Wedding band suggestions for an Engineering and materials nerd?
August 2, 2011 6:20 AM   Subscribe

Why doesn't anyone make wedding bands made of carbon nanotubes?

My first ring was tungsten carbide, which although very hard, is prone to shattering. As a replacement I'm looking to sacrifice a couple of Mohs on a different material that can take more of a beating.

I need my ring to last forever, with excellent corrosion resistance, hardness and strength. Are there any jewelry manufacturers that take pride in material quality and precision machining? Points for use of exotic metals like titanium carbide, or even hardened steel.
posted by Capa to Clothing, Beauty, & Fashion (17 answers total) 10 users marked this as a favorite
Titanium jewelry isn't actually all that hard to find. A little googling reveals that even companies like Zales carry them, and there are at least a handful of online dealers.
posted by valkyryn at 6:44 AM on August 2, 2011

When you say nanotubes, does that mean you'r eno tinterested in carbon fiber?
posted by aimedwander at 6:50 AM on August 2, 2011

Probably because rings need to be cut off sometimes. You don't want to sacrifice your finger if something happened and it got swollen up. Better to replace a ring, if necessary.
posted by sugarfish at 7:02 AM on August 2, 2011 [2 favorites]

Response by poster: valkyryn: Titanium is at the top of my list currently, but I was hoping to find something a little more exotic

aimedwanderer: While carbon fiber-reinforced resins have a lot of great uses and are very strong in certain applications, I don't feel it's appropriate for a ring that will be constantly dragged across abrasive surfaces
posted by Capa at 7:02 AM on August 2, 2011

Capa, what happened to the tungsten carbide band? I ask 'cos that's what I've got.
posted by Leon at 7:11 AM on August 2, 2011 [1 favorite]

Here's a recent roundup of non-traditional wedding rings from a site run my MeFi's own Ariel Meadow Stallings.
posted by donovan at 7:15 AM on August 2, 2011 [4 favorites]

IAAMS, BIANYMS (I am a materials scientist...)

Here are a few (not-well-organized) thoughts:

Carbon nanotubes would be a spectacularly-poor choice for a ring. Nanotubes are short, and although they can be spun together like a yarn, there are still safety concerns given their small size, and they're likely to hold up as bad (or worse) than carbon fiber from an abrasion point of view.

Most things that are as hard as WC (or harder) are bad choices for the reason sugarfish mentioned above- you probably like having a ring finger.

Additionally, hardness probably isn't what you want so much as toughness; the ability to take a (minor) impact is a good thing. A diamond ring, while possible (in principle) would be a spectacularly poor choice, which you would discover as soon as you accidentally tapped it against something.

Titanium is a reasonable choice because it is tough (and reasonably hard) and possible to machine. Its hardness is a bit of a disadvantage, though, which is why most people choose slightly-less-hard metals and risk an occassional scratch, which can be polished out, anyhow.
posted by JMOZ at 7:21 AM on August 2, 2011 [1 favorite]

FWIW, carbide is hard, but really quite prone to fracture, so a WC ring shatters when the right tool is applied, but who knows if a first responder will interpret the exotic material correctly. Cite
posted by Glomar response at 7:31 AM on August 2, 2011

Best answer: These guys indicate they can fabricate a ring from iridium metal. Nothing's more corrosion resistant, and only one metal (osmium) is stiffer or denser (if density is a plus). Decent hardness. Very expensive.
posted by ftm at 7:37 AM on August 2, 2011 [1 favorite]

Response by poster: Leon: The tungsten band is somewhere in the Atlantic

ftm: Very nice find. I have a feeling Iridium would be prone to fracture similar to tungsten carbide. Perhaps JMOZ can chime in and confirm/deny.
posted by Capa at 7:51 AM on August 2, 2011

Hey! I did a project on carbon nanotubes last spring. They have outstanding tensile strength, but their tensile strength really isn't being called into play in a wedding band. Right now they're very, very hard to manufacture on a mass scale. We can grow them in a lab through a few different methods, but the yield we get just isn't great enough for something like an airplane, space elevator, or a bunch of wedding bands.

Now, someone could get enough to equal the mass of a wedding band, that's not a problem on a one-off scale, but these things are really hard to work with. They really like to stick to each other, so making a pure CNT band would be difficult. You'd want to impregnate them in a binder material, which basically brings you to matrix/fiber materials, and not a pure CNT object.

The other downside of CNT manufacture/handling is fuckin' cancer, man. CNT fibers are tiny tiny tiny tiny. Like, on the order of a few nanometers in diameter. They come like this in either a straight or a curly configuration. The straight ones have the best tensile strength, but they're also more likely to love hanging out in alveoli and causing cancer 20-30 years down the road.
posted by spikeleemajortomdickandharryconnickjrmints at 7:58 AM on August 2, 2011 [3 favorites]

Best answer: Since it sounds like titanium's a good bet for you but you're looking for something more unusual, you might want to check out these titanium mokume gane rings. My husband's has held up well for 4 years so far, and the folded metal process makes it more interesting than most titanium rings.
posted by polymath at 8:09 AM on August 2, 2011

My husband got a lovely textured titanium wedding ring which we got through etsy. They have a HUGE range of jewelers etc on their and you can find rings made in all sorts of materials. They also have the added benefit if they don't have just what you want as they are made by the people that sell them most will gladly do custom orders.
posted by wwax at 8:47 AM on August 2, 2011

Best answer: Stainless steel and concrete.
posted by workerant at 9:31 AM on August 2, 2011

Capa: "ftm: Very nice find. I have a feeling Iridium would be prone to fracture similar to tungsten carbide. Perhaps JMOZ can chime in and confirm/deny."

Iridium is an interesting one... It's an fcc (face-centered-cubic) crystal structure, which USUALLY results in high toughness (i.e. the ability to absorb energy before fracture), but iridium is an exception, and is known for its brittleness. It's undoubtedly less brittle than tungsten carbide (WC), but I'd probably still stay clear of an iridium ring.

For anyone interested, let me define a few terms: (teachable moments, right?)

Fracture: What you think- item is broken

Strength: An ambiguous term. See "yield strength" and "ultimate strength" below

Toughness: The amount of energy that can be absorbed before fracture. Often, materials with a high yield strength have low toughness (i.e. are brittle)

Yield strength (for these purposes- approximately the same as hardness): The amount of force (technically, stress) which a material can take before it deforms in a permanent way. Glass or ceramics (including tungesten carbide) are generally a high yield strength.

Ultimate strength: The amount a material can be stressed before fracture. Most metals aren't as hard (i.e. lower yield strength) than ceramics, but have a higher ultimate strength. (For the scientists among us- the area under the stress-strain curve up to the ultimate strength is the toughness).
posted by JMOZ at 9:51 AM on August 2, 2011 [3 favorites]

I'd also like to again agree with sugarfish and Glomar response and suggest that there are non-trivial risks involved in exotic wedding ring materials- you probably really do want a paramedic to be able to cut your ring off in the event of an emergency. Platinum is a really nice choice, doesn't corrode significantly (under reasonably normal circumstance), and can be polished when scratched. It's also a scientifically-interesting metal, especially in terms of its catalyst properties.
posted by JMOZ at 9:55 AM on August 2, 2011

How about tantalum?
posted by The otter lady at 10:35 AM on August 2, 2011

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