Microwave Plasma Treatment Research Articles

Unveiling The Potential of Microwave Plasma Treated Char For Sustainable Automotive Shredder Residue (ASR) Management and Reduced Ecological Risk Of Cadmium

Introduction: This study explores the effectiveness of microwave plasma pyrolysis in reducing heavy metal concentrations, specifically cadmium, in automobile shredder residue (ASR). METHOD: The ASR was subjected to plasma pyrolysis at microwave power levels ranging from 800 to 1000W, resulting in a significant decrease in heavy metal concentration in the char. Utilizing the Bureau Communautaire de Référence (BCR) sequential extraction method, a standardized procedure developed by the European Commission, we assessed the chemical speciation and matrix properties of the char. The results indicated that microwave plasma treatment effectively decreased the bioavailable forms of cadmium. After 6 minutes of pyrolysis at 1000W, the exchangeable and acid-soluble fractions (F1) dropped to 10%, while the reducible fraction (F2) fell to 12%. RESULT: This treatment resulted in a substantial increase in the oxidizable (F3) and residue (F4) fractions, which reached 27% and 51%, respectively. Importantly, the potential ecological risk of cadmium decreased significantly, with the risk index (Er) dropping from 164.91 to 28.45, aligning with Taiwan's regulatory standards for non-hazardous waste.CONCLUSION: These findings suggest that microwave plasma pyrolysis is a promising and sustainable approach for the disposal of ASR, offering an environmentally friendly alternative for waste management. This study provides valuable insights for policymakers, environmental scientists, and industries seeking effective solutions for ASR treatment.

Microwave-plasma surface modification of nanostructured-polyaniline:graphite composite counter electrode in dye-sensitized solar cells

This work demonstrates microwave plasma surface modifications of nanostructured polyaniline (NPES)-based counter electrodes (CE). Oxidative oxygen (O2) plasma and reductive hydrogen (H2) plasma were used in this study. Optical emission spectra confirm the presence of reactive species in both plasmas through the emissive species, such as O2+, O+, O•, H(nl), and H2 Fulcher-α. Microwave plasma treatment does not affect the surface morphology of NPES composite CE, which conserves its granule nanostructures, as revealed by SEM. The water contact angle measurements demonstrate how the O2 plasma treatment improves surface hydrophilicity, contrary to the H2 plasma treatment. Raman spectroscopy results show significant changes in the intrinsic-oxidation state and the number of semiquinonoid species (SQ) of NPES after plasma treatments, which are represented by the ratios of Raman intensity at 1368–1260 cm−1 and 1624–1583 cm−1, respectively. Generally, O2 plasma treatment increases the intrinsic-oxidation state and SQ number, opposite to the H2 plasma. The optimum condition of microwave plasma-assisted surface modification was attained in one minute of O2 plasma treatment, producing NPES with the highest intrinsic-oxidation state and SQ number. A power conversion efficiency of 3.17 % was obtained by a dye-sensitized solar cell fabricated with a modified CE using a one-minute O2 plasma treatment.

Study of Cation Distribution and Photocatalytic Activity of Nonthermal Plasma-Modified NiZnFe2O4 Magnetic Nanocomposites.

In this study, NiZnFe2O4 composite was synthesized using a sol-gel route and subjected to nonthermal plasma treatment for tailoring their cations' distribution and physicochemical, magnetic, and photocatalytic properties. Microwave plasma treatment was given to the composites for 60 min in support of postsynthesis sintering at 700 °C for 5 h. X-ray diffraction (XRD) analysis was conducted on pre- and postplasma-modified ferrite composites to identify phase-pure cubic spinel structure and cations' distribution. The cation distributions were measured from the ratio of XRD intensity peaks corresponding to (220), (311), (422) and (440) planes. The intensity ratio of plasma-treated ferrite composites decreased compared to that of pristine composites. The crystallite size and lattice constant were increased on plasma treatment of the composite. The morphological analysis showed nanoflower-like structures of the particles with an increased surface area in the plasma-treated composites. The plasma oxidation and sputtering effects caused a reduction in the nanoflower size. The energy bandgap increased with a decrease in particle size due to plasma treatment. The rhodamine B dye solution was then irradiated with a light source in the presence of the nanocomposites. The dye degradation efficiency of the composite photocatalyst increased from 80 to 96% after plasma treatment.

