Plasma Jet Reactor Research Articles

TO HIGHLY PRODUCTIVE SYNTHESIS OF ALUMINUM NANOPARTICLES IN PLASMA FLOW AT ATMOSPHERIC PRESSURE

Purpose. To study the highly productive evaporation of aluminum micron powder in an atmospheric pressure plasma jet for the synthesis of nanoaluminum. Using special plasma technology, nanoparticles can be produced by rapid melting and evaporation of the initial micrometer particles and their subsequent re-nucleation. Research methods. Methods of mathematical and computer modeling of subsonic plasma turbulent jets at atmospheric pressure and experimental studies of two-phase processes during thermal plasma treatment using an arc plasma torch. Results. Based on computer modeling, a special reactor system was designed and developed, which includes a plasma-jet reactor with an electric arc plasma torch for the synthesis of aluminum nanoparticles. Numerical modeling makes it possible to determine the position of the melting point, evaporation and crushing of a molten particle, the evolution of the fractional composition of the dispersed phase, and find the speed and temperature of the particle in the area from its melting point to the crushing point. An experimental test of the operation of the reactor system was carried out using arc plasma torches with a power of 30 and 150 kW. It has been shown that intensifying the fragmentation of dispersed raw materials in a plasma jet can be useful in technologies for producing nanomaterials. The consequence of the fragmentation process is the redistribution of the fractional composition of the powder along the plasma jet and the accompanying changes in the dynamics of movement, heating and evaporation of particles. It has been determined that when the temperature of the largest aluminum particles reaches 2500 C, the total amount of evaporated mass is theoretically equal to 100%. The main parameters influencing the behavior of particles in a plasma jet are particle diameter, powder injection rate, flow rate, temperature and composition of the plasma gas. Taking these parameters into account will allow the process to operate at increased productivity. Scientific novelty. A mathematical description of the process of fragmentation a polydisperse powder, based on a continuum approach, has been obtained, which makes it possible to determine the position of the crushing point of a molten particle, the fractional composition of the dispersed phase, and find the speed and temperature of the particle in the area from its melting point to the point of crushing and evaporation. It was shown for the first time that it is possible to carry out a process in which complete evaporation of a molten drop is achieved due to the high enthalpy of the plasma before the end of mixing with steam. Practical value. A special reactor system has been designed and developed, which includes a plasma-jet reactor with an electric arc plasmatron for the synthesis of aluminum nanoparticles. The operating parameters of the reactor system have been determined, which will allow the synthesis of aluminum nanoparticles to be carried out with high productivity.

The influence of electrodes thicknesses on the characteristics of a helium plasma jet

An atmospheric plasma jet reactor (PJR) was designed using two outer disc-like copper plats placed around a quartz tube. The effects of the electrodes’ thicknesses and their placement on the plasma jet length created in helium and its electrical characteristics were investigated. Measurements of the plasma jet length were carried out for different applied voltages and different gas flow rates. The electrical characteristics (such as discharge current and power consumption) of the plasma jet obtained using a high voltage generator delivering a sin-wave signal varying from 13kVp-p to 17kVp-p at a resonance frequency of 5.5kHz, were measured/calculated. The best results (long plasma plume and intense plasma) were obtained with a reactor equipped with a thicker upper electrode and a thinner lower electrode. Using this configuration, a plasma plume 55mm long was reached at 17kVp-p and 7slm of helium.

Evaluation of Selected Properties of Dielectric Barrier Discharge Plasma Jet.

In the technological processes requiring mild treatment, such as soft materials processing or medical applications, an important role is played by non-equilibrium plasma reactors with dielectric barrier discharge (DBD), that when generated in noble gases allows for the effective treatment of biological material at a low temperature. The aim of this study is to determine the operating parameters of an atmospheric pressure, radio-frequency DBD plasma jet reactor for the precise treatment of biological materials. The tested parameters were the shape of the discharge (its length and volume), current and voltage signals, as well as the power consumed by the reactor for various composition and flow rates of the working gas. To determine the applicability in medicine, the temperature, pH, concentrations of H2O2, NO2- and NO3- and Escherichia coli log reduction in the plasma treated liquids were determined. The obtained results show that for certain operating parameters, a narrow shape of plasma stream can generate significant amounts of H2O2, allowing for the mild decontamination of bacteria at a relatively low power of the system, safe for the treatment of biological materials.

