Introduction to Ceramics 141

abrasives

A material consisting of hard ceramic particles used to wear away or remove workpiece material. Abrasives are used in operations designed to clean, polish, or otherwise prepare the surface of a part.

acidic

Sour, reactive with bases, and able to promote certain chemical reactions. Acidic refractories can react quickly and become corroded by a basic substance.

additives

A substance added to another substance or material to improve its chemical and physical properties. Additives are used early in ceramic processing as binders or hardening agents.

advanced ceramic

A material or product whose chemical compositions have been engineered to exhibit unique and superior physical and mechanical properties. Advanced ceramics often have simple chemical compositions, but they are complex to manufacture.

advanced functional ceramics

A class of advanced ceramics that are characterized as having enhanced physical properties. Advanced functional ceramics are mainly used in electronics.

advanced structural ceramics

A class of advanced ceramics that demonstrate enhanced mechanical properties when subjected to extreme forces. Advanced structural ceramics make superior cutting tools for metal manufacturing.

alumina

A ceramic compound of aluminum and oxygen. Alumina is one of the main materials used in advanced ceramics.

amorphous

Lacking a long-range order that is characteristic of a crystalline structure. Glasses are most widely known for having an amorphous, or non-crystalline, structure.

atomic structure

The organization of atoms in a substance. Atomic structures determine the physical and mechanical characteristics of a substance.

atoms

The smallest distinguishable unit of a material that maintains that material's characteristics. Atoms consist of protons, neutrons, and electrons.

basic

Slippery to the touch, bitter tasting, reactive with acids, and able to promote certain chemical reactions. Basic refractories exhibit resistance to iron oxides.

bearings

A friction-reducing device that allows machine parts to move together without excess wear or friction. Bearings made with ceramics possess greater hardness and require less lubrication.

bioceramics

Ceramic materials whose composition is compatible with the human body. Some bioceramics can even be absorbed into the body in some instances.

biocompatibility

A material's ability to be used in living tissue without being toxic or causing injury. Biocompatibility is an important property for materials used in medical applications.

blowing

A technique or process used for manufacturing glass by inflating molten glass into a bubble using a pipe or tube. Glassblowing is used in the production of bottles, containers, and decorative pieces.

bonding agent

The material that holds abrasive grains together in an abrasive. Bonding agents may consist of rubber, metal, or other material.

brittle

Hard and more likely to break instead of bend when subjected to force or pressure. Brittle materials include most traditional ceramics.

capacitors

A device used to store an electric charge. Capacitors consist of one or more pairs of conductors separated by an insulator.

carbides

A common ceramic cutting tool material used to make cutting tools for manufacturing. Carbides are very hard and wear resistant.

catalytic converters

An exhaust component that controls and converts toxic gases into less harmful substances. Catalytic convertors are central to emission control in the automotive industry.

caustic

Capable of destroying a material by chemical action. Caustic substances usually do not chemically deteriorate ceramics.

ceramics

An inorganic material that consists of both metallic and nonmetallic atoms held together by strong bonds. Ceramics are used in manufacturing due to their corrosion resistance and durability.

cermet

A composite material made from ceramic and sintered metal. Cermets have high temperature resistance and high hardness.

chemically inert

A material's ability to not react chemically. Plastics and ceramics are both chemically inert and are used when dealing with corrosive chemicals.

chromite

A chemical compound consisting of iron chromium oxide. Chromite is a neutral substance used in refractories with a high resistance to corrosion and thermal changes.

clay

A common, naturally occurring ceramic material that is easily shaped and solidifies when dried. Clay is the basis for many ceramic products.

coarse

Rough or harsh in texture. Coarse grains remove the most surface material.

composites

Material composed of two or more unlike materials that are bonded together without losing their individual properties or characteristics. Composites generally consist of materials layered or suspended in one another.

compressive strength

A material's ability to resist forces that attempt to reduce it in size. A material that withstands fracturing under compressive stress has high compressive strength.

conductors

A material or element that allows free movement of electrons and therefore allows easy transfer of heat. Conductors require an insulating material such as a ceramic or plastic.

corrosion

A process by which a material gradually degrades or wears away. Corrosion typically occurs when a material is exposed to atmosphere, moisture, or other substances.

covalent bonds

A chemical bond formed between atoms by the sharing of electron pairs. Covalent bonds are a strong type of primary bond that forms in a ceramic.

crucibles

A ceramic container in which substances can be melted at high temperatures. Crucibles used in metallurgy are made of refractories.