Microwave and dielectric barrier discharge atmospheric plasma interaction on guava industrial biomass for biomaterial production

AbstractThis research helps to develop a novel and economical method for improving the extraction efficiency of oil and fully valorizing guava fruit processing industrial waste into biomaterial. Dielectric barrier discharge atmospheric (DBDA) plasma is a novel non‐thermal technology that has been widely used in the food processing field of research. In this study, the synergistic effect of microwave (MW) and DBDA plasma treatment under different treatment combinations on the modification of morphological and biochemical properties of the guava pomace powder on improving the efficiency of extraction of biomaterials has been investigated. The response surface model (RSM) model was then constructed using the experimental results of Box–Behnken Design (BBD) to obtain the optimal extraction conditions. The predicted optimal extraction conditions for the microwave power level of 600 W for a treatment time of 90 s under solvent extraction at 420 min; DBDA plasma treatment as 35 kV for 15 min and solvent extraction conditions were determined as 80°C for 360 min causing an increment of the oil yield up to 16.19% when extracted using solvent extractor with ethanol as a solvent. These results indicate that the DBDA plasma treatment previous to the extraction step extraction process can contribute to reducing the duration of extraction by 120 min. The obtained data indicate that the MW and DBDA plasma pre‐treatment before the extraction can reduce the extraction duration, increase the yield, and improve the nutritional quality and functional properties.

Facile microwave synthesis of multi‐walled carbon nanotubes for modification of elastomer used as heaters

AbstractMulti‐walled carbon nanotubes (MWCNTs) were synthesized by a microwave method. MWCNTs had filamentous shapes (10 μm) and were intertwined in bundles (40–60 nm diameter). The rapid oxidation of MWCNTs with a loss of 90% of weight was observed from 530 to 630°C. 2% Residue was present at 630°C, which gradually decreased to 1.2% at 1000°C. In a silicone elastomer, increased thermal conductivity at a concentration of 8% MWCNTs was observed. The highest thermal conductivity of the nano‐modified elastomer was 0.48 W/m°C with 8.0 wt% MWCNTs. The highest electrical conductivity was 2.4 × 10−5 S cm−1 at 8.0 wt% MWCNTs. Both the thermal and electrical conductivities showed percolation behavior with the percolation thresholds at 6 and 5 wt%, respectively. The MWCNTs synthesized by microwave method gave a good power economy in comparison to MWCNTs obtained by chemical vapor deposition (CVD) on NiMg catalyst. Microwave‐synthesized MWCNTs showed high stability at a potential of 250 V in an electrical resistance heater application due to the presence of Fe on the surface of MWCNTs. The developed heater can effectively operate at 220 V, which enables the use of the tubes in household appliances, such as heat fans, irons, and washing machines.Highlights Synthesis of MWCNTs by microwave plasma treatment of ferrocene and graphite. Characterization of MWCNTs by different techniques. Concentration dependence of electro‐ and thermal conductivity of MWCNTs in elastomers. Electro‐physical parameters studies of elastomers modified with MWCNTs. Heat generation studies in elastomeric matrix with MWCNTs.

Impact of microwave plasma treatment on tritium retention in submicronic tungsten dust

In the current paper, we have studied the impact of microwave (2.45 GHz) plasma treatment of submicronic (250–600 nm) tungsten dust, upon tritium gas retention. Herein, the conducted experiments have emphasized the role of dust treatments in pure hydrogen gas versus hydrogen plasma, before the tritiation process at different pressures. The obtained tritiated dust was analyzed via room temperature desorption and dissolutions. Additionally, Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy analyses were performed to observe the changes induced by the plasma discharge. The results have shown that the Specific Surface Area of dust is enhanced by using microwave hydrogen plasma treatments, resulting in a high tritium gas retention inside the submicronic tungsten dust.

