question

What is atomic number

answer

# of protons in nucleus of atom

question

What is the coefficient "A"

answer

atomic mass unit, amu, 1/12 mass of Carbon 12

1 amu/atom = 1 g/mol

question

What is atomic weight

answer

the weight of 6.022E23 molecules or atoms
units: g/mol

question

4 properties that valence electrons determine

answer

1. Chemical
2. Electrical
3. Thermal
4. Optical

question

Electron changes correspond to quantum [number?]
jumping to: higher level _____ energy, lower level ____ energy

answer

Jumping to higher level ABSORBS energy
Jumping to lower level EMITS energy

question

Describe the wave-mechanical model of an atom

answer

- orbitals not discrete
- Position defined by probability of electron at various locations around nucleus

question

Heisenberg Uncertainty Principle states:

answer

both particle momentum and position cannot be determined simultaneously

question

Schrodinger's equation defines:

answer

a wave function that can be used to determine the probability of finding an electron at a certain location

question

electrons have ____-like and ____-like properties

answer

electrons have WAVE-like and PARTICLE-like properties

question

Each orbital is described by a discrete energy level defined by ______.

answer

Each orbital is described by a discrete energy level defined by QUANTUM NUMBERS.

question

List the quantum numbers and their designation

answer

n = principal (energy level-shell) | K, L, M, N, O (1, 2, 3, etc.)
l = subsidiary (orbitals) | s, p, d, f (0, 1, 2, 3,...n-1)
ml = magnetic 1, 3, 5, 7 (-l to +l)
ms = spin 1/2, -1/2

question

Pauli's Exclusion Principle

answer

No two electrons can have the same quantum numbers.
This leads to being able to have all the elements of the periodic table

question

Electrons have discrete ______; they are ____.

answer

Electrons have discrete ENERGY STATES; they are QUANTIZED.

question

Electrons tend to occupy _____ available energy state.

answer

Electrons tend to occupy LOWEST available energy state.

question

Each electron state can accommodate ___ electrons

answer

Each electron state can accommodate TWO electrons (m = 1/2, -1/2)

question

Electron orbitals (l = 0, 1, 2, etc. or s, p, d, f) describe:

answer

probabilistic location of electrons at a certain energy

question

True of false: most elements have unstable electron configurations

answer

TRUE, most elements have unstable electron configurations

question

What are the electrons called in unfilled shells

answer

Valence electrons

question

Filled shells are [more or less] stable than unfilled shells

answer

Filled shells are MORE stable than unfilled shells

question

Valence electrons are most available for bonding and tend to control the _____ properties.

answer

Valence electrons are most available for bonding and tend to control the CHEMICAL properties.

question

What is the electron configuration of C (atomic number = 6)
put the valence electrons in parentheses

answer

1s2(2s22p2)

question

What is the electron configuration of Fe (atomic number = 26)
put the valence electrons in parentheses

answer

1s2 2s2 2p6 3s2 3p6 (3d6 4s2)

question

Columns have similar valence structure.
Electropositive elements readily ____ electrons to become ____ ions.
Electronegative elements readily ____ electrons to become ____ ions.

answer

Columns have similar valence structure.
Electropositive elements readily GIVE UP electrons to become POSITIVE ions.
Electronegative elements readily ACQUIRE electrons to become NEGATIVE ions.

question

Electronegativity ranges from __ to __.
Large values tend to ____ electrons.
The bottom right of the periodic table has [smaller/greater] electronegativity
The top left of the periodic table has [smaller/greater] electronegativity

answer

Electro negativity ranges from 0.7 to 4.0.
Large values tend to ACCEPT electrons.
The bottom right of the periodic table has SMALLER electronegativity
The top left of the periodic table has GREATER electronegativity

question

Which bonds are PRIMARY bonds (usually STRONG):

