Clay/Conductive Polymer Nanocomposites

This chapter describes the main strategies for designing clay nanocomposites of the most investigated inherently conductive polymers, namely, polypyrrole, polyaniline, and polythiophenes including poly(3,4-ethylenedioxythiophene) polystyrene sulfonate. It is shown that premodification of clays is an essential step to successful intercalation or exfoliation by conductive polymers. Toward this end, surfactants, reactive diazonium, and silanes permit the preparation of adhesive clay sheets for the conductive polymers once polymerization is triggered. Exfoliated nanocomposites usually exhibit superior properties compared to intercalated ones. Through selected applications (e.g., conductive fillers, catalysts, sensors, ultracapacitors), it is clear that research on clay–conductive polymer nanocomposites will continue to grow because these materials combine the best of two worlds: low-cost abundant minerals with remarkable nanostructural properties and nanostructuring abilities on the one hand and ease of synthesis, reactivity, and electrical conductivity of conjugated polymers on the other hand.Scopu

PREPARATION AND PHOTOTHERMAL CHARACTERIZATION OF NANOCOMPOSITES BASED ON HIGH DENSITY POLYETHYLENE FILLED WITH EXPANDED GRAPHITE: PARTICLE SIZE AND SHAPE EFFECTS

This work aimed at thermal transport characterization of high density polyethylene (HDPE) filled with two sizes (5 and 50 mu m) of expanded graphite (EG) particles. Sample platelets were produced by melt mixing followed by compression molding. Thermal conductivity k was determined by combining measurements of density, specific heat capacity and thermal diffusivity. For the latter, we used the self-checking, non-contact method of photothermal radiometry (PTR) in back detection configuration. Starting from an effective medium approximation model, we derived a simple linearized expression for the effective k of composites with low particle charge. It explains the unusually high experimental k values (up to four-fold increase) as the effect the strongly non-spherical EG particles (aspect ratio 1/p = 110 - 290). Larger particle sizes produce higher k enhancement, while the interfacial thermal resistance (R-bd = 2.1.10(-7) m(2).K/W) has an opposite effect on k. The eventual deviation of experimental k from the model at high particle charge is possibly due to limitation of interparticle free space preventing random orientation of high aspect ratio particles

Elastomeric actuators based on ethylene-vinyl acetate and carbon nanotubes

The development of new types of visual-aid tablet for visually impaired people requires the development of cheap, but still very effective photoactuating materials. This requirement can be satisfied by the use of new kind of elastomers filled by nanofillers, such as carbon nanotubes. Nanocomposites based on commercial ethylene vinyl-acetate (EVA) copolymer and multiwalled carbon nanotubes (MWCNT) were prepared by casting from solution. The non-covalent surface modification of MWCNT was carried out by special, newly synthesized compatibilizer cholesteryl 1-pyrenecarboxylate (PyChol). In order to mimic Braille character, special home-built silicone punch and die moulds were used. The Brailleelement based on EVA/MWCNT-PyChol composite displays reversible, multiple changes of dimension in thedirection of the irradiation during/upon illumination by red and blue light-emitted diode (LED). Transmission electron microscopy (TEM) showed a good dispersion of the MWCNT-PyChol within the matrix. The Braille element behaviour under illumination was analysed by atomic force microscopy (AFM) and by nanoindentor. Nanoindentor, even if the purpose of its original use is different, can be effectively applied for the determination of the actuation stroke, the sample dimensional changes in the directionof irradiation.Scopu

Electrical Conductivity of Glass Fiber-Reinforced Plastic with Nanomodified Matrix for Damage Diagnostic

