Plasma Equipment Research Articles

Design and construction of a continuous industrial scale cold plasma equipment for fresh produce industry

This study presents the design, construction, and evaluation of a novel continuous industrial-scale cold plasma system optimized for the treatment of fresh produce. The system integrates multiple plasma modules with a multipin-to-plate discharge configuration, ensuring efficient generation of reactive oxygen and nitrogen species at relatively low voltages. The cold plasma modules are combined with a conveyor mechanism, allowing for continuous, uniform exposure of irregularly shaped food items, such as tomatoes, to reactive plasma species. Notably, the system operates using ambient air, and incorporates modularity for easy scalability, making it suitable for both small-scale enterprises and large-scale industrial applications.Experimental trials on tomatoes demonstrated reductions in microbial load, with the system effectively enhancing product safety while minimizing power consumption. Moreover, the integration of cold storage further extended shelf life, although optimization of plasma treatment parameters remains necessary to preserve bioactive compounds like lycopene and ascorbic acid. This research fills a critical gap in scaling cold plasma technology for industrial use, providing a sustainable and energy-efficient solution for food disinfection. The results highlight the potential of this system to meet industry demands for safe and efficient on-farm and small-scale enterprise disinfection.

Numerical investigation of plasma properties in Ar/SiH4 inductively coupled plasmas considering electron energy distribution functions

In thin film deposition, Ar/SiH4 mixtures are widely used to make polysilicon (poly-Si) and hydrogenated amorphous silicon (a-SiH) layers. Despite extensive research conducted on this mixture, little research has focused on the variations in plasma properties, radicals, and ions that occur during plasma discharge in inductively coupled plasma (ICP) equipment compared to capacitive coupled plasma equipment. In this paper, we investigate the properties of the plasma generated through mathematical modeling of Ar/SiH4 inductive coupled plasma discharge by using the electron energy distribution function (EEDF) obtained by solving the Boltzmann equation. We closely examine the variation in plasma properties and the correlation of plasma variables by controlling the radio frequency power and gas pressure during the process conditions. The Boltzmann equation was computed by assuming the two-term approximation, resulting in a Druyvesteyn-like EEDF due to the high-pressure conditions. To validate the simulation model, the 2D simulation results were compared with probe measurements performed in a two-turn ICP chamber. The results demonstrated encouraging agreement with the measured data. This research not only enhances our comprehension of the discharge characteristics but also establishes a framework for optimizing the discharge conditions to enhance the process and effectively regulate external variables.

Simulation-based Analysis of the Atmospheric Pressure Plasma and Its Temperature Distribution Using Ansys Mechanical

This research article delves into an in-depth analysis of atmospheric pressure plasma and its temperature distribution, utilizing the finite element method (FEM) and Ansys Mechanical software. This contribution discusses the various technological applications of atmospheric pressure plasma, including surface treatment, material processing, and plasma equipment, where precise plasma and temperature behavior prediction is crucial for an optimization and innovative solutions. The simulations presented provide a detailed representation of plasma and temperature behavior, and the simulation models have been validated against experimental data, demonstrating the accuracy and reliability of the approaches used. The deviation between the simulation and the actual measurement results was a maximum of 0.87%. In addition, the implications of the findings of this research for optimizing plasma applications and future research directions are discussed. This study highlights the crucial role of simulation tools, such as Ansys Mechanical, for investigating and optimizing atmospheric pressure plasma applications.

