ME 240 - Exam 1 Review - Timothy Becker NAU

BCC Crystals have detectable diffraction:

when the planes h+k+l = even

What is the correct miller indicies notation for the vector in the following hexagonal cell?

[2 2 4̅ 3]

The atomic weight of an atom is:

Number of protons and neutrons

Ionic bonds undergo:

electron transfer from one atom to another

Substitutional solid solutions have atoms that replace the solvent atoms in the crystal structure:

True

Amorphous materials are:

Non-crystalline and transparent

Which of the following materials may form crystalline solids?

Polymers, Metals, and Ceramics

Atomic radius of a metal with the BCC structure is R, what is the volume of the unit cell in terms of R?

\left(\frac{\left(4R\right)}{\sqrt3}\right)^3

HCP Crystals have detectable diffraction:

never

For X-Ray diffraction, the incoming wavelength must be greater than the atomic spacing to diffract.

False

Isotropic crystals are:

Single crystals randomly oriented, Crystals with non-directional properties

Secondary Bonds are directional, and therefore create a dipole.

True

Fick’s first law is a steady-state equation of diffusion

True

What material classification is typically ductile, low strength, and a poor conductor?

Polymer

What is the predominate type of bonding for sodium (Na)?

ionic

Materials with high bond energies typically have low melting temperatures.

False

Metals and ceramics are ___ while glasses are ____:

Crystalline and non-crystalline

An element with the electron configuration

has how many outermost electrons?

8

Atoms near the ____ of the periodic table are considered more electronegative:

right

Metallic bonds are directional, and therefore create a dipole:

False

What material classification is typically brittle, high strength, highly crystalline, and a poor conductor?

Ceramic

What is the predominant type of bonding for carbon (C)?

Covalent

What is the Atomic Packing Factor (APF)?

Number of equivalent atoms within a unit cell

Van der Waals bonds undergo:

Secondary attraction of atomic dipoles

When two atoms are at an equilibrium distance for bonding, the sum of the repulsive and attractive energies equals:

Trough negative energy (slope = 0) vs. r

The drawing below represents the unit cell for which crystal?

FCC

How many atoms are associated with an FCC unit cell?

4

What is the coordination number of an atom in an HCP configuration?

12

What is the coordination number of an atom in an BCC configuration?

8

What is the coordination number of an atom in an FCC configuration?

12

How many atoms are associated with an BCC unit cell?

2

How many atoms are associated with an HCP unit cell?

6

Below is a plane through a simple-cubic crystal structure. What set of indices below represents this structure?

(100)

Metal with a face-centered cubic structure, calculate the atomic radius in terms of the unit cell dimension (a).

a\left(\frac{\sqrt2}{4}\right)

Predominately covalent bonds undergo:

Electron sharing from one atom to the bonded atoms(s)

What are the Miller indices for the plane shown below?

(1̅ 0 1 0)

Completely destructive interference is detectable with X-ray diffraction detectors

False

Substitutional solid solutions have atoms within the spacing between the crystal structures

False

Increased temperature decreases the number of vacancies in a crystal structure

False

Diffusion coefficient decreases with increasing temperature

False

Material temperature is a measure of atomic vibration frequency and amplitude

True

High-angle grain boundaries typically have atoms with a higher energy than low- angle grain boundaries

True

Diffusion mechanisms include:

Vacancy Diffusion, Interstitial Diffusion

Interstitial solid solutions have atoms within the spacing between the crystal sturctures

True

For a "solid solution," the solute is

the atoms of lesser concentration

FCC crystals have detectable diffraction:

if h, k, l are all even or all odd

Point defects include:

atomic substitutions, interstitial spacing, vacancies

For a "solid solution," the solvent is:

the host, the atoms of highest concentration

Planar defects DO NOT include:

interstitial defects