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CHEMISTRY OF ENGINEERING MATERIALS Flashcards

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1
Q

What is the primary focus of the module on the Chemistry of Engineering Materials?

A

The module explores the intermolecular structure of materials guided by general chemistry principles such as Kinetic Molecular Theory, phase changes, and intermolecular forces.

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2
Q

What is the significance of assessing material properties in engineering?

A

Assessing material properties is crucial for selecting materials suitable for specific applications, considering factors like availability and budget constraints.

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3
Q

Define Tensile Strength.

A

The limit state of tensile stress that leads to tensile failure, either ductile or brittle.

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4
Q

What does Shear Strength refer to?

A

The resistance to stress caused by opposing forces acting along parallel lines through the material.

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5
Q

Fill in the blank: The ability of a material to return to its previous shape after stress is released is known as _______.

A

[Elasticity]

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6
Q

What does Hardness measure?

A

The resistance to localized plastic deformation induced by mechanical indentation or abrasion.

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7
Q

Define Malleability.

A

The ability of a material to be plastically deformed and shaped when cold.

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8
Q

What is Plasticity?

A

The ability of a solid material to undergo permanent deformation in response to applied forces.

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9
Q

List the types of Intermolecular Forces.

A
  • Ion-Dipole
  • Dipole-Dipole
  • Hydrogen Bonding
  • Induced Dipole
  • Dispersion Forces
  • Ionic Forces
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10
Q

True or False: Ionic Forces are the weakest intermolecular forces.

A

False

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11
Q

What is the relationship between Density and Strength of Materials?

A

Higher density indicates more intact matter in its volume, directly contributing to strength.

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12
Q

What is the difference between Crystalline and Amorphous structures in terms of strength?

A

Crystalline structures withstand compression due to their density and ordered structure, while amorphous structures are weaker due to their random internal structure.

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13
Q

What is the Kinetic Molecular Theory?

A

A theory that explains the behavior of particles in different phases of matter based on their kinetic energy.

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14
Q

Describe what a Phase Diagram for Pure Substances illustrates.

A

It shows the configuration of molecules as solid, liquid, or gas under varying pressure and temperature.

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15
Q

What occurs at the Triple Point in a Phase Diagram?

A

All three phases (solid, liquid, gas) are in equilibrium and will not change phase.

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16
Q

What defines a Super Critical Fluid?

A

A phase occurring at high temperature and pressure, exhibiting properties of both liquid and gas.

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17
Q

Explain the concept of saturation in binary mixtures.

A

Saturation is the limit of one component’s concentration in a mixture, beyond which it will settle into its own phase.

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18
Q

What is the ‘Lever Rule’ used for in binary mixtures?

A

It computes the percent mass of liquid and solid in a two-phase system based on concentration.

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19
Q

Fill in the blank: The overall %Weight of B in a binary phase region is found by projecting the system point to the _______.

A

[x-axis]

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20
Q

How is the concentration of B in the liquid phase represented in a binary phase diagram?

A

By projecting the point L to the x-axis.

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21
Q

What does the term ‘monophasic region’ refer to in phase diagrams?

A

A region where both components in a mixture are compatible and exist in the same phase.

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22
Q

What is the formula to calculate %ml?

A

%ml = (Ws - Wo) / (Ws - Wl)

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23
Q

What is the significance of the tie line in a binary phase diagram?

A

The tie line is used for points occurring on binary phase regions.

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24
Q

How is %ms calculated in a binary phase system?

A

%ms = (SO / SL)

