Metal hydrogen is an electrical conductor formed by liquid or solid hydrogen under high pressure of millions of atmospheres.The conductivity is similar to that of metal, so it is called metal hydrogen.Metal hydrogen is a kind of high-density and high energy storage material. Previous predictions showed that metal hydrogen is a room temperature superconductor.
Metal hydrogen stores huge energy, 30-40 times larger than ordinary TNT explosives.On January 26, 2017, Science magazine reported that the Harvard University laboratory successfully produced metal hydrogen[1]。On February 22, 2017, the only metal hydrogen sample on the earth disappeared due to operational errors.
Hydrogen is the most familiar chemical element.It is a gas at normal temperature, can become a liquid at low temperature, and is a solid when the temperature drops to minus 259 ℃.If a high pressure of several million atmospheres is applied to solid hydrogen, it may become metallic hydrogen.The emergence of metallic hydrogen is a miracle created by contemporary ultra-high pressure technology, which is a very active topic in the field of high-pressure physics research.
In the metal state of hydrogen, the hydrogen molecule will split into a single hydrogen atom and enable electrons to move freely.In metallic hydrogen, the chemical bond of hydrogen breaks, and the bound electrons in the molecule are squeezed into public electrons. The free movement of these electrons makes metallic hydrogen conductive.Therefore, the key to making hydrogen into metal is to liberate electrons from the bondage of atomscovalent bondChange toMetal bond。[2]
Development history
Announce
edit
In 1935, British physicist Bernard predicted that under a certain high pressure, any insulator can become a conductive metal, but the pressure required for different materials to transform into conductive metal is different. Some materials, such as phosphorus, have been able to obtain a conductor, but stable metal hydrogen samples have never been obtained.In several laboratories in the Soviet Union, Japan and the United States, metallic hydrogen was obtained only under the ultra-high pressure of millions of atmospheres. However, once the normal pressure was restored, the hydrogen returned to its original state.It is judged that metal hydrogen is obtained based on the fact that its resistance changes from 10eightOhm becomes 10twoOhms (Soviet data), or from (1.26 × 10twelve）Ohms drop to 10twoOhms (Japanese data).
Since the 1940s, the United States, Britain and other countries have invested a lot of manpower and material resources to develop metal hydrogen.There are more than 100 high-voltage laboratories in the world.China has successfully developed a press capable of producing 1 million atmospheres.China has successfully developed the "separation sphere type multi-stage multi piston combination device", which can produce 2 million atmospheres of air pressure.China and several other countries have announced that they have successfully developed metallic hydrogen in the laboratory, which is a welcome step towards metallic hydrogen.However, it is still quite difficult to put metal hydrogen into industrial production on a large scale.But it has effectively promoted and promoted the development of more than 20 science and technology, such as ultra-high pressure technology, ultra-low temperature technology, superconducting technology, space technology, laser, atomic energy, to a new depth.It can be predicted that the era of large-scale production of metal hydrogen is not far off.
Scientists at the University of Edinburgh, UK, use diamond anvil to create a certain extreme high pressure state, thus generating“Hydrogen in the fifth state”Is the solid metal state of hydrogen.This is a new form of matter. Hydrogen in this state usually exists in large planets or the solar core. Molecules are separated into single atoms, and the behavior of electrons is like metal electrons.
As early as 80 years ago, this state of hydrogen was first proposed in theory.Since more than 40 years ago, scientists have been trying to reconstruct hydrogen in this state, but they have failed.This time, scientists from the University of Edinburgh, UK, used diamond anvil to compress hydrogen to an unprecedented high pressure, thus confirming the existence of this rare "metallic hydrogen"."Metallic hydrogen" is unstable, and scientists have never seen "metallic hydrogen" before.
