In the National Ignition Facility (NIF) laboratory, hydrogen samples in small test chambers are under tremendous pressure. The pressure is so great that hydrogen changes its state and becomes a liquid. However, this is only the beginning, and as the pressure gradually becomes larger, the droplets undergo a series of changes.
Hydrogen is the most abundant element in the universe. The main component of gas planets such as Jupiter and Saturn is hydrogen. However, in the interior of the planet, the form of hydrogen is not gaseous, but metal hydrogen. Therefore, changes in small hydrogen droplets can tell us a lot about planets like Jupiter and Saturn. At the same time, solid metal hydrogen will be a magical future material that can be used as a fuel to make spacecraft fly farther; it can also act as a superconductor, allowing current to flow without resistance.
Multiple states of simple matter
Hydrogen has three isotopes: 氕, 氘, 氚, and 99.985% of hydrogen in nature is 氕, which has the simplest atomic structure in the world, surrounded by an electron. In addition, the nucleus of strontium consists of a proton and a neutron, and the content in nature is generally about one-seventh of that of all hydrogen. The nucleus of the sputum consists of a proton and two neutrons. It is radioactive and has very little in nature. In the laboratory, it is also possible to artificially synthesize four other isotopes of hydrogen: hydrogen 4, hydrogen 5, hydrogen 6, and hydrogen 7.
In our natural world, hydrogen is mainly in the form of hydrogen, which is bound by two atoms to form a molecule. However, as pressure and temperature change, the density and arrangement of atoms change, so hydrogen actually has multiple states. When the temperature is lowered to -252.88 ° C under normal pressure, the hydrogen becomes a liquid, and when it is lowered to -259.125 ° C, the hydrogen becomes solid.
However, at high temperatures, as the pressure increases, the hydrogen gas first becomes a clear liquid hydrogen, at which point the molecules can flow freely; then become an opaque liquid hydrogen, where the liquid contains both molecules and atoms; The bond is completely broken and becomes a liquid metal hydrogen composed of atoms. Finally, as the pressure increases, the hydrogen nuclei are aligned neatly, and the electrons can move freely, in this case a solid metal hydrogen state.
Currently, researchers focus on liquid and solid metal hydrogen. In August 2018, researchers at the NIF laboratory in the United States found an accurate method for converting strontium into a metal form at a temperature above 726.85 ° C and 2 million atmospheric pressures. Although the liquid metal hydrogen in the laboratory is very unstable, it allows researchers to understand the properties of some liquid metal hydrogen, such as whether liquid metal hydrogen is a superfluid liquid.
If liquid metal hydrogen is a superfluid liquid, it will play a crucial role for scientists to understand the motion patterns inside the gas planet and the external magnetic field. According to astronomers, there are oceans of liquid metal inside the gas planets such as Jupiter and Saturn. 80% of these giant planets are composed of liquid metal hydrogen, not pure gas. In a superfluid liquid, the flow of particles does not encounter any resistance. Once the liquid begins to move, it can move indefinitely, which is probably the reason why Jupiter has a strong magnetic field.
Looking for solid metal hydrogen
Although the road to manufacturing solid metal hydrogen has a long way to go, once it is successful, it will bring about a major leap in the field of metal hydrogen research.
The study of solid metal hydrogen began in 1935, when American physicists Eugene Wagner and Hilde Huntington predicted that hydrogen could be converted into solid matter with metallic properties under ultra-high pressure, and the atomic structure should be compact. 10 times. At the same time, once the solid matter is produced, its state and metallic properties can be maintained even under normal pressure, just like diamonds. Diamonds are formed by the high pressure and high temperature of carbon inside the earth. When the diamond is mined from the ground, it still maintains a compact atomic structure rather than expanding into graphite.
One of the scientists’ closest success was in 2017, when scientists at Harvard University used diamond-on-anvil (composed of two opposing diamonds and seals, with the sample placed in the center of the diamond and seal) at very low temperatures. The hydrogen sample was applied with an atmospheric pressure of 4.95 million times (the core pressure was about 360 times that of atmospheric pressure). As the pressure increases, hydrogen transforms from a non-conductive, transparent insulator into a black semiconductor that eventually transforms into a shiny, metallic solid. At this time, the force between the hydrogen atoms is converted into a metal bond, and the electrons outside the hydrogen nucleus are free from the bond, and the nucleus shares a group of electrons.
Regrettably, the only metal hydrogen in the world disappeared in just a month or so. After the solid metal hydrogen was formed, it was kept in the diamond anvil. Before the sample was sent to the Argonne National Laboratory in the United States, the researchers wanted to use the laser to finally test the pressure, resulting in diamond fracture, and the solid metal hydrogen sample was like this. Doped in the debris of the diamond, can not be found. Now scientists have been improving and repeating the experiment.
Future technological revolution
Today, many rockets are driven by liquid hydrogen (liquefied at a standard atmospheric pressure of -253 ° C). If we use solid metal hydrogen as a fuel, when it burns, it will first come from the solid state. It is converted to hydrogen. At this time, the energy of the solid metal hydrogen into hydrogen will be released and then burned. Therefore, this super metal can generate more energy than liquid hydrogen fuel. Researchers predict that solid metal hydrogen is 3.7 times more efficient than liquid hydrogen.
Modern rockets often have to sail in space for a long time, so they need a lot of fuel. For this, they need to be equipped with huge fuel tanks, and rockets tend to be large. Once solid metal hydrogen is successfully developed, future rockets can become lighter and more efficient, greatly reducing the difficulty and cost of space navigation.
In addition to being a fuel, another important application of solid metal hydrogen is as a superconductor. Current superconductors must be cooled to -269 °C with liquid nitrogen to maintain very low resistivity, which is both expensive and requires energy. However, according to theoretical predictions, solid metal hydrogen is a superconductor at room temperature with a resistivity of zero. This may pave the way for a technical revolution in which we can store electricity from green energy sources in large superconducting coils composed of solid metal hydrogen. Since the resistivity is completely zero, the current flowing in it does not consume any energy. Can flow all the time.
Although the road to developing solid metal hydrogen and commercial mass production seems to be long, the beginning of each new technology is difficult. With the breakthrough in this field in recent years, I believe we will soon see hydrogen metal blocks at room temperature.