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Cellulose insulation paper as a part of oil-paper insulation systems plays an important role in the reliability of converter transformers. The reliability of converter transformers equipped with traditional cellulose paper is adversely affected by space charge under DC voltage. The addition of nanoparticles into other dielectrics has been demonstrated to improve electrical performance. However, studies on the space charge behavior of cellulose paper reinforced with nanoparticles are rarely reported. This paper presents the results of a study aimed at elucidating the effect of nano-aluminum nitride (AlN) concentration on the space charge behavior of cellulose paper. Samples with various nano-AlN concentrations were fabricated and pretreated first. The micro-morphologies of prepared cellulose papers were observed using a field-emission scanning electron microscope. The space charge distribution was measured using a pulsed electroacoustic instrument. The results show the dependence of the charge injection as well as charge dissipation on the concentration of nano-AlN. The isothermal decay current method is used to obtain trap information. Based on the density and distribution of traps, the underlying mechanism of the effect of various concentrations on the space charge behavior is theoretically explained. [ABSTRACT FROM AUTHOR]

The introduction of nanoparticles (NPs) and nanostructured materials (NSMs) in papermaking originally emerged from the perspective of improving processing operations and reducing material consumption. However, a very broad range of nanomaterials (NMs) can be incorporated into the paper structure and allows creating paper products with novel properties. This review is of interdisciplinary nature, addressing the emerging area of nanotechnology in papermaking focusing on resources, chemical synthesis and processing, colloidal properties, and deposition methods. An overview of different NMs used in papermaking together with their intrinsic properties and a link to possible applications is presented from a chemical point of view. After a brief introduction on NMs classification and papermaking, their role as additives or pigments in the paper structure is described. The different compositions and morphologies of NMs and NSMs are included, based on wood components, inorganic, organic, carbon-based, and composite NPs. In a first approach, nanopaper substrates are made from fibrillary NPs, including cellulose-based or carbon-based NMs. In a second approach, the NPs can be added to a regular wood pulp as nanofillers or used in coating compositions as nanopigments. The most important processing steps for NMs in papermaking are illustrated including the internal filling of fiber lumen, LbL deposition or fiber wall modification, with important advances in the field on the in situ deposition of NPs on the paper fibers. Usually, the manufacture of products with advanced functionality is associated with complex processes and hazardous materials. A key to success is in understanding how the NMs, cellulose matrix, functional additives, and processes all interact to provide the intended paper functionality while reducing materials waste and keeping the processes simple and energy efficient. [ABSTRACT FROM AUTHOR]

Microfibrillated cellulose (MFC)-SiO nanopapers were prepared using a rapid spray deposition technique. Large area (~310 cm) composite nanopapers with thickness and SiO content varying from 16 to 92 µm and 0 to 33 %, respectively, were prepared in less than 30 min with nearly complete nanoparticle retention in the cellulose mat. In the presence of an excess of MFC, SiO nanoparticles formed large clusters embedded in a dense and continuous cellulose matrix which conferred to the composite an extremely low permeability to air, i.e., below 2 nm. For silica mass fraction above 20 %, SiO clusters induced a net increase in air permeability and ionic conductivity up to 12 nm and 1.5 mS cm for a SiO content of 33 %. Despite the addition of an inert phase, composite nanopapers displayed mechanical properties, viz. Young's modulus and internal cohesion higher than 2.2 GPa and 913 J m, outperforming those of most conventional papers. This study demonstrates that MFC-SiO nanopapers fabricated by spray deposition can be an alternative to PE/PP membranes as separators in Li-ion batteries and, in general, that spray deposition is a promising method for the rapid fabrication of large area composite nanopapers. [ABSTRACT FROM AUTHOR]

A nanosized carbonaceous material was derived from bacterial cellulose (BC). BC, which is produced by bacteria as nanosized material, possesses high degree of crystallinity of 90 %, was pyrolysed at 950 °C and physically activated with CO to produce a nanosized activated carbon material. The pyrolysis of BC yielded a carbonaceous material (carbon yield of between 2 and 20 %) with a relatively low D- to G-band ratio (between 2.2 and 2.8), indicating that the carbonaceous material possesses a graphitic structure. Two different BC materials were pyrolysed-a loose fibrous (freeze-dried) and dense paper form. It was observed that a carbon nanofibre-like material was produced by the pyrolysis of the loose fibrous form of BC. The electric double layer (EDL) capacitance and the area-normalised specific capacitance in KSO solution were as high as 42 F g and 1,617 F cm, respectively. The EDL capacitance was also compared to commercially available activated carbon (YP-50F). [ABSTRACT FROM AUTHOR]

