Tuesday, April 30, 2013

Time Warp - Cornstarch

The Time Warp guys love running just about anything through slow motion and in front of high speed cameras. Oobleck is made for these guys.

Oh, first an actual definition (from the video, slowed down so you can read it) of what a Newtonian fluid is:
The resistance which arises from the lack of slipperiness originating in a fluid, other things, being equal is proportional to the viscosity by which the parts of the fluid are being separated from each other.
Yeah, whatever. Cornstarch and water make for some really fun stuff.

Like...sticking in your hands, running the hands across the surface, then showing it in really super slow motion.

Like...nailing a nail into a floating board (which is really cool to see, honestly).

Like...dumping it on a modified speaker (basically a drum head stretched over a cardboard tube, I think (and playfully mocking your own wedding).

Like...running across a pool of the stuff - and doing a hoedown on the oobleck.

Oh, at 4:20, how does the cornstarch mix flow? Shouldn't it be solidifying as it pours?

Oh, I'm about finished with the Spanish-language video. This one's way better quality and goes more in depth.

Plus it's in English.

How To: Forge Sterling Silver with Drac (metallurgy modding like a boss)

Debbie and I started to play 'count the mistakes' in Drac's explanations in this video.

Acetone torch? No, probably acetylene torch.

He wants the un-exposed pieces to slag with the rest of it? No, he probably doesn't want slag.

Why would he be using copper tongs? Copper conducts heat wonderfully. (Though copper does at least melt at a higher temperature, +1085C, than does silver, + 962C.)

I thought that saying he was annealing the silver and quenching it was contradictory, but the wikipedia article says otherwise "Unlike ferrous metals—which must be cooled slowly to anneal—copper, silver and brass can be cooled slowly in air, or quickly by quenching in water."

The thickness actually does not matter? I would think that it would matter.

[The silver] came out of the pickle? He put the silver in a gherkin? Oh, nevermind, he's right on that one.

I'm pretty sure they're troy ounces, not trojan ounces.

All that being said, he does end up with a few hundred bucks in his hand. Maybe he could use that to buy a better microphone so we don't hear his torch drowning out his voice.

How much pressure does it take to crush a concrete cylinder?

Great under compression, lousy under tension...concrete has its strengths. That's why we use it to build dams, buildings, anything that needs to withstand something really heavy pushing down on it.

This test, applying a million and a half pounds of pressure to a concrete cylinder isn't something that most of us - a few matsci teachers in Washington state, not withstanding - can't do in our classrooms, but it's the kind of thing that's well worth testing for a roomful of visiting kids and parents at your engineering open house.

Yeah, there's science there, but there's also wanton destruction. That's always cool.

How and Why to replace the Anode rod of a hot water heater

This guy's no Rich Trethewey, but he does a good job showing how to change an anode in a far tighter space - with the hot water heater actually installed as opposed to Rich's magic 'in the middle of my shop' heater.

This video kicks Rich's hiney in terms of the science explained. I love the test for electrical conduction at 2:50. It's a neat little check to show us that the cell ACME is in place. This video also goes into far more of the chemistry of corrosion from about 3:30 onward, especially writing the reactions for the oxidation of iron. I would've never thought of using an electrically powered anode for a hot water heater. I wonder where that might be required.

By the way, has anybody ever heard the phrase (from 1:22) that two things can be lying "side by each"?

Barricade Fire Gel on the DIY Network

"This is basically a do-it-yourself fire blocker..."

Yup, that's about right.

The comparison of the untreated and untreated sides of the 'house' is stunning, and the application of the sodium polyacrylate is absolutely brilliant.

I'm stunned that the host has the faith to put his Barricade-coated hand over the torch. That's some faith in the product.

If I lived in a different part of the country (not in southern Ohio, as I am), I'm thinking I would stock Barricade by the tankful.

homemade fireworks

Sometimes you just need a chuckle.

