Ceramics: Types, Properties, and Applications

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What are the types of ceramics?

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Ceramics can be classified into:

• Traditional Ceramics (e.g. porcelain, tiles)

• Engineering Ceramics (e.g. alumina, zirconia)

• Glass

• Glass Ceramics (e.g. cooktops)

• Electronic Ceramics (e.g. barium titanate)

• Cements (e.g. Portland cement)

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What is ionic bonding in ceramics?

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Transfer of electrons, resulting in rigid and brittle structures.

Ionic bonding in ceramics occurs when electrons are transferred from a metal atom to a non-metal atom, forming positive and negative ions. These ions are held together by strong electrostatic forces, creating a rigid and stable lattice structure. This type of bonding is common in ceramics like alumina (Al₂O₃) and contributes to properties such as high hardness, high melting point, electrical insulation, and brittleness. Because the ions are tightly bound, ceramics with ionic bonding do not conduct electricity and tend to fracture under tensile stress.

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What is covalent bonding in ceramics?

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Shared electrons, leading to strong and directional bonds.

Covalent bonding in ceramics occurs when atoms share electrons in fixed, directional bonds. This creates a very strong and rigid structure that resists deformation, contributing to the high hardness and stiffness (high Young’s Modulus) of ceramics.

An example is silicon carbide (SiC), which has strong covalent bonds and is used in engineering cutting tools and high-temperature components. These directional bonds make the material ideal for precision machining, as it maintains shape under stress but is also brittle and can crack if overloaded.

Key Concept: Covalent bonding explains why some ceramics are strong, stiff, and wear-resistant — essential for aeronautical, transport, and manufacturing applications.

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Why are ceramics insulators?

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They have no free electrons, which prevents electrical conductivity.

Ceramics are electrical insulators because they lack free electrons. In metals, free electrons move easily and carry electric current. But in ceramics, the electrons are tightly bound in ionic or covalent bonds and cannot move freely.

This means electricity cannot flow through the material, making ceramics ideal for insulators in electrical and telecommunications systems, such as porcelain insulators on power lines or ceramic components in circuit boards.

Summary: Ceramics are insulators because they have no free-moving electrons to carry current — this makes them useful in engineering applications where electrical insulation is required.

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What is vitrification in ceramics?

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The formation of a glassy phase during firing that strengthens the structure.

Vitrification is the stage in ceramic firing where, at temperatures above 900°C, a glassy phase forms and mullite crystals grow within the material. This process bonds the ceramic particles together, reducing porosity and increasing strength and density.

This is essential in engineering applications where durability is required — such as ceramic tiles & insulators. Without vitrification, ceramics would remain weak and porous.

Summary: Vitrification strengthens ceramics by forming a glassy phase and binding particles together, making them hard, dense, and suitable for civil and electrical engineering applications.

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What is the property of ceramics that resists wear?

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High hardness.

The property of ceramics that resists wear is high hardness. This means ceramics can withstand scratching, surface abrasion, and mechanical contact without being easily damaged.

Ceramics have high hardness because of their strong ionic and covalent bonds, which hold the atoms rigidly in place in a crystalline structure. This bonding resists the movement of atoms under force, making the material very hard and wear-resistant.

This is especially important in engineering applications such as:

• Cutting tools (e.g. silicon carbide tips),

• Brake pads in high-performance vehicles,

• Pump seals and bearings exposed to friction.

Summary: Ceramics are hard because of their strong atomic bonds and rigid structure. This makes them ideal for resisting wear in demanding engineering environments.

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What is the tensile strength of ceramics?

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Low tensile strength; they fail under pulling forces.

Ceramics have low tensile strength, meaning they fail easily under pulling or stretching forces. This is because ceramics are brittle — they do not deform plastically and instead fracture suddenly when placed under tension.

This weakness is due to the rigid ionic and covalent bonding in ceramics, which holds atoms in fixed positions. While these bonds give ceramics high hardness and compressive strength, they cannot stretch or bend before breaking.

Example: In engineering, ceramics are rarely used in components under tensile loads. Instead, they are used in compression-heavy environments, like tiles, bricks, or spark plug insulators, where their low tensile strength is not a disadvantage.

Summary: Ceramics break under tension due to their brittle structure and rigid bonding — giving them low tensile strength.

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What is the significance of high Young’s Modulus in ceramics?

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It indicates stiffness and resistance to deformation.

A high Young’s Modulus in ceramics means the material is very stiff and resists deformation under applied force. This is due to the strong ionic and covalent bonds holding atoms in place in a rigid structure.

This stiffness makes ceramics ideal for precision components that must maintain shape under load, such as cutting tools, engine components, or turbine blade coatings.

However, while ceramics resist bending, they are also brittle — they don’t absorb much energy before breaking.

Summary: High Young’s Modulus means ceramics are stiff and resist bending — useful in engineering where rigidity is needed, but designers must also consider their brittleness.

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What is the drying stage in ceramic manufacturing?

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Removes surface water at temperatures ≤150°C.

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What happens during the dehydration stage?

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Chemically bound water is removed at 300–700°C.