The Hydrophobic Characteristics of Aerosol Gel

        by Chelsi Kovala

        supervisor:  Dr. Sorensen

Kansas State University Physics Department  REU Program, sponsored by NSF

Hello All!

Welcome to my temporary web page. I am (hopefully!) working on upgrading this page in the near future, but this will suffice for the time being. 

Following I will describe my Project Goals, my Research Strategy, my Research Progress, and I will eventually post my Final Presentation and my Final Report.  I may post my homework assignments from our weekly REU scientific Ethics class, taught by Prof. Bruce Glymour, and my reaction to Prof. Larry Weaver's Lectures.   Scroll all the way down to learn more About Me.  Finally, I've included some Useful Links.

Background: Before I dive into my research let me give you some background. First, take some time on this site to get a feel for the idea of fractals. http://www.math.umass.edu/~mconnors/fractal/sierp/sierp.html Fractals are defined on dictionary.com as

"A geometric pattern that is repeated at ever smaller scales to produce irregular shapes and surfaces that cannot be represented by classical geometry....".
Another way to think of fractals is to consider the concept of dimensionality. We live in a 4-demensional world (assuming you believe Einstein!) and we generally deal with dimensions with nice integer relationships. To practice thinking about these types of concepts consider this question - if you make a person twice as tall as they normally are (and keep them proportionate!) how much will their mass increase? Now consider how much their skin area will increase? The answers are 8 and 4 respectively... This is because height is a 1-demensional measurement, skin is 2-dimensional and mass is 3-dimensional. However, when you are dealing with fractals you don't get nice integers when you double something - for example when you double the volume of the gel I am researching (a fractal aggregate - more on that later!) the mass does not double - it expands by a factor of 1.8 or 2.6 - not an integer value.
   Now lets move on to aerogels. You can explore silica aerogels at  http://eetd.lbl.gov/ECS/aerogels/saprep.htm Our gel is carbon based and our manufacturing process is different as well - but you can get a feel for the idea here. The main point is how light and fragile the gel is - only a little bit more dense than air. This stuff is pitch black and crumbles to a fine soot when touched.
This gel is a "fractal aggregate" because when we make it the gel aggregates in the container in a fractal pattern.

Project Goals: The primary goal at this time is to gain understanding of the hydrophobic nature of our carbon based aerogel. There is a picture of a water droplet sitting on the surface of the gel after is is pressed flat. This picture shows the hydrophobicity of the gel - the droplet just sits on top of the gel without wetting... I think. More on that later.  

   

 

Research Strategy:  My research is exploratory by nature and therefore my approach must be open-minded. In general I am looking for functionality between the physical traits of the gel - basically I want a graph that accurately predicts graphs. I want to understand why these traits exist and then look for applications for my discoveries.  

Research Progress: 

Up 'tll June 6th, 2006......

So far my progress is thus:

1) I noticed soon after research started that there was a relationship between the time the droplet sat on the gel and the contact angle of the droplet. (KSVLTD - Contact Angle -- Check this site to see what the contact angle is for for liquid on a surface.) After taking measurements and gathering some data, I decided that this is due to the water droplet evaporating. As the droplet sat on the surface it shrank considerably, but the contact length of the droplet stayed the same... Look at the two pictures below, if you look carefully at the length of the droplet that actually contacts the surface, you will notice it is the same in each picture! (Though determining this required a closer look than you are getting by inspection here!) So, after doing some calculations that indicated up to 40% of the droplet could be evaporating and some further experimentation, I concluded that the droplet was shrinking due to evaporation and that was what was changing the contact angle. Further experiments are pending to observe the droplet in an environment where it can't evaporate - very much at least. :) 

  

 

2) Another observation I had is that the surface becomes sticky after the droplet sits for some time so that eventually you can totally invert the surface and the droplet will hang from it! I have not conducted any experiments yet because I am still mentally designing an apparatus that will allow me to measure the angle at which I have to tilt the surface for the droplet to roll off the surface.

3) I have also been looking at the relationships between surface tension and contact angle. So far I have just performed preliminary experiments, but I do know that the droplet wets almost completely when it is 3% ethanol/water mixture. So I am going to add 1/5 ml of ethanol at a time to 100ml of deionized water and take digital photographs of the the droplet to observe the changes in the contact angle.

-----------June 6th to July 7th-----------

I can't believe a month has passed! Well, here is what's up.

1) There has been a lot of miscellaneous stuff going on - mostly the holiday (just passed) and taking the machine shop class (VERY fun). I had a long fight with my computer over PDF files and I have been working on a literature review... (more on that later).

2) Surface tension experimentation commenced and I got some decent data out of the experience. Mostly the data indicated a dramatic decrease in contact angle when I reached about .5ml ethanol in 100ml water. However I started noticing inconsistent results depending on where on the surface I placed the droplet. Finally, after severe changes in the contact angle were observed depending on the location of the droplet, Dr. Sorensen suggested that I work on some ways to reduce the number of variables that could be tainting my results.  More later.........

Final Presentation:  Click here to download my presentation in PowerPoint and PDF formats. (still working on it)

Final Report: Not done yet... I just started.

Lectures by Dr. Weaver: 

These lectures have ranged widely in topic, from classical to quantum, covering lasers, particle physics, relativity, fusion and more. I enjoy these despite my fiendish brain's inane desire to return to a sleep riddled state - a "ground state" you might say....  :) Despite the occasionally vicious fights with my nefarious subconscious to remain alert, I have enjoyed the brief introductions to various areas of physics that I intend to pursue in the future...  I haven't had any trouble understanding anything that has been discussed at an intuitive or basic level. However, I am constantly assailed by the impression during lecture that we are skimming gleefully over the ocean's surface pretending that we have plumbed its depths....   

About Me:  I was born in Arizona and moved to Kansas City when I was 10. I attended two junior colleges after high school to take some general interest classes, eventually pursuing the prerequisites I needed to pursue an engineering degree. Here at K-state I have fallen in love more and more with Electrical Engineering every semester. However along the way my long standing passion for science and knowledge grew into the pursuit of an additional degree in physics. Alas my journey is now allowing me to transverse a small part of the world of research in physics. I have three years to go before I graduate with my two degrees and I am only more and more impassioned about my field. This coming semester I am taking Electronics I, Circuit Theory II, Intro to Optics, Thermodynamics & Statistical Physics and Into to Critical Thinking.

Useful Links: 

American Physical Society Statements on Ethics

American Institute of Physics

My Research group's home page