Cubic Unit Cells

I'll admit that I posted this video. If you check, it's on the Lonnie Dusch (the actual name of your friendly neighborhood blogger) account.

I didn't make the video. I didn't clip it from whatever its original source it. But I needed it, and I had a downloaded copy that I got somewhere along the way of teaching the material science summer camps.

So I posted it on YouTube so I could stream it from anywhere.

If that's the event that pushes me over the edge into eternal damnation, I really wish I would've known.

But you might as well benefit from me risking my eternal soul.

So, check this video out.

It's a brilliant computer animation showing the main crystal structures that we cover in our material science course - simple cubic, body centered cubic, face centered cubic, and hexagonal close packing. We get the coordination number of each structure, a great animation showing the slicing to find the unit cell, the percent occupied, the 

The animation showing how many total atoms are in the simple cubic unit cell (at 1:35 - and repeated throughout the video for the other crystal structures) is so simple and elegantly shown.

I absolutely show this one in class every year - though I stop at about 5:34 because they start to get into ionic compounds (ceramics) which are beyond where we go with unit cells.

(I do warn you that it looks like the video locks up about 0:15 - 0:45. The audio continue, but the video goes still. Don't freak out. It works fine after that.)

The wonder material of the 21st century | Monica Cracuin & Dimitar Dimov | TEDxTruro

No, I have never wondered why pushing harder on a pencil while I'm writing makes the line darker.

I just assumed that there were more layers of graphite being left behind.

Oh, wait, that's it?

Wow. that's not a great opening question, Dimitar.

Here Dimitar discusses the benefits of adding graphene to concrete to make the concrete even stronger. Then Professor Cracuin steps in and suggests other uses of graphene - electronics integrated into fabrics or even our skin - and graphene-like materials (?). She mentions a material of two layers of graphene sandwiched around iron chloride (a combination she calls graphexeter - after the University of Exeter where she researches) to make incredibly flexible, durable, conductive displays - possibly even 'tatoo'ed onto the skin or integrated into contact lenses.

As an aside, I think this is the first TED talk I've seen that switches presenters partway through.

Self organising steel balls explain metal heat treatment

TL;DW - Top video great, absolutely show in class...second video mathematical diversion, not efficient use of class time, good math...third video between the two - more mathy but more tightly edited and efficient and material-science-course tied)

I'm posting all three of these videos together because they're part of a series that Steve Mould made (with help on the lower two) exploring ball bearings and ball-pit balls as crystalline modeling tools.

In the above one, Mould makes a really fancy version of our ASM BB board (we use CD cases and airsoft pellets - he uses plexiglass and metal bb's, more akin to the Atomix toy of yesteryear). If you want to make something like his fancy version, here are a couple of links to check out.

Mould uses the BB board the same way we use it in class: to discuss grains, grain boundaries, heat treating etc in crystalline metals. He places the BB board on a shaker to model adding energy via heat (and there's a brilliant view of vacancy defects moving through the crystal at 2:27 and again at 2:35). Mould then discusses how the crystalline structure he's modeling affects the macroscopic properties (hardness, toughness, strength, etc) of the metal.

Honestly, it's a great explanation of about half a day of summer camp, even admitting that his model is limited in exactly how accurate it is compared to more complicated reality. He mentions a couple of videos that go further. I've already posted one and will look at the other.



The second video is Mould and Matt Parker going through to find the most efficient packing for spheres - using ball pit balls. They then shift from tetrahedral packing to a more square packing - which turns out to be exactly the same (check the below video to see that they're the same). 

I'll warn you that the second video is a lot less professionally laid out and more heavily math-leaning. (There's a slightly more organized video that shows about the same content.) But Mould and Parker do cut a whole bunch of oranges trying to calculate the percentage of space occupied in the face centered cubic packing. (It an IRL version of a computer animation that we use in class and that I'm STUNNED to see I haven't posted on the blog before - coming in two weeks now.) We include a mathematical version of the proof at 16:55 in our summer camp powerpoint (at least Becky and I do - check slides 85 & 86) and you can find the math laid out here, too.

The last video is back to Steve Mould's channel and shows - using ball pit balls and a cardboard box - hexagonal (and face centered cubic) packing. They use that to demonstrate stacking faults (maybe defects, maybe disolcations, maybe grain boundaries - I need to figure out which term is most correct there), brilliantly shown with the color-coded balls from about 6:00-8:00.

The idea that the face centered cubic lattice is really and A-B-C (repeat) hexagonal arrangement whereas hexagonal close packing is A-B (repeat) is kind of mind blowing and so brilliantly well shown with the ball arrangement. The ABC diagram is a little weird to me and very much a mathematical diagram, something I wouldn't get into in class.

Discover the materials of the future...in 30 seconds or less | Dr. Taylor Sparks | TEDxSaltLakeCity

(Must refrain from making snarky comment about mustache...boots...slacks...)

Wait, the video is fifteen minutes long ( a pretty standard TED talk length, admittedly), but the title says "...in 30 seconds or less"). That feels like a serious disconnect.

I'm also a little disappointed that I don't know Dr Sparks because I've taught a material science camp at University of Utah (where he teaches) a half dozen times. I know a lot of the people on this page - but Dr Sparks seems to have eluded me for some reason.

In the above talk, Dr Sparks goes through the historical model of - as he says - "Edisonian trial and error" and serendipity (a la the discovery of saccharine) discovering new materials. He then transitions to our needs to discover modern materials in a more purposeful way via the Materials Genome Initiative and his research using machine learning to predict properties of materials either not yet created or with ingredients too rare to risk on trial and error experimentation. He refers to this field as materials informatics, a term I've never heard of before.

I think I'm going to hunt Dr Sparks down when I get out to Salt Lake (hopefully) next summer.