On design of plasma jet reactor for non-oxidative methane conversion.

Non-oxidative methane coupling in an atmospheric pressure plasma jet reactor with an internal diameter of 3.0 mm has been studied. The jet reactor consisted of a quartz tube surrounded by a copper ring and a stainless-steel tube, which were separated by a variable distance. The stainless-steel tube (inner diameter: 1.0 mm, outer diameter: 1.5 mm) served as high voltage electrode and gas inlet. The jet characteristics with different tip angles of the high voltage electrode were investigated using voltage-current waveforms and gas analysis at a constant methane flow rate of 100 ml min-1. The effect of the length of the ground electrode and the gap between the electrodes on conversion, C2 selectivity and energy efficiency has been studied. The methane conversion was nearly tripled with a sharp angle of the electrode (15°), while the energy consumption was reduced from 150 to 55 kJ molC2H y -1. The carbon deposition was also reduced.

A boundary value problem of heat transfer within DBD-based plasma jet setups.

We claim an analytical solution for the thermal boundary value problem that arises in DBD-based plasma jet systems as a preliminary and consistent approach to a simplified geometry. This approach involves the outline of a coaxial plasma jet reactor and the consideration of the heat transfer to the reactor solids, namely, the dielectric barrier and the grounded electrode. The non-homogeneous initial and boundary value thermal problem is solved analytically, while a simple cut-off technique is applied to deal with the appearance of infinite series relationships, being the outcome of merging dual expressions. The results are also implemented numerically, supporting the analytical solution, while a Finite Integration Technique (FIT) is used for the validation. Both the analytical and numerical data reveal the temperature pattern at the cross-section of the solids in perfect agreement. This analytical approach could be of importance for the optimization of plasma jet systems employed in tailored applications where temperature-sensitive materials are involved, like in plasma biomedicine.

Treatment of Escherichia coli contaminated water with different pulse-powered NTP configurations and analysis for post treatment efficacy

A cost-effective and energy efficient method for water sterilization is a challenging demand in the present scenario where scarcity of pure water is rising. Non-Thermal Plasma (NTP) finds promising applications in environmental processes and has advantages over conventional water treatment methods. Escherichia coli contaminated water treatment using multiple pin plasma reactor and atmospheric pressure plasma jet reactor was undertaken in this work. High voltage pulsed power was used for generating non-thermal plasma in these reactors and various configurations were tested for treating the contaminated water. The most feasible configuration among these was identified from the treatment efficiency and survival rate plots of E. coli colonies. It was observed that with an exposure of 15 min NTP, 100 percent bacterial removal was achieved using plasma jet reactor configuration. The presence of bacteria after NTP-treated time was also checked and confirmed for complete removal of bacteria. An optimum time of 15 min plasma exposure for 100 ml was found to be effective for complete removal of microorganisms and the sterility was maintained up to 60 min after the treatment. Non-thermal plasma-based treatment of bacteria-contaminated water is found to be promising and could be considered for scale-up and analysis.

Experimental Analysis of Cold Plasma With Glow Discharge Mechanism Under a Variety of Input Parameters

Cold plasma with a glow discharge mechanism is a homogeneous and effective mechanism of nonthermal plasma for industrial applications due to the continuous and stable discharge process compared with the filamentary discharge. The discharge mechanism is essentially dependent upon the input parameters of the plasma system, such as the voltage supply, excitation frequency, and the flow rate of the background gas. This article discusses the effects of input parameters on plasma discharge characteristics produced from the plasma jet reactor. The voltage and supply frequency are tuned to match the discharge gap and background gas flow rate in producing the homogeneous glow plasma discharge. The characteristics of the glow plasma discharge produced were analyzed based on the characteristics of the time–domain discharge current and charge-voltage Lissajous figure techniques. Results show that the most efficient and uniform plasma was disclosed by the configuration of input parameters such as 0.5 kV of the applied voltage, 20 kHz of operating frequency, and 0.8 L/min of purified helium gas flow rate. The single pulse of discharge current and parallelogram-like Lissajous figure obtained indicating the homogeneous plasma discharge with a constant value of discharge capacitance.