Rapid hydrophobicity recovery of contaminated silicone rubber using low-power microwave plasma in ambient air

The loss of hydrophobicity of silicone rubber (SR) insulators due to contamination accumulation will increase the risk of flashover and threaten the stability of electrical power system. To solve this problem, a highly efficient and environmentally friendly microwave plasma surface treatment method is developed, which only consumes low-power electricity and ambient air without any chemical agent or rare gas. The hydrophobicity of seriously contaminated SR can be recovered on the order of 10 s, with a nice long-term aging performance under natural transfer. The underlying mechanism is revealed via carefully designed control experiments and systematic surface analysis. It is illustrated that the plasma-generated active species break the long chain of SR into non-crosslinked low-molecule-weight siloxanes (LMWs) and accelerate their transfer to contamination layer, while the bombing and etching effects of plasma manufacture a porous structure and increase the surface roughness. All of these factors will contribute to the increase of hydrophobicity. On the contrary, the oxidation effect of plasma will turn LMWs into polar groups and destroy the hydrophobicity, which should be restricted in practice. The microwave plasma treatment method developed in this work has the on-line application potential in power system for hydrophobicity recovery under severe contamination conditions.

An atmospheric microwave plasma-based distributed system for medical waste treatment.

Inadequate handling of infectious medical waste may promote the spread of the virus through secondary transmission during the transfer process. Microwave plasma, an ease-of-use, device-compact, and pollution-free technology, enables the on-site disposal of medical waste, thereby preventing secondary transmission. We developed atmospheric-pressure air-based microwave plasma torches with lengths exceeding 30cm to rapidly treat various medical wastes in situ with nonhazardous exhaust gas. The gas compositions and temperatures throughout the medical waste treatment process were monitored by gas analyzers and thermocouples in real time. The main organic elements in medical waste and their residues were analyzed by an organic elemental analyzer. The results showed that (i) the weight reduction ratio of medical waste achieved a maximum value of 94%; (ii) a water-waste ratio of 30% was beneficial for enhancing the microwave plasma treatment effect for medical wastes; and (iii) substantial treatment effectiveness was achievable under a high feeding temperature (≥ 600°C) and a high gas flow rate (≥ 40 L/min). Based on these results, we built a miniaturized and distributed pilot prototype for microwave plasma torch-based on-site medical waste treatment. This innovation could fill the gap in the field of small-scale medical waste treatment facilities and alleviate the existing issue of handling medical waste on-site.

Microwave plasma torches for solid waste treatment and vitrification.

Conventional thermal plasma technology used in the treatment of solid waste has a high demand for power and a high rate of heat loss during solid waste treatment. We developed a novel approach for treating and vitrifying solid waste with a low-power microwave plasma torch (MPT). Based on theoretical thermodynamic equilibrium calculations, we studied the melting temperature of the residual ash and achieved vitrification of the residual ash with an MPT by adding specified ratios of discarded glass scraps. Thermocouples and a gas analyzer were used to characterize the temperature variations and gas concentrations in the plasma treatment chambers, respectively. An organic elemental analyzer and X-ray fluorescence (XRF) analyses were used to determine the chemical proportions of the solid waste residues. The morphologies of the residues and vitreous material were analyzed using scanning electron microscopy (SEM). The results showed that the microwave plasma treatment process converted 96 wt.% of the solid wastes into nonpolluting gases, leaving a residue of pure carbon and inorganic powder. Through theoretical calculations and experiments, atmospheric MPTs with power levels less than 10kW were identified as realistic means for treating and vitrifying solid wastes.

Enhancing the electrochemical performance of TiO2 based material using microwave air plasma treatment with an ECR cavity.

