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Journal of Thermal Analysis and Calorimetry
Authors: A. Andreescu, Adriana Savin, Rozina Steigmann, Nicoleta Iftimie, E. Mamut, and R. Grimberg

Abstract  

This paper presents a model for evaluation of effective thermal conductivity for the composites with carbon nanotubes (CNT) having log-normal function of distribution of CNT, with direct effect over depolarization factor. The CNT are considered having cylindrical shape with L/d ratio very high. The model parameters are calculated in function of the data from literature. The influence of volume fraction of reinforced materials, of the aspect ratio of the particles included and of the ratio of the two thermal conductivities is presented.

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Abstract  

One of the greatest challenges in the application of organic phase change materials (PCMs) is to increase their thermal conductivity while maintaining high phase change enthalpy. 1-Tetradecanol/Ag nanowires composite PCM containing 62.73 wt% (about 11.8 vol%) of Ag nanowires showed remarkably high thermal conductivity (1.46 W m−1 K−1) and reasonably high phase change enthalpy (76.5 J g−1). This behavior was attributed to the high aspect ratio of Ag nanowires, few thermal conduct interfaces, and high interface thermal conductivity of Ag nanowires in the composite PCM. These results indicated that Ag nanowires might be strong candidates for thermal conductivity enhancement of organic PCMs.

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We describe the direct, conformal, atomic layer deposition (ALD) of silica onto carbon nanotubes (CNTs) in the microfabrication of thinlayer chromatography (TLC) plates. As before, these plates were prepared with zig-zag hedge and channel microstructures, with high aspect ratio, porous hedges. After ALD, scanning electron microscopy (SEM) showed an increase in the radius of the CNTs of 8–40 nm. X-ray photoelectron spectroscopy (XPS) showed that the plates were composed almost entirely of silicon and oxygen, without contamination of metals or other elements that might compromise chromatographic performance, e.g., aluminum. Time-of-flight secondary ion mass spectrometry confirmed the extremely low level of aluminum in the plates. The final TLC layer thickness was ca. 50 μm. Separations of a test mixture of dyes from CAMAG (Muttenz, Switzerland) on an uncoated silica plate under traditional, normal phase conditions gave efficiencies of 40,000–140,000 plates m−1 with migration distances ranging from 2 to 36 mm. A separation of two fluorescent dyes, eosin Y disodium salt and sulforhodamine B, on an amino silane-coated plate gave efficiencies of ca. 170,000 and 200,000 plates m−1, with hR F values of 76 and 88, respectively. Run times on these new plates were much faster than on conventional TLC plates.

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(including aspect ratio), particle size and particle size distribution and internal cavities. The effect of surface roughness development is only briefly considered here as a more detailed analysis of this factor will be presented in a separate communication

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that acts as a heat shield for composites. Consistent with this mechanism, the flame retardancy was found to improve with better dispersion and a higher interface area (aspect ratio) of the nanotubes at desired loading. However, the major hurdle

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modern ferroelectrics . Science . 315 : 954 – 963 10.1126/science.1129564 . 4. Yang , Y , Wang , XH , Sun , CK , Li , LT . 2008 . Photoluminescence of high aspect-ratio PbTiO 3

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Introduction The carbon nanofibers not only have a low-density, high modulus, high strength and high electrical conductivity and thermal stability, and other characteristics, but also have a very small number of defects, aspect

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been the topics of very active research fields over the last decade [ 14 – 16 ]. CNTs possess high flexibility, low mass density, and large aspect ratio (typically >1,000), whereas the predicted and some experimental data indicate extremely high tensile

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inorganic groups of P. Schmuki (Nuernberg-Erlangen University) and R. Tenne (Weizmann Institute of Science), respectively. Due to the high aspect ratio (NT height-to-width ratio) of WS 2 NT confinement effects, very similar to what was already known for

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Table 2 . The microstructures of the glass ceramics presented in Fig. 3 also showed significant differences. LAS-A had a microstructure made up a number of low aspect ratio plates between 8–14 μm in length and about 1–2 μm in thickness. In contrast

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