'Metallic wood' has the strength of titanium and the density of water | Hacker News Reader

'Metallic wood' has the strength of titanium and the density of water

sciencedaily.com

126 pointsLinuxBender51 comments

The problem with metamaterials that have interesting macro-scale properties has always been manufacturing them cost-effectively and in quantity.

It hardly matters if this stuff has a better strength-to-weight ratio than titanium if it also costs 1000 times as much to make an airplane wing out of it.

"Metallic wood" is a very misleading term, too. The material in question is nickel with a cellularized structure resembling wood, rather than a cellulose variant that has undergone some process that bestowed metal-like properties upon it. A more accurate term would have been "xyloid metal" or "ligneous metal".

Plus other factors like the failure modes or how it fatigues in use or how badly it is affected by corrosion or unfortunate thermal constraints. There are plenty of super light and strong but materials that are not suited for use in vehicles or large structures due to a practical limitation of the substance.

Nobody wants to build an airliner wing that is 70% of the weight of a regular wing, but also explodes into a million tiny pieces when it suffers a bird strike.

Nickel tends to be very corrosion resistant. Though these properties are probably diminished by the increased surface area of the porous topology.

I run a small forge. Every alloy I've used will corrode way faster if it's not been finished smooth. I can only imagine how fast a metal (even nickel) foam oxidizes.

Interesting, seems like nanoscale metal foam: https://en.wikipedia.org/wiki/Metal_foam

The fact alone that it's lighter than titanium is a big deal. That's great.

But, too bad that nickel is toxic as hell, and many people are allergic to it. So, I guess it's the biggest trade-off when compared to titanium.

"Some people have an allergic reaction to it" is hardly "toxic as hell".

I think we can put nickel in the "do not eat" category:

https://rais.ornl.gov/tox/profiles/nickel_and_nickel_compoun...

Yes, in that sense it is worse than e.g. iron. One can still imagine applications that don't carry a high risk of ingestion or inhalation.

It's both, toxic and an allergen.

You're right!

Let me see if I can clarify the original point. Nickel is both toxic when ingested and often a contact allergen. Thus the two points are independently true of one another and in no way contradictory.

I hope this has been helpful.

What generally happens to kids that find a US nickel on the ground/floor and swallow it without their parents notice? This must have happened a million of times.

Based on the documentation provided by a sibling comment, I think the answer is that ingestion of the metallic form is not so bad. It's some nickel compounds and inhalation that are particularly dangerous.

Again, the document posted by a sibling (https://rais.ornl.gov/tox/profiles/nickel_and_nickel_compoun...) likely contains all the detail you could wish for.

Also, nickels are about 75% copper.

Not a kid, but I’m allergic to nickel and my daughter threw some quarters in my bed. I didn’t realize it and slept with a quarter burning a hole into my side. I woke up with a quarter-shaped rash that lasted about a week.

This is like the reverse of a super power.

Well, certainly, nickel is toxic, like many metals. But OP's point was "toxic as hell" which seems simply wrong in any kind of context. I haven't seen evidence searching or here that nickel is more toxic than many commonly used metals and thus there seems like zero backing at all for worries about using some super strong nickel-based material. Indeed, nickel-based structural materials are used with some frequency.

Whether the material's good properties pan-out is another question, of course.

It's very toxic if ingested or breathed. Some people have allergic reactions on touch.

I would assume "light and strong" is mostly valuable for frames of cars, building, and airplanes, not the parts people lick or come in contact with all that much.

Ultra-light backpackers will still need to use titanium for their spoons, but if an airplane can cut down on its weight, that's worth a lot.

As an ULBP I don't use metal spoons because they function really poorly in freezing conditions. Bamboo works as well for me...actually I try to eat things that don't need any more tools than my knife.

Titanium spoons for backpackers are just silly.

If you want a metal utensil, aluminum is even lighter than titanium. Titanium is tougher but it's not like your utensil is a load-bearing beam.

Plastic utensils are even lighter than aluminum and don't transmit heat as fast or get as cold in the cold. Wood utensils are good too.

Titanium is mainly just a marketing thing for consumer products. It's not really a broadly useful material in the same way steel is. Expensive, difficult to machine or weld, etc. Advances in steel alloys have reduced the strength/weight advantage to be minimal or nonexistent. It's good for some things though, most notably high temperature applications like gas turbine blades.

Titanium is used for medical implants as it is bio-compatible.

They are luxury, but not silly.

Aluminum disintegrates in acidic food. It has been associated with Alzheimer's disease. It can crack.

Wood can not be cleaned, it splits, and it even has slivers.

Plastic melts or burns. Plastic cracks. Plastic gets discolored, often by foods that contain both oil and tomatoes. BPA has been a problem, and the substitutes in BPA-free plastic are sometimes suspected of being worse.

Anodized aluminum is food-safe and is commonly used in pans, where it experiences much harsher chemical exposure than dipping a spoon into some freeze-dried pasta.

Wood can definitely be cleaned. Wood spoons are a common item in any kitchen where meals are commonly prepared. Bamboo is even tougher and easier to clean.

It's not hard to keep plastic utensils from melting or cracking. I still use the same plastic camp utensils I got decades ago.

I was working in outdoor retail when titanium utensils started being sold. Guess what? People ate just fine before them. When people started buying the titanium utensils, I would sometimes ask why (not challenging, just curious). To a person, they all said: because they're so light. (They were heavier than the plastic spoons.)

