I don't know if I call it advanced myself...this may be a significant
unraveling point however.
Advance in high-pressure physics
Harvard scientists announce they've created metallic hydrogen,
which has been just a theory
January 26, 2017
Nearly a century after it was theorized, Harvard scientists report they
have succeeded in creating the rarest material on the planet, which could
eventually develop into one of its most valuable.
Thomas D. Cabot Professor of the Natural Sciences Isaac Silvera and
postdoctoral fellow Ranga Dias have long sought the material, called
atomic metallic hydrogen. In addition to helping scientists answer some
fundamental questions about the nature of matter, the material is
theorized to have a wide range of applications, including as a room-
temperature superconductor. Their research is described in a paper
published today in Science.
“This is the Holy Grail of high-pressure physics,” Silvera said of the quest
to find the material. “It’s the first-ever sample of metallic hydrogen on
Earth, so when you’re looking at it, you’re looking at something that’s
never existed before.”
In their experiments, Silvera and Dias squeezed a tiny hydrogen sample
at 495 gigapascal (GPa), or more than 71.7 million pounds per square
inch, which is greater than the pressure at the center of the Earth. At
such extreme pressures, Silvera explained, solid molecular hydrogen,
which consists of molecules on the lattice sites of the solid, breaks down,
and the tightly bound molecules dissociate to transforms into atomic
hydrogen, which is a metal.
While the work creates an important window into understanding the
general properties of hydrogen, it also offers tantalizing hints at
potentially revolutionary new materials.“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.”
Understanding whether the material is stable is important, Silvera said,
because predictions suggest metallic hydrogen could act as a
superconductor at room temperatures.
“As much as 15 percent of energy is lost to dissipation during
transmission,” he said, “so if you could make wires from this material and
use them in the electrical grid, it could change that story.”
A room temperature superconductor, Dias said, could change our
transportation system, making magnetic levitation of high-speed trains
possible, as well as making electric cars more efficient and improving the
performance of many electronic devices. The material could also provide
major improvements in energy production and storage. Because
superconductors have zero resistance, superconducting coils could be
used to store excess energy, which could then be used whenever it is
needed.
Metallic hydrogen could also play a key role in helping humans explore
the far reaches of space, as a more powerful rocket propellant.
“It takes a tremendous amount of energy to make metallic hydrogen,”
Silvera explained. “And if you convert it back to molecular hydrogen, all
that energy is released, so that would make it the most powerful rocket
propellant known to man, and could revolutionize rocketry.”
The most powerful fuels in use today are characterized by a “specific
impulse” (a measure, in seconds, of how fast a propellant is fired from
the back of a rocket) of 450 seconds. The specific impulse for metallic
hydrogen, by comparison, is theorized to be 1,700 seconds.
“That would easily allow you to explore the outer planets,” Silvera said.
“We would be able to put rockets into orbit with only one stage, versus
two, and could send up larger payloads, so it could be very important.”
In their experiments, Silvera and Dias turned to one of the hardest
materials on Earth, diamond. But rather than natural diamond, Silvera and
Dias used two small pieces of carefully polished synthetic diamond and
treated them to make them even tougher. Then they mounted them
opposite each other in a device known as a diamond anvil cell.
“Diamonds are polished with diamond powder, and that can gouge out
carbon from the surface,” Silvera said. “When we looked at the diamond
using atomic force microscopy, we found defects, which could cause it to
weaken and break.”
The solution, he said, was to use a reactive ion etching process to shave
a tiny layer — just five microns thick, or about a tenth the thickness of a
human hair — from the diamond’s surface. The diamond was then coated
with a thin layer of alumina to prevent the hydrogen from diffusing into
the crystal structure and embrittling it.
After more than four decades of work on metallic hydrogen, and nearly a
century after it was first theorized, it was thrilling to see the results,
Silvera said.
“It was really exciting,” he said. “Ranga was running the experiment, and
we thought we might get there, but when he called me and said, ‘The
sample is shining,’ I went running down there, and it was metallic
hydrogen.”
“I immediately said we have to make the measurements to confirm it, so
we rearranged the lab … and that’s what we did.”
|
|
I’ve been studying a basic Tutorial Physics course and
have just come across momentum and impulse. Impulse is
the change in momentum. An equation for Impulse is
[force x time]. In the article about metallic
hydrogen the m.h. burns much longer than the most
powerful fuels in use today, so a rocket can have much
more momentum (which is mass x velocity).
In the article about metallic hydrogen:
“It takes a tremendous amount of energy to make
metallic hydrogen,” Silvera explained. “And if you
convert it back to molecular hydrogen, all that energy
is released, so that would make it the most powerful
rocket propellant known to man, and could
revolutionize rocketry.”
The most powerful fuels in use today are characterized
by a “specific impulse” (a measure, in seconds, of how
fast a propellant is fired from the back of a rocket)
of 450 seconds. [7.5 minutes] The specific impulse
for metallic hydrogen, by comparison, is theorized
to be 1,700 seconds. [about 28.3 minutes]
“That would easily allow you to explore the outer
planets,” Silvera said. “We would be able to put
rockets into orbit with only one stage, versus two, and
could send up larger payloads, so it could be very
important.”
-----------------------------
It takes a tremendous amount of pressure to make
metallic hydrogen, so right now it might not be very
practical.
|
|