Dispersion Of Nanofibers Research Articles

Aligning TiO2 nanofiber for high ionic conductivity in cellulose acetate gel electrolytes

The escalating need for sustainable energy storage systems has prompted enhanced investigations into the advancement of environmentally acceptable, flame-retardant, and high-performing polymer gel electrolytes. The present study examines the ionic conductivity and electrochemical characteristics of gel polymer electrolytes (GPEs) based on cellulose acetate (CA) incorporated with disordered and electric-field-induced aligned TiO2 nanofibers. The results of our study indicate that the arrangement of nanofibers within the CA matrix significantly affects the electrical properties of these electrolytes. The highest ionic conductivity of GPEs containing randomly distributed nanofibers is 5.48 × 10−4 S/cm when the nanofiber content is 2.5 wt%. On the other hand, 2.5 wt% aligned nanofibers containing GPE shows a slightly higher room temperature ionic conductivity of 6.2 × 10−4 S/cm. Nevertheless, the alignment of these nanofibers strategically leads to a gradual enhancement in ionic conductivity, ultimately reaching its maximum value of 5.99 × 10−3 S/cm at a concentration of 10 wt% at room temperature. Significantly, the level of conductivity exhibited in this case is more than 1.5 orders higher than the conductivity observed in disordered nanofiber dispersion within the CA matrix. The improved performance can be due to the creation of long-distance conduction channels enabled by the alignment of nanofibers. The incorporation of well-aligned nanofibers into GPEs results in a high Li+ ion transference number of 0.71, an excellent electrochemical stability window of 4.9 V, and exceptional interfacial compatibility with metal electrodes. In addition, the polymer electrolytes exhibit improved flame-retardant properties when 10 wt% aligned nanofibers are added, enabling the samples to endure exposure to a flame for a period of 10 s. These results indicate the potential suitability of the nanocomposite gel polymer electrolytes (NCGPEs) for application in future advanced energy-storing systems. XRD, FTIR, and XPS investigations further confirm the ion-conduction features of the produced NCGPEs. The investigation of increased electrical characteristics of NCGPEs was supported by a detailed computer simulation conducted using density functional theory (DFT).

Superior high-temperature mechanical and thermal performance of carbon fiber/epoxy composites by incorporating highly dispersed aramid nanofibers

Enhancing the high-temperature properties of polymer-matrix fiber-reinforced composites is a challenging task, given the thermal limitations of polymer resins. In this study, we propose a straightforward and efficient method for producing high-performance carbon fiber/epoxy composites with superior high-temperature properties by incorporating highly dispersed aramid nanofibers. To achieve high dispersion of aramid nanofibers in the epoxy, we used a sequential solvent exchange method, which allowed us to fabricate B-stage cured resin films. The aramid nanofiber-hybridized carbon fiber composite, manufactured using resin film infiltration, demonstrated impressive mechanical and thermal properties. Specifically, in the glass transition temperature range at high temperatures, the composite provided 3.1, 5.1, and 6.8 times higher Young's modulus, tensile strength, and short beam strength, respectively, compared to the unmodified composite. Moreover, incorporating aramid nanofibers significantly increased the glass transition temperature by 31 °C, resulting in 2.4 times higher storage modulus and improved thermal stability with an increase in the total weight residue at 800 °C by 33.7 %. Therefore, the highly dispersed aramid nanofiber-embedded carbon fiber composite shows great potential for use in high-performance polymer composite applications.

Extrusion 3D printing of carbon nanotube-assembled carbon aerogel nanocomposites with high electrical conductivity

