Editorial

2 pages, 183 KiB

Open AccessEditorial

On the Omnipresence and Potential of Plasma Technology

by Christoph Gerhard

Appl. Sci. 2021, 11(20), 9707; https://0-doi-org.brum.beds.ac.uk/10.3390/app11209707 - 18 Oct 2021

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Even though plasma is the most common state of aggregation in the known universe, its complex chemistry and physics, as well as its specifics and particular characteristics, are not yet fully understood [...] Full article

(This article belongs to the Special Issue Plasma Science and Technology)

Research

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14 pages, 3072 KiB

Open AccessArticle

Application of Deep Learning to Spectroscopic Features of the Balmer-Alpha Line for Hydrogen Isotopic Ratio Determination in Tokamaks

by Mohammed Koubiti and Malo Kerebel

Appl. Sci. 2022, 12(19), 9891; https://0-doi-org.brum.beds.ac.uk/10.3390/app12199891 - 01 Oct 2022

Cited by 4 | Viewed by 1467

Abstract

We propose in this paper the use of artificial intelligence, especially deep learning algorithms, for the isotopic ratio determination for hydrogen–deuterium mixtures. Our approach is based on the Balmer-α line emitted by hydrogen and deuterium, but unlike the standard method, it does not [...] Read more.

We propose in this paper the use of artificial intelligence, especially deep learning algorithms, for the isotopic ratio determination for hydrogen–deuterium mixtures. Our approach is based on the Balmer-α line emitted by hydrogen and deuterium, but unlike the standard method, it does not consist of fitting the Hα/Dα line spectra. Instead, only some basic spectroscopic features such as the line peak-to-dip wavelength separation, peak-to-peak and dip-to-peak intensity ratios of the Zeeman–Doppler-broadened Hα/Dα line spectra are used by the regression algorithm for training. We demonstrate the proof-of-principle of our approach by applying deep learning from the open-access machine-learning platform TensorFlow to Hα/Dα line profiles, which we have synthetized with pre-determined parameters such as neutral temperatures, the magnetic field strength and the H/(H+D) isotopic ratio. The used regression algorithm allowed us to retrieve with a good accuracy the isotopic ratios used for the synthetized line profiles. Full article

(This article belongs to the Special Issue Plasma Science and Technology)

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12 pages, 5101 KiB

Open AccessArticle

High Density RF-DC Plasma Nitriding under Optimized Conditions by Plasma-Diagnosis

by Tatsuhiko Aizawa, Imron Rsadi and Ersyzario Edo Yunata

Appl. Sci. 2022, 12(8), 3706; https://0-doi-org.brum.beds.ac.uk/10.3390/app12083706 - 07 Apr 2022

Cited by 7 | Viewed by 1622

Abstract

This paper is concerned with plasma diagnosis on a N₂-H₂ gas mixture to determine the optimum parameters for the nitriding process. Plasma parameters such as pressure, RF-voltage, and DC-bias were varied for optimization. The active species such as [...] Read more.

This paper is concerned with plasma diagnosis on a N₂-H₂ gas mixture to determine the optimum parameters for the nitriding process. Plasma parameters such as pressure, RF-voltage, and DC-bias were varied for optimization. The active species such as

N_{2}^{+}

and NH were identified in plasma diagnosis. In the N₂-H₂ gas mixture, hydrogen imposed a great influence on plasma generation. The small addition of a hydrogen molecule into the gas mixture resulted in the highest yield of

N_{2}^{+}

ions and NH radicals; the optimum hydrogen content was 20% in the mixture. The austenitic stainless-steel type AISI304 was nitrided at 673 K and 623 K to experimentally demonstrate that hydrogen gas content optimization is necessary to improve the surface hardness and to describe low temperature nitriding under high nitrogen flux at the surface. Full article

(This article belongs to the Special Issue Plasma Science and Technology)

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15 pages, 2117 KiB

Open AccessArticle

Characterization and Optimization of a Conical Corona Reactor for Seed Treatment of Rapeseed

by Thalita M. C. Nishime, Jasmin Werner, Nicola Wannicke, Taiana S. M. Mui, Konstantin G. Kostov, Klaus-Dieter Weltmann and Henrike Brust

Appl. Sci. 2022, 12(7), 3292; https://0-doi-org.brum.beds.ac.uk/10.3390/app12073292 - 24 Mar 2022

Cited by 5 | Viewed by 1731

Abstract

Plasma agriculture is a growing field that combines interdisciplinary areas with the aim of researching alternative solutions for increasing food production. In this field, plasma sources are used for the treatment of different agricultural goods in pre- and post-harvest. With the big variety [...] Read more.

