Friday, July 31, 2015

10 mind-blowing man-made materials

Admit it, you're every bit as susceptible to list videos (and internet posts) as I am.

We all must be, otherwise we'd probably lose a third of the internet and be left with just cat videos and pictures of pretty people.

This video is severely lacking in detail for each of the "ten mind-blowing man-made materials", but it would be a great starting point to get your class thinking about the Materials Choice Award.

Drought taking toll on SF's aging sewage system

I am going to eschew any jokes here.

No jokes about this situation gags about chuckles about rotting eggs...

Honestly, though, the idea that decreased water usage in our flushing habits could be bad for the cement in the sewers (less water with the same volume of 'organic matter' means more hydrogen sulfide produced in the pipes) is stunning to me.

Check out all of the filthy details on KPIX's website.

Shimmery sea sapphire disappears in a flash

An invisible car, I don't get.

An invisible animal, I get. That would be the best camouflage ever, just turn slightly to the side and go all Kate Moss on your predators.

The color is due entirely to the distance between crystals in the sea sapphire's back, causing it to look blue when seen directly on but to shift its 'color' appearance into the ultraviolet range when it tilts slightly and shortens that wavelength.

The full science is summarized in an article in New Scientist and originally in Journal of American Chemical Society.

How to make the mini metal foundry

There's pretty much nothing better than melting metal in the backyard (or maybe on the patio, wouldn't want to set the dry grass on fire out there, folks). And aluminum isn't a bad choice since it has a relatively low melting point for a metal.

Plus, lots of us have ready supplies of aluminum just sitting around in the recycling bin (because we wouldn't ever throw an aluminum can away, would we?)

In this trilogy of videos, the King of Random shows us how to make a backyard foundry, melt and purify aluminum, and then cast something via lost foamboard casting.

Looks like a blast.

Using bacteria to make self-healing conrete

Poop has been useful for a long, long time. As a long ago resident of Terre Haute, I know that.

Heck, it's even been a building material before, but the use of bacteria that produce a waste product of limestone to 'heal' concrete is brilliant. Once the bacteria - encased in the cement - is rehydrated, it releases calcite which seals up the crack, sending the bacteria back into hibernation.

Thanks to Andrew Fishback, one of our Cincinnati campers, for sending this my way.

Sunday, July 26, 2015

Fountains of Chain: Science Take: The New York Times

I've never tried to demonstrate the bead chain demonstration (available from Educational Innovation for about $20, though I'll admit that I'm looking for longer, cheaper beaded chains) from more than a couple of feet off the ground. That height gives a jump out of the beaker of about five inches or so. Supposedly, though, a longer drop (from a balcony, a second or third story, even) will provide an even higher jump out of the container.

Why, however, does it provide that jump above the lip of the container? That's a little more complicated.

The video above says it explains that jump, but I got a heck of a lot more out of the video below.

Friday, July 24, 2015

Today's material science quote...

Today's material science quote from master teacher, Rebecca Heckman  (shown above moments after the quote)...
I'm betting that in the future, we'll still be using stuff made of things. 

Thursday, July 16, 2015

Carbon-fiber epoxy honeycombs mimic the material performance of balsa wood

Balsa wood?

Seriously, the blades of modern windmills are filled with frickin' balsa wood?

That's the fancy level of modern technology that we're working with to replace coal and natural gas and hydroelectric power?

It's not really a surprise that materials engineers are looking to replace balsa wood with something a little more reliable.

Check out all the details in the article or see the research group's video above.

Memory alloy that bounces back into shape 10 million times

Admittedly, I'm a bit far from testing any of my samples of NiTiNOL ten million times, so I can't guarantee that my metal samples don't survive ten million cycles.

Professor Manfred Wuttig, however, seems able to make an actual claim that his new memory alloy (NiTiNOL doped with some copper), can survive ten million cycles.

And that's certainly something. In fact, it's the kind of something that makes a memory alloy far more useful. See, most memory alloys return to their shape above their transition temperature, but every transition sees the sample adding dislocations to the original shape during the transition leading to eventual functional fatigue and a change in the transition temperatures. After only a few transitions, the sample is less and less back to its original shape. A sample that can return to its original shape for ten million cycles, though, is a significant breakthrough.

Check out one of the these articles covering the original research...

Where to buy a kiln

At the ASM teachers camps, we use kilns from Seattle Pottery Supply.

We like the front loading kilns and lean toward the 120 volt versions with the digital controllers because they're programmable - allowing for particularly ramp rates, hold lengths, and delay starts. If you ever get stumped, the digital controller looks like this, and its manual can be found online here.

The 120 volt kilns do require breakers with at least 20 amp capacities. You'll know if your circuit has that if it looks like this.

There are other kiln sellers, of course, but make sure to check that your electrical circuits have the right capacity for what you're ordering, that you're getting a front loader (that's the side-swinging door, not the up-and-down guillotine option), and that you're getting a programmable, digital controller. All of that should add up to a good raku experience.

