At some point in my material science and chemistry courses, I speak bluntly to my students that most research suggests that man-made polymers are bad for us.
Some are worse than others, but most research on the effects of polymers on humans seems to suggest that there are bad effects from most man-made polymers. Some are minorly bad, but others - like the family of PFAS - are more obviously and persistently bad.
The video above is short and has a direct message: DuPont is bad (or has acted badly).
The longer video below - from Veritasium - is far longer but is much, much more informative.
If this sounds familiar, you might've seen a semi-recent movie about this story, Dark Waters.
Depleted uranium just sounds terrifying. Sure, you can pick up some uranium ore and yellowcake from United Nuclear, but trying to buy depleted uranium is going to likely be a little dodgier.
With that being said, the US military has used depleted uranium (DU) as a source of armor penetrating ammunition over the years. I thought - wrongly from the video above - that the DU was simply used because of its high density and nature otherwise as nuclear waste. Today's video posits that there are quite a few other advantages of DU in high-caliber munitions applications.
There are also some seemingly obvious health risks involved in living in an area where spent DU shells are peppering the ground or having been in a tank where DU rounds entered and as least slightly vaporized. The video also goes through those health risks and says that they have largely been disproven, though I would be skeptical and appreciate that many military branches are "not considering depleted uranium anymore because of the environmental problems associated with it, be [they] real or perceived."
Oddly, I had heard that old battleship steel - from before the development of atomic/nuclear weapons - was highly valuable for non-radioactive shielding material.
This video does a great job explaining how the Trinity explosion - and subsequent open-air, atmospheric testing of nuclear weapons - polluted any steel made after those tests via the Bessemer process for producing steel from pig iron and using atmospheric air.
I did not know, however, that the battleships scuttled at Scapa Flow had subsequently been salvaged and some of the steel used in this way. (As an aside, your friendly, neighborhood blogger has visited Scapa Flow. It's gorgeous.)
And I also didn't know that the demand for this low-background steel has mostly been superseded because of the switch from Bessemer to basic oxygen steel production.
This article took me a few reads through to get the idea, but here's what I think I have. I'll use quotes from the article...
"[T]he researchers needed to explore the tradeoff between mechanical protection and thermal insulation, properties rooted in a material's molecular structure and orientation."
"Materials with strong mechanical protection, such as metals and ceramics, have a highly ordered and aligned molecular structure. ... Insulating materials, on the other hand, have a much less ordered structure, which prevents the transmission of heat through the material."
" "Our idea was to use this Kevlar polymer to combine the woven, ordered structure of fibers with the porosity of aerogels to make long, continuous fibers with porous spacing in between," said Gonzalez. "In this system, the long fibers could resist a mechanical impact while the pores would limit heat diffusion." "
"[T]he researchers were able to spin long, aligned nanofibers into porous sheets—providing enough order to protect against projectiles but enough disorder to protect against heat."
First off, whoa, there's such a thing as kevlar aerogel?
And B, I think I might need to re-read the article because I kind of went away thinking about what the heck a kevlar aerogel would be.
So much needless special effects and multiplication of the speaker. - and motion that does more to distract from that focus us on the message. This video just screams 90's to me even though it was clearly produced in the 2000s.
I had no idea that we had a director of corrosion policy and oversight (corrdefense).
The most useful part of this video might be in the distracting animation of the 12 types of corrosion that rotate at the top of the video.
I teach, admittedly, a simplified version of material science. That's partially because my students aren't quite ready for more advanced versions but also because I'm not always aware of just how much more there is to material science.
For example, when we study ceramics and glasses, one of the things I explain is that glass is amorphous, and one indicator of that is the fact that it's transparent to visible light. Ceramics, on the other hand, are generally crystalline, and that's why they're opaque.
It turns out things are much more subtle than that. Check out Surmet's ALON (aluminum oxynitride.) From the wikipedia article...
