Melting gold at room temperature is a thing now.

[g_axelsson]

Plasma torches cut steel (or melt steel) or many other metals at room temperature.

Excuse me, but that's just a stupid statement. The plasma and the steel being removed is way higher than room temperature. All that electrical power going into the plasma torch ends up as heat.
If you still believe that it cuts at room temperature, put your hand on the other side of the steel and see how bad it burns at room temperature.

Göran

I can melt gold, at a room temperature of 72 degrees F, with a high-temperature plasma arc where the temperatures inside the plasma can range from 5,000K to 20,000K.
What is stupid about that statement?
I did not say the localized plasma arc or the ionization area was at room temperature.
What does the temperature of the room have to do with melting metals?
How is this statement different than if I said I can melt a few atoms of gold with a laser beam at a room temperature of 72 degrees F viewed under a microscope?
What does the temperature of the room have to do with anything here?

Please, explain to me then what you mean by "Plasma torches cut steel (or melt steel) or many other metals at room temperature."

If the plasma arc is at 5000-20000 K then it isn't room temperature. Room temperature is approximately 393K.

The report states that the gold melted while still at room temperature (probably slightly higher than 400K)

If you use a laser beam, a plasma torch or a mapp torch to melt gold it still melts at around 1400 K. It is just different ways to increase the temperature (vibrational energy) in the gold up until the point where it melts.
Increasing the electrical field to get the gold melting at the surface at 400K is a totally different process. Apparently the binding energies at the surface are affected and the gold melts. And the molten gold is at room temperature while molten.

Another example of how the melting point can vary depending on external factors is the phase diagram of water, at 200MPa pressure water melts at -20C while under normal atmosphere pressure it melts at 0C.
http://www1.lsbu.ac.uk/water/water_phase_diagram.html
You could easily measure the temperature and while compressing water will heat it up slightly it is easily cooled down and it is the measured temperature that is entered in the diagrams.

Göran

 

[nickvc]

Having followed this thread I have to say it’s falling into a world of semantics, let’s give this a miss now and get back to discussing recovery and refining :shock: :roll:

 

[butcher]

The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point, the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at a standard pressure such as 1 atmosphere or 100 kPa.

Yes, I can boil or freeze water at room temperature nothing new here.

So we can melt a substance (excite the molecules energy level to break a rigid surface), under other conditions besides temperature.



As the energy in the molecules increases from a rise in temperature, the molecules start moving faster. Soon they have enough energy to break free of their rigid structure and start moving around more easily. The matter becomes a liquid.

Making of a few molecules move faster in a localized area with a laser beam under a microscope at room temperature is no surprise to me.

we can melt metal at room temp under pressure.
https://www.sciencealert.com/scientists-have-just-melted-a-solid-below-its-freezing-point

I cannot see what the excitement is about so they made a few molecules of gold move around or get excited under a microscope.

Actually, I have not been following this discussion very thoroughly, I guess I should read the article you guys are getting all molten over (excited over) before opening my jaw and pressing keys...

 

[butcher]

http://sustainable-nano.com/2018/02/14/melting-temperature-depression/

 

[g_axelsson]

That was two interesting articles, Butcher.

I don't know where you got the impression that they used a laser beam to zap the surface layer. It was a high electric field. The interesting thing in this discovery is that the melting point of gold was lowered about 1000K by applying an electric field, as I understand it no one has done that before so it's a discovery. It might not be revolutionary but an incremental step forward of our understanding of nature. In the end it's hard to see what becomes an important discovery or not. In the beginning the laser was called "A solution looking for a problem" and now it's used all over.

As the energy in the molecules increases from a rise in temperature, the molecules start moving faster. Soon they have enough energy to break free of their rigid structure and start moving around more easily. The matter becomes a liquid.

But in this case the gold atoms doesn't move any faster, they melt at "room temperature".

If this effect is discovered in gold then it ought to exist in other materials too. Maybe partial melting of silicon could create a ultra pure surface free of gallium, that could create a new generation of XRF guns (uses Si-crystals as detectors but gallium is hard to remove).
Micro machining could be another area where a localized melting of material could be a great tool.

Personally, I'm just fascinated by learning more about nature.

Göran