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Sergey Venezky
STORIES ON METALS

TANTALUM:

BORN IN PAIN

Sins and torments of Tantalus. - The similarity is misleading. - Clarity made. - Hand-in-hand. - 101-year life. - Presentiments had not deceived. - Desired feature. - A match head. - The interest is growing. - Weakness of Aqua Regia. - Repair skulls? - Tantalum nerves. - Humane mission. - Solid customer. - Monstrous temperature not terrible. - Ability to work under pressure. - Down with gases! - Solidarity with the Tantalum. - Enviable constancy. - In the hands of the goldsmiths. - Costs recovered.

The mythological son of Zeus Phrygian king Tantalum, reputed to be the darling of the gods, a great honour: he was admitted to their meetings and gatherings, usually held on the Holy mountain of Olympus. But Tantalum started to abuse such a high confidence. First, he shared some secret decisions adopted by the Olympians. Then in the midst of divine dinner was abducted from the table nectar and ambrosia. Reluctantly the gods had pretended not to have noticed these sins. But once Tantalum has shown unprecedented cruelty and besides the obvious irreverence towards the gods: inviting them to the feast, filed a meat dish prepared from the body of the murdered them on the eve of his own son Pelops. This enraged the Lord of heaven could not forgive and decided to condemn Tantalum to eternal torments of thirst, hunger and fear.

Since then he is in hell on the throat in the clear water. Under the weight of ripe fruit lean branches of the trees. When thirsty Tantalus opens mouth to drink, the water goes away from his lips. He should reach out to the juicy fruits, the wind picks up a branch, and exhausted from hunger, the sinner is unable to get her. Above his head hung a rock, threatening just about to collapse.

So the myths of ancient Greece tell us about "the torment of Tantalus".

Tantalising is an attempt to dissolve a new mineralMust have not once had a Swedish chemist Andres Gustav Ekeberg remember the agony of this mythological sufferer, when he unsuccessfully tried to dissolve in acid open them in 1802 in one of the Scandinavian Minerals new "earth". Many times, it seemed that the scientist was close to the goal, but separate from "the earth" new metal he failed. In the end he was forced to abandon this idea, but, apparently, in memory of their suffering decided to call beginner "tantalum".

Some time later it was discovered that tantalum has a twin, which, however, was born a year earlier, but hardly differed from him on properties. This twin was Columbia opened in 1801 by Englishman Charles Hatchett. Their striking resemblance misled many chemists. After much debate, they came to the erroneous conclusion that we are talking about one and the same element is tantalum.

Wrong scientist was destined for more than forty years. Until 1844 the German chemist Heinrich rose managed to clarify this confusing question and to prove that Columbia as tantalum, has a full right to apply for individual a place in the Sun. And only because there were family connections of these elements. Rose gave Colombia a new name - niobium, which emphasized their nepotism (mythological goddess Niobe was the daughter of Tantalus).

Since tantalum and niobium walking hand in hand through life's journey. And this was a thorny...

For many decades the industrial world has not been shown to tantalum any interest. Yes, strictly speaking, tantalum, as such, simply didn't exist: because pure compact form tantalum managed to get only after he celebrated the centenary of his birth. This happened at the beginning of our century in 1903. And at the same time, i.e. on the 101-year life, he finally got a job: knowing that this metal has a very refractory nature, the scientists decided to use it for the filaments of light bulbs. With no other offers, tantalum was forced to consent, although he felt that it was not his calling.

Tungsten was replaced by tantalum in light bulbsAnd, indeed, the harsh laws of competition that prevails in the world of metals, soon deprived of tantalum. On this warm place was taken by another metal is tungsten, which turned out to be more refractory.

Again reached the years of enforced idleness. "Labor exchange" were quoted only those metals that have either been long known, or had time to present their excellent performance, certified by physicists, chemists and other scientists. Tantalum at that time had few acquaintances in the world of science and technology and was forced to sit idly by. But luck still came in 1922, it has been successfully applied to the rectifiers, and a year later - in radio tubes. Then began the development of industrial methods of production of this metal.

Interestingly, the first industrial stebic tantalum (semi-finished product subjected to further processing), which was obtained in 1922, did not exceed the size of a match head. Recently on tantalum plants are born rods sometimes a thousand times larger than the firstborn.

Tantalum is a rare metal in the earth's crust, accounting for only 0.0002%. However, minerals containing this element, in the nature there are more than 130 (typically, a tantalum them inseparable from niobium). Before the second world war production tantalo-niobium ore was small, but by the end of the war, it increased several times. Increased interest in tantalum is simple: by this time science has discovered many of its valuable properties, which could not remain indifferent representatives of various fields of technology and other spheres of human activity.

What is tantalum? It is a hard light-gray metal with a slightly bluish tint. In refractoriness (melting point of about 3000°C), it is second only to the tungsten and rhenium. High strength and hardness combined with excellent plastic characteristics. Pure tantalum easily workable, easily stamped, rolled into a thin sheet (thickness in hundredths of a millimeter) and wire. But, undoubtedly, the most important property of tantalum is exceptional chemical resistance - in this respect, it is second only to the noble metals, and even then not in all cases. Tantalum is not dissolved even in such terrible chemical aggressors, as Aqua Regia and concentrated nitric acid. At 200°C in 70%nitric acid tantalum does not corrode; in sulfuric acid at 150°C corrosion also not observed, and at 200°C, the metal will corrode only 0,006 mm per year. This makes the tantalum valuable structural material for the chemical industry.

Tantalum equipment used in the manufacture of many acids (hydrochloric, sulfuric, nitric, phosphoric, acetic acid), hydrogen peroxide, bromine, chromium. At one of the plants using gaseous hydrogen chloride, stainless steel components broke down after two months. But as soon as the steel was replaced by tantalum, even the most subtle details (thickness of 0.3 - 0.5 mm ) was almost eternal life of their increased up to twenty years. Only hydrofluoric acid may say that before it passes the tantalum.

