Introduction and General Properties of Ceramics
- Ceramic materials are hard, brittle, heat-resistant, and corrosion-resistant.
- They are made by shaping and firing inorganic, nonmetallic materials at high temperatures.
- Examples of ceramics include earthenware, porcelain, and brick.
- Ceramics can withstand high temperatures ranging from 1,000°C to 1,600°C (1,800°F to 3,000°F).
- They are generally strong in compression but weak in shearing and tension.
- Most fired ceramics are either vitrified or semi-vitrified.
- Ceramic materials have varying crystallinity and electron composition.
- They are good thermal and electrical insulators.
- General properties of ceramics include high melting temperature, high hardness, poor conductivity, and chemical resistance.
- Exceptions to these properties include piezoelectric ceramics and superconductive ceramics.
Composites, Processing, and History of Ceramics
- Composites like fiberglass and carbon fiber are not considered ceramics.
- Highly oriented crystalline ceramics have limited processing options.
- Ceramic forming techniques include shaping by hand, slip casting, and injection molding.
- Glass can be converted into a semi-crystalline material known as glass-ceramic.
- Traditional ceramic raw materials include clay minerals, while advanced ceramics include silicon carbide and tungsten carbide.
- The earliest known ceramics are Gravettian figurines dating back to 29,000–25,000 BC.
- Humans have been making ceramics for at least 26,000 years.
- Regular pottery became common around 10,000 years ago.
- The Corded Ware culture decorated their pottery with rope patterns.
- The invention of the wheel improved pottery production.
Archaeology and Analysis of Ceramics
- Ceramic artifacts are important for understanding past cultures, technology, and behavior.
- They are commonly found at archaeological sites as small fragments called sherds.
- Traditional analysis involves sorting artifacts based on style, composition, and manufacturing.
- Technical analysis examines the composition of ceramics to determine their source and manufacturing site.
- Stylistic changes in ceramics can help establish chronology and distinct diagnostic groups.
Mechanical and Electrical Properties of Ceramics
- Physical properties of ceramics are determined by their crystalline structure and chemical composition.
- Solid-state chemistry reveals the connection between microstructure and properties, such as density variations and grain size distribution.
- Ceramic properties include mechanical strength, hardness, toughness, dielectric constant, and optical properties.
- Ceramography is the study of ceramic microstructures, which are examined on a similar scale as nanotechnology.
- Fracture mechanics is used to improve the mechanical performance of ceramics.
- Ceramic materials have limited slip systems for dislocations, causing slow deformation.
- Some ceramics, such as zinc oxide, exhibit semiconductor behavior.
- Varistors are ceramics that exhibit a sharp drop in resistance at a certain voltage threshold.
- Piezoelectric ceramics can convert mechanical stress into electrical signals and vice versa.
- Ceramics can exhibit ferroelectric behavior, where they have a spontaneous electric polarization.
- Some ceramics show high-temperature superconductivity under specific conditions.
Applications of Ceramics
- High-frequency loudspeakers, transducers, and motion sensors utilize the piezoelectric response of certain ceramics.
- Ferroelectric materials are used in ferroelectric RAM and memory devices.
- Ceramics with positive thermal coefficient are used as self-controlled heating elements and in ceramic capacitors.
- Optically transparent ceramics have applications in digital image enhancement, fiber optics, and optical communication systems.
- Ceramic brake disks offer high resistance to brake fade in vehicles.
- Ceramic plates are used in ballistic armored vests and for cockpit protection in military aircraft.
- Ceramic ball bearings have lower wear, longer lifespan, and resistance to corrosion compared to steel bearings.
- Ceramics have the potential to be used in engines for weight reduction, higher operating temperatures, and improved efficiency.
- Synthetic hydroxyapatite, a ceramic material, is used in dental implants and synthetic bones.
- Ceramics are being experimented with in gas turbine engines for improved efficiency and performance.
A ceramic is any of the various hard, brittle, heat-resistant, and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain, and brick.
The earliest ceramics made by humans were pottery objects (pots, vessels, or vases) or figurines made from clay, either by itself or mixed with other materials like silica, hardened and sintered in fire. Later, ceramics were glazed and fired to create smooth, colored surfaces, decreasing porosity through the use of glassy, amorphous ceramic coatings on top of the crystalline ceramic substrates. Ceramics now include domestic, industrial, and building products, as well as a wide range of materials developed for use in advanced ceramic engineering, such as semiconductors.
The word ceramic comes from the Ancient Greek word κεραμικός (keramikós), meaning "of or for pottery" (from κέραμος (kéramos) 'potter's clay, tile, pottery'). The earliest known mention of the root ceram- is the Mycenaean Greek ke-ra-me-we, workers of ceramic, written in Linear B syllabic script. The word ceramic can be used as an adjective to describe a material, product, or process, or it may be used as a noun, either singular or, more commonly, as the plural noun ceramics.