Mechanical properties and structural characterization of carbon nanotube/alumina composites prepared by precursor method

Relationship between microstructure and mechanical properties in acid-treated carbon nanotube-reinforced alumina composites

“…Mixtures of 0.9, 1.9, and 3.7 vol% MWCNTs and alumina powder were prepared by a precursor method [21][22][23]. The details of composite preparation can be found in the Ref.…”

“…A vast majority of CNT composite studies have focused on polymer matrices [12], while comparatively few investigations have explored inorganic (ceramic and glass) matrices. In the last two decades, there has been growing interest in using CNTs in brittle ceramic monoliths, particularly as toughening agents in these otherwise strong and stiff materials [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. In addition, CNTs may have a significant influence on other properties such as electrical conductivity, thermal expansion coefficient, and hardness [13].…”

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

“…A great variety of conflicting results are reported in literature. In some works no reinforcement is observed [5][6][7] while in others fracture toughness (K IC ) increases [8][9][10][11][12][13][14][15][16], but no clear trend is found when changing the amount of CNTs.…”

“…Composites with lower SWNT content maintain the Vickers hardness of monolithic alumina, whereas it significantly decreases for the rest of compositions. 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.…”

Effects of processing conditions on microstructure, electrical conductivity and mechanical properties of MWCNT/alumina composites prepared by flocculation

“…This has seen the development of multifunctional composites become a key focus of ceramics research, with CNTs expected to not only have a favorable effect on fracture resistance, but also a positive influence on the thermal/electrical conductivity and tribological properties [5][6][7][8]. The effective utilization of the properties of CNTs does present a challenge though, in that clusters of CNTs have been reported to possess poor load-carrying ability and are therefore considered to have an effect similar to pores in a ceramic matrix [9]. This suggests that any increase in defect concentration with a higher CNT content could lead to a reduction in the mechanical properties, making it essential to achieve a homogeneous dispersion of CNTs within the matrix.…”