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Material Science > Chapter 13 > Flashcards

Chapter 13 Flashcards

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1
Q

crystallization

A

most inorganic glasses can be made to transform from a noncrystalline state into one that is crystalline by the proper high-temperature heat treatment

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2
Q

glass–ceramic

A

product is a fine-grained polycrystalline material

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3
Q

glass–ceramic materials

A

characteristics: relatively high mechanical strengths, low coefficients of thermal expansion, good high-temperature capabilities, good dielectric properties, and good biological compatibility

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4
Q

structural clay products

A

building bricks, tiles, and sewer pipes—applications in which structural integrity is important

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5
Q

firing

A

a high-temperature heat treatment that increases the

density and strength of a ceramic piece

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6
Q

whiteware

A

ceramics that turn white after firing

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7
Q

refractory ceramics

A

a metal or ceramic that may be exposed to extremely
high temperatures without deteriorating rapidly or
without melting

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8
Q

basic refractories

A

refractories that are rich in periclase or magnesia (MgO)

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9
Q

abrasive ceramics

A

used to wear, grind, or cut away other material, which necessarily is softer

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10
Q

cements

A

when mixed with water, they form a paste that subsequently sets and hardens

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11
Q

calcination,

A
  • grinding and intimately mixing clay and lime-bearing minerals in the proper proportions and then heating the mixture to about 1400”C (2550”F) in a rotary kiln
  • produces physical and chemical changes in the raw materials
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12
Q

hydraulic cement

A

hardness develops by chemical reactions with water

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13
Q

graphitic carbon fibers

A

graphene layers assume the ordered structure of graphite—planes are parallel to one another having relatively weak van der Waals interplanar bonds

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14
Q

turbostratic carbon

A

graphene sheets become randomly folded, tilted, and crumpled

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15
Q

microelectromechanical systems

A

miniature “smart” systems consisting of a multitude of mechanical devices that are integrated with large numbers of electrical elements on a substrate of silicon

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16
Q

nanocarbons,

A

-a particle having a size of less than about 100 nm
composed of carbon atoms that are bonded together with sp2 hybridized electron orbitals
-three nanocarbon types: fullerenes, carbon nanotubes, and graphene

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17
Q

single-walled carbon nanotube

A

a single sheet of graphite (i.e., graphene) that is rolled into a tube

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18
Q

glass transition temperature

A

below this temperature, the material is considered to be a glass; above it, the material is first a supercooled liquid and, finally, a liquid

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19
Q

melting point (527)

A

temperature at which the viscosity is 10 Pa-s (100 P); the glass is fluid enough to be considered a liquid

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20
Q

working point (527)

A

temperature at which the viscosity is 103 Pa-s (104 P); the glass is easily deformed at this viscosity

21
Q

softening point (527)

A

maximum temperature at which a glass piece may be handled without causing significant dimensional alterations

22
Q

annealing point (527)

A

at this temperature, atomic diffusion is sufficiently rapid that any residual stresses may be removed within about 15 min

23
Q

strain point (527)

A

-for temperatures below the strain point, fracture will
occur before the onset of plastic deformation
-glass transition temperature will be above the strain point

24
Q

five different forming methods are used to fabricate glass products (528)

A

pressing, blowing, drawing, and sheet and fiber forming

25
Q

pressing (528)

A

glass piece is formed by pressure application in a graphite-coated cast iron mold having the desired shape; the mold is typically heated to ensure an even surface

26
Q

parison (528)

A

temporary shape from a raw gob of glass is formed by mechanical pressing in a mold

27
Q

blowing (528)

A
  • from a raw gob of glass a temporary shape is formed by mechanical pressing in a mold
  • piece is inserted into a finishing or blow mold and forced to conform to the mold contours by the pressure created from a blast of air
28
Q

drawing (528)

A

used to form long glass pieces that have a constant cross section, such as sheet, rod, tubing, and fibers

29
Q

float process (529)

A
  • with this technique, the molten glass passes (on rollers) from one furnace onto a bath of liquid tin located in a second furnace
  • as glass ribbon “floats” on the surface of the molten tin, gravitational and surface tension forces cause the faces to become perfectly flat and parallel and the resulting sheet to be of uniform thickness
  • sheet next passes into an annealing furnace (lehr), and is finally cut into sections
30
Q

thermal stresses (529)

A

stresses introduced as a result of the difference in cooling rate and thermal contraction between the surface and interior regions when a ceramic material is cooled from an elevated temperature

31
Q

thermal shock (529)

A

the fracture of a brittle material as a result of

stresses introduced by a rapid temperature change

32
Q

thermal tempering (530)

A
  • strength of a glass piece enhanced by intentionally inducing compressive residual surface stresses
  • glassware is heated to a temperature above the glass transition region yet below the softening point
  • then cooled to room temperature in a jet of air or, in some cases, an oil bath
  • residual stresses arise from differences in cooling rates for surface and interior regions
33
Q

hydroplasticity (531)

A

when water is added to clay minerals, they become very plastic

34
Q

hydroplastic forming (532)

A

the molding or shaping of clay-based

ceramics that have been made plastic and pliable by adding water

35
Q

slip casting (532)

A

a forming technique used for some ceramic materials.
A slip, or suspension of solid particles in water, is poured into a porous mold. A solid layer forms on the inside wall as water is absorbed by the mold, leaving a shell (or ultimately a solid piece) having the shape of the mold

36
Q

extrusion (532)

A
  • type of hydroplastic forming

- a stiff plastic ceramic mass is forced through a die orifice having the desired cross-sectional geometry

37
Q

slip (532)

A

suspension of clay and/or other nonplastic materials in water

38
Q

drain casting (532)

A
  • when poured into a porous mold, water from the slip is absorbed into the mold, leaving behind a solid layer on the mold wall, the thickness of which depends on the time
  • process is terminated when the solid shell wall reaches the desired thickness, by inverting the mold and pouring out the excess slip
39
Q

green (533)

A

body that has been formed and dried but not fired

40
Q

vitrification (534)

A
  • gradual formation of a liquid glass that flows into and fills some of the pore volume
  • degree of vitrification depends on firing temperature and time, as well as on the composition of the body
41
Q

powder pressing (535)

A

used to fabricate both clay and nonclay compositions,

including electronic and magnetic ceramics, as well as some refractory brick products

42
Q

three basic powder-pressing procedures (536)

A

uniaxial, isostatic (or hydrostatic), and hot pressing

43
Q

uniaxial pressing (536)

A

powder is compacted in a metal die by pressure that is applied in a single direction

44
Q

isostatic pressing (536)

A

powdered material is contained in a rubber envelope and the pressure is applied isostatically by a fluid (i.e., it has the same magnitude in all directions)

45
Q

sintering (536)

A

-coalescence of the powder particles into a denser
mass
-carried out below the melting temperature,

46
Q

hot pressing (537)

A

-powder pressing and heat treatment are performed
simultaneously—the powder aggregate is compacted at an elevated temperature
-costly in terms of time, because both mold and die must be heated and cooled during each cycle

47
Q

tape casting (537)

A

thin sheets of a flexible tape are produced by means of a casting process

48
Q

isomers

A

have same chemical formula but different properties and groups are in different locations

Material Science (6 decks)

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