Characteristics Of Nanofillers Research Articles

Abnormal volatile and normal stable bipolar resistive switching characteristics of hybrid nanocomposites: Morphology–defects–property ‘Relationship

The characteristics of nano-fillers in a polymer matrix have a significant influence on the microstructural, thermo-mechanical, optical, and conductivity properties of organic-inorganic nanocomposites. In this study, we investigated the influence of inorganic component – ZnO nanoparticles (NPs) on the characteristics and properties of PVA-ZnO nanocomposites which have been applied as an insulation layer in a resistive switching (RS) device. Three nanocomposites originating from three different types of ZnO NPs exhibit different RS characteristics: Abnormal volatile RS is observed with the ∼20-nm-sized spherical-like NPs (Z1) and 15–20-nm-sized mixed shaped NPs (Z2), whereas normal nonvolatile bipolar RS is observed with the 50–150-nm-sized hexagonal rod-like NPs (Z3). The concentration and size of the intrinsic defects of the ZnO NPs as well as the thickness of the PVA-ZnO interface are responsible for the different charge transport paths, operating voltage ranges, and ON/OFF switching ratios of the memory devices. Simultaneously, the distinct sizes and morphologies of the ZnO NPs can affect the nanoholes among the PVA chains and induce various fractional free volumes in the nanocomposites. It may modify the conductivity of the nanocomposite layer or the resistance ratio of the memory devices. Understanding the influence of ZnO NPs size, morphology, and defects on the characteristics of RS of PVA-ZnO nanocomposites can help in the selection and management of functional applications, especially in the data storage field.

THE MECHANISMS OF REINFORCEMENT OF NANOCOMPOSITES POLYURETHANE/CARBON NANOTUBE

The aim of present work is theoretical analysis of high values of reinforcement degree of nanocomposites polyurethane/carbon nanotube. For this two micromechanical models were used, showing identical results. The indicated models demonstrated, that densely-packed high-modulus interfacial regions, which serve the same reinforcing element of nanocomposite structure, as and nanofiller (carbon nanotubes) actually. The formation of interfacial regions defines by strong interactions polymer matrix – nanofiller. This means that nanofiller efficiency is controlled by its ability to generate densely-packed interfacial regions. It is important also to point out, that any micromechanical model, including mixtures rule, describes correctly modulus of elasticity of polymer nanocomposites, if in it real, but not nominal, characteristics of nanofiller were used. The content of interfacial regions in nanocomposite is controlled by structure of nanofiller. This allows to obtain important practical conclusion – for realization maximum degree of reinforcement it is necessary to cause structure of nanofiller, allowing to generate greatest content of interfacial regions. Absence of interfacial regions results to reduction of modulus of elasticity of nanocomposite in comparison with matrix polymer.

Analysis of Partial Discharge Signal Characteristics of Nano-Mineral Oil for Transformer Condition Monitoring Applications

Transformer is an expensive and key component in an electric power transmission network. Most of the failure of transformer occurs due to degradation of insulation oil, which further leads to major economical losses and power shutdown. Advancements in nanotechnology has given horizons for the development of nanofluids for transformer insulation applications. Understanding the enhancements in dielectric properties of nanofiller added mineral oil is a hot research area. In recent times, partial discharge (PD) detection and analysis is a well recognized insulation condition monitoring technique for transformers. However, reports on PD signal characteristics of nano filler added mineral oil is scanty. This paper attempts to investigate the PD characteristics of SiO2 nanofiller added mineral oil at different %wt concentrations of nanofiller material. Major PD source normally experienced in transformers i.e. corona discharge due to non-uniform electric field was simulated in the laboratory using needle-plane electrode configuration and the corresponding PD signals were measured using wide band PD detection system. Important PD characteristics such as inception voltage, stable PD formation voltage, PD amplitude with respect to increase in voltage stress and PD signal frequency spectrum were evaluated. Results clearly show that addition of SiO2 nanofiller material in the base mineral oil enhances PD performance of mineral oil and these results will be useful for electrical utilities for developing effective condition monitoring system for transformers.