Ceramics is a non-metallic and inorganic material, and after passing forming and sintering steps, due to its unique mechanical and physical properties, they are used in a variety of industries, such as construction, medicine, and automobile manufacturing.

Ceramics are a wide classification of non-metallic and inorganic materials constructed from a combination of artificial or natural compounds and have different properties like high-temperature endurance, high stiffness, and high chemical resistance. The ceramic production process includes selecting and preparing consumable raw materials, forming ceramic sections, and finally, cooking the pieces.

From eating utensils and cooking equipment to cutting tools and electronic equipment, ceramics has many applications in our daily lives. Due to their unique characteristics, these materials have multiple uses, and their usage has increased as material development and production progress. Throughout this paper, we aim to become familiar with this material from A to Z.

Ceramics are a wide classification of non-metallic and inorganic materials constructed from a combination of artificial or natural compounds. They are usually formed by shaping a compound of clay soil, mineral, and other additives and then cooking them at a high temperature to produce a stiff and high-endurance substance.

Ceramics can be found in a wide variety of productions, from building tile and decorative clay utensils to electronic and Aerospace tools with advanced technology. They are valuable because of their durability, stiffness, and resistance against heat, corrosion, and abrasion.

In addition to clay-based traditional ceramics, modern technologies made it possible to develop ceramics made of carbides, nitrides, and oxides. These advanced ceramics are more durable than traditional ones and are useful in applications such as cutting tools, engine components, biomedical implants, and bulletproof vests.

Depending on their properties and specific requirements, ceramic materials can provide advantages over steel in certain applications. A ceramic material, for example, has greater stiffness and durability than steel, which makes it ideal as a material for applications requiring resistance to abrasion and heavy abrasion. Ceramic materials can tolerate higher temperatures compared to steel without melting or destruction. Due to this feature, they are highly suitable for use in environments with high temperatures, such as jet engines. Aside from this, some of these ceramic materials are environmentally friendly, so they can be used safely without causing undesirable reactions in contact with the body.

What is ceramic made of?

Ceramics can be provided from minerals like clay, oxides, carbides, and nitrides. The compound of ceramic depends on the intended use and desired properties of the ultimate production. Traditional ceramics like clay and porcelain are usually made from a complex of clay, feldspar, and quartz, along with other additives like kaolin, bullet, and bone ash.

This mixture is formed in the desired shape and cooked at a high temperature to create a stiff and enduring material.

On the other hand, advanced ceramics can be made of a wide variety of materials. For example, silicon carbide and alumina are usually used for creating cutting tools and abrasives, while zirconia is used in dental crowns and artificial joints. Usually, ceramics are made of a combination of materials, like carbide cement, which is composed of tungsten carbide grains and joined with steel adhesives. In general, ceramics are made of minerals and processed by using high temperatures to create a stiff and enduring material with specific properties.

Ceramic production steps

Below is a general summary of the ceramic manufacturing process:

1. Selection and preparation of raw consumable materials
2. Forming ceramic pieces
3. Thermal operation of ceramics
4. Complementary and ultimate operation (if needed)

Following a thorough evaluation of the raw materials, they are ground into a suitable grade. It is essential to avoid the entrance of impurities during the preparation process. The final step of this part is mixing powder materials in wet, dry, and semi-dry states and in the presence of adhesive or its absence. The next step is shaping ceramic sections aiming to achieve a sound piece. In the final step, thermal and sintering operations are carried out.

Note that in the first step, which is selecting raw materials, parameters such as purity, the particle size of raw materials, existing fuzzy transformations in materials, and other parameters should be considered.

These factors significantly affect the quality of the final production. For example, impurities in many ordinary ceramics can be explained by their glassy phase formation and ability to help cook, although it has some limitations. However, as there are specific properties and behaviors required in engineering ceramics, impurities can cause severe changes in intended properties. Therefore, it is essential to reduce impurities in raw materials compounds as much as possible. Accordingly, raw materials preparation is of high importance. This preparation includes three overall and separate steps:

1. Grinding raw materials using a grinder or mill
2. Grading crushed materials (using different methods with a sieve) or suction with the air
3. Mixing graded materials to form a homogenous compound before crystallizing

After providing raw materials in the form of powder or granules, the next step of the ceramics manufacturing process is shaping. The most common methods to shape ceramics are:

• slip casting
• plastic formation (clay)/extrusion
• powder press (uniaxial and biaxial dry and semi-dry hot press, cold and warm isostatic press)
• melting and casting
• injection molding
• tape casting
• formation and covering thick and thin layers (CVD) and similar methods

The section complexity, raw material type, used equipment, investment amount in this field, required and intended quality, accessibility of facilities, the final price of the raw materials, and final production are crucial parameters in this step of shaping ceramic pieces using different methods, production type and considering problems. After shaping ceramic pieces and drying the system if moisture is present, sintering and cooking ceramics are the next step. The sintering aims to reduce porosity percentage, heal particles, and increase density and durability. If we heat steel or compressed ceramic powders to a temperature roughly equivalent to half of their melting point and more, they form a stick together, and an inter-particle bond is formed. This phenomenon, which has important impacts such as dimension changes, fuzzy changes, and releasing internal stresses of the section, is called sintering

What are the properties of ceramic?

