Although advances in wireless technologies such as miniature and wearable electronics have improved the quality of our lives, the ubiquitous use of electronics comes at the expense of increased exposure to electromagnetic (EM) radiation. Up to date, extensive efforts have been made to develop high-performance EM absorbers based on synthetic materials. However, the design of an EM absorber with both exceptional EM dissipation ability and good environmental adaptability remains a substantial challenge. Here, we report the design of a class of carbon heterostructures via hierarchical assembly of graphitized lignocellulose derived from bamboo. Specifically, the assemblies of nanofibers and nanosheets behave as a nanometer-sized antenna, which results in an enhancement of the conductive loss. In addition, we show that the composition of cellulose and lignin in the precursor significantly influences the shape of the assembly and the formation of covalent bonds, which affect the dielectric response-ability and the surface hydrophobicity (the apparent contact angle of water can reach 135°). Finally, we demonstrate that the obtained carbon heterostructure maintains its wideband EM absorption with an effective absorption frequency ranging from 12.5 to 16.7 GHz under conditions that simulate the real-world environment, including exposure to rainwater with slightly acidic/alkaline pH values. Overall, the advances reported in this work provide new design principles for the synthesis of high-performance EM absorbers that can find practical applications in real-world environments.

This work aimed to help the bamboo industry develop methodology for producing imperfection-free bamboo boards that can serve either decorative or structural benefit to consumers seeking to engage with the bioeconomy. Specifi- cally, softened and slotted bamboo tubes were handled by a roller device with nails to render crack-free flattened bamboo board. Softening temperature and time were optimized herein according to findings regarding chemical composition and board mechanical properties. The optimal softening parameters for saturated steam heat treatment is proved to be 160°C for 8 minutes. The flattened bamboo board possesses an increased bending strength of 101.5 MPa and a decreased bending modulus of 7.7 GPa, being compared with only-softened bamboo. The corresponding changing mechanism is determined in-depth by the micro- morphological and mechanical results based on in-situ SEM and AFM technologies. Under the action of nails and rolling processes, the bamboo texture becomes compact with crushed and fragmented conduit walls. The resulting cell cavity then becomes stretched and compressed, taking on a morphology which allows for the mechanical penalties associated with flattening to be avoided. According to the micro-mechanical results obtained by AFM, compared with unflatten bamboo, the Young’s modulus of the cell membrane in transverse direction (YT) decreases to 1.00 GPa while the corresponding Young’s modulus in radial direction (YR) increases to 7.29 GPa.

The aim of this study was to investigate the effects of the heat treatment time and initial moisture content of bamboo on the corresponding chemical composition, crystallinity, and mechanical properties after saturated steam heat treatment at 180 °C. The mechanism of saturated steam heat treatment of bamboo was revealed on the micro-level, providing a theoretical basis for the regulation of bamboo properties and the optimization of heat treatment process parameters. XRD patterns of the treated bamboo slices were basically the same. With the increase in the initial moisture content of bamboo, the crystallinity of bamboo increased first and then decreased after treatment. Due to the saturated steam heat treatment, the content of cellulose and lignin in bamboo slices increased while the content of hemicellulose decreased, but the content of cellulose in bamboo with a 40% initial moisture content increased first and then decreased. The shear strength of treated bamboo changed little within 10 min after saturated steam heat treatment, and then decreased rapidly. During the first 20 min with saturated steam heat treatment, the compressive strength, flexural strength, and flexural modulus of elasticity of the treated bamboo increased, and then decreased.