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The use of graphene materials, i.e. graphene oxide, reduced graphene oxide, graphene nanoplatelets and their functionalized forms as fillers of epoxy composites, is reviewed. The purpose of...

Single-walled carbon nanotubes (SWCNTs) demonstrate unique properties of both electrical and thermal conductivity, but at the moment of producing a network composed of multiple nanotubes, these values sharply decrease. It is associated with the presence of defects in the nanotube network structure, as well as with the dissipation phenomena at the junctions between SWCNTs. One of the methods to alleviate this problem is doping. In our study, we obtained a film made of high-quality SWCNTs doped with three types of iodonium salts: Barluenga’s reagent (bispyridineiodonium tetrafluoroborate, IPy2BF4), pyridine iodine monochloride (IPyCl) and diphenyliodonium chloride (DPIC). We recorded a significant improvement in electrical properties after doping with IPy2BF4 and IPyCl, by as much as 224% and 322%, respectively. What is more, we noted improvement in thermal conductivity, which amounted to over 50% when the material was doped with IPyCl. Our research indicates that permanent doping of CNT-based ensembles is possible with iodonium salts. The process significantly improves electrical conductivity, and the compounds themselves are more convenient to work with rather than when other halogen-based dopants are used commonly for this purpose.

In this work, DC conductivity and EMI shielding characteristics in the frequency range of 25.5–37.5 GHz (Ka-band) of polymer composites based on ultrahigh-molecular-weight polyethylene (PE) and polypropylene (PP) containing different types of nano- and microfillers were studied. Graphene nanoplatelets (Gr), thermally exfoliated graphite (TEG), thermally treated anthracite (A) and dispersed metals such as iron (Fe) and copper (Cu) were used as conductive fillers. Two types of composites were formed: 1 – with ordered distribution of the filler particles in the form of conductive 3D network in polymer matrix (segregated structure), 2 – with random distribution of the filler particles. It was found that the percolation threshold for Gr and A filler is 100 and 10 times lower in the segregated system was 100 and 10 times lower than that for A filler with its random distribution in polymer matrix. Distinctly increased value of shielding efficiency (SET) in the segregated system can be explained by multiple internal reflection of electromagnetic wave in the network formed in the segregated structure. It was also found that the value of SE corresponds with the electrical conductivity of composites. However, for the same conductivity, higher values of SE were observed for the formed segregated structure in comparison with the literature data for composites with random filler distribution.

Single-walled carbon nanotubes (SWCNTs) remain one of the most promising materials of our times. One of the goals is to implement semiconducting and metallic SWCNTs in photonics and microelectronics, respectively. In this work, we demonstrated how such materials could be obtained from the parent material by using the aqueous two-phase extraction method (ATPE) at a large scale. We also developed a dedicated process on how to harvest the SWCNTs from the polymer matrices used to form the biphasic system. The technique is beneficial as it isolates SWCNTs with high purity while simultaneously maintaining their surface intact. To validate the utility of the metallic and semiconducting SWCNTs obtained this way, we transformed them into thin free-standing films and characterized their thermoelectric properties.

Graphenic materials have been produced from thermally treated highly metamorphosed carbon material – anthracite using two different methods: (1) the improved Hummers method followed by thermal redu...

The concept of application of crumbled carbon foam obtained from polymer precursor as a filler in polymer/carbon composite was described. The carbon foam used as powdered reinforcement of composites was prepared from epoxy resin cross-linked with phenol–formaldehyde resin (novolac) in a self-foaming process followed by carbonization at not very high temperature and ambient pressure. The structure of the carbon foam filler and resultant composites was studied by microscopic and spectroscopic methods. In the final composites, there were observed good quality dispersion of micronized grains of carbon foam, with the sizes that preserve their specific porous structure, in epoxy matrix and excellent adhesion at interfacial areas. The influence of the CF filler on the properties of resultant composites were investigated. Due to valuable properties of carbon foam, resultant composites occurred to have interesting characteristics: densities similar to those of pure polymer matrix, advantageous thermal and viscoelastic properties and enhanced tribological features.

We have demonstrated that the aqueous two-phase extraction (ATPE) can differentiate between large diameter single-walled carbon nanotubes (CNTs) by electrical character. Introduction of &ldquo, hydration modulators&rdquo, to the ATPE machinery has enabled us to isolate metallic and semiconducting CNTs with ease. We have also shown that often there is a trade-off between the purity of the obtained fractions and the ability to separate both metallic and semiconducting CNTs at the same time. To isolate the separated CNTs from the matrices, we have proposed a method based on precipitation and hydrolysis, which can eliminate the need to use lengthy dialysis routines. In the final step, we prepared thin free-standing films from the sorted material and probed how electrical charge is transported through such macroscopic ensembles.

The study of interfacial interactions between polymer matrix and particulate fillers is essential for producing composites with enhanced properties. In this work, the influence of the unique glassy carbon (GC) structure on the properties of its binary epoxy composites as well as hybrid nanocomposites with GC and multi-walled carbon nanotubes (MWCNTs) was investigated. The purpose of incorporating MWCNTs into the epoxy matrix (EP) as an addition filler was to obtain nanocomposites with improved properties. The influence of GC particles alone or in combination with MWCNTs on morphological, thermomechanical, and electrical properties of composites was studied in detail. There were found good, homogeneous dispersion of GC and MWCNTs in epoxy matrix as well as strong interfacial interactions between the carbon fillers and epoxy. Mechanical measurements demonstrated that both the tensile and bending properties of the composites, especially the hybrid composites, were greatly improved compared with those of pure epoxy due to the uniform dispersion of fillers in epoxy and significant adhesion between the filler and matrix. The electrical resistivity of hybrid composites, which is directly related to the presence of MWCNTs in addition to the GC, decreased sharply by 9–11 orders of magnitude compared to the insulating matrix. Such composites with enhanced mechanical and electrical properties could be applied in various branches of industry.

Carbon nanotubes (CNTs) have recently emerged as one of the most promising structures for thermoelectrics (TE). As compared with typical thermoelectric materials, CNTs can be made from almost any carbon-bearing precursor, and so at present thousands of tonnes of them are produced annually at every corner of the world. In this work, we synthesized multi-walled CNTs (MWCNTs) and doped them with heteroatoms of nitrogen, boron or phosphorus to tune their thermoelectric performance. The research showed that MWCNTs doped with nitrogen or boron had improved thermoelectric properties by up to three orders of magnitude as compared with the undoped material. Because of the different modes of charge transport by electrons and holes, respectively, they could be used to construct functional thermoelectric modules.

The adsorption of ethyl acetate, a volatile organic compound, on activated carbons, synthesized from various precursors based on by-products and waste materials—polymer, biomass, coal tar pitch—was studied. The activated carbons were prepared by thermochemical treatment of the precursors, carbonization, and subsequent activation with water vapor. Surface and textural properties of obtained carbon adsorbents were characterized by low-temperature N2 adsorption, Boehm’s method, etc. The activated carbons are distinguished by relatively high surface area and developed pore structure. The adsorption investigations were performed with water solutions of ethyl acetate, and the obtained results fit well the Langmuir model, as well as the Freundlich model. All activated carbons demonstrated considerably high adsorption capacity in the range 160–450 mg/g. The obtained data indicate that the adsorption ability of activated carbon toward ethyl acetate depends on the surface area, and it increases with increasing the content of mesopores, where ethyl acetate molecules are preferably adsorbed.