During this fifth week of research, we’ve been able to move on past the purification of carbon nanotubes (CNTs). We were able to take the CNTs we put in solution with chlorosulfonic acid and make films.
To make films, you have to coat one side of a glass slide with the CNT solution. Then you place another slide on top of the first slide and move them around until the solution is dispersed.
Next you have to use a device built by a grad student in the lab to quickly shear the slides past each other. Both slides then drop into a jar of ether. The slides are removed and hopefully, you have a smooth film on each slide.
After the films dry on the slides, you gently use a spatula to push the film to the center of the slide until you have a fiber.
Once you have a fiber on the slide, you gently remove it and then twist it.
We were then able to measure the diameter of the fibers with a microscope and test the conductivity.
Unfortunately, our fibers aren’t the greatest quality. Moving forward, my mentor will be reviewing the purification process to find out if it’s damaging the CNTs. She’ll also be looking at the recipe and reactor conditions for synthesizing CNTs. And, I won’t be here to help! 🙁
This week I’ve gotten to see and do a lot of new things. Since we finally had some purified carbon nanotubes (CNTs), we put them in chlorsulfonic acid to dissolve the CNTs. The result is a viscous black liquid that we can then analyze.
We then used some of the dissolved nanotubes to make a sample in capillary tubes to be analyzed with Polarized Optical Microscopy (POM), To make the sample, you have to draw up some of the liquid into a tiny glass tube. Then you have to use a blowtorch to melt both ends of the tube. The POM was being finicky, so we didn’t actually get to observe the samples.
We then used an extensional rheometry technique that was developed in the Pasquali lab to determine the aspect ratio of our CNTs. There are two pistons in a glove box that are really close to each other. You take a drop of the dissolved CNTs and place it between the pistons. You record video of the CNTs pulling apart. Here’s what the Pasquali group paper says about the extensional rheometry: “The method is based on measuring the extensional viscosity of CNT solutions in chlorosulfonic acid with a customized capillary thinning rheometer and determining CNT aspect ratio from the theoretical relation between extensional viscosity and aspect ratio in semidilute solutions of rigid rods.” I’m still trying to figure out what that means…
Purification of carbon nanotubes (CNTs) is a looooong process and you lose a lot of material. The CNTs that we synthesized on June 13th are finally through the purification process. When we first retrieved the CNTs from the reactor, we collected 76.2 mg and called them sample DOE-01-180613.
After the first round of a hydrochloric acid wash, water wash, and freeze drying, the sample weighed 65.5 mg. And, each of these processes takes an entire day.
Then we put the sample in the furnace for air oxidation. The furnace heats up to 450 degrees Celsius, and the sample stays in for 12 hours. Another day… After air oxidation, the sample weighed 40.4 mg.
We then went through another round of acid wash, water wash, and freeze drying. Today, we can call these CNTs purified! And, they now weigh a grand total of 22.8 mg. From 76.2 to 22.8 mg means that there was a lot of iron and amorphous carbon in our CNTs.
All in all, it took us 8 days to purify sample DOE-01-180613. The next step will help us figure out the aspect ratio of these CNTs; we’ll use extensional rheology and a look through the transmission electron microscope to find out if we have have quality CNTs. Two new tools to learn!
This was a week of hands-on, independent work. My mentor showed me how to do everything last week and left me to my own devices. The week started off really well. I started by using a scanning electron microscope (with lots of help); the images you can capture are amazing, though not magnified enough to see individual carbon nanotubes (CNTs).
I then worked on purifying a sample of CNTs — first through an acid wash and then a water wash. Later in the week, I learned how to purify the sample even more by burning off amorphous carbon in a furnace.
I also spent a lot of time analyzing Raman data and looking at TGA data. I’m finally beginning to understand what all the graphs and charts mean!
I did accidentally break a slide when trying to find the CNTs on the Raman microscope. I felt really silly and anxious about it. The folks in the lab made me feel better though. And, I got to experience a little anxiety about learning something new — which put me in the place of my students. So, a good experience all around.
First, an introduction. I’m Sarah Gonzales, a fourth grade teacher at Travis Elementary in the Houston Heights. I teach all subjects, but have a real love of science. I’m excited to be part of RET so that I can better teach the overall scientific process and talk to my students about the real scientific research I am doing over the summer.
It’s been an extremely busy, productive, fun week. I’ve been learning how to operate several instruments and learning the process for synthesizing, purifying and characterizing carbon nanotubes (CNTs).
Purifying CNTs is all about ridding the sample of amorphous carbon and iron. I’ve gone through the first several steps of the purification process, including washing the CNTs with hydrochloric acid. More on this next week, when I’ll be doing this by myself!
Before and after purifying the CNT sample, you need to characterize it. The first technique uses Raman spectroscopy. Raman spectroscopy involves shining a laser on a sample and detecting the scattered light. With Raman, you learn how defective the CNTs are and if the CNTs are metal or semiconductors.
Today, I learned how to conduct thermogravimetric analysis (TGA). With this instrument, you’re basically burning part of the sample to find out what is left, such as iron.
Next week, we’ll be using scanning electron microscopy to find out about the morphology of the CNTs on a micron scale.
I can’t wait!
K-12 Educators Disseminating Research from Rice University, Arizona State University, and University of Texas-El Paso