Ion motion above a biased wafer in a plasma etching reactor

The behavior of ions in the plasma is an essential component in the process of industrial etching. We studied the motions and energy distribution of argon ions in a inductively coupled plasma (ICP) etching tool, by the method of laser induced fluorescence (LIF). The silicon wafer clamped to a chuck at the bottom of the chamber was biased with a 1 MHz 1–1.2 kV peak-to-peak sinusoidal voltage. The plasma is formed with a 2 MHz ICP coil pulsed at 10 Hz. Sheath thickness was measured at different phases of the bias waveform. The experiment also compared the ion motions with and without wafer bias, as well as different switch-on time of wafer bias. For all cases, ion energy distribution functions and the two-dimensional flow pattern were studied near the center and edge of the wafer. Significant vortex flows were observed near the wafer edge. Experiments in which the wafer was biased in the plasma afterglow resulted in a narrow distribution of ion energy close to the bias voltage at the vicinity of the wafer, and the ion incident angle on the wafer was the smallest. The results were compared to simulations using the Hybrid Plasma Equipment Model code.

Influence of the shape of the anode assembly inner channel on plasma flow velocity

This article considers how the shape of the inner channel in the anode assembly affects plasma flow velocity in a plasma torch. Three different shapes of the anode assembly were analyzed, all with a conical confusor part of 50 mm in length: with a diameter transition from 12 to 6 mm, from 12 to 8 mm, and from 12 to 10 mm. A computer experiment was performed using the finite element method and then validated by the subsequent full-scale experiment on a laboratory plasma unit. The obtained results were verified. The verification outcomes showed a satisfactory convergence and were consistent with the published data. A review of the existing plasma unit designs for powder production, application of functional coatings, and surface modification was carried out. The software packages implementing the finite element method to solve these problems were examined. The study yielded practical recommendations for consumers and developers of plasma equipment and identified the shapes of the anode assembly enabling both supersonic and subsonic plasma flow regimes.

Cost-effective layered double hydroxides/conductive polymer nanocomposites for electrochemical detection of wastewater pollutants

There is an urgent need to develop multifunctional cost-effective nanomaterials and nanocomposites that can be used in numerous applications while showing high efficiency and cheaper implementation compared to conventional techniques and/or materials. In this work, zinc/iron layered double hydroxide (LDH) and polyaniline (PANI) were synthesized as a model LDH/conductive polymer nanocomposite, which is a promising family of cheap multifunctional materials. This electrochemical properties of this nanocomposite was investigated for detection of heavy metal (HM) ions in water streams, using lead as a model HM. In the present work, zinc/iron LDH and PANI was assigned as carbon paste electrode modifier. The composite was fully characterized using various characterization techniques including X-ray diffraction (XRD), scanning electron microscope (SEM), and Fourier transform InfraRed (FTIR). The electrochemical redox reactions of lead (II) ions at the modified electrode interface were investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), Accordingly, a linear relation of Pb2+ ions was achieved in the concentration range 1–80 µM with limit of detection (LOD) was 167.8 nM and limit of quantification (LOQ) was 559.4 nM. Furthermore, the cost of using such material for lead removal using a typical adsorption study was compared to using conventional inductively coupled plasma (ICP) or atomic absorption spectrometry (AAS) equipment for tracking HM removal during the adsorption process. Cost analysis revealed that the final overall cost of the modified carbon paste electrode is estimated as 1.25 USD. This cost represents less than 0.1% of the total cost required to conduct the same adsorption study using a typical ICP or AAS equipment. This composite can pave the road towards portable measurements for onsite detection of wastewater pollutants using cheap disposable-electrodes as compared to massive expensive off site equipment such as ICP and AAS.

Low-pressure inductively coupled plasmas in hydrogen: impact of gas heating on the spatial distribution of atomic hydrogen and vibrationally excited states

Non-equilibrium inductively coupled plasmas (ICPs) operating in hydrogen are of significant interest for applications including large-area materials processing. Increasing control of spatial gas heating, which drives the formation of neutral species density gradients and the rate of gas-temperature-dependent reactions, is critical. In this study, we use 2D fluid-kinetic simulations with the Hybrid Plasma Equipment Model to investigate the spatially resolved production of atomic hydrogen in a low-pressure planar ICP operating in pure hydrogen (10–20 Pa or 0.075–0.15 Torr, 300 W). The reaction set incorporates self-consistent calculation of the spatially resolved gas temperature and 14 vibrationally excited states. We find that the formation of neutral-gas density gradients, which result from spatially non-uniform electrical power deposition at constant pressure, can drive significant variations in the vibrational distribution function and density of atomic hydrogen when gas heating is spatially resolved. This highlights the significance of spatial gas heating on the production of reactive species in relatively high-power-density plasma processing sources.

