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, the multi-wall carbon nanotube (MWNT) and the single-wall carbon nanotube (SWNT). A SWNT is a graphene sheet rolled into a cylinder with typical diameter on the order of 1.4 nm. However, a MWNT consists of several concentric cylinders with diameters

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Abstract  

Many concerns over unsafe or unknown properties of multi-walled carbon nanotubes (MWNTs) have been raised. The thermal characteristics regarding stability would represent potential hazards during the production or utilization stage and could be determined by calorimetric tests for various thermokinetic parameters. Differential scanning calorimetry (DSC) was employed to evaluate the thermokinetic parameters for MWNTs at various compositions. Thermoanalytical curves showed that the average heat of decomposition (ΔH d) of the MWNTs samples in a manufacturing process was about 31,723 J g−1, by identifying them as an inherently hazardous material. In this study, significant thermal analysis appeared in the presence of sulfuric acid (H2SO4). From the DSC experiments, the purification process of MWNTs could induce an unexpected reaction in the condition of batch addition with reactants of H2SO4. The results can be applied for designing emergency relief system and emergency rescue strategies during a perturbed situation or accident.

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Thermogravimetric (TG) and varied temperature Raman spectroscopic measurements of melt-blended polypropylene composites (PP) with double wall (DWNT) and multi-wall carbon nanotubes (MWNT) revealed that the incorporation of carbon nanotubes into polymer matrix increased the thermal stability comparing to the virgin polypropylene. The characterization of reference nanotubes was also done by Raman microscopy and TG measurements. Varied temperature rheological analysis provided further information about the thermal decomposition of the composites indicating the formation of high strength char in case of MWNT and limited applicability of DWNT at high temperature. The residue of the decomposition of PP-MWNT nanocomposites consists of nanotubes of spectroscopically higher purity comparing to the original one indicating the thermally induced chemical changes in the solid phase.

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The effects of multi-walled carbon nanotubes (MWNTs) on the phase change enthalpy (ΔH) and the thermal conductivity (κ) of a solid-liquid phase change materials (PCM), palmitic acid (PA), have been investigated. The results showed that both the ΔH and the κ of the composite were lower than that of PA when the loading of MWNTs was small. As the concentration of MWNTs in the composites increased, the ΔH of the composites was slightly improved and then decreased linearly. However, the κ of the composites was monotonously increased from the minimum value. When the loading of MWNTs increased to 5% and no surfactant was added, the κ of the composite was enhanced to be 26% higher than that of PA. The κ of the composite could be enhanced by CTAB instead of SDBS when the loading of MWNTs was small, as SDBS showed no obvious effect on the κ of the composites. Furthermore, the effects of surface modification of MWNTs on the ΔH and the κ of the composites have also been investigated.

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The flow-induced crystallization behavior of nanocomposites, containing isotactic poly(1-butene) (PB) and functionalized multi-walled carbon nanotubes (MWNT), was investigated. Three different MWNT concentrations (0.1, 1, 5 wt%) were used to prepare the nanocomposites. Effects of MWNT and shear flow on the crystallization parameters were evaluated separately. Rheological measurements based on oscillatory shear revealed induction time and crystallization half-time at the quiescent state, where both parameters exhibited the nucleating effect of MWNT on PB. Rheological measurements based on steady-state shear flow and short-time shear flow revealed the evolution of molecular orientation, which was studied in both PB and its nanocomposites. A small increase in crystallization kinetic was recorded in PB under shear having moderate values of the Weissenberg (We) number. On the other hand, a dramatic synergistic effect of MWNT and shear was detected under the same shear conditions for nanocomposites. The optical microscopic images exhibited a clear transition from isotropic to row-like morphology in the case of nanocomposites under shear.

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Journal of Thermal Analysis and Calorimetry
Authors: Eudes Lorençon, Rodrigo G. Lacerda, Luiz O. Ladeira, Rodrigo R. Resende, André S. Ferlauto, Ulf Schuchardt, and Rochel M. Lago

charge transfer from naphthalene anion to CNTs followed by metal reduction [ 14 ]. In this report, this method was used to produce different carbon forms, i.e., SWNTs, multi-walled carbon nanotubes (MWNTs), and soot, decorated with Au nanoparticles with a

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, nanoparticles with high thermal conductivity have shown tremendous potential in heat transfer application [ 10 ]. Zeng et al. enhanced the thermal conductivity of PCMs by adding Ag nanoparticles [ 11 ], Ag nanowires [ 12 ] and multi-walled carbon nanotubes

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, Huang , HM 2011 Responses and thermal conductivity measurements of multi-wall carbon nanotube (MWNT)/epoxy composites . J Therm Anal Calorim 103 2 533 – 542 10.1007/s10973-010-1088-y . 16

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