Processing and properties of aligned multi-walled carbon nanotube/aluminoborosilicate glass composites made by sol–gel processing

Understanding the mechanical reinforcement of uniformly dispersed multiwalled carbon nanotubes in alumino-borosilicate glass ceramic

“…"Sword-in-sheath"-type failures usually occur when the outer walls of the nanotubes bear most of the load and fail, while the inner walls remain intact and tend to get "telescoped" out due to the weak inter-wall bonding of MWCNTs. Such a failure mode would have resulted in the protruding MWCNTs having diameters smaller than the diameter of the as-functionalized MWCNTs, along with tapering towards the ends of the protruding sections [36], and the appearance of smoother inner walls (devoid of adhering glass), at least near the broken ends [36], which are contrary to our observations. Additionally, we note that the SEM micrograph in Fig.…”

“…This has the added attraction of explaining why "sword-in-sheath" fail- ure is not observed in the sense that not only is premature failure favoured in the section between the crack faces, but also the inner layers of the MWCNT are clamped in place at the buckling site, preventing the "telescoping" of the inner tubes. This hypothesis has strong support from recent observations of aligned MWCNTs in a very similar glass matrix [36]. Alignment normal to the crack plane would not lead to such buckling and stress concentrations, and in this case [36] pull-out of relatively long lengths of MWCNT ($1 lm), holes in the fracture surface and "sword-in-sheath" failure were all observed in abundance.…”

“…This hypothesis has strong support from recent observations of aligned MWCNTs in a very similar glass matrix [36]. Alignment normal to the crack plane would not lead to such buckling and stress concentrations, and in this case [36] pull-out of relatively long lengths of MWCNT ($1 lm), holes in the fracture surface and "sword-in-sheath" failure were all observed in abundance. There have also been reports of extensive pull-out of MWCNTs from ceramic matrices in aligned composites [42].…”

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

“…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].…”

Ceramic composites from mesoporous silica coated multi-wall carbon nanotubes

“…The synthesis of mesoporous silica was adapted from a previously described method [5]. Briefly, 4.0 g P85 (BASF) in 120 ml of 2 M HCl (Aldrich 37%) and 30 ml deionised H 2 O was stirred for 30 min.…”