crystalline structure

A structure consisting of crystals that are formed by repeating patterns of atoms. Crystalline structures are found in both metals and ceramics.

cutting tools

A device with sharp edges used to cut a material. Ceramic cutting tools are often more effective at removing workpiece material than metal cutting tools.

defects

A type of irregularity that exists within a material's atomic structure. Defects play a role in determining the properties of a ceramic.

deform

To change or distort an object's shape. Deformed ceramics have permanently lost their original shape.

degradation

The process of the weakening or diminishing of a substance due to environmental factors. Degradation of a ceramic is not typical.

densifies

Making a material more compact. Heat treatment densifies a ceramic green body.

diamond

Naturally occurring or manufactured stone made of crystalline carbon that is used as an abrasive. Diamond is the hardest available material.

dielectric

Having little or no ability to conduct electricity. Dielectric materials are used to separate conductors and are non-metallic.

durability

The ability of materials to withstand extended exposure to environmental wear and mechanical forces. Ceramics tend to have good durability.

electrical conductivity

A material's ability to act as a medium for conveying electricity. Electrical conductivity depends on the modification of a ceramic's structure.

electrical insulators

A material or element that has little electrical conductivity and high resistance to electrical charges. Most insulators are plastics and ceramics.

electroceramics

Ceramic material that possesses the ability to perform an electrical function for a particular application. Electroceramic applications vary from conductors to circuitry in the medical field to quartz watches.

elements

A basic form of a substance that cannot be further subdivided by chemical methods. Elements include substances such as oxygen, hydrogen, and carbon.

exhaust

Used gas or vapor expelled from an engine. Exhaust is filtered through a catalytic converter with ceramic filters.

extruded

Shaped by forcing through a die. Extruded glass is an alternative process of shaping compared to conventional methods of blowing or molding.

feldspar

A mineral commonly used in glassmaking and ceramics to improve a material's hardness and durability. Feldspar is commonly used to lower the melting temperature during ceramic processing.

ferrites

A ceramic compound that contains large amounts of iron oxide. Ferrites are often used as a substitute for metallic-based magnets.

fiber optic cable

Thin, flexible glass or plastic optical fibers that transmit light instead of electricity. Fiber optic cable is a more advanced alternative to metal wiring for data communication.

fiberglass

A lightweight and strong material composed of a matrix of fine glass fibers weaved into a mesh. Fiberglass material is used as insulation in many industrial applications.

fine

Less rough or harsh in texture. Fine grains remove less surface material and are often used for polishing or finishing.

fire bricks

A block of refractory material that can withstand high temperatures. Fire bricks are used to line furnaces, kilns, and fireplaces.

firing

The heating of ceramic materials at elevated temperatures. Firing helps to solidify the material and improve its strength.

float glass

A sheet of glass made by floating molten glass on a bed of molten metal, typically tin, giving the glass uniform thickness and a flat surface. Float glass is used in the manufacturing of windows.

fracture

The act or process of cracking or breaking under stress. Ceramics tend to fracture along grain boundaries.

friability

An abrasive grain's ability to fracture and self-sharpen under stress. Low friability in an abrasive could result in faulty grinding.

friction

A force that resists motion created by the contact of components in an operation. Increased friction raises the heat in an operation and can cause damage.

fuel cells

A device that uses gas to convert chemical energy into electrical energy. Fuel cells are potentially very efficient power sources.

fuel injectors

A pump and valve mechanism that sprays liquid fuel into the cylinder of an engine. Fuel injectors contain ceramic parts.

gaskets

A shaped material that seals the junction between two surfaces in a device. Gaskets made with ceramic magnets are used in household appliances.

glass

A transparent material made from silica and other compounds. Glass is the most widely used ceramic.

glazing

An impervious layer or coating of a vitreous substance that is fused to a ceramic during firing. Glazing can be colorful, decorative, or functional.

grain boundaries

The place where two grains meet. Grain boundaries determine the microstructure of a ceramic.

grain size

The measurement of small crystals in a microstructure. Grain size determines the strength of a material.

grains

Small particles or crystals that form the structure of a ceramic material. Grain arrangement contributes to a ceramic's properties.

green body

A shaped but unfired ceramic part or product. A green body lacks the desired mechanical properties brought by heat treatment.

grinding

The use of an abrasive to cut the surface of a workpiece and change its shape. Grinding operations commonly use abrasive grains bonded into a wheel shape.

grinding wheels

Abrasive grains bonded into a wheel shape used to cut the surface of a workpiece and change its shape. Grinding wheels are commonly used in manufacturing processes.