Carbon nanotubes (CNTs) with high aspect ratio and excellent electrical conduction offer huge functional improvements for current carbon aerogels. However, there remains a major challenge for achieving the on-demand shaping of carbon aerogels with tailored micro-nano structural textures and geometric features. Herein, a facile extrusion 3D printing strategy has been proposed for fabricating CNT-assembled carbon (CNT/C) aerogel nanocomposites through the extrusion printing of pseudoplastic carbomer-based inks, in which the stable dispersion of CNT nanofibers has been achieved relying on the high viscosity of carbomer microgels. After extrusion printing, the chemical solidification through polymerizing RF sols enables 3D-printed aerogel nanocomposites to display high shape fidelity in macroscopic geometries. Benefiting from the micro-nano scale assembly of CNT nanofiber networks and carbon nanoparticle networks in composite phases, 3D-printed CNT/C aerogels exhibit enhanced mechanical strength (fracture strength, 0.79 ​MPa) and typical porous structure characteristics, including low density (0.220 ​g ​cm−3), high surface area (298.4 ​m2 ​g−1), and concentrated pore diameter distribution (∼32.8 ​nm). More importantly, CNT nanofibers provide an efficient electron transport pathway, imparting 3D-printed CNT/C aerogel composites with a high electrical conductivity of 1.49 ​S ​cm−1. Our work would offer feasible guidelines for the design and fabrication of shape-dominated functional materials by additive manufacturing.

Reinforced energy storage performance of poly(vinylidene fluoride) composite films by filling with surface fluorinated one-dimensional barium titanate nanofibers

One-dimensional barium titanate nanofibers/poly(vinylidene fluoride) (PVDF) composite films were prepared by casting technology. To improve the dispersion of nanofibers in the PVDF matrix and enhance the interface bonding between nanofibers and the PVDF matrix, surface modification of nanofibers was obtained by fluorination treatment. Experimental and theoretical simulation studies were conducted to investigate the effects of surface fluorination-modified one-dimensional barium titanate nanofibers on the micro morphology, structure, dielectric constant, and energy storage density of PVDF composite films. The results showed that the barium titanate powder synthesized by electrospinning had a good one-dimensional fiber morphology, with a diameter of 70–130 nm and a length of 4–15 µm. The surface fluorination treatment was able to significantly improve the dispersion and bonding of the one-dimensional barium titanate nanofiber in the PVDF matrix. As the filling volume of the one-dimensional nanofibers increased, the dielectric constant of the PVDF composite film significantly increased. When the filling volume of the surface fluorinated one-dimensional barium titanate nanofiber was 7.5 vol%, the room temperature dielectric constant of the PVDF composite film reached 21.8, and the surface fluorinated one-dimensional barium titanate nanofiber/PVDF composite film exhibited lower dielectric loss and high breakdown strength. When the filling volume of the surface fluorinated one-dimensional barium titanate nanofiber was 2.5 vol%, the energy storage density of the PVDF composite film was 7.9 J/cm3, which was 2.82 times that of pure PVDF. The improvement of energy storage performance can be attributed to the good dispersion of the surface fluorinated barium titanate nanofibers in the PVDF matrix and the good interface situation. Finite element simulation further revealed that the surface fluorinated one-dimensional nanofibers could effectively improve the breakdown strength of the composites. That provides a promising way to enhance the dispersion and interface bonding of filler in polymer matrices, thereby achieving high-performance composites with high dielectric constant, high breakdown strength, and excellent energy storage density.

Dispersion of Cellulose Nanofibers in Methacrylate-Based Nanocomposites.

Poly(methylmethacrylate-co-methacrylic acid) (PMMA-co-MAA) polymers were prepared via cobalt-mediated free radical copolymerization and were characterized after synthesis. The synthesis led to a 98.5% conversion and a final ratio between the two units, MMA/MAA, was equal to 63:37 mol%. PMMA-co-MAA was then used as a matrix for cellulose-based nanocomposites to tailor filler compatibility, thanks to the presence of carboxylic groups capable of generating strong H-bonds with the cellulose surface. Cellulose nanofibers (CNFs) were dispersed using a solution with a mixture of two solvents to tailor compatibility of both the components. For this purpose, CNFs were successfully re-dispersed in methanol using the solvent exchange method and tetrahydrofuran/methanol mixtures at different ratios were used for the preparation of the films. Fully transparent films of PMMA-co-MAA + CNF were prepared up to 15 wt% of CNF with a good dispersion in the matrix. This dispersion state leads to the reinforcement of the polymethacrylate matrix, increasing its tensile strength whilst preserving optical transparency.