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25
At point O in the phase diagram, how many phases are present and what are they?
2 phases: alpha and liquid.
26
What is the percentage of B in the alpha phase at point O?
5.2% B
27
What is the percentage of A in the alpha phase at point O?
94.8% A
28
What is the percentage of B in the liquid phase at point O?
34.5% B
29
What is the percentage of A in the liquid phase at point O?
65.5% A
30
How much of the total 150g is liquid at point O?
94.71g
31
How much of the total 150g is alpha at point O?
55.29g
32
What is the formula for calculating %m(alpha)?
%m(alpha) = 100 * (34.5 - 23.7) / (34.5 - 5.2)
33
What is the value of %m(alpha) at point O?
36.86%
34
What is the formula for calculating %m(liquid)?
%m(liquid) = 100 * (23.7 - 5.2) / (34.5 - 5.2)
35
What is the value of %m(liquid) at point O?
65.1%
36
What is the primary focus of the module on Chemistry of Engineering Materials?
Highly ordered internal structures termed Crystals.
37
What does kinetic molecular theory suggest about the states of matter?
As molecules become more kinetic, the phase of matter gets increasingly fluid.
38
What are the two types of solid materials discussed?
Amorphous and crystalline.
39
What is the primary characteristic of crystalline solids?
Internal repeating patterns.
40
What is an example of an amorphous solid?
Ice.
41
What is an example of a crystalline solid?
Table salt.
42
What is the utility of knowing the internal structure of a material?
To deduce its properties and potential impurities.
43
What are the three allotropes of carbon mentioned?
Diamond, Graphite, Coal.
44
What is the primary reason for diamond's hardness?
Repeating tetrahedral pattern of C-C covalent bonds.
45
How do amorphous substances behave with light?
They often absorb but do not reflect light.
46
What are Bravais lattices used for?
To categorize the geometry in ordered crystals.
47
What is the role of unit cells in crystal structures?
They are repeated patterns that are uniform to the whole crystal matrix.
48
What are the three cubic crystal structures discussed?
Primitive cubic, Body Centered Cubic (BCC), Face Centered Cubic (FCC).
49
How many atoms are in a simple cubic structure?
1 atom.
50
How many atoms are in a Body Centered Cubic (BCC) structure?
2 atoms.
51
How many atoms are in a Face Centered Cubic (FCC) structure?
4 atoms.
52
What is the density of palladium given its unit cell structure?
12.023 g/cm³.
53
What is the formula used to calculate the atomic radius in a cubic structure?
r = d / 2(√2)
54
What is Bragg's Law used for?
To understand basic crystal diffraction.
55
What happens to light in crystalline structures?
It can diffract at consistent angles.
56
What is the mass calculated in the example?
1.2957688 x 10-24 kg ## Footnote This mass is used for further calculations.
57
What is the calculated density in the example?
21511 kg / m3 ## Footnote The standard value is 21450 kg / m3.
58
What is diffraction?
The bending of waves as they encounter an obstacle or an aperture. ## Footnote Refer to Huygens’s Principle.
59
What occurs during positive interference of waves?
Waves add and form a larger wave. ## Footnote Example: build-up of larger tidal waves.
60
What occurs during negative interference of waves?
Waves cancel each other out. ## Footnote Visualized with a string vibrated oppositely.
61
Which type of waves are used in crystal diffraction techniques?
X-rays ## Footnote X-rays have wavelengths comparable to distances between crystal atoms.
62
What is Bragg’s Law?
A formula showing the condition of constructive interference required for diffracted X-rays. ## Footnote It involves the phase lag between two X-rays being an integer multiple of the wavelength.
63
What is the formula for finding X-ray wavelength using Bragg's Law?
λ = 2d sin θ *(1/n) ## Footnote Where d is the spacing and θ is the incident angle.
64
Find the wavelength of X-rays if d = 0.282 nm and θ = 7°.
0.069 nm ## Footnote This is calculated assuming a first order maximum (n = 1).
65
What is the distance between layers in a crystal if X-rays of wavelength 0.154 nm are diffracted at an angle of 14.17°?
314.54 pm ## Footnote This is calculated assuming n = 1.
66
What are the major categories of carbon steel based on carbon content?
* Low carbon steel * Medium carbon steel * High carbon steel ## Footnote Each category has different properties and applications.
67
What is Band Theory?
A quantum mechanical model related to the electrical properties of metals and semiconductors. ## Footnote It explains how metals conduct electricity.
68
What are metal alloys?
Physical mixtures of metals that do not form unique compounds. ## Footnote They can be separated without chemical reactions.
69
What is the effect of doping on semiconductors?
It creates holes that facilitate electron movement. ## Footnote Doping increases conductivity by introducing free spaces for electrons.
70
What is a 'hole' in the context of semiconductors?
A free space within the energy bands where an electron can occupy. ## Footnote It is created when an electron moves to a higher energy state.
71
What distinguishes metals from insulators in terms of band gaps?
Metals have overlapping bands; insulators have large band gaps. ## Footnote Insulators require significant energy to promote electrons.
72
What is the typical carbon content range for medium carbon steel?
0.31% to 0.60% ## Footnote This steel is stronger and more difficult to work with than low carbon steel.
73
What is the typical carbon content range for high carbon steel?
0.61% to 1.50% ## Footnote This steel is very hard and brittle after heat treatment.
74
Fill in the blank: The energy difference between the conduction band and the resting valence band is called the _______.
band gap ## Footnote This gap determines the electrical properties of materials.
75
True or False: Metals form localized electron regions similar to ionic compounds.
False ## Footnote Metals do not form unique compounds but share electrons in a band.
76
What temperature range allows valence band electrons in semiconductors to leave their parent nuclei?
Temperatures above 0 Kelvin ## Footnote At very low temperatures, semiconductors behave like insulators.