The core of the sun and the large planets of the solar system is mainly composed of elements in this high-pressure form.For example, the cores of Jupiter and Saturn are believed to be mainly composed of elements in this form.Professor Eugene Gregorianz, the main person in charge of the research and a scientist at the School of Physics and Astronomy of the University of Edinburgh, said, "In the past 30 years, in numerous high-pressure experiments, scientists have claimed to produce metallic hydrogen, but these experimental results were later proved invalid.Our research provides the first experimental evidence to prove that hydrogen can have a solid metal state as predicted, but the pressure required is much higher than previously thought.The research results will contribute to the development of basic science and planetary science. "
The research team of the University of Edinburgh in the UK used diamond anvil - a device that can allow a very small amount of material to be compressed to extreme pressure - to compress hydrogen, that is, the pressure state necessary to generate the "fifth state hydrogen", and compress hydrogen into a new solid state.In order to reach the "fifth state", the pressure achieved by the research team is equivalent to 3.25 million Earth atmospheres.The scientists observed the change of this state with laser micro Raman spectrometer, thus proving this unusual characteristic of hydrogen through experiments.
Under this extremely high pressure, the molecules begin to separate into single atoms.Researchers found that the behavior of electrons is similar to that of metal electrons.Although this experiment is a big step forward than previous experiments, scientists admit that they still need to continue their efforts to prove it.In addition, more pressure may be required to generate pure atomic and metal states.
On January 26, 2017, Science magazine reported that the Harvard University laboratory successfully produced metal hydrogen[1]。
Preparation
Announce
edit
Theoretically, it is possible to obtain metallic hydrogen under ultra-high pressure.However, to obtain metal hydrogen samples, scientists need to further study.Although metallic hydrogen has not yet been obtained, theorists infer that metallic hydrogen is a high-temperature superconductor, a high-density, high energy storage material.
Most of the available superconducting materials need to be cooled by liquid helium (- 269 ℃) or liquid nitrogen (- 196 ℃), which limits the development of superconducting technology.Metallic hydrogenicSuperconductor critical temperature (i.e. the main maximum temperature reflecting superconductivity) is - 223 ℃~- 73 ℃, which may be able tocarbon dioxide(- 78.45 ℃), which will greatly promote the development of superconducting technology.
As metal hydrogen is a high-density material, the volume and weight of the rocket will be greatly reduced if it is used as fuel, which will lead to a huge leap in the aerospace industry.
Unlike chemists, astronomers refer to all elements other than hydrogen and helium as metals.Under high temperature and high pressure, gaseous hydrogen can also become metallic hydrogen of electrical conductor.Take Jupiter as an example: the outermost layer is 1000 km thick gaseous molecular hydrogen, then 24000 km thick liquid molecular hydrogen, and then 45000 km thick liquid metal hydrogen.
In 1936, American scientist Weiner made the first calculation on the pressure of hydrogen to metal, and proposed that the critical pressure of hydrogen to metal is within the range of 1 million to 10 million atmospheres.In the world, various ways are being used to produce ultra-high pressure metal hydrogen.There are two mature methods. One is called dynamic compression method, which is to use rapid shock compression from a strong magnetic field to obtain high pressure to produce metal hydrogen.The other is called static compression method, which uses a press weighing more than 1000 tons or a hydraulic press with a height of nearly 10 floors to generate a high pressure of 1 million to 2 million atmospheres and compress liquid hydrogen to produce metal hydrogen.
Reason for development
Announce
edit
Why do people work so hard to develop metal hydrogen?This is because once metallic hydrogen comes out, just like the birth of the steam engine, it will lead to an epoch-making revolution in the whole field of science and technology.
Metal hydrogen is a metastable substance, which can be used to make a "magnetic cage" to restrain plasma and "pack" the hot ionized gas. In this way, the controlled nuclear fusion reaction converts atomic nuclear energy into electrical energy, which will be cheap and clean, and it will be convenient to build "factories imitating the sun" on the earth,Mankind will finally solve the energy problem.
The use of metal hydrogen for power transmission can eliminate large substations, and the transmission efficiency is more than 99%, which can increase the power generation of the world by more than a quarter.If the generator is made of metal hydrogen, its weight is less than 10% of the weight of ordinary generators, and the output power can be increased dozens or hundreds of times.