Highly thermally conductive and insulating PET nonwoven fabric/PDMS sandwich composite film by synergism of boron nitride nanosheets and alumina particles

AbstractThe accumulation of heat in electronic devices puts forward an urgent demand for thermal interface materials. It is still a great challenge to achieve the good comprehensive performance of high thermal conductivity (TC), insulation, flexibility and tensile strength. In this work, polyester‐based nonwoven fabric (NWF) was coated with boron nitride nanosheets (BNNS) by dispersion and interfacial reinforcement of cellulose nanofibers to obtain a three‐dimensional thermally conductive network skeleton (BNNS@NWF). The sandwich‐structured composite film was assembled by introducing alumina (Al2O3)/polydimethylsiloxane (PDMS) layers on the top and bottom surfaces of BNNS@NWF using scratch coating and hot pressing processes. The composite film has a high TC of 6.42 W/mK at 45.8 wt% BNNS content, and has excellent insulation with a volume resistivity of 1.06 × 1015 Ω cm. This is due to the long‐range effective thermal conduction path constructed by BNNS, the bridging effect of Al2O3 and the synergistic effect of the two fillers. PDMS helps the composite film maintain good flexibility and good TC stability after 30 bending cycles. The PET nonwoven interlayer gives the composite film good mechanical properties with a tensile strength of 17.5 MPa. This work provides a strategy for the efficient preparation of flexible composite films with high TC and insulation properties, which is of great importance for the development of innovative thermal interface materials.Highlights A sandwich‐structured composite film was prepared by a simple scale‐up method. Al2O3 and BNNS achieves synergistic enhancement of thermal conductivity. The film has a high thermal conductivity of 6.42 W/mK and electrical insulation. The film shows good flexibility, high tensile and thermal management properties.

Formation and characterization of oleogels obtained via direct dispersion of ultrasound-enhanced electrospun nanofibers and cold milling

Formation and characterization of oleogels obtained via direct dispersion of ultrasound-enhanced electrospun nanofibers and cold milling

Biodegradable Poly(butylene adipate-co-terephthalate) Nanocomposites Reinforced with In Situ Fibrillated Nanocelluloses

The enhancement of mechanical properties is highly required for the expanded applications of biodegradable polymers like poly(butylene adipate-co-terephthalate) (PBAT). The use of nanocellulose as reinforcing fillers is one of the effective approaches while preserving the biodegradability of polymers, but the dispersion of nanofibers in polymer matrixes is a great challenge. Here, we report an in situ fibrillation method to prepare nanocellulose-reinforced PBAT composite films with superior mechanical properties and enhanced degradability while promoting the easy dispersion of natural plant fibers in the polymer matrix, which overcome the limitation of natural fiber composites for thin film applications. A hemicellulose-rich holocellulose fiber was selected and silanized prior to melt compounding with PBAT, in which in situ fibrillation of fibers and the dispersion of in situ fibrillated cellulose nanofibrils (CNFs) occurred simultaneously. The nanostructure, mechanical properties, and degradability of the resulting composite films were characterized. Compared with pristine PBAT, the incorporation of 1 wt % CNF fillers increased the tensile modulus by 82% while possessing a tensile strength of 26 MPa, an elongation of 372%, and a toughness of 75 MJ/m3, surpassing most reported data. Moreover, the degradability of PBAT was enhanced as well. Altogether, this study paves a new way of making biodegradable nanocomposites, which expand the application areas, especially where films are required.

Evaluation of natural protein-based nanofiber composite photocrosslinking hydrogel for skin wound regeneration

Protein based photocrosslinking hydrogels with nanofiber dispersions were reported to be an effective wound dressing. In this study, two kinds of protein (gelatin and decellularized dermal matrix) were modified to obtain GelMA and ddECMMA, respectively. Poly(ε-caprolactone) nanofiber dispersions (PCLPBA) and thioglycolic acid-modified chitosan (TCS) were added into GelMA solution and ddECMMA solution, respectively. After photocrosslinking, four kinds of hydrogel (GelMA, GTP4, DP and DTP4) were fabricated. The hydrogels showed excellent physico-chemical property, biocompatibility and negligible cytotoxicity. When applied on the full-thickness cutaneous deficiency of SD rats, hydrogel treated groups exhibited an enhanced wound healing effect than Blank group. Besides, the histological staining of H&E and Masson’s showed that hydrogels groups with PCLPBA and TCS (GTP4 and DTP4) improved wound healing. Furthermore, GTP4 group performed better healing effect than other groups, which had great potential in skin wound regeneration.