The microwave-based plasma treatment facility at the Central University of Punjab Bathinda (CUPB) based on 2.45GHz has been used to investigate the impact on the electrochemical performance of TiO2. This was accomplished by treating a number of pellets of TiO2 sample material with microwave plasma at an input power of 80W. The palette is subjected to microwave plasma treatment at 30-, 60-, 80-, and 100-s intervals. Many such characterization methods, including UV-visible spectroscopy, FTIR, XRD, and FESEM, have been applied to the study of the impact of plasma treatment on other physical and chemical properties in the context of untreated pellets. In the 80-s plasma treatment, the FTIR study showed that the (O-Ti-O) vibration band at 500-900cm-1 was wider than other bands. The UV results showed that an 80-s plasma treatment decreased the sample's band gap by 37% and increased the amount of disordered, amorphous material in the sample that had not been treated. XRD studies show that a sample that was treated with plasma for 80s has low crystallinity and a high disorder (amorphous) factor. The Nyquist plot showed that the electrochemical charge transfer resistance drops from 7 (not treated) to 4 after 80s of plasma treatment. In a study of electrochemical performance, a sample that was treated with plasma for 80s has a capacitance that is 35% higher than a sample that was not treated.

Effects of various microwave intensities collaborated with different cold plasma duration time on structural, physicochemical, and digestive properties of lotus root starch

Lotus root starch was treated with single and combined microwave (300 and 700 W) and cold plasma (60, 90, and 120 s) treatments. Effects of treatments on multi-structural, physicochemical, and digestive properties of lotus root starch were investigated. The results revealed that a combination of cold plasma and microwave treatments significantly affected the morphology of starch granules and reduced the relative crystallinity of starch compared with a single treatment. However, no changes were found in the chemical functional groups of starch after single or combined treatments. Additionally, the amylose content, amylopectin branch chain length distribution, solubility, and swelling power of the starch significantly varied depending on cold plasma treatment duration and microwave power. Furthermore, the treated starch showed lower peak viscosity and higher pasting temperature than the native one. Moreover, the resistant starch content significantly decreased as cold plasma treatment was prolonged and microwave power increased.

Microbial Control of Raw and Cold-Smoked Atlantic Salmon (Salmo salar) through a Microwave Plasma Treatment.

The control of the pathogenic load on foodstuffs is a key element in food safety. Particularly, seafood such as cold-smoked salmon is threatened by pathogens such as Salmonella sp. or Listeria monocytogenes. Despite strict existing hygiene procedures, the production industry constantly demands novel, reliable methods for microbial decontamination. Against that background, a microwave plasma-based decontamination technique via plasma-processed air (PPA) is presented. Thereby, the samples undergo two treatment steps, a pre-treatment step where PPA is produced when compressed air flows over a plasma torch, and a post-treatment step where the PPA acts on the samples. This publication embraces experiments that compare the total viable count (tvc) of bacteria found on PPA-treated raw (rs) and cold-smoked salmon (css) samples and their references. The tvc over the storage time is evaluated using a logistic growth model that reveals a PPA sensitivity for raw salmon (rs). A shelf-life prolongation of two days is determined. When cold-smoked salmon (css) is PPA-treated, the treatment reveals no further impact. When PPA-treated raw salmon (rs) is compared with PPA-untreated cold-smoked salmon (css), the PPA treatment appears as reliable as the cold-smoking process and retards the growth of cultivable bacteria in the same manner. The experiments are flanked by quality measurements such as color and texture measurements before and after the PPA treatment. Salmon samples, which undergo an overtreatment, solely show light changes such as a whitish surface flocculation. A relatively mild treatment as applied in the storage experiments has no further detected impact on the fish matrix.