Tantalum cathodes used in the electrolytic recovery of gold and silver. The advantage of these cathodes that precipitate gold and silver dissolved Imperial vodka, which may not cause harm to the tantalum.

Unique quality tantalum - its high biological compatibility with living tissues, i.e. the ability to get along with body tissues, causing them irritation. This property explains its wide application in medicine, mainly in reconstructive surgery to "repair" of the human body. Records from this metal is used in the damage to the skull. The literature describes the case when tantalum plate was created artificial ear, and transplanted with thigh skin is so well established that the ear was difficult to distinguish from the real. Tantalum yarn is used for compensation of muscular tissue. Using tantalum surgeons strengthen after the operation, the wall of the abdominal cavity. Tantalum clips, such as those that sew notebook, securely connect the blood vessels. Grid of tantalum used in the manufacture of artificial eyes. Thinnest filaments of the metal replaces the tendons and even nerve fibres. And if the expression "nerves of steel" is usually used in a figurative sense, people with tantalum nerves you may not often met on the street.

Tantalum in the service of medicine

Medicine though not the most important, but perhaps the most noble occupation of tantalum. Right, there is something symbolic in the fact that the share of metal, named after the mythological Martyr, was a humane mission is to alleviate human suffering and torment.

For medical needs, takes approximately 5% of the world production of tantalum. About 20% consumes chemical industry. The main order of this metal and its compounds (more than 45%) comes from metallurgists. In recent years, the tantalum is increasingly used as an alloying element in special steels - high strength, corrosion resistant, heat resistant. The action exerted on the steel tantalum, similar to the effect of niobium. The addition of these metals to the usual corrosion resistant chromium steels improves their strength, reduces fragility after quenching and annealing.

A very important application area of the tantalum - production of heat-resistant alloys, in which more and more in need of rocket and space technology. The remarkable properties of constructional alloy consisting of 90% tantalum, 10% tungsten. Sheets of this alloy can be applied up to 2500°C, and more massive parts meet monstrous temperature is above 3300°C! Abroad this alloy is considered quite reliable for the manufacture of injectors, exhaust pipes, parts of the gas systems of control and regulation, leading edge and many other important units of space ships. In those cases, when the nozzle of the rocket cooled liquid metal that can cause corrosion (lithium or sodium), without alloy of tantalum-tungsten is simply impossible to do.

Even more striking is the resistance of parts of santalova-tungsten alloy, if they are coated with a layer of carbide of tantalum (melting temperature 4000°C). In a test missile launches such nozzle withstand huge temperature at which the alloy uncoated quickly corroded and destroyed.

The tantalum carbide is different and very high hardness (close to the hardness of the diamond), thanks to which it is widely used in the production of hard alloys. When high-speed cutting metal so heated that the chip is welded to the cutting tool edge it is painted, it'll break. Cutting tools made of hard alloys based on the carbide of tantalum, chipping is not threatened, and they serve a very long time.

Many of the entries in the "work-book" tantalum indicate its close ties with electric current: a significant part of world production of this metal is consumed electrical and electro industry. Tantalum rectifiers used in the signal service of the Railways, telephone switches, fire alarms systems. Miniature tantalum capacitors used in transfer stations, radar and other electronic circuits.

Tantalum is a material for various parts vacuum devices. As niobium, he is an excellent getter, i.e. getpagetitle. So, at 800°C tantalum able to absorb 740 volumes of gas. Adsorbing gases remaining in the tube after evacuation of the vacuum pumps, getters provide a high degree of vacuum. Tantalum produce hot valves lamps - anodes, grids, cathodes indirect heat and other heated items. In the tantalum especially need those lamps operating at high temperatures and stresses, must keep accurate characteristics. In some types of vacuum tubes tantalum is used to maintain the gas pressure at a certain level.

Tantalum wire can be found in cryotron - superconducting elements used in computing.

Will mention about another electrical lesson tantalum: it serves as an excellent material for gas arresters. The metal, as if out of solidarity with his mythical namesake, Tantalum, defying Zeus the Thunderer, discharging lightning, which he in anger sends to earth.

In the manufacture of artificial silk drawing dies for pulling threads have tiny holes and their diameter is equal to the hundredth fractions of a millimeter. Portages are often clogged, and they constantly have to clean. However, the diameter of the hole should remain strictly constant. Naturally, for a portage necessary durable, wear-resistant, decoratively material. That is why these items are made from tantalum metal, meets all these requirements.

Recently tantalum began to try their hand at jewelry: in many cases, he successfully replace platinum. This replacement gives huge savings because platinum is many times more expensive than tantalum. Jewelry activity of the metal contributes to its ability to cover a thin film of a beautiful rainbow of colors. Tantalum is used for the manufacture of watches, bracelets, and various decorations.

The international Bureau of weights and measures in France and the Bureau of standards applied tantalum instead of platinum for the manufacture of standard analytical weights precision. In the production of nibs for pens automatically handles tantalum acts as a substitute for very expensive iridium.

Of course, to compete on cost with platinum or iridium to tantalum hard, but the price is also quite high. This is largely due to the high cost used in the production of tantalum materials and complexity of the production technology. Suffice it to say that to produce 1 ton of tantalum concentrate need to process up to 3000 tons of ore. But all the costs are paid back with interest.

...Were relegated to the area of legends younger years tantalum, when he was full of energy and desire to work, but nevertheless risked being branded as a parasite. In our days, as you have seen, the work of this metal enough. And how important, useful and interesting cases he has yet to do!..

 

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