Synthesis of superhydrophobic silica nanofibrous membranes with robust thermal stability and flexibility via in situ polymerization

Fabrication and characterization of flexible natural cellulosic fiber composites through collaborative modification strategy of sodium hydroxide and γ-Aminopropyl triethoxysilane

The primary purpose of this work is to study the fabrication of a flexible natural cellulosic fiber composite. In this respect, natural cellulosic fiber was obtained by modified poplar wood fiber through sodium hydroxide (NaOH) and γ-Aminopropyl Triethoxysilan. Then, the composites were fabricated by hot-pressing the modified wood fibers and polyurethane following characterization. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM) observation results confirmed that some of the hemicellulose and lignin were removed from wood fibers after NaOH modification and successfully grafted with alkoxy structures after KH550 modification. NaOH&KH550 modification improved the interfacial compatibility between poplar wood fibers and polyurethane. The flexibility of the composites was improved (the slenderness value was reduced by 113 %), allowing flexible deformations such as bending, twisting, and knotting. In addition, thermal stability, tensile strength (increased by 105 %), elongation at the break (increased by 125 %), and water resistance were increased. This flexible natural cellulosic fiber composite is expected to be applied in the veneering of curved materials and special-shaped structure furniture, providing a theoretical basis for improving the added value of wood-based composites.

Bending Flexibility of Moso Bamboo (Phyllostachys Edulis) with Functionally Graded Structure

As one of the most renewable and sustainable resources on Earth, bamboo with its high flexibility has been used in the fabrication of a wide variety of composite structures due to its properties. A bamboo-based winding composite (BWC) is an innovative bamboo product which has revolutionized pipe structures and their applications throughout China as well as improving their impact on the environment. However, as a natural functionally graded composite, the flexibility mechanism of bamboo has not yet been fully understood. Here, the bending stiffness method based on the cantilever beam principle was used to investigate the gradient and directional bending flexibility of bamboo (Phyllostachys edulis) slivers under different loading Types during elastic stages. Results showed that the graded distribution and gradient variation of cell size of the fibers embedded in the parenchyma cells along the thickness of the bamboo culm was mainly responsible for the exhibited gradient bending flexibility of bamboo slivers, whereas the shape and size difference of the vascular bundles from inner to outer layers played a critical role in directional bending flexibility. A validated rule of mixture was used to fit the bending stiffness under different loading Types as a function of fiber volume fraction. This work provides insights to the bionic preparation and optimization of high-performance BWC pipes.

Rational design of materials interface at nanoscale towards intelligent oil-water separation

Oil-water separation is critical for the water treatment of oily wastewater or oil-spill accidents. The oil contamination in water not only induces severe water pollution but also threatens human beings' health and all living species in the ecological system. To address this challenge, different nanoscale fabrication methods have been applied for endowing biomimetic porous materials, which provide a promising solution for oily-water remediation. In this review, we present the state-of-the-art developments in the rational design of materials interface with special wettability for the intelligent separation of immiscible/emulsified oil-water mixtures. A mechanistic understanding of oil-water separation is firstly described, followed by a summary of separation solutions for traditional oil-water mixtures and special oil-water emulsions enabled by self-amplified wettability due to nanostructures. Guided by the basic theory, the rational design of interfaces of various porous materials at nanoscale with special wettability towards superhydrophobicity-superoleophilicity, superhydrophilicity-superoleophobicity, and superhydrophilicity-underwater superoleophobicity is discussed in detail. Although the above nanoscale fabrication strategies are able to address most of the current challenges, intelligent superwetting materials developed to meet special oil-water separation demands and to further promote the separation efficiency are also reviewed for various special application demands. Finally, challenges and future perspectives in the development of more efficient oil-water separation materials and devices by nanoscale control are provided. It is expected that the biomimetic porous materials with nanoscale interface engineering will overcome the current challenges of oil-water emulsion separation, realizing their practical applications in the near future with continuous efforts in this field.

Engineering Ceramic Fiber Nanostructures Through Polymer-Mediated Electrospinning

Electrospinning is increasingly used as a simple and straightforward technique to fabricate one-dimensional fibers from both organic and inorganic materials. These one-dimensional fibers with controlled sizes possess some unique features such as large surface area to volume ratio, high porosity, and low density. Compared to other conventional materials, these features make them attractive for applications such as energy harvesting, energy storage, super-hydrophobic membranes, and sensors. This chapter provides an overview on the synthesis of inorganic fibers through polymer-mediated electrospinning. Some of the common techniques employed by many researchers, such as solgel combined with electrospinning, emulsion electrospinning, and electrospinning combined with solid–gas reaction, to fabricate metal oxide fibers are discussed. In addition, techniques to fabricate ceramic and metal oxide fibers having different morphologies and hierarchical structures are described. Recent applications of electrospun metal oxide fibers are finally highlighted with a focus on filtration, sensors, photocatalysis, and energy.

