In this study, modified epoxy nanocomposite was produced by incorporating SiO₂ nanoparticles of 15–30 nm in size, with different concentrations ranging from 1 to 20 wt%. The electrical properties of the epoxy nanocomposite were measured at room temperature in the frequency range of 10⁻²–10⁷ Hz. To determine the impact of nanoparticles on the epoxy composition, scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDS), Fourier transform infrared spectra (FTIR) spectroscopy, and Raman spectroscopy were conducted. With an increase in filler (SiO₂ nanoparticles) content, the electrical characteristics of the epoxy nanocomposite exhibited multiple changes. At low concentrations, all electrical properties experienced a notable increase. The epoxy with 15 wt% of SiO₂ nanoparticles samples had a lower permittivity, loss number, conductivity, and capacitance than the unfilled epoxy. At medium concentrations (5 to 15 wt%), the formation of immobilized nanolayers has an impact on permittivity, loss number, conductivity, and capacitance, which have decreased; impedance and modulus increased. The initiation of contact between the nanofillers at a concentration of 20 wt% leads to the formation of continuous interfacial conductive pathways, resulting in a dramatic increase in the permittivity, conductivity, and capacitance of the composites, while concurrently reducing impedance.

This work studies the direct current breakdown characteristics of unfilled epoxy and epoxy nonconductive nanocomposites (${\mathrm{S}\mathrm{i}\mathrm{O}}_2,\mathrm{M}\mathrm{g}\mathrm{O}$ and ${\mathrm{A}\mathrm{l}}_2{\mathrm{O}}_3$). It also examines the variation of electrical properties in epoxy nanocomposites. The novel aspect of this study is that the samples of Epoxy nanocomposite were exposed to high voltages of up to six kilo volts for three hours using field electron microscopy under high vacuum conditions (${10}^{-5}$ mbar). The current emitted from these samples was measured at three different intervals of time. In addition, the influence of high voltage on the permittivity, loss factor (tan(δ)), and conductivity of the epoxy nanocomposite was studied. This evaluation was conducted before and after applying the voltage at room temperature, The frequency range extends from ${10}^{-2}$–${10}^{-7}$ Hz using the Novo Control Alpha-A analyzer. Current–voltage characterization was performed through field electron microscopy. The samples were characterized by scanning electron microscopy–energy dispersive X-ray spectroscopy and Fourier Transform Infrared Spectroscopy. The unfilled epoxy exhibited structural degradation, resulting in the formation of holes when exposed to high voltages of up to six kilo volts, leading to a reduction in electrical properties. Nevertheless, the addition of nanoparticles shows a significant increase in the operational lifetime of the epoxy nanocomposite. The degree of increase in the lifetime of epoxy composite varied depending on several factors such as the type of NPs introduced and their respective sizes. The epoxy/${\mathrm{A}\mathrm{l}}_2{\mathrm{O}}_3$ nanocomposite comparing with epoxy/MgO and epoxy/${\mathrm{S}\mathrm{i}\mathrm{O}}_2$ nanocomposite showed elevated resistance to direct current breakdown strength and maintaining its dielectric.

The electrical properties and activation energy of epoxy/graphite flakes (GFs) micro-composite with different content of GFs (0.0625–1 wt%) were studied for electrical properties using Novocontrol Alpha Analyser (10⁻² Hz—10⁷ Hz). GFs sizes ranged from (100 nm to 10 μm). The analysis was performed by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), visible spectrum reflectance spectra (VIS) spectra, and Fourier Transform Infrared spectra (FTIR) spectroscopy. Increasing GFs content caused multiple changes in electrical characteristics. At 0.0625 wt%, all electrical properties noticeably increased. But at 0.125 to 0.25 wt%, immobilized nanolayers were formed leading to decreased permittivity, dielectric loss (tan(δ)), quality factor (Q-factor), capacitance, conductivity, and figure of merit (F-factor). At 0.25 wt%, the epoxy microcomposite had lower permittivity, tan(δ), conductivity, and capacitance compared with unfilled epoxy. With 0.5 wt% of GFs, signified the percolation threshold, initiating a rise in permittivity, conductivity, capacitance, and tan(δ), accompanied by the closer proximity of grain boundaries, facilitating the formation of conductive channels. At a concentration of 1 wt% of GFs, the establishment of continuous interfacial conductive pathways resulted in a remarkable augmentation of all dielectric properties. The Cole-Cole analysis has been employed to investigate variations in epoxy/GFs microcomposites based on concentration levels.

