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In situ synthesis of carbon nanotubes (CNTs) on Ti powder decorated with Ni catalyst enabled us to obtain a high-quality CNTs/Ti composite powder via fluidized bed chemical vapor deposition (FBCVD) process. The composite powder was characterized by a combination of high structural integrity and uniform dispersion of CNTs, which is not obtained by traditional ball-milling route. These advantages enabled the retention of CNTs in the near-fully dense titanium matrix composite (TMC), together with the uniform dispersion of TiC particles. The CNTs and TiC particles coordinated with each other and contributed to a synergistic effect involving load transfer from the matrix to CNTs and dispersion strengthening of TiC particles. The nanotube–particle-reinforced TMC exhibited superior mechanical properties in comparison to single-phase-reinforced TMCs. The catalytic behavior of Ni, controllable synthesis of CNTs, the retention behavior of CNTs, and the formation mechanism of TiC particles during the sintering process are discussed in detail. [ABSTRACT FROM AUTHOR]

External catalysts are commonly pre-coated on Ti alloy powders for in situ synthesis of carbon nanotubes (CNTs) to resolve the inhomogeneity issue, but their excessive introduction changes the matrix composition. Here, we activated the catalytic function of trace Fe impurity solid solute in Ti-6Al-4V powders to plant CNTs within the Ti-6Al-4V powders without modifying the composition. These CNTs exhibited high reactivity with Ti, were retained in the consolidated composites, and improved the mechanical properties. [ABSTRACT FROM AUTHOR]

The present study is in sequel to the previous research (Phys. Chem. Chem. Phys. 16 (2014) p. 19122), where a solution-based nucleation and growth approach that involved direct epitaxial nucleation of nanofibres of poly(3-hexylthiophene) (P3HT) on carbon nanotubes (CNTs) for potential use as next-generation building blocks for applications including field-effect transistors and photovoltaic devices, was described. Also presented was a theoretical analysis of epitaxial mechanism of nucleation and growth of semiconducting conjugated polymers notably, P3HT on CNTs. In the present study, we elucidate the impact of molecular weight of P3HT on structural morphology and photophysical properties. The change in average molecular weight of P3HT from ~14 to ~60 kDa resulted in several structural changes, even though the mechanism of nucleation and growth continued to be epitaxial process. In the case of high-molecular weight P3HT, the crystallized fibrils were ~200–400 nm in length and ~2–3-nm thick. In contrast, for the low molecular weight, the fibrils were significantly longer (>5 μm) in length and ~800–1000-nm thick, which are envisaged to involve chain folding in relation to shorter fibrils. Furthermore, the graft density of fibrils crystallized on CNTs was remarkably higher for the high-molecular weight P3HT such that the connectivity between successive fibrils is anticipated to be through very small tie-molecules. On the other hand, the graft density of low-molecular weight P3HT crystallized on CNTs was low. Thus, the interconnectivity between successive fibrils is anticipated to involve large tie-molecules. The differences in connectivity between successive fibrils (besides the structural morphology), for low- and high-molecular weight P3HT, would at least, in part, impact the charge carrier mobility. [ABSTRACT FROM AUTHOR]

The dispersion of carbon nanotubes (CNTs) in polypropylene (PP) introduces a significant change in the structure and phase evolution during crystallisation at ambient and elevated pressures. The differences between the behaviours of PP and PP containing CNTs are attributed to CNT/polymer interface driven nucleation, which is also responsible for the significant reduction in spherulite size and is associated with the change in equilibrium melting point and percentage crystallinity. This opens the gateway for the use of polymer CNT composites for functional devices, including biomedical and electronic devices. A study of the impact of 1 wt-%CNT additions on the microstructure evolution of PP during pressure induced crystallisation is reported. It is demonstrated that the dispersion of CNTs produces a significant difference in the macromolecular structure and phase evolution during crystallisation at ambient and elevated pressures. The change in equilibrium melting point with pressure is higher for PP containing CNT, which is indicative of the chemical interaction between polymer and CNT. It is found that CNT additions promote the formation of γ-phase at low crystallisation pressure of 0·1-25 MPa, in contrast to the neat PP where α-crystals nucleate at low to moderate pressures (about 0·1-60 MPa) and the γ-phase nucleates at crystallisation pressures exceeding ∼60 MPa. The dependence of equilibrium melting temperature on crystallisation pressure and spherulite size delineates two distinct regimes, characterised predominantly by α- and γ-phases respectively, for both PP and PP-CNT systems. [ABSTRACT FROM AUTHOR]

Here, we elucidate the significant impact of carbon nanotubes (CNTs) on the electrochemical behavior of Mg-based amorphous composite materials that were reinforced with CNTs while using pressure die casting. The addition of 3 vol % CNTs led to an increase in the compressive strength of Mg-based amorphous material from 812 MPa to 1007 MPa, and the fracture strain from 1.91% to 2.67% in the composite. Interestingly, the addition of CNTs significantly contributed to the enhancement of corrosion resistance of Mg-based glass by ~30%. The superior mechanical properties are primarily related to the fact that the addition of CNTs hindered the growth of shear bands (cracks), while the high corrosion resistance is related to inferior wettability and the bridging effect between adherent corrosive oxide film and the matrix that provided enhanced corrosion resistance. [ABSTRACT FROM AUTHOR]