Oh, and while you're at it, throw a piece of Fiberfrax paper on the bottom to protect your kiln from any dripping glaze.

Modern marvels with Ainissa Ramirez: Space Shuttle Ceramics

I think Anisa might be over-simplifying things at 0:44 when she says the thing that keeps the Shuttle from heating up is as simple as sand, particularly not sand as dirty as she shows right after that.

And, at 2:00 when she pours water onto the tile, it looks more like she really pours the water onto the metal ring above the tile. Yeah, the water sizzles there, but I can't really tell how much of the water hits the tile itself.

Wednesday, July 15, 2015

Engineering the Strongest Foam in the World

I'm not sure I would want the metal of my boat to look like the Swiss-cheese-ish piece of metal in the video still above. It just wouldn't instill confidence from me and - I would imagine - my fellow passengers.

Still, the decrease of weight without subsequent decrease in metal strength is a fairly perfect pursuit for research, particularly as it's being undertaken by Nikhil Gupta at NYU Polytechnic.

Check out either of the two articles that cover the same content as the above video and start getting ready not to worry about the 'holes' in your boat.

Compound Bars

The bimetallic strip is a tried and true demonstration of thermal expansion. It's available from all sorts of sellers (Flinn, Arbor Sci, bunches of other places). Invariably, though, the bimetallic strip (also known as a compound bar) is exactly the same from every seller. Yeah, the handle changes, but the metal strip is exactly the same - brassy on one side, silvery on the other, curving toward the brassy side.

This summer, though, I went searching to see if there were other bimetallic strips available, other combinations of metals to demonstrate.

It turns out that there are...sort of...

The four bars above are available from Arbor Scientific, but they come with a bit of a warning.

Of the three customer reviews on the Arbor Scientific page, one is pretty solidly and simply negative, "These pieces are just poorly made, and do not work at all. They are riveted together and tend to buckle instead of bend."

Yup, you can see clearly that those four compound bars are riveted together not smoothly joined as the more common bimetallic strip is. Clearly there's some reason why the cheap and omnipresent bimetallic strip is so omnipresent. It works. The two metals are - assumedly - easily and permanently joined.

Has anybody bought or used the four-bar set? If so, what are your experiences?

If anybody wants to see a couple of nice videos explaining the compound bar, check these...

Mizuno Grain Flow Forging: Factory Tour

Chris Voshall walks around during most of the video. It wasn't until I watched the video for a third time that I saw his title, "Golf Club Engineer."

Not that there's anything wrong with faking being a golfer or anything. Heck, I've been doing it for years. (ba da bum - rimshot!)

Seriously, though this video does a brilliant job explaining the forging process from billet to primary forging through trimming (and repeating the process) and in explaining why forging works (see the wood splinter/metal crystal grain analogy at about 0:40).

(By the way, that whole "I've been doing it for years" is a lie. It was just too easy a joke to make, though. Really, I'm pretty much just into frisbee and miniature golfing. In total, I think I've played 27 holes of real golf. Thanks, Brian and Brian for taking me out for those two rounds.)

The Difference Between Casting and Forging

That's a simple enough title for a webpage - the difference between casting and forging - but it's a terrifically important topic, so I greatly appreciate that ATC group (which provides both cast and forged parts, so would seem to be willing to provide neutral and positive spins on both processes) has put together a great summary on the two topics.

I'll give just a taste of the simplicity by showing their casting information...
We use castings for a wide range of wearparts and components that are too large, complicated, intricate or otherwise unsuitable for the forging process. We can forge parts up to 50kgs but the sheer energy required to forge larger items make casting a much more viable alternative.

We currently cast mining and earthmoving components to 580 kg. We can cast up to 3000 kg if required. Manganese work hardening screens are one of our specialities. We have found that by carefully choosing alloys and applying proven methods of heat treatment, we can produce castings of high quality, strength and wearability. The casting process better lends itself to making parts where internal cavities are required.
The advantages of casting include:
  • No real upper size limit in casting weight
  • Large range of alloy choices
  • As forgings remain solid, custom alloys are far more difficult to get into production whereas with casting, alloys including Chrome, Nickel and Moly can be added at the molten stage.
  • Tooling is often less expensive than forge dies
  • Smaller production “runs” required
  • Complicated/complex parts are no problem
For general GET as well as large and complex components - casting is a fantastic method of manufacture.

You'll have to visit the webpage to see why you should forge parts.

Why does glass turn purple?

A year or so ago, my mother - a frequent visitor to the American Southwest in the course of her life - asked me if I knew why glass would turn purple if left in the sun, particularly in the intense sun of the Southwest.

It wasn't something that I'd heard of before, but I'll admit that Mom's spent more time in the Arizona sun than I have, so I went a'researching.

In material science we discuss additions to glass - to lower the melting point, change the thermal expansion, widen the softening range, further dull the electrical conductivity, improve the sparkle, change the color, improve the strength. These additives each have their own historical profiles due to research, economics, politics, environmental concerns.