Ceramics have various properties that can be classified into some general groups. In the following, we mention some of these properties.

Mechanical properties of ceramics

As the name suggests, mechanical properties are related to properties that are accompanied by stress (force). Tensile and compressive strength, stiffness, and fracture resistance are among the criteria for evaluating the mechanical properties of these materials. A main challenge of using ceramics is their brittle nature and low tensile resistance, which limits some of their applications. However, significant electrical, thermal, and optical properties of ceramics make them appropriate for various uses in industries like aerospace, medicine, and energy.

Compressive strength of ceramic

The durability of a material is its ability to tolerate stress without deformation or fracture. The compressive strength of ceramics is high, and ceramics can tolerate load under pressure without deformation. It makes them suitable for applications requiring high endurance, like cutting tools and engine parts.

Ceramic durability is affected by factors such as microscopic structure, compound, and construction process. For instance, ceramics with a fine microscopic structure and high impurity has higher endurance compared to ceramics with a coarse microscopic structure.

Fracture resistance of ceramic

Fracture resistance is the ability of a material to resist breaking the crack. Ceramics are breakable in general, which means they easily break under stress. However, some ceramics show a high fracture resistance due to the plastic deformation ability before fracture. This feature is crucial for applications involving hit or shock loads, such as bumper or cutting equipment.

Ceramic stiffness

Stiffness is the resistance of a material against compression and surface scratch. Ceramics are known for their high stiffness, which makes them suitable for applications requiring resistance against abrasion and scratch, such as abrasion and cutting tools.

Physical properties of ceramics

Physical properties of a substance are properties observable or measurable without change in the chemical compounds of the material. Ceramics are a various group of materials with a wide variety of physical properties. In the following, we note some of the most crucial physical properties of ceramics:

• Density and porosity

Ceramics have a high density, meaning they are rather heavy. Ceramics can have different levels of porosity that can affect their strength and durability and create various applications for them.

• Thermal conductivity

Thermal conductivity is the ability of heat transfer in a material. Contrary to steel materials, ceramics are weak and conducive to heat, making them useful in applications with high temperatures that require insulation.

• Thermal expansion coefficient

Ceramics have a relatively low thermal expansion coefficient, meaning that they expand or contract less than other materials by changing temperature.

• Transparency and light transition

Some ceramics are transparent and trespass the light, while other ones are opaque.

Chemical properties of ceramics

Ceramics are highly required in hard environments and environments with high temperatures and electronic pieces due to their chemical properties. In this section, we investigate the measurement criteria of chemical properties of ceramics, including chemical endurance, resistance against chemical corrosion, and stability in high temperatures.

• Chemical stability

A crucial feature of ceramics is their stability. In hard environments where chemical and acid contact is avoided, ceramics are ideal since they are resistant to chemical reactions with other materials. This feature is due to strong covalent bonds between ceramic atoms. Covalent bonds form a stable and durable formation against chemical attacks. As ceramics are chemically stable, they are useful materials for storing and transporting corrosive substances in planets of chemical production. Ceramics are also used in creating reactors and chemical pipes, which provide a long-term and durable solution for problems related to chemical corrosion.

Resistance to chemical corrosion

In addition to chemical stability, ceramics are also highly resistant to chemical corrosion. The reason for this feature is that ceramics are formed from metallic or non-metallic elements with oxygen, nitrogen, or carbon. The bonds between these elements are stable and resistant to chemical attacks, which makes ceramics usable in corrosive chemical environments.

Stability in high temperatures

Ceramics can tolerate high temperatures without experiencing significant changes in their structure or chemical properties. It is because of the high melting point of ceramics, which means they can maintain their stability and structure in high temperatures.

Electric properties of ceramics

In this section, we focus on the electric properties of ceramics, including electrical conductivity, electrical insulation, and Piezoelectric properties. Ceramics involve a wide domain of electric properties. Some of them do not allow passing electric flow even in powerful fields, and some are conductors. Ceramics can be categorized into conductors, semi-conductors, or dielectrics.

Semiconductor ceramics have a medium electric conductivity. This ceramic’s interesting property is the adjustability of electric conductivity. With the help of changing chemical compounds and production methods, engineers can produce their intended semiconductor ceramic and use it in different applications, such as electronic devices, solar cells, and thermoelectric generators. Semiconductor ceramics exhibit flow following energy adsorption due to changes in their electronic structure.