The electrical conductivity of glass fiber-reinforced plastic (GFRP) with epoxy matrix modified by multiwall carbon nanotubes (MWCNT) was studied. The electrical conductivity of nanomodified lamina and multi-layered GFRP was investigated on several levels using a structural approach. Components of the electrical conductivity tensor for unidirectional-reinforced monolayer were calculated similarly as in micromechanics using the conductivity of the nanomodified matrix. The electrical conductivity of multilayer composite was calculated using laminate theory and compared with values measured experimentally for various fiber orientation angles. Calculated and experimental data were in good agreement. The voltage distribution measured throughout the laminate allowed detecting the damage in its volume. The electrode network located on the laminate surface could determine the location, quantification, and geometry of the damage in the GFRP lamina modified with MWCNT. Experimental and calculated electrical resistance data for GFRP double-cantilever beam specimens were investigated in Mode I interlaminar fracture toughness test. Results demonstrate that electrical resistance could be successfully used for the diagnostic of the crack propagation during interlaminar fracture of the MWCNT-modified GFRP

Morphological, Mechanical and Gas Penetration Properties of Elastomer Composites with Hybrid Fillers

Ethylene–propylene–diene monomer (EPDM)-based composites including four different types of graphene nanoplatelets (GnPs) were prepared to evaluate the size effects of GnPs in terms of both specific surface area and lateral size on the morphological, mechanical, and viscoelastic properties, swelling ratio, crosslink density, and oxygen permeability. EPDM-based hybrid composites with GnPs and carbon black (CB) fillers were prepared, with the concentrations of 20 and 50 phr of CB and GnPs up to 7 phr. All samples were prepared using the melt mixing method, followed by compression molding. The specific surface area of GnPs is a more important key factor for mechanical and viscoelastic properties than its lateral size. The presence of GnPs leads to a decrease in the swelling ratio and oxygen permeability of the matrix while an increase in the crosslinking density. For a given specific surface area of GnPs (170 m(2)/g) and the same thickness (5 nm), the optimum lateral size for mechanical properties, swelling ratio, and crosslinking density is about 30 µm. There is a distinct synergic effect on the mentioned properties when hybrid fillers are used. For hybrid composites, the optimum total and each filler concentration are found to be important for achieving the best performance in terms of mechanical properties, swelling ratio, and crosslink density

Insight into the Li-storage property of surface-modified Ti2Nb10O29 anode material for high-rate application

Ti-based anode materials are considered to be an alternative to graphite anodes to accomplish high-rate application requirements. Ti2Nb10O29 (TNO15) has attracted much attention due to its high lithium storage capacity through the utilization of multiple redox couples and a suitable operating voltage window of 1.0 to 2.0 V vs Li/Li+. However, poor intrinsic electronic conductivity has limited the futuristic applicability of this material to the battery anode. In this work, we report the modification of TNO15 by introducing oxygen vacancies and using few-layered carbon and copper coatings on the surface to improve its Li+ storage property. With the support of the galvanostatic intermittent titration technique (GITT), we found that the diffusion coefficient of carbon/copper coated TNO15 is 2 orders of magnitude higher than that of the uncoated sample. Here, highly conductive copper metal on the surface of the carbon-coated oxygen-vacancy-incorporated TNO15 increases the overall electronic and ionic conductivity. The prepared TNO15-800-C-Cu-700 half-cell shows a significant rate capability of 92% when there is a 10-fold increase in the current density. In addition, the interconnected TNO15 nanoparticles create a porous microsphere structure, which enables better Li-ion transportation during charge/discharge process, and experiences an enhancement after the carbon and copper coating on the surface of the primary TNO15 nanocrystallites.CzechNanoLab Research Infrastructure; Ministry of Education, Youth, and Sports, Czech Republic; Technology Agency of the Czech Republic, TACR; HORIZON EUROPE Framework Programme, (101078935); Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT, (CZ.02.2.69/0.0/0.0/18_053/0017879, LM2023051, LTT20005, TH71020006)Ministerstvo ?kolstv?, Ml?de?e a Telov?chovy [LTT20005, CZ.02.2.69/0.0/0.0/18_053/0017879]; Ministry of Education, Youth, and Sports, Czech Republic (MEYS CR) [LM2023051]; CzechNanoLab Research Infrastructure (MEYS CR); Technology Agency of the Czech Republic [101078935]; Horizon Europ