I agree that they're a luxury, the same way a $200 Dolce & Gabbana t-shirt is a luxury: high price for no additional benefit. Triumph of marketing.

Cars deteriorate, materials are disassembled and reused, the orderly world in your head is not real and materials need to be safe for a chaotic one

> nickel is toxic as hell, and many people are allergic to it

Unfortunately that doesn't stop companies from making loads of cheap jewelry and eyeglasses out of nickel alloys. And there are lots of applications where a nickel allergy doesn't matter. Golf clubs have rubber grips. Airplanes have walls, carpets and seats between people and the structure.

A quick google search puts the price of nickel at $5.39/lb and titanium at $25.68/lb, so it would be a huge reduction in material costs if they can keep the manufacturing costs relatively similar.

Nickel may indeed be poisonous but given that actual all-nickel coins once circulated, (knows as ... nickles), I'd guess it's not like osmium or something which it can be deadly to be in the same room as.

Nickel isn't listed in Wikipedia's list of metal toxicities.

https://en.wikipedia.org/wiki/Metal_toxicity

US nickels are still 25% nickel.

US nickels have had the same composition (75% copper and 25% nickel) since first being issued in 1866. Hopefully people who feel that using it as a structural metal is a bad idea due to its toxicity are quite wrong and hundreds of millions of Americans are not touching a high toxic metal every day. We once put lead in gasoline, so who knows for sure. Get rid of nickels and the US average IQ goes up a point?

I guess so called because "woody metal" sounds weird?

>"The reason we call it metallic wood is not just its density, which is about that of wood, but its cellular nature," Pikul says. "Cellular materials are porous; if you look at wood grain, that's what you're seeing? -- parts that are thick and dense and made to hold the structure, and parts that are porous and made to support biological functions, like transport to and from cells."

What kind of world do we live in where Sciencedaily.com uses phrases like "titanium, which is as strong as steel but about twice as light"

Twice as light.

Also: "strong as steel" - which measure of strength and which sort of steel?

Fine, it weighs two times less.

It’s half the mass ;)

It's confusing. I can as easily conclude it's either 1/2 or 1/3 of the mass.

Or we could have finally managed negative mass.

I suspect it has to do with connotations.

When you hear "heavy" as used to describe something, you automatically assume it to mean negative. "Half is heavy" has a more negative connotative meaning than "Twice as light", even though they have the same denotative meaning. In other words, they effectively mean the same thing, but represent that thing differently.

I also suspect it has to do with the positive/negative framing. Ideally, you want to leave a positive impression on your audience. If you're talking about scientific discoveries – especially something as cool as a material that's comparable to titanium in terms of strength, yet is much lighter – I reckon you want your audience to feel excited and inspired. In this case, using positive framing is reasonable and conducive to the goal.

I'm not sure how appropriate it is for a popular-science publication to refer to framing when talking about new discoveries, and am not offering support for or against such usage in this context. The decision to put the phrase in such a way, however, may well be an informed choice that makes sense from the perspective of the goal of such a publication.

It would be interesting to know why they choose nickel.

Easy to electroplate with?

Nickel tends to be corrosion resistant. Oxidation is a probabilistic sort of thing. The higher the surface area, the higher chance of corrosive cascades. A metal sponge has significantly higher surface area than the equivalent mass of polished bar stock.

I bet if they did the same thing with iron, a drop of peracetic acid on it would make it go "FOOF!".

Actually that might still work on the nickel.

electro-less nickel plating has been around for years. You dust your object with a catalyst- often palladium and you can coat just about anything with nickel

I wonder if one could 3D-print such structures?

The particulates that process might make would be a problem of its own

"The struts in the researchers' metallic wood are around 10 nanometers wide, or about 100 nickel atoms across. Other approaches involve using 3D-printing-like techniques to make nanoscale scaffoldings with hundred-nanometer precision, but the slow and painstaking process is hard to scale to useful sizes." - TFA

You can 3D print similar structures at a much larger scale. Some of the benefits are retained, like a better overall resistance to weight ratio, some others are not, like increased resistance to localized damage. It's pretty much what different kinds of infill do in 3D prints, which let you control the degree of resistance/deformation of a part in different axes while keeping a low weight.

The article was big on having them self-assemble, which is probably the only practical way to build large quantities of nanoscale materials. Downside of course is controlling for defects.

Lignumified metal? :)

( lignum is wood/timber in Latin )

Lignified*, which is actually a word, “to make woody”

Petrified wood, but metal instead of mineral.

Woodal

What kind of strength? Every aspect? Super. If it doesn’t have the stiffness of titanium it isn’t really as strong.

Edit ok sorry that I confused stiffness with strength. Sorry my lay opinion was factually incorrect

If it turns out to be brittle it can’t be used in the wings. That is my lay opinion on making an aircraft.

Stiffness is usually not considered strength. Strength, whether in compression, tension, or shear, is usually defined as the load it can handle without plastic deformation or fracture. Elastic deformation is by definition reversible once the load is removed.

Titanium actually isn't that stiff, either. It's quite a bit more flexible than steel. New martensitic steel alloys can be close to a match for the best titanium alloys for strength/weight ratio as well.

Since this material is less dense, it should provide better stiffness for weight, since thicker members can be constructed with the same weight. Much like how aluminum bicycles have much larger tubes than steel ones, to make up for the greater elastic flexibility of aluminum.

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