Metals
Why is aluminum used in airplanes?
Lightweight and strong
Which material has the highest hardness and thermal conductivity?
Diamond
Why do people use salt to melt ice?
It reduces the melting temperature (eutectic temp)
What kind of battery does an iphone use?
Lithium ion battery
What test uses a swinging hammer to measure impact toughness?
Charpy test
What soft metals are used in traditional solder?
What 2D material is used in pencils and is made of carbon layers?
Graphite
Why do silica gel packets say "Do Not Eat"?
They absorb moisture (hygroscopic, dessicant)
Why can saltwater conduct electricity, but pure water can't?
Salt breaks down into ions that carry charge
The Statue of Liberty is green because copper slowly forms what protective layer?
Patina (copper carbonate/hydroxide)
What was the first superconductor (resistance = 0) discovered?
Mercury (liquid helium cooled)
What ceramic component in jet engines protects turbine blades from heat?
Thermal barrier coatings like YSZ
Which metal is known to dissolve aluminum (like a macbook)?
Gallium
Under what conditions can you microwave metal?
It must be smooth to lack sharp peaks for charge build up and discharge
What is the softest material on the Mohs scale?
Talc (hydrated magnesium silicate)
Why are FCC metals more ductile than BCC metals?
High probability of slip and lower critical resolved shear stress
Why is a four-point bend test more accurate than a three-point bend test for ceramics?
It increases the range in which flaws can be present
Under what conditions can you microwave metal?
It must be smooth to lack sharp peaks for charge build up and discharge
What material is 99.8% air and can sit on a flower without bending it?
Aerogel
How do noise-canceling headphones "cancel" sound
They generate inverted sound waves to destructively interfere the noise
Name all 5 of the phases on the Fe-C phase diagram (greek letters accepted)
α-ferrite (BCC)
γ-austenite (FCC)
δ-ferrite (BCC ish, moderate C solubility)
Cementite (Fe₃C)
Liquid (L)
What unusual property allows some ceramics, like zirconia with yttria (YSZ), to have a high fracture toughness?
Transformation toughening: tetragonal to monoclinic stress induced phase transformation at the crack tip puts closing pressure due to volume expansion in the monoclinic phase
Why does baking soda make cookies rise?
It decomposes into carbon dioxide that bubbles to puff the dough up
Shuji Nakamura solved the impossible problem to create the blue LED. What was the semiconductor he used?
Gallium nitride (doped with aluminum (p-type) and indium (n-type)) (2.6eV)
What is the world’s strongest natural biological material (specific strength)?
Spider silk