Here I'm going to quote liberally from the Corning Museum's article on solarized glass...
The major constituent of most glasses is silica, which is usually introduced as a raw material in the form of sand. Although silica itself is colorless in glass, most sands contain iron as an impurity, and this imparts a greenish tint to glass. (In ancient times, glassmakers used very impure sands, with iron contents higher than those of sands used today, so most ancient glasses have a pronounced greenish color.)

By adding certain other ingredients to a molten glass, it is possible to offset the greenish color and produce colorless glasses. Such ingredients are known as decolorizers, and one of the most common is manganese dioxide (MnO2). In chemical terms, the manganese acts as an oxidizing agent and converts the iron from its reduced state (which is a strong greenish blue colorant) to an oxidized state (which has a yellowish, but much less intense, color). In the course of the chemical reaction, the manganese goes into a chemically reduced state which is virtually colorless.

Manganese dioxide is believed to have been first used as a decolorizer as early as about the second century B.C. It was probably introduced as the mineral pyrolusite. From Roman times onward, glasses often contain about 0.5% to 1.0% manganese oxide (MnO). Later on, manganese dioxide (MnO2) was sometimes called "glassmakers' soap."

If pieces of decolorized glass containing reduced manganese are exposed to ultraviolet light for long periods of time, the manganese may become photo-oxidized. This converts the manganese back into an oxidized form, which, even in rather low concentrations, imparts a pink or purplish color to glass. The ultraviolet rays of the sun can promote this process over a matter of a few years or decades, thus accounting for the color of desert glass. The effect has been reproduced in the laboratory.
The article also mentions that selenium and cerium oxides can also solarize in glass but to an amber or light brown color.

Dumpdiggers (an antique blogger - or rather a blogger about antiques, I don't know that he's an actual antique) writes about a different process through which this solarization can be recreated on a shorter time scale...
Sometimes called desert glass, or sun-colored amethyst glass, these pretty purple bottles are fake; their color is artificially produced by gamma radiation in a lead lined chamber by an unscrupulous merchant with one motive – profit.


When exposed to the radioactive isotopes Cobalt-60 and Cesium-137, most manganese glass will turn amethyst, while glass made with selenium will become either straw, wheat, or honey colored.

Dumpdiggers then links to a fairly scientific article on the National Insulator Association's website addressing these concerns about artificially inducing colors in glass insulators, including a practice of heat treating solarized (naturally or artificially) glass insulators...
Exposure to high levels of heat will reverse the sun’s ultra-violet purpling effects on glass. This procedure is often referred to by collectors as “cooking”. During the thermal reversal or “cooking” process, the manganese is once again the key stimulant. In most cases, when a sun “purpled” insulator is heated to high temperatures, generally a step below melting, it will revert back to a shade in close proximity to its original manufactured color.


Our final category of alterations involves exposing irradiated insulators to high levels of heat. In some instances this creates a secondary altered color, much different in appearance to the primary irradiated color. During one of our numerous experimental procedures, one particular pony insulator was first altered from its original color of light blue aqua to a burnt olive brown. This same insulator was then subjected to extreme thermal exposure, transforming to a medium shade of cornflower blue.   We know that some of the unscrupulous new era “nukers” are using this same process to dial in colors that very closely mimic authentic insulator colors, and with considerable accuracy. Even though such color duplications look authentic, they are, of course, outright frauds. These “chameleons” can be very difficult to identify.
We are currently looking at a possible method for identifying irradiated insulators that fall within a specific color range. As we know, natural purple or sun colored purple glass insulators contain manganese. Generally, the darker the purple the more manganese content in the glass. Manganese is very sensitive under a black light, providing a yellow to greenish yellow glow. The glowing intensity of authentic purple insulators is fairly easy to measure with the human eye, particularly after viewing several examples with a long wave black light in a completely dark room. We have found that most irradiated purple insulators display a diminished glow when compared to authentic purples. We have also noted that some of our insulator samples exhibited good black light glowing characteristics prior to radiation exposure, then deadened under a black light after radiation exposure. We are continuing our testing with this method and hope to have more validated and expanded information in the near future.
I find all of this absolutely fascinating and a wonderful application of the multivalent colors of manganese. For collectors, though, this is clearly a hugely decisive issue.

I kind of want to buy a few cheap glass insulators to line my classroom's windows now...and I kinda want some two-tone ones...

Saturday, July 11, 2015

The Elemental Composition of Metal Alloys

Green gold...white gold...chartreuse gold...yellow gold...royal blue with a hint of pink gold...

Are there any colors that can't be used to describe gold?

Compound Interest just posted a great graphic showing the metals in a number of common alloys - along with ranges for each metal's percentage composition within that alloy. Plus the page also has some explanations of just what alloys - particularly substitutional and interstitial alloys - are.

Great info...