New unscratchable 18k gold that is harder than steel

Swiss metallurgists have created the world's most resilient 18-karat gold.
news.discovery.com...

By fusing a material used in bulletproof vests with gold, scientists have created unscratchable 18-karat gold.

The research was funded by the Swiss watchmaker Hublot.

The new gold will be used for jewelry and watches, although it could have other applications.

Now a research team from the EPFL in Switzerland, with support from Swiss watchmaker Hublot, have created a very hard high-quality gold. And recently, they unveiled the shiny result.

“What is radically new is being able to make something that is both extremely hard and 18-karat gold. The challenge was to stick with that boundary,” said Andreas Mortensen, a metallurgy professor at the EPFL in Switzerland who led the work. Metallurgy lecturer Ludger Weber, postdoc Reza Tavangar and materials engineer Senad Hasanovic collaborated with Mortensen to develop the new gold.

Others have been able to make hard gold in the past but they haven't been able to achieve the level of hardness required to meet the 18-karat standard, separating real gold from impure gold. Hublot filed for a patent on the new gold composite, Mortensen said. He called Hublot an adventurous company when it comes to designing with new materials.

To make the new gold, the EPFL team used boron carbide, a ceramic that’s one of the hardest materials in the world, along with diamonds. This material has numerous applications, including as a component in bulletproof vests.

First the ceramic was heated in an oven to more than 3,600 degrees Fahrenheit, producing a three-dimensional network almost like a scaffold, with just the right amount of pores. That network was then infiltrated with liquid gold, meaning the scientists pushed gold into the pores. Finally, the combination was solidified to form the composite material.

Mortensen said the new gold looks and feels distinctive. It’s harder to the touch than other gold, and has a darker hue. The material is so hard that no coating is needed to make it unscratchable. Although that’s an advantage to watch-wearers looking for durability, there is a trade-off because it’s slightly more fragile than pure gold that’s soft.

I think this could have many more uses than the above described use as jewelry and watches. The durability could give this type of gold several more uses including further use as a electrical conductor where friction or corrosion may be an issue, and may have more possible uses in space exploration.

Sounds kinda retarded to me, since one of the unique qualities that make gold valuable is it´s uniquely high malleability and ductility. If the malleability(softness) is removed, of course the ductility should lower as well. What is left? Might as well use steel and paint it yellow... duh.

reply to post by NeoVain


Gold is used in contact electronics because of its resistance to corrosion. It is, however, very soft and easily worn away. This is why your cartridge-based electronics wear out. Often, it's the gold contacts being worn away.

Materials like this change that prospect, considerably. With this, cartridge media will, likely, secure dominance in the market over optical media.

For jewelry purposes, it means you have gold that can stand up to abrasion. The value of gold in jewelry is what it looks like - not its ductility or malleability. When you can deform your ring by squeezing it with your bare hands - that's not a very good ring. Working with pure gold is more like working with putty than a metal.

Excuse my ignorance but isn't gold mixed with another compound or element just an alloy? and not actually gold anymore?

Originally posted by NeoVain
Sounds kinda retarded to me, since one of the unique qualities that make gold valuable is it´s uniquely high malleability and ductility. If the malleability(softness) is removed, of course the ductility should lower as well. What is left? Might as well use steel and paint it yellow... duh.

edit on 27-12-2011 by NeoVain because: (no reason given)

Why would you say something like that? Using big words to make u feel clever? Fact is, there are suitable applications for this new 18ct gold where 24 ct gold and Steel would be unsuitable. Hate when people rubbish things they nothing about.

Thanks for the post pal, I'm in the industry myself and this was new to me!?!. Chances are it will be pretty expensive in comparison. Well done hublot.

OK it is new, and it promises a lot of new applications.

I see one problem, how to salvage the gold out of the used parts?

Now you can use acid, then you would have to grind it down first to extreme fine powder before the acid step.
Otherwise it will be unreachable in the ceramic matrix.

I must admit I am a bit confused about this.

The first thing I thought of was electrical contacts... another poster pointed out that gold is used as a non-corrosive conductor plating but is easily worn away. Boron, I believe, is an insulator. Carbon (diamonds) is a very poor conductor. So unless the composite has some properties that are counter-intuitive and unspecified, it would appear this alloy would be of little use as a conductor plating.

As for jewelry, which is specifically mentioned, I always thought gold was valued for its purity; this composite would by definition not be pure.

Maybe I'm missing something?

TheRedneck

Originally posted by TheRedneck
I must admit I am a bit confused about this.

The first thing I thought of was electrical contacts... another poster pointed out that gold is used as a non-corrosive conductor plating but is easily worn away. Boron, I believe, is an insulator. Carbon (diamonds) is a very poor conductor. So unless the composite has some properties that are counter-intuitive and unspecified, it would appear this alloy would be of little use as a conductor plating.

As for jewelry, which is specifically mentioned, I always thought gold was valued for its purity; this composite would by definition not be pure.

Maybe I'm missing something?

