How metals are formed
Do you have a ring on your finger? What is it made of: gold, silver, platinum or some other metal? Then think about this: the metal from which the ring is made on your finger, is older than the planet where you live.
What is "metal"?
Scientifically, metals are natural chemical elements that are usually hard and shiny; in addition, they are considered good conductors of heat and electricity. These include iron, gold, silver, copper, zinc, nickel, etc., as well as elements that we are not used to refer to metals. An example is sodium, a metal that we regularly eat. Sodium is a soft, silvery-white metal that usually combines with the element chlorine to form sodium chloride, or, simply speaking, common salt.
Another example is astatine, which was artificially created under laboratory conditions in 1940. In nature, it was discovered only three years later. Astat is highly radioactive. It is believed that on Earth there are only about 30 grams of this metal.Of the 118 chemical elements known to us, 88 are metals.
So, how did all these metals come about? Here is a very simplified explanation:
All elements, including metals, are made of the same: atomic material - electrons, neutrons and protons. Atoms of various elements can be distinguished from each other by the number of protons they contain. (The number of neutrons and electrons can vary even among atoms of the same element.) For example, a hydrogen atom contains only one proton, an iron atom - 79. This is also true for each of the countless hydrogen and gold atoms in the Universe.
If you could find a way to turn 79 hydrogen atoms into one, you would get an atom with 79 protons, that is, an atom of gold. This is exactly what is happening ... however, not on Earth, but inside the stars.
Gold in the stars
About 13.7 billion years ago, matter first appeared in the form of atoms of the two lightest elements: hydrogen with one proton and helium with two. They certainly remain the most common elements in the universe.
After many millions of years, those first atoms of hydrogen and helium formed clouds of dust and gases, and so large that they could be measured in light years (1 light year = 9.5 trillion kilometers).The clouds eventually succumbed to their own huge gravity and dissipated, forming the first stars. The stars became atom destroyers — hot enough to break up the atoms of hydrogen and helium into small particles and subsequently form large atoms of heavier elements from them.
For example, if you connect two atoms of hydrogen, you will get an atom with two protons - or helium. Connect three atoms of hydrogen together - and you get an atom with three protons - lithium, the first and the lightest metal. Connect three atoms of helium - and you get an atom with six protons - carbon. This is the process that occurs in all the stars that you see in the sky at night. In massive stars, the process can lead to the formation of heavier elements, including metals such as titanium (22 protons) and iron (26 protons). If stars are supermassive, they are capable of forming the heaviest metals, such as gold (79 protons) and uranium (92 protons). This is one of the functions that stars perform, and an explanation of how all elements are formed in nature, including shiny metals.
And now let's consider how they were on Earth.
In the first few billion years after the Big Bang, millions of stars were born - as a result of the process we just described. Some of them were supermassive - hundreds of times larger than the sun. Massive stars live relatively little — only a few million years (small stars can live for billions of years) at best — after which they die as a result of an explosion and become supernovae.
When these massive stars exploded billions of years ago, they threw into space the heavy elements that they managed to form. They, so to say, "littered" the Universe with elements, including metals, in an incomprehensible amount - trillions, trillions and trillions of megatons. This means that when new stars later formed, they were already “littered” with metals left by supernovae.
One of these later metal-rich stars was our sun. Let's briefly review the history of its occurrence:
Approximately 4.5 billion years ago, a massive cosmic cloud of dust and gas, strewn with lots of heavy elements, dissipated, launching the process of forming a new star.
Most of the hydrogen and helium in the cloud turned into a star.The remaining amount of dust and gas, including metals, has accumulated in the red-hot mass, rotating around a new star. The spinning motion flattened the mass (like pizza dough), turning it into a hot spinning disk.
Over the course of millions of years, the disk gradually cooled, and its parts stuck together among themselves here and there, forming lumps. These clumps later became the planets of our solar system. And what happened to the metals in the dust? They became all those metals found on all the planets, including ours.
There is a lot of metal on Earth. Almost one third of the mass of our planet is iron, the largest part of it is concentrated in the core. The other 14 percent is magnesium, 1.5 percent is nickel and 1.4 percent is aluminum. This is 49 percent of the planet. Other metals of the Earth, including "precious", such as gold, silver, platinum and palladium, exist in insignificant quantities. The rest (not metals) is about 30 percent oxygen and 15 percent silicon, along with other non-metallic elements.
Look how glitters!
