|
|
Below is a week by week report on the weeks happenings...
 | The First Week
 |
The first few days were hectic and filled with
anxiety. Getting acclimated to a new environment and trying to
figure out what project to pick were definitely taxing on the brain,
especially following a month of relaxation, since school ended at
the end of April. For two days we listened to mentors present their
research and projects. Finally though, on Wednesday we were able to
decide, we had three choices, pick #1 being our favorite. Later that
day at an ice cream social at Dr. Larry Weaver’s House, Larry and
Kristan told us who got what project.
Fortunately, I got my top pick, which was a project with Dr. Chris
Sorensen, on Aerosol
gelation, click on the
Research
goals and
Theoretical
Background links to
learn more about it. The next day, a Thursday, I began my journey
into Aerosol gels.
Mrs. Sarah
Elizabeth Gilbertson
a graduate student in physics in search of her masters was already
working on the project. She is the resident expert on aerosol gels,
besides Dr. Sorensen, and she began to teach me on the subject and I
worked with her on her project to learn more. She had been working
on gelling an aerosol with liquid phase precursors, but to date she
had not accomplished such a feat. Thus ended the first week, a
hectic week filled with much reading on aerosol gels. |
|
| The Second Week
| We began this week with a bang...a styrene and oxygen explosion
in the 100mL cylindrical chamber. Unfortunately, we only attained a
thin layer of soot plastered to the walls of the small chamber. We
later performed another explosion with similar results. This led to
the idea that we were not getting enough volume fraction from the
styrene vapor. At this point we went to take a TEM (Transmission
electron Micrograph) of our soot. The TEM showed us little
aggregation, and another interesting feature. There were noticeably
large black monomers, about 300 nm in diameter, amongst the smaller
monomers, about 5-10 nm in diameter. This led to the idea that the
large black monomers were pyrolized Styrene droplets that did not
fully combust, hence the low yield of aggregation. Only a shell of
some thickness was being combusted. Back to the drawing board. |
|
| The Third Week
| During this week we performed a light scattering experiment on
our 100 mL bomb chamber, in order to determine the volume fraction.
We have two quartz glasses on the chamber. We fill the chamber up
with the vapor produced by the nebulizer, then measure the peak
intensity through the chamber from the laser, and do the same having
no vapor in the chamber. By how much the peak intensities attenuated
we can determine the volume fraction. The volume fraction was
measured to be ~10-4, so we're at the right order of
volume fraction. thus, the styrene must not be combusting fully.
This week also featured the arrival of the 30 year old 20 liter
apparatus a.k.a. "the detention droid". Its age shows. It will take
a lot of work to get this new bomb chamber operational, I need to
set up the system in which the dust disperses, the ignition system,
find a way to seal the chamber up, in order to adjust the pressure
inside of it, and some other problems. |
|
| The Fourth Week
| This week featured a large "boom". Since we were not getting
full combustion of styrene we decided to add a background gas. This
background gas happened to be acetylene. The oxygen and acetylene
combustion is our bread and butter for creating carbon aerosol gel.
The thought process here is...since the styrene isn't combusting
fully, then if we add some more energy (acetylene) to the system,
perhaps the combustion of the acetylene will add enough humph to the
system so that the styrene combusts fully. When we performed the
first combustion, there was a deafening boom from our chamber as it
broke the 1/4" quartz glass on the sides of the bomb chamber.
Fortunately, we combusted the chamber in a strong fume hood and we
were out of the room at the time of the ignition. Whew. Following
that exhilarating event, we needed to redesign the chambers sides to
ensure such an explosion does not occur again. Two this aluminum
discs should do the trick and they did. |
|
| The Fifth Week
| With our chamber redesigned, we were able to create a gel using
acetylene, styrene, and oxygen. The week was cut short due to being
kicked out, because of asbestos roaming from the ceilings and into
the air, a remnant of the tornado damage. Fortunately, the air
quality tests were negative. We were actually way below the maximum
daily exposure limit, a few orders of magnitude. But nonetheless, we
were pleased to know that we were able to make gel from a mixture of
styrene, oxygen, and acetylene. It was estimated that the gel yield
was increased by about 10%. This was noticed qualitatively too, as
the bomb chamber was noticeably fuller. |
|
| The Sixth Week
| Frustrations over setting up the solid fuel experiment reached
an all time high. I had ordered a part from a company the previous
week and when it arrived, I realized that they sent me the wrong
part. Besides that, the process of making the solid phase experiment
had been coming along relatively smoothly. On the liquid phase side,
we decided to move onto using titanium tetrachloride with oxygen and
acetylene. These precursors would yield some titanium dioxide carbon
aerosol gel combination. The technical advantages of titanium
dioxide gels is enormous. They would be photo catalytic and because
of which, can clean up nitrogen oxides and dangerous organic
compounds. Also, it would perform hydrolysis, so perhaps as a
potential hydrogen fuel cell. |
|
| The Seventh Week
| Success!!!...by the end of this week my hard work paid off and the
solid phase experiment was finally ready to be performed, after much . I started
the tests with just flour in order to work out the kinks in the
system i.e. leaks, pressures, ignition system. Prior to this
grandiose moment, Elizabeth and I had also created a very low yield
of some titanium dioxide and carbon gel. The gel was grayish as
compared to the carbon black and it also had a firmer quality to it.
