Dr. K Suresh Chary, DRDO Scientist

Thesis Abstract:

In recent times so much development has taken place in modern electronic systems. As

technology grows, there is an increasing need of portable electronic devices in the field of

defence as well as different daily life activities. However use of batteries as power source for

these portable electronics is limited by it's service life. Hence, there is a demand for

portable, sustained and continuously self-operable energy generators. The Piezoelectric

Nanogenerator is one of the suitable technologies to harvest ambient mechanical energy

from the surroundings and convert it into electricity, ready to supply for portable electronic

devices. However, there are many technical barriers in fabrication and preparation of desired

quality of nanogenerators on an industrial scale. The present work is designed to develop

lead-free ceramic nanofibers based piezoelectric nanogenerator for energy harvesting and

sensor applications.

In this work, it was attempted to produce and characterize different lead-free ceramic

nanofibers with large aspect ratio such as Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) and 0.2 Y2O3-

Ba(Sn0.04Ti0.96)O3 (Y2O3-BST) nanofibers by sol-gel followed by electrospinning. Studies on

structural and morphology of ceramic nanofibers (BCZT, Y2O3-BST) were carried out, to

determine the crystal structure and microstructure of sintered fibers. It was revealed that

there is an enhancement (20-30 °C) of Curie temperature of nano-fibers compared to that of

bulk ceramics for given composition. Present research work also deals with design and

fabrication of ceramic nanofibers based flexible nanogenerators using cost-effective and

scalable process. The developed BCZT nanofibers based nanogenerator exhibited an output

voltage of 2.68 V with maximum power of 2.95 μW for energy harvesting application. BSTY2O3

nanofiber based nanogenerator exhibited significantly higher output voltage of 25 V

with maximum power of 12 μW. Further, nanogenerators were explored for possible

applications as energy harvester and self-powered frequency sensor.

xiii The current work demonstrates the synthesis of one-dimensional (1D) antimony doped

potassium sodium niobate (KNNSb) nanorods (NRs) by hydrothermal process. A new

approach has been adopted to prepare KNNSb NRs/PVDF-HFP composite nanofibers used

for fabricating nanogenerator with more flexibility and ease of handling. Crystal structure

and morphology analysis of KNNSb NRs and composite nano-fibers were carried out using

various analytical techniques. The impact of the KNNSb nanostructures on the dielectric

properties of KNNSb NRs/ PVDF-HFP composite nanofibers was investigated. In addition,

the feasibility study of KNNSb/PVDF-HFP composite nanofiber-based nanogenerator as a

pressure sensor for thermal management of heat-pipe was also carried out.

Further, fabrication of surface modified BCZT nanofibers/ PVDF-HFP based composite film

has been carried out for similar objectives. Surface modification of nanofibers with

dopamine hydrochloride has been performed to enhance the dielectric properties with

reduced dielectric losses for resultant nanocomposite. The developed nanofibers and

nanocomposite films were analyzed by XRD and FE-SEM to investigate crystal structure

and morphology respectively. Dielectric studies were carried out in a wide range of

frequencies and temperature to know the dielectric behavior of the nanocomposite. Finally,

this work also deals with fabrication and performance evaluation of nanocomposite film

based flexible nanogenerator (NG).