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Abstract Carbon multi-walled nanotubes (C-MWNTs) and alternatively carbon double-walled nanotubes (C-DWNTs) were added in water, following our previous work, in order to enhance the thermal conductivity of this traditional heat transfer fluid. Hexadecyltrimethyl ammonium bromide (CTAB) and Nanosperse AQ were employed as dispersants. The transient hot-wire technique was used for the measurement of the thermal conductivity with an instrument built for this purpose. The absolute uncertainty is better than 2%. The maximum thermal conductivity enhancement obtained was 34% for a 0.6% volume C-MWNT suspension in water with CTAB. All measurements were made at ambient temperature. In an attempt to evaluate and explain the experimental results, information about the microstructure of the suspensions is needed. The findings of these investigations are presented here along with the analysis. [ABSTRACT FROM AUTHOR]

This study reports a novel approach for growing multilayer thin films consisting of alternate layers of carbon nanotubes (CNT) and nickel on Si (1 0 0) substrates and justifies their use in thin film temperature sensors. A low pressure chemical vapor deposition system was employed for synthesizing CNT films, while Ni films were deposited by electrodeposition. Porous-Si was used as substrate to increase adhesion between the layers of the multilayer structure. The structure of the multilayer films and the quality of the CNT grown were analyzed using several characterization methods, including scanning electron microscopy, x-ray photoelectron spectroscopy, x-ray auger electron spectroscopy and Raman spectroscopy. The electrical characteristics were investigated using a van der Pauw setup and the effect of the increasing number of CNT layers in the multilayer structure was studied. The sensitivity of the multilayer film was found to increase with increasing number of CNT layers, despite the decrease of the temperature coefficient of resistance. On the other hand, the initial resistance was found to increase. Results indicated that these multilayer structures are appropriate for fabricating highly sensitive thin film gauges that can detect lower heat fluxes with more accuracy. [ABSTRACT FROM AUTHOR]