hardness

A material's ability to resist penetration. An increase in hardness generally leads to a decrease in toughness, or ability to withstand fracture.

heat treatment

A controlled heating and cooling process used to change the structure of a material and alter its physical and mechanical properties. Heat treatment is often used to adjust a material's hardness.

heating elements

A device that increases the temperature of a component when activated. Ceramic heating elements are sometimes made of graphite silicon carbide.

impurities

An unwanted substance or particle that reduces the quality of a material. Materials can be refined to eliminate the presence of impurities.

infrared

IR. Invisible ray of light energy emitted by heated objects. Infrared light can be used to capture a visual representation of an object's thermal signature.

inorganic compounds

A material derived from nonliving substances such as minerals. Inorganic compounds usually do not contain carbon and are often classified in terms of the elements or groups of elements that they contain.

insulators

A material that reduces the transfer of heat. Insulators include polymers and ceramics.

ionic bonds

A type of chemical bond that occurs when one atom borrows one or more electrons from another atom. Ionic bonds form between oppositely charged ions.

iron oxide

A chemical compound containing iron and oxygen. Iron oxide is found in ceramic magnets and cosmetics.

lasers

A device that generates an intense beam of light that can be precisely aimed and controlled. Lasers are used for a wide array of manufacturing processes.

lenses

A curved, transparent material used to concentrate or disperse light rays. A lens can be used in numerous optical instruments such as lasers, eye glasses, and telescopes.

lime

A caustic, highly infusible material derived from limestome. Lime is used in the glass-making process to purify and increase durability and wear resistance.

long-range

The predictable arrangement of atoms over a long distance. Long-range order is characteristic of atomic crystalline structures.

magnesium oxide

A white substance used in the manufacturing of high-temperature refractory materials. Magnesium oxide is used for a variety of refractory applications.

magnetism

The power of attraction and repulsion produced by electrical currents that exists in materials. Magnetism most often occurs between metals but can exist within certain types of ceramics.

magnetite

A naturally occurring magnetic ceramic material. Magnetite is the oldest known ferrite and was used for needles in compasses.

mass

The amount of matter in an object. Mass gives an object weight when it is acted upon by gravity.

mechanical properties

A characteristic that describes how a material reacts when subjected to a force that attempts to stretch, compress, bend, dent, scratch, or break it. A material's mechanical properties are usually tested under given loads.

metallurgy

The technique or science of separating metals from their ores, creating alloys, and working or heating them so as to give them certain shapes or properties. Metallurgy uses ceramic lined furnaces and crucibles.

metals

A naturally occurring material that is electrically and thermally conductive. Metals include copper, iron, nickel, and lead.

microstructure

The shape and alignment of microscopic components in a material. Microstructure strongly influences the properties of a material.

molten

Fused or liquified by heat. Glass is one of the few ceramics that can be heated to a molten state.

neutral

Not reacting with an acid or a base. Neutral refractories may be used in a variety of environmental conditions.

nitrides

A chemical compound containing nitrogen, an inert gas. Nitride-based ceramics exhibit superior properties.

non-crystalline

Lacking a long-range order that is characteristic of a crystalline structure. Glasses are most widely known for having a non-crystalline, or amorphous, structure.

optical

Relating to or utilizing light. Glass is manufactured as windows for its optical properties.

oxides

A chemical compound containing oxygen and one other element. Oxides are known to lend durability and high operating temperatures to a ceramic.

petrochemical

Related to petroleum or natural gas. Petrochemical products include plastics, soap, solvents, drugs, pesticides, synthetic fibers, and rubbers.

physical properties

A characteristic that describes a material's volumetric, thermal, electrical, and magnetic characteristics. Physical properties are a collection of characteristics that describe how a material responds to forces other than mechanical forces.

piezoelectric

Having the ability to generate an electrical charge when subjected to mechanical stresses. Many piezoelectric devices are made of the same ceramic materials as capacitor dielectrics.

plastics

A lightweight polymer material that has high corrosion resistance, a high strength-to-weight ratio, and a low melting point. Most plastics are easily shaped and formed.

pores

An empty space between the grains and bond in a material. Pores decrease in size when a ceramic is fired.

porosity

A discontinuity characterized by the appearance of tiny spaces or voids. Porosity is often determined by the number of small voids within a ceramic material.

refractories

Ceramics with remarkable resistance to high temperatures, corrosion, and abrasive environments. Refractories are used to line industrial furnaces.

reinforcements

An additive material that provides strength, stiffness, and the ability to carry a load. Reinforcements are commonly used in ceramic and composite manufacturing.

