Hardness and flexural strength of single-walled carbon nanotube/alumina composites
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This work adds new experimental facts on room temperature hardness and flexural strength of alumina and composites with 1, 2, 5 and 10 vol% single-walled carbon nanotubes (SWNT) with similar grain size. Monolithic Al2O3 and composites were spark plasma sintered (SPS) in identical conditions at 1300 °C, achieving high density, submicrometric grain size and a reasonably homogeneous distribution of SWNT along grain boundaries for all compositions with residual agglomerates. Vickers hardness values comparable to monolithic alumina were obtained for composites with low (1 vol%) SWNT content, though they decreased for higher concentrations, attributed to the fact that SWNT constitute a softer phase. Three-point bending flexural strength also decreased with increasing SWNT content. Correlation between experimental results and microstructural analysis by electron microscopy indicates that although SWNT agglomerates have often been blamed for detrimental effects on the mechanical properties of these composites, they are not the main cause for the reported decay in flexural strength.
KeywordsFracture Toughness Flexural Strength Spark Plasma Sinter Alumina Matrix Ceramic Matrix
This work was financed by Spanish Ministry of Science and Innovation (MAT2009-11078 and MAT2012-34217) and by Junta de Andalucía (P12-FQM-1079). Microscopy studies were performed at CITIUS facilities (Universidad de Sevilla).
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