Production of Carbon from CO<sub>2</sub> and CO by Plasma Jet Reactor

Production of Carbon from CO<sub>2</sub> and CO by Plasma Jet Reactor

Atmospheric Plasma Jet processing for figure error correction of an optical element made from S-BSL7

To meet the increasing market demand for optical components, Plasma Jet Machining (PJM) of Borosilicate Crown Glass (BCG), which can be an alternative to Fused Silica, is presented. Surface figure error correction was performed by applying reactive plasma jet etching, where a fluorine-containing microwave driven plasma jet is employed to reduce the figure error in a deterministic dwell-time controlled dry etching process. However, some of the glass constituents of BCG cause the formation of a residual layer during surface treatment which influences the local material removal. By heating the substrate to about TS = 325 °C to 350 °C during processing, the etching behavior can clearly be improved. Geometric conditions of the optical element nevertheless lead to a characteristic temperature distribution on the substrate surface, which requires an adjustment of the local dwell times in order to obtain the required material removal. Furthermore, the resulting local surface roughness is also influenced by the surface temperature distribution. It is shown that figure error can be significantly reduced by taking the local temperature distribution and resulting local etching rates into account. A subsequent polishing step smoothens roughness features occurring during etching to provide optical surface quality.

Recursive algorithm for modeling non-linear etching rates in reactive plasma jet based optical surface machining of borosilicate crown glass

Application-specific optical glass properties are achieved by utilizing complex material compositions. This can be problematic in reactive plasma-assisted deterministic surface processing since a non-volatile surface layer may form depending on the glass composition, which affects the etch rate and thereby the local etching depth. In this investigation, a model algorithm is proposed to tackle some restrictions in applying fluorine-based plasma jet as etching tool utilized for freeform surface machining of optics made of complex glass composition, like borosilicate crown glass (e.g., N-BK7®). In this regard, firstly an analytical model is proposed for estimating the depth-dependent etch rate function. Subsequently, a recursive simulation algorithm is introduced for convolving the derived depth-dependent etch rate function with the given dwell time matrix to simulate a deterministic freeform generation process. By the proposed simulation algorithm, the impeding influence of the residual layer on the reduction of etching depth is computed prior to a real experiment in order to scale the local dwell time to ensure the targeted local removal. Finally, the simulated freeform shape is compared with the corresponding result of an etching experiment to validate the feasibility of the proposed approach.

Combined reactive plasma jet-laser etching method for technical optical glass containing metal oxides

The machining of optical glass materials with beam technologies enables novel fabrication processes for innovative optical elements with freeform surfaces. However, the complex material composition of optical glass such as N-BK7® is challenging for non-abrasive, pure chemical machining. N-BK7 can be machined utilizing reactive atmospheric plasma jet (RAPJ) etching. However, the etching mechanism results in process-inherent surface composition changes that limit potential applications of RAPJ-machining. A residues layer is formed which causes a temporally changing etching behavior and an increased roughness. Therefore, a process sequence of utilizing RAPJ etching and laser cleaning is proposed and demonstrated that enables to overcome the stated limitations. In this cyclic sequence, N-BK7 optical glass is etched first with a fluorine-containing reactive atmospheric plasma jet resulting in an etched but also residues-modified surface. Thereafter, the residues are removed by pulsed UV laser irradiation without ablation of the glass. This combined laser-enhanced reactive plasma jet etching allows etching of optical glass with a higher average etching rate and smoother machined surfaces.

A mixed type boundary-value problem related to the electrostatics of cold plasma jet reactors based on dielectric barrier discharge

A mixed type boundary-value problem related to the electrostatics of cold plasma jet reactors based on dielectric barrier discharge

An investigation on effectiveness of temperature treatment for fluorine‐based reactive plasma jet machining of N‐BK7®

AbstractIn this study, a fluorine‐based reactive plasma jet is investigated as a promising tool for ultraprecise surface machining of N‐BK7®. Plasma‐generated particles react with an N‐BK7 surface to create volatile and nonvolatile compounds. The desorption of volatile compounds results in an etched surface, whereas nonvolatile compounds form a residual layer in the etched area, causing unpredictable effects on the etching rate. Surface temperature treatment is proposed to improve the machining procedure with respect to deterministic material removal, leading to predictable results. It is shown that, at an elevated surface temperature, the residual layer properties are modified in favor of improved etching performance. The etching behavior of N‐BK7 is compared with fused silica to verify the optimality of the obtained results.

