Lightweight structural materials with high strength are desirable for advanced applications in transportation, construction, automotive, and aerospace. Bamboo is one of the fastest growing plants with a peak growth rate up to 100 cm per day. Here, a simple and effective top‐down approach is designed for processing natural bamboo into a lightweight yet strong bulk structural material with a record high tensile strength of ≈1 GPa and toughness of 9.74 MJ m−3. More specifically, bamboo is densified by the partial removal of its lignin and hemicellulose, followed by hot‐pressing. Long, aligned cellulose nanofibrils with dramatically increased hydrogen bonds and largely reduced structural defects in the densified bamboo structure contribute to its high mechanical tensile strength, flexural strength, and toughness. The low density of lignocellulose in the densified bamboo leads to a specific strength of 777 MPa cm3 g−1, which is significantly greater than other reported bamboo materials and most structural materials (e.g., natural polymers, plastics, steels, and alloys). This work demonstrates a potential large‐scale production of lightweight, strong bulk structural materials from abundant, fast‐growing, and sustainable bamboo.
Natural wood is functionalized
using the index matching poly(methyl
methacrylate) (PMMA) and luminescent γ-Fe2O3@YVO4:Eu3+ nanoparticles to form a novel type
of luminescent and transparent wood composite. First, the delignified
wood template was obtained from natural wood through a lignin removal
process, which can be used as a support for transparent polymer and
phosphor nanoparticles. Then, the functionalization occurs in the
lumen of wood, which benefits from PMMA that fills the cell lumen
and enhances cellulose nanofiber interaction, leading to wood composites
with excellent thermal properties, dimensional stability, and mechanical
properties. More importantly, this wood composite displays a high
optical transmittance in a broad wavelength range between 350 and
800 nm, magnetic responsiveness, and brightly colored photoluminescence
under UV excitation at 254 nm. The unique properties and green nature
of the luminescent wood composite have great potential in applications
including green LED lighting equipment, luminescent magnetic switches,
and anti-counterfeiting facilities.
Turning wood into honeycombs
Wood is an attractive material for structural applications, but it usually works best as boards or sheets. Xiao
et al
. have developed a process for engineering hardwood that allows these sheets to be manipulated into complex structures (see the Perspective by Tajvidi and Gardner). The key is to manipulate the cell wall structure by shrinking and blasting open the fibers and vessels by drying and “water-shocking” them. This process creates a window wherein the wood can be manipulated without ripping or tearing. Honeycomb, corrugated, or other complex structures are locked in once the wood dries. —BG
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