Friday, June 27, 2008

Miracles

6/27
Ram had said that no matter how many times you see it, the Meissner effect is miraculous. Today, we made a breakthrough in our progress, and the sight of it shocked everyone who saw it.

After a series of trial and error approaches to making a track of magnets that could levitate a superconductor pellet as well as be a useful path for the superconductor to move across, we finally saw patterns and got systematic about things. The following is an outline of our thought process and how we got here.

We found that only two sides of the magnet would levitate a superconductor. The other four would not. We marked these sides with a dot, and they correspond to the poles of the magnet. Also, we found certain orientations of four magnets that could levitate a superconductor with high stability. Other combinations of four magnets provided no stability. The superconductors were just bounced off.

Also, we noticed that when a set of magnets that would not hold a superconductor steady were placed in series, on a few occasions the superconductor would move independently down the "track" as if propelled. This was not a controllable process, but there were times when it would move down the middle of the track with moderate stability. We figured that there must be something about those orientations resulted in the magnetic field lines causing the superconductor to move.

After several trials and more than several errors, the lack of consistent results was frustrating. We got a quick lesson on magnetic field lines from our mentor, Brent, and decided that we should codify the individual magnets to determine which of the levitating sides were the north and south poles. Although slightly monotonous, this was a key step in the miracle alluded to at the beginning of this post.

To determine the poles of the magnets, we used compasses. A quick anecdote on obtaining a compass:
I needed to buy a compass in order to determine the poles. My wife suggested Target, so that was where we went. When I started to walk toward the camping and sporting goods section, she said that we should try the party section first. Incredulous, but not being a complete contrarion, I went along not expecting much. The first thing we saw when we got there was a set of four compasses. Presumably, if you want to throw your child a pirate themed party, a compass is the way to go. So I bought a set of four for $2.39. I decided I wouldn't doubt my wife for a while.
On Friday, 6/27, we spent a fair amount of time determining the poles of magnets. The track was created to be two magnets wide, with the magnets on each side of the track having the same polarity. This proved to be a working track that would maintain levitation, and if given an initial push, the magnet would move down the track. However, it was unstable, and any left-right motion would bounce the superconductor off its course. About mid-day, one of our mentors, Josh, had an idea. He started to add a third row of magnets to the track. The alignment of the rows alternated S-N-S. This produced astonishing results. The levitation was stable, and when propelled by an initial push, the superconductor would move down the middle of the track.

The levitation and movement was so astonishing that the first time we saw it, everyone in the room gasped. This all happened last on 6/26-6/27. After several days of frustratingly slow progress, seeing the stable levitation was quite encouraging and I am hopeful that we can accomplish our goal. We'll see.

video

In the video, you can see the pellet stop. The length of the track has a consistent S-N-S arrangement across its width. At the end, the orientati0n was changed to be N-S-N. That alternative causes a stop in the movement. We have gone through some thinking about the field lines that is causing it, but we're not entirely sure.

Thursday, June 26, 2008

Playing with Superconductors

6/25
With the post-annealing process suspended for a few days as the oxygen tank arrives from being ordered, we had some down time. Some YBCO had been prepared by another member of the Seshadri group, and Ram had just bought us an impressive set of magnets. After obtaining some liquid nitrogen, we had enough materials to start playing with them trying to work on the construction of both the magnetic track and the vehicle that would be levitating.

The day itself was rather unstructured and really was playing with the materials, however with a purpose. The first time that the superconductor sat hovering over the magnetic track, seemingly sitting on an invisible platform was a truly remarkable site.

From the day's work, several ideas were tried and dismissed. Others were attempted and failed miserably. Some ideas showed signs of progress. I anticipate that the construction of the vehicle will become more sophisticated, and the more we experiment with the materials, they more we will understand their properties--intuitively if not theoretically.

Conclusions:
-The cylinder styrofoam we bought is porous and leaks liquid nitrogen. If used, a lining may be necessary. However, the square styrofoam is dense enough to hold a liquid. (Picture is a styrofoam boat lined with plastic, containing a superconductor pellet that is levitating a small magnet)

- The YBCO will levitate through a styrofoam barrier. When YBCO was placed in a styrofoam boat with liquid nitrogen, it levitated and the styrofoam could be moved freely between the pellet and the magnets. Thus, the pellet does not necessarily need to be directly over the magnets. There can be a thin substance between them.

