M. Mayne-L’Hermite

Thermal and electrical conductivities of water-based nanofluids prepared with long multiwalled carbon nanotubes

Thermal and electrical conductivities of suspensions of multiwalled carbon nanotubes (MWCNT) in water were measured as a function of temperature, nanotube weight content, and nanotube length. Nanotubes were dispersed in water by using gum Arabic as surfactant. The thermal conductivity was measured by the steady-state method by using a coaxial-cylinder cell that allows the sample temperature to be varied from 15to75°C. Our measurements show that the thermal conductivity enhancement as compared to water linearly increases when the MWCNT weight content increases from 0.01to3wt%, reaching 64% for the MWCNT weight content of 3wt%. The thermal conductivity enhancement is found to be temperature independent up to MWCNT weight content of 2wt%. The average length of the nanotubes appears to be a very sensitive parameter. The thermal conductivity enhancement as compared to water increases by a factor of 3 when the nanotube average length increases in the 0.5–5μm range. Electrical conductivity measurements show that the electrical properties do not follow the same trend as a function of MWCNT weight content, as compared to thermal properties. The electrical conductivity is mainly constant in the studied range, but undergoes a drop when the weight content decreases to about 0.1wt%, which suggests that the MWCNT network in the base fluid might be percolating at this very low value. By comparison, the thermal conductivity does not show any percolation threshold.Thermal and electrical conductivities of suspensions of multiwalled carbon nanotubes (MWCNT) in water were measured as a function of temperature, nanotube weight content, and nanotube length. Nanotubes were dispersed in water by using gum Arabic as surfactant. The thermal conductivity was measured by the steady-state method by using a coaxial-cylinder cell that allows the sample temperature to be varied from 15to75°C. Our measurements show that the thermal conductivity enhancement as compared to water linearly increases when the MWCNT weight content increases from 0.01to3wt%, reaching 64% for the MWCNT weight content of 3wt%. The thermal conductivity enhancement is found to be temperature independent up to MWCNT weight content of 2wt%. The average length of the nanotubes appears to be a very sensitive parameter. The thermal conductivity enhancement as compared to water increases by a factor of 3 when the nanotube average length increases in the 0.5–5μm range. Electrical conductivity measurements show that...

Local current mapping of single vertically aligned multi-walled carbon nanotube in a polymer matrix

This paper reports our work on the development of thin composite films based on aligned multi-walled carbon nanotubes (CNTs) forest embedded in epoxy polymer matrix dedicated for 3D-interconnection in flexible substrate. To reach this goal, information about local CNT properties is strongly needed. In this study, aligned multi-walled carbon nanotube carpets were prepared by aerosol Assisted catalytical chemical vapor deposition (AA-CCVD) process. Such carpets were then embedded in a polymer matrix, subsequently thinned by chemical mechanical polishing (CMP) process and finally treated by plasma process. Then, to determine local conducting properties of CNT, the surface of the composite film is studied by conductive AFM (C-AFM) and scanning spreading resistance microscopy. These methods are discussed and compared. C-AFM appears to be the most efficient method to obtain high resolution current maps. For the first time, a local electrical property mapping and current versus applied voltage characteristics ov...

Multi-Walled Carbon Nanotube Based Sensors for Selective Detection of Chemical Pollutants

This work reports the design of a resistive gas sensor based on 2D mats of multi-walled carbon nanotubes (MWCNT). The sensor sensitivity was optimised using chlorine by tuning both MWCNT network morphology and MWCNT electronic properties. Raw CNT were compared with annealed CNT. Besides, with the aim to enhance the sensor sensitivity and selectivity for detection of several gases, MWCNT were functionalized with poly (phenylene)-like or vinyl polymers using a process based on the diazonium chemistry. In this paper, we will mention the preparation of such sensors and we will demonstrate that the optimized devices are operating at room temperature, for the detection of pollutants such as chlorine, hydrogen chloride and ammonia. Such sensors are able to detect down to 30 ppb of pollutant, in particular for chlorine.

Microdiffraction Study Of Iron-Containing Nanotube Carpets

X‐ray microdiffraction can be a powerful technique to study nanotube‐based materials, as shown here for carpets of aligned multiwall carbon nanotubes synthesized by aerosol‐assisted Catalytic Chemical Vapor Deposition. Catalytic particles are found to be iron oxide. Moreover, local analysis of nanotube alignment allows one to understand the effects of the synthesis procedure.