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Materials Engineering > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

Q: What are the steps in the Materials Selection Process?

A

A:

Pick Application: Determine required properties.
Identify candidate material(s) based on properties.
Identify required processing for the chosen material.

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2
Q

What are some examples of material processing methods?

A

A: Casting, sintering, vapor deposition, doping, forming, joining, annealing.

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3
Q

Q: What are the main properties to consider when selecting materials?

A

A: Mechanical, electrical, thermal, magnetic, optical, deteriorative.

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4
Q

Q: What are the key characteristics of metals?

A

A:

Strong, ductile.
High thermal & electrical conductivity.
Opaque, reflective

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5
Q

Q: What are the key characteristics of polymers/plastics?

A

A:

Soft, ductile, low strength, low density.
Thermal & electrical insulators.
Optically translucent or transparent.

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6
Q

Q: What are the key characteristics of ceramics?

A

A:

Brittle, glassy.
Non-conducting (insulators).
Ionic bonding (refractory), compounds of metallic & non-metallic elements.

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7
Q

Q: What is the atomic number (Z) of an element?

A

A: The number of protons in the nucleus, and also the number of electrons in a neutral species.

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8
Q

Q: What is the formula for atomic mass?

A

A: Atomic mass = Protons + Neutrons = Atomic mass unit (amu), where 1 amu is 1/12th the mass of Carbon-12.

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9
Q

Q: How many atoms or molecules are in one mole of a substance?

A

A: 6.022 x 10²³ (Avogadro’s number).

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10
Q

Q: What do electron energy states represent?

A

A: energy level. the 3-dimensional space surrounding the nucleus where electrons are most likely to be, tend to occupy the lowest available energy state.

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11
Q

Q: What are the quantum numbers that describe an electron’s state?

A

A:

Principal (n): Energy level (shells).
Subsidiary (l): Orbital shape.
Magnetic (ml): Orbital orientation.
Spin (ms): Spin of the electron (±½).

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12
Q

Q: What dual properties do electrons have?

A

A: Electrons have both wavelike and particulate properties.

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13
Q

Q: What are two wavelike characteristics of electrons?

A

A:

Electrons are in orbitals defined by a probability.
Each orbital exists at a discrete energy level determined by quantum numbers.

Interference
When two electron waves meet, they can overlap and create a new wave pattern.

Diffraction
When an electron wave passes through a small opening, it bends around the edges of the opening

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14
Q

Q: Why is the electron configuration of most elements not stable?

A

A: The valence (outer) shell is usually not completely filled, making the electron configuration unstable.

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15
Q

Q: What are valence electrons?

A

A: Valence electrons are the electrons in unfilled shells, available for bonding, and they control the chemical properties of the element.

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16
Q

Q: What is a key characteristic of elements in the same column of the Periodic Table?

A

A: Elements in the same column have similar valence structures.

17
Q

Q: What is the difference between electropositive and electronegative elements?

A

Electropositive elements readily give up electrons to become positive ions.

Electronegative elements readily acquire electrons to become negative ions.

18
Q

Ionic bonding is the “ “ of electrons

A

transfer, with +- electrons

19
Q

Q: What factors determine the physical properties of materials?

A

A: The interatomic forces between atoms, which are influenced by temperature and pressure.

20
Q

Q: What are the types of primary bonding?

A

A: Metallic bonding, ionic bonding, covalent bonding.

21
Q

Q: What is secondary bonding, and what is an example?

A

A: Secondary bonding refers to weaker forces like Van der Waals bonding.

22
Q

Q: What is ionic bonding and between which types of atoms does it occur?

A

A: Ionic bonding occurs between a metal and a non-metal, where the metal donates electrons and the non-metal accepts them. It requires a large difference in electronegativity.

23
Q

Q: ionic bonding predominant in ceramics T/F?

A

A: T. Ionic bonding is predominant in ceramics.

24
Q

Q: How does the coefficient of thermal expansion, α, relate to the bonding energy, E₀?

A

A: A larger α (thermal expansion) corresponds to a smaller E₀ (bonding energy).

25
Q

Q: How is the % ionic character of a bond calculated?

A

A: % ionic character = [1 - exp(-0.25*(XA - XB)²)] × 100%
where XA & XB are the Pauling electronegativities.

26
Q

What are the 2 key characteristics of metallic bonding?

A

Valence electrons are not bound to any particular atom.

Electrons form a “sea of electrons” that drift throughout the metal.
Remaining non-valence electrons and atomic nuclei are called ion cores with a net positive charge.

27
Q

Q: What interactions give rise to secondary or Van Der Waals bonding?

A

A: Interactions between dipoles, which can be permanent dipoles, molecule-induced dipoles, or fluctuating dipoles.

28
Q

Q: Compare bond energy and characteristics for ionic, Covalent, metallic, secondary.

A

Ionic Bond: Large bond energy, nondirectional (ceramics).
Covalent Bond: Variable bond energy, directional (semiconductors, ceramics, polymers).
Metallic Bond: Variable bond energy, nondirectional (metals).
Secondary Bond: Smallest bond energy, directional (inter-chain for polymers, inter-molecular).

29
Q

describe crystalline materials

A

Crystalline Materials: The atoms are neatly arranged in a regular pattern, like a grid., 3d array
typical of metals, most ceramics

30
Q

Q: What are the characteristics of the Simple Cubic (SC) Structure?

A

Atoms are located at the corners of a cube.
Coordination number = 6.
Atomic Packing Factor (APF) = 0.52.

31
Q

Ceramics (Ionic & Covalent Bonding):
____bond strength
____melting temperature
____stiffness
____thermal expansion

A

High bond strength
High melting temperature
High stiffness
Low thermal expansion

32
Q

Q: Describe the Body-Centered Cubic (BCC) structure and its APF.

A

Atoms touch each other along cube diagonals.
Coordination number = 8.
Atomic Packing Factor (APF) = 0.68.

33
Q

Metals (Metallic Bonding):
____bond strength
____melting temperature
____stiffness
____thermal expansion

A

Bond strength varies
Moderate melting temperature
Moderate stiffness
Moderate thermal expansion

34
Q

Polymers (Covalent & Secondary Bonding):
____bond direction
____melting temperature
____stiffness
____thermal expansion
2nd bonds are____

A

Bonding is directionally specific
Secondary bonds are important
Low melting temperature
Low stiffness
High thermal expansion

35
Q

describe noncrystalline materias

A

Noncrystalline Materials: The atoms are scattered randomly without any pattern, like a messy pile, complex structures
-rapid cooling,”, Amorphous” = Noncrystalline

Materials Engineering (2 decks)

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