Effects of microwave plasma treatment on β-Ga2O3 Schottky barrier diodes

In this work, the effects of O2 or N2 microwave plasma treatment on β-Ga2O3 surface prior to Schottky metal deposition are reported. The device uniformity of Schottky barrier diodes is improved significantly by the microwave plasma treatments without any degradation such as ideality factor (near 1.0), and on-state resistance (R on ∼3 mΩ cm2). The standard deviation of Schottky barrier height (SBH, φB) is as small as less than 10 m eV. Kelvin probe force microscope analysis shows that the surface electrostatic potential after O2 microwave plasma treatment is lower than that of the N2 microwave plasma treatment, which is consistent with the change of SBH obtained by capacitance–voltage (C–V) and current–voltage (I–V) measurements. The relatively low SBH with O2 microwave-plasma treatment corresponds to the high reverse leakage current. The oxygen related adsorption at metal/Ga2O3 interface by O2 microwave plasma treatment confirmed by x-ray photoelectron spectroscopy can be attributed to the SBH and surface potential lowing.

Enhancement of Magnetic and Dielectric Properties of Ni0.25Cu0.25Zn0.50Fe2O4 Magnetic Nanoparticles through Non-Thermal Microwave Plasma Treatment for High-Frequency and Energy Storage Applications.

Spinel ferrites are widely investigated for their widespread applications in high-frequency and energy storage devices. This work focuses on enhancing the magnetic and dielectric properties of Ni0.25Cu0.25Zn0.50 ferrite series through non-thermal microwave plasma exposure under low-pressure conditions. A series of Ni0.25Cu0.25Zn0.50 ferrites was produced using a facile sol–gel auto-ignition approach. The post-synthesis plasma treatment was given in a low-pressure chamber by sustaining oxygen plasma with a microwave source. The structural formation of control and plasma-modified ferrites was investigated through X-ray diffraction analysis, which confirmed the formation of the fcc cubical structure of all samples. The plasma treatment did not affect crystallize size but significantly altered the surface porosity. The surface porosity increased after plasma treatment and average crystallite size was measured as about ~49.13 nm. Morphological studies confirmed changes in surface morphology and reduction in particle size on plasma exposure. The saturation magnetization of plasma-exposed ferrites was roughly 65% higher than the control. The saturation magnetization, remnant magnetization, and coercivity of plasma-exposed ferrites were calculated as 74.46 emu/g, 26.35 emu/g, and 1040 Oe, respectively. Dielectric characteristics revealed a better response of plasma-exposed ferrites to electromagnetic waves than control. These findings suggest that the plasma-exposed ferrites are good candidates for constructing high-frequency devices.

Microbial control of raw and cold-smoked Atlantic salmon (Salmo salar) through a microwave-plasma treatment

Microbial control of raw and cold-smoked Atlantic salmon (Salmo salar) through a microwave-plasma treatment

Evaluation of structural, morphological, optical, and electrical properties of zinc oxide semiconductor nanoparticles with microwave plasma treatment for electronic device applications

ZnO is an important II-IV n-type direct bandgap semiconductor material that has exhibited wide consideration due to its applications in optoelectronic devices. In the present investigation, untreated and plasma-treated ZnO NPs were fabricated by a sol-gel route and analyzed with XRD, Raman, UV-Vis spectra, and I–V characteristic techniques. To be used in electronic applications, the ZnO nanoparticles were subjected to a plasma treatment process to tune their optical, vibrational mode, structural and electrical properties. XRD confirmed the pure Wurtzite tetragonal phase crystalline nature of produced samples. The average crystalline size, lattice constant, unit cell volume, and porosity were found in the range of 3.81–4.68 nm, a = 3.217–3.323 Å and c = 2.032–2.178 Å, 5.662–11.274 Å3 and 7.09–5.03%, respectively. The Raman spectra revealed that the intensity of Raman bands was increased due to the increase in the vibrational amplitude and increase in force constants with the enhancement in grain size, these spectra results are in good agreement with XRD and reveal the purity of samples. The bandgap found reduced from 3.56 eV to 3.39 eV by plasma treatment. The electrical studies revealed that plasma treatment improves the electrical properties of ZnO NPs without producing any structural distortions. I–V characteristic curves confirmed that the conductivity was increased from 8.3 X 10−6 to 5.5 X 10−4 ℧ cm−1 on plasma treatment which caused an increase in leakage current. The improved structural, vibrational mode, optical and electrical properties of prepared ZnO NPs make them a suitable candidate for application in electronic devices.

