Materials Day 2009 at MIT

Today I skipped a music class and XC practice to go to a day long Materials Day symposium at MIT. It consisted of the following presentations:

1: "New materials for PV modules: Cost, Performance and Reliability" - Let my preface my reaction to this talk by saying that I believe that I do not have a future in photovoltaics. I find it not very interesting, and not related to materials science in ways I find interesting. Thus, I didn't find this talk very exciting, and, being the first of the day, it may have been all I could do to stay awake.

2: "Nanostructured Heat Transfer and Energy Conversion Materials" -This presentation was probably my favorite. I was wide awake for all of this. It described a certain system consisting of a p-type semiconductor and an n-type semiconductor, each attached to two different plates. Then, if you create a temperature gradient between the plates, it creates an electrical current. Conversely, if you put a current through the semiconductors, you can create a temperature gradient! So this talk was all about this technology and the search for a material with high electrical conductivity and low thermal conductivity, and various methods for achieving and optimizing this.

3: "Progress and Challegnes in Solid-State Lighting" - All about LEDs. Not very interesting. A lot more semiconductor and electricity stuff.

4: "What's Exciting about Excitonics?" - This one seemed pretty cool, although I understand any of it really. It was about these things called excitons, which I guess are energy carriers of some sort? 

5: "Nano-structured Materials for Next Generation Fuel Cells" - This one wasn't terribly interesting, but I liked the speaker. However, he mostly just talked about how his group tried this and they got some unexpected results and it was cool and all but not useful so they tried this instead but then they got these unexpected results which were also cool but not useful. 

6: "The "Materials Genome" Project at MIT: Accelerated and Large-Scale Materials Discovery in the Energy Field" - This talk was fantastic. This guy is heading a group at MIT that is trying to computationally characterize and predict the properties for as many materials as they can (generally single-crystal crystalline materials of various compositions). The things they can do and have found are amazing. I think that this sort of sorting and computational prediction of the structure and properties of materials will become a lot bigger in the future, especially when computational power increases. 

7: "A123systems Li-ion batteries: from Nanotech to Reality" - This talk was pretty good, all about how this MIT spin-off company, A123 Systems, grew and became successful. They make lithium ion batteries. I find I liked the part of the presentation about the company and the entrepreneurship better than the information about batteries, as again, it's a lot of electronics related materials science.

8: "Creating and Funding Startups: A Venture Capital Perspective" - This talk was given by a venture capitalist all about what venture capitalism is, how it works, what they look for, etc. Very interesting.

After the talks was a poster session and a dinner, both of which I did not attend as I needed to get home and get a lot of work done. The talks that were interesting, I really enjoyed, and I'm very glad I went. 

Flamecutting and Grinding!

I learned two exciting new skills in my welding class yesterday, flamecutting and grinding. 

Flamecutting is certainly interesting. At times a bit more scary than fun. Basically, you have a nozzle with 9 holes, eight on the outside and one in the center. The outer 8 are for preheating, and the center one is for the actually cutting. The center hole is only used when you depress a lever on the side of the nozzle which I believe completely opens up the path for oxygen, which saturates the flame with oxygen making it very hot but also making it such that it will oxidize the steel. With flamecutting, however, this is not a worry because you are removing all of the steel that contacts the oxidizing flame.

The removing part is where it gets exciting. After preheating the steel up to about a yellow hot, you depress the lever and the flamecutting flame comes out and it is hot enough to instantly melt the steel, and the pressure from the gas from the nozzle shoots the melted metal away in a shower of sparks. Where do these sparks go? Why, directly away from the nozzle, of course. It's because of this I've learned to always try to flamecut away from yourself. Also I've learned to always have your pants over your boots, to avoid having hot pieces of metal fall into your boots and sit their for a while burning you.

It gets better, though.  Sometimes you have what's called a blowback, where instead of going away from you, pushed by the gases of the nozzle, the melted metal explodes outwards in all directions, and often makes an extremely loud and sudden popping noise. My guess is that this is caused by a pocket of air in the metal that, when heated up to quickly, explodes, causing the metal to behave much like several thousand degree hot liquid popcorn. This happens most of the time if you try to flamecut over an area that has already been cut. This is a tempting thing to do, as occasionally, if the part of the metal that was just cut stays too hot, the steel will fuse back together. 

And, just to add to all this, it's really hard to keep yourself steady if, like me, you're naturally a shaky or trembling person. This causes all your cuts to turn up looking like tiny zig-zags.

But, thankfully, this is why we have grinding tools. After having done a good bit of flamecutting, we were introduced to the 4 and a half inch grinders. These are somewhat crazy power tools that you plug into the wall, and when you turn it on, it will spin a 4.5 in. diameter disk really fast, fast enough to create a nice breeze, which you then put up against steel. What happens then is that some amount of steel is converted into a 15-foot jet of sparks. Yes, 15 feet, and, Yes, a jet. And these aren't all harmless little sparks, several of the things that shoot off the grinder are decent sized particles of hot steel. Luckily, most of the time, this just is facing away from you, though, depending on the side of the grinder you use, it can be facing you, and there are always little bits that get whipped around and towards you. The little devils get everywhere too. They've been known to light clothing on fire, light paper nearby on fire, and even bounce their way under your safety glasses and into your eye. Again, I try to avoid sending the stream in my direction.

This grinding, however, is extremely useful. When flamecutting, you'll often accumulate little beads of melted metal that are blown onto the sides of the steel. These little beads are no longer steel but are rather, because of the oxidizing flame I mentioned earlier, slag. The grinder is great for getting them off. The grinder also can smooth down the rough edges that all your trembling makes while flamecutting. Even more, the grinder can polish the metal and expose bright shiny bits under the black oxide coating, making the steel look a lot nicer. 

