| NSF Org: |
CMMI Div Of Civil, Mechanical, & Manufact Inn |
| Recipient: |
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| Initial Amendment Date: | June 1, 2015 |
| Latest Amendment Date: | May 30, 2019 |
| Award Number: | 1463636 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Andrew Wells
awells@nsf.gov (703)292-7225 CMMI Div Of Civil, Mechanical, & Manufact Inn ENG Directorate For Engineering |
| Start Date: | June 1, 2015 |
| End Date: | May 31, 2020 (Estimated) |
| Total Intended Award Amount: | $299,947.00 |
| Total Awarded Amount to Date: | $299,947.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
2200 VINE ST LINCOLN NE US 68503-2427 (402)472-3171 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
2200 Vine st, 151 Whittier Lincoln NE US 68588-0430 |
| Primary Place of Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): |
GOALI-Grnt Opp Acad Lia wIndus, NANOMANUFACTURING |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.041 |
ABSTRACT
Continuous carbon nanofibers have advantages over other nanomaterials in terms of cost, ease of handling, processing into useful applications, and possibility of their integration into multi-scale assemblies. However, their mechanical properties need to be substantially improved to improve processability. Due to the small scale of the nanofibers, it is difficult or impossible to use external mechanical constraints during processing that have been successfully utilized in manufacturing conventional larger-scale carbon fibers. Properly constrained nanofibers can match or exceed mechanical properties of conventional fibers; high mechanical performance coupled with low cost processing, small diameter, and ultrahigh surface area will open up broad new areas of nanofiber applications. This Grant Opportunity for Academic Liaison with Industry (GOALI) Program award supports fundamental research to provide needed knowledge for the development of an alternative approach utilizing internal constraints. Unlike the classical external constraint that is only applicable to aligned (one-dimensional) fiber tows, the new process will be applicable to both one-dimensional and two- and three-dimensional nanofiber constructs that can lead to revolutionary affordable high-performance bulk nanostructured carbon products. These multi-scale nanofilamentary structures can be used in a broad range of applications in aerospace, energy, environmental protection, healthcare, biomedical, and automotive industries. Therefore, results from this research will benefit the U.S. economy and society. This research involves several disciplines including manufacturing, electrodynamics process control, and materials science. The multi-disciplinary approach and collaboration with two companies will help broaden participation of underrepresented groups in research and positively impact engineering education.
This project's concept of internal constraint during nanomanufacturing of nanofibers can overcome the issues with the classical external mechanical constraint that is instrumental for high mechanical properties of conventional carbon fibers. However, several scientific barriers still need to be resolved to achieve carbon nanofibers? full potential. This research will study the mechanisms of nanofiber structure formation as a result of addition of small quantities of constraining nano-scale inclusions such as carbon nanotubes in all three stages of nanofiber manufacturing, i.e. electrospinning of nanofiber precursors, their oxidative stabilization, and high-temperature carbonization. The research team will perform extensive parametric studies to analyze processing-structure-properties relationships and to select optimal processing parameters for individual nanofibers and their aligned one-dimensional assemblies. Applicability of these parameters to nanomanufacture two- and three- dimensional macroscopic carbon nanofiber constructs in an integrated process will be then explored. The partnership of academic researchers with two companies will help focus this fundamental research on practical issues and will accelerate nanomanufacturing scale-up.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
The goal of this project was to explore a novel, potentially low-cost nanomanufacturing process to produce continuous carbon nanofibers (CNF) with enhanced graphitic structure and properties. We hypothesized that the above graphitic structure can be improved as a result of nanoinclusion-mediated internal constraint during fiber thermal treatment. The main objective of this project was to perform processing/structure/properties analysis and to study the mechanisms of structural changes. This was accomplished by investigating nanofiber structure formation during all three stages of carbon nanofiber fabrication, i.e. precursor spinning, oxidation/stabilization, and carbonization. Structure and properties of CNFs containing small amounts of 1D nanoinclusions were compared to pristine CNFs produced with and without application of external constraint. Several types of 1D inclusions were explored as orientation facilitators. Fabrication of aligned nanofiber sheets as precursors for layered two- and three-dimensional nanofiber assemblies was also studied and a new, potentially detrimental misalignment defect was identified and its formation mechanism explained.
Processability of several types of nanoinclusions into uniform continuous nanofibers was evaluated and successfully demonstrated. Characterization of structure and mechanical properties of as-spun nanofibers showed that addition of inclusions resulted in increased macromolecular chain orientation and decreased chain mobility in the inclusion-modified polymer precursor nanofibers. Examination of nanofiber shrinkage during thermal oxidation/stabilization showed that incorporation of nanoinclusions resulted in reduced fiber shrinkage, thus directly demonstrating the internal constraint. Characterization of macromolecular orientation in thermally annealed nanofibers showed enhanced retained orientation in the nanoinclusion-modified nanofibers that was on the par with externally constrained nanofibers, while orientation in unconstrained nanofibers was significantly lower. Finally, comparison of mechanical properties of carbonized CNFs fabricated with and without internal constraints showed that the internally constrained CNFs exhibited weaker size effects on properties with higher strength and modulus in the intermediate and larger diameter ranges. The latter discovery shows promise for improved inexpensive manufacturing of continuous CNFs as nanofibers with larger diameters are easier to produce uniformly at large scale.
Overall, the obtained results confirm feasibility of controlling structure and properties of CNFs by using 1D inclusions. Better understanding of mechanisms of structure formation will lead to development of improved nanomanufacturing processes. CNFs with improved structure and properties can be used in a broad variety of applications, including structural composites, coatings, high-temperature membranes, batteries, fuel cells, and biomedical applications. Our continuing collaboration with industrial researchers will help translate the results of this fundamental research into practice.
This grant partially supported research training of several graduate and undergraduate students. Their results have been presented at numerous Research Fairs as well as national and international conferences. Two undergraduate students won conference presentations awards at an international research congress. Several additional papers based on the results of this project, that were delayed due to the COVID pandemic, are being finalized and will be submitted and published.
Last Modified: 07/06/2021
Modified by: Yuris Dzenis
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