Yes, there's certainly a fair bit of oxidation and corrosion happening here, and I'm sure the energy being released is because the metals are returning to their more stable, ceramic forms, but this one's all about the deadpan delivery of the lines at 1:10.

"Holy smokes...a little too much magnesium, I guess. I won't do that again. Sorry 'bout that."

Out of curiosity, though, does anyone have any proof that this is - or is not - real? The man just seems a little too casual for me to entirely believe the veracity of the video. (other than just observational, assumptive data - like his shirt changing color)?

Chemistry of Concrete - Periodic Table of Videos

How can you not love the narrator/professor from the Periodic Table of Videos? His upper crust British accent, his halting delivery, his shock of white hair (sadly under a hard hat here), and his periodic table ties all make him an endearing character.

His explanation of the making of concrete is nicely simple and well laid out...

calcium carbonate ---heat--> calcium oxide + carbon dioxide

calcium oxide + sand (silicon dioxide) + aggregate (stone) + water ---> concrete

From there, the silicon dioxide and the calcium oxide make (from 2:21) "a sort of jelly that gets harder and harder." This 'jelly' then reacts with the carbon dioxide from the air to get even harder still, reacting over hundreds of years to react a final hardness.

Then the professor goes through the differences in concrete strength under tension and compression, explaining how adding in the steel reinforcement to overcome the material's weakness in tension.

There's even a great, if quick, explanation of the environmental issue with creating carbon dioxide in the process of producing the calcium oxide.

Very well done, professor.

Houghton on Forging

This industry-produced (Houghton forging) is definitely pro-forging, but it's also nicely informative, showing many of the places where forged materials are used.

We also get some of the advantages of forged materials listed, as well: strength, resistance to impact and fatigue, reliability, low cost, fully recyclable. They do stop short of claiming any sort of medicinal benefits of forging materials.

The latter part of the video - focusing on Hougton's fluid management business (fluids used in the forging industry) certainly touches on an area of forging that I had never considered.

Saturday, April 20, 2013

Graphene aerogel is the new world's lightest substance

As research into aerogel continues, scientists are discovering ever-lighter variations. First, there was carbon nanotube aerogel, with a density of 4 milligrams per cubic centimetre. Then along came silica aerogel, which weighed in at 1 milligram per cubic centimetre and garnered 15 entries in Guinness World Records. It was ousted by metallic microlattices, at 0.9 milligrams, and then aerographite, at 0.18 milligrams.

Now, a new graphene aerogel created by scientists led by professor Gao Chao at the Zhejiang University has swept past, weighing in at just 0.16 milligrams per cubic centimetre
The original article is from Nature, but only an abstract is viewable online for free, sadly. The full article takes a little bit of money that I'm not willing to spend ($8 for the one article or $199 for a year's subscription). Luckily there is a decent enough report on CNET Australia's blog (the source of the above quote).

Aerogels are odd, weird substances. I have a piece in a plastic container that I've taken out a few times to hold it. Each time it feels like I'm holding a solid and a gas at the same time. It's a contradictory feeling, a real-life discrepant event without a trick. The aerogel that I have - now snapped in two by another ASM master teacher, arggh - is a silica aerogel (available from Educational Innovations, one of our summer camp sponsors) which means it's something in the order of six times more dense than is this new graphene aerogel.

I, of course, want some of the new stuff.

Because it's the newest...

PS - There are other possible sources for the purchasing of silica aerogels - United Nuclear (small pieces in semi-bulk only), ebay (including, as of today, a huge 220cc sample), ThinkGeek, and BuyAeroGel.com.

Simple Golf Tip

The Turbo Encabulator is a brilliant bit of performance gibberish. It's also our standard opener at the ASM summer workshops. We use it to illustrate that technical language without context, without understanding, without meaning is useless. Yes, you can describe the marzul veins and the pre-framulated amulite, but that doesn't mean those things exist or mean anything at all.

And just because you know to snap load your power package that doesn't mean your power cumulator isn't going to break down.

Personally, I'm partial to grip it and rip it.