- Getting lift from the YBCO will be difficult. We can get it to levitate, but engineering a vehicle that will experience lift was a struggle. The YBCO will need to be attached to the vehicle so that they move as a unit. Also, weight will be an issue.

Prep for post-annealing

6/24
Today was a slow day in terms of actual lab work. The slurry that had dried overnight was taken out of the oven, re-ground using a mortar and pestle until homogeneous. It had changed from a dark black mud to a gray paste. Strangely, though, when it was re-ground with a mortar and pestle, the color became black again.

Fortunately, we remembered how to press pellets from a few days earlier, so we were able to work somewhat independently to press the pellets for post-annealing. Until now, our inexperience with Materials Lab research techniques, procedures etc had rendered us dependent upon our mentors to tell us what to do. There was a nice sense of accomplishment at being able to work alone. I suppose its like that at most new jobs. Once the training phase is over, people settle in and can work for themselves. I don't think we are quite there yet, but it was nice to get a taste. Five total pellets were made pressed (four with a mass of 1.0 g, and a last with 0.50 g)

Once the pellets were pressed, our day in the lab was pretty much done. The oxygen tank necessary for the post-annealing was not available, so the last phase of YBCO prep will have to wait. The rest of the day was spent brainstorming ideas and looking online for some examples of what we were trying to engineer.

Tuesday, June 24, 2008

Lab Book- Synthesis of YBCO

This is the abridged version of what I have done so far. The other posts have my thoughts, and musings on this project. This post will be more succinct and a quick reporting of procedures.

6/19
Obtained the following masses of reactants:
0.8483 g Y2O3
2.9622 g BaCO3
1.7900 g CuO

Combined the reagents and ground into homogeneous powder with mortar and pestle.

Transferred powder to jar mill, added zirconia beads and ethanol (solvent)

Set apparatus to mill overnight

6/20
-Removed slurry and balls from jar mill, placed in large glass petri dish
-Rinsed milling bottle with ethanol to remove slurry stuck to walls
-Placed petri dish in 120 degree oven to evaporate solvent.
-Removed dry petri dish

-Using forceps, remove jar mill balls and rinsed with acetone to recover mixture stuck to the balls. (mostly ineffective)
-Placed petri dish in oven to evaporate acetone.
- When dry, set to cool, scraped powder from petri dish onto weighing paper

-Made 4 pellets (approximately 1-1.5 g each)

-Crucible and pellets set to react in furnace (48 hours at 930 degrees C, ramp 5 degrees/minute)

6/23:
- Removed pellets from furnace (color change from gray to black)
- Ground with mortar and pestle
- Verified phase with x-ray diffraction

- Made 3% by mass solution of poly-vinyl alcohol in DI water
- Added 5-6 drops of solution (PVA did not dissolve completely, used magnetic spin and extracted solution using pipet)
- Homogenize YBCO and PVA into slurry (added some DI water)
- Placed in 60 degrees C oven to dry overnight

6/24:
- Re-ground with mortar and pestle
- Pressed into 1.0 g pellets

6/27: (lapse in days due to lack of oxygen available)
- Post-anneal in tube furnace (oxygen flow)
Vessel: alumina boat
48 hours at 940 degrees C
Gas flow: 1.0 mL per minute

6/30:
- X-Ray diffraction of sample

7/1:
- When testing Meissner Effect, levitation of pellets was weak.
- Re-annealed in oxygen
40 hours @ 940 degrees C
Gas Flow: 1.5 mL per minute

7/7:
They work!!!

- Started Batch #2 (similar preparation with only a few slight differences)

Changes:
- Perform PVA treatment after first annealing
- Use alumina crucible rather than boat (prevent pellets from sitting against alumina during heating- remove chance of some interaction between alumina and pellets)

Reference used for this synthesis:
She, J.L. & Liu, R.S. J. Chem. Educ. 2008, 85,825-826.

X-Ray Diffraction and PVA treatment

6/23 AM
Today, with much anticipation, we removed the sample from the furnace that had ramped back down to room temperature. There was a distinct color change from gray to black. The samples had the appearance of looking like pellets of charcoal. We now have a superconductor! But we have to test it first.