Ionic, metallic, van der waals (or induced dipoles), covalent, hydrogen bond (or permanent dipoles)

answer

Ionic, covalent, metallic bonds are primary bonds and usually strong

question

Which bonds are SECONDARY bonds (usually much weaker):

Ionic, metallic, van der waals (or induced dipoles), covalent, hydrogen bond (or permanent dipoles)

answer

van der waals and hydrogen bonds are secondary bonds and are usually much weaker

question

In ionic bonding, a ____ donates electrons and a _____ accepts electrons

answer

In ionic bonding, a METAL donates electrons and a NONMETAL accepts electrons

question

Ionic bonding is between elements with _____ electronegativities.

answer

Ionic bonding is between elements with DISSIMILAR electronegativities.

question

What kind of bond is found in MgO?
After bonding, Mg has the electron structure of? What about O?

answer

MgO is ionic, both Mg and O have the electron structure of Ne.

question

In NaCl, which is the cation and which is the anion? What kind of bond is this?

answer

NaCl, Na is + so it is the cation and Cl is - so it is the anion. It is a ionic bond.

question

In ionic bonding, for stability, nearest neighbors must have ____ charges

answer

In ionic bonding, for stability, nearest neighbors must have opposite charges

question

Coulomb's Law describes the ______ between two charges

answer

Coulomb's Law describes the energy of interaction between two charges

question

For Coulomb's Law, if z1 and z2 are of the same sign, Epot is [+ or -] meaning [attractive or repulsive]

answer

For Coulomb's Law, if z1 and z2 are of the same sign, Epot is + meaning repulsive

question

For Coulomb's Law, if z1 and z2 are of opposite signs, Epot is [+ or -] meaning [attractive or repulsive]

answer

For Coulomb's Law, if z1 and z2 are of opposite signs, Epot is - meaning attractive

question

Coulomb’s Law for a cation and anion will describe a
negative potential energy which is attractive.

However, as the ions come closer, electrons from the
ions interact and ____ each other.

answer

Coulomb’s Law for a cation and anion will describe a
negative potential energy which is attractive.

However, as the ions come closer, electrons from the
ions interact and REPEL each other.

question

Ionic bonding is predominant in ____.

answer

Ionic bonding is predominant in CERAMICS.

question

____ range attraction, ___ range repulsion.

answer

LONG range attraction, SHORT range repulsion.

question

Covalent bonding has similar ____ and ____ electrons. _ & _ orbitals dominate bonding.

answer

Covalent bonds have similar ELECTRONEGATIVITY and SHARE electrons. s & p orbitals dominate bonding.

question

Covalent bonds are _____, meaning between specific atoms participating in electron sharing

answer

Covalent bonds are DIRECTIONAL, meaning between specific atoms participating in electron sharing

question

# of possible covalent bonds for an atom = 8 - N'
N' is the number of _____

answer

# of possible covalent bonds for an atom = 8 - N'
N' is the number of VALENCE ELECTRONS

question

Metallic bond - delocalized as _____ _____. Is it directional or nondirectional?

answer

Metallic bond - delocalized as ELECTRON CLOUD. It is NONDIRECTIONAL.

question

Ionic-Covalent Mixed Bonding-
____ gives the percentage of bonds that are ionic

answer

%IC, %Ionic Character

question

Secondary bonding arises from interaction between _____. Is it directional or nondirectional?

answer

Secondary bonding arises from interaction between DIPOLES.
It is DIRECTIONAL.

question

Relatively weak van der Waals bonds result from attractive forces between electric dipoles, which may be ____ or _____.

answer

Relatively weak van der Waals bonds result from attractive forces between electric dipoles, which may be INDUCED or PERMANENT.

question

For hydrogen bonding, highly ____ molecules form when hydrogen covalently bonds to a nonmetallic element such as fluorine.

answer

For hydrogen bonding, highly POLAR molecules form when hydrogen covalently bonds to a nonmetallic element such as fluorine.
This is the STRONGEST SECONDARY BONDING type.

