Transient liquid phase bonding of nickel foams by boron nitride nanoparticles synthesized via electrospinning method for triboelectric nanogenerator application

نوع: Type: Thesis

مقطع: Segment: masters

عنوان: Title: Transient liquid phase bonding of nickel foams by boron nitride nanoparticles synthesized via electrospinning method for triboelectric nanogenerator application

ارائه دهنده: Provider: Negin Javanmard

اساتید راهنما: Supervisors: Dr Hamid Esfahani , Dr Mohsen Sheikhi

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: Dr Karbasi , Dr Damavandi

زمان و تاریخ ارائه: Time and date of presentation: 2026

مکان ارائه: Place of presentation: سالن کنفرانس دانشکده مهندسی

چکیده: Abstract: : In this study, nanostructured boron nitride particles were synthesized and evaluated with the dual objectives of investigating their role in nickel foam bonding and improving the performance of PVDF fiber-based energy harvesting systems. In the first step, the precursor solution was prepared and transformed into amorphous fibers by electrospinning. Then, they were calcined at 900°C. The results showed that after calcination, the fiber morphology was transformed into agglomerates of nanoparticles (average particle size 550 nm) with the crystallography of hexagonal boron nitride (h-BN) phase. In the second step, the bonding of nickel foam and nickel-based discs was performed by transient liquid phase (TLP) method at 1050°C, holding time 2 hours using fiber interlayers containing BN. For this purpose, two types of designs were used including a single-layer sample and an intermediate layer sample with additional amorphous powder. The results showed that the presence of additional amorphous boron improved the interface, made it denser and more uniform, and reduced porosity, shrinkage cracks, and irregular aggregation. Also, the distribution of fine particles related to nickel borides was observed. In the third step, PVDF–BN fibers with concentrations of 0.5 and 1 wt% of nanostructured BN particles were investigated for use in energy harvesting by the triboelectric method. The results showed that the addition of BN to PVDF, despite having a negative charge (zeta potential difference of -42.3 mV), reduced the amount of electroactive β phase in the PVDF fiber matrix (6.6%). However, the addition of nanostructured BN particles increased the dielectric constant, and the piezoelectric coefficient decreased with the addition of nanostructured BN particles. The results of triboelectric tests in contact-separation and sliding modes showed that the addition of nanostructured BN particles to the PVDF fiber matrix improved the open circuit voltage (values 144 and 148 mV), current density (values 0.796 and 0.318 mA/cm2(, and power density )values 0.079 and 0.012 W/m2(. Overall, the results of this study showed that the electrospinning and heat treatment method provides a suitable route for the production of h-BN nanostructures; the multilayer design of the fiber layer based on nanostructured BN particles provides the conditions for the connection of nickel parts. In addition, the addition of the optimal amount of BN to PVDF can significantly increase the triboelectric and piezoelectric behavior and, consequently, the efficiency of energy harvesting systems