Title Page

Contents

Abstract 12

Chapter 1. INTRODUCTION 14

Chapter 2. EXPERIMENTS 20

2.1. Materials 20

A. Preparation of materials 20

B. Preparation of kraft, hydrophilic, and hydrophobic lignins 20

2.2. Experimental details 22

A. Electrospinning for nanofiber mat 22

B. Fabrication of lignin/polycaprolactone nanofiber-based triboelectric nanogenerators 24

C. Physicochemical properties 26

D. Energy-harvesting performance 26

E. Other characterizations 27

Chapter 3. RESULTS AND DISCUSSIONS 28

3.1. Mechanical properties of lignin/polycaprolactone nanofibers 28

3.2. Physicochemical properties of lignin/polycaprolactone nanofibers 34

3.3. Energy-harvesting performance of lignin/polycaprolactone nanofiber-based triboelectric nanogenerators 45

Chapter 4. CONCLUSION 58

References 59

논문요약 67

Table 1. Mw of kraft, hydrophilic, and hydrophobic lignins.[이미지참조] 22

Table 2. FTIR band assignments of kraft lignin. 38

Table 3. Comparison of materials, methods, and performances of the previously-reported tribopositive biomaterial-based TENGs. 50

Table 4. Parameters for COMSOL simulation. 54

Figure 1. Synthetic pathway of hydrophilic lignin (HIL). 17

Figure 2. Synthetic pathway of hydrophobic lignin (HOL). 17

Figure 3. Schematic of the process employed to transform KL into HIL and HOL and the operating mechanism of LP-TENG as an energy harvester. 19

Figure 4. Schematic of the process of synthesizing KL into (a) HIL and (b) HOL powders. 21

Figure 5. Schematic of (a) the tribo-positive (LP NF mat) and -negative (teflon tape) layers for energy-harvesting performance test and photos of (b) LP NF... 25

Figure 6. Photos and SEM images of electrospun NF mats of (a) KLP, (b) HILP, and (c) HOLP cases. 29

Figure 7. SEM images of the pristine PCL NF mat. 29

Figure 8. Photos of KLP, HILP, and HOL powders and solutions. 30

Figure 9. Fiber size distributions of (a) KLP, (b) HILP, (c) HOLP, and the (d) pristine PCL cases. 31

Figure 10. Stress-strain curves for (a) KLP, (b) HILP, (c) HOLP, and the pristine (d) PCL NF mats. 33

Figure 11. ¹H NMR spectra of KL, HIL, and HOL powders. 35

Figure 12. FTIR spectra of KLP, HILP, and HOLP NF mats. 37

Figure 13. FTIR spectra of KL, HIL, and HOL powders. 37

Figure 14. XRD patterns of KL, HIL, and HOL powders. 41

Figure 15. XRD patterns of KLP, HILP, and HOLP NF mats. 41

Figure 16. TG curves of KLP, HILP, and HOLP NF mats. 43

Figure 17. Water contact angles of KLP, HILP, and HOLP NF mats. 44

Figure 18. Surface potential (φ) of HILP and HOLP NF mats. 45

Figure 19. V signals of the KLP, HILP, and HOLP-TENGs with (a, c) varying F from 3 to 9 N with a fixed f of 9 Hz and (b, d) varying f from 3 to 9 Hz... 48

Figure 20. Cyclic tapping tests of the KLP-, HILP-, and HOLP-TENGs for 100,000 cycles. 49

Figure 21. (a) V signals of the KLP, HILP and HOLP-TENGs during 100,000 cycles. (b) A short-circuit I signal of the HOLP-TENG. (c) A cyclic tapping... 49

Figure 22. η vs. S for the previously-reported tribopositive biopolymer-based TENGs. 51

Figure 23. (a) Vptop and (b) Iptop as a function of R ranging from 10⁵ to 10⁹Ω.[이미지참조] 52

Figure 24. Corresponding P and PS⁻¹. 53

Figure 25. Simulation results obtained using COMSOL. 55

Figure 26. Accumulated V signals for different capacitors. 56

Figure 27. (a) LED operation using the HILP-TENG. (b) V signals obtained from the HILP-HOLP-TENG during walking and running. 57