Crack-bridging and strengthening prospects of nanofibers in the cement composite – A review

The primary objective of this review is to investigate the influence of nanofibers in the modifications of the strength characteristics of the cement composite. Cement composite is an important constituent in civil infrastructures due to its great compressive strength and constructability. The poor binding characteristics of cement composite lead to microfractures during casting, which leads to the weakening of the structure. In order to decrease the microfractures, nanofibrous materials like carbon nanofibers are employed. The incorporation of nanofibers in cement composite also increases the water resistance in buildings. Hence in this article, the use of nanofibers in diverse constructions and property enhancement approaches are examined. The incorporation of fibers in cement composite has been proven to control its fracture behavior and retain its ductility in tension. Nanofiber-reinforced cement composite was also put into practice in highway construction to withstand the bearing loads and sudden impact loads of automobiles. Recent work on nanofiber cement composite demonstrates to acquire a better toughness value and also opens the path to higher flexural strength than that of regular fiber-reinforced cement composite and plain cement composite. The performance of this composite emerges the excellent crack bridging and favored load transmission at micro-scale by the inclusion of fibers in cement composite. These nanofibers also aid in the early identification of micro-cracks and maintain cement composite compactness during the construction of a structure. The review finds that appropriately dispersed nanofibers in a cement matrix may considerably increase the cracking resistance and flexural strength of cement composite by early detection of fractures which acts as a key element in the prevention of brittle cement composite failure.

Carbon nanofiber dispersion in alkali solution and its reinforcement of alkali-activated volcanic ash-based geopolymers

Volcanic ash has several negative impacts on the environment and can be used in massive to synthesize geopolymers, which are considered quasi-brittle. Carbon nanofibers (CNFs) can reinforce the geopolymers, and the dispersion of CNFs directly determines the reinforcement effect. However, the dispersion of CNFs in alkali solutions is challenging. In this paper, the effect of surfactant type, dosage, and ultrasonic time on CNFs dispersion in aqueous and alkali solutions was investigated by the quantitive method of microscopic image processing to determine the preferred dispersion scheme. Zeta potential tests and visual observation were used to analyze the mechanism and stability. Based on this, volcanic ash-based geopolymer nanocomposites with 0.1 wt% contents of CNFs were synthesized. The mechanical properties were tested, and the microstructure was characterized using Scanning Electron Microscope coupled with Energy Dispersive Spectroscopy and Mercury Intrusion Porosimetry. The results showed that methylcellulose (MC), polycarboxylate superplasticizer (PC), and polyvinylpyrrolidone (PVP) could disperse CNFs in aqueous, but evident aggregations can be observed in the alkali solution. PC performed better than MC and PVP in alkali solutions, with 4.83% aggregation area of the whole image, 86% of 0–100 μm2 aggregations, and an average aggregation area of 87 μm2, beneficial from the comb-like structures. Dispersed CNFs can improve the 28-d flexural and compressive strength of the resulting geopolymer nanocomposite by 23% and 16%, respectively, and refine the pore structure through filling, bridging, and nucleation effects, decreasing the average pore size and porosity by 33% and 15%. This paper will contribute to the resourceful use of volcanic ash to reduce pollution and the higher reinforcement of CNFs in alkali-activated geopolymers.

Bacterial Cellulose Nanofibers Modified with Quaternary Ammonium Salts for Antimicrobial Applications

Nanofibrillated bacterial cellulose (NFBC) is a recyclable, biodegradable, and nontoxic biopolymer whose fibers are much longer than other cellulose nanofibers prepared from wood pulp. NFBC is a promising material for use as an additive in food and pharmaceutical industries and as a nanofiller in fiber-reinforced nanocomposite resins; however, it is easily microbially degraded and, consequently, cannot be used in long-term applications. In this study, NFBC was endowed with antimicrobial properties through modification by an aqueous alkaline solution of 2,3-epoxypropyltrimethylammonium chloride (EPTMAC). The structure of the modified NFBC was analyzed in detail using solid-state NMR and infrared spectroscopy, as well as X-ray diffractometry, which revealed that only the surface layer of each fiber had been conjugated with quaternary ammonium EPTMAC groups, with the amount of EPTMAC added during preparation determining the degree of molar substitution (MS) of the cationic groups. In addition, increasing the MS of the modified NFBC resulted in a positive surface charge that led to an increase in the transparency of the nanofiber dispersion owing to electrostatic repulsion between nanofibers. Despite these differences, the fiber morphologies and crystal structures of the modified fibers were almost identical to those of pristine NFBC, suggesting that EPTMAC selectively reacts with the surface hydroxyl groups of NFBC. In addition, bacterial cell culture experiments revealed that the modified nanofibers are antimicrobial against Klebsiella pneumoniae, a Gram-negative bacterium, most likely because the surface of the modified NFBC is positively charged. Therefore, the quaternary-ammonium-salt-modified NFBC is a functional nanofiber endowed with both nanofiber features and antimicrobial properties and can possibly be used in fiber-reinforced nanofillers and as a flocculant for water-based paints and polar resins.