Plasma agriculture is a growing field that combines interdisciplinary areas with the aim of researching alternative solutions for increasing food production. In this field, plasma sources are used for the treatment of different agricultural goods in pre- and post-harvest. With the big variety of possible treatment targets, studied reactors must be carefully investigated and characterized for specific goals. Therefore, in the present study, a cone-shaped corona reactor working with argon was adapted for the treatment of small seeds, and its basic properties were investigated. The treatment of rapeseed using different voltage duty cycles led to an increase in surface wettability, possibly contributing to the accelerated germination (27% for 90% duty cycle). The discharge produced by the conical reactor was able to provide an environment abundant with reactive oxygen species that makes the process suitable for seeds treatment. However, operating in direct treatment configuration, large numbers of seeds placed in the reactor start impairing the discharge homogeneity. Full article

(This article belongs to the Special Issue Plasma Science and Technology)

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11 pages, 24578 KiB

Open AccessFeature PaperArticle

Influence of Air Cold Plasma Modification on the Surface Properties of Paper Used for Packaging Production

by Konrad Terpiłowski, Michał Chodkowski, Salvador Peréz-Huertas and Łukasz Wiechetek

Appl. Sci. 2022, 12(7), 3242; https://0-doi-org.brum.beds.ac.uk/10.3390/app12073242 - 22 Mar 2022

Cited by 3 | Viewed by 1786

Abstract

In this study, the effect of air plasma on the surface properties of printed and coated cardboard was investigated. The material was activated by low-pressure cold plasma for 1, 10, 20, and 30 s. Wettability changes on the surface were examined by contact [...] Read more.

In this study, the effect of air plasma on the surface properties of printed and coated cardboard was investigated. The material was activated by low-pressure cold plasma for 1, 10, 20, and 30 s. Wettability changes on the surface were examined by contact angle measurements using the sessile droplet technique. The differences in the surface free energy were calculated using the Lifshitz–van der Waals/acid–base and Contact Angle Hysteresis approaches. Optical profilometry was used for the surface roughness evaluation and an X-ray photoelectron spectroscopy analysis was performed to find changes in surface chemistry. Adhesive strength tests were carried out to estimate the adhesion changes after the material’s modification. It was found that the water and formamide contact angles increased after the plasma treatment while the diiodomethane contact angle did not change. As a result of the modification, the surface free energy also increased significantly and the surface roughness increased. The pull-off tests confirmed the improvement in the material’s surface properties. Moreover, it was demonstrated that the optimal effect can be obtained after just 10 s of the plasma process. Full article

(This article belongs to the Special Issue Plasma Science and Technology)

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16 pages, 2108 KiB

Open AccessArticle

A New Technique of Eliminating the Actual Plasma Background When Calibrating Emission Spectrometers with a CCD Recording System

by Aleksandr S. Mustafaev, Anna N. Popova and Vladimir S. Sukhomlinov

Appl. Sci. 2022, 12(6), 2896; https://0-doi-org.brum.beds.ac.uk/10.3390/app12062896 - 11 Mar 2022

Cited by 3 | Viewed by 1698

Abstract

This research focuses on the development of a new technique of emission spectral analysis designed to accurately account for the background radiation. The technique enables the evaluation of background radiation while being unaffected by its spectral shape. This is possible through the use [...] Read more.

This research focuses on the development of a new technique of emission spectral analysis designed to accurately account for the background radiation. The technique enables the evaluation of background radiation while being unaffected by its spectral shape. This is possible through the use of standard data obtained in an analytical-line-recording process performed by light-intensity-to-electric-signal converters such as CCDs, PMTs, photodiodes, etc. This technique, when applied at a set RMS deviation of the analytical-line-radiation intensity, reduces the random error of a determined low impure-element concentration due to the optimal calibration-line slope. In areas of high concentrations, an accurate accounting of the background does little to affect the emission spectrometer’s measurement accuracy. This technique also allows the replication of calibration curves in spectrometers of the same type by a linear-intensity conversion with only two standard samples required. The technique was tested on SPAS-02 and SPAS-05 commercial spark spectrometers. The testing fully confirmed the aforementioned advantages of the developed technique. The authors also determined the applicability conditions of the conventional emission-spectrometer-recalibration method by a linear conversion of the analytical-line intensity. Full article

(This article belongs to the Special Issue Plasma Science and Technology)

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11 pages, 725 KiB

Open AccessArticle

Atmospheric Pressure Dielectric Barrier Discharge Plasma-Enhanced Optical Contact Bonding of Coated Glass Surfaces

by Josephine Neumann, Stephan Brückner, Wolfgang Viöl and Christoph Gerhard

Appl. Sci. 2021, 11(15), 6755; https://0-doi-org.brum.beds.ac.uk/10.3390/app11156755 - 22 Jul 2021

Cited by 1 | Viewed by 1871

Abstract

This paper reports on plasma-enhanced bonding of optics surfaces coated with highly sensitive functional layers using surface preparation by a dielectric barrier discharge (DBD) plasma. The samples to be bonded were treated with a DBD in diffuse mode at atmospheric pressure for 30 [...] Read more.

