Ceramics Flashcards
An inorganic non-metallic solid made up of either metal or non-metal compounds that have been shaped and then hardened by heating to high temperatures.
ceramic
The term ceramic comes from the Greek word ______, which means “burnt stuff”.
keramikos
One of the atoms (the metal) transfers electrons to the other atom
(the nonmetal), thus becoming positively charged (cation), whereas the nonmetal becomes negatively charged (anion). The two ions having opposite charges attract each other with a strong
electrostatic force.
ionic bond
Nowadays this term has a more expansive
meaning and includes materials like glass, advanced ceramics and some cement systems as well.
ceramic
Occurs between two nonmetals, in other words two atoms that
have similar electronegativity, and involves the sharing of electron pairs between the two atoms.
covalent bonding
Bonds of ceramics that are responsible for many unique properties of these materials, such as high hardness, high melting points, low thermal expansion, and good chemical resistance, but also for some undesirable characteristics, foremost being brittleness, which leads to fractures unless the material is toughened by reinforcing agents or by other means.
ionic and covalent
Some of the common ceramic materials are those in which there are equal numbers of cations and anions. These are often referred to as
AX compounds
Perhaps the most common AX crystal structure is the
sodium chloride (NaCl) or rock salt type
Structure where the coordination number for both cations and anions is 6.
Rock Salt Structure
The coordination number is 8 for both ion types.
Cesium Chloride Structure
A third AX structure is one in which the coordination number is 4—that is, all ions are tetrahedrally coordinated.
Zinc Blende Structure
If the charges on the cations and anions are not the same, a compound can exist with the
chemical formula ______.
AmXp
It is also possible for ceramic compounds to have more than one type of cation; for two types of cations (represented by A and B), their chemical formula may be designated as ________.
AmBnXp
The properties of ceramics, however, also depend on their _____________-.
microstructure
are by definition natural or synthetic inorganic, non-metallic, polycrystalline materials.
ceramics
are formed by multiple crystal grains joined together during the production process.
Polycrystalline materials
are grown as one three-dimensional crystal.
Monocrystalline materials
Fabrication processes of polycrystalline materials are relatively _______, when compared to single crystals.
inexpensive
a familiar group of ceramics; containers, lenses, and fiberglass represent typical applications.
glass
Most inorganic glasses can be made to transform from a non-crystalline state into one that is crystalline by the proper high-temperature heat treatment. This process is called
crystallization
have been designed to have the following characteristics:
relatively high mechanical strengths; low coefficients of thermal expansion (to avoid thermal shock); good high-temperature capabilities; good dielectric properties (for electronic packaging
applications); and good biological compatibility.
glass-ceramic materials
The most attractive attribute of glass-ceramic materials is
the ease with which they may be _______
fabricated
are manufactured commercially under the trade names of Pyroceram, CorningWare, Cercor, and Vision.
glass-ceramic
One of the most widely used ceramic raw materials is _____. This inexpensive ingredient, found naturally in great abundance, often is used as mined without any upgrading of quality.
clay
The salient properties of these materials include the capacity to withstand high temperatures without melting or decomposing and the capacity to remain unreactive and inert when exposed to severe environments.
refractories
are marketed in a variety of forms, but bricks are
the most common.
refractories materials
are used principally in furnace construction to confine hot atmospheres and to thermally insulate structural members from excessive temperatures.
Fireclay bricks or fireclay refractories
For fireclay brick, ______ is not ordinarily an important consideration because support of structural loads is usually not required.
strength
The prime ingredient for silica refractories, sometimes termed acid refractories, is
silica
These materials, well known for their high-temperature load-bearing capacity, are commonly used in the arched roofs of steel- and glass-making furnaces; for these applications, temperatures as high as 1650 0C (30000F) may be realized.
Silica Refractories
The refractories that are rich in periclase, or magnesia (MgO), are termed ________; they may also contain calcium, chromium, and iron compounds.
Basic Refractories
Some of these are relatively high-purity oxide materials, many of which may be produced with very little porosity. Included in this group are alumina, silica, magnesia, beryllia (BeO), zirconia (ZrO2), and mullite (3Al2O3–2SiO2). Others include carbide compounds, in addition to carbon and graphite. Silicon carbide (SiC) has been used for electrical resistance heating elements, as a crucible material, and in internal furnace components. Carbon and graphite are very refractory, but find limited application because they are susceptible to oxidation at temperatures in excess of about 800C (1470F). As would be expected, these refractories are relatively expensive.
Special Refractories
are used to wear, grind, or cut away other material, which necessarily is softer.
Abrasive ceramics
are those in which an abrasive powder is coated on some type of paper or cloth material; sandpaper is probably the most familiar example.
Coated abrasives
