Metals with a Memory

Memory metals - nitinol being the one with which I am most familiar - are a fascinating material with their solid state transition radically changing the material's macroscopic shape. The old chestnut of turning a straight piece into a coil in hot water is nice, but the creativity of using metals with different transition temperatures to make a little sculpture here with uncurling biceps, straightening spine and neck, able to 'stand' straight up as the temperature rises is very well done.

Bouncing bearings on liquid metal

Advertising is advertising. I think we all know that.

And the advertising demonstrations set up in sporting good stores aren't always the truest indicators of a particular piece of equipment's final performance. Yes, the materials shown probably perform the specific functions being demonstrated very well. Here we can see that the rebound of a metal ball off of liquidmetal's proprietary alloy as compared to the rebound from a titanium surface.

We have to assume that all the other variables - material thickness, cold or hot treating perhaps - are the same between the materials and that the two metal balls are also the same. If so, we can safely say that the liquidmetal does, indeed, provide a greater rebound (coefficient of restitution if I remember my physics correctly). Now, what does that mean on the surface of a golf club, in a tennis racket, or as a fishing pole?

That I can't definitively say from the limited data I have before me. I am glad, though, that their website does provide a little of the science behind the fact that the alloys possess ' an "amorphous" atomic structure, which is truly unique. By contrast to the crystalline structure, no discernable patterns exist in the atomic structure of the unique Liquidmetal alloys. As such, properties superior to the limits of conventional metals can be achieved.'

Has anyone actually used anything from the liquidmetal line?

Galvanizing a Towmaster Trailer

Early this week the students at ASM's corrosion-themed three-day workshop (hosted by the University of Akron's National Center for Education and Research on Corrosion and Materials Performance - that's a mouthful) got to tour the AZZ Galvanizing plan in Canton, OH. There the AZZ folks gave a great PowerPoint (which you can see here - be warned, however, that it's a 150MB pdf of the presentation, kinda big) on the advantages of and science behind the hot dip galvanizing process - about which they might be admittedly a little biased. They then took the teachers/campers to see the process in action. I - as one of those campers - can say it was a pretty impressive sight to see, particularly as the steel light post was lowered into the molten zinc which began to spit and splash due to the temperature difference of the materials.

The finished post section practically glowed from the brilliant, shiny zinc coating as it was removed from the zinc bath. Great process to see in action and great protection against corrosion.

Thermite Reaction - Smash! Bang! Boom!

There's so much science hanging here in this remarkably simple-to-perform demonstration.

Steve Spangler - former elementary science teacher - her explains that the kinetic energy from the ball bearing's banging together turn into thermal energy - enough to burn holes in the piece of construction paper. He then goes on to show the far cooler - to me, anyway - reaction of iron oxide (the rust on the outside of the ball bearings) and aluminum. Most folks - if they know that reaction - know it as thermite (check a few thermite reactions here).

Typically, though, the thermite reaction involves mixing aluminum and iron (III) oxide powders in a flower pot or some ceramic vessel. The reaction is then started with a separate reaction (it has high activation energy) and then produces molten iron and a huge pile of sparks. It's outstanding to watch FROM A DISTANCE. That whole FROM A DISTANCE and the need for some second reaction means that thermite is typically reserved for high school and college chemistry classes.

Spangler - who didn't come up with the idea, by the way - brings the reaction into far more manageable form by taking a rusty ball bearing (covered in iron oxide) right up against one covered in aluminum foil. Same reactants...good energy to start the reaction (from the KE of the ball bearings)...great sparks.

Yeah, it takes a little practice to get the technique down right, but it's way safer than the big thermite reaction that throws molten iron all over the place. Plus, you get to clean up the rusty ball bearing in the process.

Al _(s) + Fe₃O_{4 (s)} --> Al₂O_{3 (s)} + Fe _{(s or l)}

We can look at this for...

• activity series - aluminum more active than iron, so oxygen goes to aluminum
• energy transfer - kinetic energy becomes thermal energy becomes chemical energy becomes light and heat energy again
• corrosion - We're un-corroding the iron in favor of the aluminum.
• electrochemistry - electrons are leaving the aluminum (so it's the anode) and going to the iron (so it's the cathode)

I am so happy that I just got myself a pair of these rusty ball bearings myself.

First day of awesome AP chemistry, here we come.



Update: If you're looking to buy yourself a set of these, Flinn Scientific offers a slightly larger version of these rusty steel balls (AP 6256) for (as of April, 2013, anyway) $26.60. Plus you get a couple of sheets of aluminum foil, which are easily worth like a thousand dollars or something. They also have a video on their site (that I can't figure out how to embed here)

Smack Me on the Head With a Shovel

Watching d30 at play (better in the video below) is like watching anybody play with Silly Putty. The explanation given (again, explained in the video below) is that the "intelligent molecules all band together upon impact...[to] absorb the shock and get hard."

Sounds like a pretty cool material and one that I need to get my hands on a sample of. Maybe a trip to Play-It-Again Sports is in need, 'cause this is a material I need to get my hands on.