Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Materials > Glossary - Michaelmas 2013 > Flashcards

Glossary - Michaelmas 2013 Flashcards

1
Q

Activation energy, Q

A

in diffusion, this is related to the energy required to move an atom from one lattice site to another (Jmol^-1 or eVatom^-1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Anode

A

the electrode at which oxidation occurs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Anisotropic

A

having properties that vary according to the direction of measurement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Alloy

A

A metallic substance that is composed of 2 or more elements

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Amorphous

A

irregular; having no discernible order or shape. In the context of solids, the molecules are randomly arranged, as in glass, rather than periodically arranged, as in a crystalline material. A non-crystalline structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Atomic form factor/Atomic scattering factor

A

Amplitude of radiation scattered by a single atom. It varies with atomic number and with the angle of scattering

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Antiferromagnetism

A

opposition of adjacent magnetic dipoles causing zero net magnetisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Arrhenius plot

A

Plot of ln(rate) for a process or reaction vs. 1/T. The slope is proportional to the activation energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Atactic polymer

A

polymer with configurational base units in a random sequence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Backbone

A

main structure of a polymer onto which substituents are attached

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Birefringence, delta-n

A

difference in refractive index between 2 permitted vibration directions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Bloch walls

A

boundaries between magnetic domains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Body-centred unit cell

A

non-primitive unit cell that is described with a lattice point at the centre of each unit cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Bragg equation

A

basic diffraction equation which relates interplanar spacings to the angle through which beams of radiation are diffracted, for a given wavelength of radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Bravais lattice/Lattice type

A

Classification of lattices based on symmetry, allowing for all possible lattices consistent with a given symmetry. There are 14 Bravais lattices

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Centre of symmetry/Inversion centre

A

point through which an object can be inverted (i.e. all x,y,z transformed to -x,-y,-z) to bring the object into coincidence with itself

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Centrosymmetric

A

possessing a centre of symmetry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Ceramic

A

A compound of metallic and nonmetallic elements, in which the interatomic bonding is predominantly ionic

Compounds of metallic anions with non-metallic cations, which commonly have very high melting temperatures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Close packed structure

A

A structure in which the atoms are packed closely together. For structures made of only one atom type, the common close packed structures are ccp and hcp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Constructive interference

A

combination of rays which are in phase and give an intense beam

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Coordination number

A

number of atoms forming a polyhedron around a central atom in a structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Coordination polyhedron

A

polyhedron (commonly tetrahedron or octahedron) that can be constructed around a cation with the centres of the surrounding anions forming the vertices

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Conventional unit cell

A

unit cell that is orientated in a specific way with respect to the symmetry elements of the crystal. The conventional cell may or may not be primitive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Critical radius ratio

A

ratio of cation radius to anion radius for the condition where the surrounding anions are touching each other as well as the central cation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Crossed polars

A

2 sheets of polaroid (polariser and analyser) orientated at 90 degrees to each other between which a sample is placed for optical examination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Crystal

A

solid form of matter showing translational periodicity in 3d in its atomic arrangement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Crystal structure

A

arrangement of atoms in a single crystal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Crystal system

A

Classification based on the symmetry of the lattice. There are 7 crystal systems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Capacitance,C

A

charge per unit voltage (Farads or CV^-1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Capacitor

A

electrical device consisting of alternating layers of dielectric and conductor, which is capable of storing charge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Cathode

A

electrode at which reduction occurs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Chiral nematic (cholesteric)

A

molecules in adjacent layers are orientated at a slight angle relative to each other (rather than parallel as in nematic). Therefore the Director rotates helically, around an axis perpendicular to the layers.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Compensator

A

sample of an optically anisotropic crystal with a known birefringence (often quartz)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Coercive field Ec/Hc

A

electric/magnetic field that is required to depolarise/demagnetise a ferroelectric/magnetic material (Vm^-1/Am^-1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Concentration cell

A

electrochemical cell whose electromotive force is driven by differences in concentrations across the electrolyte

