2018 Fiscal Year Research-status Report
Experimental tuning of 2D heat conduction and thermoelectric conversion based on shape control
| Project/Area Number |
18K13704
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| Research Institution | Kyushu University |
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Principal Investigator |
李 秦宜 九州大学, 工学研究院, 助教 (60792041)
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| Project Period (FY) |
2018-04-01 – 2020-03-31
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| Keywords | graphene nanoribbons / thermal conductivity / electrical conductivity / Seebeck coefficient / figure of merit / 2D materials / size effect |
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| Outline of Annual Research Achievements |
Tuning thermal transport and thermoelectric properties of graphene is of great importance for both nanoscale thermal science and energy harvesting applications. In this year, we successfully developed an 8-terminal method to comprehensively measure the three thermoelectric properties of nanomaterials, fabricated as-grown free-standing graphene nanoribbons through collaboration with Tohoku University, measured record-high thermoelectric performance of graphene, and theoretically revealed quasi-ballistic phonon transport in the measured samples through collaboration with Purdue University. The size-controlled suspended graphene nanoribbons had a low level of defects due to the as-grown synthesis process. The ratio of electrical to thermal conductivity was enhanced by 1-2 orders of magnitude, and the Seebeck coefficient was several times larger than bulk graphene. As a result, the thermoelectric figure of merit reached record-high values of ~0.1. Moreover, we observed record-high electronic contribution of ~20% to the total thermal conductivity in the nanoribbon. Phonon Bolztmann transport equation simulations reveal that these experimental findings were mainly enabled by the disparate electron and phonon mean free paths. Our work has demonstrated that electron and phonon transport can be fundamentally tuned and decoupled by size and defect control in graphene. In addition, we developed transient non-contact Raman methods to measure thermal properties of 2D materials and van der Waals heterostructures, which will allow comparative measurements using different methods.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The measurements and the collaboration with the synthesis group at Tohoku University are going very smoothly as planned. We have held several meetings at Tohoku University about the collaboration research. We have also established collaboration relationship with the famous group of phonon theories at Purdue University. Through efficient Japan-US collaboration, we have achieved record-high thermoelectric performance of graphene. I have presented the experimental results at an international conference in Finland, and submitted a journal paper on the thermoelectric performance of graphene nanoribbons. In addition, I have also developed non-contact methods to measure thermal properties of 2D materials.
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| Strategy for Future Research Activity |
In FY2019, I will change the sizes and shapes of the graphene nanoribbons and hope to further enhance the thermoelectric performance of graphene to an unprecedented level. I plan to reveal the physical mechanism of shape dependent thermal and thermoelectric properties by combining both experiments and simulations. In addition, I will continue to develop non-contact methods to measure thermal properties of 2D materials and compare the measurements using different methods.
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| Causes of Carryover |
Because we developed the measurement methods all by ourselves with no need of additional personnel, the personnel expenditure and remuneration were zero. Because we only successfully measured a small number of samples and the results have not been published yet, the related expenses were less than planned.
However, in FY2019, as we have started collaboration with Purdue University and more results will be measured and published, the income will be used for experimental costs, research collaborations and publications.
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Research Products
(12 results)