The Knife-Plane Configuration Model of CCP equipment from plasma corona discharge case

This research discusses the concept of analytical calculations of current-voltage (I-V) characteristics in the case of corona discharges using an asymmetric electrode model (with a DC source), which is often called capacitively coupled plasma (CCP) equipment. This CCP equipment, which is almost similar in shape to capacitor equipment in conventional electrical equipment, has the characteristic of having an active electrode in an upright position above the position of a passive electrode (in a lying position) in the air. Another characteristic is that the lowest end of the active electrode has a sharp surface so that a large corona current flows out of the sharp surface towards the passive electrode. The (I-V) characteristic calculation method can be calculated using a geometric concept (based on the sharp surface at the tip of the active electrode) using a modified capacitance concept. For the case of an asymmetric model with an arrangement of active and passive electrodes perpendicular to each other, the capacitance calculation can use the knife-plane electrode configuration model.

A novel on-line microwave diagnostic for an atmospheric pressure air plasma based on an artificial neural network

Permittivity is an important aspect of the design of microwave devices. In order to design microwave devices that are more suitable for the excitation of air plasmas, this paper presents a method for the on-line measurement of the relative permittivity of an atmospheric pressure air plasma with 2.45 GHz microwaves. First, a ridged waveguide is designed and constructed to excite the air. Using the ridged waveguide, the plasma can be excited and measured simultaneously. An artificial neural network trained with simulated data is integrated into the system to invert the dielectric constant of the air plasma being measured. At a power of 786 W and an airflow rate of 1250 L/h, the real and imaginary parts of the permittivity are obtained to be −1244 and 60, respectively. The forecasted errors on the real part and the imaginary part of the relative permittivity are kept at around 5% and 3%. The Drude model is used to construct a relationship between the electronic and dielectric properties. This diagnostic method is simple to operate and has a high degree of generality. It should be useful in the design of microwave plasma devices and can greatly improve the efficiency of microwave plasma equipment.

Spatiotemporal corona discharge characteristics of nanoelectrode: array carbon nanotubes

Corona discharge is a widely-used phenomenon that requires a sharp electrode to generate a strong electric field (106 V m−1) at high voltages (typically in the tens of kV). The advent of nanoelectrodes has overcome the technical limitations of traditional electrodes, dramatically improving the density of discharge points and enabling low voltage (several kV) corona discharges with nanometer-sized tips. Consequently, nanoelectrode discharge technology has the potential to revolutionize the miniaturization of plasma equipment in the future. However, research on the discharge characteristics of nanoelectrodes is still relatively sparse. This paper focuses on an array of carbon nanotubes (ACNTs) and proposes a numerical simulation model based on the hybrid hydrodynamics model and ion migration model. The accuracy and efficiency of this model are demonstrated by a high degree of agreement between the results from numerical simulations and experiments. In addition, the corona discharge characteristics of ACNTs are studied and discussed, particularly the spatiotemporal evolution of charged particles near the tip. This paper may provide a method of analysis for optimizing and broadly applying nanoelectrodes.

