Hardened wood could replace plastic and steel

“The hardened wood we demonstrate[…] epitomizes the potential of processing natural wood into high performance structural materials”Teng Li

With hard materials being in great demand for engineering applications, researchers from the University of Maryland have developed a method to process bulk natural wood into a hardened wood that make it a viable and renewable substitute for steel and plastic in many applications.

Of course, wood has been in wide use as a structural material for a long time due to its low cost, high strength and low density, but has increasingly been seen as a viable alternative for petroleum-derived materials such as plastics and other non-sustainable materials, such as concrete and steel.

Although existing hard materials like ceramics and alloys have found many uses, from cutting tools to fixing materials to wear-resistant coating, they tend to be non-renewable and expensive. Their synthesis and manufacture tends to require a great deal of energy and extreme conditions involving ultra-high pressure and high temperatures, bringing safety challenges and the consumption of much energy, as well as a large amount of waste gas.

However, in this new study published in the journal Matter [Chen et al. Matter (2021) DOI: 10.1016/j.matt.2021.09.020], a simple and effective approach to manufacturing a super hard material from bulk natural wood that offers a 23-fold increase in hardness compared to natural wood was demonstrated.

The process involves conducting chemical treatment to partially remove lignin and hemicellulose from natural basswood, followed by rinsing with deionized water before the wood sample is compressed perpendicular to the wood fibers to squash the vessels, pores and pits in the raw wood and to remove all water. This is followed by a hot-press drying procedure to be further densify the sample. The hardened wood is then soaked in mineral oil to increase its water resistance and was shaped into knives and nails by curving and polishing.

A table knife made in this way was found to be almost three times sharper than standard table knives, while a hardened wood nail was shown to be as functional as a steel one with similar performance and without the problems of rusting.

The team had been working on wood and cellulose for a number of years, and is increasingly uncovering the potential of these materials. As lead researcher Teng Li told Materials Today, “The hardened wood we demonstrate[…] epitomizes the potential of processing natural wood into high performance structural materials”.

They now hope to further improve the performance of the processed wood and to extend its limits to produce wood-based materials with even better properties, with efforts also focusing on reducing manufacturing cost and working towards its commercialization.