Metal hydrogen also has significant military value.The rocket uses liquid hydrogen as fuel, so it must be made into a large container like a hot water bottle to ensure low temperature.If metal hydrogen is used, the rocket can be made dexterously and small.The application of metallic hydrogen in aviation technology can greatly increase the speed per hour, even many times higher than the speed of sound.Since the volume of metal hydrogen with the same mass is only 1/7 of liquid hydrogen, the fuel cell composed of it can be easily used in automobiles. At that time, cities would not be as noisy and polluted as they are now, and would become very clean and quiet.
Metal hydrogen stores huge energy, 30-40 times larger than ordinary TNT explosives.With the birth of metal hydrogen, many new weapons will be produced.
Related differences
Announce
edit
In most common compounds, such as those in the visible ocean and soil around us, the compound molecules are composed of atoms, which are closely held together because they share electrons.Each electron here is tightly bound to one atom or another.When this happens, the substance shows non-metallic properties.
According to this criterion, hydrogen is a nonmetal.An ordinary hydrogen molecule is composed of two hydrogen atoms.Each hydrogen atom has only one electron, and the two hydrogen atoms that make up a molecule share those two electrons on average.There are no electrons left.
What happens when some electrons are not firmly bound?For example, let's take a look at the element potassium.Each potassium atom has 19 electrons, which are arranged in four shells, and only the electrons in the outermost shell can be shared.In the case of potassium, this means that it has only one electron that can be shared by adjacent atoms.Moreover, the outermost electron is controlled very loosely because there are other electron shells between it and the central nucleus that attract it. These intermediate shells separate the outermost electron from the central gravity.
In solid potassium, atoms are tightly bound together, as we sometimes see in a fruit shop that apples are pyramidal.Each potassium atom has eight adjacent atoms.Since the outermost electron is controlled loosely and many adjacent atoms are so close, any outermost electron is easy to slide from one adjacent atom to another.
However, it is these loose and active electrons that make it possible for potassium atoms to be so tightly bound together;Make potassium easy to conduct heat and electricity;That is, the potassium may be deformed.In short, these loose and active electrons make potassium (and other elements and mixtures containing these elements) metallic.
Remember that hydrogen, like potassium, has only one electron that can be shared by neighboring atoms.However, there is another difference.There is no isolated electron between one (only one) electron of hydrogen and the central nucleus.Therefore, the electron is too tightly controlled to move enough to convert hydrogen into metal or force the hydrogen atoms tightly together.
Event discussion
Announce
edit
On January 26, 2017, Isaac Sivila's team wrote an article in Science magazine that they cooled the hydrogen sample to a temperature slightly higher than absolute zero, compressed the solid hydrogen with diamond under extremely high pressure higher than the center of the earth, and successfully obtained a small piece of gold hydrogen, which was stored between two tiny diamonds.
Isaac said in the news bulletin issued by Harvard University: "The preparation of metallic hydrogen is the holy grail of high-pressure physics, which is the first metallic hydrogen sample on the earth."
On February 22, 2017, when Isaac Sivila's team tried to measure the pressure with a low-power laser, they heard a faint "click", indicating that one of the diamonds had broken into dust.This catastrophic failure made the sample disappear.They believe that metal hydrogen may disappear in the metal "liner" between two diamonds, which is used to hold metal hydrogen;It may also become a gas under normal temperature and pressure due to instability.But some scientists say that metallic hydrogen may not have been developed at all.
Isaac said that through microscope observation, hydrogen samples are shiny and will reflect light in the way that metal hydrogen should, which means they have prepared metal hydrogen.But some scientists believe that it is far from clear whether the shiny metal they observed is hydrogen;Others pointed out that this shiny metal may be aluminum oxide, because the diamond is coated with a layer of aluminum oxide, and aluminum oxide may behave differently under high pressure.In order to convince everyone, Isaac had to repeat the experiment in the same way.[3]
