Aqueous colloidal processing of single-wall carbon nanotubes and their composites with ceramics

Abstract

A unique combination of acid treatment, aqueous colloidal processing, and spark-plasma sintering (SPS) has been used to fabricate high-density Al2O3 /single-wall carbon nanotube (SWNT) composites with well-distributed SWNTs and other carbon nanostructures ('nano-onions', diamond) at Al2O3 grain boundaries. This approach could be used to obtain well-controlled microstructures of ceramic/SWNT composites for tailored mechanical, electrical, and thermal properties. In addition, the colloidal approach for dispersing SWNTs presented here could be used for the controlled manipulation of SWNTs.

Improvement of Vickers hardness measurement on SWNT/Al2O3 composites consolidated by spark plasma sintering

“…Dark regions are composed by SWNTs as confirmed by Raman spectroscopy (not shown). Similar microstructure has been previously observed in other 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 SWNT/Al 2 O 3 composites [6,19,20]. In MWNT/Al 2 O 3 nanocomposites only Huang et al…”

“…% SWNT) were prepared from α-alumina powder (99% purity and 30-40 nm particle size) supplied by Nanostructured and specifically developed to achieve a highly homogeneous distribution of SWNTs at ceramic grain boundaries [19].…”

“…Although aqueous colloidal processing has been assessed as an efficient technique producing adequate dispersion of CNTs throughout ceramic matrix grain boundaries after sintering [18][19][20], the presence of agglomerates seems to be unavoidable.…”

“…The decreasing trend with increasing SWNT content has been explained by the presence of higher SWNT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Heterogeneous dispersion and distribution of CNTs in the ceramic matrix, poor chemical compatibility between CNTs and alumina hindering effective transfer load and the large differences in the scales of the matrix microstructure and the carbon nanotubes have been stated as main obstacles to transfer the desirable CNT mechanical properties to the brittle ceramic matrix [5,7,11,14,15]. Adequate dispersion of CNTs is very difficult owing to their tendency to form bundles in order to minimize their surface area.Although aqueous colloidal processing has been assessed as an efficient technique producing adequate dispersion of CNTs throughout ceramic matrix grain boundaries after sintering [18][19][20], the presence of agglomerates seems to be unavoidable.Recently, Poorteman et al [21] fabricated MWNT/alumina composites with low MWNT content (0.6 and 1.4 vol. %) by a colloidal processing route to optimize electrostatic…”

Ceramic matrix composites containing carbon nanotubes

“…These acidic groups electrostatically stabilize the CNTs in water, or other polar liquids, by developing a negative surface charge. Similar effects occur for both MWCNTs 74 and SWCNTs 75 . The resulting electrostatic repulsion among the CNTs leads to a remarkable increase in the stability of the colloidal suspension 76 .…”