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Lookup NU author(s): Emeritus Professor Derek Thompson
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SIC nanoparticles were added to a range of rare-earth doped Ln-sialon (Ln = Nd, Dy, Yb) ceramics to prepare a series of increased hardness sialon/SiCp composites. The composites, of overall composition Ln(0.33)Si(9.3)Al(2.7)O(1.7)N(14.3) and containing 10 and 20 wt.% of SiC particles, were sintered by hot-pressing at 1800 degrees C and then heat-treated at 1450 degrees C to modify the microstructure and properties by alpha double left right arrow beta sialon transformation. Enhanced hardness was found in proportion to the content of SiC particles and with increasing alpha:beta sialon phase ratio in the matrix. The kind of grain boundary phases which occurred also affected the results. In Nd-densified samples with or without SiC particles, the alpha-sialon phase was unstable under the heat-treatment conditions used and transformed substantially to beta-sialon in elongated grain morphology, with Nd-melilite phase as the dominant grain boundary crystalline phase. These materials were tough with a highest indentation fracture toughness K-1C of 7.0 MPa m(1/2). In contrast, Dy- and Yb-densified samples with or without SiC addition showed good stability for the alpha-sialon phase under the same conditions, with only a small amount of beta-sialon phase produced and Dy- or Yb-garnet as the main grain boundary phase. These composites were hard and brittle with a maximum Vickers hardness HV10 of 20 GPa. (C) 1999 Elsevier Science S.A. All rights reserved.
Author(s): Liu Q, Gao L, Yan DS, Thompson DP
Publication type: Article
Publication status: Published
Journal: Materials Science and Engineering A: Structural Materials: Properties, Microstructures and Processing
Year: 1999
Volume: 269
Issue: 1-2
Pages: 1-7
Print publication date: 11/08/1999
ISSN (print): 0921-5093
ISSN (electronic): 1873-4936
Publisher: Elsevier SA
URL: http://dx.doi.org/10.1016/S0921-5093(99)00144-6
DOI: 10.1016/S0921-5093(99)00144-6
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