The first ceramic products appeared long before people learned to melt metal. Ancient pots and jugs that archaeologists find to this day are proof of this. It is worth noting that the ceramic material has unique properties that make it simply irreplaceable in some areas. Let's look at the features of ceramics with you, talk about its production and characteristics.
General information
Ceramic products are obtained by sintering clay and mixtures with organic additives. Sometimes oxides of inorganic compounds are used. The first such products appeared 5,000 years ago. During this time, the production technology has improved significantly, and today we have access to high-strength ceramic products. They are used in construction for cladding facades, floors, walling, etc.
There are ceramic products with a dense and porous shard. The key difference between the two is that the tight shard is waterproof. These are porcelain, floor tiles, etc. Porous shards - tiles, ceramic stones, drainage pipes and more.
History of occurrence
The word "ceramics" in Greek means "clay." Naturally, for the manufacture of any product a kind of mixture was used. The necessary materials were added to it, depending on what needed to be obtained in the end. At first, manually, and somewhat later on a special machine, the clay product was given a special shape. Subsequently, ceramic products are fired in furnaces at high temperature.
Many countries used their own production technologies. This applies to pottery, painting and glazing. The first state that has achieved significant development of this industry is Egypt. It was the production of ceramics that was established in the first place. The products were made of coarse and poorly mixed clay, but the technology was further improved. Today, yellow clay bricks are found that were allegedly used in the construction of the Memphis Pyramids.
The appearance of china
For a long time, China used such material as jade. It was beautiful, but rather fragile and difficult to process. After many years of searching, a solution was found. Porcelain is easier to manufacture. Nevertheless, there were some nuances. For example, mica and zwaoku, which were found in "porcelain stones", were ground into fine powder and stored for more than 10 years. This was done in order to make the material as plastic as possible. The first porcelain in China was tall and elongated vessels. They had a polished surface and a blue or dark green color. The latter were valued the most.
Today it is believed that China is the state where porcelain was most widely distributed. This is true, although it was popular in Europe, but appeared there later, and its production developed longer.
The main types of ceramics
Currently, clay products have a broad classification. So, pottery can be divided into two main groups:
- unglazed ceramics (terracotta and pottery);
- glazed (majolica, faience, porcelain, chamotte).
Terracotta - from Italian "scorched earth". Products are made of colored clay and have a porous structure. From terracotta make vases, dishes, as well as toys and tiles.
Pottery is more difficult to process. In order to make it waterproof, glossing is necessary. Further, the product is subjected to staining. To do this, it is left in a hot oven in smoke until it cools completely. Today, many types of ceramics, in particular pottery, are extremely popular. It is used in everyday life for storing milk, bulk materials or as a decor.
As for the second type - glazed ceramics, then porcelain and faience are the most popular. The first is more expensive and time-consuming to manufacture, the second is practical and cheap. They differ among themselves in that porcelain products contain less clay and more special additives. In addition, porcelain shines through in the light, unlike faience.
About Refractories
Clay mixtures are refractory. Depending on the purpose, they can withstand temperatures from 1,300 to 2,000 degrees Celsius, and even higher. A special ceramic kiln is used. Refractory materials are most used in the metallurgical process. There they are used for the construction of blast furnaces and units.
It is logical to say that with increasing temperature the strength of the refractory is not lost, but, on the contrary, increases. This is achieved due to the presence in the composition of refractory oxides, silicates and borides. They are used almost everywhere where high-temperature processes take place. Very often they are found molded, that is, in the form of a specific product, for example, a brick. Less commonly, the use of unformed refractories in the form of a powder is necessary.
Ceramics in construction
The advantages of ceramic materials are that their stocks are practically unlimited. Along with the simplicity of production and high durability of such a product, today it is indispensable in the construction industry. If we take wall materials, then the clay brick occupies a leading position .
The same applies to ceramic tiles, which, despite the appearance of polymers, do not lose ground. It is still used to equip rooms with high humidity and temperature. Among the facing materials, expanded clay occupies the first place.
Over the past few years, the production of hollow ceramic block and brick has increased by 4%. For their manufacture, minimal changes are needed at the brick factories, while the costs pay off for the first year of sales. Abroad, hollow ceramics has long taken a leading position and is sold much better than ordinary brick.
Special ceramic materials
Such products include sanitary and sewer pipes. The first are divided into three large groups:
- from solid faience (porous shard);
- sanitary porcelain (sintered shard);
- half porcelain (half-caked shard).
The main requirements for sanitary products are resistance to mechanical damage, heat resistance. The recipe must be observed in strict order, the same applies to technology. Only a professional ceramic kiln and high quality raw materials are used. Sanitary products include sinks, toilets, bathtubs, radiators, etc. The surest way to check the quality of a product is to tap it lightly on the body. The sound should be clear and without rattling. This indicates firing at the correct temperature and no cracks.
As for sewer pipes, they should have a dense sintered shard. Ceramic pipes are produced with a diameter of 150-600 mm. Usually coated with glaze both inside and out. Such products are characterized by high resistance to aggressive environment and stray electric current. They have a moderate cost, which makes them more affordable.
Physico-chemical properties of ceramics
As noted above, all products can be divided into two broad groups: dense and porous. Dense ones have a water absorption coefficient of less than 5%, porous - 5% or more. The last group includes the following products: clay bricks (porous and hollow), hollow wall stones, tiles, roof tiles. Dense ceramic products - road bricks and floor tiles. In the sanitary industry, both porous and dense ceramics are found.
