Term of Award

Summer 2019

Degree Name

Master of Science, Mechanical Engineering

Document Type and Release Option

Thesis (restricted to Georgia Southern)

Copyright Statement / License for Reuse

Digital Commons@Georgia Southern License

Department

Department of Mechanical Engineering

Committee Chair

Mujibur Khan

Committee Member 1

Aniruddha Mitra

Committee Member 2

Anoop Desai

Abstract

The effect of corona treatment on piezoelectric property of Poly (vinylidene fluoride) (PVDF) nanofibers (NFs), multi-wall carbon nanotube (MWCNT) reinforced PVDF NFs and Polyacrylonitrle (PAN) NFs membrane were investigated. All the NFs were produced by electrospinning process using NF-500 electrospinning unit. PVDF-Dimethylformamide (DMF) solution was prepared and electrospun using optimum parameters. Similarly, PAN-DMF solution was also electrospun to fabricate PAN NFs. In another case, MWCNTs were dispersed in DMF using ultrasonic process and then PVDF was dissolved & stirred to make a complete homogenous mixture for electrospinning. To investigate the piezoelectric property, four categories of samples were prepared: control, heat treated (at 1000C), corona treated, and corona and heat treated. Corona (plasma) treatment was applied on NF membranes at 6kV with 1mA current flow. Using Scanning Electron Microscope (SEM), the morphology of the NFs was observed to be in the nanoscale. Fourier Transform Infrared Spectroscopy (FTIR) analysis of PVDF NFs shows peak at 796cm-1 representing α-phase (C-H rocking) in control sample which is absent in the treated samples. Raman spectroscopy of PVDF NFs identifies raman shift from 873cm-1 to 877cm-1 (denoting β-phase) for corona treated samples only. Electro Paramagnetic Resonance (EPR) concludes that intensity of free radicals increases from 1.37 to 1.46 (a.u.) which is 8% of the original after corona treatment. Sensors were fabricated from the NF membranes for piezoelectric testing. Drop ball tests were performed to measure the output voltage response of the NF sensors. Oscilloscope signals indicate high voltage output response for treated samples, whereas only 1mV voltage spike is observed for control samples. After the corona treatment, piezoelectric coefficient d33 of pristine PVDF NFs was increased from 0 to 102pC/N, for MWCNT reinforced PVDF NFs d33 increased from 0 to 52pC/N and for pristine PAN NFs d33 increased from 0 to 75 pC/N. However, we also tested a macro-scale PVDF film after corona treatment and observed d33 value 26 pC/N. So, the corona effect to the macro-scale membrane was not as high as nanoscale. On the other hand, corona treated PVDF samples show the highest d33 value, while the MWCNT reinforced PVDF samples show the maximum capacitance (0.93 nF), which is almost double compared to pristine PVDF membranes and pristine PAN membranes. This study provides strong support regarding the effectiveness of corona treatment to induce piezoelectric properties on electrospun NFs. The research will serve as a baseline for future work on scaling up the fabrication of novel polymer nanofiber composites with enhanced piezoelectric property for the purpose of energy harvesting.

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