Sep 2026· Journal of the Physical Society of Japan· 0 citations· 10 references
Abstract
To investigate the influence of electrode surface roughness on gas discharge characteristics under micro-gap conditions, direct-current breakdown experiments were carried out in atmospheric air using a nano-positioning system. Breakdown tests were conducted for five metal electrodes over the electrode gap distances from 1 to 10 µm, and for one metal with different surface roughness levels over the electrode gap distances from 1 to 20 µm. Meanwhile, the electric field intensity distribution of aluminum electrodes (cathode) with different surface roughness values was simulated using Maxwell electromagnetic field simulation software. The experimental results show that, in the electrode gap distances from 1 to 5 µm, different metal electrodes exhibit different degrees of deviation from the Paschen curve, all of which are related to the work function. At the same electrode gap distance, the rougher the electrode surface, the larger the field enhancement factor β and the lower the breakdown voltage. Analysis indicates that surface protrusions cause local electric field intensification, allowing the field strength to reach the critical condition for field electron emission, thereby reducing the breakdown voltage. In the electrode gap distances from 10 to 20 µm, electrode surface roughness leads to a multiplication of the effective electron emission from the cathode surface, thus enhancing the surface electron emission process. Therefore, in the design of microelectronic devices, reducing electrode surface roughness and selecting metal electrode materials with higher work functions can effectively improve gas breakdown characteristics under small-gap conditions and optimize the insulation protection of microelectronic devices.
This research investigates the influence of cathode surface roughness on DC breakdown voltages and pre-discharge currents in pressurized synthetic air. A physics-based computational model is presented for predicting breakdown voltages in insulating gases under high-voltage stress. The model combines electron ionization and attachment processes along the discharge path to calculate the evolution of the primary electron avalanche. The model considers gas pressure, gap distance, electrode geometry and electric field distortions due to electron avalanches, and had been validated with a huge number of experimental breakdown measurement series with smooth electrode geometries in synthetic air. In the present work this model is extended to include the influence of electrode surface roughness on breakdown behavior. To accomplish this, cathodes with varying roughness levels were characterized using laser scanning microscopy and corresponding local field enhancements at the surfaces are calculated by numeric simulation. Those, locally non-uniform electric field distributions were used as input for the computational model to predict breakdown voltages. Finally, breakdown and pre-discharge measurements of sphere spark gaps with different electrode surfaces are presented and compared to the model predictions. Validations against these experiments at pressures up to 1.5 MPa show strong agreement between measured and calculated breakdown voltages. The results demonstrate that cathode surface features in the micrometer scale can significantly reduce the insulation strength of pressurized synthetic air and that the proposed model is able to predict this effect.
Tobias Köstner, Maximilian Kuhn, M. Rossner et al.· Electrical Insulation Confer...· 0 citations
Atmospheric pressure dielectric barrier discharge is generated to investigate the discharge parameters, transitioning from a filamentary to uniform appearing discharge. Uniform discharge is beneficial for modifying material surfaces owing to its intrinsic properties. For uniform discharge generation the wire-mesh electrodes of capacitive coupled reactor are linked to an alternating high voltage supply that can provide up to 42 kV at 50 Hz. The wire-mesh electrodes were shielded with glass dielectrics and Polyethylene Terephthalate sheets. Oxygen gas was supplied between the wire-mesh electrodes at a fixed flow rate of 70 ml/min controlled by a mass flow meter. The wire-mesh electrodes gap was set between 1 and 4 mm. After diagnosing the wire-mesh electrodes discharge, the results show a tendency towards uniform discharge at 27 kV under atmospheric pressure. The discharge Lissajous figure was obtained for various applied voltages to measure the fundamental parameters. The results indicate that increase in the applied voltage, enhances the capacitance of the dielectric and charge transfer process, while reducing the gap capacitance, cell capacitance and equivalent gap capacitance respectively.
