In this paper, a direct sustainable approach for the development of a n-ZnO:p-CuO heterojunction (ZCH) through a simple grinding is reported to be an effective technique to enhance the piezoelectric performance of ZCH/polydimethylsiloxane (PDMS) nanocomposite-based nanogenerators (ZP-PNGs). We have first optimized the best concentration for ZnO/PDMS nanocomposite for the realization of the piezoelectric nanogenerator. Later, with the same configuration, we implemented a novel, simple, facile, frugal, and inexpensive technique to fabricate ZCH. The heterojunction results in the improved charge transfer characteristics, low capacitance, and charge nullification contributing to the enhanced piezoelectric output. This reflects in the improvement of the peak-to-peak piezoelectric potential of the device from 2.7 to 9 V. The instantaneous max power density was found to be 0.2 mW/m2. The device can work as a force sensor with improved sensitivity of 1.7 V/N compared to 1.05 V/N of the intrinsic device. The device is being systematically studied for load matching and capacitor charging to demonstrate its practicability. Furthermore, we tested our device to harness the biomechanical energy from day-to-day life activities. Finally, the device was used to fabricate sustainable piezoelectric-based smart urinal systems for low-income group countries.

CuAlNi shape memory alloy (SMA) has wide scope in vibration damping applications for machine tools. A bespoke cold spray based additive manufacturing system was used to fabricate CuAlNi SMA precursor structures of two different compositions with optimized deposition parameters, which were subsequently alloyed via annealing. The two compositions of CuAlNi chosen for the study were Cu rich in wt% (Cu-82%, Al-14%, Ni-4%) and the Ni rich in wt% (Cu-12%, Al-2%, Ni-80%) shape memory alloy material. The various properties of developed samples were compared with commercially available CuAlNi structure. The properties compared include surface morphology, crystal structure, phase transformation temperature, and mechanical properties were studied with scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) compression testing respectively. The shape memory characteristics were also analyzed using dynamic mechanical analyzer (DMA). Among the two samples, Cu rich sample exhibited better SMA qualities than Ni rich sample as reported in the literature. The micro-hardness of Cu rich sample was to be 356 ± 3 VHN comparatively lower than Ni rich sample. The DSC results revealed the phase transformation hysteresis for Cu rich sample to be very low at 5 ± 3°C. The Cu rich CuAlNi SMA showed very good shape memory characteristics in the DMA results in the range of 50°C to 100°C.

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Incoloy 825 alloy is often used in calorifiers, propeller shafts, and tank vehicles owing to the improved resistance to aqueous corrosion. The electrochemical micromachining process can be utilized to machine such an engineering material owing to higher precision and lower tool wear. In the present study, an investigation was performed to enhance the process of creating micro-holes using silver-coated copper tool electrodes. The sodium nitrate electrolyte was used under different levels of input parameters such as voltage, electrolyte concentration, frequency, and duty cycle with a view to improving material removal rate, conicity, overcut, and circularity. It was found that silver-coated copper tool electrode had a high material removal rate (MRR), better overcut, conicity, and circularity compared to uncoated copper tools in most cases, due to its high corrosive resistance and electrical conductivity. From SEM and EDS analysis, it was observed that better surface topography of the micro-holes is obtained with silver-coated copper tool electrode while machining Incoloy 825 alloy in the micromachining process.