Thermoelectric Performance of Polypropylene/Carbon Nanotube/Ionic Liquid Composites and Its Dependence on Electron Beam Irradiation

The thermoelectric behavior of polypropylene (PP) based nanocomposites containing single walled carbon nanotubes (SWCNTs) and five kinds of ionic liquids (Ils) dependent on composite composition and electron beam irradiation (EB) was studied. Therefore, several samples were melt-mixed in a micro compounder, while five Ils with sufficiently different anions and/or cations were incorporated into the PP/SWCNT composites followed by an EB treatment for selected composites. Extensive investigations were carried out considering the electrical, thermal, mechanical, rheological, morphological and, most significantly, thermoelectric properties. It was found that it is possible to prepare n-type melt-mixed polymer composites from p-type commercial SWCNTs with relatively high Seebeck coefficients when adding four of the selected Ils. The highest Seebeck coefficients achieved in this study were +49.3 µV/K (PP/2 wt.% SWCNT) for p-type composites and −27.6 µV/K (PP/2 wt.% SWCNT/4 wt.% IL type AMIM Cl) for n-type composites. Generally, the type of IL is decisive whether p- or n-type thermoelectric behavior is achieved. After IL addition higher volume conductivity could be reached. Electron beam treatment of PP/SWCNT leads to increased values of the Seebeck coefficient, whereas the EB treated sample with IL (AMIM Cl) shows a less negative Seebeck coefficient value.

Moiré patterns and carbon nanotube sorting

Moiré patterns (MPs), arising from the superposition of two lattices with close periods, are tightly related to the physicochemical properties of bilayer nanostructures. Here, we develop the theory of complex MPs emerging in twisted bilayer graphene and planar nets of double-walled nanotubes at significant relative twist and/or deformation of layers. The proposed theory clarifies the physicochemical regularities arising at sorting of single-walled carbon nanotubes (SWCNTs) by organic molecules, which self-assemble in regular coatings on both the tubes and planar graphene. We introduce and consider an outer tubular virtual lattice that is a parent structure for the deposited coating and due to this fact, its existence is crucial for the coating formation. As we show, such outer lattices exist only for successfully sorted SWCNTs and the superposition between the outer lattice and SWCNT forms a specific long-period MP. We explain known experimental results of SWCNT sorting by molecules of flavin group, poly(9,9-dioctylfluorene-2,7-diyl) (PFO), and poly [(m-phenylenevinylene)-alt-(p-phenylenevinylene)] (PmPV). Also, our approach points out other organic molecules and polymers suitable for effective CNT sorting.

Enhancing the Thermoelectric Performance through the Mutual Interaction between Conjugated Polyelectrolytes and Single-walled Carbon Nanotubes

We present a method of constructing composites composed of conjugated polyelectrolytes (CPEs) and single-walled carbon nanotubes (SWCNTs) to obtain a high-performing flexible thermoelectric generator. In this approach, three kinds of polymers, namely, poly[(1,4-(2,5-didodecyloxybenzene)-alt-2,5-thiophene] (P1), poly[(1,4-(2,5-bis-sodium butoxysulfonate-phenylene)-alt-2,5-thiophene] (P2), and poly[(1,4-(2,5-bis-acid butoxysulfonic-phenylene)-alt-2,5-thiophene] (P3) are designed, synthesized and complexed with SWCNTs as thermoelectric composites. The electrical conductivities of CPEs/SWCNTs (P2/SWCNTs, and P3/SWCNTs) nanocomposites are much higher than those of non-CPEs/SWCNTs (P1/SWCNTs) nanocomposites. Among them, the electrical conductivity of P2/SWCNTs with a ratio of 1:4 reaches 3686 S cm-1, which is 12.4 times that of P1/SWCNTs at the same SWCNT mass ratio. Moreover, CPEs/SWCNTs composites (P2/SWCNTs) display remarkably improved thermoelectric properties with the highest power factor (PF) of 163 μW m-1 K-2. In addition, a thermoelectric generator is fabricated with P2/SWCNTs composite films, and the output power and power density of this generator reach 1.37 μW and 1.4 W m-2 (cross-section) at ΔT=70 K. This result is over three times that of the thermoelectric generator composed of non-CPEs/SWCNTs composite films (P1/SWCNTs, 0.37 μW). The remarkably improved electrical conductivities and thermoelectric properties of the CPEs/SWCNTs composites (P2/SWCNTs) are attributed to the enhanced interaction. This method for constructing CPEs/SWCNTs composites can be applied to produce thermoelectric materials and devices.

Magnetic nanoribbons with embedded cobalt grown inside single-walled carbon nanotubes

Molecular magnetism and specifically magnetic molecules are recently gaining plenty of attention as key elements for quantum technologies, information processing, and spintronics. Transition to the nanoscale and implementation of ordered...