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Concentration gradient

A

rate of change of composition with distance (m^-4)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Conformation

A

structure of a polymer chain that arises from rotation about the single bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Cross-linking

A

process in which bonds are formed joining adjacent molecules. At low density these bonds add to the elasticity of a polymer, at higher densities they produce rigidity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Curie temperature

A

temperature above which ferroelectric/ferromagnetic behaviour is lost (Celsius or K)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Current density, j

A

current flowing through unit cross-sectional area (Am^-2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Diamagnetism

A

effect caused by the magnetic moment due to orbiting electrons which produces a slight opposition to the imposed magnetic field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Dielectric

A

an electrical insulator which is polarisable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Dielectric breakdown

A

the passage of current through a dielectric material upon application of a large electric field. The maximum field that a dielectric can sustain without breakdown is the dielectric strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Dielectric constant, κ

A

a measure of the rate of change of polarisation with electric field; the ratio of the permittivity of a material to the permittivity of free space

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Diffusion

A

transport of atoms in which the diffusing atom moves relative to its neighbours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Diffusion coefficient (diffusivity), D

A

a temperature dependent coefficient related to the rate at which atoms diffuse, which also depends on the activation energy (m^2s^-1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Dipole

A

2 equal charges of opposite sign, separated by a small distance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Dipole moment, μ

A

electric field generated by a spatial separation of positive and negative charges (Cm) or the magnetic moment generated by electron orbitals and spin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

Director, D

A

the direction of preferred orientation of molecules in liquid crystals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

Disclination

A

point at which the Director in a liquid crystal undergoes an abrupt change in orientation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

Displacement field, D

A

resultant total polarisation field created in a material by application of an electric field (Cm^-2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

Domains

A

regions within a material in which all the electric/magnetic dipoles are aligned

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

Domain wall

A

boundary between ferroelectric/magnetic domains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

Drift velocity

A

average rate at which charge carriers move through a material under the application of an electric field (ms^-1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

dhkl

A

spacing between lattice planes (hkl)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

Destructive interference

A

combination of rays which are out of phase, giving zero intensity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

Diffraction pattern

A

distribution of intensity of radiation scattered by an object

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

Diffractometer

A

instrument used for recording intensities of diffracted X-rays as a function of diffraction angle and sample orientation. There are many different types of diffractometers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

Disordered materials

A

In general this term is used to refer to materials that lack the 3d long-range periodicity of a crystalline substance (e.g. liquids, glasses, polymers, liquid crystals)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

Exchange interaction/exchange energy

A

quantum mechanical electron - electron interaction which favours parallel alignment of magnetic moments. A negative exchange interaction favours anti-parallel alignment of moments.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

Extinction positions

A

orientations in which an anisotropic material appears black between crossed polars. (They occur every 90 degrees, when the PVDs of the sample are parallel to the polariser/analyser)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

Fatigue

A

accumulation of defects in a ferroelectric material which gradually degrades the amount of switched charge

63
Q

Ferrimagnetism

A

magnetic behaviour obtained when 2 types of dipole, with different strengths, oppose one another, leaving a net magnetisation

64
Q

Ferroelectric

A

a material possessing a spontaneous net electrical polarisation which can be switched by an external electric field. A ferroelectric material must be polar and switchable

One that produces domains of spontaneous polarisation whose polar axis can be reversed in an electric field directed opposite to the total dipole moment of the lattice

65
Q

Ferroelectric phase transition

A

transition from a high temperature paraelectric phase to a low temperature ferroelectric phase. Characterised by onset of spontaneous polarisation

66
Q

Ferroelectric/magnetic hysteresis

A

difference in polarisation/magnetisation behaviour upon reversing electric/magnetic field

67
Q

Ferromagnetism

A

existence of a spontaneous magnetic dipole; alignment of magnetic domains can result in a net magnetisation after removal of an imposed magnetic field

68
Q

Flux density, J

A

number of atoms/ions crossing a unit cross sectional area in unit time (m^-2s^-1)

