Ceramics PDF

Traditional Ceramics diTerent orientations. This structure aTects mechanical strength and brittleness. > Keramikos – originates from the Greek word “Keramos” meaning “potter’s clay” or “pottery...

Traditional Ceramics diTerent orientations. This structure aTects mechanical strength and brittleness. > Keramikos – originates from the Greek word “Keramos” meaning “potter’s clay” or “pottery”. Grain Boundaries: The interfaces between diTerent crystal grains can act as stress > Pottery making- one of Egypt's most ancient human concentrators, influencing failure modes. industries from about 15000 BC. The structural characteristics lead to several > Basic raw materials for making classic or triaxial notable properties: ceramic products are clay, feldspar, and sand. High Hardness and Strength: Due to strong What are ceramics? Ionic and covalent bonds. A diverse group of materials defined primarily by their Brittleness: Limited ability to deform inorganic, non-metallic nature. They are typically plastically before fracturing. composed of a combination of metal and non-metal compounds that have been shaped and hardened Chemical Stability: Resistance to corrosion through high-temperature processing. and chemical reactions. Ceramic structures - are defined by their atomic Mechanical Properties of Ceramics arrangement and bonding types, which directly influence their properties. High Hardness - Ceramics are extremely hard, making them resistant to scratching and Ceramics have two types of bonds (Ionic bonds and wear. Covalent bonds ) Brittleness - They tend to fracture easily under Ionic bonds - This type of bonding contributes to the stress, especially in tension, due to limited hardness and high melting points of ceramics. plastic deformation. Covalent Bonds - This type of bonding leads to High Compressive Strength - While they are directional bonding which influences the crystal weak in tension, ceramics can withstand very structure and mechanical properties of ceramics. high compressive loads. Ceramics typically exhibit a crystalline structure, Low Ductility - Ceramics are not ductile and which can be categorized into various types based on cannot stretch or deform before breaking. how atoms are arranged Low Toughness - Ceramics have low o Cubic Structures: Common in toughness, meaning they are prone to materials like sodium chloride (NaCl) cracking under sudden impact. and magnesia (MgO), where each ion is surrounded by six oppositely High StiIness - They have a high Young's charged ions, allowing for eTicient modulus, meaning they are rigid and do not packing and stability. deform easily under stress. o Fluorite Structures: Found in Thermal Properties of Ceramics materials such as calcium fluoride High Melting Point - Most ceramics have very (CaF₂), where the arrangement allows high melting points, typically above 1000°C, for unique properties like with some going beyond 2000°C. This makes superconductivity in certain ceramics. them ideal for applications in high- The microstructure of ceramics consists of multiple temperature environments. grains and phases are: Low Thermal Conductivity - Ceramics Polycrystalline Materials: Composed of generally have low thermal conductivity, many small crystals or grains, each with meaning they do not easily transfer heat. This makes them excellent insulators. For  example, materials like alumina and zirconia Refractory Materials are used in applications requiring heat Ø Structure: High-temperature ceramics made resistance, such as thermal barriers. from materials like alumina, silica, and Thermal Expansion - Ceramics have magnesia. relatively low thermal expansion coeTicients Ø Properties: High melting points, resistance to compared to metals, meaning they expand thermal shock and chemical attack, and and contract less with temperature changes. durability in extreme environments. This property helps them maintain structural Ø Applications: Furnace linings, kiln integrity under varying thermal conditions. components, and high-temperature industrial processes. Thermal Shock Resistance - Ceramics tend to be brittle and can experience cracking when Ceramic Product Manufacturing subjected to rapid temperature changes, known as thermal shock. However, certain 1. Porcelain - Is a type of ceramic material ceramics like silicon carbide and zirconia can known for its strength, whiteness, and withstand thermal shocks better than others. translucence. It is made by heating a mixture of materials, primarily including kaolin (a fine Heat Capacity - Ceramics generally have white clay), at very high temperatures, lower specific heat capacities compared to typically between 1200°C and 1400°C (2192°F metals, meaning they require less energy to to 2552°F). raise their temperature. However, this depends on the specific type of ceramic Two main types of porcelain: material. o Hard-paste porcelain Refractoriness - Ceramics are often used in o Soft-paste porcelain refractory applications due to their ability to 2. Bricks - are rectangular blocks used primarily retain strength and stability at high as building materials in construction. They are temperatures, making them suitable for made from various materials, but the most furnace linings, kilns, and other high- common type is clay brick, which is formed temperature industrial processes. from clay and hardened by firing in a kiln. Bricks have been used for thousands of years Distinct Character and Uses of Ceramics due to their durability, strength, and fire- resistant properties. Glass (Ceramic Types of Bricks: Ø Structure: Amorphous, non-crystalline. Ø Properties: Transparent, brittle, hard, good Clay Bricks: Made from natural clay electrical insulator, chemically inert, and low and fired in a kiln, these are the most thermal conductivity. traditional type of bricks. They are Ø Applications: Windows, containers, optical strong, long-lasting, and commonly fibers, and laboratory glassware. used for walls, pavements, and building exteriors. Clay Products Concrete Bricks: Made from cement Ø Structure: Composed of natural clay and aggregate (sand, gravel, or minerals; crystalline or semi-crystalline after crushed stone), these are