Advance in high-pressure physics | Hacker News Reader

Advance in high-pressure physics

news.harvard.edu

68 pointsnrkfeller10 comments

It hasn't been confirmed yet[0]. Their evidence so far is that they saw something shiny in the diamond anvil. The shiny thing may not necessarily be metallic hydrogen, and could just be the coating.

There are also questions that they reached as high of a pressure as they said they did.

Metallic hydrogen has been created in the lab before. Of course, in these previous cases the metallic hydrogen didn't last long(neither did the test apparatus) as the necessary pressures were reached using explosions.

The first confirmed production of metallic hydrogen used a giant gun to shoot a large bullet at a small container of liquid hydrogen at ~7 kilometers per second.[1] One unconfirmed attempt even used a specially designed bomb to compress liquid hydrogen[2].

[0]http://www.nature.com/news/physicists-doubt-bold-report-of-m... [1]https://en.wikipedia.org/wiki/Metallic_hydrogen#Shock-wave_c... [2]http://web.archive.org/web/20120321111752/http://lateralscie...

Compressing hydrogen with explosions and bullets is actually very old and well-understood science ... if you have the clearance. Explosively compressing hydrogen is how you trigger hydrogen bombs (also via radiation pressure, which probably doesn't create metallic hydrogen). H-bomb research is all about slamming things into liquid H2. I wouldn't be surprised to hear that metallic hydrogen had been briefly produced somewhere in the desert during a bomb-related test.

A few questions I didn't see addressed in the article:

Did they confirm metastability? I guess confirmation of that isn't as easy as simply removing the pressure and seeing if it continues to shine and conduct electricity, or they'd have mentioned it.

As rocket fuel, how do you convert it back to molecular hydrogen to release all that energy? As simple as lighting it on fire in the presence of an oxidizer?

Is it liquid or solid? If liquid, how practical is it going to be in their suggested use in long-distance power transmission? You'd need some kind of flexible packaging that doesn't allow for voids to open up (because then you've lost conductivity) that also won't leak.

And if it's easy to light it on fire as rocket fuel, how can we prevent our long-distance electricity lines from turning into fiery conflagrations in hostile conditions? Could lightning strikes detonate them? Maybe that risk could be reduced with high conductivity coatings on their outer wrap, but that doesn't cover every eventuality.

I met a guy once who was in the business of providing valves for liquid hydrogen handling, he said it was very tricky to handle the stuff safely. Stringing it all over the countryside in a form that packs more than a 3x energy punch of its conventional liquid form could be interesting.

It's solid, altough soft. For rocket fuel you could spray a disintegration catalyst along with the oxidizer.

For rocket fuel, you probably would not want to oxidize it. Low molecular weight in the propellent means higher exhaust velocities. Nuclear rocket engines used H2 propellent.

They didn't confirm metastability. Converting it back to molecular hydrogen is trivial even if it's metastable. If it's not metastable, remove pressure. If it's metastable, one just needs to wait, but the process can be sped up by heating it up. If it's metastable then we'd expect something with properties on the order of dry ice.

We don't know if it's liquid or solid, but there is a pretty good chance it would be solid at room temperature[0].

It would be ridiculous to use metallic hydrogen for power lines, even if it's metastable. If it's not metastable, it's utterly ridiculous, because now we need powerlines that can hold GIGAPASCAL PRESSURES! If it's metastable, some of it will be continuously transitioning to nonmetallic, how fast this happens will depend on how metastable it is, temperature and pressure. So that less of it transitions, we are probably going to want to keep it cold and at high pressure. Our power line is probably going to resemble something like a pipeline. Oil pipelines can run at high pressures(90 bar)[1]

Now if it's metastable, we need to be continuously adding new metallic hydrogen. If our hydrogen is solid, this problem is interesting. There is also the potential for some hydrogen to go non-metallic, increasing resistance, increasing heat causing more hydrogen to go non-metallic, resulting in the entire powerline exploding.

[0]https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/hire... [1]https://insideclimatenews.org/news/20130412/exxons-22-foot-r...

There are some skeptics. "Their main concern is that Silvera and Dias really only have one data point: a single measurement of the reflectivity of their sample at high pressure. While that could indicate metallic hydrogen, it could also be something else, like the alumina coating they used on the diamonds to prevent hydrogen from leaking into the crystal and making it brittle." http://www.forbes.com/sites/samlemonick/2017/01/27/theres-re...

This has been the week for high pressure experiments. Scientists were also able to create a stable helium-sodium compound under high pressures.

http://www.nature.com/nchem/journal/vaop/ncurrent/full/nchem...

http://www.sciencealert.com/forget-what-you-learned-scientis...

Quote: “One prediction that’s very important is metallic hydrogen is predicted to be meta-stable,” Silvera said. “That means if you take the pressure off, it will stay metallic, similar to the way diamonds form from graphite under intense heat and pressure, but remain diamonds when that pressure and heat are removed.”

But the article doesn't say whether the observed result persisted after the pressure was removed.

Previously:

https://news.ycombinator.com/item?id=12875868

Reply on news.ycombinator.com