Insulation ceramics have low electrical conductivity and are used in applications demanding electric insulation, such as electric insulators and capacitors. Ceramic materials with high electric resistance are called dielectric. Although these materials are not conductive, they undergo some changes in their electric charge balance when placed in a dielectric field and acquire new properties. Dielectric constants serve as a measure of the amount of electric energy a substance can store. It is an important feature in applications like capacitors and sensors.

Piezoelectric ceramics are a type of dielectric ceramics. Piezoelectricity is the property of some ceramics that enables them to transform mechanical energy into electric energy and vice versa. These properties are used in various applications such as sensors, operators, and transducers.

Types of ceramics

Types of ceramic in terms of material

Ceramics are divided into two categories: Standard (traditional) and engineering ceramics. Standard ceramics, known as traditional ceramics, include ceramics like chinaware, all sorts of tiles, such as tiles for the floor and walls, ceramic sanitary tools, and other ceramic products installed using  ceramic adhesive. Consumable raw materials for this type of ceramic are usually clay, silica feldspar, and other materials. As a result of the abundance and cheapness of their raw materials, standard ceramics are common in Iran, and, also, as a result of the high value-added of their products, this industry has experienced significant growth and is still developing.

Processed mineral raw materials and common construction techniques are used to produce standard ceramics. There are several divisions for each group of standard ceramics; for example, one can mention provided divisions about chain wares which are sometimes based on their application and sometimes based on the properties of soft and rigid chain wares. Generally, ceramics of this type are made with clay, feldspar, and silica, but other materials can also be utilized if necessary. Engineering ceramics are used to respond to specific requirements such as higher thermal strength, better mechanical properties, particular electric properties, and chemical resistance.

These ceramics are:

1- Pure oxide ceramics: Oxides like Alumina (Aluminum oxide), zirconia (Zirconium oxide), Thoria (thorium oxide), beryllia (beryllium oxide), and magnesia (magnesium oxide) are mostly used.

2. Non-oxide ceramics: These ceramics have all kinds of nitride (aluminum nitride, silicon nitride, and boron nitride, which are refractory and have high durability in high temperatures), carbide (such as silicon carbide and boron carbide), and boride.

3- Composite compound materials (ceramic-metallic): Both ceramic and metallic phases exist in these materials.

Introduction of Porcelain Ceramic

Porcelain ceramics are ceramics with water adsorption percentages lower than 0.5% from the kaolin soil compounds and are cooked at a temperature of around 1200 C.

Compared to other standard ceramics, porcelain ceramics are highly compact, and the porosity in these ceramics is very small (roughly zero). Low porosity is the principal property of porcelain ceramics which causes desirable technical and chemical performance and high durability in this type of ceramic. In addition, porcelain ceramics are highly resistant to chemicals and detergents. High durability against corrosion and high fracture resistance, along with easy cleaning of porcelain ceramics, made them an ideal choice in industrial and congested spaces.

View more: “What is porcelain ceramic; types and functions”

Types of ceramic in terms of application

Standard and traditional ceramics have various applications and are divided based on application:

• Cement productions (like hydraulic cement that are used in construction industries)
• Whiteware (including crockeries, chain wares, and chain ware compounds)
• glazes
• Building clay productions (mostly made of bricks and tiles)
• refractory
• Glasses
• abrasive materials

In terms of function, engineering or industry ceramics can be divided into three groups functional engineering, structural engineering, and biological ceramics. Each classification has a specific performance, as stated in the following:

The first subset is known as functional engineering ceramics, which includes electroceramics, superconducting ceramics, semiconductor ceramics and electrical insulators, ceramic magnets, etc., and some productions of this subset are:

• Piezoelectric and pyroelectrics
• Insulators and ceramic dielectrics of insulators and capacitors
• Ceramic semiconductors
• Ceramic fuses
• Ceramic sensors
• Magnetic ceramics
• Optic ceramics
• electro-optic

Another subset of engineering ceramics is structural ceramics which includes engineering ceramics with better thermal and mechanical properties, such as ceramic oxide, non-oxide, and complex materials. In this set of ceramics, mechanical and thermomechanical properties are the most important ones. Some crucial structural engineering ceramics are:

•  Zirconia systems
•  Microfilters and membranes
• Catalysts and ceramic foams
•  Glass and glass-ceramics
•  Ceramic composites and cermet

The third subset is biological ceramics, which includes all types of biological ceramics and nanoceramics. Biological ceramics are drug-release systems, implants, and biodegradable ceramics.