69
Q

Freedericksz Transition

A

reorientation of liquid crystal molecules on the application of an electric field

70
Q

Frenkel defect

A

crystalline defect consisting of an interstitial and a vacancy

71
Q

Fuel Cell

A

energy conversion device that produces electricity by the electrochemical oxidation of a fuel

72
Q

Face -centred unit cell

A

non-primitive unit cell that is described with a lattice point at the centre of each face of the unit cell

73
Q

Fractional coordinates

A

Set of coordinates x,y,z that define the position of an atom in a unit cell in terms of fractions of the unit cell lengths

74
Q

Glass

A

A solid form of matter formed by cooling a liquid sufficiently fast to avoid crystallisation. The arrangement of atoms in a glass does not exhibit periodicity, but on a short length-scale the bonding may resemble that found in a crystal

75
Q

Hard magnet

A

a ferromagnetic material that has a wide hyteresis loop and high remanence

76
Q

Hysteresis loop

A

loop traced out by polarisation/magnetisation as an applied electric/magnetic field is cycled

77
Q

Glide plane

A

glide plane is symmetry operation describing how a reflection in a plane, followed by a transition parallel with that plane, may leave the crystal unchanged

78
Q

Ionic bond

A

primary bond arising from the electrostatic attraction between 2 oppositely charged ions

79
Q

Isotropic

A

Having properties that are the same regardless of the direction of measurement. In the isotropic state, all directions are indistinguishable from each other

80
Q

Isotactic polymer

A

polymer with configurational base units in a single sequential arrangement

81
Q

Kuhn length/segment

A

theoretical treatment of a polymer chain, divided into n Kuhn segments, with Kuhn length, l, so that each segment can be thought of as freely jointed. Complex polymers may be simply modeled as a random walk

82
Q

Lambda (lambda sensor)

A

the air/fuel weight ratio for a petrol engine normalised by the corresponding ratio for complete stoichiometric combustion of petrol

83
Q

Liquid crystal

A

A phase characterised by anisotropy of properties without the existence of a 3d crystal lattice i.e. orientational order, without positional order

A thermodynamic stable phase characterised by anisotropy of properties without the existence of a 3d crystal lattice, generally lying in the temperature range between the solid and isotropic liquid phase, hence the term mesophase

84
Q

Lattice

A

An infinite array of points repeated periodically throughout space. The view from each lattice point is the same as from any other

85
Q

Lattice parameters/Unit cell parameters

A

set of lengths of the edges of the unit cell, a,b,c, and the angles between the unit cell axes, α, β, γ

86
Q

Lattice plane

A

one of a set of parallel planes containing 2 non-parallel intersecting lattice vectors, defined by the Miller indices (hkl)

87
Q

Lattice vector

A

vector between 2 lattice points, defined by the symbol [UVW] = Ua + Vb + Wc

88
Q

Long-range order

A

order between particles correlated over large distances in a solid

89
Q

Miller indices

A

set of parallel, equally spaced lattice planes is specified by the Miller indices (hkl) with reference to the unit cell, where h,k,l are integers. The first plane out from the origin makes intercepts of length a/h,b/k,c/l along the 3 unit cell axes. If one of the indices is 0, the planes are parallel to the associated axis

90
Q

Microstructure

A

the arrangement of phases and other structural features that make up a solid material

91
Q

Mirror plane

A

plane through which reflection of an object brings it back into coincidence with itself

92
Q

Motif

A

element of a structure associated with any lattice point

93
Q

Multiplicity

A

number of equivalent lattice planes which are related by symmetry; important for understanding the intensities of X-ray powder diffraction patterns

94
Q

Magnetic Flux density (Inductance, B)

A

total magnetic flux per unit area (Tesla)

95
Q

Magnetic moment, m

A

strength of the magnetic field associated with electron orbitals/spin (Am^2)

96
Q

Magnetic permeability, μ

A

ratio between magnetic flux density, B, & applied magnetic field, H (Hm^-1)

