ABSTRACT
Chitin nanofibrils (ChNF) sourced from discarded marine biomass are shown as effective stabilizers of carbon nanomaterials in aqueous media. Such stabilization is evaluated for carbon nanotubes (CNT) considering spatial and temporal perspectives by using experimental (small-angle X-ray scattering, among others) and theoretical (atomistic simulation) approaches. We reveal that the coassembly of ChNF and CNT is governed by hydrophobic interactions, while electrostatic repulsion drives the colloidal stabilization of the hybrid ChNF/CNT system. Related effects are found to be transferable to multiwalled carbon nanotubes and graphene nanosheets. The observations explain the functionality of hybrid membranes obtained by aqueous phase processing, which benefit from an excellent areal mass distribution (correlated to piezoresistivity), also contributing to high electromechanical performance. The water resistance and flexibility of the ChNF/CNT membranes (along with its tensile strength at break of 190 MPa, conductivity of up to 426 S/cm, and piezoresistivity and light absorption properties) are conveniently combined in a device demonstration, a sunlight water evaporator. The latter is shown to present a high evaporation rate (as high as 1.425 kg water m-2 h-1 under one sun illumination) and recyclability.
ABSTRACT
This work focuses on multi-stimuli-responsive materials with distinctive abilities, that is, color-changing and shape-memory. Using metallic composite yarns and polymeric/thermochromic microcapsule composite fibers, processed via a melt-spinning technique, an electrothermally multi-responsive fabric is woven. The resulting smart-fabric transfers from a predefined structure to an original shape while changing color upon heating or applying an electric field, making it appealing for advanced applications. The shape-memory and color-changing features of the fabric can be controlled by rationally controlling the micro-scale design of the individual fibers in the structure. Thus, the fibers' microstructural features are optimized to achieve excellent color-changing behavior along with shape fixity and recovery ratios of 99.95% and 79.2%, respectively. More importantly, the fabric's dual-response by electric field can be achieved by a low voltage of 5 V, which is smaller than the previously reported values. Above and beyond, the fabric is able to be meticulously activated by selectively applying a controlled voltage to any part of the fabric. The precise local responsiveness can be bestowed upon the fabric by readily controlling its macro-scale design. A biomimetic dragonfly with the shape-memory and color-changing dual-response ability is successfully fabricated, broadening the design and fabrication horizon of groundbreaking smart materials with multiple functions.
ABSTRACT
Herein, a cellulose-based aerogel, containing graphene-oxide (GO), chemically-reduced-GO (CrGO), and thermally-reduced-GO (TrGO), has been facile prepared to investigate mechanical and electrical properties as well as meso-(nano)structure features. The effect of reduction processes on the cellulose/GO aerogel was tracked by FT-IR spectroscopy and EDS analysis, confirming the accomplishment of reduction processes-carbon/oxygen (C/O) ratio asserted it evidently. The formation of porous structure has been declared using SEM micrographs, and then, Mercury-porosimetry and BET tests revealed meso-(nano)structure of aerogels. The improvement of mechanical behavior with the increment of Young modulus has been seen by raising C/O ratio. Low thermal and moderate electrical conductivity was measured for the reduced aerogels concerning the addition of different conductive fillers. With introducing a novel method for studying shape memory properties, the best shape recovery rate was obtained for thermally reduced aerogel in an aqueous situation by simultaneously applying mechanical force and an electrical field (various voltages).
Subject(s)
Graphite , Nanocomposites , Cellulose/chemistry , Gels/chemistry , Graphite/chemistry , Nanocomposites/chemistry , Spectroscopy, Fourier Transform InfraredABSTRACT
This study aims to induce antibacterial and superhydrophobic properties on the surface of thermoplastic polyurethane (TPU) sheets via an improved phase separation process through application of polyvinyl chloride (PVC) thin films. Porous PVC thin films were produced using different amounts of ethanol as nonsolvent. However, the created porosity was not sufficient to achieve superhydrophobicity. To improve the phase separation process, the silver phosphate nanoparticles were first synthesized and then added to the solution. According to scanning electron microscopy and X-ray photoelectron spectroscopy results, the nanoparticles were majorly localized at the bulk of PVC films. A direct relationship was found between the level of porosity and superhydrophobicity. An exceedingly high amount of nanoparticles had a deteriorating influence on porosity and superhydrophobicity. The optimum sample was found to be durable against liquids with different pH values. In contrast to the good resistance of superhydrophobic sample at elevated temperatures (80 °C), a sticky behavior was obtained upon exposure to 120 °C. The level of bacterial adhesion for the superhydrophobic sample was drastically declined (>99%) with respect to the pure PVC film in case of S. aureus and E. coli bacteria after an incubation time of 24 h. In conclusion, the hybrid of superhydrophobic behavior and an antibacterial material such as silver phosphate nanoparticles exhibited a promising potential in achieving antibacterial surfaces.