For at least several million years, people and their ancestors used tools made from materials such as wood, bone, and stone to make their lives easier.However, they didn’t really succeed: Homo sapiens remained relatively primitive nomadic hunters and gatherers for almost their entire existence. Then, about 10 thousand years ago, they began working with a "new" material: metal.
The first metals that people began to use were those with which it was easiest to work. These are native metals - metals that are found in nature in their pure form or were naturally mixed with other elements, while retaining all their properties. These include copper, tin, lead, silver and gold.
People may have found nuggets of these metals in a stream or among the roots of an excavated tree. They then shaped them with stone hammers. This led to the emergence of jewelry and jewelry, as well as metal tools and weapons such as axes, knives and swords (this was an improved replacement for old stone tools). All this, ultimately, led to the fact that people began to actively search for metals, create mines, trade between different nations and develop the metalworking industry.
Approximately 8,000 years ago, people began to realize that they could change metals. Perhaps they discovered it at random, and perhaps it was a rush of creativity - or both. In any case, new processes were developed to create new metals that did not exist in nature at all. Over the next several thousand years, the extraction and processing of metals became an integral part of most cultures on Earth, and the metal became one of the substances that changed the history of mankind. Each of these new processes involved fire, and it is quite possible that experiments with it directly led to the following major achievements:
1) Annealing. This is the process of heating the metal until it turns cherry red. It allows you to return the old pliable metal to its original pliable condition, as well as to recycle it and extend its service life. Annealing can be performed at relatively low temperatures (copper can be burned at the stake). This process was first used around 6000 BC somewhere in the Middle East, and perhaps around the same time in Europe and India.
2) Melting.During this process, metals become liquid, which makes it possible to give them various forms. For the first time, metals were smelted around 5000 BC, after the appearance of advanced ceramic kilns that could produce higher temperatures than open fire.
3) Alloys production. It is the process of mixing various metals while they are in the molten state. It appeared around 3300 BC (the beginning of the Bronze Age). The first alloy was bronze - a mixture of copper and tin, which is much stronger than its components, taken separately.
4) Extraction of metal from ores. With further improvement of kilns and ways to achieve higher temperatures, methods have been developed that allow the extraction of metals from ore. It was first done with iron in the Middle East around 1500 BC, which was the beginning of the Iron Age.
5) Melting, the production of alloys and the extraction of metal from ores were practiced by the ancient people in Europe, Asia, South America and Mexico, but in Australia and the rest of North America they became available only after the arrival of Europeans.These simple processes are still the basis of what has perhaps become the largest and most successful industry in the history of mankind: the metal industry.
Iron is the most common metal on earth. But, as in the case of most metals, its mining is a complex process, since in nature it is very rarely found in its pure form. As a rule, it is obtained from iron ore, which is purified from oxygen and impurities. Here is the most common process used today:
Preparation: after extraction, iron ore is ground into powder. In order to separate iron-rich ore, huge magnetic drums are used. (Iron-rich ore sticks to the drums; the rest falls off.) The iron-rich powder mixes with clay and turns into small balls, which are then subjected to thermal hardening. This allows a much more efficient flow of the next process - smelting.
Melting: the balls are melted in a furnace along with coke — coal, which has been processed into almost pure carbon — and limestone. Intense heat destroys iron-oxygen bonds in the ore, releasing oxygen,which combines with carbon resulting from the combustion of coke and turns into CO2 (carbon dioxide). CO2 comes out of the upper part of the furnace, and the iron, which is now free of oxygen, melts (at a temperature of about 1,540 degrees Celsius) and is collected at the bottom of the furnace. Limestone also melts and combines with impurities, forming waste, known as slag. Slag is lighter than iron, and is constantly removed from the top of the furnace.
Result: The product of this process is cast iron. It has a relatively high carbon content of about 5 percent, which makes it very brittle and, therefore, almost useless, except that it can be used to produce other iron alloys, especially steel.
Today, about 98 percent of pig iron produced worldwide is used to produce steel, the most widely used metal or metal alloy in history. The process begins with pouring molten iron into steel-smelting furnaces, where it is processed to remove the remaining impurities and reduce the carbon content to 0.1-0.2 percent. This is one of the main characteristics of steel, which helps to reduce brittleness, increasing strength and hardness.Depending on the type of steel being produced, various elements may be added to the mixture. Consider two examples:
1) Manganese steel, or Hadfield steel, contains about 13 percent manganese, thanks to which it has extraordinary strength. It is used in the production of mining tools, equipment for crushing rocks and protecting military equipment.