Efektivitas Perlakuan Kombinatif Plasma Medis dan Ekstrak Daun Sirih untuk Mempercepat Penyembuhan Luka Fase Proliferasi pada Model Mencit Diabetik

The continued increase in the number of people with Diabetes Mellitus (DM) in Indonesia is a serious problem. One of the big problems for people with Diabetes Mellitus (DM) is the emergence of complications of diabetic wounds. To date the strategy for treatment of diabetic wounds has been limited to the use of wound dressing, cell therapy and oxygen therapy. The problem is that the strategy is not fully successful. Thus, it is very important to look for new strategies to improve the quality of diabetic wound healing, such as by applying a combination of plasma medicine and local natural product, like the extraction of Daun sirih (Piper betle) leaves. Plasma medicine is a relatively new and multidisciplinary study involving plasma science, biomedical, pharmaceutical and other health sciences aimed at applying plasma to therapeutic health. Plasma is the fourth phase of matter, after the solid, liquid and gas phase. The medical aspects of plasma are related to the ability of plasma to produce biological molecules Reactive Oxygen and Nitrogen Species (RONS). If RONS is controlled in the right dosage it can be efficacious for health therapy. This study intends to examine the effects of combinative treatment of plasma medicine and Piper betel leaf extract for proliferation phase of wound healing in diabetic small animal model. This study used male Balb c mice with acute wounds which were divided into 5 groups, namely groups of untreated normal mice (ND-TP), groups of untreated diabetic mice (D-TP), groups of diabetic mice wounds with Piper betel leaf extract (DS ), the wound group of diabetic mice with plasma medicine (DP) and the wound group of diabetic mice with plasma medicine and Piper betel leaf (DPS). The plasma medicine was treated on wound with condition non-contact style (the plasma jet did not touch the wound) with a distance of plasma jet reactor nozzle to the surface of wound about 20 mm, for 2 minutes, every day. Macroscopic observation of wounds is carried out every day from day 0 to 7. On day 7 it was seen that the size of the wound area for D-P-S was smaller than the other groups. The results of this study indicated that Piper betel leaf extract can potentially be used to optimize the performance of plasma medicine in accelerating diabetic wound healing during the proliferation phase. Further investigation, however, is important to be conducted to study the effect for all phases of wound healing and its mechanism histo-pathologically.

Plasma-Chemical Synthesis of Graphene/Copper Nanocomposite

The effect of graphene doping with copper in a plasma jet reactor is studied. The effect is obtained during the synthesis of graphene in hydrocarbon-contating helium and nitrogen plasma jets generated by an electric arc plasma torch under reduced pressure. The graphene/copper nanocomposite synthesized has been studied by scanning electron microscopy, X-ray diffraction, and energy-dispersive X-ray microanalysis. It has been found that copper forms various bonds with carbon in graphene layers, which are due to interaction between the layers. It has been shown that the concentration of copper in the nanocomposite substantially depends on the composition of the plasma-forming gas and its flow rate.

Development of a model for ultra‐precise surface machining of N‐BK7® using microwave‐driven reactive plasma jet machining

AbstractIn this paper, extensive studies are conducted as key to overcoming several challenging limitations in applying fluorine‐based reactive plasma jet machining (PJM) to surface machining of N‐BK7®, particularly regarding the manufacture of freeform optical elements. The chemical composition and lateral distributions of the residual layer are evaluated by X‐ray photoelectron spectroscopy and scanning electron microscopy/energy‐dispersive X‐ray spectroscopy analysis aiming at clarifying the exact chemical kinetics between plasma generated active particles and the N‐BK7 surface atoms. Subsequently, a model is developed by performing static etchings to consider the time‐varying nonlinearity of the material removal rate and estimate the local etching rate function. Finally, the derived model is extended into the dynamic machining process, and the outcomes are compared with the experimental results.

