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The diamond has come up with a competitor as tough as he is: an alloy of platinum and gold 100 times harder than steel

Hardness around here. Hardness over there … The meaning of this word from a scientific point of view does not exactly match with the notion we have of hardness in our everyday environment. For this reason, I think that before continuing with the article it is interesting that we briefly review what hardness is from a physicochemical point of view.

In mineralogy, hardness is usually identified as the scratch resistance of a material, and it is measured using the Mohs, Rosiwal or Knoop scales, in addition to others common in the industrial environment. However, there is a slightly more ambitious definition that identifies this property as the opposition presented by a material to suffer a physical alteration, such as not only scratching, but also abrasion, mechanical deformation or penetration.

So far the mineral that in terms of hardness is in a position to look “over the shoulder” at everyone else is diamond. And it is that not only it is the hardest known material, but also the one that offers us the highest thermal conductivity. At the end of the last decade, several studies pointed out that lonsdaleite, a mineral that is formed thanks to the pressure and temperature conditions that occur during the impact of some meteorites containing graphite against the Earth, is even harder. But, given the rarity of this mineral, the diamond, for the moment, remains well established on its throne.

This is the hardest known alloy: platinum and gold.

A group of scientists from Sandia National Laboratory, an institution run by the United States government that specializes in materials engineering, has developed an alloy of platinum and gold which, apparently, has very interesting physicochemical properties. This laboratory is primarily dedicated to testing the non-nuclear components of American atomic weapons, hence its interest in finding new alloys and materials capable of withstanding extremely demanding conditions.

The alloy they have developed contains 90% platinum and 10% gold, and the funny thing is that it is not really new. At least not strictly. It has been known for a long time, but until now scientists had overlooked it and failed to notice its exceptional ability to resist heat and friction. That is what the researchers in this lab have changed, and what has definitely put this alloy on the map.


According to John Curry, who is one of the researchers involved in the study of this material, the property that allows the platinum-gold alloy to look at the diamond from you to you is its excellent mechanical and thermal stability. This characteristic is precisely what places it at the same level as the diamond, adhering to the second definition of hardness that we reviewed at the beginning of the article, and which considers not only resistance to scratching, but also opposition to abrasion, penetration and mechanical deformation.

But this is not all. A very interesting property of this alloy that the engineers of this laboratory have also noticed is its ability to segregate, when subjected to very intense stress, a lubricant that seems to play a very important role in its hardness. And that, in addition, perhaps in the future it can be used to obtain synthetic diamond using a simpler and cheaper process than chemical vapor deposition, which is the method commonly used by industry to make synthetic diamond.

Imágenes | Scott Webb | Randy Montoya | James St. John
Via | New Atlas