Because of irreversible agglomeration in the dehydrating process, the wet storage and transport of cellulose nanofibres (CNF) are the serious issues that need to be resolved in the commercialization and application of CNF. In this study, silanized cellulose nanofibres (Si-CNF) were prepared by modifying CNF with phenyltrimethoxysilane (PTS). Moreover, a mixture of redispersed Si-CNF and mineral oil was treated by combining ultrasound and high-pressure homogenizer to prepare Pickering emulsions. Different ratios of CNF/PTS were prepared and redispersed, and their morphological characteristics, thermal performance, rheological properties, zeta potential, and size distribution were analysed to evaluate the changes occurring during modification. The results show that the obtained Si-CNF demonstrates excellent redispersibility in water. The viscosity of the redispersed product exhibits the best suspension stability with the particle distribution uniform at the nanoscale when the addition amount of PTS is 0.18 mmol/g. Rheological and dynamic light scattering results have shown that the Pickering emulsion maintains the best dispersion stability at a concentration of 0.02% and remains stable after 7 days of storage. PTS modified the hydrophobicity of the CNF and provided alternative routes for application of CNF and Pickering emulsions. [ABSTRACT FROM AUTHOR]

Heavy metal pollution is one of the most serious environmental problems, posing threats to human health. Here, we developed a magnetic hybrid aerogel by integrating nanocellulose and ferroferric oxide (Fe3O4) nanoparticles for effectively adsorbing heavy metal ions from water and realizing controllable recovery under magnetic condition. The magnetic behavior and adsorbing capacity of the hybrid aerogel on removal of heavy metal chromium (Cr)(VI) ion were examined. Results show that the ferroferric oxide nanoparticles physically adsorb the nanocellulose, each of which retains the original composition and structural characteristics. The magnetic hybrid aerogel possesses good ferromagnetic property with saturation magnetization value of 53.69 emu/g, enabling effective and controllable recovery of the aerogel under magnetic condition The adsorption efficiency of the hybrid aerogel on the Cr(VI) ion reaches the highest value of 2.2 mg/g when the mass ratio of the nanocellulose to ferroferric oxide nanoparticle is 1:1. Additionally, the hybrid aerogel presents similar adsorption behavior on plumbum (Pb)(II) and copper (Cu)(II) ions, suggesting extended applications of the hybrid aerogel on removal of heavy metal ions. Such strategy could provide new applications for the abundant nanocellulose resources and could be extended to integrate nanocellulose with other functional nanomaterials into novel hybrid aerogel for water purification. [ABSTRACT FROM AUTHOR]

In this article, conductive composite films based on TEMPO-oxidized cellulose nanofibers (TOCN) and polypyrrole (PPy) were synthesized in situ by a Chemical Polymerization Induced Adsorption Process of pyrrole on the surface of TOCN in aqueous medium. Resulting composite films were investigated by X-ray photoelectron spectroscopy, scanning, and transmission electron microscopy, N gas adsorption analysis, thermogravimetric analysis, mechanical tests, and conductivity measurements in the ambient air. Our results showed a stable, flexible, and highly electrically conductive composite film in which PPy nanoparticles coated the surface of the TOCN network. In addition, the advantage in using the famous material, TOCN, is clearly due to the presence of carboxylate (COOH/COONa) and hydroxyl (OH) moieties on the surface of TOCN. These reactive moieties could enhance the adsorption process of positively charged PPy backbone during polymerization. TEM observations demonstrated the formation of a PPy coat along the surface of the cellulose nanofibers having a diameter of about 90 nm which is relatively higher compared to the initial diameter of pure TOCN (~9 nm). Despite the physical and chemical treatment of TOCN during polymerization, the micrometric length of the cellulosic nanomaterial was maintained. In addition, the incorporation of polyvinyl alcohol as an additive in the TOCN/PPy composite seems to enhance the flexibility of composite films (bent up to 180°) without losing the high electrical conductivity. Finally, because of the high conductivity and good mechanical properties of the TOCN/PPy composite films obtained in this work, they can be used as a promising material in applications of sensors, flexible electrodes, and other fields requiring electrically conductive flexible films. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]