This study employs the Modified Embedded Atom Method with Bond Order (MEAM-BO) atomic potential as first used to capture single-wall carbon nanotube (SWCNT) properties accurately. We updated the MEAM-BO potential parameters to produce a MEAM-BO* potential for the SWCNT system. Calculating the wavenumber of the radial breathing mode (RBM), elastic properties, and folding energy (DELTA E) of SWCNT which are all associated with bond curvature was considered. Interestingly, MEAM-BO* including the SWCNT data base, improved the previous fit of the C-H system. Further discussed is how we constructed five different partially unzipped carbon nanotubes (PUCNT) and investigate the mechanical properties and self-healing of the simplest PUCNT by using molecular dynamics simulations. In addition, we studied the exploration of damage evolution and the mechanical response of a polyethylene/single wall carbon nanotube composite (SWCNT-PE) at different stress states, temperatures, and strain rates which are studied through utilizing atomistic simulations. The SWCNT-PE composite was expanded perpendicular to the nanotube direction and damage was computed in terms of the void number density (void nucleation) and void volume

The purpose of this research is to explore the potential of using carbon-infiltrated carbon nanotubes (CI-CNT) as a material for coronary artery stents. Stents are commonly fabricated from metal, which may not perform as well as many polymers and ceramics in biomedical applications. Pyrolytic carbon, a ceramic, is currently used in medical implant devices due to its preferrable biocompatibility properties. Micro-patterned pyrolytic carbon devices can be created by growing carbon nanotubes, and then filling the space between with amorphous carbon via chemical vapor deposition. We prepared multiple samples of two different planar stent-like flexible geometries and smaller cubic structures out of carbon infiltrated carbon nanotubes. These samples were tested in tension to failure. The cubic structures were used for separate compression tests. We also examined existing auxetic patterns for possible application in the stent designs and a second iteration of design and fabrication was performed using data and understanding obtained from the work in the first iteration. Slight changes were made to the mask design and fabrication processes based on the new geometries and testing considerations. The auxetic planar designs were tested in compression to demonstrate flexibility and collect material data. The testing results show that CI-CNTs can be designed and fabricated into flexible geometries capable of stent-like compression. The samples in this work were found to have moduli ranging from 5 to 27 GPa, with the majority being between 10 and 20 GPa. We also found fracture strength greater than 100 MPa, with it sometimes getting as high as 200 MPa. Lastly, fracture strain values were measured, with the maximum reaching 1.4% and the average between 0.75-1%. We also found that the CI-CNTs material lends itself to fracture at weak locations (if present) before the anticipated fracture strength has been reached and concluded that a tightly controlled process (including fabrication machines) environment is necessary to ensure consistent results and a CI-CNT material whose imperfections have been minimized.

Thermal protection systems, which are commonly used to protect spacecraft during atmospheric entry, have traditionally been made of materials which are traditionally high in manufacturing costs for both the materials needed and the manufacturing complexity, such as carbon-carbon composites and aerogels. [1] In addition to their manufacturing costs, these materials are also limited in their strength, such as PICA, in a way that necessitate the use of tiles as opposed to single structures because they are not capable of supporting larger structures. [2] The limitations of polymer reinforced composites have limited their entry into these applications, except for pyrolyzed composite materials, such as carbon-carbon and ceramic composites. These materials have been successfully demonstrated their utility in extreme environments, such as spacecraft heat shields, but their high costs and the difficulty to manufacture them have limited their use to similarly high performance applications where the costs are justifiable. Previous work by others with “fuzzy fiber” composites have shown that aligned carbon nanotubes (CNTs) grown on fibers can improve their thermal conductivity and wettability. To this end vertically aligned CNTs were studied for their potential use, but found to be difficult to process with current conventional techniques. A composite material comprised of basalt, a relatively new reinforcing fiber, and phenolic, which has been used in high-temperature applications with great success was made to attempt to create a new material for these applications. To further improve upon the favorable properties of the resulting composite, the composite was pyrolyzed to produce a basalt-carbon composite with a higher thermal stability than its pristine state. While testing the effects of pyrolysis on the thermal stability, a novel iv technique was also developed to promote in-situ carbon nanotube growth of the resulting basaltcarbon composite without using a monolithic piece of cured phenolic resin in place of the standard aromatic hydrocarbon-catalyst precursor. [3, 4] The in-situ growth of carbon nanotubes (CNTs) was explored as their thermal stability [5] and effectiveness in improving performance has been previously demonstrated when used as a resin additive [6]. The specimens were examined with SEM, EDS, and TGA to determine the effects of both pyrolysis and CNT growth during pyrolysis of the basalt phenolic composites. These tests would confirm the presence of CNTs/CNFs directly grown in the composite by pyrolysis, and confirm their composition by EDS and Raman spectroscopy. EDS would additionally confirm that the surface of the basalt fibers possess a composition suitable for CNT growth, similar to the parameters of CVD processing. Additional testing would also show that the growth behavior of the CNTs/CNFs is dependent on temperature as opposed to composition, indicating that there is a threshold temperature necessary to facilitate the availability of catalysts from within the basalt fibers. The thermal stability shown by TGA indicates that the process of pyrolysis leaves the newly formed composite with a high degree of thermal stability, making the new materials potentially usable in applications such as turbines, in addition to large-scale thermal protection systems.