Chitosan Stabilised Iron Containing Nanoparticles For Photocatalytic Hydrogen Generation

Metal nonoparticles stabilized by polymers is emerging as a new class of materials having entirely new physico-chemical properties as that of bulk and atom both. Stabilizers play important role in protecting the nanoparticles and also contributes in improvising the overall surface area. Chitosan, a natural polymer is selected as a stabilizer for the synthesis of iron containing nanoparticles. These nonoparticles are thoroughly characterized by using BETsurface area, FTIR, TEM and XPS. TEM image is showing well dispersed nanofibers with average size of 13nm. XPS data supports the formation of Fe2O3 type structure with O1s binding energy at 534.5 eV and Fe 2P3/2 and Fe 2P1/2 binding energies at 712eV and 723.2 eV. BET Surface area value is 36.72m2 /g with pore size of 145.16 and pore volume of 0.1332 cm3 /g. This synthesized nanomaterial was evaluated for photocatalytic hydrogen generation via water splitting reaction. Iron containing nanoparticles are showing excellent photocatalytic activity with hydrogen generation yield of 55.5 mmoles h-1g -1 of photocatalyst. The nanoparticles are magnetically retrievable and hence can be separated effectively from heterogeneous system.

Clearly transparent and air-permeable nanopaper with porous structures consisting of TEMPO-oxidized cellulose nanofibers.

Optically transparent materials that are air permeable have potentially numerous applications, including in wearable devices. From the perspective of sustainable development, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibers with widths of 3-4 nm have attracted considerable attention as starting materials for the preparation of clearly transparent nanofiber paper (denoted as conventional nanopaper). However, conventional nanopaper that is prepared from a water dispersion of TEMPO-oxidized cellulose nanofibers by direct drying exhibits poor air permeability owing to its densely packed layered structure. In this study, we prepared a clearly transparent and air-permeable nanopaper by applying filtration-based solvent exchange from high-surface-tension water to low-surface-tension ethanol and hexane, followed by drying under continuous vacuum filtration. The resulting hexane-exchanged nanopaper had a porous structure with individually dispersed and thin nanofiber networks and interlayer pore spaces. Owing to the tailored porous structures, the hexane-exchanged nanopaper provides similar clear transparency (total light transmittance and haze at 600 nm: 92.9% and 7.22%, respectively) and 106 times higher air permeability (7.8 × 106 mL μm m-2 day-1 kPa-1) compared to the conventional nanopaper. This study will facilitate the development of clearly transparent and air-permeable nanopapers to extend their functional applications.

3D printed polylactic acid (PLA) filters reinforced with polysaccharide nanofibers for metal ions capture and microplastics separation from water