97
Q

Magnetic susceptibility, χ (Susceptibility)

A

measure of the effect of a magnetic field on the magnetisation of a material; ratio between magnetisation, M, and the applied field, H (dimensionless)

98
Q

Magnetisation, M

A

sum of all magnetic moments per unit volume (Am^-1)

99
Q

Magnetocrystalline anisotropy energy, K

A

extra energy, per unit volume, required to magnetise a material along the ‘hard’ crystallographic axis (Jm^-3)

100
Q

Magnetostriction coefficient, Λ

A

fractional change in length on changing magnetisation from zero to saturation (dimensionless)

101
Q

Monomer

A

simple chemical unit which, when many are joined together, form a polymer

102
Q

Non-crystalline

A

solid state wherein there is no long-range atomic order. Sometimes the terms amorphous, glassy and vitreous are used synonymously

103
Q

Non-primitive unit cell

A

unit cell that encompasses more than one lattice point. Lattice points will be found at the corners of the unit cell, and also in positions such as the centre of the unit cell or in the centres of some or all of the faces of the unit cell

104
Q

Nematic

A

spontaneously anisotropic liquid, composed of rod-shaped molecules with parallel alignment

105
Q

Optic axis

A

for a birefringent sample, a direction along which no birefringence is observed i.e. a direction perpendicular to an isotropic section. The optic axis of a nematic LC is along the director

106
Q

Optical Path difference

A

extra distance traveled by the fast ray outside an anisotropic material in the time it takes for the slow ray to reach the edge of the sample (m)

107
Q

Order parameter

A

describes the orientational order of a liquid crystalline material, taking account of the deviation of orientation of individual molecules from the Director ( 0 for complete disorder, 1 for perfect order)

108
Q

Paramagnetism

A

net magnetic moment caused by alignment of the electron spins when a magnetic field is applied

109
Q

Permitted Vibration Directions

A

2 perpendicular directions in an anisotropic material along which the transverse electric field of light can vibrate

110
Q

Permittivity, ε

A

describes how an electric field is affected by a dielectric (Fm^-1)

111
Q

Perovskite

A

family of ABX3 compounds which commonly show displacive phase transitions by octahedral tilts or atomic displacements

112
Q

Phase

A

a part of a system, homogeneous in composition and structure

a physically distinct form of a given material, when the material can exist as different phases under different conditions of temperature or pressure. Also used to refer to a homogeneous portion of a system that has uniform physical and chemical characteristics

113
Q

Phase diagram

A

a diagram showing the equilibrium phases and phase compositions at each combination of temperature (and/or pressure) and overall composition

114
Q

Photoelasticity

A

stress-induced birefringence. In a polymer, this is caused by stress-induced alignment of polymer chains

115
Q

Piezoelectricity

A

application of stress produces a change in the dielectric polarisation of a material or, conversely, application of an electric field results in strain. Piezoelectric materials must be non-centrosymmetric

116
Q

Piezoelectric coefficient, d

A

measure of the rate of change of dielectric polarisation with applied stress (CN^-1)

117
Q

Pitch

A

distance it takes for the Director in a cholesteric/chiral nematic LC to go through one complete 360 rotation (m)

118
Q

Polar material

A

material with crystal symmetry such that it contains one (or more) unique direction

119
Q

Polarisation, P

A

the dipole moment per unit volume in a medium, or charge per unit area (Cm^-2)

120
Q

Polarisation (of light)

A

property of electromagnetisation waves that describes the direction of the transverse electric field

121
Q

Polarised light

A

light that has passed through a sheet of polariser, and has a transverse electric field that vibrates in one direction only

122
Q

Poled ferroelectric

A

ferroelectric material that has been brought to saturation by a strong electric field and then allowed to relax back to the remanent condition

123
Q

Polymer

A

long chain of covalently bonded atoms

124
Q

Pyroelectricity

A

change in electrical polarisation due to a change in temperature. Pyroelectric materials must be polar