Ali Akbar Khan, S. L. Yap, Wilayat Khan· Journal of Instrumentation· 0 citations
This research investigated the effect of both the applied voltage and the anode area on the electrical and plasma properties of a DC glow discharge in low-pressure argon gas. The electrical properties included current-voltage (I-V) curves and Paschen's curves, while the plasma parameters included electron temperature and number density. The plasma was generated between two copper electrodes separated by a constant distance of (4 cm), using anodes of different diameters of (2, 4, 5, and 6 cm). The plasma was characterized by optical emission spectroscopy (OES), which was used to estimate the electron temperature (Te) and number density (ne). The experimental results showed that the discharge operates within an anomalous glow regime. Furthermore, decreasing the anode area led to a higher breakdown voltage required to initiate the discharge, while increasing the anode area resulted in higher spectral emission line intensity, electron temperature, and number density. When the anode diameter changed from (2-6) cm, the electron temperature ranged from (0.389-0.393) eV, while the electron density ranged from (3.26×10¹⁵ - 9.23×10¹⁵) cm⁻³. These results confirm the influential role of anode geometry in the distribution of the electric field and the processes of ionization and excitation, and thus in determining the electrical and plasma characteristics of the discharge.
Zahraa55 Noman, Abdulhussain A. Khadayeir· Al-Noor Journal of Engineeri...· 0 citations
Understanding electric fields at electrochemical interfaces is essential for optimizing electrocatalytic processes. However, their measurement under high current densities is limited by gas evolution, which obstructs access to the electrode surface. To address this, we developed a custom flow cell featuring an internal nozzle that directs fluid across the electrode surface. This high-velocity flow suppresses bubble nucleation by limiting local hydrogen supersaturation and thereby preserves optical access to the electrode. This design enables
in situ
Raman spectroscopy and direct quantification of interfacial electric fields under current densities relevant to electrolysis. High-speed optical imaging shows that bubble coverage decreases by 85–88% at 100 mL min⁻¹ relative to stagnant conditions. With this improvement, stable Raman measurements are possible at current densities up to 25 mA cm⁻², which is more than two orders of magnitude higher than in a non-flowing cell. Under these conditions, graphene-encapsulated Pt and Au electrodes exhibit Stark shifts in the graphene G-band. These shifts allow extraction of charge-carrier densities and local interfacial fields up to 3.8 × 10⁶ V cm⁻¹. Differences between graphene/Pt and graphene/Au highlight the substrate-dependent nature of the doping behavior. We propose a framework in which metal work function, proton adsorption, and electrostatic gating collectively determine the potential-dependent graphene doping and the resulting interfacial electric field.
Daniela A. Bushiri, Anvita Bansal, E. Saunders et al.· ECS Meeting Abstracts· 0 citations
The present paper reports simulation-based investigations of electric field distributions in different geometrical configurations of the corona electrode. Previously, various corona electrode arrangements have been used in the literature for uniform corona aging of insulating samples. However, to date, no conclusive comparative study has been performed to choose the best corona electrode design that would result in a uniform electric field distribution. So, in the present study, simulation investigations have been carried out using Finite Element Methods (FEM) to explore the impact of corona discharges that affect the electric field distribution at various gap spacings between the HV and GND electrodes. An understanding of the effect of such conditions that leads to the intensification of the electric field is needed to better design the corona electrode for experimental purposes. The effect of the electric field distribution in the vicinity of the corona-treated insulating surface is developed. This study provides information on the selection of the best-suited electrode design to achieve a homogeneous electric field.
Ramanuj Deb, A. Verma· Electrical Insulation Confer...· 0 citations
Introduction
Alkaline water electrolysis (AWE) has attracted considerable attention for hydrogen production; however, the generated bubbles can cover the electrode surface at high current densities, significantly increasing the overpotential
1)
. Further research is required to understand the effects of the geometric surface structure on the bubble generation behavior and electrolysis performance. This study investigated the relationship between the Ni electrode surface structure and the hydrogen bubble generation behavior using electrochemical measurements and a microscopic video camera.