The need for multifunctional, robust, reusable, and high-flux filters is a constant challenge for sustainable water treatment. In this work, fully biobased and biodegradable water purification filters were developed and processed by the means of three-dimensional (3D) printing, more specifically by fused deposition modelling (FDM).The polylactic acid (PLA) – based composites reinforced with homogenously dispersed TEMPO-oxidized cellulose nanofibers (TCNF) or chitin nanofibers (ChNF) were prepared within a four-step process; i. melt blending, ii. thermally induced phase separation (TIPS) pelletization method, iii. freeze drying and iv. single-screw extrusion to 3D printing filaments. The monolithic, biocomposite filters were 3D printed in cylindrical as well as hourglass geometries with varying, multiscale pore architectures. The filters were designed to control the contact time between filter’s active surfaces and contaminants, tailoring their permeance.All printed filters exhibited high print quality and high water throughput as well as enhanced mechanical properties, compared to pristine PLA filters. The improved toughness values of the biocomposite filters clearly indicate the reinforcing effect of the homogenously dispersed nanofibers (NFs). The homogenous dispersion is attributed to the TIPS method. The NFs effect is also reflected in the adsorption capacity of the filters towards copper ions, which was shown to be as high as 234 and 208 mg/gNF for TCNF and ChNF reinforced filters, respectively, compared to just 4 mg/g for the pure PLA filters. Moreover, the biocomposite-based filters showed higher potential for removal of microplastics from laundry effluent water when compared to pure PLA filters with maximum separation efficiency of 54 % and 35 % for TCNF/PLA and ChNF/PLA filters, respectively compared to 26 % for pure PLA filters, all that while maintaining their high permeance.The combination of environmentally friendly materials with a cost and time-effective technology such as FDM allows the development of customized water filtration systems, which can be easily adapted in the areas most affected by the inaccessibility of clean water.

Magnetic nanocellulose: influence of structural features on conductivity and magnetic properties

Magnetic cellulose (MC) is prepared by hydrolysis of iron precursors in an aqueous dispersion of cellulose nanofibers. A thin, flexible film was then prepared by removing the water and drying the sample in a hot press at 110 °C followed by the removal of the water. Structural analysis of MC was performed and correlated with the measurement of electromagnetic properties. The magnetic cellulose showed high magnetic saturation of 68 emu/g with characteristic superparamagnetic behaviour, and conductivity in a range of semiconductors, with an increase of direct current (DC) conductivity with increasing temperature. Modification of cellulose with Fe3O4 has a positive effect on the DC conductivity and lower limit that needs to be exceeded to achieve a stable and sustainable conductivity in the range of ~ 5–20 × 10–9 (Ω cm)−1 @30 °C is 65 wt% of the Fe3O4 for studied MC composites. The surface roughness of the magnetic cellulose shows a dynamic change with increasing temperature, which is closely related to the enhancement of MC conductivity. A theoretical model of the conductivity is calculated based on continuous 2D percolation and shows an interesting agreement with the experimental results.

Researching proton conduction behavior at subzero temperature of lamellar anhydrous proton exchange membranes

For proton exchange membranes (PEMs), many studies have been going into the anhydrous PEMs with the working temperature exceeding 110 °C and the humidified PEMs below 80 °C. However, the PEMs fracture can cause cold start failure while the fuel cell vehicles are exposed to a colder climate for a long-time parking. In this study, low temperature PEMs (LTPEMs) with the lamellar structure was constructed through the well-ordered dispersion of Kevlar nanofibers, thioglycollic acid capping cadmium telluride (CdTe) nanocrystals and polyurethane (PU) polymer, expecting to enhance the mechanical property and improve the proton conductivity at subzero temperature. The successful preparation of the LTPEMs with spin coating technique and layer by layer self-assembly technique was determined by the structure analysis and the property measurement. The compact microstructure was constructed owing to electrostatic attraction and intermolecular hydrogen bonding. In the prepared (Kevlar/CdTe)25/(PU/CdTe)100 membrane, Kevlar nanofibers provided the support and PU molecular chains guaranteed enough flexibility. Furthermore, a massive amount of CdTe nanocrystals could tolerate low temperature condition, which was derived from the high proton conductivity at subzero temperature. Specifically, the (Kevlar/CdTe)25/(PU/CdTe)100/PA membrane exhibited the proton conductivity values of (2.23 ± 0.39) × 10−2 S/cm at −30 °C, (6.59 ± 0.15) × 10−2 S/cm at 0 °C and (1.73 ± 0.04) × 10−1 S/cm at 30 °C. Most importantly, the fine proton conductivity stability was revealed from the proton conductivity values of 3.72 × 10−2 S/cm at −30 °C after a thirty-cycle heating/cooling process and 3.53 × 10−2 S/cm at −30 °C after a 1020 h non-stop test. Furthermore, there was a slight decrease on the tensile stress with PA molecules doping owing to the compact microstructure.

