In recent years, solving environmental problems has become an urgent task with the drain of materials based on exhaustible petroleum and the aggravation of environmental pollution. ...Environment-friendly material has attracted much attention such as natural plant fiber reinforced composites. Bamboo fiber, as a number of natural plant fiber, possesses many excellent properties including low density, low cost, high strength, renewability and complete degradability. But there are few review articles about bamboo fiber reinforced composites and most of them are classified according to materials especially lack of interfacial bonding mechanism. To attack these problems, this review will not only discuss the preparation and performance of bamboo fiber reinforced polymer composites but also take a profound look at their interfacial bonding mechanism. This review will also explore characteristics and processes of physical and chemical modification. Synergism of physical and chemical reactions receives increasing attention. Finally, the opportunities and challenges of bamboo fiber reinforced polymer composites are presented. We hope that this paper will provide a serviceable review for future research on BF reinforced polymer.
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•A bilayer hydrogel was prepared by interfacial reaction in one step.•A synergistic function exists between the two layers of hydrogel.•High strength, toughness and durable water ...retention were achieved.•The bilayer hydrogel shows well antibacterial ability and accelerated healing effect.
The main limit of hydrogel used as an independent wound dressing is its poor water retention, brittleness, and weak skin adhesion. Focusing on it, the macromolecular cross-linked chitosan and polyacrylamide double network hydrogel (C-A) is chosen as a functional layer, another robust poly(vinyl alcohol)-polyacrylamide/glycerin (P-A) protective layer is designed to cover its surface, an interfacial reaction happens to link two layers tightly for achieving the function synergy. In this double-layer hydrogel (DH) dressing, the surface P-A layer with strong water locking ability could keep the wound surface moist for a long time, high strength and toughness make the dressing maintain integrity under large deformation and stress to strengthen wound protection, and the C-A layer with modest adhesion ensures the dressing fit the skin, the synergistic swelling ability could guarantee the fast absorption for the wound exudate. Moreover, in vitro and in vivo tests, the DH dressing exhibits excellent antibacterial and cytocompatibility, it could significantly accelerate skin tissue regeneration and wound closure than the commercial hydrocolloid dressings. In general, this DH dressing is easy to prepare and shows superior comprehensive performance, revealing the great potential for use as an independently applied wound dressing.
In order to solve the contradiction that the conductivity, tensile properties and antibacterial properties of traditional hydrogels cannot coexist at the same time, multifunctional CMCS/GG/PAM ...double-network (DN) hydrogels are prepared by introducing carboxymethyl chitosan (CMCS) into gellan gum/polyacrylamide (GG/PAM) double-network (DN) hydrogels. CMCS not only endows hydrogels with good antibacterial properties, but also enhances the interaction between GG and PAM networks. The physically crosslinked GG network and chemically crosslinked PAM network synergistically enhance the mechanical performances of the hydrogel, and the mechanical performances of hydrogel can be controlled by adjusting the dosage of GG and CMCS. The hydrogel can reach a fracture stress of 198.4 kPa and a fracture strain of 797.8%. CMCS/GG/PAM DN hydrogels have good adhesion properties, can be firmly attached to aluminum, titanium, pig skin, stainless steel and other solid surfaces. CMCS/GG/PAM DN hydrogels also have excellent biocompatibility, conductive strain sensitivity with a wide sensing range of 0–350%, short response time of 40 ms, and can monitor human movement state and facial micro-expression in real time, so as to be used as a safe antibacterial flexible sensor for human health monitoring.
•Double-network hydrogels are prepared by introducing carboxymethyl chitosan into gellan gum/polyacrylamide double-network hydrogels.•The hydrogels exhibited excellent mechanical properties, antibacterial properties, high conductivity strain sensitivity and stability.•A wearable strain sensor based on the hydrogel was assembled and evaluated.
Pt-based ultrathin nanowires (NWs) are considered as one of the most intriguing catalysts for fuel cells. However, the delicate controllability of surface structure of ultrathin NWs to regulate their ...catalytic performances is still a challenge. Here, two kinds of one-nanometer-thick Pt-based NWs with smooth surfaces (S-NWs) and rough surfaces (R-NWs) are demonstrated, in which the combined use of hexadecyltrimethylammonium bromide and oleylamine plays an essential role, as they could form soft-templates to direct the growth of NWs. Due to its high-density of low-coordinated sites on the surface, Pt-based R-NWs exhibit higher oxygen reduction reaction (ORR) activities but lower stabilities than corresponding S-NWs. Notably, Pt
0.78
Ni
0.22
R-NWs possess the highest mass activity (1.07 A·mg
Pt
−1
) and specific activity (1.02 mA·cm
−2
) among all Pt-based NWs. After 10,000 sweeping cycles, the mass activity still exhibits 5.7-fold enhancement compared to the corresponding commercial Pt/C. This work presents a new approach to delicately control the surface structure of ultrathin Pt-based NWs as advanced ORR catalysts.