Speaking about the physicochemical properties, one cannot fail to note the key disadvantage of ceramics. It consists in increased fragility in comparison with other materials. Nevertheless, high availability and versatility make this material one of the most popular in many industries and even in everyday life. Modern technology allows you to get a smooth surface immediately after firing. If you want to achieve a certain color, then add oxides of iron or cobalt.
Microstructure Features
When heated, the ceramics gradually becomes liquid. It has a large number of simple and complex compounds. During cooling, crystallization occurs. It manifests itself in the precipitation of pure crystals, which increase in size. When the mass hardens, a microconglomerate is formed in the structure. In it, mullite grains are cemented by a hardened mass. It is worth paying your attention that oxygen atoms form a kind of matrix. Small metal atoms are present in it, which are replaced in the voids between them. Consequently, ionic and somewhat less covalent bonds predominate in the microstructure. Chemical stability and stability are achieved due to the presence of strong and durable chemical compounds.
As noted above, the use of ceramic materials is limited. This is due to the fact that the crystals are imperfect. Crystal lattices have many defects: pores of atomic size, deformation, etc. All this significantly worsens the strength. However, there are some nuances here. For example, while observing the technology during the manufacture of a particular type of ceramic, it is quite possible to achieve good strength results. For this, it is extremely important to observe the temperature regime and the duration of firing the product.
Characteristics and properties of clay
Clay is a sedimentary rock that, regardless of its composition and structure, forms plastic material when mixed with water. After firing - a stony body. Usually the mixture is dense, to a greater extent consists of aluminosilicates. Often in clays are found and rocks such as quartz, spar, pyrite, as well as hydroxides and carbonates of calcium, magnesium and titanium compounds.
Kaolins are the purest clays known today. Almost completely consist of kaolinite. After firing, they turn white. The plasticity required for processing is achieved due to the presence in the structure of small grains of clay substance (0.005 mm). Naturally, the greater the composition of such a substance, the higher the ductility, and vice versa.
The main ceramic properties of clays are:
- plasticity - deformation without breaking integrity;
- connectedness;
- air and fire shrinkage;
- fire resistance.
Today, various thinning and enriching additives are used, which allow you to change the properties of the material in one direction or another. This leads to the fact that ceramic products become even more popular and affordable.
Technological scheme of production
The characteristic of ceramic materials indicates the possibility of using clay in various industries. This led to the fact that there was a great demand, and therefore, supply increased. Production plants in most cases work according to the same scheme:
- extraction of raw materials;
- training;
- shaping and drying;
- firing and product release.
To minimize costs, factories are usually erected in the immediate vicinity of a clay deposit. Extraction is carried out in an open way, that is, with an excavator. The next step is the preparation of the mass. Raw materials are enriched, crushed and mixed to a homogeneous mass. The formation of future ceramic products is carried out by wet and dry methods. In the first case, the mass is moistened to 25%, and in the second - not more than 12%.
Previously, natural drying was often used. However, the result depended mostly on the weather. Consequently, the plant stands in rain or cold. Therefore, special dryers (gas) are used. The most critical step is firing. It is imperative to adhere to technology that is quite complex. Much depends on the cooling of ceramics. A sharp temperature difference is not allowed, which can lead to curvature of the plane. Only then can ceramic materials be sold. The production technology, as you see, is not simple, consists of several stages. Each of them must be respected. If this does not happen, then on the shelves of the store we can meet marriage.
A bit about the disadvantages of ceramics
As already mentioned, the composition of ceramic materials is imperfect. In particular, this affects the strength of the clay product. Any mechanical damage can occur as a chip, crack, etc. This is a key drawback. But there are other factors that hinder the widespread dissemination of the material we are considering. One of them is high cost. For example, ceramic tile for the roof of a country house is an excellent solution from an aesthetic point of view, but such a pleasure will cost a lot.
At the same time, its appearance will remain for no more than 5 years with proper care. In the future, fading occurs, the appearance of moss on the surface, etc. Along with this, fragility and brittleness lead to the fact that any mechanical damage can lead to leakage of the roof, and few people will like it. Of course, modern ceramic material looks very impressive, which is achieved due to the wide texture of colors and high quality workmanship. But it is still expensive, which often makes you think about the appropriateness of such a choice.
To summarize
We examined the basic properties of ceramic materials. Based on the foregoing, we can conclude that such products have some uniqueness. It consists in the fact that in the absence of mechanical damage, they will last a very, very long time. In addition, ceramic material for casting liquid metal in factories is also indispensable, because it withstands high temperatures.
As for everyday life, then ceramics are very welcome. Special dishes for cooking in the oven, although it has changed its appearance over the years, but is still made from this material. Porcelain, despite its high cost, has an elegant appearance and is simply pleasing to the eye. This also applies to faience, which, when properly executed, is difficult to distinguish from porcelain.
In any case, it is necessary to use ceramic material. This is primarily due to the large reserves of natural clay. There are really a lot of it, and every year more and more new careers are being developed for the extraction of this natural resource. The second important factor is environmental cleanliness. Previously, people generally did not have the opportunity to use any harmful additives to improve the strength characteristics of the product. Today the situation has changed, albeit not too critical. Ceramic tile, unlike synthetic materials, is not harmful to health. This also applies to ceramic dishes, which, compared to plastic, especially if the latter is heated, does not harm at all.