sapphire

A precious gemstone from a form of alumina. Sapphire is used as an alternative to glass because of its extreme durability and ability to be transparent.

shaping

A manufacturing process that mixes raw materials and forms them into complex shapes. In ceramics, shaping can involve powders or slurry.

shear strength

A material's ability to resist forces that attempt to cause the internal structure to slide against itself and separate. Shear strength is the amount of shear force a material can withstand before fracturing.

short-range

The arrangement of atoms over a short distance. Short-range order is characteristic of amorphous structures.

silica

A ceramic compound that is commonly used to make a wide variety of glasses. Silica is also used in refractory materials.

silicon carbide

A colorless ceramic compound of silicon and carbon. Silicon carbide abrasives are brittle and used in high-temperature applications.

silicon nitride

A ceramic compound of silicon and nitrogen. Silicon nitride is highly heat resistant.

sintering

A material manufacturing process that heats pressed and shaped powdered materials to create a solid shape. Sintering can be used to make both metal and ceramic products.

slurry

A thick mixture of liquid and suspended solids. A slurry is used in the forming process of traditional ceramics.

sodium carbonate

A nontoxic, noncorrosive, nonconductive extinguishing agent. Sodium carbonate reduces the melting temperature in the production of glass.

sonar

A method for detecting and locating objects, especially underwater, by means of sound waves sent out to be reflected by the objects. Sonar uses piezoelectrics to convert electricity into sound.

spark plugs

A part that fits into an internal combustion engine and carries two electrodes separated by an air gap across which the current from the ignition system discharges to form the spark for combustion. Spark plugs contain sintered alumina insulators.

strength

A material's ability to resist forces that attempt to break or deform it. A material exhibits tensile, compressive, or shear strength, depending on the deforming force.

stress

A force that attempts to deform an object. Stress typically causes a ceramic to fracture or break.

structural ceramics

A type of ceramic that possesses high load-bearing strength. Structural ceramics are often used for construction materials.

substrates

A surface or medium that serves as a base for other materials or components. Ceramic substrates are the bases on which microscopic electronic components and their connections are built.

synthesized

Formed by combining parts or elements. Synthesized ceramic compounds combine the desired properties of many substances into one material.

tensile strength

A material's ability to resist forces that attempt to pull it apart or stretch it. Materials with high tensile strength tend to deform, bend, or stretch before breaking.

thermal conductivity

A material's ability to conduct heat. Thermal conductivity depends on the material's structure and temperature.

thermal properties

The characteristics of a material that determine how it reacts when it is subjected to excessive heat or heat fluctuations over time. The thermal properties of ceramics make them good insulators.

thermal resistance

A material's ability to remain unchanged due to exposure to extremely high or low temperatures. Thermal resistance allows materials to maintain their properties and integrity even at extreme temperatures.

thermochemical inertness

A material's ability to be nonreactive to chemicals or temperature fluctuation. Thermochemical inertness is a priority in aerospace.

toughness

A material's ability to absorb energy without breaking or fracturing. Toughness is a key property that determines a material's ability to withstand a sudden stress.

traditional ceramic

A clay- or silica-based material developed through a conventional process of shaping and firing. Traditional ceramics are typically made in large quantities by efficient, inexpensive methods.

turbine

A machine that uses the motion or energy of moving water or wind to produce circular movement. A turbine made with ceramic is lightweight and performs well under high temperatures.

ultrasound

A method of producing images of the inside of the body or an object by using a machine that produces sound waves too high to be heard. Ultrasound is produced by piezoelectric vibration.

ultraviolet

UV. A potentially harmful wavelength of light that is below, or shorter, than violet on the light spectrum. Certain glasses can protect from ultraviolet light, like that in welding helmets.

viscosity

A property that describes a fluid's resistance to flow. The viscosity of a fluid decreases as temperature increases.

viscous

Having a high resistance to flow. Viscous glass has been heated to a liquid, at which point it can be shaped or molded.

vitreous

Characterized by a material's lack of porosity or impermeability. Certain ceramics such as glass and whiteware china are vitreous.

voltage

A measure of electrical pressure or potential. Voltage is measured in volts (V).

whiteware

A class of ceramics made from clay that is less porous, has fewer impurities, and more functionality than other clay ceramics. Porcelain, a type of whiteware, is used for tableware, plumbing fixtures, and insulators.

workpiece

A material being machined or undergoing another type of processing. Workpieces can be shaped by processes such as cutting, welding, and grinding.

zirconia

A ceramic compound of zirconium and oxygen. Zirconia is often used in advanced ceramics for its extreme hardness.