Science

Metal-infused lumber resists water and mold

Metal-infused lumber resists w...
A treated piece of wood resists absorbing water (left), while an untreated piece readily does so, changing color in the process (right)
A treated piece of wood resists absorbing water (left), while an untreated piece readily does so, changing color in the process (right)
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A treated piece of wood resists absorbing water (left), while an untreated piece readily does so, changing color in the process (right)
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A treated piece of wood resists absorbing water (left), while an untreated piece readily does so, changing color in the process (right)
From left to right: Assoc. Prof. Shannon Yee, grad student Shawn Gregory, and Asst. Prof. Mark Losego
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From left to right: Assoc. Prof. Shannon Yee, grad student Shawn Gregory, and Asst. Prof. Mark Losego

While lumber certainly has many desirable qualities as a building material, it typically has to be pressure-treated with eco-unfriendly chemicals to keep from rotting. With that problem in mind, US scientists are working on a greener alternative – giving the wood a shot of metal oxide.

Led by Asst. Prof. Mark Losego, a team at Georgia Tech is taking advantage of an existing technique known as atomic layer deposition. Although typically used in the manufacturing of electronics, in this case the technology is being utilized to deposit an ultra-thin protective coating of metal oxide throughout the entire cellular structure of pieces of lumber.

The process involves placing the wood in a low-pressure airtight chamber, then introducing a metal oxide gas. The gas molecules proceed to permeate the wood – they travel throughout it, using its interconnected pores as an internal pathway. As those molecules do so, they react with the wood, forming a metal oxide coating on its inner structure.

Although that coating is only a few atoms thick, it's highly effective at keeping the lumber from absorbing water, even when the wood is submerged. As a result, and possibly also due to other effects of the treatment, the lumber is much more resistant to mold growth over time. And as an added bonus, the treated wood is also less thermally-conductive than regular lumber, allowing it to better insulate buildings against heat loss.

From left to right: Assoc. Prof. Shannon Yee, grad student Shawn Gregory, and Asst. Prof. Mark Losego
From left to right: Assoc. Prof. Shannon Yee, grad student Shawn Gregory, and Asst. Prof. Mark Losego

In lab tests, the researchers infused 1-inch (25-mm) lengths of pine 2 x 4's with three types of metal oxide: titanium oxide, aluminum oxide and zinc oxide. It was found that the titanium oxide was the most effective at keeping the wood from absorbing water – an untreated piece of 2 x 4 absorbed three times as much.

Along with its versatility and renewability, one of wood's other selling points as a building material is the fact that once it is discarded, it biodegrades. More research still needs to be conducted concerning how the metal oxide treatment will affect the lumber in that regard, although Losego believes it likely shouldn't be a problem.

"We are actually actively studying biodegradation of these sorts of materials right now," he tells us. "The 'coating' is nominally only an atom or a few atoms thick, so the expectation is that it wouldn’t have that much of an effect on biodegradation, however, I can’t say that with 100-percent certainty."

A paper on the research was recently published in the journal Langmuir.

Source: Georgia Tech via EurekAlert

7 comments
Grunchy
I'm a little dissatisfied with the story, it's too vague. The wood sample treated with titanium oxide only absorbed 1/3 the water as the untreated sample, but over what time period? Was there any change in physical properties like hardness or elastic modulus (perhaps expressed numerically)? Is the wood any more fireproof? Does it create toxic smoke when it does burn? Lastly how long is the time to process, this drastically affects the cost.
Expanded Viewpoint
And don't forget other factors, such as how much energy it takes to process the wood and the cost of the metal oxide. And if there are any drawbacks to the treatment, how do you identify it so people don't think that it's just plain old regular wood and get the two mixed up?
Douglas Rogers
It is not biodegradable in a building but it is, in the ground?
Jery Lake
All good points. Also, as someone who has worked in the construction & lumber business for 30 years it would be good to point out that the worst enemy of wood is UV rays - much worse that water. I would bet the metal oxide would help with this as well but it was not mentioned.
Thud
If the coating doesn't have "much effect" on bio degradation then it surely only has the same effect on resistance to environmental degradation as they are functionally linked.
ljaques
The bonus is that they will be protected from sunburning under UV rays for one day! (Please disregard protection if the lumber is pierced in any way, such as nails, screws, bolts, or cleats.) IOW, this is a nothingburger. (retired handyman confirms Jery Lake's take)
Worzel
How does 1'' translate into 12-15 feet of 3''x 9''? Also, any damage to the timber, like sawing, would expose uncoated fibres, and instantly allow fungal attack. Traditionally, copper oxide has been used to treat plants against fungal attack, and copper is used to protect boat hulls against infestation, so, I'm surprised the team didnt try that as it may be cheaper, and more effective than titanium.