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| Content Provider | Royal Society of Chemistry (RSC) |
|---|---|
| Author | Shen, Zhijian-j. Brown, Ian W. M. White, G. Vaughan Mackenzie, Kenneth J. D. Ekström, Thommy |
| Copyright Year | 1998 |
| Abstract | Simultaneous carboreduction and nitridation (CRN) of Y2O3 doped SiO2 /clay or elemental Si/clay mixes at atmospheric pressure were used to prepare low-cost powders of α-sialon composition. The synthesised products contained crystalline phase mixtures of α- and β-sialon and Y3Si6N11 . Subsequent hot pressing of the CRN powders at 1800 °C resulted in poorly densified materials from mixtures with low Y2O3 , whereas high Y2O3 gave dense ceramics. The addition of SiO2to the starting mix resulted in ceramics containing substantial amounts of very fine SiC particles distributed in a matrix of β-sialon and glass. Solid state MAS NMR indicates that the crystalline SiC observed by XRD after hot-pressing is also present in an XRD-amorphous form in the pre-pressed powders, and that hot-pressing causes the Al–N units to become overall more oxygenated, with the conversion of β-sialon to α-sialon and the formation of small amounts of polytypoid sialons. The hardness,HV10 , and fracture toughness, K1C , of the densified materials were ca. 18 GPa and 3 MPa m1/2 , respectively. The use of elemental Si produced less SiC, the major phase in these ceramics being α-sialon and a residual glassy phase observable by electron microscopy. The hardness and toughness of these densified materials was ca. 20 GPa and 3 MPa m1/2 , respectively. |
| Starting Page | 977 |
| Ending Page | 983 |
| Page Count | 7 |
| File Format | |
| ISSN | 09599428 |
| Volume Number | 8 |
| Issue Number | 4 |
| Journal | Journal of Materials Chemistry |
| DOI | 10.1039/a707729g |
| Language | English |
| Publisher | Royal Society of Chemistry |
| Access Restriction | Open |
| Subject Keyword | CRN Atmospheric pressure Hot pressing Composite material Magic angle spinning Nuclear magnetic resonance X-ray crystallography Fracture toughness Transmission electron microscopy |
| Content Type | Text |
| Resource Type | Article |
| Subject | Chemistry Materials Chemistry |
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