Computational approach for plasma process optimization combined with deep learning model

As semiconductor device structures become more complex and sophisticated, the formation of finer and deeper patterns is required. To achieve a higher yield for mass production as the number of process steps increases and process variables become more diverse, process optimization requires extensive engineering effort to meet the target process requirements, such as uniformity. In this study, we propose an efficient process design framework that can efficiently search for optimal process conditions by combining deep learning (DL) with plasma simulations. To establish the DL model, a dataset was created using a two-dimensional (2D) hybrid plasma equipment model code for an argon inductively coupled plasma system under a given process window. The DL model was implemented and trained using the dataset to learn the functional relationship between the process conditions and their consequential plasma states, which was characterized by 2D field data. The performance of the DL model was confirmed by comparison of the output with the ground truth, validating its high consistency. Moreover, the DL results provide a reasonable interpretation of the fundamental features of plasmas and show a good correlation with the experimental observations in terms of the measured etch rate characteristics. Using the designed DL, an extensive exploration of process variables was conducted to find the optimal processing condition using the multi-objective particle swarm optimization algorithm for the given objective functions of high etch rate and its uniform distribution. The obtained optimal candidates were evaluated and compared to other process conditions experimentally, demonstrating a fairly enhanced etch rate and uniformity at the same time. The proposed computational framework substantially reduced trial-and-error repetitions in tailoring process conditions from a practical perspective. Moreover, it will serve as an effective tool to narrow the processing window, particularly in the early stages of development for advanced equipment and processes.

Research and improvement of SPS spark plasma sintering equipment

Through the functional disassembly study of the pressurization system, vacuum and atmosphere control system, water cooling system and control system of the SPS spark plasma equipment, the problems in the actual production process and the corresponding improvements of the spark plasma sintering (SPS) equipment are also discussed. The shortcomings and its development directions are also proposed to provide sufficient data support for the subsequent research.

Investigation of Upgraded Technology for Plasma Spraying of Bronze Powder Using the Combined Process with Hydrocarbon Additions

The object of the research is thermal spray process for the formation of metal coating from bronze powder in plasma-fuel variant, using direct current (DC) electric arc plasma torch, on steel samples. The aim of the work was to investigate and develop the technology for plasma-fuel spraying of functional coatings (for wear-resistant and antimicrobial applications) on machine-building and medical purpose pieces with increased process capacity and moderate energy consumptions in a comparison with conventional thermal spray technologies with use of inert and oxygen-free gas media. During the study, using experimental and thermodynamic estimation methods, the thermal and chemical parameters of the process under the spraying conditions at ambient pressure were characterized, which made it possible to determine the area of preferred regimes of the developed technology. On the modernized testing unit for plasma spraying of metal powders with power of up to 40 kW, operating using a controlled combination of three types of gases – technical nitrogen and propane-butane (LPG) with compressed air, the measurement and optimization of the operating and constructive/assembling parameters of the system for aluminum bronze coating spraying were established. In this case, the experiments were carried out using the designed fuel intensifier, which is joined with the PP-25 arc plasma torch, as well as additional technological equipment (protective shroud). For samples of the resulting coatings with a thickness of 100 to 450 mm from the bronze material, testing of phase composition and some parameters of the resulting coatings on steel products was carried out. Operating capacity of the proposed process reaches 7–15 kg/h for bronze powder when using a moderate power of the torch – up to 35–40 kW and a limited flow rate of hydrocarbon gas (for example, LPG of the SPBT grade) – 0.1–0.35 kg/h. Analysis of the energy efficiency parameters of the developed technology, as well as its calculated technical characteristics, in a comparison with plasma and combined equipment of a similar purpose, showed that it has an advantage in terms of target indicators, in particular, in terms of energy consumption and total energy efficiency of the spraying unit, not less than 20–30 %. This makes it to proceed later to the stage of application of this technology into production based on a new process for the metal coating formation, in particular with antimicrobial properties, with improved energy efficiency of the process.

Contact fatigue properties of NiCrCr3C2 and AlSi coatings for sealing performance of the Wankel engine

NiCrCr3C2 and AlSi coatings were prepared using supersonic plasma equipment. The contact fatigue properties of the coatings were evaluated under dry friction, fuel oil, and lubricating oil conditions. The fatigue life of the NiCrCr3C2 coating was much longer than that of the AlSi coating at the same pressure. Under the same conditions, the NiCrCr3C2 coating had better contact fatigue performance than the AlSi coating, and due to the wettability of Cr3C2 and NiCr alloys, the Cr3C2 hard phase was firmly embedded in the NiCr alloy to ensure hardness and wear resistance at high temperatures.

