacDonald |
Issue Date: | 1983 |
Publisher: | Newcastle University |
Abstract: | Structure determination of a calcium ɑ'-sialon containing 1.8 calcium atoms per unit cell shows that these atoms occupy the two large interstitial sites in the structure. The carbothermal reduction of ɑ'-sialons results in silicon carhide-aluminium nitride alloys with the wurtzite-type structure. A more direct method of firing powder mixtures of silicon nitride, aluminium nitride, carhon and calcium oxide in the temperature range 1650-2100 C° is explored. Phase relationships in the silicon carbide-aluminium nitride system have been determined up to 2100°C and contrary to previous reports there is a miscihility gap extending from about 40 m/o to 84 m/o aluminium nitride at 1800°C. 2H-SiC formed at the silicon carbide-rich end of the system by the reaction of silicon nitride with carbon at 1650°C contains up to 12 a/o nitrogen which stabilizes it relative to other polytypes. At higher temperatures, 2H transforms to 3C which is itself stabilized by nitrogen and, unlike nitrogen-free 3C, does not transform to 6H below 2l00°C. The phases produced by high-temperature reaction and heat-treatment are characterized by X-ray diffraction, scanning electron microscopy and chemical analysis. High resolution electron microscopy is used to examine structural details and particularly to follow the 2H→3C transformation in silicon carbide alloys. |
Description: | PhD Thesis |
URI: | http://hdl.handle.net/10443/1949 |
Appears in Collections: | School of Chemical Engineering and Advanced Materials |
Files in This Item:
File | Description | Size | Format | |
---|---|---|---|---|
Patience, M.pdf | Thesis | 16.01 MB | Adobe PDF | View/Open |
dspacelicence.pdf | Licence | 43.82 kB | Adobe PDF | View/Open |
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.