Lu Shen,Yinfu Luo,Long Ni,Mei Liang,Shengtai Zhou,Huawei Zou
It is a great challenge to prepare lightweight porous materials with high-efficiency broadband sound absorption and good mechanical properties. In this work, a series of melamine foams (MF) which were decorated by silver (Ag) and cellulose nanofiber (CNF) were prepared by the in-situ deposition and freeze-drying method. The deposition of Ag particles on the foam skeleton formed nanopores, and hierarchical porous structures were constructed along with the existence of micropores in MF. In addition, the formation of filamentous CNF structure further optimized the pore structure, which resulted in achieving excellent broadband sound absorption and enhanced mechanical properties of corresponding composite foams. Specifically, Ag@MF-6-CNF achieved more than 95 % sound absorption efficiency in the range of 2500–6400 Hz. Besides, the compressive strength of Ag@MF-6-CNF reached 13.8 kPa at a strain rate of 50 %, which was 75 % higher than pure MF. The proposed method provided a reference for preparing lightweight porous materials for noise attenuation applications in industrial sectors.
Glyphosate, a widely used herbicide, is prone to residue in the environment that may cause harm to humans. In this work, titanium ion-modified melamine foams (MF/PDA/Ti 4+ ) were prepared as sorbents to achieve rapid extraction of glyphosate by pipette-tip solid-phase extraction (PTSPE). The MF/PDA/Ti 4+ was characterized by SEM, EDS, XPS, and TGA, and its adsorption properties were evaluated by adsorption kinetics and isotherm experiments. The porous structure and good mechanical properties of MF made the MF/PDA/Ti 4+ fill into the pipette-tip easily and could achieve low back pressure. The developed PTSPE method showcased short extraction time (<2 min) for glyphosate and the limits of detection (LOD, 3σ/k) was 4.9 μg/L. It was applied in aqueous samples (tap water, lake water, tea drink, and orange juice) with recoveries ranging from 82.8 % to 108.2 % and the relative standard deviation (RSD, n = 3) was less than 7.7 %, demonstrating broad perspectives on the extraction of glyphosate from the aquatic and terrestrial environment.
Shuang Song,Hao Yang,Chunping Su,Zhibin Jiang,Zhong Lu
We herein report the fabrication of recyclable, stable and cost-effective superhydrophobic reduced graphene oxide modified melamine foam (RGMF) through ultrasonic-microwave synergistic method for the first time. In the synthesis process, ultrasonic and microwave irradiation not only shortened the reduction time of graphene oxide (GO) with the existence of reducing agent, but also considerably enhanced the firmness of reduced graphene oxide (rGO) anchored onto the melamine foam (MF). The structure and property of the obtained RGMF were characterized by XRD, Raman, SEM and contact angle measurements. The results showed that the skeletons of MF were completely covered with rGO layers which were compact and full of wrinkles. The as-prepared RGMF was superhydrophobic without further modification. Besides, the RGMF showed excellent selective adsorption capacity of various oils and organic solvents from water. The maximum oil adsorption capacity was 112 times of the weight of the initial MF, and the adsorption capacity of the RGMF did not deteriorate after it was reused 20 times. More importantly, the RGMF showed good stability against cavitation erosion and corrosion liquids. All these features made the as-prepared material an ideal candidate for removal and collection of oils and organic solvents from water.
With the progress of intelligent electronic equipment, flexible and wearable strain sensors are being widely used in various applications such as electronic skins and smart robot. In this work, we proposed a facile method for the preparation of stretchable strain sensors as well as compressible strain sensors by using commercially available melamine form (MF). Firstly, MF was coated with reduced graphene oxide (rGO) to construct conductive networks via layer-by-layer assembly of polyethyleneimine and graphene oxide followed by chemical reduction. Thermoplastic elastomer poly (styrene- b -ethylene-butylene- b -styrene) (SEBS) was then infused into the MF@rGO scaffolds through solution absorption method. By adjusting the concentration of SEBS solution used, stretchable and compressible strain sensors were fabricated and both of them exhibited excellent mechanical properties, sensitive responsiveness and electromechanical durability. The deformation capacity of these two types of sensors could reach as high as 50% strain and the maximum gauge factors of stretchable and compressible strain sensors was 2.43 and 1.74, respectively. Stable signals during at least 1000 cycles for both stretchable and compressible strain sensors were well maintained. The potential sensing application of real-time monitoring of human motions was also demonstrated.
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