Numerical Simulation of an ICP Plasma Torch and an HF Generator Taking into Account Their Mutual Influence

In developing electrotechnical plasma equipment, one of the most important issues is the coupling of a power source and a nonlinear load (in this case, a ICP plasma torch). The following factors affect the power supply operation: the method of gas supply to the plasma torch, operation mode, gas consumption and composition. The power supply can influence the plasma flow pattern in the plasma torch through the volt-ampere characteristics. The article addresses matters concerned with studying the processes in the ICP plasma torch electrical technology installation and revealing regularities influencing the plasma flow generation. An ICP plasma torch and its power supply are numerically simulated with taking their mutual influence into account. A 2D axisymmetric model of the operation of a plasma torch that uses argon as a plasma-forming gas is considered. The gas flow is described by the turbulent k-ε model. A power supply equivalent circuit is proposed for its implementation in the Comsol Multiphysics software package. The possibility of coupling a power source and a plasma torch in one model is shown. The distributions of velocity, temperature, and electrical parameters over time are obtained. By using the proposed approach, it is possible to analyze the sensitivity of the electrotechnological processes in the ICP plasma torch to the power source electrical parameters. This article is the first one in a series of studies on simulating the "power supply-plasma torch" system.

Control Algorithms and Technical Solutions in the Traction Electrical Drive of Mining Dump Trucks

In developing electrotechnical plasma equipment, one of the most important issues is the coupling of DC or AC electrical drive is the basic type of drive in mining dump trucks with a load capacity of 90 t or more. Reliable and economically efficient operation of traction electrical drives is one of key conditions for successful operation of mining dump trucks. The developers of converters rarely reveal details of their design, and the electric motors are controlled using the information from speed sensors. The article considers in detail new design solutions and control without using sensors on the shaft of traction electric motors of BELAZ dump trucks. Owing to a rational design of the cabinet of converters and control systems for a dump truck of a load-carrying capacity of 136 t, it became possible to minimize parasitic parameters and achieve a noticeable decrease in the net cost and improvement of reliability, serviceability and manufacturability. Trial runs of the BELAZ dump truck with a load-carrying capacity of 90 t with sensorless control have confirmed high quality of operation in all modes, including the truck maneuvering at low speeds, holding on a hill, and driving on an ice-covered road. The introduction of the obtained results in the traction electrical equipment sets of dump trucks with load-carrying capacity of 90 240 t will make it possible to decrease their net cost and increase their reliability without degrading the control quality.

Generative Adversarial Network-Based Fault Detection in Semiconductor Equipment with Class-Imbalanced Data.

This research proposes an application of generative adversarial networks (GANs) to solve the class imbalance problem in the fault detection and classification study of a plasma etching process. Small changes in the equipment part condition of the plasma equipment may cause an equipment fault, resulting in a process anomaly. Thus, fault detection in the semiconductor process is essential for success in advanced process control. Two datasets that assume faults of the mass flow controller (MFC) in equipment components were acquired using optical emission spectroscopy (OES) in the plasma etching process of a silicon trench: The abnormal process changed by the MFC is assumed to be faults, and the minority class of Case 1 is the normal class, and that of Case 2 is the abnormal class. In each case, additional minority class data were generated using GANs to compensate for the degradation of model training due to class-imbalanced data. Comparisons of five existing fault detection algorithms with the augmented datasets showed improved modeling performances. Generating a dataset for the minority group using GANs is beneficial for class imbalance problems of OES datasets in fault detection for the semiconductor plasma equipment.

The Effect of Dielectric Barrier Discharge Plasma Gas and Plasma-Activated Water on the Physicochemical Changes in Button Mushrooms (Agaricus bisporus).