The purity of the now superconductor was to be tested using an X-Ray diffractometer (pictured at right). Before this could be done, the pellets needed to be re-ground using the agate mortar and pestle. Once again, curses to the hunter-gatherers that creating these tools. They are definitely useful, but wholly uninteresting and an unending test of sanity. I found that as a tried to grind with more force, or more quickly, I was more likely to have product fly our of the mortar. This kept me in a perpetual state of wanting to do something faster than was prudent due to our desire to maximize product--rather than have it littered all over the lab tables.



The freshly ground powder was set in a diffraction slide-- a specially designed slide that looks like a thick microscope coverslip that was a rectangular depression in the middle (pictured at left). We were given a quick tutorial on how to use the diffractometer, a device with plenty of detail and chances to mess up the reading. But essentially, the instrument shoots an x-ray at the sample, and results in series of peaks. Those peaks are compared to a reference, and the percent alignment corresponds to the purity of our sample. Fortunately, the sample was relatively pure, with only a few errant peaks. Those should go away with the post-annealing process.

After lunch, we treated the sample with poly-vinyl alcohol. This will reduce electrostatic repulsions at the atomic level, allowing the substance to form a more dense pellet. The end result will be a more uniformly distributed lattice, that should more effectively show the Meissner effect (magnetic levitation).

We made a 3% by mass solution of poly-vinyl alcohol in de-ionized water. Solubility was low, and the solution did not readily form. We added two drops of the solution per gram to the sample that was now in a mortar. To aid the slurry formation, more DI was added to the mortar and the pestle was used to homogenize the mixture. It made a black mud along the surface of the mortar.

The mortar, containing the sample was placed in a 60 degree oven to dry overnight.

All-in-all, this day was mostly preparative in nature. It was nice to see that we had in fact made the compound that we were shooting for, even if the synthesis is relatively error-proof.

"Making pellets IS painful."

6/20 PM

After lunch, we removed the reagant mixture from the oven. At this point it was dry, fine powder, dark gray in color, and ready for pressing. The powder was removed from the petri dish and scraped onto a weighing paper.

Surprisingly, after using a $600 mortar and pestle, balls for jar milling that were also expensive, the method for removing our precious powder from the petri dish was a piece of transparency film. And this was the most valuable lab instrument we used. Valuable- meaning that it was highly effective for its designated task. There is something beautiful there. A one cent fragment of transparency film proved to be wonderfully effective when other more expensive tools left us feeling incompetent.

Once the powder was scraped onto a piece of weighing paper, we pressed them into pellets. Given the shape of the die, these pellets took the shape of hockey pucks. Here's the process:

The die is an expensive set of several metal pieces that is somewhat difficult to describe with words, but I'll paraphrase the process.

The metal casings have a hollow center (pictured above, at left). Some powder (less than 1.0 g) is placed in that center, surrounded by two hockey puck shaped pieces of metal (pictured above, at bottom). Then a metal cylinder is placed on top of the outermost metal hockeypuck (pictured above, at middle).



This assembly is then taken to the pellet press, a device that utilizes a hydraulic pump to apply pressure to the powder (by pushing on the cylinder) and smashing the powder into a pellet. The pressure used is about 3500 pounds per square inch.


Once made, the pellets were placed in an alumina crucible which is stable at high temperatures. They were stacked, and the crucible was placed in a furnace set for 930 degrees. The furnace was set to run for 48 hours, and ramp up by 5 degrees per minute.


The title of this post was a quote from our professor, Ram. He came into the lab late in the day and was watching us toil over our pellets. He wondered whether we were finding the making of pellets painful--meaning tedious, laborious, and painstaking. When we answered in the affirmative, he responded that, "making pellets IS plainful." I found this interesting. It was sort of a right of passage. This process is all a part of doing science. It is at times laborious, even boring. But I think his implied meaning was that everyone has to do these seemingly menial tasks to get the results that may in fact have a huge impact. Our project may not follow that trajectory, but the process we are engaging in is the same that Ram and many others have done as well. Things don't just happen, you have to work for them. And yes, making pellets is, in fact, painful.

Finishing Jar Milling, Maximizing Product



6/20 AM
Well, after the jar mills spent the night in a spin cycle, we went through several steps to recover as much product as possible while losing as little as possible.