Generic residual charge based model for the interpretation of the electrohydrodynamic effects in cold atmospheric pressure plasmas

In cold atmospheric pressure plasmas (CAPPs), the residual charges that exist in the wake of the streamers play an important role in the acceleration of the working gas. This paper presents a model that links the drift of the net residual ionic charge density, under the effect of the local electric field, with the momentum increase of the gas. In the model, the ions and the neutrals are considered as separate phases and the conservation equations for the two phases are connected via the ionic pressure. The residual charge density is quantified through an approximate approach that considers the streamer events to be ‘instantaneous’, in order to avoid the excessive computational cost of resolving the propagation of each streamer. For the validation of the residual charge model with the ‘instantaneous’ streamer approach, comparisons are made with experimental data from three plasma jet reactors. The electrode configuration of the reactors and the varied parameters (applied voltage, gas flow rate) are chosen so as to cover a broad range of different cases, in order to assess the generality of the model. The comparisons concern the gas flow and visible plasma patterns. It is found that the numerically simulated flow structures are in agreement with the corresponding schlieren images and that the residual charge density is a fair indicator of the visible plasma channel.

Development of DDBD and plasma jet reactors for production reactive species plasma chemistry

A novel Double Dielectric Barrier Discharge (DDBD) and an atmospheric pressure plasma jet (APPJ) was generated with a dielectric barrier discharge (DBD) column by AC high voltage have been developed. This reactor can produce cold atmospheric plasmas (CAP) that formed in air reactive oxygen species (ROS). These species among others are O3, H2O2, was quantified in the outlet of reactors. The analysis for ROS has been conducted by using medium that we call Plasma-Activated Medium (PAM). Some analysis conducted including variation of exposure times by ROS to the plasma-activated medium. In addition, concentration-voltage characteristics of ozone production. Peroxide Value, Acid Value and Viscosity of virgin coconut oil (VCO, as PAM) increased with increasing exposure time of O3. The concentration of hydrogen peroxide in water (as PAM) has been measured. The concentration of H2O2 179 μM with exposure time for 1 minute. The concentration of H2O2 in the study is quite high when compared with some other research results. The results showed that increased exposure time resulted in increased concentrations of ozone and hydrogen peroxide.

Main performance analysis of kitchen waste gasification in a small-power horizontal plasma jet reactor

Plasma gasification technology has been demonstrated in recent studies as one of the most effective and environmentally friendly methods for solid waste treatment, which could be attractive for resource and energy recovery from kitchen waste. This study focuses on the effects of plasma gasification of kitchen waste replaced by 85% flour and 15% vegetables (Mass Fraction), including dimensionless operation parameters, ER (equivalence ratio), SFR (steam to feedstock ratio) and the gasification efficiency. The Horizontal plasma jet reactor is employed in the experiments. It is found that the influence of the equivalence ratio on syngas can be divided into positive and negative parts. And the steam injection is conducive to improving the yield of syngas, which mainly results from the heterogeneous water gas shift reaction. The optimal experimental parameters can be obtained at ER = 0.095 and SFR = 0.084. Besides, the maximum first and second efficiency of plasma gasification during these cases occurs in SFB = 0.084, accounting for 28.2% and 23.0%, respectively, which needs to study further to get improvement. The XRD and Raman spectra are applied to characterize the residual char, which may illustrate that the degree of graphitization is competing with a high yield of syngas during plasma gasification.

Determination of the kinetic constants of the process of plasma gasification of coal-water fuel

The chemical kinetics of processes of thermal transformations of carbon-containing media was studied at high-temperature processing (2000 K ≤ T ≤ 5000 K) in the chamber of a plasma-jet reactor using water vapor as an oxidizer. The chemical reactions rate was calculated according to the method of determining the kinetic constants of the process of gasification of coal-water fuel. The influence of the temperature of the gaseous environment in the chamber on the time of complete carbon conversion of the fuel particles is established. An example of calculating the parameters of the gasification process of coke residue particles with a size of (5 - 20)·10-5 m with an oxidizer excess coefficient α = 0.45 and fuel consumption mf = 100 kg/hr is given. The expediency of the process of vapor-plasma gasification at the temperature of gases in the reactor chamber up to 3000 K is shown.