The aim of this work was to study the dielectric properties of dot capacitors composed of a microtip coated with a thin layer of epoxy resin bonded to a steel plate. Two microtips with radii ranging from 3 to 5 μm were fabricated via electrochemical etching and coated with an epoxy layer 27-35 μm in thickness. The microtips were characterized by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). This study showed that composite cold-field emission emitters behave as dot capacitors. The real and imaginary parts of the impedance and permittivity, along with the direct and alternating conductivities, activation energies, and hopping energies, were examined. These evaluations were conducted at temperatures of 30, 45, 60, 75, and 90 °C, with a frequency range of 1 to 10⁶ Hz using impedance spectroscopy. The results indicated that both the impedance and electrical permittivity decreased slightly with increasing temperature, whereas the AC conductivity was independent of temperature. Additionally, a decrease in the activation and jump energies was observed as the thickness of the epoxy layer increased. The low values of the activation and hopping energies facilitated electron transport through the epoxy layer. The modified hopping model also provides an explanation for the conduction mechanism through the epoxy layer. The Nyquist plot shows that the capacitance decreased with increasing temperature. A slight increase in relaxation time was also observed, indicating the onset of conductive pathway formation. These findings contribute to a better understanding of the capacitance of the composite emitters and the formation of conductive pathways.

This study investigates electron emission from copper broad-area emitters (CBAEs) and copper broad-area composite emitters (CBACEs) based on the principles of trapping and conductive pathways. Emission current measurements were conducted on two CBACEs, which consisted of copper coated with a 300–400 μm epoxy resin and subjected to high voltages up to 15 kV. The research specifically examines the ‘switch-on’ and collapse phenomena occurring within the epoxy layer. Field emission microscopy (FEM) was utilized in a high-vacuum environment ( 10 − 6 mbar) to observe these effects. A comprehensive model is developed to explain the formation of conductive pathways within the epoxy layer, allowing electrons transfer from traps to the surface. This model treats the composite emitter as a trap-rich capacitor. The study also clarifies the effects of trap density and epoxy layer thickness on the collapse process. To gain a deeper understanding of the model, changes in the I-V curve were examined. Simulations, scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDX) images, and Fourier transform infrared spectroscopy (FTIR) analysis were employed to understand the collapse mechanism of the epoxy collapse. Additionally, Nyquist and Cole–Cole plots were analyzed across frequencies ranging from 1 to 10 6 Hz before and after applying a high electric field on the samples, revealing changes in the capacitive component and the role of diodes in the formation of conductive channels.

In this study, the thickness of a thin film (t_c) at a low primary electron energy of less than or equal to 10 keV was calculated using electron energy-loss spectroscopy. This method uses the ratio of the intensity of the transmitted background spectrum to the intensity of the transmission electrons with zero-loss energy (elastic) in the presence of an accurate average inelastic free path length (λ). The Monte Carlo model was used to simulate the interaction between the electron beam and the tested thin films. The total background of the transmitted electrons is considered to be the electron transmitting the film with an energy above 50 eV to eliminate the effect of the secondary electrons. The method was used at low primary electron energy to measure the thickness (t) of C, Si, Cr, Cu, Ag, and Au films below 12 nm. For the C and Si films, the accuracy of the thickness calculation increased as the energy of the primary electrons and thickness of the film increased. However, for heavy elements, the accuracy of the film thickness calculations increased as the primary electron energy increased and the film thickness decreased. High accuracy (with 2% uncertainty) in the measurement of C and Si thin films was observed at large thicknesses and 10 keV, where $\frac{t}{\mathsf{\lambda }}\approx 1$. However, in the case of heavy-element films, the highest accuracy (with an uncertainty below 8%) was found for thin thicknesses and 10 keV, where $\frac{t}{\mathsf{\lambda }}\le 0.29$. The present results show that an accurate film thickness measurement can be obtained at primary electron energy equal to or less than 10 keV and a ratio of $\frac{t}{\mathsf{\lambda }}\le 2$. This method demonstrates the potential of low-loss electron energy-loss spectroscopy in transmission electron microscopy as a fast and straightforward method for determining the thin-film thickness of the material under investigation at low primary electron energies.