UV-protection of wood surfaces by controlled morphology fine-tuning of ZnO nanostructures

Abstract

Abstract:One of the most significant limitations for a wider utilisation of the renewable and CO 2 -storing resource wood is its low ultraviolet (UV) light stability. The protection of the wood surface without altering its aesthetic appeal requires an optically transparent but UV protective coating which should be strongly attached to the rough and inhomogeneous substrate. For this purpose, ZnO nanostructures were deposited onto the wood surface via a chemical bath deposition process. The morphology of crystalline ZnO was controlled by aluminium nitrate or ammonium citrate in the growth step resulting in nanorod arrays or platelet structures, respectively. Detailed structural, chemical and mechanical characterisations as well as accelerated weathering exposure revealed the effective performance of the platelet structure, which formed a dense and thin ZnO coating on spruce. The total colour change (ΔE in the CIE system) was calculated to be 20.5 for unmodified wood, while it was about three for the modified samples after 4 weeks accelerated weathering test. Moreover, the ZnO coating also suppressed crack initiation and propagation indicating a substantial increase in durability.

Bio‐Inspired Superhydrophobic and Omniphobic Wood Surfaces

“…The wood surface roughness was covered with ZnO nanorods following the optimized procedure reported in a former publication . First, the seed layer was prepared by dipping the wood slices into an aqueous solution containing 5 m NH 3 and 50 × 10 −3 m ZnO at room temperature for 3 min before heat treatment on a hotplate at 110 °C for 2 min.…”

“…In this work, we further develop a recently reported wood surface coating process to study wettability and generate superhydrophobic as well as omniphobic wood surfaces. The modification steps comprise a solution‐based surface seeding followed by a morphology controllable growth of ZnO crystals.…”

“…), which is structured by concave lumen channels and ridges originating from double cell walls. We applied a versatile aqueous based approach to modify the surfaces, as previously reported for the fabrication of nanostructures on wood surfaces . To coat the rough wood surface (uneven topography with lumina and cell walls) with a conformal and uniform ZnO seed layer (SL), zinc ammine complexes (Zn[(OH) x (NH 3 ) y ] 2− x ( x + y = 4)) were prepared by dissolving ZnO powder in ammonium hydroxide solution (Equation (S1), Supporting Information).…”

Optically Transparent Wood: Recent Progress, Opportunities, and Challenges

“…The main modification strategies include modification of the cell wall, cell wall/lumen interface modification, and lumen filling ( Figure a) . Modification can be performed by chemical reactions of small molecules, physical adsorption, physical filling of monomer liquids, thermal treatment, or complex combinations. Successful wood modification examples include preparation of magnetic wood, fire retardant wood, conductive wood, and stimuli‐responsive wood .…”

Estudios reales en banco de pruebas de la Casa ETH de Recursos Naturales – protección superficial de la madera para aplicaciones exteriores

“…The process was adapted from a procedure we reported previously (19,20) and was carried out in a stainless steel container. The first seeding step required a heat treatment at 80°C.…”