Summer Scholar Ashley Kaiser delves into hybrid carbon nanotube materials research in nectslab.
|Ashley Kaiser holds samples of carbon nanotubes she grew in the Wardle lab as part of her summer project studying carbon nanotube-based aligned nanofiber carbon matrix nanocomposites [CNT A-CMNCs]. The carbon nanotubes are on the left, and the pyrolytic carbon is on the right. These new materials have potential aerospace applications. Photo, Maria E. Aglietti.|
University of Massachusetts Amherst chemical engineering major Ashley Kaiser joined MIT Professor of Aeronautics and Astronautics Brian L. Wardle's necstlab this summer with past experience in growing graphene and examining it with Raman spectroscopy.
During her new summer internship, Kaiser, who is a rising senior, is learning new fabrication and characterization techniques to further necstlab’s research on carbon nanotube aligned nanofiber carbon matrix nanocomposites [CNT A-CMNCs].
High temperature composites
MPC-CMSE Summer Scholar Kaiser is making these composites, which are treated at high temperatures from 600 to 1400 Celsius [1112 F to 2552 F], and analyzing their composition to study the confinement effects of the carbon nanotubes in the carbon matrix. Similar heat-treated material, called pyrolytic carbon [PyC], is currently used for aerospace applications but in a simpler form without embedded carbon nanotubes. “It’s super hard and lightweight, and since carbon nanotubes are also very strong and lightweight as well, we would like to introduce these nanotubes inside this existing matrix,” Kaiser explains.
“Ashley’s primary contribution is to help us understand how the aligned carbon nanotubes facilitate the self-organization and meso-scale evolution of the graphitic crystallites that comprise the pyrolytic carbons, and how control over the processing (i.e., pyrolysis) temperature can modify the structure and morphology of A-CNT-PyC hybrid nanocomposite materials on the nanoscale,” necstlab Postdoctoral Associate Itai Stein says.
“The results from Ashley’s project will be invaluable to better understanding the process-structure-property relations of these high temperature materials,” Stein adds. Kaiser’s project builds on work done in necstlab by 2015 MPC-CMSE Summer Intern Alexander Constable, who studied the structural evolution of pyrolytic carbon (PyC) as a function of processing parameters and the effects of aligned carbon nanotube (A-CNT) confinement.
Four key steps
Her project consists of four steps, Kaiser explains:
• Carbon nanotube growth
• Polymer resin infusion
• Oven curing the polymer matrix nanocomposites
• High temperature heat treatment (pyrolysis)
“Basically, we want to fabricate and characterize the composites to see what effect the carbon nanotubes are having on the final structure to address several questions – what it looks like, if the nanotubes stay aligned, are there functional groups inside of that, are there defects, what’s the crystallite size, etc.” Kaiser says.
“We are seeing that when we are putting our nanotubes into our composite, the effect of them governs the meso-scale [submicron scale], which means that the way the atoms are arranging in our crystallites isn’t changing too much just from having our nanotubes there, which is interesting. So in terms of scaling this up to, say, something in industry, the fact that it’s not changing the entire atomic scale is beneficial because it means that processing may not be too different,” she says.
“This composite is a closely-related material with similar strength to PyC because the atoms are arranged similarly, but it’s more lightweight, at least we think, which is a step up in improving the current technology,” she adds.
Adding new skills
Although she previously grew graphene using chemical vapor deposition, growing the carbon nanotubes using a similar chemical vapor deposition process at MIT and making the final nanocomposites requires more steps. “After the CNT growth, I do polymer infusion under vacuum, then the samples are cured in an oven, and then they are pyrolyzed in an even larger furnace. In this way, I’m working on many different pieces of equipment in the lab, which is great experimental experience,” Kaiser says.
|Ashley Kaiser prepares to grow carbon nanotubes [CNTs] on a silicon wafer with a coating of alumina and iron in a 1-inch furnace. Alumina and iron act as catalysts to stimulate the CNTs to grow. During her summer project in the Wardle lab, Kaiser grew pyrolytic carbon as a control in addition to growing carbon nanotubes, turning out 5 samples of each at a time. Photo, Maria E. Aglietti.|
Although she has previous experience with Raman spectroscopy at UMass and from her 2015 summer internship at 3M, she is learning new characterization skills at MIT this summer, including SEM [scanning electron microscopy], FTIR [Fourier Transform Infrared Spectroscopy], XRD [X-ray Diffraction] and SAXS [Small Angle X-ray Scattering]. “I think that’s going to be really beneficial experience moving forward into graduate work,” she suggests.
“The overarching goal is to study the impact of carbon nanotube confinement on the graphitic crystallites that comprise the pyrolytic carbon, or the matrix of our nanocomposites,” Kaiser explains. “We are finding that as our temperature is increasing, our material is evolving, and it’s forming essentially a lower density pyrolytic carbon which may be more diamond-like, and very strong. We are interested in examining how the nanotubes are affecting the carbon matrix crystallite growth in the composite at various processing temperatures. If this material can be processed to maintain high strength while becoming even lighter, it could be an ideal candidate for aerospace applications.
“I’m essentially doing all the processing, characterization and analysis on my own, so I’m really very solo on this project. I have about 50 robust samples to fabricate and analyze over the course of my summer internship here at MIT,” Kaiser explains. “I’m definitely quite busy with that, but I’m very excited about it at the same time.”
MPC and CMSE sponsor the nine-week National Science Foundation Research Experience for Undergraduates (NSF REU) internships with support from NSF’s Materials Research Science and Engineering Centers program (grant number DMR-14-19807). The program runs from June 7 through Aug. 6, 2016.
– Denis Paiste, Materials Processing Center | July 27, 2016