Titanium: A metallic element, gray, can burn in nitrogen, and has a high melting point. Passive titanium and titanium-based alloys are new structural materials, mainly used in the aerospace industry and the marine industry. It took more than a hundred years from the discovery of titanium to the production of pure products. Titanium was truly utilized and recognized after the 1940s. In the ten-kilometer-thick strata on the surface of the earth, the content of titanium is 6/1000, which is 61 times more than copper. If you grab a handful of soil from the ground, it contains a few thousandths of titanium. It is not uncommon to find titanium ore with a reserve of more than 10 million tons. There are hundreds of millions of tons of sand and gravel on the beach. Titanium and zircon, two minerals heavier than sand and gravel, are mixed in the sand and gravel. After millions of years of continuous washing by seawater day and night, the heavier ilmenite and zircon sand ore are washed together, forming a piece of titanium ore layer and zircon ore layer on the long coast. This ore layer is a black sand, usually a few centimeters to tens of centimeters thick. Titanium is not magnetic, so nuclear submarines built with titanium do not have to worry about the attack of magnetic mines. In 1947, people began to smelt titanium in factories. At that time, the output was only 2 tons. In 1955, the output surged to 20,000 tons. In 1972, the annual output reached 200,000 tons. The hardness of titanium is similar to that of steel, and its weight is almost half of the same volume of steel. Although titanium is slightly heavier than aluminum, its hardness is twice that of aluminum. Now, titanium is used in large quantities to replace steel in rockets and missiles. According to statistics, the amount of titanium used for navigation in the world has reached more than 1,000 tons per year. Ultra-fine titanium powder is also a good fuel for rockets, so titanium is known as a metal and a space metal.
Titanium has good heat resistance and a melting point of up to 1725℃. At room temperature, titanium can lie safely in various strong acid and alkali solutions. Even the fierce acid, aqua regia, cannot corrode it. Titanium is not afraid of seawater. Someone once sank a piece of titanium to the bottom of the sea. Five years later, when he took it out, he found that it was covered with many small animals and seabed plants, but it was not rusted at all and was still shiny.
Now, people have begun to use titanium to make submarines - titanium submarines. Because titanium is very strong and can withstand very high pressure, this submarine can sail in the deep sea as deep as 4,500 meters.
Titanium is corrosion-resistant, so it is often used in the chemical industry. In the past, stainless steel was used for the parts containing hot nitric acid in chemical reactors. Stainless steel is also afraid of the strong corrosive agent - hot nitric acid. Every six months, these parts must be replaced. Now, although the cost of using titanium to make these parts is more expensive than stainless steel parts, it can be used continuously for five years, which is much more cost-effective.
In electrochemistry, titanium is a one-way valve metal with a very negative potential, and it is usually impossible to use titanium as an anode for decomposition.
The biggest disadvantage of titanium is that it is difficult to refine. This is mainly because titanium has a strong ability to combine at high temperatures and can combine with oxygen, carbon, nitrogen and many other elements. Therefore, whether in smelting or casting, people are careful to prevent these elements from "attacking" titanium. When smelting titanium, of course, air and water are strictly prohibited from approaching, and even the alumina crucible commonly used in metallurgy is prohibited from use, because titanium will take oxygen from alumina. Now, people use magnesium and titanium tetrachloride to react in an inert gas - helium or argon to extract titanium. People use the characteristics of titanium's strong chemical ability at high temperatures. When making steel, nitrogen is easily dissolved in molten steel. When the ingot cools, bubbles are formed in the ingot, affecting the quality of the steel. Therefore, steel workers add metal titanium to the molten steel to make it combine with nitrogen to become slag - titanium nitride, floating on the surface of the molten steel, so that the ingot is relatively pure.
When a supersonic aircraft flies, the temperature of its wings can reach 500℃. If a relatively heat-resistant aluminum alloy is used to make wings, it will not be able to withstand one to two or three hundred degrees. There must be a light, tough, and high-temperature resistant material to replace the aluminum alloy, and titanium can just meet these requirements. Titanium can also withstand the test of more than 100 degrees below zero. At this low temperature, titanium still has good toughness and does not become brittle. Using the strong absorption of titanium and zirconium on air, air can be removed to create a vacuum. For example, a vacuum pump made of titanium can be used to extract air to only one ten-millionth of the total.
Titanium oxide, titanium dioxide, is a snow-white powder and is the best white pigment, commonly known as titanium dioxide. In the past, people mined titanium ore mainly for the purpose of obtaining titanium dioxide. Titanium dioxide has strong adhesion, is not easy to undergo chemical changes, and is always snow-white. Titanium dioxide is particularly valuable. It has a high melting point and is used to make refractory glass, glaze, enamel, clay, high-temperature resistant experimental utensils, etc.