often used firing. for low-cost construction, walls, and Ø Properties: High plasticity when wet, durable foundations. after firing, porous unless glazed, good heat and electrical insulation. Fly Ash Bricks: Made from fly ash, a Ø Applications: Bricks, tiles, pottery, porcelain, by-product of coal combustion, along and sanitary ware.  with cement or lime, these bricks are Key Properties of Glass: lightweight and eco-friendly. Transparency: Glass allows light to pass Engineering Bricks: These are through, which makes it ideal for windows, specially made for strength, density, lenses, and lighting. and water resistance, often used for Brittleness: Though it is strong in structural purposes like load-bearing compression, glass is brittle and breaks walls. easily under tension or impact. Fire Bricks (Refractory Bricks): Non-Porous: Glass does not absorb Designed to withstand high liquids or gases, making it useful for temperatures, they are used in kilns, containers and lab equipment. fireplaces, and other areas exposed to heat. Thermal Stability: Certain types of glass (like borosilicate) can withstand high 3. Pottery - Is the craft and art of creating objects temperatures, making it useful for out of clay, which are then hardened by heat cookware and laboratory instruments. through a process known as firing. Chemical Resistance: Glass is inert to Pottery Techniques: most chemicals, which makes it ideal for Hand-building - A traditional method storage of liquids and for chemical where clay is shaped by hand, using apparatus. techniques like pinching, coiling, or 5. Ceramic tiles - are commonly used for slab construction. flooring, walls, and decorative purposes. The Wheel-throwing - Involves spinning manufacturing process typically involves Raw the clay on a potter’s wheel and Material such as clay, feldspar, and silica are shaping it with the hands and tools. mixed, ground, and blended. The prepared This is a popular method for creating mixture is shaped using a process like dry symmetrical forms like bowls and pressing or extrusion. After that, Tiles are dried vases. to remove moisture content, preventing cracks during firing. Ceramic tiles are fired in Molding - Clay is pressed into a mold kilns at high temperatures (up to 1200°C), to to achieve a specific shape, solidify their shape. commonly used in mass production. 6. Ceramic diamonds - also known as synthetic Glazing - A layer of glaze (liquid glass) diamonds, are commonly used in cutting tools is applied to pottery pieces before a and high-precision instruments. Unlike second firing to make them waterproof traditional ceramic materials, ceramic and to add color and texture. diamonds are carbon-based, made through chemical vapor deposition (CVD) or high- Firing - The process of heating the pressure, high-temperature (HPHT) methods shaped clay objects in a kiln, which 7. Ceramic disk brakes - used in high- transforms the clay into a hard, performance vehicles, are valued for their durable material. ability to withstand high temperatures and 4. Glass - Is a hard, brittle material that is oTer improved braking performance. typically transparent or translucent and is Manufacturing ceramics made by melting sand (silica), soda ash (sodium carbonate), and limestone at high Ceramic disk brakes need material temperatures, then cooling the mixture so that such as Silicon carbide, graphite, and it solidifies without crystallizing. other ceramic fibers are mixed to create a heat-resistant composite. The  mixture is formed into the shape of a 13. Whiteware brake disc through a molding or - Is the generic term for ceramic products which pressing process. The shaped material are usually white and of fine texture. is fired in a kiln at very high - Based on selected grades of clay blended together temperatures (up to 1700°C), allowing with varying amounts of fluxes and heated to a the ceramic particles to bond together. moderately high temperature in a kiln (1200 - 1500°C). 14. Arthenware To further improve strength, carbon - sometimes called semivitreous dinnerware fibers or metal may be added to the - porous and nontranslucent with a soft glaze. brake discs. The surface of the brakes Chinaware may undergo additional treatments to - is vitrified translucent ware with a minimum enhance friction or reduce wear. Glaze that resists abrasion to a degree 8. Ceramic knives are popular for their - used for nontechnical purposes. sharpness, light weight, and resistance to 15. Sanitary ware rust. These knives are typically made from - formerly made from clay and was usually zirconium oxide (zirconia) Porous. Ø Zirconium dioxide powder is mixed - vitreous composition is presently used. with binders to create a malleable - prefired and sized vitreous grog is sometimes material. The mixture is pressed into Included with the triaxial composition. 16. Stoneware the desired knife shape. The formed - one of the oldest of ceramic wares, was in use knife blade is fired in a kiln at Long before porcelain was developed. temperatures over 1500°C. This - crude porcelain process hardens the blade and gives it - not so carefully fabricated from raw material of a dense, durable structure. The A poorer grade. ceramic knife is ground and sharpened using diamond abrasives, as ceramics are much harder than steel. 9. Ceramic Toilets: Made from vitreous China, a smooth, durable, and non-porous ceramic, making them easy to clean and resistant to stains. They’re long-lasting, hygienic, and low- maintenance bathroom fixtures. 10. Ceramic Figurines: Small decorative objects shaped from clay and hardened in a kiln. Often painted or glazed, they represent artistic forms and are popular as collectibles and elegant home decor. 11. Piezoelectric Ceramics: Special ceramics like lead zirconate titanate (PZT) that generate electricity when compressed. They’re used in sensors, actuators, and devices that convert mechanical to electrical energy, crucial for precision technology. 12. Refractories: High-temperature-resistant ceramics used in industrial furnaces and kilns. Made from materials like alumina or silica, they withstand intense heat without degrading, essential for efficient high- temperature operations.