I think I can look forward to a lot of grinding in my future. 

Visit to the SEM

Last Thursday my boss took me on a trip to a scanning electron microscope nearby that we had rented some time with. He wanted to check some carbon residue for carbon nanotubes, and to examine the epitaxy of a certain grown sample.

First, we looked at the carbon residue. It looked like soot, and under the SEM it looked very disorganized and splotchy. However, we did see some carbon nanotubes. They looked like white strings in the SEM. There were not as many of them as my boss had hoped, but it was still cool for me to see what a carbon nanotube looks like under and SEM.

The next sample was ever cooler. First we got a look at some crystals. We wanted to see whether they were arranged epitaxially, which, unfortunately, they were not. It was still cool to see the crystals up close. When we zoomed in further though, past the large crystals and into about a 100 nm scale, we saw odd shapes that looked almost like olives. This was really cool because we have no idea what they are, but we believe they may be some odd arrangement of carbon. Hopefully we will figure out soon what it was we saw, it could be some exciting discovery!

Physics!

I'm finally getting to the calculus in physics, too! Yesterday I watched the lecture on pendulums, springs, and simple harmonic oscillation, (the one where Walter Lewin rides a pendulum across the room to show that its period is independent from mass) and today I watched the lecture about work and energy.

The SHO lecture has a little bit of calculus, mostly pretty simple and used to manipulate terms to get equations. The equations I had all seen before, last year in honors physics. However then we had just been given them, with little to no explanation of where they came from. Now that I've seen the math, I can understand the concept and reasoning behind the equations.

With work and energy calculus was deeply involved, using integrals and some manipulations to derive the equations we had again been given without explanation last year. This was then taken further when the calculus was used to understand work, energy, and gravity in three dimensions, something that had not been touched upon last year. 

This is the physics that I really enjoy. 

Calculus!

Last night was the fourth class of the Multivariable Calculus class I am taking at Harvard Extension, and we're finally doing calculus!

Pretty much everything up until now has been vectors, geometry, and parameterization, all necessary to learn pretty well before we actually got to the calculus, but to me it is less interesting and less fun. Last night though we got to partial derivatives, and velocity and acceleration vectors. 

Beauty.

Welding Class 2

Last night was my second welding class. Last class was all safety and a tour of the facilities, but this class we actually got to weld! And it was so much fun!

First we cut ourselves a bunch of pieces of steel. They were shaped like isosceles right triangles without the hypotenuse. Then we watched the instructor demonstrate the welding, and then we ourselves did it. It's not a short process, and a steady hand and patience are a huge help, but it's still a lot of fun! After most people had done their first weld, the instructor proceeded to show us to weld using a filler wire, which is a copper coated steel wire (The copper is used to protect the steel from oxidation. It burns away as soon as you heat it up in the flame. If the steel wire oxidizes it can weaken the weld) that you use to fill in gaps in the weld if the two pieces of steel are too far from each other, which happens since we're not always welding straight edges or perfectly cut steel.

I think that this class will absolutely be worth all the difficulty of getting into Boston every Tuesday after a cross country meet and not getting home until after 10.

Knifemaking

I took a class this weekend at Prospect Hill Forge in Waltham called "Nothing but Knives."

It consisted of three three-hour sessions. The first was a practice knife where we used mild steel (steel with about .16-.29% carbon) and the instructor taught us all the parts to making the knife. This was mostly review for me since I had previously taken the Simple Knives class there which was essentially the same thing.

The second session we made the real knife, using high carbon steel (about .30-1.70%. What we used was probably around .8-.9%) which is much harder than mild steel. It heats differently and fights back more when being smithed. 

The most interesting part, however, was after we had finished hammering the blade, and we annealed it. The instructor had a basic understanding of the metallurgy behind much of this process, and so he told us about it. Some of it I knew already, but some was new. For annealing, we heated the blade up to the point where the whole thing was hot enough to change from a Base Centered Cubic crystal structure to a Face Centered Cubic structure, called austenite. At this point the steel also ceases to be magnetic. I don't know why, though I sure would like to. After we have heated the blade to this temperature we placed it into an ash bed and left it to cool overnight. The slow cooling allows the steel to form large grains, making it very soft.

In the third session we came in and removed our knives from the ashes. We wanted them soft so that we could grind and file them easily. So we proceeded to grind and file for quite a while. This is mostly what makes the blade, since you can't get it sharp enough to cut anything with a hammer. After lots and lots of grinding, when we have a decently sharp blade, we begin the tempering process. This starts with again heating the blade up to an austenite temperature, and then cooling it rapidly in a vat of oil. Not only does this make it very hard and brittle from the rapid cooling, but gives it a nice oil finish.

After this comes the main tempering. A really hard brittle knife isn't so good, since it can be brittle enough that dropping it on the floor might shatter it. Also it would be really really hard to sharpen. So we took large metal clamps, heated them really hot, and then held them against the back part of the blade. 

At this point our instructor explained to us tempering colors. Steel will, starting at about 300 degrees, start showing colors. It starts with a light straw color, goes to bronze, then brown, then purple, then deep blue, then a bright teal color. It's pretty dramatic. His theory as to why this occurs is that a very very small oxide layer forms, small enough to be transparent, but still diffract the light, creating the colors. He's not sure about this, though, so it would be a cool thing to check. This is useful because it can tell us what temperature the blade is at. We hold the hot clamp on until the blade becomes bronze. We then quench it very quickly. The purpose of this is to leave the blade hard enough to hold and edge but soft enough to sharpen well and not break off. After the tempering comes some final sharpening, and then you have a finished knife!

The class was great, and lots of fun, especially since I learned not just how to make a knife, but much of the materials science behind it!

Below is a picture of the knife I made: