In this study, we investigated the effect of zirconium content on lead-free barium zirconate titanate (BZT) (Ba(Zr_xTi_1−x)O₃, with x = 0.00, 0.01, 0.03, 0.05, and 0.08), which was prepared by the sol–gel method. A single-phase perovskite BZT was obtained under calcination and sintering conditions at 1100 °C and 1300 °C. Ferroelectric measurements revealed that the Curie temperature of BaTiO₃ was 399 K, and the transition temperature decreased with increasing zirconium content. At the Curie temperature, Ba(Zr_0.03Ti_0.97)O₃ with a dielectric constant of 19,600 showed the best performance in converting supplied mechanical vibration into electrical power. The experiments focused on piezoelectric activity at a low vibrating frequency, and the output power that dissipated from the BZT system at 15 Hz was 2.47 nW (30 MΩ). The prepared lead-free sol–gel BZT is promising for energy-harvesting applications considering that the normal frequencies of ambient vibration sources are less than 100 Hz.

The present work has investigated a means of fabricating porous,  phase P(VDF-HFP) film by adding two kinds of hydrated metal salts. Without the use of mechanical stretching or electrical poling treatments, MgCl2•6H2O and AlCl3•6H2O are found to induce the formation of  phase crystals in porous film derived from the solution casting method. Trivalent Al ions have been found to effectively promote the self-oriented electroactive phase of the P(VDF-HFP) film greater than divalent Mg ions. Increases in the pore sizes with increasing salt concentration raise the degree of surface roughness and the formation of electret dipoles. Values of the dielectric constant of about 5 for pure P(VDF-HFP) film over the frequency range below 200 Hz has been boosted up to 10-20 when adding the salts. In addition, all the films have low dielectric loss tangent. The modified polymers are attractive to be used in energy harvesting on ambient vibration at low level (<200 Hz).

Fe and Cu powders were mixed at a 50:50 ratio. Then, Fe-Cu alloys were prepared using the ball milling technique with different milling times of 6, 12, 18, 24, 30, 36, and 42 h. The crystalline structure was analyzed using X-ray diffraction (XRD), and it was found that the optimum milling time was 30 h. The homogeneity of the Fe and Cu elements in the Fe–Cu alloys was analyzed using the scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM–EDX) mapping technique. Additionally, the crystal orientation of the Fe–Cu alloys was investigated using transmission electron microscopy (TEM). To fabricate the cathode for nitrate removal via electrolysis, an Fe–Cu alloy milled for 30 h was deposited onto a copper substrate using mechanical milling, then annealed at 800 °C. A pulsed DC electrolysis method was developed to test the nitrate removal efficiency of the Fe–Cu-coated cathode. The anode used was an Al sheet. The synthesized wastewater was prepared from KNO₃. Nitrate removal experiments from the synthesized wastewater were performed for durations of 0–4 h. The results show that the nitrate removal efficiency at 4 h was 96.90% compared to 74.40% with the Cu cathode.

This work focuses on an improvement of dielectric properties of poly(vinylidene fluoride-co-hexafluoropropylene) or P(VDF-HFP) via mixing with different nickel(II) chloride hexahydrate (NiCl₂⋅6H₂O) contents (0–2 wt%). The nanocomposite films have been prepared by a conventional solution technique. The results reveal that the surface roughness increases with increasing salt content. The NiCl₂⋅6H₂O salt has no significant effect on the crystallinity of films. Additional incorporation of NiCl₂⋅6H₂O in the polymer leads to the growing conductivity. However, the considerable enhancement in dielectric constant with the relatively low dielectric loss tangent (0.1–0.3) can be found because of the formation of β-phase nucleation of NiCl₂⋅6H₂O in the P(VDF-HFP) matrix. The maximum value of calculated β-phase fraction of the nanocomposite is achieved 86% for salt content 0.5 wt%. Moreover, the largest dielectric constant (29.2 at 10 Hz) of the film doped 2 wt% NiCl₂⋅6H₂O is about 7 times greater than that of the pure P(VDF-HFP). The findings in this research suggest that the NiCl₂⋅6H₂O/P(VDF-HFP) nanocomposite is a candidate dielectric material for the next generation of energy conversion components.