question

Tm (melting temperature) is larger if Eo (bond energy) is _____.

answer

Tm (melting temperature) is larger if Eo (bond energy) is LARGER.

question

Coefficient of thermal expansion is larger if Eo (bond energy) is _____.

answer

Coefficient of thermal expansion is larger if Eo (bond energy) is SMALLER.

question

Ceramics have _____ and _____ bonding.
Metals have _____ bonding.
Polymers have ____ and _____ bonding.

answer

Ceramics have IONIC and COVALENT bonding.
Metals have METALLIC bonding.
Polymers have COVALENT and SECONDARY bonding.

question

Thanks to ______ forces, geckos can walk on walls.

answer

Thanks to VAN DER WAALS forces, geckos can walk on walls.

question

Dense, ordered packed structures tend to have _____ energies compared to non dense, random packing.

answer

Dense, ordered packed structures tend to have LOWER energies compared to non dense, random packing.

question

Crystalline materials
atomics pack in periodic, ___ arrays, typical of:
- metals
- many ceramics
- some polymers

answer

Crystalline materials
atomics pack in periodic, 3D arrays, typical of:
- metals
- many ceramics
- some polymers

question

Noncrystalline materials...
• atoms have no periodic packing
- occurs for:
1.
2.

answer

Noncrystalline materials...
• atoms have no periodic packing
- occurs for:
1. complex structures
2. rapid cooling

question

Amorphous means

answer

Amorphous means Noncrystalline

question

Metallic Crystal Structures:
- Have the simplest crystal structures
- Tend to be densely packed, because:
1. typically only 1 element is present, so all atomic radii are ____.
2. Metallic bonding is ____.
3. Nearest neighbor distances tend to be ___ in order to lower bond energy.
4. ______ shields cores from each other.

answer

Metallic Crystal Structures:
- Have the simplest crystal structures
- Tend to be densely packed, because:
1. typically only 1 element is present, so all atomic radii are THE SAME.
2. Metallic bonding is NON DIRECTIONAL.
3. Nearest neighbor distances tend to be SMALL in order to lower bond energy.
4. ELECTRON CLOUD shields cores from each other.

question

Small repeat units which describe the crystalline structure of a solid are called _____ _____ and they extend in all directions.

answer

Small repeat units which describe the crystalline structure of a solid are called UNIT CELLS and they extend in all directions.

question

What are the four 3D arrangements found in metals:

answer

What are the four 3D arrangements found in metals:
- SC: Simple Cubic
- BCC: Body-centered cubic
- FCC: Face-centered cubit
- HCP: Hexagonal closed-packed

question

Describe Simple Cubic Structure (SC)

answer

SC:
- Rare, due to low packing density (only Po has this structure)
- Close-packed directions are cube edges
- Coordination # = 6
- APF = .52
- R = .5a
- 1 atom / unit cell

question

Coordination # is

answer

Coordination # is the number of nearest neighbors

question

Describe Body Centered Cubic Structure (BCC)

answer

BCC:
- Atoms touch each other along cube diagonals
- Coordination # = 8
- 2 atoms / unit cell
- APF = .68
- 4R = sqrt(3)a

question

Describe Face Centered Cubic Structure (FCC)

answer

FCC:
- atoms touch each other along face diagonals
- MAXIMUM achievable APF, = .74
- 4 atoms / unit cell
- 4R = sqrt(2)a
- coordination # = 12
- ABCABC stacking sequence

question

Describe Hexagonal Close-Packed Structure (HCP)

answer

HCP:
- atoms touch each other along multiple directions
- coordination # = 12
- 6 atoms / unit cell
- APF = .074
- ABAB stacking sequence

question

What is the relationship between theoretical density, p, for metals, ceramics, and polymers. Why?

answer

In general:
p metals > p ceramics > p polymers

Metals have:
- close-packing (metallic bonding)
- often large atomic masses

Ceramics have:
- less dense packing
- often lighter elements

Polymers have:
- low packing density (often amorphous)
- lighter elements (C, H, O)

