Make alloy
Cobalt is mainly used to make alloys. Cobalt-based alloys are the general names of alloys made of cobalt and one or more of chromium, tungsten, iron and nickel. Tool steel containing a certain amount of cobalt can significantly improve the wear resistance and cutting performance of steel. Stellite containing more than 50% cobalt will not lose its original hardness even if it is heated to 1000℃. Nowadays, this kind of cemented carbide has become the most important material used between gold-bearing tools and aluminum. In this material, cobalt combines with other metal carbide grains in the alloy composition, which makes the alloy have higher toughness and reduces the sensitivity to impact. This alloy is welded on the surface of parts, which can improve the service life of parts by 3 ~ 7 times. The most widely used alloy in aerospace technology is nickel-based alloy, and cobalt-based alloy can also be used, but the "strength mechanism" of the two alloys is different. The high strength of nickel-based alloys containing titanium and aluminum is due to the formation of phase strengthening agent with NiAl(Ti). When the operating temperature is high, the phase enhancer particles become solid solution, and the alloy soon loses strength. The heat resistance of cobalt-based alloys is due to the formation of refractory carbides, which are not easy to be converted into solid solutions and have low diffusion activity. When the temperature is above 1038℃, the advantages of cobalt-based alloys are fully demonstrated. This is just right for manufacturing high-efficiency high-temperature engines, and so is the cobalt-based alloy. Using cobalt-based alloy containing 20% ~ 27% chromium in the structural material of aviation turbine can make the material achieve high oxidation resistance without protective coating. The turbine generator with mercury as heat medium supplied by nuclear reactor can run continuously for more than one year without maintenance. It is reported that the boilers of generators used in the United States are made of cobalt alloy. Cobalt is one of the few metals that can remain magnetic after being magnetized. Under the action of heat, the temperature at which magnetism is lost is called Curie point. The Curie point of iron is 769℃, nickel is 358℃, and cobalt can reach 1 150℃. The coercivity of magnetic steel containing 60% cobalt is 2.5 times higher than that of general magnetic steel. Under vibration, general magnetic steel loses almost 1/3 of its magnetism, while cobalt steel only loses 2% ~ 3.5% of its magnetism. Therefore, the advantages of cobalt in magnetic materials are obvious. Cobalt is also widely used in electroplating, glass, dyeing, medicine and medical treatment. Lithium cobaltate made of lithium carbonate and cobalt oxide is the most widely used cathode material for modern high-energy batteries. Cobalt may also be used to make nuclear weapons, a theoretical atomic bomb or hydrogen bomb, which is packed in a cobalt shell and can turn cobalt into deadly radioactive dust after explosion.
Preparation of pigment
Cobalt is not only an important metal for making alloy steel, but also an important raw material for various high-grade pigments. According to the documents preserved in17th century, Russia spent a lot of money to buy expensive cobalt pigment, which is called "Golubets", which means "blue". The blue paint on the walls of many magnificent buildings, such as the Kremlin hall and the sleeping cathedral, is this kind of Golubets.
In the Middle Ages, glass craftsmen in Venice made all kinds of exquisite blue glass with cobalt pigments, which quickly became popular all over the world. Venetian artisans kept the manufacturing technology of glasses and the formula of cobalt pigment secret, so as to maintain their undisputed competitiveness in the market. In order to prevent the leakage of technical information, the Venice government moved all the glass factories to an island, and no one was allowed to visit this place without permission. However, an apprentice named Giorgio Bellerino Bellerino escaped from the island because he didn't want to endure the boring life on the island, and later fled to Germany, where he opened his own glass factory, but he didn't escape the disaster. One day, someone set fire to his factory and "bled" the factory owner who fled the island, almost losing his life. It can be seen that Venetians attach importance to the secret of cobalt pigment.
More than 500 years ago, cloisonne mass-produced in China was also fired with blue cobalt pigment. This kind of metal art made in Jingtai period of Ming Dynasty is still famous all over the world. It is said that many foreign intelligence personnel have tried their best to get the formula and firing process of cloisonne.
Some cobalt compounds have unpredictable colors at different states and temperatures. According to records, paracel Sass, a famous chemist and doctor in16th century, often performed his famous tricks and won warm applause from the audience every time. He first showed the audience an oil painting with winter scenery of trees and snow-covered hills. After they had enjoyed enough, he "changed" the winter in the oil painting into the summer in full view: the snow on the tree disappeared and became clusters of green leaves; The snow-covered hills turned into slopes covered with green grass. The audience all admired it, but they didn't know the secret. In fact, this is a magic trick made by paracel Sass with cobalt compound cobalt chloride. It turns out that at room temperature, cobalt chloride can be made into a white solution (the solution contains a certain amount of nickel and iron), and paracel Sass painted with this solution. When the painting is dry and heated slightly, cobalt chloride will turn very beautiful green. When paracel Sass was performing, he first painted his magic painting with cobalt chloride solution, and then quickly put a candle behind the painting and heated it while the audience was enjoying the picture without paying attention to him. As a result, cobalt chloride turned green after heating, which made people stunned by the seasonal changes. Cobalt is a component of vitamin B 12. Ruminants can synthesize cobalt into vitamin B 12 in the intestine, but humans and monogastric animals can't synthesize cobalt into B 12 in vivo. Other functions of cobalt cannot be determined, but only about 10% of cobalt in the body exists in the form of vitamins. It is observed that inorganic cobalt plays an important role in stimulating erythropoiesis. There is an anemia that cannot be treated with folic acid, iron and B 12. Some people can treat this anemia with large doses of cobalt dichloride. However, repeated use of such a large dose of cobalt can lead to poisoning. The mechanism of cobalt affecting erythropoiesis is to affect the release of erythropoietin from kidney or stimulate guanidine circulation. It is also observed that cobalt can dilate blood vessels and make the face red, which is caused by the release of carnosine from the kidney. Cobalt may affect the function of thyroid. The results of animal experiments show that the synthesis of thyroxine may need cobalt, which can antagonize the influence of iodine deficiency.
Cobalt can stimulate the hematopoietic system of human bone marrow, promote the synthesis of hemoglobin and increase the number of red blood cells. Most of them participate in physiological functions in vivo in the form of vitamin B 12. The mechanism of cobalt stimulating hematopoiesis is as follows: ① Stimulating hematopoiesis by producing erythropoietin. Cobalt can inhibit intracellular respiratory enzymes, make tissues and cells anoxic, stimulate the production of erythropoietin through feedback, and then promote bone marrow hematopoiesis. ② Effect on iron metabolism. Cobalt can promote the absorption of iron by intestinal mucosa and accelerate the storage of iron to bone marrow. ③ Vitamin B 12 participates in the metabolism of RNA and hematopoietic substances, and acts on the hematopoietic process. ④ Cobalt can promote the release of red blood cells from spleen (increased hemoglobin content, active proliferation of reticular cells and red blood cells, and increased peripheral red blood cells), thus promoting hematopoietic function.