Microwave-induced Plasma System Research Articles

Efficient degradation of Fipronil in water by microwave-induced argon plasma: Mechanism and degradation pathways

Fipronil and its metabolites are potentially harmful to the ecological environment and have chronic neurotoxic effects, which makes it to be classified as class C carcinogens. Fipronil has been banned from agricultural use in China since 2009, but its residue remains in the environment. Therefore, an efficient and economical method is urgently needed to degrade fipronil residues in the environment. Herein, the degradation of fipronil in water solution using argon microwave-induced plasma (MIP) system was studied and a plausible reaction pathway was proposed in combination with Density Functional Theory (DFT) calculations. The degradation of fipronil by MIP system was optimized in terms of input power, plasma-sample distance, initial concentration and gas flow rate. After short time MIP treatment with an input power of 150 W, as high as 85.62% degradation efficiency was achieved for the fipronil at concentration of 20 mg·L‐−1 under the optimized conditions, and the corresponding energy efficiency was 1334.8 mg·kwh−1. Optical emission spectrometry (OES) was employed to characterize the distribution and intensity of OH, H and O species which play key roles in the degradation of fipronil by plasma, and it revealed that the degradation reaction mainly occurs at gas-liquid interface where the highest intensity of OH, H and O species was observed. High resolution mass spectrometric analysis in combination quantum chemical calculations indicate that a wide diversity of reaction processes occurred for fipronil degradation under MIP treatment, involving oxidation or reduction, nitro reduction, oxidative dichlorination, reductive dichlorination, hydration, dehydration and thiourea to urea. The possible degradation mechanism and pathways were proposed based on the degrading species identified by high resolution Mass Spectrometry (HRMS) and the thermodynamic profiles.

Role of ponderomotive force in sustaining plasma discharge in a microwave induced plasma system

This paper discusses the nature of the plasma equilibrium in a microwave induced plasma under STP conditions. The plasma is generated out of water spray with dissolved minerals. It is known [] that plasma is not generated unless the water droplets are introduced in an iris region of the waveguide. To understand this, the plasma generation process was simulated in a coupled Matlab-Comsol simulation and different iris configurations were studied. The simulation confirms that the iris provides the necessary ponderomotive force required to confine the plasma. In the absence of the iris, plasma does not form in the simulation and in the experiment. This confirms that ponderomotive force is necessary for the plasma formation. The plasma and field profiles obtained in the simulation are presented and the role of the ponderomotive force is established.

Design of a portable optical emission tomography system for microwave induced compact plasma for visible to near-infrared emission lines.

A new non-invasive diagnostic system is developed for Microwave Induced Plasma (MIP) to reconstruct tomographic images of a 2D emission profile. A compact MIP system has wide application in industry as well as research application such as thrusters for space propulsion, high current ion beams, and creation of negative ions for heating of fusion plasma. Emission profile depends on two crucial parameters, namely, the electron temperature and density (over the entire spatial extent) of the plasma system. Emission tomography provides basic understanding of plasmas and it is very useful to monitor internal structure of plasma phenomena without disturbing its actual processes. This paper presents development of a compact, modular, and versatile Optical Emission Tomography (OET) tool for a cylindrical, magnetically confined MIP system. It has eight slit-hole cameras and each consisting of a complementary metal-oxide-semiconductor linear image sensor for light detection. The optical noise is reduced by using aspheric lens and interference band-pass filters in each camera. The entire cylindrical plasma can be scanned with automated sliding ring mechanism arranged in fan-beam data collection geometry. The design of the camera includes a unique possibility to incorporate different filters to get the particular wavelength light from the plasma. This OET system includes selected band-pass filters for particular argon emission 750 nm, 772 nm, and 811 nm lines and hydrogen emission H(α) (656 nm) and H(β) (486 nm) lines. Convolution back projection algorithm is used to obtain the tomographic images of plasma emission line. The paper mainly focuses on (a) design of OET system in detail and (b) study of emission profile for 750 nm argon emission lines to validate the system design.

Fast Etching of Molding Compound by an Ar/O2/CF4 Plasma and Process Improvements for Semiconductor Package Decapsulation

Decapsulation of a SOT23 semiconductor package with 23 um copper wire bonds is conducted with an especially designed microwave induced plasma system. It is found that a 30%-60% CF4 addition in the O2/CF4 etchant gas results in high molding compound etching rate. Si3N4 overetching which is encountered in plasma decapsulation is solved by an improved etching process. Critical processing parameters are investigated and 350 um thick molding compound on top of the die is removed selectively by pure plasma etching for 6 minutes, which is at least 10 times faster than conventional plasma etchers.

Development of compact high voltage switched mode power supply for microwave plasma sources supply for low pressure plasma

Although microwave induced plasmas are well known as high efficiency plasma sources, their uses in laboratories are limited since the microwave power systems are complicated and expensive. The output power of commercially available low-cost microwave ovens is fixed and discontinuous resulting from the high voltage doubler topology of the magnetron tube power supply. In this paper, a high voltage switched mode power supply of forward topology has been developed for continuous microwave power radiation. The forward converter can generate a no-load high voltage output maximum of 7 kV. When driving the magnetron tube, the microwave output power could be varied from 0 to 35 W while the high voltage output level was constantly regulated at -3.4 kV. A microwave induced plasma system was setup to investigate the plasma produced. A low pressure argon plasma was produced with only 2 W over a wide range of pressures.

Plasma Etching for Failure Analysis of Integrated Circuit Packages

Plastic integrated circuit packages with copper wire bonds are decapsulated by a Microwave Induced Plasma system. Improvements on microwave coupling of the system are achieved by frequency tuning and antenna modification. Plasmas with a mixture of O2 and CF4 showed a high etching rate around 2 mm3/min. The role of O2 and CF4 in etching molding compound is described. Plastic package with 38 um Cu bond wires and a 2 mm * 3.5 mm die inside is fully decapsulated in 20 minutes. Cu wires remain undamaged after decapsulation proving the efficiency of this method.

Escherichia coli sterilization and lipopolysaccharide inactivation using microwave-induced argon plasma at atmospheric pressure

Upon fabricating medical devices and biomaterials, the inactivation of microorganisms harmful to human is very important. It is more important to remove killed bacteria and their debris, particularly pyrogens such as lipopolysaccharide (LPS) from medical devices. LPS, referred to as endotoxin, is derived from the cell wall of gram-negative bacteria and well-known for inducing various pathological diseases. In this study, the sterilization of Escherichia coli ( E. coli) and elimination of E. coli-derived LPS were examined by using our self-designed microwave-induced plasma system at atmospheric pressure. Plasma treatment resulted in complete sterilization of E. coli after 1 s, which was confirmed by morphological alterations such as ruptured membranes and amorphous structures. Furthermore, LPS was completely inactivated after 10 s of plasma treatment. These results suggest that microwave-induced plasma will not only be effective on E. coli sterilization, but will also be able to remove LPS from the surface of the objects being sterilized.

Microwave Induced Plasma (MIP) Brazing of Silicon Nitride to Stainless Steel

AbstractIn an attempt to accelerate the process of joining of metals to ceramics, a new rapid brazing technology has been developed. In this process, referred to as Microwave Induced Plasma (MIP) brazing, a microwave plasma is used to rapidly heat the ceramic and metal to the melting temperature of the reactive braze material. The heating rate obtained by MIP could be many times faster than those achieved by conventional resistive heating in a tube furnace. The fast heating rate has no detrimental effect on the joint quality and in fact results in the formation of a thick interfacial film suggesting significant interdiffusion between the braze and ceramic, possibly stimulated by the microwave radiation. In this paper the experimental arrangement of the MIP system is described. The unique capability of the MIP heating is demonstrated by successful joining of hot pressed silicon nitride to stainless steel using reactive metal brazing. The results of microstructural characterisation of the joints carried out by SEM and EDS will also be presented.