This paper reports on plasma-enhanced bonding of optics surfaces coated with highly sensitive functional layers using surface preparation by a dielectric barrier discharge (DBD) plasma. The samples to be bonded were treated with a DBD in diffuse mode at atmospheric pressure for 30 s which is applied directly to the sample surface, then joined with the aid of de-ionised water and cured subsequently. The plasma treatment itself already increased the shear strength achieved by a factor of two compared to classical wringing or direct contacting, while the curing process led to a further increase by a factor of up to five, depending on curing temperature. The observed enhancement of shear strength can be attributed to DBD plasma-induced cleaning and most likely additional activation of the surface as verified by contact angle measurements. Since the impact of the used plasma on the surface is quite gentle in comparison to other bonding processes or other plasma-based processes reported in the literature, a destruction of the treated functional layer is avoided. This advantage makes it possible to bond even optics surfaces coated with sensitive materials. Full article

(This article belongs to the Special Issue Plasma Science and Technology)

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12 pages, 3147 KiB

Open AccessArticle

Characterizations of a Plasma-Water System Generated by Repetitive Microsecond Pulsed Discharge with Air, Nitrogen, Oxygen, and Argon Gases Species

by Nima Bolouki, Wen-Hui Kuan, Yu-Yun Huang and Jang-Hsing Hsieh

Appl. Sci. 2021, 11(13), 6158; https://0-doi-org.brum.beds.ac.uk/10.3390/app11136158 - 02 Jul 2021

Cited by 39 | Viewed by 3526

Abstract

A non-thermal plasma-water system using a microsecond pulsed high-voltage power supply was investigated with air, nitrogen, oxygen, and argon gas feedings individually. Optical emission spectroscopy (OES) was utilized to characterize the primary active species inside the plasmas generated by different gas feedings. The [...] Read more.

A non-thermal plasma-water system using a microsecond pulsed high-voltage power supply was investigated with air, nitrogen, oxygen, and argon gas feedings individually. Optical emission spectroscopy (OES) was utilized to characterize the primary active species inside the plasmas generated by different gas feedings. The OES method was also employed to estimate the neutral gas and electron temperatures. The pH and the oxidation-reduction potential (ORP) of plasma-activated water (PAW) were measured in the liquid phase. An ion chromatography system (ICS) was employed to present the PAW activity, such as nitrite and nitrate species. Moreover, hydrogen peroxide as a secondary active species inside the activated water, generated by the gases mentioned above, was measured by potassium permanganate titration. It was found that the gas species have a noticeable effect on the pH level as well as the ORP of PAW. In the cases of argon and oxygen plasmas, the pH level of PAW does not change significantly. In contrast, the pH values of PAW generated by air and nitrogen plasmas decline sharply during the treatment time. Moreover, the gas species have a significant impact on the concentrations of nitrite, nitrate, and hydrogen peroxide generated in PAW. The activated water generated by oxygen plasma provides the highest level of hydrogen peroxide. Although the consumed power of argon plasmas was half of the other plasma sources, it provides relatively high hydrogen peroxide contents compared to the nitrogen and air plasmas. Full article

(This article belongs to the Special Issue Plasma Science and Technology)

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20 pages, 6876 KiB

Open AccessArticle

A Linear Microwave Plasma Source Using a Circular Waveguide Filled with a Relatively High-Permittivity Dielectric: Comparison with a Conventional Quasi-Coaxial Line Waveguide

by Ju-Hong Cha, Sang-Woo Kim and Ho-Jun Lee

Appl. Sci. 2021, 11(12), 5358; https://0-doi-org.brum.beds.ac.uk/10.3390/app11125358 - 09 Jun 2021

Cited by 4 | Viewed by 3229

Abstract

For a conventional linear microwave plasma source (LMPS) with a quasi-coaxial line transverse electromagnetic (TEM) waveguide, a linearly extended plasma is sustained by the surface wave outside the tube. Due to the characteristics of the quasi-coaxial line MPS, it is easy to generate [...] Read more.

For a conventional linear microwave plasma source (LMPS) with a quasi-coaxial line transverse electromagnetic (TEM) waveguide, a linearly extended plasma is sustained by the surface wave outside the tube. Due to the characteristics of the quasi-coaxial line MPS, it is easy to generate a uniform plasma with radially omnidirectional surfaces, but it is difficult to maximize the electron density in a curved selected region. For the purpose of concentrating the plasma density in the deposition area, a novel LMPS which is suitable for curved structure deposition has been developed and compared with the conventional LMPS. As the shape of a circular waveguide, it is filled with relatively high-permittivity dielectric instead of a quasi-coaxial line waveguide. Microwave power at 2.45 GHz is transferred to the plasma through the continuous cylindrical-slotted line antenna, and the radiated electric field in the radial direction is made almost parallel to the tangential plane of the window surface. This research includes the advanced 3D numerical analysis and compares the results with the experiment. It shows that the electron density in the deposition area is higher than that of the conventional quasi-coaxial line plasma MPS. Full article

(This article belongs to the Special Issue Plasma Science and Technology)

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