Naked Science Forum

On the Lighter Side => That CAN'T be true! => Topic started by: Bogie_smiles on 30/11/2018 11:47:32

Title: How do you melt gold at room temperature?
Post by: Bogie_smiles on 30/11/2018 11:47:32
https://www.kitco.com/news/2018-11-29/Scientists-Succeed-At-Melting-Gold-At-Room-Temperature.html (https://www.kitco.com/news/2018-11-29/Scientists-Succeed-At-Melting-Gold-At-Room-Temperature.html)
Not available for commercial applications, but still ... https://www.youtube.com/watch?time_continue=17&v=mbKuq1BAfrs

Title: Re: How do you melt gold at room temperature?
Post by: evan_au on 30/11/2018 23:45:20
An electron microscope at high magnification bombards the target with high-energy electrons.
- These electrons have an equivalent temperature, based on the Boltzmann constant of 8x10-5 eV/K.
- Atoms at room temperature (about 300K) have a kinetic energy of 0.025eV.
- An electron in a 100kV electron microscope has a thermal energy equivalent to a temperature of around 4 million degrees (Kelvin or Celcius).
- So they would need to show that it was not thermal heating that caused the gold to melt.

Whatever the cause, this certainly puts a limit on the resolution of fine detail under an electron microscope - it is traditional to coat non-conductive specimens with gold before putting them in an electron microscope.
 
See: https://en.wikipedia.org/wiki/Boltzmann_constant
Title: Re: How do you melt gold at room temperature?
Post by: Bored chemist on 01/12/2018 00:43:01
This seems to be a bunch of folk who don't understand the science they are doing.
They are reporting as "new", something that's well known.
https://onlinelibrary.wiley.com/doi/pdf/10.1002/sca.4950220403
Title: Re: How do you melt gold at room temperature?
Post by: Bogie_smiles on 01/12/2018 02:27:52

The OP article was from 11/29/2018,  “The discovery of how gold atoms can lose their structure in this way is not just spectacular, but also groundbreaking scientifically,” said the study, published in the Physical Review Materials journal (https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.2.085006).


and referenced this journal:
https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.2.085006 (https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.2.085006)

Electric-field-controlled reversible order-disorder switching of a metal tip surface, Ludvig de Knoop, Mikael Juhani Kuisma, Joakim Löfgren, Kristof Lodewijks, Mattias Thuvander, Paul Erhart, Alexandre Dmitriev, and Eva OlssonPhys. Rev. Materials 2, 085006 – Published 22 August 2018


Maybe the explanation for the “old news” getting new attention is as simple as publish or perish, lol.



Title: Re: How do you melt gold at room temperature?
Post by: Petrochemicals on 01/01/2019 08:10:47
This is quite interesting. Gold is crushed and crushed again by pressure, yet does not develop fatigue at any point. Like fluid really, i suppose in a container at enough gravity it would indeed fill the container. Maybe the definition of liquid needs redefining, something like  "at mass smaller than gravitational friction, in zero gravity environment, it will  form a sphere of matter ?

Title: Re: How do you melt gold at room temperature?
Post by: evan_au on 01/01/2019 08:27:23
Quote from: Petrochemicals
at mass smaller than gravitational friction
Please define "the mass of gravitational friction" for gold.

...and how that limit defines a liquid?
Title: Re: How do you melt gold at room temperature?
Post by: Bogie_smiles on 01/01/2019 15:16:41
Quote from: evan_au on 01/01/2019 08:27:23
Quote from: Petrochemicals
at mass smaller than gravitational friction
Please define "the mass of gravitational friction" for gold.
...and how that limit defines a liquid?
Evan, I am thinking that the au in your screen name may not represent gold, though as a moderator, you are as good as gold, lol, and always the Scientist, :) . I have the same question. The concept of gravitational friction is not hard to imagine, but the action of gold or anything else under extreme gravitational force would seemingly be to flatten, and not to flow like a liquid, unless the substance was liquid at the prevailing temperature.

Quote from: Petrochemicals on 01/01/2019 08:10:47
This is quite interesting. Gold is crushed and crushed again by pressure, yet does not develop fatigue at any point. Like fluid really, i suppose in a container at enough gravity it would indeed fill the container. Maybe the definition of liquid needs redefining, something like  "at mass smaller than gravitational friction, in zero gravity environment, it will  form a sphere of matter ?

https://m.youtube.com/watch?v=RcxBfdyF7YY (https://m.youtube.com/watch?v=RcxBfdyF7YY)
Malleability is a term that applies to gold, and the video the malleability of gold is demonstrated. I think gold is the most malleable metal. It is natural for any liquid, in zero gravity, to take a spherical shape, and that would be true of gold above its melting point,

https://en.wikipedia.org/wiki/Gold (https://en.wikipedia.org/wiki/Gold)

 
Phase (https://en.wikipedia.org/wiki/Phase_(matter))at STP (https://en.wikipedia.org/wiki/Standard_conditions_for_temperature_and_pressure)
 		 solid
 
Melting point
 		 1337.33 K (1064.18 °C, 1947.52 °F)
 
Boiling point
 		 3243 K (2970 °C, 5378 °F)
 
Density (https://en.wikipedia.org/wiki/Density)(near r.t.)
 		 19.30 g/cm3
 
when liquid (at m.p.)
 		 17.31 g/cm3
 
Heat of fusion
 		 12.55 kJ/mol
 
Heat of vaporization
 		 342 kJ/mol
 
Molar heat capacity
 		 25.418 J/(mol·K)
 
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   But I take your post to suggest that substances, solid gold included, have a characteristic, which you would label “gravitational friction”. That phrase would define the separation line between whether a substance would be solid or liquid, and would also require a variable that goes with it, i.e., a temperature scale.Then, could we say that the point where any substance would fall on the scale of “gravitational friction” would be at its melting point temperature at a given atmospherical pressure?
Title: Re: How do you melt gold at room temperature?
Post by: Petrochemicals on 01/01/2019 19:58:28
Point taken, enough gravity to flatten gold will probably lead to gravitational friction.

What other metals then are malliable enough to refuse ie. create molecular bonds once more without melting ? Copper I would think would be the next malliable metal, I would think that it would develop fatigue and not recreate bonds ?
Title: Re: How do you melt gold at room temperature?
Post by: evan_au on 01/01/2019 20:26:14
Quote from: Petrochemicals
create molecular bonds once more without melting ?
The definition of a dwarf planet is one which has enough mass to pull itself into a spherical shape.

This even happens for rocky asteroids. However, there may be a degree of melting and differentiation involved, due to heat from the collisions that formed them, or traces of radioactive minerals heating them up from the inside.

Quote from: Bogie_smiles
Evan, I am thinking that the au in your screen name may not represent gold
Correct; it represents a country (au=Australia).