[CCoE Notice] Cullen College Dissertation Defense Announcement - Maninderjeet Singh_ChBE

[Hutchinson, Inez A]

[Dissertation Defense Announcement at the Cullen College of Engineering]
ELUCIDATING THE STRUCTURE-PROPERTY RELATIONS OF DIELECTRIC POLYMER FILMS FOR CAPACITIVE ENERGY STORAGE AND ELECTRONICS

Maninderjeet Singh
July 26, 2023;   12:00 PM

Room: Agrawal Building, AERB 222
ZOOM ID:
https://urldefense.com/v3/__https://us05web.zoom.us/j/88282103719?pwd=xit30ZjcAmRz0bIwxxeeutKG8s7aad.1__;!!LkSTlj0I!FKj0SURG4APYn-Q2FmIU3icJcTl4GgkwN5AhXIFktaNRc_-I6t2aqDjPpEWxbEAl8RUHobWMvyfQeZo7u3Qd8gH1IVk$ 
       Meeting ID: 882 8210 3719
                                                                      Passcode: w9mncu


Committee Chair:
Alamgir Karim, PhD
Committee Members:
Megan Robertson, Ph.D. | Jeremy Palmer, Ph.D. | Pradeep Sharma, Ph.D. |
Hadi Ghasemi, Ph.D. | Devin Shaffer, Ph.D
Abstract
The need for a sustainable future demands the development of high energy and power density energy storage devices. Dielectric capacitors are used as passive components of power and electronics devices. However, these capacitors have the potential to serve as high power density energy storage devices if their energy densities can be increased significantly. The maximum energy density of the dielectric capacitors is dictated by the permittivity and the dielectric strength of the dielectric media used in dielectric capacitors. To meet the requirements of the energy storage devices of the future, the permittivity, dielectric strength, and hence the energy density of the polymer and polymer nanocomposites dielectric need to be increased significantly. To achieve this, the fundamental mechanisms of dielectric polarization and breakdown need to be understood in detail.

As part of this thesis, we explore the mechanisms governing the dielectric breakdown and permittivity in polymeric dielectrics. To begin with, we test the free volume theory of dielectric breakdown by comparing the dielectric strength of cyclic polymers with linear polymers. We observe that cyclic polymers demonstrate higher dielectric strength and hence higher energy density as compared to linear polymers. We believe that this is due to the role of chain end-associated free volume in linear polymers, which is absent in cyclic polymers. Next, to compare the intrinsic dielectric strength of a polymer chain with the bulk films, we conducted a detailed analysis of the effect of polymer film thickness on the dielectric strength and observed that the dielectric strength increases significantly as the film thickness decreases below a micron. We correlate these observations to the observations of polymer stiffness in a thin film regime and find a strong correlation between the stiffness and dielectric strength.

To utilize the unique dielectric properties of 2D nanosheets in polymer nanocomposites, we developed a strategy for orienting the 2D nanosheets perpendicular to the electrical field. Due to the perpendicular orientation of the nanosheets, the nanosheets provide a barrier to the electrical breakdown trees and as a result, the dielectric strength increases significantly. Interestingly, we observe a strong enhancement in the dielectric permittivity as well for oriented nanosheet-based nanocomposites. As a result, we obtain an ultra-high energy density of ≈ 75 J/cm3, which is the highest reported energy density per unit mass to date. Polymer grafted nanoparticles (PGNPs) offer a unique way to alleviate the problems of nanoparticle aggregation in nanocomposite dielectrics. As part of this thesis, we studied the effect of polymer grafting density and polymer molecular weight on the dielectric properties of PGNPs. We observe the low grafting density PGNPs show the best performance due to the intermixing of polymer chains and a low number of voids. Overall, we believe that these results are expected to serve as guiding principles for designing high-energy density and efficient capacitors for the energy storage devices of the future.
[Engineered For What's Next]


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