Button mushrooms (Agaricus bisporus) are highly popular worldwide due to their rich nutritional value and health benefits. However, the rapid water loss rate and browning restrict their economic value. The atmospheric cold plasma (ACP) generated by the plasma equipment used by dielectric barrier discharge preservation technology is widely used for food preservation since it is cost-efficient and environmentally friendly, generating no chemical residues. This study established four treatment groups, namely the direct ACP treatment group (DBD), plasma-activated water immersion group (PAW), pure water immersion group (PW), and control group (control), to explore the effect that ACP preservation technology has on button mushrooms. The results indicated that ACP treatment decreased the pH of pure water from 5.90 ± 0.03 to 5.16 ± 0.03, while significantly increasing the temperature (p < 0.05). During the storage period, the browning index (BI) and E value were the lowest in the PAW group, which exhibited the best hardness and sensory properties. Neither the pH nor water activity changed significantly during the storage period in any of the groups. The polyphenol oxidase (PPO) activity in the button mushroom decreased significantly compared with the control after plasma-activated water treatment. In summary, plasma-activated water significantly reduced the BI and E value of button mushrooms, inhibited PPO activity, and yielded the most stable sensory properties for the optimal preservation of button mushrooms.

Changes in Content of Bioactive Compounds and Antioxidant Activity Induced in Needles of Different Half-Sib Families of Norway Spruce (Picea abies (L.) H. Karst) by Seed Treatment with Cold Plasma.

In order to ensure sufficient food resources for a constantly growing human population, new technologies (e.g., cold plasma technologies) are being developed for increasing the germination and seedling growth without negative effects on the environment. Pinaceae species are considered a natural source of antioxidant compounds and are valued for their pharmaceutical and nutraceutical properties. In this study, the seeds of seven different Norway spruce half-sib families were processed for one or two minutes with cold plasma (CP) using dielectric barrier discharge (DBD) plasma equipment. At the end of the second vegetation season, the total flavonoid content (TFC), DPPH (2,2- diphenyl-1-picryl-hydrazyl-hydrate), and ABTS (2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)) antioxidant activity, and the amounts of six organic acids (folic, malic, citric, oxalic, succinic, and ascorbic) were determined in the needles of different half-sib families of Norway spruce seedlings. The results show that the TFC, antioxidant activity, and amounts of organic acids in the seedling needles depended on both the treatment duration and the genetic family. The strongest positive effect on the TFC was determined in the seedlings of the 477, 599, and 541 half-sib families after seed treatment with CP for 1 min (CP1). The TFC in these families increased from 118.06 mg g−1 to 312.6 mg g−1 compared to the control. Moreover, seed treatment with CP1 resulted in the strongest increase in the antioxidant activity of the needles of the 541 half-sib family seedlings; the antioxidant activity, determined by DPPH and ABTS tests, increased by 30 and 23%, respectively, compared to the control. The obtained results indicate that the CP effect on the amount of organic acids in the needles was dependent on the half-sib family. It was determined that treatment with CP1 increased the amount of five organic acids in the needles of the 541 half-sib family seedlings. The presented results show future possibilities for using cold plasma seed treatment in the food and pharmacy industries.

A Successful Elimination of Indonesian SARS-CoV-2 Variants and Airborne Transmission Prevention by Cold Plasma in Fighting COVID-19 Pandemic: A Preliminary Study

Global infection and mortality rates have soared to millions due to SARS-CoV-2 human-to-human transmission from via droplets which then declared as pandemic. This study examined the created cold plasma equipment (CPE) effectiveness in reducing COVID-19 transmission in a confined space. CPE sucked air using a fan in a test chamber then pushed it into a cold plasma reactor. The results indicated that it was able to terminate all SARS-CoV-2 variants along with bacteria and fungi indoors by keeping it turned on for 30 minutes’ minimum. CPE was proven as safe and effective to hinder virus transmission with the acceptable ozone emission as the side effect.