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Functionalization and Dispersion of Carbon Nanomaterials Using an Environmentally Friendly Ultrasonicated Ozonolysis Process
Chapters
Summary May 30th, 2017
Here, a novel method for the functionalization and stable dispersion of carbon nanomaterials in aqueous environments is described. Ozone is injected directly into an aqueous dispersion of carbon nanomaterial that is continuously recirculated through a high-powered ultrasonic cell.
Transcript
The overall goal of this Ultrasonic Ozonolysis and Electrophoretic Deposition processes is to achieve a stable dispersion of carbon nanomaterials which can then be used for the preparation of hierarchichal composite materials. This method can answer key questions in the hierarchichal composites field. By providing a convenient method to controllably coat microfiber fabrics with carbon nanomaterials.
The main advantage of this technique is that carbon nanomaterials such as nanotubes and nanoplatelets can be functionalized made compatible with polymeric resin systems without the use of harsh chemicals. To begin this procedure, transfer all needed materials into a glove box inside a hepa-filter equipped fume cupboard. Weigh the desired quantity of nanomaterials into a bottle and add water so that the final nanoparticle concentration is one gram per liter.
Seal the bottle with a lid. Ultrasonicate for 30 minutes at 43 kilohertz and 60 watts to disperse the CNTs and GNPs. Next, carefully pour the nanoparticles suspension into a reactor flask containing a magnetic stir-bar.
Assemble the experimental set-up as detailed in the text protocol. After this, insert the ozone bubbler and connect it to the ozone generator. Then, place the reactor flask into the refrigerated bath.
Stir the solution to prevent the CNTs from settling out of the suspension. Turn on the cooling water recirculation unit to cool the ozone reactor and ultrasonic cell. Then, turn on the oxygen supply to the ozone generator.
Adjust the flow rate to zero point five litters per minute. Turn on the ozone generator and allow it to run for 30 to 60 minutes. The use of a bubbler on the other side of the ozone destruct unit enables a quick check that the ozone generator is connected and flowing properly.
After this, turn on the peristaltic pump and adjust it to zero point six seven hertz. Turn on the ultrasonic horn and adjust the power to 60 watts. Observe the sonication process for at least 30 minutes, to ensure the pumping and ultrasonic horn operation is stable.
After the desired ultrasonicated ozonolysis processing time has elapsed, turn off the ozone generator, sonicator, and pump. Stir the carbon nanomaterial dispersion for one hour to allow the ozone and solution to decompose. To begin, sonicate the nanomaterial suspension if electrophoresis is not performed within 24 hours of the ultrasonicated ozonolysis processing.
Then, prepare three stainless steel electrodes as outlined in the text protocol. Using P1000 aluminum oxide sandpaper abrade the electrodes. Clean the abraded electrodes in an ultrasonic cleaning bath for 10 minutes in ultra pure water.
Place the electrodes in a clean oven to dry for 10 minutes at 100 degrees celsius. After this, move the eletrodes to a desicator to cool. When cooled, weigh the electrodes to be used for anotic deposition on a four figure analytical balance.
Then assemble the electrodes as outlined in the text protocol. Transfer 35 milliliters of carbon nanomaterial dispersion to a 50 milliliter beaker. Secure the electrode fixture to a retort-stand.
After this, slowly lower the electrodes to the bottom of the beaker. Attach the positive terminal of the DC power supply to the central anode. Next, attach the negative terminal to one of the outer cathodes.
Using a lid with alligator clips, connect the two outer cathodes. With the power supply turned off, adjust the current to the maximum setting. Adjust the voltage to the required value for the desired study.
Then, prepare a stopwatch and turn on the power supply for the required coding duration. After this, switch off the power supply. Slowly raise the electrode fixture out of the dispersion, ensuring that the film is not disturbed.
Disconnect the terminals from the electrodes. Next, slowly rotate the electrode fixture to a horizontal orientation. Allow the film on the anode to dry evenly.
After this, disassemble the fixture and dry the anode in an oven for one hour at 100 degrees celsius. Place the dried anode in the desicator to cool. Using an analytical scale, record the weight to four decimal places.
Photograph the coded anode and repeat the coding and weighing process for each deposition time. Then, perform characterization and analysis as outlined in the text protocol. In this study, a novel method is used to functionalize and stably disperse carbon nanomaterials in an aqueous environment.
X-ray photoelectron spectroscopy widescan characterization shows that CNTs that did not undergo USO treatment contain almost no oxygen. However, the surface oxygen level is seen to increase as the USO treatment time increases. A raman spectrum reveals the presence of defects in the CNTs which existed even before USO treatment.
The G band is seen to shift from a wavenumber of 1, 576 to a wavenumber of 1, 582 with the second component becoming more pronounced at a wavenumber of 1, 618 as USO time increases. Noticeable differences are also seen in the intensity of the two D band at a wavenumber of 2, 698. And then the D and G band at a wavenumber of 2, 941 as USO time increases.
These changes all correspond with an increase in the oxidation level of the CNTs. Scanning electron microscopy shows that while untreated CNTs are highly compt, CNTs treated with USO are much more evenly distributed across the surface. This indicates that USO treatments has helped to reduce agglomirates present in the as received material.
The USO treated CNTs are then electrophorically deposited using a variety of conditions, thicker films are produced as electrophoresis time increases. Thicker films are also produced when higher CNT concentrations are used. After its development, this technique paved the way for researchers in the field of hierarchical composites to explore whether Ultrasonic Ozonolysis can be used to functionalize other nanomaterials for eletrophoretic deposition.
Different coating levels of carbon nanomaterials can have a significant effect on the macroscale composite properties such as strength and toughness. Because the method is water based after funtionalization, the ozone breaks down into harmless oxygen. And there is no need to remove chemicals from the dispersion before using the nanomaterials.
Don't forget to run the ozone for one hour before turning on the peristaltic pump. Otherwise, you'll get clumping of nanomaterials in the tube.
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