What is the difference between thermoplastic polymers vs thermosetting?
Thermoplastic are not rigidly connected, therefore ductile
Thermosetting plastics are not as rigidly connected, so they are brittle, but stronger.
True or false: polymers are low density
True
True or false: polymers are high density
False
True or false: ceramics are strong under compression
True
True or false: Ceramics are very brittle
True
What are some properties of semiconductors?
Unique electric behavior that converts electric signals to lasers, LED, and diodes
What are some properties of composite materials?
Blends different materials
Very hard
Shock absorbs
Low cost
True or false: ceramics have high strength to weight ratio
False; polymers and composites do
True or false: polymers have a high strength to weight ratio
True
True or false: glass is amorphous
True
True or false: glass is not amorphous
False
What does amorphous mean?
Does not have regular arrangement of atoms
How does temperature affect ceramics and polymers?
Ceramics and polymers melt at high temperatures, but at low temperatures, they are very brittle
How does corrosion affect metals, ceramics, and polymers?
Metals and ceramics disintegrate
Polymers oxidize
In the periodic table, where would you find carbon based polymers?
4B
In the periodic table, where would you find metallics?
Groups 1 and 2, and transition metals
In the periodic table, where would you find semiconductors?
4B, 2B & 6B, and transition metals
True or false: polymers with strong Van Der Waal bonds are stiffer but brittle
True
What are the differences between diamond and graphite?
Diamonds are arranged in an array, whereas graphite is in layers
In diamonds, all four C are covalently bonded to each other. In graphite, only three.
Graphite is electrically conductive; diamond insulates
How do light optical microscopes work? Why aren't they good?
Uses visible light as a probe to magnify the image.
Not good because smallest they can go is ten to the negative six
How do x-rays work?
Sends electromagnetic radiation that penetrates thru matter to find the arrangement of crystals using a diffractometer to measure space, diffraction peaks, and planes
Can also measure chemical structure; xrays can be used to excite electrons
How does a transmission electron microscope work?
Uses high energy electrons, accelerated with a voltage from 100 000 - 500 000 V, and into a small beam.
Gets directed at a small film. The high energy electrons penetrate film. If there are cracks n shit, electrons split
How does a scanning electron microscope work?
Similar to a transmission electron microscope, it creates a beam across the surface
From the primary beam, the secondary beam would scan the surface for e
Speciman must conduct e
How does a scanning tunnel microscope work?
An atomically sharp probe is scanned over a surface w space in between
Current is between the gap
Image produced is from the vertical motion of the probe
How does an atomic force microscope work?
An atomically sharp probe is scanned over a surface w space in between
Moves up and down
Different heights show different colours
Measures a wide variety of shit
How does a mass spectrometer work?
Gas molecules are converted into positive ions
Magnetic field hits and sorts the ions by mass
Measures chosen gas - can look at partial pressure of ions in a gas
Name a fuel additive and why additives are added
Example: Ethanol, MTBE
1) Improves engine performance by increasing octane rating to increase compressibility before it ignites
2) Add oxygen for a more complete combustion
Compare and contrast metallic and covalent bonds in terms of ductility (ability to bend into shape)
Metallic bonds are non directional. Non directionality and shielding ions by electron cloud leads to higher ductilities.
Covalent bonds are highly directional and this limits ductility making it diffiicult for atoms to slip past one another, therefore not very ductile
