Despite the fact that increasingly in industry andlife is used artificially created materials, to abandon the use of metals is not yet possible. They have a unique combination of properties, and alloys allow maximum use of their potential. In what areas is the production and use of metals?
Characteristics of a group of elements
Metal is understood to mean a set of inorganic chemicals that have characteristic properties. Typically, they include the following:
- high thermal conductivity;
- plasticity, relative ease of machining;
- relatively high melting point;
- good electrical conductivity;
- characteristic "metallic" luster;
- the role of the reducing agent in the reactions;
- high density.
Разумеется, не все элементы этой группы обладают all these properties, for example, mercury at room temperature is liquid, gallium melts from the heat of human hands, and bismuth can hardly be called plastic. But in general, all these traits are traced in the aggregate of metals.
Internal classification
Metals are conventionally divided into several categories, each of which combines the elements closest to each other in various parameters. There are the following groups:
- alkaline - 6;
- alkaline earth - 4;
- transitional - 38;
- lungs - 7;
- semimetals - 7;
- lanthanides - 14 + 1;
- actinides - 14 + 1;
Outside the groups there are two more: beryllium and magnesium. Thus, at the moment, among all the open elements, 94 scientists are referred to as metals.
In addition, it is worth mentioning that there are othersclassification. According to them, noble metals, platinum group metals, post-transition, refractory, black and color are considered separately, etc. This approach makes sense only for certain purposes, so it is more convenient to use the generally accepted classification.
History of receipt
Mankind throughout its developmentwas closely associated with the processing and use of metals. In addition to being the most common elements, they could be used to manufacture different products only with the help of mechanical processing. Since there were no skills to work with ore, at first we were talking only about using nuggets. At first it was a soft metal, which gave the name to the copper age, which replaced the stone one. During this period, a method of cold forging was developed. In some civilizations, smelting became possible. Gradually, people have mastered the production of non-ferrous metals, such as gold, silver, tin.
Позднее на смену медному пришел бронзовый век.It lasted about 20 thousand years and became a turning point for mankind, because it was during this period that it became possible to obtain alloys. There is a gradual development of metallurgy, methods of obtaining metals are being improved. However, in the 13th-12th centuries, BC. e. there was a so-called bronze collapse, which laid the foundation for the Iron Age. This is presumably due to the depletion of tin stocks. And lead and mercury, discovered at this time, could not become a replacement for bronze. So people had to develop the production of metals from ores.
The next period lasted for a relatively short time -less than a millennium, but left a bright mark in history. Despite the fact that iron was known much earlier, it was almost not used because of its disadvantages compared to bronze. In addition, the latter was much easier to obtain, while ore smelting was more labor intensive. The thing is that native iron is rare, so it's not surprising that the rejection of bronze occurred so slowly.
Importance of skills in metal extraction
By analogy with how the ancestor of man for the first timemade a tool of labor, tying a sharp stone to a stick, the transition to a new material was just as grandiose. The main advantages of metal products were that they were easier to make, and there was also the possibility of fixing. The stone does not have plasticity and malleability, so that any tools from it could only be made anew, they could not be repaired.
Thus, it is the transition tometals led to the further improvement of tools, the emergence of new objects of everyday life, ornaments, which were previously impossible to produce. All this gave impetus to technical progress and laid the foundation for the development of metallurgy.
Modern methods
If in ancient times people were familiar onlyobtaining metals from ores, or they could be satisfied with nuggets, there are currently other ways. They became possible due to the development of chemistry. Thus, there were two main directions:
- Pyrometallurgy. It began its development earlier and is associated with the high temperatures necessary for processing the material. Modern technologies in this field also allow the use of plasma.
- Hydrometallurgy.This direction deals with the extraction of elements from ores, waste, concentrates, etc. with the help of water and chemical reagents. For example, the method involving the production of metals by electrolysis is extremely common, and the cementation method is also quite popular.
There is another interesting technology.The production of precious metals of high purity and with minimal losses became possible thanks to it. It's about refining. This process is one of the types of refining, that is, the gradual separation of impurities. For example, in the case of gold, saturation of the melt with chlorine is used, and platinum is dissolved in mineral acids, followed by isolation with reagents.
Кстати, получение металлов электролизом чаще all is applied, if smelting or restoration are economically unprofitable. This is the case with aluminum and sodium. There are also more innovative technologies that make possible the production of non-ferrous metals even from fairly poor ores without significant costs, but this will be discussed a little later.
About alloys
Most of the metals known in antiquity are notalways met some needs. Corrosion, insufficient hardness, fragility, fragility, fragility - each element in its pure form has its drawbacks. Therefore, it became necessary to find new materials combining the advantages of the known ones, that is, to find ways to produce metal alloys. To date, there are two main methods:
- Casting. The melt of the mixed components is cooled and crystallized. It is this method that made it possible to obtain the first samples of alloys: bronze and brass.
- Pressing. The mixture of powders undergoes high pressure, and then is sintered.
Further improvement
In recent decades, the most promisingit seems the production of metals using biotechnology, primarily with the help of bacteria. It has already become possible to extract copper, nickel, zinc, gold and uranium from the sulphide raw materials. Scientists hope to connect microorganisms to such processes as leaching, oxidation, sorption and precipitation. In addition, the problem of cleaning deep wastewater is extremely topical, for it, too, are trying to find a solution that involves the participation of bacteria.
Application
Without metals and alloys, life inthe kind in which it is now known to mankind. High-altitude houses, airplanes, dishes, mirrors, electrical appliances, cars and many other things exist only thanks to a distant transition of people from stone to copper, bronze and iron.
Due to its exceptional electrical andThermal conductivity metals are used in wires and cables for a variety of purposes. Gold is used to make non-oxidizable contacts. Due to their strength and hardness, metals are widely used in construction and for obtaining a variety of designs. Another area of application is the instrumental. Hard metal alloys and special types of steel are often used to make the working part, for example, the cutting part. Finally, precious metals are highly valued as a material for jewelry. So there are plenty of applications.
Interesting about metals and alloys
The use of these elements is so widespread andhas such a long history that it is not surprising the emergence of various curious situations. They and just a couple of interesting facts and should be brought to the end:
- Prior to its widespread use, aluminum is verywas appreciated. The cutlery that Napoleon III used to receive guests was made from this material and was the pride of the monarch.
- The name platinum in Spanish means"silver". Such an unflattering name element was received due to the relatively high melting point and, consequently, the inability to apply it for a long time.
- In pure form, the gold is soft, and it can easily be scratched with a fingernail. That is why to make jewelry it is fused with silver or copper.
- There are alloys with a curious property of thermoelasticity, that is, the "memory" effect of the shape. With deformation and subsequent heating, they return to their original state.