Experimental
Polycrystalline Ni rods (⌀3.0 mm) and hemispherical single-crystal Ni
2)
(⌀3.0 mm) were used as the working electrodes. The polycrystalline Ni rods had different surface roughness, achieved by polishing the bottom surfaces with papers of different grades (
G
p
= 240, 1000, 4000, and 8000). Single-crystal Ni electrodes were prepared with surface orientations of Ni(111), Ni(100), and Ni(110) using a controlled-atmosphere flame fusion method
2)
. The Ni(110) sample with the smoothest surface was used as the electrode in the experiments. The skewness of the probability density of the surface height (
S
sk
/ -) was measured using confocal laser scanning microscopy (VK-X160, Keyence Co., Ltd.).
Electrochemical measurements were performed using three-electrode electrochemical cells with 0.10, 0.50, and 1.0 M KOH solutions as electrolytes. A reversible hydrogen electrode (RHE) and Ni ring (⌀60 mm) were used as reference and counter electrodes, respectively. The current density (
i
/A cm
−2
) was normalized to the projected area of the working electrode surface. After pretreatment, linear sweep voltammetry (LSV) was conducted within a potential window (
E
) of 0.00 to −0.40 V at a scan rate of 0.10 mV s
−1
. The bubble formation behavior on the electrode surface was monitored using an inverted microscope video camera. To detect and track the time evolution of bubble generation and determine the number of bubbles generated, the bubble-generation images were analyzed using an original program
3)
. The
i
value at the onset point of bubble formation,
i
b
, was determined as the point at which the number of generated bubbles began to increase.
Results and Discussion
Fig. 1 shows the polarization curve and bubble behavior at different
i
values ((i)–(iv)) in 1.0 M KOH (
G
p
= 1000). Two linear regions were observed, with the transition point marked by an orange circle. The slope in the higher negative potential range was comparable to the Tafel slope of the Volmer–Heyrovsky reaction (120 mV dec
−1
)
2)
. The red circle in Fig. 1 indicates the onset point of bubble formation, which was situated near the transition point. Hydrogen bubbles were not observed in the lower negative potential range (i) and their generation began at
i
b
(ii). Thereafter, the number and size of bubbles increased (iii). In the higher negative potential range, the bubbles covered most of the electrode surface (iv). The potential at
i
b
is defined as
E
b
. Figure 2 shows the relationship between
E
b
and
G
p
.
E
b
increased with increasing
G
p
, indicating that a rougher electrode surface enhanced bubble nucleation.
S
sk
, which represents the deviation in height distribution from the mean plane of the surface, was introduced to clarify the factors that influenced this result. Fig. 3 illustrates the relationship between
E
b
and
S
sk
, and Fig. 4 shows images of the electrode surface for
S
sk
≈ 0 (rough) and
S
sk
< 0 (smooth). Upon polishing, large convex asperities are removed from the electrode surface, resulting in a smoother surface (
S
sk
< 0). Fig. 3 shows that
E
b
is smaller for electrodes with
S
sk
≈ 0 than for electrodes with
S
sk
< 0. Comparing the surface characteristics of electrodes with
S
sk
≈ 0 and
S
sk
< 0, those with
S
sk
≈ 0 had deeper concave features. Deeper concaves result in slower diffusion of the dissolved hydrogen produced by the electrolytic reaction, leading to a higher degree of supersaturation in the concave regions. Because a higher supersaturation enhances bubble nucleation,
E
b
is lower for electrodes with
S
sk
≈ 0.
Conclusion
The effects of the electrode surface characteristics on bubble generation during the hydrogen evolution reaction were investigated using a Ni electrode. The polarization curve exhibited two linear regions, and the potential at the onset of bubble formation (
E
b
) coincided with the point at which the linear slope changed.
E
b
increased as the convexity of the electrode surface decreased, whereas concave regions enhanced the degree of supersaturation and bubble nucleation.
References
1) D. Kitajima,
et al.
,
Electrochim. Acta
,
502
, 144772, (2024).
2) K. L. Varvaris,
et al
.,
J. Phys. Chem. C
,
127
, 14711-14722 (2023).
3) K. Toyama,
et al
.,
Electrochemistry
,
93(2)
, 027011 (2025).
Figure 1
C. Toba, R. Misumi, Gaurav Verma et al.· ECS Meeting Abstracts· 0 citations
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