Composites/fibers have intermediate values

question

Some properties of crystalline materials often related to _____ _____.

answer

Properties of crystalline materials often related to CRYSTAL STRUCTURE.

question

For a crystalline solid, when the periodic and repeated arrangement of atoms is perfect or extends throughout the entirety of the specimen without interruption, the result is a ____ ____.

answer

For a crystalline solid, when the periodic and repeated arrangement of atoms is perfect or extends throughout the entirety of the specimen without interruption, the result is a SINGLE CRYSTAL.

Some real life applications:
- turbine blades
- electronic microcircuits
- diamond single crystals for abrasives

question

anisotropy

answer

directionality of properties is termed anisotropy, and it is associated with the variance of atomic or ionic spacing with crystallographic direction.

a single crystal is anisotropic bc its material properties vary with crystal orientation

GRAINS TEXTURED

question

isotropic

answer

Substances in which measured properties are independent of the direction of measurement are isotropic

GRAINS RANDOMLY ORIENTED

question

Single crystals have properties that vary with direction so they are

answer

Single crystals have properties that vary with direction so they are ANISOTROPIC

question

Polycrystals (majority of engr materials) may/may not vary with direction
- each "grain" is a single crystal
- if gains are randomly oriented:
- if grains are textured:

answer

Polycrystals (majority of engr materials) may/may not vary with direction
- each "grain" is a single crystal
- if gains are randomly oriented: isotropic
- if grains are textured: anisotropic

question

How many possible lattice parameters

answer

3 possible lattice parameters

question

What is polymorphism (or allotropy)

answer

Polymorphism is when there are two or or more distinct crystal structures for the same material

ex. carbon, diamond, graphite

question

What is solidification

answer

Solidification: result of casting of molten material
- 2 steps:
1. Nuclei form
2. Nuclei grow to form crystals - grain structure

- start with a molten material, all liquid, crystals grow until they meet each other

question

Grain Boundaries
• Regions between crystals
• Transition from ____ of one region to that of the
other
• Slightly disordered
• Low density in grain boundaries

– ____ mobility
– ____ diffusivity
– ____ chemical reactivity

answer

Grain Boundaries
• Regions between crystals
• Transition from LATTICE of one region to that of the
other
• Slightly disordered
• Low density in grain boundaries

– HIGH mobility
– HIGH diffusivity
– HIGH chemical reactivity

question

Grains can be:
- _____ (roughly same size in all directions)
- _____ (elongated grains)

answer

Grains can be:
- EQUIAZED (roughly same size in all directions)
- COLUMNAR (elongated grains)

question

Grain Refiner can be added to make _____, more ____, ______ grains.

answer

Grain Refiner can be added to make SMALLER, more UNIFORM, EQUIAXED grains.

question

Turbine Blade Casting

1. _________
Uses a ceramic mold and develops an equiaxed grain structure

2. _____
Ceramic mold with direction heating to produce elongated grains

3. _____
Strict control of crystallization leads to structure which is creep and thermal shock resistant

answer

Turbine Blade Casting

1. CONVENTIONAL
Uses a ceramic mold and develops an equiaxed grain structure

2. DIRECTIONALLY SOLIDIFIED
Ceramic mold with direction heating to produce elongated grains

3. SINGLE CRYSTAL
Strict control of crystallization leads to structure which is creep and thermal shock resistant

question

Most common amorphous material that you come in contact with on a daily basis

answer

GLASS is the most common amorphous material that you come in contact with on a daily basis

question

Talk about amorphous metals

answer

- Although more challenging, metals can also be made
amorphous.