2) Stainless steel. In fact, this is the name for a wide range of steel, but they all have one common element in the composition: chrome (from 10 to 30 percent, depending on the type). Chromium on the surface of stainless steel combines with oxygen in the air and forms a layer of chromium oxide, which gives the stainless steel a shiny appearance and makes it resistant to corrosion. And if it is somehow damaged or scratched, chromium will reconnect with oxygen and form a new layer, that is, it turns out that stainless steel is self-healing.
Stainless steel is used in the manufacture of a wide range of products, ranging from kitchen utensils to surgical equipment and street sculptures. (It is also 100% recyclable.)
The most common ore used to produce aluminum is bauxite, a substance that contains about 50 percent alumina. As in the case of iron, to get aluminum, you need to separate the ore from oxygen and minerals. This process is much more complicated than iron mining, and it was developed only in the late 1800s. (Aluminum was recognized as a unique element only in 1808.) The first part of the system most often used today is called the Bayer process, named after the Austrian chemist Carl Bayer, who invented it in 1877.
The Bayer Process: Bauxite is mined and crushed, then mixed with water and lye and heated in tanks. Heating and lye are designed to dissolve aluminum from ore in water. Meanwhile, the impurities themselves sink to the bottom. Water enriched with aluminum is subsequently pumped out and filtered to remove the remaining impurities. After that, it is pumped into huge septic tanks. The white crystalline powder obtained after settling consists of 99 percent alumina. The crystals are washed and allowed to dry.
The next step is known as the Hall-Eru process, named after the two chemists who developed it - independently of each other - in 1886. During this process, aluminum oxide crystals (along with minerals that contribute to the decomposition of aluminum oxide) melt at a temperature of 960 degrees in steel vats. However, this is not enough to destroy aluminum-oxygen bonds in alumina; they are much stronger than iron-oxygen bonds. Thus, a powerful electric current is passed through the molten material - and this leads to the breaking of bonds. Oxygen is released and attracted to carbon rods suspended above the molten mixture. It combines with carbon and forms CO2. The released aluminum melts and collects at the bottom of the tank. This is 99.8 percent pure aluminum.
Aluminum is used both in pure form (aluminum foil is made of almost pure aluminum), and in various alloys with silicon, copper and zinc. Some of them are stronger and lighter than steel. Kitchenware, cans and a cylinder block (engine) are produced from aluminum.
Platinum is a shiny silver-white metal that is very rare and has unique properties: it is one of the most dense metals, but it is very ductile and resistant to corrosion (temperature, rust, acids). It has a melting point of 1779 degrees Celsius (gold melts at a temperature of 1064 degrees Celsius, and iron - at 1535 degrees Celsius). Platinum exists in its pure form in nature, but most often it is found in a mixture with other elements, including oxygen, copper and nickel. More than 90 percent of platinum today is mined in just four places: three of them are in Russia, and one is in South Africa.
Production is quite complicated.
To get one ounce (28.3 grams) of platinum, you need to extract and process ten tons of ore. The platinum production process is as follows:
The ore is mined, ground into powder and mixed with water and chemicals. Then the mixture is blown with air that forms bubbles - tiny platinum particles subsequently adhere to them. Bubbles rise to the surface of the tank, creating a foam. This foam is collected, dried and melted at a temperature of 1482 degrees Celsius. Heavier particles - metals - fall to the bottom of the furnace.Lighter impurities are collected on the surface of the molten metal and removed. Subsequently, complex chemical processes are used, as a result of which platinum is separated from copper, nickel and other metals until it is completely pure.
Interesting facts related to metals and metalworking industry
• Iron ore is smelted in a blast furnace: the air heated to a temperature of 1204 degrees Celsius is “blown” into the furnace, causing it to burn even more than usual. A typical blast furnace in a steel plant operates 24 hours a day, 365 days a year. Its service life under such conditions is 20 years.
• Pure steel is susceptible to corrosion. Galvanized steel is zinc plated steel that is resistant to corrosion.
• The main chemical element in rubies, emeralds and sapphires is aluminum.
• What is the extremely rare metal platinum used for? For the production of catalytic converters - devices on cars that are used for cleaning exhaust gases. Platinum is an exceptionally good catalyst: it helps convert toxic gases, such as carbon monoxide, to non-toxic gases.
• It is a myth that Native Indians did not do metalworking.In fact, many tribes had a long tradition of copper processing, especially those who lived near the Great Lakes, where the metal was abundant.
• Platinum, mined in the history of mankind, could fit in the basement of an ordinary house.