Evaluation of cold atmospheric microwave plasma on skin physiological parameters and tolerability in dogs.

Cold atmospheric microwave plasma (CAMP) is a promising therapeutic option for treating skin infections and wounds. Changes in biophysical skin parameters and the tolerability in dogs after applying CAMP is unknown. This study aimed to evaluate the in vivo effects of CAMP on skin biophysical parameters [hydration, transepidermal water loss (TEWL) and surface temperature] and tolerability in dogs. Twenty client-owned dogs with normal skin. Cold atmospheric microwave plasma treatment was performed for 30 s and 1, 2 and 4 min, respectively, at different sites of normal canine skin in the inguinal area. Hydration, TEWL and surface temperature were measured five, three and three times, respectively, before and after CAMP application. After treatment, pain and adverse effects were evaluated using a modified Melbourne Pain Scale and the modified short form Glasgow Composite Measure Pain Scale (modified CMPS-SF). Transepidermal water loss values significantly decreased with 4 min of treatment, and hydration decreased significantly with 2 min of treatment. Temperature increased significantly with increasing treatment time. For other parameters, no significant changes were observed. No significant pain response or adverse effects were observed in most dogs, aside from mild erythema in the treatment area after 4 min. Cold atmospheric microwave plasma treatment was well-tolerated and did not significantly change canine skin biophysical parameters. CAMP achieves basic recommendations for safe use and is a potential therapeutic option for various skin diseases in dogs.

Evaluation of graphitization and tensile property in microwave plasma treated carbon fiber

Plasma technology can be used as a green and novel method for the graphitization of carbon fiber. The effect of graphitization time on the main element content along with microstructure of carbon fiber in the plasma treatment process was investigated. It took an extremely short time (less than 100 ms) for the temperature of the system to increase until a relatively stable stage was reached. Furthermore, compared with the original carbon fiber, the increase in the carbon content and graphitization degree of carbon fiber was observed after microwave plasma treatment. Moreover, the original imperfect turbostratic graphite-like structure transformed to an ordered graphite structure with the escape of non‑carbon elements from the disordered region of graphite-like crystallites. With the graphitization time of 180 s and microwave power of 800 W, corresponding to the temperature of 2100 °C, a high graphitization degree (R = 0.61) was observed and the crystallite size was as large as 5.10 nm, which are better than that of M40J and T800H. After 5 mins treatment, the average tensile modulus of samples apparently increased by 23% from 189 GPa to 245 GPa. This work demonstrated that the microwave plasma is an alternative approach for the development of carbon fibers with good microstructure and high graphitization degree.

Effect of radical on defect and molecular structure of monolayer MoS2 by low temperature plasma treatment

The aim of this study is to form the sulfur defects on monolayer molybdenum disulfide (MoS2) by low temperature microwave plasma treatment suppressing disturbance of molecular structure. CVD-grown and plasma treated multilayer MoS2 surface were analyzed to investigate the effects of H2 and Ar plasma treatment on sulfur defects and molecular structure. It was found that the disturbance of molecular structure was suppressed in the H2 plasma treatment compared to the Ar plasma treatment. Varying the incident ratio of hydrogen ions H+ and radicals H*, the influences of H2 plasma treatment with high and low H*/H+ ratio on monolayer MoS2 structure were discussed. As a result of X-ray photoelectron spectroscopy, Raman spectroscopy and photoluminescence analysis, sulfur defects increased with the increase in total amount of radical incident on MoS2. In addition, it is speculated that the etching with radical contributed to form sulfur defects suppressing the disturbance of molecular structure.

Microwave plasma treatment of NiCuZn ferrite nanoparticles: a novel approach of improving opto-physical and magnetic properties

Microwave plasma treatment of NiCuZn ferrite nanoparticles: a novel approach of improving opto-physical and magnetic properties