TheRedneck

Although carbon as graphite is a lousy conductor, diamond is a reasonable p-conductor when there is boron in the matrix, which is the case in natural blue diamonds . Other diamonds are insulators.

Most "golden" jewellery is an alloy of gold and other metals, depending on how may carat and the preferred colour.
Only some very old "grave gifts" were 24 K gold.
24K gold is to soft for everyday use.

reply to post by TheRedneck

en.wikipedia.org...

Boron carbide is known as a robust material having high hardness, high cross section for absorption of neutrons (i.e. good shielding properties against neutrons), stability to ionizing radiation and most chemicals.[3] Its Vickers hardness (38 GPa) and fracture toughness (3.5 MPa·m1/2) approach the corresponding values for diamond (115 GPa and 5.3 MPa·m1/2).

You have a valid point about the conductivity of boron carbide. The quantity involved may or may not effect the conductivity of the gold.

An alternative use, if it is less conductive, may be as a sheild protecting against neutrons, although I'm not sure if the gold content would prohibit this type of use.

reply to post by TheRedneck


The important thing to note in the construction of this material is that it is a lattice of the ceramic material with gold impregnated into it - like a resin fills in around the fibers of a composite material. The gold will still conduct just fine - it just has an insulator creating a mesh framework within it (think like rebar in concrete - only the concrete is conductive and the rebar is not).

Anyway - I've long thought that these types of materials would start to crop up. Traditional alloys are becoming exhausted. Fiber-Resin composites have their applications, but are horribly limited by comparison to the structural characteristics of metals and ceramics. Ceramic-Metal composites are the next logical evolution of structural materials until we get into dynamically engineered compound latices that actually respond to stress with changing chemical bonds (forming new compounds). Which we will likely start seeing prototypes of within the next ten years - computer modeling accuracy providing.

It will not surprise me to see more of these types of materials emerging - particularly in the extreme ends of engineering (jet engines, for example - where the temperatures are more than sufficient to melt the materials used in jet engines without "cool" air injection through the turbine surfaces).

reply to post by Pokoia

I wasn't aware that carbon in the diamond matrix combined with boron was a conductor. Not disputing you, but do you have a link for that info?

As for the weight, 18K vs. 24K... again, I can't dispute you but I would like more information. Pure gold is 24K, correct? And since gold is sold by the ounce (weight measure), would not 24K gold be more valuable than 18K gold? And since jewelry cost is based on the value of the materials in it (precious metals and/or gemstones), would not this 18K hardened gold be less valuable than pure gold?

I am also a little confused about how the gold can be weighed as 18K when it is encased in a matrix of ceramic. Doesn't that by definition decrease the carat weight since a substantial part of the material is no longer gold, but a boron-carbon ceramic?

I understand metallurgy and ceramics technology just fine, but the concept of value is what is confusing me.

TheRedneck

reply to post by isyeye

I don't think the gold would decrease the neutron-absorbing properties of the ceramic, except by taking up space that is gold instead of ceramic. I would expect the gold-ceramic mixture to have similar nuclear properties to the ceramic alone.


reply to post by Aim64C

Oh, don't get me wrong: ceramics are indeed the future of materials science. My confusion about this material is that it is actually decreasing the gold weight by including the ceramic matrix, thereby lessening the value of the gold in it, and apparently has no evident uses outside of hard watches. Now, maybe hardened gold would be desirable enough to make its value significantly more than gold itself... I really don't know about that.

Maybe that's what I am missing... maybe I am thinking of gold strictly in the monetary sense, and that is not applicable to this discussion?

TheRedneck

reply to post by TheRedneck


18 karat gold is 75% gold I think (18/24). The rest is an alloy of some sort. This resin just replaces the alloy. In the end you have the same amount of gold. The resin 18 k is probably harder to extract so resale value would likely be lower. Thus this would not be investable like gold coins, jewlery, etc.

reply to post by TheRedneck

Maybe that's what I am missing... maybe I am thinking of gold strictly in the monetary sense, and that is not applicable to this discussion?

You've pretty well summed it up, here, I think.

Interestingly enough, gold and silver have become very important in recent decades within industry. Silver is the best conductor known (spare for extreme examples of super-conducting materials). Both have become very crucial to the computer industry (a number of companies out there recycle electronics almost exclusively to reclaim the silver and gold used in them - although copper is valuable enough to justify attempts at it, to be honest). Both are essential elements in fuel cells and in other catalytic reactions.

I recall a recent discovery where micronized gold was found to exhibit anti-microbial and anti-pollutant characteristics when exposed to ultraviolet radiation. A key component in stained glass windows is gold dust. While they were likely unaware of it - stained glass windows will actually 'purify' the air and break down many complex molecular structures that encounter the stained glass.

From a purely monetary sense - what they have done is not really all that important.

From an industrial sense - what they have done is allowed someone to wear a gold ring that is as hard as steel. It will be a bit of a niche market in the jewelry arena, to be sure - but this highlights the developing technology, as much as anything.