Ultra-Stable and Durable Piezoelectric Nanogenerator with All-Weather Service Capability Based on N Doped 4H-SiC Nanohole Arrays

Ultra-stable piezoelectric nanogenerator (PENG) driven by environmental actuation sources with all-weather service capability is highly desirable. Here, the PENG based on N doped 4H-SiC nanohole arrays (NHAs) is proposed to harvest ambient energy under low/high temperature and relative humidity (RH) conditions. Finite element method simulation of N doped 4H-SiC NHAs in compression mode is developed to evaluate the relationship between nanohole diameter and piezoelectric performance. The density of short circuit current of the assembled PENG reaches 313 nA cm−2, which is 1.57 times the output of PENG based on N doped 4H-SiC nanowire arrays. The enhancement can be attributed to the existence of nanohole sidewalls in NHAs. All-weather service capability of the PENG is verified after being treated at -80/80 ℃ and 0%/100% RH for 50 days. The PENG is promising to be widely used in practice worldwide to harvest biomechanical energy and mechanical energy.

Enhancement Research on Piezoelectric Performance of Electrospun PVDF Fiber Membranes with Inorganic Reinforced Materials

The electrospun PVDF fiber membranes with the characteristics of light weight, strong signal and measurability, have been widely applied in the fields of environment, energy sensors and biomedical treatment. Due to the weakness of the piezoelectric and service properties, the conventional PVDF fiber membranes cannot meet the operating requirements. Based on the obtained optimal technological parameter of electrospun pure PVDF fiber membranes (P-PVDF) in the previous experiment (unpublished), three inorganic reinforced substances (AgNO3, FeCl3·6H2O, nanographene) were respectively used to dope and modify PVDF to prepare composite fiber membranes with the better piezoelectric performance. The morphology and crystal structure of the hybrid fiber membranes were observed and detected by scanning electron microscopy and X-ray diffraction, respectively. The results showed that the dopant could effectively promote the formation of β-phase, which can enhance the piezoelectric performance. The mechanical properties test and piezoelectric performance test exhibited that the static flexural strength, the elastic modulus, and the piezoelectric performance were improved with the addition of dopant. In addition, the influence on the addition of dopant and the doping modification mechanism were discussed. Finally, the conclusions showed that the minimum average diameter was obtained with the 0.3 wt% addition of AgNO3; the piezoelectric performance reached the strongest with the 0.8 wt% addition of FeCl3·6H2O; the mechanical properties were best with the 1.0 wt% addition of nanographene.

Theoretical modeling of longitudinal piezoelectric characteristic for cellular polymers

Efficient energy harvesting is a difficult challenge that consists in the development of systems allowing charging autonomous and low-power devices. In addition to traditional piezoelectric polymers, mono-crystals, and ceramics, cellular electrets offer consistent solutions by converting wasted vibration energy from the environment to usable electrical energy. This paper presents an electromechanical model to study the energy harvesting capability of cellular polymers. The theoretical study models the response of these materials to investigate the effect of different parameters on the piezoelectric coefficient d33, particularly. The model considers the percentage of porosity, surface charge density in each polymer–gas surface, the properties of the polymer matrix and the gas encapsulated in the pores, and the Young’s modulus of the porous film. For poly(ethylene-co-vinyl acetate), the results showed that the piezoelectric performance of the film declines with the increase of the film thickness. However, the variation of the d33 as a function of the percentage of porosity is exponential and can achieve 4.24 pC/N for a porosity of 80%. Compared to a previously published experiment, the theoretical results have proven a good agreement with only 3.3% error.