Scandium is the "boron like" element predicted by Mendeleev. Their discovery once again proved the correctness of the periodic law of elements and Mendeleev's foresight.
Scandium metal was produced from electrolytic molten scandium chloride in 1937.
Related figure: Mendeleev (1834-1907) predicted the existence of scandium. Scandium was discovered by L.F. Nelson (1840-1899) and P.T. Cleve (1840-1905).
Extraction and preservation: for a long time after discovery, the use of scandium has not been shown because it is difficult to produce. With the increasing improvement of the separation methods of rare earth elements, the compounds used for the purification of scandium now have quite mature technological processes.
Because the alkalinity of scandium hydroxide is the weakest than that of yttrium and lanthanide elements, the rare earth element mixed ore containing scandium will be precipitated first when it is transferred into solution and treated with ammonia after treatment, so it can be easily separated from the rare earth element by using the "graded precipitation" method. Another method is to separate scandium nitrate by using the "fractional decomposition" of nitrate. Since scandium nitrate is the easiest to decompose, the purpose of separating scandium can be achieved. In addition, the comprehensive recovery of associated scandium from uranium, thorium, tungsten, tin and other minerals is also an important source of scandium.
After obtaining the pure scandium compound, convert it into ScCl3, co-melt it with KCl and LiCl, use the molten zinc as the cathode for electrolysis, so that scandium will precipitate on the zinc electrode, and then evaporate the zinc to obtain scandium metal.
Scandium is a light silvery white metal with very active chemical properties. It can react with hot water to generate hydrogen. So the metal scandium you see in the picture is sealed in a bottle and protected with argon, otherwise scandium will soon form a dark yellow or gray oxide layer, losing its shiny metallic luster.
Isotope: Scandium (atomic mass unit: 44.955912 (6)) is characterized by many isotopes, with a total of 37 isotopes, of which only one isotope (47Sc) is stable in nature.
Application field: lighting industry; Interestingly, the use of scandium (as the main working substance, not for doping) is concentrated in a very bright direction. It is not too much to call it the son of light.
The first magic weapon of scandium is called scandium sodium lamp, which can be used to bring light to thousands of households. This is a metal halide electric light source: fill the bulb with sodium iodide and scandium iodide, and add scandium and sodium foil at the same time. During high voltage discharge, scandium ion and sodium ion emit light of their characteristic emission wavelength respectively. The spectral line of sodium is 589.0 and 589.6 nm, two famous yellow light, while the spectral line of scandium is 361.3~424.7 nm, a series of near-ultraviolet and blue light emission. Because of complementary color, the overall color of light produced is white light. It is precisely because scandium sodium lamp has the characteristics of high luminous efficiency, good light color, power saving, long service life and strong fog breaking ability that it can be widely used for television camera and square, stadium and road lighting, and is called the third generation light source. In China, this kind of lamp is gradually popularized as a new technology, while in some developed countries, this kind of lamp was widely used as early as the early 1980s.
The second magic weapon of scandium is solar photovoltaic cells, which can collect the light scattered on the ground and turn it into electricity to promote human society. Scandium is the best barrier metal in metal-insulator-semiconductor silicon photocells and solar cells.
His third magic weapon is called γ The ray source is a magic weapon that can shine bright by itself, but this kind of light can't be received by the naked eye. It is a high-energy photon flow. We usually extract 45Sc from minerals, which is the only natural isotope of scandium. Each 45Sc nucleus contains 21 protons and 24 neutrons. If we put scandium in a nuclear reactor and let it absorb neutron radiation, as if we put a monkey in the alchemy furnace of Supreme Master for 4749 days, 46Sc with one more neutron in the nucleus would be born. 46Sc, an artificial radioisotope, can be used as γ Ray source or tracer atom can also be used for radiotherapy of malignant tumors. There are also applications such as yttrium gallium scandium garnet laser, scandium fluoride glass infrared optical fiber, and scandium coated cathode ray tube on TV. It seems that scandium is born with light.
Alloy industry: scandium in the form of single substance has been widely used in the doping of aluminum alloys. As long as a few thousandths of scandium is added to the aluminum, a new phase of Al3Sc will be formed, which will modify the aluminum alloy and make obvious changes in the structure and properties of the alloy. Adding 0.2%~0.4% Sc (this proportion is really similar to the proportion of salt in the fried vegetables at home, only a little) can increase the recrystallization temperature of the alloy by 150~200 ℃, and significantly improve the high-temperature strength, structural stability, welding performance and corrosion resistance, and can avoid the embrittlement phenomenon that is easy to occur during long-term work at high temperature. High strength and high toughness aluminum alloy, new high strength and corrosion resistant weldable aluminum alloy, new high temperature aluminum alloy, high strength and neutron irradiation resistant aluminum alloy, etc., have very attractive development prospects in aerospace, aviation, ships, nuclear reactors, light vehicles and high-speed trains.