Sunlight-Sensitive Anti-Fouling Nanostructured TiO2 coated Cu Meshes for Ultrafast Oily Water Treatment

Nanostructured materials with desired wettability and optical property can play an important role in reducing the energy consumption of oily water treatment technologies. For effective oily water treatment, membrane materials with high strength, sunlight-sensitive anti-fouling, relative low fabrication cost, and controllable wettability are being explored. In the proposed oily water treatment approach, nanostructured TiO₂-coated copper (TNS-Cu) meshes are used. These TNS-Cu meshes exhibit robust superhydrophilicity and underwater oleophobicity (high oil intrusion pressure) as well as excellent chemical and thermal stability (≈250 °C). They have demonstrated high separation efficiency (oil residue in the filtrate ≤21.3 ppm), remarkable filtration flux (≥400 kL h⁻¹m⁻²), and sunlight-sensitive anti-fouling properties. Both our theoretical analysis and experimental characterization have confirmed the enhanced light absorption property of TNS-Cu meshes in the visible region (40% of the solar spectrum) and consequently strong anti-fouling capability upon direct solar light illumination. With these features, the proposed approach promises great potential in treating produced oily wastewater from industry and daily life.

Superelastic and superhydrophobic nanofiber-assembled cellular aerogels for effective separation of oil/water emulsions

Many applications proposed for functional nanofibers require their assembly into a monolithic cellular structure. The ability to maintain structural integrity upon large deformation is essential to ensure a macroscopic cellular material that functions reliably. However, it remains a great challenge to achieve high elasticity in three-dimensional (3D) nanofibrous networks. Here, we report a strategy to create fibrous, isotropically bonded elastic reconstructed (FIBER) aerogels with a hierarchical cellular structure and superelasticity by combining electrospun nanofibers and the freeze-shaping technique. Our approach allows the intrinsically lamellar deposited electrospun nanofibers to assemble into elastic bulk aerogels with tunable porous structure and wettability on a large scale. The resulting FIBER aerogels exhibit the integrated properties of ultralow density (<30 mg cm(-3)), rapid recovery from 80% compression strain, superhydrophobic-superoleophilic wettability, and high pore tortuosity. More interestingly, the FIBER aerogels can effectively separate surfactant-stabilized water-in-oil emulsions, solely using gravity, with high flux (maximum of 8140 ± 220 L m(-2) h(-1)) and high separation efficiency, which match well with the requirements for treating the real emulsions. The synthesis of FIBER aerogels also provides a versatile platform for exploring the applications of nanofibers in a self-supporting, structurally adaptive, and 3D macroscopic form.

Superhydrophobic nanocoatings: from materials to fabrications and to applications

Superhydrophobic nanocoatings, a combination of nanotechnology and superhydrophobic surfaces, have received extraordinary attention recently, focusing both on novel preparation strategies and on investigations of their unique properties. In the past few decades, inspired by the lotus leaf, the discovery of nano- and micro-hierarchical structures has brought about great change in the superhydrophobic nanocoatings field. In this paper we review the contributions to this field reported in recent literature, mainly including materials, fabrication and applications. In order to facilitate comparison, materials are divided into 3 categories as follows: inorganic materials, organic materials, and inorganic-organic materials. Each kind of materials has itself merits and demerits, as well as fabrication techniques. The process of each technique is illustrated simply through a few classical examples. There is, to some extent, an association between various fabrication techniques, but many are different. So, it is important to choose appropriate preparation strategies, according to conditions and purposes. The peculiar properties of superhydrophobic nanocoatings, such as self-cleaning, anti-bacteria, anti-icing, corrosion resistance and so on, are the most dramatic. Not only do we introduce application examples, but also try to briefly discuss the principle behind the phenomenon. Finally, some challenges and potential promising breakthroughs in this field are also succinctly highlighted.

Silica nanofibrous membranes with ultra-softness and enhanced tensile strength for thermal insulation

Novel silica nanofibrous membranes with ultra-softness of 40 mN and enhanced tensile strength of 5.5 MPa were prepared for the first time via an electrospinning process, which exhibited an ultra-low thermal conductivity of 0.0058 W m⁻¹ K⁻¹.