• No long range order
• No grain boundaries
• Formed from rapid solidification techniques
• Alloys contain Fe, Ni, Cr with C, P, B, Al, Si

• PROPERTIES: Excellent corrosion resistance, good
ductility, high strength

• Applications include face-plate inserts on golf club
heads and thermally-sprayed composite amorphous
metal coated baseball bats

question

There is no such thing as a ____ crystal.
Many of the important properties of materials are due to the presence of _____.

answer

There is no such thing as a PERFECT crystal.
Many of the important properties of materials are due to the presence of IMPERFECTIONS.

question

Vacancy atoms, interstitial atoms, and substitutional atoms are all _____ defects.

answer

Vacancy atoms, interstitial atoms, and substitutional atoms are all POINT defects.

question

Dislocations are _____ defects.

answer

Dislocations are LINE defects.

question

Grain boundaries are _____ defects.

answer

Grain boundaries are AREA defects.

question

Vacancies: vacant atomic sites in a structure
- point defect
- all crystalline solids contain vacancies
- presence of vacancies increases ______ of the crystal.

answer

Vacancies: vacant atomic sites in a structure
- point defect
- all crystalline solids contain vacancies
- presence of vacancies increases ENTROPY (DISORDER) of the crystal.

question

Each _____ is a potential vacancy site.

answer

Each LATTICE SITE is a potential vacancy site.

question

Equilibrium vacancy concentration varies with _____.

answer

Equilibrium vacancy concentration varies with TEMPERATURE.

question

Arrhenius equations are used to describe many ____ activated processes. What are some examples from class?

answer

Arrhenius equations are used to describe many THERMALLY activated processes. What are some examples from class?

- The equilibrium vacancy concentration equation

question

______ temperature causes surface island of atoms to grow.
The equivalent vacancy concentration ______ via atom motion from the crystal to the surface, where the atoms join the island.

answer

INCREASING temperature causes surface island of atoms to grow.
The equivalent vacancy concentration INCREASES via atom motion from the crystal to the surface, where the atoms join the island.

question

_________ are "extra atoms" position between atomic sites.

This is a _____ defect.

answer

SELF-INTERSTITIALS are "extra atoms" position between atomic sites

This is a POINT defect.

question

Which point defect, vacancy or self-interstitial, is more likely? Why?

answer

Vacancy is MORE likely than self-interstitial.

Self interstitial atoms are large relative to interstitial space and therefore much less likely than vacancy.

question

There is no such thing as a ____ metal.
Most metals are ____.

answer

There is no such thing as a PURE metal.
Most metals are ALLOYS.

question

Impurity atoms deliberately added to modify _____.

answer

Impurity atoms deliberately added to modify PROPERTIES.

e.g.: adding 7.5% Cu to silver to make Sterling Silver:
- Pure Ag = very soft
- Cu improves mechanical strength w/o reducing
corrosion resistance

question

Adding impurity atoms results in solid ___ or second ___ formation.

answer

Adding impurity atoms results in SOLID SOLUTION or SECOND PHASE formation. solvent = majority component or "host" solute = minority concentration

question

Two outcomes of impurity added to host:

1. Solid Solution of impurity in host, can be _______ or ______.
2. Solid solution of impurity in host plus particles of a new phase (usually for a _____ amount of impurity)

answer

Two outcomes of impurity added to host:

1. Solid Solution of impurity in host, can be SUBSTITUTIONAL or INTERSTITIAL
2. Solid solution of impurity in host plus particles of a new phase (usually for a LARGER amount of impurity)

question

What are the conditions for substitutional solid solution (S.S)? What is the name of the rule?

answer

W. Hume – Rothery rule

– 1. difference in r (atomic radius) < 15%
– 2. Proximity in periodic table
• i.e., similar electronegativities
– 3. Same crystal structure for pure metals

– 4. Valency
• All else being equal, a metal will have a greater tendency
to dissolve a metal of higher valency than one of lower
valency

question

Dislocations:
- are ____ defects
- slip between crystal planes result when dislocations move
- produce _____ deformation.