Types of ceramic in terms of the fabrication method

Selecting a mechanism and technique to shape a ceramic piece depends on various parameters, including the following:

• Length to diameter ratio of the piece
• Size and complexity of the piece and mold design
• Raw materials type
• The possibility of forming suspension or slurry
• Powder properties
• The porosity of the piece
• Accessibility of facilities
• The final price in association with internal, regional, and global competition

Generally, in standard ceramics, traditional methods like slurry casting and shaping clay are used. These methods are available in the country with inexpensive device costs. Because of the nature of methods, including the presence of water in the supply of raw materials and even in the provision of bodies, the final products have porosity. Furthermore, new techniques and machinery are used to improve properties in addition to the methods mentioned above.

Ceramic applications in various industries

Due to their unique properties, such as durability, resistance to temperature, and chemical stability, ceramics has many applications in our daily lives. We all use ceramic dishes like porcelain, clay, and stone utensils to cook and serve food. These utensils are used as tableware because of their significant resistance to heat, durability, attractiveness, beauty, and hygiene. Our house and workplace were furnished with ceramics, and the bathroom, kitchen, and other rooms were fitted with ceramic tiles. Porcelain ceramics are available in various colors and figures, which makes them a popular choice for house decoration.

Ceramic materials have been used in art and decoration for thousands of years. Ceramic statues, flowerpots, and statues are popular decorative tools used in our houses. The aesthetic appeal of ceramic materials like chainware and clay makes them ideal for jewelry production. Among jewelry enthusiasts, ceramic marbles, earrings, and pendants are popular.

Ceramic materials like zirconia and silicon carbide are used in cutting tools like knives and scissors because of their high stiffness and resistance to corrosion. In the following, we mention some of their new and more advanced applications.

Ceramic applications in medicine

Ceramic materials have a vast usage in medicine due to biocompatibility, significant mechanical properties, and resistance to corrosion and abrasion. Some applications of ceramics in medicine are:

1- dental implant: ceramic materials such as zirconia and alumina are used in dental implants because of biocompatibility, resistance to abrasion, and durability. They also can provide a more natural appearance than metallic implants.

2- Joint replacement: Because of the resistance to corrosion and high biocompatibility, ceramic materials are used in joint replacement, such as hip and knee joints. Ceramic components can reduce inflammation and improve longevity compared to traditional metallic components.

4- Graft substitutes: Ceramics like hydroxyapatite and tricalcium phosphate are used as graft replacements because of their similar components to natural bones. These materials can boost bone growth and gradually be adsorbed to the body.

5- Surgery tools: Because of the resistance to corrosion and abrasion, ceramic materials are used in surgery tools. Also, they can be easily sterilized compared to traditional metallic tools.

6- Diagnostic and imaging apparatuses: Due to significant electrical and thermal properties

Ceramics are commonly used in diagnostic and imaging tools like X-ray tubes, ultrasound transducers, and dental imaging screens due to their electrical and thermal properties.

Ceramic application in the automobile industry

Because of significant mechanical properties like durability, rigidness, and resistance to corrosion, ceramic materials have a variety of applications in the automobile industry. Ceramic

brake linings are increasingly used in vehicles with high efficiency because of their high resistance to temperature and corrosion. Brake linings can tolerate high temperatures without losing the function of their brake and, as a result, improve safety and reliability.

Due to their durability, stiffness, and resistance to high corrosion, ceramic materials such as silicon nitride and alumina are used in parts of engines, including poppet valves, pistons, and turbochargers. Ceramic components of the engine can resist high temperatures, reduce corrosion and friction, and improve fuel efficiency.

Ceramic bearings and bushings can be used in the automobile industry due to their high corrosion resistance, low friction, and high durability. Compared to metallic bearings, ceramic bearings can handle higher speeds and loads and provide superior performance and durability. Ceramics are used in exhaust systems to reduce greenhouse gas emissions and improve fuel efficiency. Ceramic materials can be used as a thermal shield, catalyst transducer, and diesel particle filter.

Ceramic application in the construction industry

Ceramic materials are typically used in the construction industry due to their significant mechanical properties and resistance to corrosion and abrasion. Some of the applications of ceramics in the construction industry are:

1-Floor finish: Due to durability, resistance to moisture, chemicals, and corrosion, ceramic and tiles are usually used as floor finish materials in houses and commercial buildings and also as ceramic for the floor and facade of the building.

2- Roof materials and bricks: Ceramic materials like brick and roof tiles are used widely in the construction industry because of their durability, thermal insulation properties, and resistance to water, air, and chemicals.

3- Insulator materials: Ceramics are used as insulators in buildings to improve energy efficiency and reduce sound transmission. Ceramic insulator materials are usually used on walls, roofs, and floors.

4- Facade and coating: Ceramic materials are used as facade and coating materials in buildings. Ceramic facades and coating materials can provide thermal and acoustic insulation properties.

5- Cement and concrete additives: Ceramic materials such as fly ash and silica fume can be used as cement and concrete additives to improve strength, durability, and efficiency. Ceramic additives can reduce the environmental impacts of producing cement and concrete.