First, we poured the slurry (reagants and ethanol) and balls from the bottle in a large, glass petri dish. Much of the slurry had stuck to the sides of the bottle, so we spent considerable time rinsing the inside of the bottle with ethanol, then pouring it out into the petri dish. Unfortunately, not all of the reagent mixture could be removed with an ethanol rinse. It appeared that the solid had leached into the bottle. So after a few attempts and many milliliters of ethanol, the rest of the reagent was given up for lost. The petri dish was then placed in a 120 degree oven to evaporate the ethanol.

Once the ethanol appeared to have completely evaporated (about 20 minutes), there was a considerable amount of reagent stuck to the balls used for milling. One-by-one, we removed the balls with forceps and rinsed them with acetone. The purpose of this was to maximize the amount of product that we could get from the process. Just estimating, there was probably 100 balls to individually pick up with forceps, then rinse and scrape until they were as clean as possible. Unfortunately, this was mostly a feeble effort. Very little of the product came off the balls. It was definitely necessary because leaving product behind is a sin in the lab, but picking up these balls that were less than 1 cm on their longest edge

Once we had given up the balls for a lost cause we put them in a large petri dish, then in the 120 degree oven to evaporate any remaining acetone. Having a sore back from leaning over the counter, and frayed nerves from spending an hour feeling mostly incompetent, we broke for lunch.

Saturday, June 21, 2008

Data Gathering and Reactant Preparations

6/19 PM

Using Balances: The precision on these balances is astonishing and debilitating at the same time. Since the actual yield is not entirely important, measuring exact values was not essential, but it was my first day on the job, and I wanted to do it the right way. However, what I quickly found was that with the balances in the MRL, if a fly passes gas within a 10 foot radius, the value on the balance changes. Soon I quickly abandoned my goal to hit exactly 4 digits of accuracy, and was satisfied with being in the ball park of that number.

Data:
0.8483 g Y2O3
2.9622 g BaCO3
1.7900 g CuO
Mortar and Pestle: For the reaction to proceed well, the three powders needed to be ground into the smallest particles possible. This ensures homogeneity and ease of reaction at the high temperatures. To accomplish this, we used an agate mortar and pestle to grind our reactants. The agate is a hard mineral that will not chip off into the reactants. Surprisingly, these are really expensivse. It seems in the MRL, even the most primitive looking tools are costly, and everyone will despise the intern that breaks them. After about 15 minutes I felt like I could empathize with the ancient hunter-gatherers as they prepared their meals. After 30 minutes, I despised them for inventing such insidious instruments of mental anguish.

Cookie Time: Fortunately, after my powders were as ground and homogeneous as a mortar and pestle can seemingly accomplish (and shortly before my threads of sanity were about to give out), we broke work for "cookie time." Thursdays at 3:30, the MRL At this meeting, all the members of the Seshadri research group get together and discuss lab issues (e.g. which machines are not working correctly, and when orders might be coming in) as well as their own research. This was nice to be a part of. I always tell my students that peer collaboration is one of the most valuable aspects to the scientific process, and this meeting was one example. At this particular meeting, not much was discussed, but I am looking forward to more opportunities to engage in the process of collaboration--something that I had only talked about before.

Jar/Ball Milling: Apparently, I may not have been a stellar hunter-gatherer chef. Our powders were not quite as finely granulated as they could be to maximize reaction efficiency, so we moved to the jar/ball milling technique. We transferred our powder mixture to a 50 mL plastic bottle, added the balls until 2/3 full, then filled with ethanol. The ethanol would act as a solvent and make a slurry with the reactants. The jar was then sealed, tested for leaks, the lid wrapped in paraffin wax, then placed in the jar milling apparatus. That title makes it sound pretty fancy, but it is essentially a big jug turned on its side, and set on rollers that cause it to rotate. As the apparatus rotates, the balls grind the slurry into a much finer consistency than the mortar and pestle could achieve.

We set the mill to run overnight, then left for the day. All-in-all, a nice first day of work. I experienced the tedious nature of many mundane but necessary scientific processes, as well as the enjoyment of being part of an academic community.

Getting Started

6/19 AM

Following a group meeting with the RET project coordinators, we met up with our research mentors and began the project in earnest.
As mentioned in the initial post, my research project is to make the superconductor, YBa2Cu3O7 (aka YBCO or Y-123). The synthesis appears to be pretty straight forward.