Water scarcity is a growing concern at the global scale. Large scale water reuse is growing both in necessity and popularity. Before water reuse can be performed efficiently on a large scale or be used for potable supply, even indirectly, contaminants of emerging concern (CECs) will need to be treated at the full scale. Advanced oxidation processes (AOPs) are a form of advanced water treatment capable of treating a wide range of CECs. This study contributes to the growing field of AOPs and more specifically AOPs using ozone combined with functionalized multi-walled carbon nanotubes (MWCNTs). Ozonation of MWCNTs has been found to increase hydroxyl radical production and improve AOP treatment. Novel MWCNT-enabled membranes were used as catalysts for ozonation to degrade the CEC Atrazine. Atrazine is an ozone recalcitrant CEC that is commonly found in herbicides. Atrazine removal results, found using a high-performance liquid chromatograph (HPLC), were inconsistent between membranes constructed using identical procedures. Further analysis using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopes (SEM), and UV-Vis spectrophotometry was conducted to explore inconsistencies in construction of the membranes which might explain removal inconsistencies and predict membrane longevity. Removal was found to be influenced by filtration time and ozone exposure. Ozone exposure and filtration time influence percent removal because they both affect hydroxyl formation. The membrane test filtration duration, for equal filtered volumes, ranged from under 5 minutes to nearly an hour. It is believed that filtration time inconsistency was due to inconsistent MWCNT loading on the surface of the membranes. Extended exposure to ozone might change the surface chemistry of the MWCNTs on the membrane surface, affecting hydroxyl radical production. Additionally, repeated use of the membrane created surface defects that might reduce the membrane strength. This study found that the lifetime of the membrane is far past what was simulated in lab and further testing must be performed.

The purpose of this lab was to investigate the printability of cellulose nanofiber/carbon nanotubes, their functions as actuators, and to compare these properties with MXene/nano cellulose gels. Data on MXene/nano cellulose gel was obtained from previous research made by Hamedi labs. Data on carbon nanotubes were collected through experiments evaluating different concentrations and sonication times to yield a gel with high conductivity and viscosity. While it was concluded that both gels could be printed into 2D or 3D shapes, the latter failed to maintain its structure over time due to issues with drying. However, it was found that only 2D MXene/CNF could be used as a reversible actuator. / Syftet med laborationen var att undersöka 3D skrivningsförmågan för nanocellulosa/ kolnanorör samt samt deras förmåga att fungera att svälla elektroniskt. Vidare jämfördes dessa egenskaper med MXene/nanocellulosageler. Data på MXene/nanocellulosa insamlades från tidigare experiment gjorda av Hamedi labs. Data på kolnanorör insamlades genom en rad experiment, vilka utvärderade olika koncentrationer och sonikeringstider för att producera geler med hög konduktivitet och viskositet. Slutsatsen blev att båda gelerna kunde 3D printas, men endast MXene/nanocellulosageler kunde användas för elektronisk svällning och avsvällning. Inga geler kunde göras till 3D strukturer.

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