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Nanocomposite Membranes in Water Treatment
Published in P.K. Tewari, Advanced Water Technologies, 2020
Studies have been carried out on reinforcement of the membrane with hybrid materials to give better performance. Titania-coated multi-wall nanotubes reinforced into the polyethersulfone matrix membrane show better hydrophilicity and pure water flux.170 Fouling resistance is exhibited due to the lower surface roughness and synergistic photocatalytic activity. The existence of nanotubes reduces the electron/hole recombination and improves photon efficiency. A multifunctional membrane designed by incorporating gold nanoparticles (AuNPs)/ exfoliated graphite nano-platelets into a polysulfone membrane shows enhanced compaction resistance and permeability as well as superior catalytic property on the reduction of 4-nitrophenol to 4-aminophenol by NaBH4, where AuNPs serve as the catalyst. The structure and catalytic activity of such membranes can be controlled separately by changing the relative contents of the corresponding components in the nanofiller hierarchy. Nanocomposite membranes containing silica (SiO2)/graphene oxide (GO) hybrid material171, 172 exhibit better permeability, protein rejection and fouling resistance than SiO2/polysulfone and GO/polysulfone membranes. The synergistic effect of SiO2/GO is due to its high hydrophilicity as well as the special sandwiched structure that facilitates its dispersion in the polysulfone matrix.
Effect of Cu surface and graphene on the conformation of n-octadecane: a molecular dynamics study
Published in Phase Transitions, 2022
Yan Zhou, Wanquan Wang, Shukun Zhang, Peng Sun, Yan He
As early as 2012, adding carbon nanomaterials to improve the thermal conductivity and morphological stability of PCM has received widespread attention. Shi [19] et al. adopted graphene and exfoliated graphite nanoplatelets (xGnP) to improve the thermal conductivity and shape-stabilization of paraffin PCM. The physical properties of CPCM of two carbon nano additives were prepared and compared in experimental studies. The results show that 10 wt% of xGnp can increase the thermal conductivity of paraffin/xGnp CPCM by up to 10 times. However, the improvement in thermal conductivity of paraffin/graphene CPCM is comparably small. Huang [20] et al. compared the effects of graphene and graphene oxide additives on the thermophysical properties of paraffin by MD simulation. From the vibration power spectrum of paraffin, graphene and graphene oxide, it was found that there is vibration coupling between paraffin, graphene and graphene oxide in the middle- and low-frequency region. The thermal conductivity of paraffin/graphene oxide is higher than that of paraffin/graphene due to their larger molecular vibration couplings.
Preparation of exfoliated graphite-based polyethylene composites with enhanced thermal conductivity
Published in Soft Materials, 2020
Hongwei Fang, Yixian Liu, Guohua Li, Yingchun Liu, Lianqi He, Xiongwei Qu
Polyethylene (PE) has many excellent properties, such as high flexibility, good processing property, and hydrostatic resistance. It has been widely used in hot/cold water transporting, including floor heating, heating connections, heat exchangers, solar panels, and thermal circulation systems. However, the applications of PE are limited due to its low thermal conductivity. Many researchers have been working on solving this disadvantage by adding various thermally conductive fillers in to PE matrix, including carbon materials (e.g. graphite,[1,2] grapheme,[3] carbon fibers,[4] carbon nanotubes[5]), inorganic thermally conductive particles,[6] or/and metal particles.[7] Among them, graphene has outstanding mechanical properties (modulus about 1060 GPa, strength about 20 GPa)[8] and thermal conductivity (5300 W/[m∙K]).[9] However, few studies have been conducted due to the high cost and difficulty of large scale production.[10] Recently, some researchers have been working on the use of different forms of graphite,[11] graphite oxide,[12] exfoliated graphite,[1] and graphene sheet,[3] to develop nanocomposites. Among them, the exfoliated graphite nanoplatelets have become a focus of research to improve the mechanical properties[13,14] and thermal properties[15] of polymer composites. The low-cost graphite is a precursor of exfoliated graphite nanoplatelets.[16] A mechanochemical synthesis technique, based on a high-energy planetary ball milling, has been used to prepare exfoliated graphite in a large scale owing to the low cost.[17] Xu et al.[18] took advantages of a simple ball milling technique combing physical and chemical routes for a facile, low-cost, scalable, and eco-friendly production of graphene nanoplatelets. Yan et al.[19] reported a simple and efficient method using ball milling to prepare highly electroactive, hydrophilic, and hydroxyl-functionalized graphene.