The reaction is: (1/2)Y2O3 + 2BaCO3 + 3 CuO --> YBa2CuO7

This reaction as written is not balanced (something for which my students would mercilessly chastise me), but my understanding is that the carbonate is liberated as carbon dioxide gas. Also, the oxide chemistry is not something that I had significant exposure to as a student but I'll make my best attempt at explaining based on what my research mentors and Ram have said. Initially, the YBCO is oxygen deficient and often has the formula written as YBa2Cu3O7-x, meaning that there is some amount of oxygen missing. This will be fixed in the second phase of heating in an oxygen environment (termed post-annealing).

Stoichiometry--one of my favorite words in chemistry. It is so abrupt and strange sounding, but has the elegant meaning of simply measuring elements. I also find the coining of the term fascinating. Jeremias Richter, in his work showed how amounts of products could be predicted if the initial amounts of reactants were known. His loftier goal was to use this elegance in nature to prove the existence of God. If only my goals were so meaningful, but I'm making a hovering train which will be pretty cool-- but as yet not divinely inspired.

The point of this paragraph was to say that as we got started, we needed to determine the stoichiometric amounts necessary to produce 5.0 g of YBCO. Moments like this are probably the inspiration behind the RET program, but it was nice to perform stoichiometric calculations with an actual purpose, rather than just introducing the topic to students and modeling the process. This was real stoichiometry, using the method that I had taught only a few months earlier.

Stoichiometric Calculations: to make 5.0000 g YBCO
0.8468 g Y2O3
2.9601 g BaCO3
1.7898 g CuO
From these calculations, data will be gathered and the reactants will be prepared for the reaction conditions.

Friday, June 20, 2008

Introductions

Hello,

This blog is started with two goals. First, it will serve as an unofficial lab book where I will document my progress with lab methods as my research group and I work toward our research goal (more on that later). Second, I intend to log my thought processes, questions and possibly emotions as we work on the problem.
I am participating in a program funded through the NSF that allows teachers to gain research experience in university labs. This Research Experience for Teachers (RET), exposes teachers to real research/lab work that they may or may not have in their undergraduate preparations. The second component of this program will take place next summer. I will work on a curriculum project that will bring methods, ideas and general "nature of science" processes to the classroom (citation to come). I do not know as many details about RET part II, but that will be the focus of later posts as I get more information. Frankly, the focus of this summer is almost entirely research, and that will encompass the vast majority of the early posts.

About myself--I teach high school science (chemistry and general science). I have a wide range of interests, and when I go to the beach, I enjoy reading Inorganic Chemistry textbooks just as much as the candy-reading standard arc plot thrillers that grace the New York Times' Best seller list. That's enough about me for now. Since this is a diary of sorts, any readers will gain exposure to my thoughts over the course of the summer. Writing a paragraph about myself is as tedious as weighing a solid reagent to a precision of four decimal places. Not my favorite thing to do, but I will as much as I need to.

My research mentors, partners and I work in Ram Seshadri's Materials Research Lab at UCSB. Our specific work will be synthesizing, analyzing and creating an application for superconducting material. The materials science itself is not cutting edge. The compound (YBa2CU3O7) has been around since 1986 and is quite well known because it is one of the few high temperature superconductors. High temperature meaning about 90 K or -183 degrees Celsius. Liquid nitrogen can accomplish this. Liquid nitrogen is also known as "one of the funnest lab materials around." So I'm looking forward to working with that.

The creative component to this project comes after the compound is synthesized. As a professor, Ram participates in many science nights at local schools. One of his favorite "magic tricks" is to take advantage of the magnetic repulsion property of superconductors when the material is at or below its critical temperature. This trick entails floating a magnet over the superconducting material. It literally hovers and is quite astonishing the first time you see it. Our project is to devise a vehicle that will not just float, but will also move down a track. Once the synthesis aspect is completed, this project will transform into an engineering exercise, which will be a challenge. My understanding is that Ram will then have this contraption to use at science nights to captivate the imaginations of area students, thus piquing interest in science-- and I am all for that.

At this point, I think that is a sufficient introduction to the project. More will follow as I catalog my own progress, successes, and failures.