77
What is the energy gap range for semiconductors?
1eV to 4eV ## Footnote This is lower compared to insulators which have energy gaps of 9eV or more.
78
What happens to the valence band and conduction band in semiconductors at room temperature?
Valence band is slightly depopulated; conduction band is slightly populated ## Footnote This results in very small electrical conductivity at room temperature.
79
What is Doping in the context of semiconductors?
Introducing impurities to an otherwise pure elemental crystal ## Footnote Doping modifies the electrical properties of semiconductors.
80
What are the two basic types of semiconductors based on purity?
* Intrinsic semiconductors * Extrinsic semiconductors
81
Define intrinsic semiconductors.
Pure substances with a natural 1eV to 4eV band gaps.
82
What are extrinsic semiconductors characterized by?
Artificial band gaps from impurities introduced by doping.
83
What are the two types of extrinsic semiconductors?
* P-type semiconductors * N-type semiconductors
84
What characterizes a P-type semiconductor?
Contains acceptor impurities, has lower electron density and higher hole density ## Footnote Electrons are minority carriers and holes are majority carriers.
85
What characterizes an N-type semiconductor?
Contains donor impurities, has higher electron density and lower hole density ## Footnote Holes are minority carriers and electrons are majority carriers.
86
What is the Greek origin of the word 'polymer'?
Poly (many) + mer (part).
87
What is a monomer?
One part of a polymer.
88
What is the term for a polymer made from a single monomer?
Homopolymer.
89
What is a copolymer?
A polymer derived from the polymerization of multiple different monomers.
90
What are the three main types of polymers based on physical properties?
* Thermoplastics * Elastomers * Thermosets
91
What defines elastomers?
Stretchy materials that return to their original shape due to 3D network structure.
92
What is the characteristic of thermosets?
Rigid materials that do not flow when heated and usually degrade.
93
What is the main property of thermoplastics?
They flow upon heating.
94
How is the size of a polymer typically described?
Using molar mass (g/mol) and degree of polymerization (number of repeat units).
95
What equation relates molar mass, degree of polymerization, and molar mass of the repeat unit?
M = x * Mo
96
What is the mean molar mass of a copolymer?
Mo' = ∑XjMj0 ## Footnote Where Xj is the mole fraction and Mj0 is the molar mass of each type of repeat unit.
97
What is a composite material?
A combination of two or more distinct materials to achieve desirable properties.
98
What is the purpose of the matrix phase in composite materials?
To keep the dispersed phase in place, transfer stress, and protect from the environment.
99
What are the three types of dispersive phases in composites?
* Metal dispersive phases * Ceramic dispersive phases * Polymer dispersive phases
100
What is the difference between continuous and discontinuous fibers in fiber reinforced composites?
Continuous fibers provide maximum strength along one direction; discontinuous fibers provide strength in multiple directions.
101
What is the main advantage of particulate reinforced composites?
Low cost and ease of production.
102
What is the primary advantage of particle reinforced composites?
Low cost and ease of production and forming.
103
How do particulate reinforced composites compare to fibre reinforced composites in terms of strength?
Particulate reinforced composites achieve gains in stiffness, strength, and toughness, but improvements are less than in fibre reinforced composites.
104
What applications are particulate reinforced composites commonly used for?
High levels of wear resistance, such as road surfaces.
105
What are structural composites designed to have?
Low densities and high degrees of structural integrity.
106
Name two common types of structural composites.
* 3D woven composites * Sandwich composites.
107
What is the construction method for three-dimensional composites?
Fiber preforms constructed from yarns or tows arranged into complex three-dimensional structures.
108
What is the core material in a sandwich-structured composite typically made from?
Low strength materials with higher thickness.
109
Which materials are commonly used as core materials in sandwich composites?
* Open- and closed-cell foams (e.g., polyethersulfone, polyurethane) * Balsa wood * Syntactic foams * Honeycombs.
110
What is a key characteristic of nanocomposites?
Dimensions of the dispersed phase particles are on the order of nanometers.
111
How does nanotechnology influence material properties?
It allows for tuning of properties to desirable results due to the size and geometry of materials.
112
What happens to the reactivity of gold when it is reduced to nanoparticles?
Nanogold is extremely reactive, unlike bulk gold which is highly unreactive.
113
What percentage of atoms in a 1 nm nano cube are on the surface?
60%.
114
What was Richard Feynman's contribution to nanotechnology?
He speculated about manipulating materials at the atomic level during a talk in 1959.
115
What was the significance of Don Eigler's work in 1989?
He became the first person to manipulate and position individual atoms.
116
Why are some materials not currently mass-produced despite being superior?
Current inability to mass produce usable quantities economically.
117
What is the focus of nanoelectronics?
The potential of being the electronics of the very near future.
118
Fill in the blank: Nanotechnology involves the control of atoms and molecules to produce materials in the size range of _______.
[1 – 100 nm]
119
True or False: Nanomaterials have properties that are not achievable with larger particle sizes.
True.
120
What materials are commonly used as skin materials in sandwich composites?
* Laminates of glass or carbon fiber-reinforced thermoplastics * Thermoset polymers (e.g., unsaturated polyesters, epoxies) * Sheet metal.
121
What is the purpose of bonding the core to the skins in sandwich composites?
To create a composite structure with high bending stiffness and low density.

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