Nanofiber Concrete: Multi-Level Reinforcement

Concrete is the most commonly used building material worldwide. One of its main disadvantages is the fragility of fracture and low crack resistance. The use of dispersed reinforcement of concrete composites is a promising direction in solving this type of problem. Dispersed fibers, evenly distributed over the entire volume of the material, create a spatial frame and contribute to the inhibition of developing cracks under the action of destructive forces. In order to increase the fracture toughness of concrete, dispersed fiber reinforcement is increasingly used in practice. The beginning of crack nucleation occurs at the nanoscale in the cement matrix. Thus, the use of nano-reinforcement with dispersed nanofibers can have a positive effect on the crack resistance of the cement composite. It is proposed to consider carbon nanotubes as such nanofibers. The presence of carbon nanofibers changes the microstructure and nanostructure of cement modified with carbon nanotubes. The result of the processes occurring in capillaries and cracks are deformations in the intergranular matrix, the free flow of which is prevented by rigid clinker grains and nanocarbon tubes, which creates a certain stress intensity at the tips of the separation cracks. The working hypothesis is confirmed that the required fracture toughness of structural concrete is provided by multi-level reinforcement: at the level of the crystalline aggregate of cement stone – carbon nanotubes, and at the level of fine-grained concrete – various macro-sized fibers (steel, polymer). Reinforcement of a crystalline joint with carbon nanotubes leads to an increase in the fracture toughness of the matrix (cement stone) by 20 %, compressive strength by 12 %, and tensile strength in bending by 20 %. When reinforcing at the level of fine-grained concrete, we obtain a composite – nanofibre-reinforced concrete with fracture toughness.

Anti-Fouling, Adhesive Polyzwitterionic Hydrogel Electrodes Toughened Using a Tannic Acid Nanoflower

Conductive polyzwitterionic hydrogels with good adhesion properties show potential prospect in implantable electrodes and electronic devices. Adhesive property of polyzwitterionic hydrogels in humid environments can be improved by the introduction of catechol groups. However, common catechol modifiers can usually quench free radicals, resulting in a contradiction between long-term tissue adhesion and hydrogel toughness. By adding tannic acid (TA) to the dispersion of clay nanosheets and nanofibers, we designed TA-coated nanoflowers and nanofibers as the reinforcing phase to prepare polyzwitterionic hydrogels with adhesion properties. The hydrogel combines the mussel-like and zwitterionic co-adhesive mechanism to maintain long-term adhesion in underwater environments. In particular, the noncovalent cross-linking provided by the nanoflower structure effectively compensates for the defects caused by free-radical quenching so that the hydrogel obtained a high stretchability of over 2900% and a toughness of 1.16 J/m3. The hydrogel also has excellent anti-biofouling property and shows resistance to bacteria and cells. In addition, the hydrogel possesses a low modulus (<10 kPa) and ionic conductivity (0.25 S/m), making it an ideal material for the preparation of implantable electrodes.

Developing Electrospun Ethylcellulose Nanofibrous Webs: An Alternative Approach for Structuring Castor Oil.

The development of environment-friendly natural polymer gel-like dispersions in oil media, with functional properties, in terms of formulation design and synthesis protocol, is still a cutting-edge research area for many applications. The aim of this work was to study the manufacture of electrospun ethylcellulose (EC) nanofibrous webs and to examine their usage to thicken vegetable oils as an alternative approach. The role of concentration, molecular weight (Mw), and binary solvent systems on the electrospinnability of EC and subsequently on the rheological properties of EC nanofiber dispersions in castor oil was investigated. It was observed that, for each Mw, defect-free nanofibers were produced above a critical concentration, corresponding to about 2.5 the entanglement concentration (Ce). The average fiber diameter increased with both Mw and EC concentrations. Dielectric constant and dipole moment of binary solvent systems influenced the morphology of the EC nanofiber web. The morphology of the micro- and nanoarchitectures generated played a key role in the physical stabilization and rheological behavior of electrospun EC dispersions. The storage modulus (G') of EC dispersions was correlated with both the spinning solution concentration and average fiber diameter. Furthermore, electrospun EC nanofiber dispersions were compared with EC oleogels obtained by traditional thermogelation from thermorheological and tribological points of view. Overall, this work proposes an efficient and innovative approach to produce bio-based oleogel-like dispersions with great potential in different sectors such as pharmaceuticals, food, or lubricants.