Introduction to Ceramics and Refractory
Products made from refractory fibrous material - source (shutterstoc images)
Refractory ceramics are a special type of ceramic material that have incredible heat-absorbing properties. There are other types of refractories that are highly tolerant to corrosion. This impressive combination of properties makes them a perfect choice for industrial processes or mechanical applications involving extremely high temperatures.
Ceramic pottery images - shutterstock
Another quality of refractory materials is their tolerance when they are exposed to chemicals. This characteristic makes them ideal for use in industrial applications that involve the use of chemicals, thus eliminating any chance of corrosion.
Image showing high temperature furnace - (source: Shutterstock image)
Still, certain types of ceramics have been extensively applied in the making of electronics. Critical components of electronic devices, such as transistors, diodes, and resistors, are made using ceramic refractories. Thanks to their superconducting or semiconducting characteristics, they make an excellent choice for use in electronic gadgets.
What Are Refractory Ceramics Made Of?
Refractory ceramics are made from naturally occurring minerals that are usually inorganic and nonmetallic.
Aluminum oxide is one ingredient used in making refractories - Sutterstock
The major raw materials used in the making of refractories are:
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Magnesium
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Aluminum
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oxides of silicon
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Zirconium
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Calcium
Refractories are also made using materials that are non-oxide, such as:
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Nitrites
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Carbides
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Silicates
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Borides
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Graphite.
Another important point to note is that the type of material used to make a refractory product determines its application. For instance, a refractory product that is made from a thermally stable mineral aggregate can be used in a blast furnace.
Similarly, refractive ceramics made from components that are less reactive to chemicals are typically used in industrial processes. This helps to eliminate any chances of corrosion in critical components of the industrial equipment.
Categories of Refractories
Refractories are classified into two main categories. The first is a type having preformed shapes or compositions that are unformed. The second category of refractory ceramic fibers includes those that have high thermal absorbing capability. This quality makes them a perfect choice for use in making insulation materials.
Image showing refractories having preformed shapes - Shutterstock
Ceramic refractories come in various shapes and sizes depending on the type of use for which they are intended. You will find those that are molded or pressed for use in floors or bathroom walls. Yet some are made in interlocking designs or wedges for use in the internal parts of extreme temperature furnaces or boilers.
Refractive ceramic materials come in varied shapes, designs, and sizes. There are those made in small sizes for use in smaller and tiny spaces. However, you will also find some that are so massive and could weigh several kilograms.
Classifications of Refractories
Refractories are usually classified into two main forms, which are the shaped and unshaped.
Refractory bricks - Shutterstock image
Refractory bricks, which are usually referred to as shaped, come in defined shapes, while the unshaped are known as monolithic
The Shaped Refractories
The terms ‘shaped refractory’ is used to describe a type of refractories that come in a defined shape that is fixed. They are most commonly referred to as bricks but they also come in two variations of special shapes and standard shapes.
Refractory manufacturers deliver the standard shape type to users for use in kilns or furnaces of the same shape design. Conversely, special-shaped refractories are specifically made for use in particular furnaces or kilns.
Of important note is that shaped refractories, in most part, are machine-pressed, thus featuring high uniformity in their properties. However, the specially shaped refractories are commonly hand-molded and thus usually exhibit a little bit of variation in their properties.
The Unshaped Refractories
The unshaped refractories just like the name suggests often come in undefined form. Usually, they only get shaped at the time of their application. Typically, they are used in the formation of jointless linings and are referred to as monolithic refractories.
Unshaped refractories are further subcategorized into smaller groups, which include the following:
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Mortars
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Castables
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Plastic refractories
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Ramming mixes
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Gunning mixes, etc.
The 2 major types of refractories
Refractories are classified into two main types, which are dense refractories and insulating refractories. High-temperature refractories, such as firebricks, are considered high-density. They offer near-perfect resistance in extreme operating environments, e.g., slugs that have varied chemical compositions, gases, or fumes.
Image showing firebrick - (source: Sutterstock)
Insulating refractories, on the other hand, have a lower density, thus providing better insulating properties. Moreover, they also offer better resistance to corrosion and reaction to chemicals. Most of them are used in chemical industrial processes as a measure to avert the possibility of corrosion.
When Choosing a Refractory, Consider These Factors
As already mentioned in the article, refractories come in varied forms, shapes, and types depending on application. If you are looking to use any given refractory product, then you should consider the following factors:
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Nature of application – It is important for you to take cognizance of the kind of application you want to use the refractory for. Is it going to be in a furnace involving extremely high temperatures? Or is it a highly corrosive environment?
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The structural load - This is also an important factor to look at when looking for the kind of refractory to employ. The structural load is the weight limit that a given refractory material may be able to withstand without getting damaged.
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Its porosity – The porosity of a refractory refers to the open spaces or pores. This has an effect on its physical behavior when it is subjected to stress.
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The cost of the refractory – The cost is yet another important factor worth considering when choosing a refractory.
In Conclusion
In the article, you have learned about what refractories are, including the various types and uses in different industries. Here’s a recap of the main points covered in the article:
Refractory ceramics come in varied types, shapes, and forms based on intended applications. For instance, you will find refractive ceramic materials that have high-temperature resistance characteristics used in furnaces. Corrosion-resistant refractories, on the other hand, are installed for use in highly corrosive industrial environments.
Your choice for the type of refractive product should always be guided by your intended application or use. If your industry is involved in high-temperature heating processes, then thermal-absorbing refractory ceramics would be the perfect option.