A Dual Microwave-Induced Plasma System with Direct Solution Introduction for Atomic Emission Spectrometry

A dual microwave-induced plasma (MIP) for atomic emission spectroscopic (AES) system is described. The first plasma with low power (95 W) and low argon flow (<550 ml/min) is used as a sampling device to desolvate and vaporize liquid samples into gaseous particles which are subsequently transported to a second plasma (100 W) for atomization and excitation. The detection limits obtained for direct liquid aerosol introduction of Ca, Cr, Mn, and Sr solutions are 22, 60, 15, and 11 ng/ml, respectively. Signal precisions are <2.0% RSD for 5 ppm solutions and the linear response ranges are greater than 3 orders of magnitude.

Factorial analysis and response surface of a gas chromatography microwave-induced plasma system for the determination of halogenated compounds

In this work the applicability of the factorial analysis and response surface technique has been established in order to optimize a gas chromatography microwave-induced plasma system with a surfatron cavity. The forward power and the flow rate of the plasma gas were found to be the most critical parameters. Prediction equations and response surface plots were obtained for chlorobenzene and bromobenzene. Detection limits for chlorine and bromine determination under optimum conditions were comparable to those obtained by other workers using a ‘one variable at a time’ method.

Direct determination of aqueous carbon, phosphorus and sulfur using a kilowatt-plus helium microwave-induced plasma system with ultrasonic nebulization

Download options Please wait... Article information DOI https://doi.org/10.1039/JA9920701249 Article type Paper Download Citation J. Anal. At. Spectrom., 1992,7, 1249-1252 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Direct determination of aqueous carbon, phosphorus and sulfur using a kilowatt-plus helium microwave-induced plasma system with ultrasonic nebulization M. Wu and J. W. Carnahan, J. Anal. At. Spectrom., 1992, 7, 1249 DOI: 10.1039/JA9920701249 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Mingin Wu Jon W. Carnahan

Automation of a wire-filament atomiser helium microwave-induced plasma system

An autosampler has been constructed to introduce microlitre samples into a low-power, helium microwave-induced plasma/electrothermal atomisation atomic emission spectrometry system resulting in improvements to the analytical precision. Computer control of sample introduction, wire filament heating and data acquisition has greatly enhanced the use of the technique and enables further processing of acquired data.

Interferences due to easily ionised elements in a microwave-induced plasma system with graphite-furnace sample introduction

Several aspects of both enhancement and suppression of the analyte emission intensity caused by an easily ionised element (EIE) have been studied in an atmospheric pressure He microwave-induced plasma (MIP). A sequence of experiments, designed to elucidate possible mechanisms of this EIE effect, examines the following aspects: the concentration dependence of the effect for various EIEs; spatially separated vaporisation of EIE and analyte into the plasma; the effect of operating parameters upon the EIE-induced enhancement; the influence of the EIE on the excitation temperature and on the efficiency of coupling of microwave energy to the cavity. The EIE-induced suppression of emission intensity is consistent with reduced power dissipation in the plasma, due to decoupling of the plasma from the microwave power source, whereas the EIE-induced enhancement of emission intensity is best explained by a radiative energy transfer mechanism.

A microwave induced plasma system for the maintenance of moderate power plasmas of helium, argon, nitrogen and air

A microwave induced plasma system capable of maintaining stable plasmas of each of the gases helium, argon, nitrogen and air is presented. The system is capable of operation at powers of up to 500 W. The TM 010 cavity design is similar to that previously described in the literature with some modifications. A demountable torch facilitates centering of diffuse plasmas of helium, nitrogen and air by providing 6 flows directed tangentially within the quartz tube. This torch was not useful for argon plasmas. Toroidal argon plasmas were maintained with a threaded quartz tube arrangement. The heat generated by these plasmas was dissipated by an outer sheath of coolant air. Details of the design and preliminary characterization of each plasma system is presented.

Influence of pressure on the properties of a microwave-induced plasma

The argon excitation temperature, OH rotational temperature, electron density, and relative line radiances have been measured as the pressure is varied from 10 to 760 torr in a unique, variable-pressure microwave-induced plasma system. The influence of power and flow rate on low (50 torr), medium (220 torr), and atmospheric-pressure plasmas is presented. Changes in behavior of the plasma at pressures below 100 torr are observed which are consistent with a relative decrease in nonradiative processes and thus a proportional increase in radiative processes at reduced pressures.