AlON is optically transparent (≥80%) in the near-ultraviolet, visible and midwave-infrared regions of the electromagnetic spectrum. It is 4 times harder than fused silica glass, 85% as hard as sapphire, and nearly 15% harder than magnesium aluminate spinel. Since it has a cubic spinel structure, it can be fabricated to transparent windows, plates, domes, rods, tubes and other forms using conventional ceramic powder processing techniques. AlON is the hardest polycrystalline transparent ceramic available commercially. Combination of optical and mechanical properties makes this material a leading candidate for lightweight high-performance transparent armor applications such as bulletproof and blast-resistant windows and for many military infrared optics. AlON-based armor has been shown to stop multiple armor-piercing projectiles of up to 50 cal. It is commercially available in sizes as big as 18x35-inch monolithic windows.
There is so much to learn...for my students and for me, too.
Well, yeah, who doesn't turn a meteorite into a chef's knife in their spare time?
Bourdain visits with Bob Kramer, a master chef's knife maker who goes through the smelting, forging, and heat treating of some pretty spectacular knives.
At about 5:38 (explanation starts) then at 6:18 (actual visual) is one of the - if correctly described - most stunning things I've ever seen in material science. Kramer explains that there is a 'shadow' that moves through the steel as it - as I understand - undergoes the phase change from FCC to BCC, squeezing the carbon into the harder, BCC form of iron.
I am currently looking for confirmation from a second source, however, that what we see is actually what Kramer says it's showing.
I do believe it goes without saying, "don't try this at home."
At 1:40 the host of Outrageous Acts of Science goes through the idea of bulletproof glass, alternating layers of glass and polycarbonate.
Then, at 1:55 we get the money quote, "composites are used when you want the properties of two different materials, and you want to put them together for different purposes."
That title, from a New Scientist article, might be over-selling things at this stage of development.
Lee and colleagues ... used a laser pulse to superheat gold filaments until they vaporised, acting like gunpowder to fire a micrometre-size glass bullet into 10 to 100 sheets of graphene at 3 kilometres per second – about three times the speed of a bullet fired from an M16 rifle.
That's pretty far from actually having a product in development.
It's sort of like saying that I can take a few steps in my back yard and announcing that I've walked on the moon.
Well, maybe that's a little exaggeration because graphene is amazing stuff.
"...and they go to the hilt to make sure the details are just right."
Seriously?
Ok, if all they're doing is making replica swords, I can see that just cutting it out of a block of metal would be faster, but it can't have nearly the same strength and flexibility that a real sword would.
I'm thinking most of this sword making procedure isn't quite historically accurate, but I will admit that most of my knowledge of sword making comes from Highlander.
From tip to tail, this one's worth showing in full. I know I can't quite make it in one of our periods (48 minutes last year, no guess how long this year), but it would be well worth two days. Brilliant stuff combining art, science, history, so much. Wow.
New video posted as of 7/30/14 - All times should be modified by subtracting about 20 seconds. For example, 11:30 listed below is more like 11:10 in this video.
My highlights...
11:30 - switching from BCC to FCC iron, paralleling the iron wire demo and showing how steel forms from the iron
12:45 - Thoe Gray's tour of the periodic table (love his book, app, poster, all of it)
15:00 - Charpy hardness testing explanation - toughness vs hardness
22:00 - The breaking up of the furnace is just gorgeous to watch...brilliant and blinding and beautiful. Wow...
23:00-25:30 - Could be skipped if need be, compares Japanese samurai films to American westerns
31:10 - cold working, work hardening of copper and how that relates to crystal defects in the sword
33:30-36:00 - Also could be skipped as it doesn't cover any science, just showing us how impressive the swords and swordsmen are.
36:40 - Differences in types of steel - high- and low-carbon steel - and how they are combined to make a better sword
40:50 - Heat treating, quenching and what it does to high- and low-carbon steels
44:00 - Differential thermal expansion, like a bimetallic strip
45:30-47:00 - Skippable...how to use the sword properly in fighting
Playing with oobleck is all well and good, but if we just stop there we don't get to the cool applications of non-newtonian fluids. Lucky for us the military didn't stop there.
