Abstract Fretboards of string instruments are usually made of rare woods that commonly have a high density, strength, and hardness; further, they are wear resistant, uniform in texture, and feature an elegant color. To reduce the consumption of scarce timber resources, especially of endangered tropical hardwood species, suitable replacement materials should be identified. The substitute can be either common tree species having similar characteristics, or fast-growing plantation wood that has undergone modifications to match the performance of precious woods. This study compares the anatomical structure, physical features, mechanical properties, and surface color of three precious woods traditionally used in fretboards (ebony, Indian rosewood, and African blackwood) against maple, which is used for the backboard, ribs, and necks of string instruments. Based on the data, a set of performance evaluation indices for selecting alternative materials for fretboards is proposed. In specific, the replacement wood should be a diffuse-porous tropical hardwood with few vessels and a smaller diameter, thick fibrous walls, and a cell wall rate of more than 50%. In terms of physical properties, it should have low swelling coefficients for moisture and water absorption, and dimensional stability. The replacement should also display hardness values greater than 9.0 kN in the cross-section and greater than 6.0 kN in the tangential and radial sections. Further, it should have a high modulus of rupture (> 149 MPa) and elasticity (> 14.08 GPa), good impact bending strength, and good wear resistance (80–150 mg/100 r ). To satisfy the traditional aesthetics, the wood surface color should be black, dark brown, or dark purple-brown, with colorimetric parameters in the range of 0.0 < L* < 30.0, 0.0 < b* < 6.0, and an a* value as small as possible. The evaluation indicators used for searching potential high-quality alternative tree species are not the same as those for replacing traditional fretboard materials using modified fast-growing plantation wood. The physical and mechanical properties and the surface color of traditional precious fretboard wood are important evaluation indicators for whether the modified fast-growing plantation wood can replace the traditional fretboard wood.
Flexible supercapacitors assembled with two-dimensional materials have become a research hotspot in recent years. Here, we have prepared two-dimensional nanomaterial MoS2 and SWCNT, CNF aerogel composite electrode, and its flexible all-solid-state supercapacitor. SWCNT can inhibit the accumulation of MoS2 nanosheets and enhance the conductivity of the composite electrode. CNF can improve the dispersion uniformity of MoS2 and SWCNT, and endow the composite electrode with a high specific surface area (328.86 m2 g-1) and excellent flexibility. MoS2-SWCNT/CNF supercapacitor has a good rectangular CV curve and symmetrical triangular GCD curve. The CV curve of the MoSCF3 supercapacitor with the highest MoS2-SWCNT content remains rectangular even at the scanning rate of 2000 mV s-1. Its voltage window can reach 1.5 V. MoS2-SWCNT/CNF supercapacitor has a specific capacity of 605.32 mF cm-2 (scanning rate of 2 mV s-1) and 30.34 F g-1 (0.01 A g-1), an area specific energy of 35.61 mWh cm-2 (area specific power of 0.03 mW cm-2), and extremely high cycle stability (91.01% specific capacity retention rate after 10 000 cycles) and good flexibility. The fine nanocomposite structure gives MoS2-SWCNT/CNF supercapacitor impressive electrochemical performance and excellent flexibility, which can be used in the field of portable electronic devices and flexible devices.
Furfuryl alcohol (FA) is an environmentally friendly chemical modifier that effectively improves the dimensional stability and mechanical properties of wood. The drawbacks of high brittleness and low toughness of furfurylated wood restrict its applications. Epoxidized soybean oil (ESO) is a biomass-derived resource and was added to FA solution as a novel plasticizer in this study. The FA–ESO solution was used to modify radiate pine wood obtained from fast-growing trees sourced from plantations. The microscopic morphology, chemical structure, and mechanical performance of the FA–ESO-modified wood were tested to evaluate the plasticizing effect of ESO on the performance of the modified wood and to assess the toughening mechanisms. It was found that ESO was an effective plasticizer that increased the toughness indictors of the furfurylated wood. When the plasticizer concentration was 20 wt %, the ultimate tensile stress and impact bending strength of the FA–ESO-modified wood were increased by 70% and 10%, respectively, compared to those of the furfurylated wood. In addition, the modified wood had a high density (approximately 910 kg/m3), good dimensional stability (antiswelling efficiency of approximately 82%), and superior mechanical properties (modulus of rupture, modulus of elasticity, and static hardness increased by 16%, 25%, and 18%, respectively). However, these exceptional performances were associated with the high molecular weight, good hydrophobicity, and proper chemical structure of ESO and the appropriate intermolecular interactions between ESO and FA resin chains. The hydrophobic FA resin and FA–ESO thermosets filled the wood cell walls and cell lumens, which improved the wood dimensional stability. Furthermore, the ring-opening polymerization reaction between FA and ESO and the long, flexible aliphatic chains of ESO increased the flexible properties of the FA resins and improved the toughness of the modified wood. The FA–ESO-modified wood had an excellent appearance and physical and mechanical properties comparable to those of tropical hardwood, which could expand the application of radiata pine to musical instruments.
We herein report the use of natural sliced wood veneer as a porous lightweight substrate for supercapacitor electrodes, where PANI/RGO and PPy/RGO were employed as active materials, and both wood electrodes showed good electrochemical performance.
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