answer

Dislocations:
- are LINE defects
- slip between crystal planes result when dislocations move
- product PERMANENT (PLASTIC) deformation.

question

Linear Defects (Dislocations) are __-dimensional defects around which atoms are misaligned.

answer

Linear Defects (Dislocations) are ONE-dimensional defects around which atoms are misaligned.

question

Edge dislocation:
- _____ inserted in crystal structure
- b (burger's vector) is _____ to dislocation line

answer

Edge dislocation:
- EXTRA HALF-PLANE OF ATOMS inserted in crystal structure
- b (burger's vector) is PERPENDICULAR to dislocation line

question

burger's vector (b) measures _____.

answer

burger's vector (b) measures lattice distortion.

question

In dislocation motion, bonds across the slipping planes are ______ and ______ in succession.

answer

In dislocation motion, bonds across the slipping planes are BROKEN and REMADE in succession.

question

_____ dislocation:
- spiral planar ramp resulting from shear deformation.
- b _____ to dislocation line.

answer

SCREW dislocation:
- spiral planar ramp resulting from shear deformation.
- b PARALLEL to dislocation line.

question

(it would be really weird if he asked this but...)
In _____ (a program):
– a region of crystal containing a dislocation can be rotated in 3D
– dislocation motion may be animated

answer

(it would be really weird if he asked this but...)
In VMSE (a program):
– a region of crystal containing a dislocation can be rotated in 3D
– dislocation motion may be animated

question

Dislocations are present in virtually all ____ materials.

answer

Dislocations are present in virtually all CRYSTALLINE materials.

question

Dislocations are visible in ____ _____.

answer

Dislocations are visible in ELECTRON MICROGRAPHS.

question

Crystal structures prefer _____ planes & directions.
Compare the planes among the crystal structures:
FCC:
HCP:
BCC:

answer

Crystal structures prefer CLOSE-PACKED planes & directions.
Compare the planes among the crystal structures:
FCC: many close-packed planes/directions
HCP:only one plane, 3 directions
BCC: none

question

Planar defects in solids:

Surfaces
• Termination of the crystal structure.
• Surface atoms are not bonded with the ____ number of
nearest neighbors (bonding ____ than coordination number).
• Because the surface atoms don’t have all the bonds they would like, they are in a ____ energy state due to surface energy (J/m?).
• There is a driving force to reduce this energy in a material by reducing the total ____ ____.
• Easily accomplished in liquids, but not so easy in solids.

answer

Planar defects in solids:

Surfaces
• Termination of the crystal structure.
• Surface atoms are not bonded with the MAXIMUM number of nearest neighbors (bonding LESS than coordination number).
• Because the surface atoms don’t have all the bonds they would like, they are in a HIGHER energy state due to surface energy (J/m?).
• There is a driving force to reduce this energy in a material by reducing the total SURFACE AREA.
• Easily accomplished in liquids, but not so easy in solids.

question

Grain Boundaries
• Regions between crystals
• Transition from lattice of one region to that of the other
• Atomic bonding is less regular along the grain boundary leading to a grain boundary ______
• ____ ____ tend to segregate here
• Crystallographic misalignment exists

answer

Grain Boundaries
• Regions between crystals
• Transition from lattice of one region to that of the other
• Atomic bonding is less regular along the grain boundary leading to a grain boundary ENERGY
• IMPURITY ATOMS tend to segregate here
• Crystallographic misalignment exists

question

Grain Boundaries:
• ______ ______ can form when edge dislocations line up.
• ______ ______ are between two different phases in an alloy
• ______ ______ is essentially a reflection of atom positions across the twin plane.
• ______ _____
– For FCC metals an error in ABCABC packing sequence
– Ex: ABCABABC

answer

Grain Boundaries:
• TILT BOUNDARIES can form when edge dislocations line up.
• PHASE BOUNDARIES are between two different phases in an alloy
• TWIN BOUNDARY is essentially a reflection of atom positions across the twin plane.
• STACKING FAULTS
– For FCC metals an error in ABCABC packing sequence
– Ex: ABCABABC

question

A catalyst ______ the rate of a chemical reaction
without being consumed
Active sites on catalysts are normally _____ defects

answer

A catalyst INCREASES the rate of a chemical reaction
without being consumed
Active sites on catalysts are normally SURFACE defects

question

Optical Microscopy
• Useful up to _____X magnification.
• _____ removes surface features (e.g., scratches)
• _____ changes reflectance, depending on crystal
orientation. Grain boundaries are susceptible to this.