So we went to get a TEM (transmission electron micrograph) of the
product. |
|
| The Eighth Week
| The results from our TEM of the titanium dioxide carbon gel came
in. We were getting beautiful fractal aggregates, but interspersed
throughout the aggregates were large black balls. We came to realize
that the black balls were burnt titanium drop cores that never fully
combusted, just like the styrene droplets. This was unfortunate,
because it meant with our current experimental set-up was
insufficient. One major problem was that we could not get the
droplet size of our fuel vapor any smaller than ~3 micron in
diameter. This was due to the fact that we created our vapor from a
nebulizer (it breaks up the surface tension of the liquid by shaking
at a certain frequency, thus creating a vapor) that operated at a
frequency of 2.5 megahertz. That was the smallest droplet size we
could attain. Furthermore, we had to stick to liquid fuels that had
a viscosity at or below the viscosity of water. Resulting in a
limited amount of liquids that could be used, mostly hydrocarbons or
some very dangerous liquids, and that wouldn't result in any new
novel aerosol gels, just carbon. So, the move to solid phase
precursors was apparent to see if some new aerosol gel could be
possible, or perhaps there would be a similar problem with solid
phase, where there was not full combustion. Speaking of the solid
phase experiment, it was going smoothly. I managed to get everything
working and I had done an aluminum combustion. I had to move to
electric matches as an ignition source, because the spark gap was
not powerful enough to ignite the aluminum powder. Unfortunately, I
hardly got any alumina, this fact led me to believe that perhaps the
powder was just not very reactive and that something was wrong with
the dispersion system, since I only got caked on aluminum and not
any aerosol soot. |
|
| The Ninth Week
| I determined that the nozzles the dust was coming out of in the
bomb chamber were depositing most of the dust directly onto the
surface of the sphere and not in an aerosol form, so the combustion
was happening when most of the dust was lying in a pile. So I went
to the machine shop and fixed this by plugging up the holes facing
the sphere. Then the most painful thing happened (not physically).
An air leak coming from the
solenoid valves that controlled the dispersion system. With the high
pressures I was using, I was always kind of scared something bad
would happen, since I rarely work with high pressure ~300 PSI. Long
story short, as I went to tighten the bolt where the leak was coming
from, the darn thing broke. This piece was special to this device so
I went on a quest for it. Unfortunately, I had to let a machinist
make it, and due to his schedule, it would not be done until after I
was gone. : ( Also, to add to the misfortune, I determined that the
aluminum powder being used was just not very flammable. By throwing
some in a Bunsen burner, there should be some large white flash, but
there was not much of any different in the flame. We took some
apparently finer powder the physics demonstration lab had and threw
that in the burner, resulting in a magnificent white flash. Hmmm.
|
|
| The Tenth Week
| This week consisted only of three days and I was determined to
work around my problem by jimmy rigging something, in order to get
some solid phase results. First, I was going to borrow some of the
aluminum powder from the demo lab, and secondly find another way to
disperse the dust. Amazingly, I was able to create a way of doing
this by running some copper tubing into the chamber and hooking a
metal funnel to the end of it. The dust would be loaded into the
funnel, then a blast of oxygen would disperse the dust in the
chamber. Unfortunately, I still needed a way to independently fill
the sphere with oxygen, in order to make the atmosphere in the
sphere 100% oxygen. Even though I wasn't able to finish this, I was
able to set up the experiment and show how to use it and show what
work still needs to be done to execute the solid phase experiment to
Eli, who would take over the experiment after I left. My final
presentation is tomorrow, then I go back home, I had a great time. |
|
|
| |
|
