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MTL200 Midterm Test With Correct Answers (graded a+).
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What are the three primary material eras? - ANSWER Stone Age, Bronze Age, Iron Age
What are the four levels of Material Structures? - ANSWER Subatomic Structures, Atomic Structures, Micro structures, Macro structures
What are the three basic materials? - ANSWER Metals, Ceramics and Polymers
Advanced Materials - ANSWER semiconductors, biomaterials, smart materials, nanomaterials
atomic number - ANSWER the number of protons in the nucleus of an atom, usually equals the number of neutrons
Isotope - ANSWER Atoms of the same element that have different numbers of neutrons
formula for atomic mass - ANSWER Atomic Number + Neutrons
mole - ANSWER the SI base unit used to measure the amount of a substance 6.022 x 10^
Bohr's Atomic Model - ANSWER Atoms have levels surrounding the nucleus where electrons are found. Levels can hold different amounts of electrons depending on their distance from the nucleus.
Wave-Mechanical Model [Schrodinger's Model] - ANSWER Modern model of the atom, atoms have electrons in "orbitals" that are like clouds around the
nucleus
Quantum Numbers - ANSWER A set of four numbers that specify the properties of atomic orbitals and the properties of electrons in orbitals
Principal Quantum Number (s) - ANSWER symbolized by n, indicates the main energy level/shell occupied by the electron. N is the row in the periodic table
Secondary Quantum Number - ANSWER symbol = l; tells which sublevel the electron is on and determines the shape of the orbital; sublevels are repetitively numbered and also lettered
Valence Electrons - ANSWER The electrons in the outermost shell, which participate in the bonding between atoms.
Pauli Exclusion Principle - ANSWER An atomic orbital may describe at most two electrons, each with opposite spin direction
Bonding Energy - ANSWER The energy required to separate two atoms that are chemically bonded to each other to an infinite distance
What does a column group represent in a periodic table? - ANSWER Similar valence electron configurations/structure and chemical/physical properties
Electropositive Elements - ANSWER The elements have a tendency to release valence electrons (metals) and have a low electronegativity
Electronegative Elements - ANSWER The elements having a tendency to accept valence electrons (non-metals) and have a high electronegativity. [MC]
What is the general trend on the periodic table for increasing the
repeating or periodic array over large atomic distances
Unit Cell - ANSWER a basic structural unit of a crystal structure, defined in terms of geometry and atom positions within a parallelepiped volume.
FCC Number of Atoms, Coordination Number and APF - ANSWER 4 atoms in Unit Cell
12 Coordination Number
APF is 0.74 or 74%
BCC Number of Atoms, Coordination Number and APF - ANSWER 2 atoms in Unit Cell
8 Coordination Number
APF is 0.68 or 68%
HCP Number of Atoms, Coordination Number and APF - ANSWER 6 atoms in Unit Cell
12 Coordination Number
APF is 0.74 or 74%
For BCC, the relation between the atomic radius and unit cell length - ANSWER a=4R/sqrt(3)
For FCC, the relation between the atomic radius and unit cell length - ANSWER a = 2Rsqrt(2)
Polymorphism - ANSWER The phenomenon of a solid material to exist in more than one form of crystal structure.
Allotropy - ANSWER Polymorphism but in Elements.
Linear Density Formula - ANSWER Number of Atoms in a Direction Vector/Length of Direction Vector
Planar Density Formula - ANSWER Number of Atoms centered on a Plane / Area of Plane
HCP Closest Packed Plane and Stacking Pattern - ANSWER (0001) and ABABAB...
FCC Closest Packed Plane and Stacking Pattern - ANSWER (111) and ABCABCABC...
single crystal - ANSWER A crystalline solid for which the periodic and repeated atomic pattern extends throughout its entirety without interruption.
Polycrystalline - ANSWER Crystalline materials composed of more than one crystal or grain.
Anisotropy - ANSWER Exhibiting different values of a property in different crystallographic directions. (Greater Electrical Conductivity in a Certain Plane)
Isotropy - ANSWER having the same properties in all directions
Bragg's Law - ANSWER n λ =2dsin θ --> fundamental equation of diffraction.
are possible.
alloy - ANSWER A mixture of two or more metals
Two types of Solid Solution - ANSWER Substitutional and Interstitial
Factors affecting the Solubility of Substitutional Solid Solutions - ANSWER 1. Atomic Size
Weight Percentage - ANSWER C1 = m1/(m1+m2)
Atom Percentage - ANSWER C1' = (n_m1)/(n_m1+n_m2)
What is a dislocation? - ANSWER a linear or one-dimensional defect around which some of the atoms are misaligned.
Burgers vector - ANSWER A vector that denotes the magnitude and direction of lattice distortion associated with a dislocation.
edge dislocation - ANSWER A linear crystalline defect associated with the lattice distortion produced in the vicinity of the end of an extra half-plane of atoms within a crystal. The Burgers vector is perpendicular to the dislocation line.
screw dislocation - ANSWER A linear crystalline defect associated with the lattice distortion created when normally parallel planes are joined together to form a helical ramp. The Burgers vector is parallel to the dislocation line.
External Surface - Interfacial Defect - ANSWER Surface Atoms aren't bonded to the maximum number of atoms and thus can be broken off easier.
Grain Boundaries - Interfacial Defect - ANSWER The angle difference between grain boundaries can affect the hardness of the material. Higher angles between the alignment of boundaries can create harder to move grains.
Phase boundaries - Interfacial Defect - ANSWER Different phases can have different properties in a multi phase material
Twin Boundaries - ANSWER a special type of grain boundary across which there is a specific mirror lattice symmetry
interstitial diffusion - ANSWER A diffusion mechanism by which atomic motion is from interstitial site to interstitial site.
diffusion flux - ANSWER The quantity of mass diffusing through and perpendicular to a unit cross-sectional area of material per unit time.
steady-state diffusion - ANSWER The diffusion condition for where the diffusion flux is independent of time
What is the driving force of steady-state diffusion? - ANSWER The concentration gradient.
Components - ANSWER A chemical consituent of an alloy either pure metal or compound.
System - ANSWER A specific body of material under consideration or a series of possible alloys. Consisting of the same components (Pb-Sn Systems)
Solubility Limits - ANSWER The max concentration of solute that may be added without forming a new phase.
Phase - ANSWER A homogeneous portion in a system having uniform physical & chemical characteristics
What are the 4 characteristicts of a mictorstructure - ANSWER 1. # of Phase
The major factors affecting the structure - ANSWER 1. Alloying Elements
Equilibrium - ANSWER State of a system corresponding to the minimum free energy, where the phase characteristics can remain constant over an indefinite time period.
Free Energy - ANSWER A thermodynamic quantity that is a function of both the internal energy and entropy (or randomness) of a system. At equilibrium, the free energy is at a minimum.
Meta State - ANSWER Non equilibrium state that may persist for a long time.