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Title: Self-assembly by multi-drop evaporation of carbon-nanotube and graphene-oxide-platelet droplets on a polycarbonate substrate for applications in energy and medicine

Hatim Machrafi

Université libre de Bruxelles, Belgium

Biography

Dr. Hatim Machrafi received a Chemical Engineering degree from the Eindhoven University and a PhD in Chemistry and Energetics from the Université Pierre et Marie Curie (Paris 6), with the highest mention. Currently, he works as a senior researcher with teaching activities. He leads research in extended thermodynamics at the Université de Liège for application in nanosystems and systems of high frequency (or short time scales). In parallel, he pursues his research activities in experimental studies of nanoparticle depositions on functionalized substrates and nanoporous systems at the Université libre de Bruxelles for energetic and medical applications.  

Abstract

Water droplets containing carbon nanotubes (CNTs), SiO2 (silica) nanoparticles and mixtures of them, are deposited one drop after the other on a polycarbonate substrate. During evaporation of the droplets, the CNTs and silica nanoparticles go through a self-assembly process, forming a nanocomposite. Two types of composites are prepared. The first is a composite prepared by depositing alternately a layer of CNTs and silica nanoparticles. The second is a nanocomposite prepared by depositing a pre-mixed CNT/silica droplet. The former results into a series of alternate layers and the other by a homogeneous nanocomposite of silica nanoparticles embedded in a porous CNT structure. The thickness, thermal and electrical conductivity (in both the perpendicular and parallel direction) of the composites are measured versus the number of depositions. The morphology of the nanomaterials is characterized by scanning electron microscopy (SEM). The one-dimensional confocal probe method is used to measure the thickness of the layers. The pre-mixed composites showed an increase in the values in both the parallel and perpendicular directions of both the electrical and thermal conductivities, making them suitable for electrodes or battery-like applications. The values of the electrical and thermal conductivities in the perpendicular direction for the first composite decrease and increase, respectively, while for the parallel direction the values are significantly constant. As such, they would be useful as electrical insulators for optimal cooling. Thickness measurements showed that the pre-mixed composite is the denser one, due to a better alignment of the carbon nanotubes. The proposed method in this work is of little cost and hardly energy-consuming. With respect to the often-used dip-coating method, the procedure in this work contributes to a better control of depositing pre-mixed solutions. This resulted into silica-induced CNT alignment with a higher density network, improving considerably the thermal and electrical properties in the aligned direction. This work shows that a simple and low-cost procedure is capable of preparing composites out of the same components, but with different properties.

Audience take away:

• Drop-by-drop deposition procedure provides efficient low-cost CNT networks
• Thermal and electrical conductivities are improved due to silica-CNT interaction, being caused by a better alignment of CNT around the silica nanoparticles. This proves to be a way to align CNTs without any external field. The interactions are caused by H-bridges, which align effectively the CNTs.
• Designing experiments can be facilitated with the proposed method, due to the opportunity to control the initial parameters and thereby the outcome of the deposited structure in terms of porosity and conductivity.
• The high degree of control of the initial parameters and the high reproducibility renders this method to be applicable to a wide range of applications in the energetic and medical sectors, such as membranes or electrodes. Future possible applications are supercapacitors and biosensors.