125
Q

Pyroelectric coefficient, p

A

measure of the rate of change of dielectric polarisation with temperature (Cm^-2K^-1)

126
Q

Packing efficiency

A

ratio of the volume contained within the atoms in a crystal structure to the volume of the crystal. Put another way, it is the fraction of the volume of the crystal that is contained within the constituent atoms

127
Q

Phase angle

A

the phase difference between radiation scattered from an atom at the origin of a unit cell and from an atom at a general position within the unit cell

128
Q

Polymorphism

A

existence of a single compound as 2 or more phase with different crystal structures stable under different conditions

129
Q

Primitive unit cell

A

a unit cell that encompasses only one lattice point i.e. a unit cell where the lattice points are only found at the corners of the unit cell

130
Q

Radius ratio

A

ratio of the radii of the cations and anions in a simple ionic structure, which is sometimes useful as a measure of the relative stabilities of different structures possible for a given material

131
Q

Rotation axis

A

the axis, of order n, about which rotation by a given fraction 1/n of a complete rotation brings an object back into coincidence with itself

132
Q

Refractive index, n

A

property that describes the speed of light in a material relative to that in a vacuum. The higher the refractive index, the slower the light travels

133
Q

Remanence

A

the polarisation/magnetisation that remains in a material after it has been removed from an applied electric/magnetic field, due to permanent alignment of dipoles (Cm^-2/Am^-1)

134
Q

Saturation polarisation/magnetisation

A

the state in which all electric/magnetic dipoles have been aligned by an electric/magnetic field, producing maximum polarisation/magnetisation (Cm^-2/Am^-1)

135
Q

Sawyer-Tower circuit

A

test circuit for measuring the hysteresis loop of ferroelectric materials

136
Q

Schottky defect

A

an anion and cation vacancy pair

137
Q

Smectic

A

liquid crystal phase in which the molecules organise themselves into layers

138
Q

SOFC

A

Solid Oxide Fuel Cell

139
Q

Soft magnet

A

ferromagnetic material that has a narrow hysteresis loop and little energy loss on cycling the field

140
Q

Spontaneous polarisation/magnetisation

A

cooperative phenomenon of electric/magnetic dipole ordering below the Curie temperature (Cm^-2/Am^-1)

141
Q

Stoichiometric

A

obeying a strict chemical formula e.g. anion/cation ratio

142
Q

Syndiotactic polymer

A

a polymer with configurational base units in a regular, alternating sequence

143
Q

Screw Axis

A

a screw axis is a symmetry operation describing how a combination of rotation about an axis and a translation parallel to that axis leaves a crystal unchanged

144
Q

Structure factor

A

amplitude of radiation scattered by all atoms in a unit cell. It depends on (a) the fractional coordinates, x, y, z, of atoms in a unit cell and (b) diffraction geometry, as specified by the planes (hkl) from which the diffracted beams are said to be reflected

145
Q

Systematic absences

A

Diffracted beams from a crystal which have strictly zero intensity, due to repeating units of structure which scatter exactly out of phase with each other. They are most easily summarised in terms of lattice type

146
Q

Short range order

A

Order which implies strong correlations between the positions of atoms, in a structure such as glass, over distances of a few Angstroms

147
Q

Translational order

A

A condition when molecules have some arrangement in space. Crystals have 3 degrees of translational order (each molecule is fixed in space with an x,y,z coordinate) and liquids have no translational order

148
Q

Tacticity

A

arrangement of side-groups on a polymer backbone

149
Q

Transducer

A

device that receives one type of input (such as strain) and provides a different type of output (such as an electrical signal)

150
Q

Transformation/transition

A

denote a change in phase (terms used interchangeably)

151
Q

Twisted nematic

A

liquid crystals physically forced to adopt a chiral structure

152
Q

Unique direction

A

a lattice vector in a crystal which is not repeated by any of the symmetry elements present

153
Q

Unit cell

A

any parallepiped in a lattice having lattice points at all corners

Materials (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions