Description
ENMA 150 Materials of
Civilization
- Closed book, Bring a calculator
- Final Exam format
- Short answer questions
- Essay type questions
- Calculation questions (analogous to the homework problems) - In-class guest lectures and videos are considered part of the class - Important concepts (also review Midterm study guide which has more details):
∙ Content from the in-class guest lectures on the World Trade Center and combinatorial materials science, readings and videos shown in class and in discussion section.
o In-Class Lectures
World Trade Center
∙ Steel was main material holding the building up
∙ Steel becomes more brittle with higher rate of deformation
∙ Exceeding 250 degrees C
∙ The impact of the planes didn’t really cause the collapse
∙ The planes weakened the buildings – they stood for 60 and
105 minutes
∙ The jet fuel allowed for the heat to rise and spread and We also discuss several other topics like When do anxiety disorders develop?
continue
∙ Fire was main cause of the collapse
∙ The light, sprayed-on material (fireproofing material) did not stick well, and most internal components in the impact region
were probably stripped clean
∙ Burning paper and other things kept fire going at a high
temperature which allowed the metal to melt
∙ Floors started sagging and collapsing
Combinatorial Materials Science (Dr. Takeuchi)
∙ Give an explanation of combinatorial materials
discovery
o The idea of combinatorial material discovery is
based on the idea that they shoot a laser into a
material that gives off atoms of that material.
They then take the atoms of many materials and
place it on a chip and test the combinations until
they find the properties they are looking for. Don't forget about the age old question of When did john locke write “an essay concerning human understanding”?
o Videos
Making Stuff Cleaner
∙ Electric cars
o Limited by batteries
o Energy density (amount of energy per volume) in
gasoline is much higher than current batteries
o Tank full of gas will allow car to go much further
o Batteries take many hours to recharge while gas
takes few minutes to fill
o New batteries are being developed but far from it
o Tesla is building a “Giga-factory” in Nevada to We also discuss several other topics like What is the tissue type of cardiac muscle?
manufacture lithium ion batteries
∙ Fuel cell
o Hydrogen can be used in a proton exchange
membrane fuel cell to generate electricity
o In a fuel cell hydrogen gas is combined with
oxygen in air to form water
o When this occurs, an electron is released when
the hydrogen is split at the anode in the fuel cell
and can be used to run an electric motor
o The electron is then combined with a proton (half
a hydrogen molecule, minus the electron) and
oxygen at the cathode of the fuel cell to form
water
o Hence the only exhaust for a fuel cell car is water
∙ Problems with fuel cells
o Hydrogen is not readily available as a fuel and it
would take significant energy to make hydrogen
available as a fuel and a new infrastructure would We also discuss several other topics like What is the scientific method(optic)?
have to be developed to distribute it to consumers
o It is difficult to store hydrogen in sufficient
quantities to be useful as fuel in a car with
reasonable range (300+ miles)
o Chicken feathers converted to carbon fibers is
being explored as a possible material for storing
hydrogen
∙ Aluminum based molten salt batteries
o Aluminum is the most abundant metal in the Don't forget about the age old question of What are flozin drugs?
earth’s crust
o Molten salts offer high energy density and high
power density
∙ Solid Oxide Fuel cells (“Bloom Box”)
o Produces electricity directly from oxidizing a fuel o High efficiency
o Long-term stability
o Fuel Flexibility
o Low emissions
o Relatively low cost
o Disadvantage: High operating temperature which results in longer start-up times
∙ Grid Storage batteries
o Electrical energy is stored during times when
production exceeds consumption, and returned to the grid when production falls below consumption o Example: dammed hydroelectricity We also discuss several other topics like What is npp?
∙ Solid Oxide Fuel Cells
o At least 5X more efficient than the ones currently on the market from Bloom Energy
o Thinner electrolyte layers helped optimize fuel cell design
∙ Artificial Photosynthesis
o Convert sunlight into either electricity (for
charging batteries)
o Or to split water to form hydrogen for fuel cell cars ∙ Creating energy from sunlight is different from storing energy in a suitable form of transportation (hydrogen for fuel cells or batteries)
Making Stuff Smarter
∙ Mimicking structure of shark skin to make a plastic that is anti-bacterial
∙ Silicone rubber pads on the “Gecko Robot” that mimics the tiny hairs on a foot of a gecko to allow the robot to climb walls
∙ Self-healing materials
o Repair themselves in response to damage
o Example: Seal a bullet hole using a 3 layer
composite
o Inner and outer layer were a special plastic that closes up after the bullet passes through
o Center layer is a super-absorbent polymer that expands dramatically and rapidly when in contact with fuel
∙ Magnetic rheological fluids
o Contains iron particles and in presence of
magnetic field increases viscosity
o These can be used as the damping fluids in shock absorbers
o Example: military Humvee, found in new cars
∙ Meta-materials
o Special class of artificial materials engineered to
have properties that may not be found in nature
o Metamaterials usually gain their properties from
structure rather than composition
o Applications: materials that will bend light around
a material creating an effective invisibility cloak
∙ Size scales (angstroms – nanometers – microns – millimeters – centimeters – meters) and the associated structures with these size scales, including the concept of hierarchical structure.
o Angstroms (Å): 10-10 meters
Missing/extra atoms
o Nanometers: 10-9 meters
o Microns: 10-6 meters
Crystals (ordered atoms)
Second phase particles
o Millimeters: 10-3 meters
Crystals (ordered atoms)
Crystal Texturing
o Centimeters: 10-2 meters
Crystals (ordered atoms)
Crystal Texturing
o Meters: 1 meter
o Subatomic structure: below the level of the atom (<0.1 nm) o Atomic/Molecular structure: interactions of atoms and molecules with each other (0.1-2 nm)
o Microscopic structure: groups of atoms/molecules interacting with each other (10 - 10,000 nm (10 μm))
o Macroscopic structure: large scale structure visible to eye (0.1 mm and larger)
∙ Historical Ages and approximate dates
o Stone Age - 2my BCE
Lower paleolithic - 1.5my BCE
Upper paleolithic - 40,000 BCE
Neolithic - 9000-8500 BCE
o Modern Era - 8000 BCE
Chalcolithic (Copper Age)4500 BCE
o Bronze Age - 3150 BCE
o Iron Age - 1200 BCE
Caesar Augustus rules Rome ~0 BCE
o Modern Age
∙ The Metals of Antiquity; why are many of the metals of antiquity are quite rare
o Mercury, (Hg) 750BC (native)
Liquid at room temperature
o Iron, (Fe) 1200BC (native, but rare & in meteorites)
Smelting is difficult (melting iron 2000 degrees Fahrenheit) o Tin, (Sn) 2000BC (not native)
Not useful alone
Tin + Copper = Bronze
o Lead, (Pb) 3500BC (not native)
Pipe lining
o Silver,(Ag) 4000BC (native, but rare)
Bad for tools
Found in same ore as lead
o Copper, (Cu) 4200BC (native)
Tools
o Gold, (Au) 6000BC (native)
Electrical connectivity
o Why they are rare?
Elemental abundance gold is really rare so is silver
Most common elements in rocks are iron and aluminum and magnesium
Earliest metals like gold is one of the scarcest elements yet it was one of first discovered
Found in native state – gold, no need to extract
Some of the earliest metals were some of the most rare because they can be found in natural state
Copper and iron are not so tightly packed into their rocks so easier to extract
∙ Six main properties of materials
o Material Property: Materials trait that determines size and kind of response when exposed to a stimulus. Desirable that a material property is independent of material size & shape
o Mechanical: Modulus and Strength, determines response to due applied load or force.
o Electrical: Conductivity and dielectric constant, determines response due to electric field
o Thermal (physical): (specific) heat capacity, thermal conductivity, Tm, Tg, density; determines response due to change in
temperature, application of heat.
o Magnetic: ferromagnetic, paramagnetic, diamagnetic, determines response due to an applied magnetic field.
o Optical: clarity, index of refraction, reflectivity, determines response due to light.
o Chemical: chemical reactivity, determines response due to chemical environment (degradation, oxidation (rust, etc.).
∙ Classification of materials (metals, ceramics, polymers) o Main classes of materials
Metals
∙ Metallic elements such as aluminum
Ceramics
∙ compounds of metallic & non-metallic elements
Polymers
∙ plastic and rubber materials
o Secondary types (Advanced materials)
Semiconductors
∙ Intermediate between electrical conductors and
insulators
Biomaterials
∙ Materials implanted in the human body
Composites
∙ Combination of 2 or more materials
Smart Materials
∙ “Smart” means material is able to sense changes in
local environment and respond with a known behavior
Nanoengineered materials
∙ Materials with very small dimensions (on the order of
nanometers) which have unusual properties
o Silicon Boule – single crystal rod of silicon (pure)
∙ Why the discovery of clay fundamental was in the shift from hunter gatherer to agricultural based societies.
o Used as storage devices
o Instead of going out everyday hunting because there was nowhere to keep food, the storage allowed to keep food fresh
o This allowed more time for other things such as evolving cities
∙ Mechanical properties of materials including elastic and plastic deformation, fracture, (Young’s) modulus, stress, strain, yield stress and strain, fracture stress and strain, creep and fatigue
o 3 types of deformation
Elastic
∙ Deformation is reversible
Plastic
∙ Change in shape of material is not reversible and
remains after deformation
Fracture
∙ Material breaks
o Modulus (stiffness)
Stiffness: measure of the load required to produce a elastic deformation
o Stress
Force applied to a certain area of an object
o Strain
Response of a system to an applied stress
o Yield stress
Amount of stress that an object needs to experience for it to be permanently deformed
o Yield strain
Amount of strain an object can experience before being permanently deformed
o Fracture stress
Amount of stress that an object needs to experience for it to be fractured or broken
o Fracture strain
Amount of strain an object can experience before being permanently fractured or broken
o Creep
Deformation (often slow) that occurs under a constant stress. The applied stress is much less than the normal fracture
stress, but the deformation can be quite large
o Fatigue
Behavior under cyclic deformation. Cyclic deformation often results in crack growth and eventual failure. The is called
failure due to fatigue. The deformation (or applied stress) is often much less than the normal (single cycle) fracture stress
∙ The parts of a stress-strain curve
∙ Equations to know (with units) for mechanical properties o Strain
σ= Eε
∙ σ – Pa
∙ E – Pa
∙ ε – NO UNIT
o Stress
σ=F/A
∙ σ – Pa
∙ F – N
∙ A – m2
o New Length
ε = lf – lo / lo
∙ ε – NO UNIT
∙ l - m
o Elastic stored Energy
(12¿ σε
∙ σ – Pa
∙ ε – NO UNIT
∙ FINAL UNIT – J/m3
∙ The relationship between stress, strain and modulus for elastic deformation
o Modulous (stiffness): measure of the load required to produce a particular elastic deformation
E=σ/ε
o Stress: force applied to a certain cross-sectional area of an object σ=F/A
o Strain: the amount of deformation in the direction of the applied force divided by the initial length of the material
ε = (lf – lo) / lo
ε=σ/E
∙ Elastic energy absorbed/volume:
o Elastic: deformation is reversible
o area under stress-strain curve (joules/m3)
(12¿ σε or equivalently σ2/2E
∙ Units of force (Newtons); stress and modulus (Pascals), strain (meters/meters) and how they are related and what the underling basic unit of length, mass and time (meter, kilogram, seconds) are for Newtons and Pascals. Understand MPa, GPa (powers of 10 for units)
∙ Smelting of copper and the societal/intellectual implications of converting a rock (albeit a mineral) to a metal
o Smite Malachite usable coper
o Allows the separation of the elements to get usable material
∙ Types of Bonding (covalent, ionic, metallic) and relationship to classification of materials
∙ Crystalline versus amorphous materials, Crystalline grains, simple cubic crystal structures
o Crystalline
Dense, regular packing
Structure of ions, molecules, or atoms that are held together in an ordered, three-dimensional arrangement
Highest level of order that can exist in a material
Ex: Quartz
o Amorphous
Non dense, random packing (noncrystalline)
Irregular and lacks repeating pattern of a crystal lattice Occurs by adding impurities (interfere with formation of crystalline structure)
Ex: Glass
o Crystal structure can be thought of as a small box with atoms, molecules or ions located in specific areas of the box
o The general arrangement and order of the atoms in the structure are directly related to the natural properties of the crystal
o Simple Crystal Structures
Rare due to poor packing (only Polonium has this structure)
o Crystalline Grains
Take a full form crystal and there are different color Speckles which are the different crystal grains
Single grains of crystals
Polycrystals
∙ Made of many crystals placed together
∙ Point defects, dislocations, role of dislocations in deformation o Point defects
Vacancies
∙ Empty lattice site
∙ Thermodynamics requires that vacancies are present
even in perfect crystals
∙ Missing atom in the sheet
Self-interstitial
∙ An atom is crowded into a spot between other atoms
and is not a regular lattice site
o Dislocation
Linear defect where some atoms are misaligned
Edge Dislocation
∙ An extra ½ plane of atoms. The extra atoms result in
strain in the nearby crystal lattice
Screw dislocation
∙ An atom is crowded into a spot between other atoms
and is not a regular lattice site
∙ Substitutional versus interstitial atoms, substitutional hardening, strain hardening
o Substitutional impurity atom
Occupies the same place in the lattice that the atom it is “substituting” for occupied
Generally the substitutional atom must be within ~15% of the size of the original atom
Many alloys are substitutional alloys where the two
components can form a solid solution
o Interstitial atoms
Sit between the regular atoms and (consequently) need to be significantly smaller than the surrounding atoms
o Substitutional hardening
Due to the fact that the substitutional atom is generally a (slightly) different size that the surrounding atoms which gives rise to local strain in the crystal.
This impedes dislocation motion during plastic deformation and results in improvement in mechanical properties.
This is why bronze has better mechanical properties than copper
o Strain Hardening
Due to the creation of dislocations during plastic deformation These dislocations impede the motion of dislocations which improves the mechanical properties of the material
It is also called work hardening
∙ Bronze vs. Copper (why was bronze an improvement over copper?) o Copper
Used for its excellent electrical and thermal conductivity, good strength, good formability
Resistant to corrosion
Greeks and Romans made tools with it
Today mostly used in wiring
o Bronze
Alloy that consists primarily of copper with addition of other ingredients
∙ Usually adding tin to copper
Much stronger than copper
Used in construction of sculptures, musical instruments and medals, and bushings and bearings
Resistant to corrosion
∙ What are quasicrystals, what is non-periodic tiling?
o Period tiling
No gaps same shapes lining up
Repeats itself
If you go up 4 feet and over 5 feet you are in center of tile o Non-periodic tiling
No gaps or spaces, but does not repeat itself
You might start at fat diamond and go up a certain space and over a certain space, it might be a different shape
Not normal pattern
o Quasicrystals
3D actual material that has kind of structure
Structural forms that are ordered but not periodic (NON PERIOD TILING)
These are 2 concepts that were previous thought to be contradictory and not allowed in a single material
∙ Constructive versus destructive interference of waves
o Constructive
Crests line up with crests: waves are “in phase”
Waves add and keep the wavelength but double the
amplitude
o Destructive
Crests line up with valleys: waves are “out of phase”
Waves add and cancel out
∙ Bragg’s Law: λ=2dsinθ, Diffraction problems
o Predicts where the scattering angle 2θ where the diffraction peak will occur for a given X-ray (or neutron, light or electron) wavelength o
o
o
o
o
∙ The differences between diffraction and radiography (see diffraction lecture notes)
o Diffraction
Gives you atomic structure of the material
Atomic or Microscopic structure of material
o Radiography
When you go to dentist or doctor
Use X-Rays and get picture
Has same ability of photo, used to see bigger things
Macroscopic structure of material
∙ The significance of gold and silver in society (concept of wealth accumulation, why is gold the logical element for currency); Apple gold. o Gold
Used for jewelry
Logical Element for currency
∙ Not gas
∙ Is not reactive
∙ Not radioactive
∙ Rare but not too rare
∙ Can melt easier to shape
∙ Does not tarnish like gold
∙ Not as abundant as silver
o Silver
Used for jewelry
Became largely used for many industries since abundance of element grew
Highest known electrical and thermal conductivity of all metals
Not logical element for currency
∙ Tarnishes
∙ Too abundant to be used as currency
o Apple gold
Hardened alloy of 18K gold in their high end Apple Watch Metal matrix composite of gold with ceramic particles (Apple Gold)
Ceramic particles are much harder than gold or copper, silver or palladium generally used in a traditional gold alloy and provided enhanced scratch and wear resistance
By definition 1 gram of an 18K gold alloy contains 0.75g of gold and 0.25g of other materials (combination of copper, silver and/or palladium)
∙ Approximately 48% less gold present but the gold alloy is harder and more scratch resistant than traditional
gold
Value of the gold In the Apple Watch Edition
∙ $861
∙ Sold for $10,000
∙ The Iron Age, smelting of iron, bloom iron forged to wrought iron, iron versus steel, the role of carbon, cast iron
o Iron Age
1200 BCE
∙ Caesar Augustus rules Rome ~0 BCE
Native
Rare
Found in Meteorites
o Smelting of Iron
Smelting is difficult (melting iron 2000 degrees Fahrenheit) Iron is extracted from the iron ore and excess oxygen is removed
o Bloom Iron forged to wrought iron
Bloom Iron
∙ Iron containing charcoal and slag (very impure)
∙ Very poor mechanical properties
Forging it into wrought iron (~0.1% C)
∙ Removes slag
∙ Fair mechanical properties (~ bronze)
o Iron vs. steel
Iron
∙ Chemical element that is found in abundance in Earth’s crust
∙ Susceptible to erosion from rust
∙ Soft and malleable
∙ Unable to be used for applications until hardened
Steel
∙ Alloy
∙ Mixing iron with carbon
∙ Extremely strong
∙ Malleable
Overall:
∙ Steel is more rust resistant
∙ Steel has Better weldability
∙ Iron is most commonly used to produce steel
o Role of Carbon
Transforms soft iron into hard and useful steel
o Cast Iron
When too much carbon is added to iron
Creating a very brittle material
Applications: cast-iron pan, piping
∙ Other Math
o Mechanical Properties