Well-defined PtNi nanocrystals represent one of the most efficient electrocatalysts to boost the oxygen reduction reaction (ORR), especially in the shape of octahedrons, nanoframes, and nanowires. ...However, the synthesis of complex PtNi nanostructure is still a great challenge. Herein, we report a new class of PtNi hexapods with high activity and stability toward ORR. The hexapods are prepared by selective capping and simultaneous corrosion. By controlling the oxidative etching, PtNi polyhedrons and nanoparticles are obtained, respectively. The intriguing hexapods are composed of six nanopods with an average length of 12.5 nm. Due to their sharp tips and three-dimensional (3D) accessible surfaces, the PtNi hexapods show a high mass activity of 0.85 A mg
at 0.9 V vs. RHE, which are 5.4-fold higher than commercial Pt/C, also outperforming PtNi polyhedrons and PtNi nanoparticles. In addition, the mass activity of PtNi hexapods maintains 92.3% even after 10,000 potential cycles.
With the development of science and technology and the improvement of people's living standards, air pollution as the main environmental problem has become increasingly prominent. Promoted by economy ...and technology, architecture is not only to satisfy people's living needs, but also to integrate building functions and user experience. This leads to building energy consumption increasing, which is in line with industry and transportation, becoming the world's major energy consumers. In the tide of sustainable development and green building, energy saving, consumption reduction, green and health have become the common pursuit of architecture. However, in the process of production and construction, the formation and release of CO2 during the calcination of ordinary Portland cement raw materials has resulted in an increase in carbon emissions. Therefore, the traditional cement materials have gradually failed to meet the concept of green building because of its high pollution and energy consumption in production. With more and more stringent restrictions on pollutant emission in various countries, the environmental cost of cement production will be higher and higher. Continuously increasing environmental costs have forced major enterprises to invest a large amount of cost in energy saving and environmental protection of products. Geopolymer concrete has also developed rapidly. With the unremitting efforts of scholars at home and abroad, after nearly 40 years of development, as a new type of green building material, geopolymer concrete has undergone a transformation from metakaolin to industrial solid waste as raw materials, with low energy consumption, low carbon emissions, easy preparation, and excellent compressive and flexural strength, acid-alkali corrosion resistance, shrinkage and expansion rate, quick drying, quick hardening and durability. In contrast, it is one of the best substitutes for ordinary Portland cement-based materials. It has broad application prospects in the fields of construction, materials, military, nuclear and other fields, and has been preliminarily applied. This paper reviews the research progress of geopolymer concrete at home and abroad, summarizes the development of raw material composition, manufacturing technology, performance and application prospects, and puts forward the problems faced by geopolymer concrete technology.
In this work, graphene grown by chemical vapour deposition is transferred onto a micron-scale hole array (MSHA) substrate by a polymer-free transfer process. The graphene adheres to the walls of the ...microholes and complies with the morphologies of the micron-scale hole substrate. In contrast to previous reports of the partial-transparency of the wettability of graphene on a plane substrate, the wettability of graphene on a micro-scale hole array substrate is found to be hydrophobic with a contact angle of 93.1°. This is quite different from that of graphene on a planar SiO
2
/Si substrate, which is hydrophilic with a contact angle of 83.0°. We find that a micron-scale hole array substrate has a regulation effect on the wettability of graphene when the graphene almost completely complies with the morphology of the micron-scale hole array substrate surface and the change from hydrophilic to hydrophobic provides a guide for designing surfaces with controllable wettability.
When graphene almost completely complies with the morphology of a SiO
2
micron-scale hole array (MSHA) substrate, the effect of graphene's surface morphology to the wettability of graphene will be greatly facilitated by the regulation effect of MSHA.
In order to develop better wound dressings, a novel chitosan hydrogel (Cn-Nm gel) was designed and fabricated by using aldehyde-4-arm polyethylene glycol (4r-PEG-CHO) to crosslink the chitosan ...dissolved in alkaline solution, amino-4-arm polyethylene glycol (4r-PEG-NH2) was chosen as the additive simultaneously. The special dissolution technique and macromolecular crosslinking structure endows the Cn-Nm gels with better performance than that of gels prepared by acid dissolving method with micromolecule crosslinker. First, Cn-Nm gels own strong toughness with 500 kPa tensile strength and 1000% elongation, about 400% swelling ratio and fast water absorption rate. Second, about 300 kPa adhesive strength and strippability between the gels and skin is achieved. More importantly, Cn-Nm gels show nearly 100% antibacterial rate towards Escherichia coli and Staphylococcus aureus. Excellent biocompatibility is also proved by the mouse fibroblasts tests. All of the performance makes this developed chitosan-based gel be the potential candidate as a wound dressing.
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