answer

Optical Microscopy
• Useful up to 2000X magnification.
• POLISHING removes surface features (e.g., scratches)
• ETCHING changes reflectance, depending on crystal
orientation. Grain boundaries are susceptible to this.

question

Polarized light – metallographic scopes often use polarized light to increase ____ – Also used for transparent samples such as polymers

answer

Polarized light – metallographic scopes often use polarized light to increase CONTRAST – Also used for transparent samples such as polymers

question

The _______ of the light determines its color.
It also determines the resolution of what we observe

answer

The WAVELENGTH of the light determines its color.
It also determines the resolution of what we observe

question

Scanning Electron Microscopy
• Surface is scanned by an electron beam and reflected
electrons are collected to produce an image.
• Surface must be electrically _______.
• Magnifications of _______X possible with good
depth of field.

answer

Scanning Electron Microscopy
• Surface is scanned by an electron beam and reflected
electrons are collected to produce an image.
• Surface must be electrically CONDUCTIVE.
• Magnifications of 10,000-100,000X possible with good
depth of field.

question

Transmission Electron Microscopy
• Electron beam passes through the specimen
• Image is created due to contrast from beam scattering from the elements in the material.
• Specimen must be ___ ___ to allow for transmission
• Magnification up to _______X.

answer

Transmission Electron Microscopy
• Electron beam passes through the specimen
• Image is created due to contrast from beam scattering from the elements in the material.
• Specimen must be VERY THIN (<100nm) to allow for transmission
• Magnification up to 1,000,000X.

question

Scanning Probe Microscopy
• Neither ____ nor ____ are used.
• A tiny probe with a very sharp tip is brought into close contact with the specimen surface.
• Electronic and other interactions between the tip and the specimen atoms to generate 3-D topography.
– Nanometer scale resolution with ________X magnification.

answer

Scanning Probe Microscopy
• Neither LIGHT nor ELECTRONS are used.
• A tiny probe with a very sharp tip is brought into close contact with the specimen surface.
• Electronic and other interactions between the tip and the specimen atoms to generate 3-D topography.
– Nanometer scale resolution with 1,000,000,000X magnification.

question

________ _______ Microscopy
• A sharp tip (usually tungsten or platinum/iridium) brought within 0.5-1 nm of surface.
• Interactions between the tip and the surface lead to electron transfer and a measurable current.
• ***can be used to manipulate atoms***

answer

SCANNING TUNNELING Microscopy
• A sharp tip (usually tungsten or platinum/iridium) brought within 0.5-1 nm of surface.
• Interactions between the tip and the surface lead to electron transfer and a measurable current.
• ***can be used to manipulate atoms***

question

Diffusion is mass transport by _____ _____.

answer

Diffusion is mass transport by ATOMIC MOTION.

question

Mechanisms for diffusion in solids include _____ diffusion or ______ diffusion.

answer

Mechanisms for diffusion in solids include VACANCY diffusion or INTERSTITIAL diffusion.

question

Interdiffusion: In an alloy, atoms tend to migrate from regions of ____ concentration to regions of ____ concentration.

_______: In an elemental solid, atoms can also migrate.

answer

Interdiffusion: In an alloy, atoms tend to migrate from regions of HIGH concentration to regions of LOW concentration.

SELF-DIFFUSION: In an elemental solid, atoms can also migrate.

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