Decades ago, people’s commonly used clinical thermometers contained a liquid metal—mercury. Nowadays, as people’s understanding of the hazards of mercury has increased, liquid thermometers using mercury as raw materials have gradually withdrawn from people’s families. However, if you still want to buy a liquid thermometer, you may be able to meet our protagonist today-gallium.
Elements from theory to reality
Gallium is the first chemical element in the history of chemistry that was first predicted by theory and then found and verified in nature.
In 1871, the Russian chemist Mendeleev, who compiled the world’s first periodic table of elements, put forward a prediction based on the law of the element period summarized by him: There is a kind of atomic weight of about 68 in nature and a density of 5.9g/cm 3 , An element with properties similar to aluminum, it should be arranged below the aluminum element in the periodic table.
Mendeleev’s prediction was confirmed by the French chemist Bois Boudran in 1875. While observing the atomic spectrum of zinc extracted from sphalerite ore, he discovered a new purple color band, and he realized that this color band corresponds to a new unknown element. In November 1875, Bouis-Bodran extracted and purified this new metal and proved that its properties were indeed similar to aluminum. This element was named Gallium by Bois-Bodran after the former name “Gaul” of the motherland of France.
The robot killer in “Terminator 2” that can change shape at will
Metal that can be melted in the hand-gallium
Gallium is deeply hidden in nature. Its melting point is only 29.78℃, but its boiling point is as high as 2403℃. Therefore, it “wanders” in various elements in liquid form most of the time, and rarely exists as an independent form. Gallium contains very little content in bauxite, sphalerite, pyrite and other ores. When chemists burn the ore at high temperature, it will volatilize in the form of a compound. It has to be refined by a variety of purification methods to get the purity. The elemental gallium. Without Mendeleev’s prediction, perhaps the true face of gallium could not be revealed so quickly.
In the sci-fi film “Terminator 2”, a robot killer with magical powers appeared. It can transform into any shape at will. It can even go through walls and enter the room to complete the established killing mission. It can automatically heal after being hit by a powerful weapon. , It’s omnipotent, making people helpless. If people can build such a robot in reality, gallium is the most suitable material that scientists can find.
In September 2014, a scientific research team in North Carolina, the United States developed a deformable liquid metal that can repair itself, which is one step closer to the goal of building a deformed robot.
Scientists use gallium and indium to synthesize liquid metal, this alloy can become liquid at room temperature, and its surface tension is very high, in the case of no external force, this alloy can maintain an almost perfect sphere. However, the alloy is very sensitive to electric current. When a small amount of electric current is passed, the surface tension of the alloy will decrease, and the spherical metal will “melt” into a pool of “water” on the desktop. If the electric current is removed, the alloy will slowly gather into a ball. . Changing the voltage level can also adjust the surface tension of the metal and the viscosity of the metal block, thereby changing it into a different structure. In this case, only the electric current needs to be changed, and it is no longer an illusion to make a deformable robot.
This deformed robot can also “eat” and move autonomously. In 2015, the joint research team of the Chinese Academy of Sciences and Tsinghua University developed the world’s first autonomously moving deformable liquid metal robot: when a gallium-based liquid alloy is placed in an electrolyte, it can “ingest” aluminum as food or Fuel provides energy to achieve high-speed, high-efficiency long-term operation. Experiments have shown that a small piece of aluminum can drive a liquid metal ball with a diameter of about 5 mm to achieve continuous movement for more than an hour at a speed of up to 5 cm per second.
Gallium knocks on a new world
Liquid robots seem to be full of sense of technology, but as shown in the movie, it is likely to lose control and cause a burden on humans. Therefore, scientists have no idea of making liquid robots for the time being. However, alloys made of gallium have opened the door to a new world for people.
Chips are one of the most important technological components in modern society. The mobile phones we use every day, the computers we use, the TVs we watch, and the stereos we listen to all contain chips. Without a chip, there would be no light and easy to use in the modern world. Of high-tech products. The emergence of chips is inseparable from semiconductors. Semiconductor refers to a material whose conductivity is between that of a conductor and an insulator at room temperature. With changes in factors such as temperature and electric field direction, the conductivity of the semiconductor will change accordingly. It is precisely because of these characteristics that semiconductors can realize functions such as controllable conduction and communication.
People used the first-generation semiconductors represented by silicon materials to replace bulky electron tubes and produced integrated circuits represented by chips, which promoted the development of the microelectronics industry and the leap of the entire IT industry. However, although silicon has many superior electronic characteristics, after decades of development, these characteristics have been used to the limit, and it is difficult for scientists to use silicon to recreate chips with better performance. They have been looking for semiconductor materials that can replace silicon to make future electronic devices. At this time, compound semiconductors entered the field of view of scientists.
Compound semiconductor refers to a compound formed of two or more elements, which has the properties of a semiconductor. In 1928, scientists synthesized gallium metal and nitrogen gas into a new compound semiconductor material-gallium nitride using a high temperature of more than 2,000 degrees and harsh conditions of nearly 10,000 atmospheres. At that time, they did not expect that after nearly a century of tepid state, today, gallium nitride, a semiconductor material, has given new life.
Compared with silicon-based semiconductors, gallium nitride requires more energy to become a conductor: the energy required to connect electrons in silicon materials to form a conductive band is 1.1 eV, while gallium nitride requires 3.4 eV. This means that GaN has better thermal performance and higher photoelectric conversion efficiency. Under the same power supply, it can achieve more powerful functions than silicon-based chips.
Gallium nitride chips can better meet the needs of today’s high-calorie, low-energy, high-performance electronic products: electronic devices made of gallium nitride chips can work at high temperatures above 200°C; gallium nitride chips are used in power electronic devices In, the system energy consumption is reduced by more than 30%; gallium nitride chip, as the core material of microwave communication base station, can make the base station transmission coverage area more than doubled than the current one.
For China, gallium nitride chips are an excellent weapon to break through the blockade of foreign chip technology, because compared with silicon-based chips that are two or three generations behind, the gallium nitride chip industry is in its infancy worldwide. Gallium chip technology keeps pace with developed countries.
In the future, gallium nitride chips will flourish in the fields of semiconductor lighting, new generation mobile communications, smart grids, high-speed rail transit, new energy vehicles and consumer electronics. Liquid metal gallium will change people’s lives in all aspects.