Plasma Gas Flow Rate Research Articles

Study of municipal solid waste treatment using plasma gasification by application of Aspen Plus

Abstract Plasma gasification is a viable and efficient technique for handling solid waste, including hazardous waste, while also holding the potential for energy recovery. The objective of this study is to analyze the treatment of municipal solid waste (MSW) using plasma gasification by application of Aspen Plus software. An earlier proposed model was used to analyze the effect of employing different types of gasifying agents as plasma gas, on the composition of syngas produced. The lower heating value, cold gasification efficiency and carbon conversion efficiency were calculated and compared in each case. A sensitivity analysis study was also carried out to observe the effect of variation in plasma gas flow rate and feed flow rate on the composition of syngas generated. The capital, operational and maintenance costs of the process were determined using existing correlations. For a feed rate of 20,000 kg per hour of MSW, the highest yield of syngas (CO (33.48 %), and H2 (34.30 %) with the highest LHV (7.9 MJ/N-m3)) were produced when air was employed as plasma gas. The cold gas efficiency and the carbon conversion efficiency were at their peak when air was used as the gasifying agent. The sensitivity analysis revealed that as the flow rate of plasma gas increases syngas production decreases while the increase in MSW flow rate results in an increase in syngas production. Additionally, the cost analysis revealed that for a plasma gasification plant that can handle 500 tons of MSW per day, the estimated capital and annual operational and maintenance costs are $125,496,721 and $9,833,892 respectively.

Prediction of Welding Mode for the Effect of Plasma Gas Flow Rate on the Mechanical and Microstructural Characteristics of Plasma Arc Welded Titanium Alloy Joints

Prediction of Welding Mode for the Effect of Plasma Gas Flow Rate on the Mechanical and Microstructural Characteristics of Plasma Arc Welded Titanium Alloy Joints

PS-PVD thermal barrier coatings microstructure modulation and high-temperature erosion resistance study

Plasma spray-physical vapor deposition (PS-PVD) enables the modulation of both the microstructure and the performance of the coating by modulating the ratio of the three phases (gas, liquid, and solid) present in the jet. Considering the observed deficiency in the erosion resistance of PS-PVD coatings, the study explores improving high-temperature erosion resistance in PS-PVD thermal barrier coatings by adjusting Ar/He flow ratios. At a plasma gas flow rate of 90 SLPM, increasing the Ar/He ratio enhances nanohardness and elastic modulus. An Ar/He ratio of 2:1 provides erosion resistance comparable to standard APS coatings. Raising the plasma flow to 120 SLPM with the same Ar/He ratio forms a dense coating with low erosion rates. The study identifies a strong correlation between the hardness of the coating and erosion resistance. Lateral cracking from high-temperature and high-speed particle erosion is identified as the primary cause of failure.

Crucial effects of plasma gas on the weld and microstructural characteristics of plasma arc welded aero engine Ti6Al4V alloy joints

This study explores the influence of plasma gas flow rate (PGFR) on the defects, microstructure evolution and mechanical properties during plasma arc welding of Ti6Al4V titanium alloy thin sheets using microscopic analysis, spectroscopic analysis, tensile and microhardness tests. The variation in PGFR affects the welding arc in terms of its stability, pressure and constriction which results in transformation of arc from conduction mode to keyhole mode and changes in microstructure as well. All the other welding process parameters were kept constant except for PGFR which was varied to investigate its significance. Excess weld metal was observed under the weld bead is an attribute of keyhole formation. Macrographs exhibits increments in weld geometry measurements whereas weld defects such as lack of penetration and porosity decreased with increased PGFR. The microstructural examination showed a variety of phase formations that includes majorly with acicular α and Widmanstätten α morphologies. Tensile strength and hardness at the weld region of the welded joints increases with increase in PGFR. An oxygen rich brittle subsurface layer called α-case morphology was observed at the weld region of 1 L/min joint causes significant reduction in ductility.

Optimization of microstructure and properties of thick Al alloy welded joints for one-step formation by keyhole welding

To solve the problem of insufficient strength of thick aluminum alloy welded joints, this study introduces a pioneering technique known as variable-polarity plasma arc keyhole-tungsten inert gas cover hybrid welding (VPPA keyhole-TIG covering welding), which is designed for welding large-thickness aluminum alloys without any weld groove. Using 13-mm-thick 2319 aluminum alloy plates as experimental materials, plasma arc butt welding experiments were conducted by varying the plasma gas flow rate and application of cover welding. The research findings underscored that the use of cover welding, coupled with an increase in the plasma gas flow rate, markedly improved the overall performance of the weld. An average tensile strength of 299.0±4.0 MPa and an elongation rate of 4.5±0.3 % were achieved for the welded joint. A microscopic analysis revealed that the heightened plasma gas flow rate did not precipitate the θ' phase but instead resulted in undesired grain size enlargement, leading to reduced joint hardness. The secondary thermal cycle effect of covering welding played a pivotal role in facilitating the nucleation of needle-like θ' strengthening phases within the matrix, ranging in size from 50 to 150 nm. This phenomenon has emerged as a principal factor contributing to the substantial enhancement of the mechanical properties of welded joints.

Boosted hydrophobic properties of leather surfaces by atmospheric pressure plasma brush reactor

In this article, we demonstrate the application of an atmospheric pressure plasma brush (APPB) reactor for improving the hydrophobic properties of leather surfaces treated with organo-silane precursors for the first time. A comprehensive investigation was conducted to analyze the influence of various process parameters, including plasma access current, treatment duration, nozzle height, and gas flow rate, on the observed outcomes effects. The dispersion of active particles in the APPB was scrutinized using an Optical Emission Spectrometer (OES), while the underlying reaction mechanism was elucidated through the integration of Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), cross-sectional Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM) analysis. The findings unveiled that the resultant polysiloxane polymers bestowed a remarkable degree of hydrophobicity upon the leather, persisting steadfastly even following a 90-day aging period (WCA >140°). This APPB treatment combined with organosilane strategy may open a new design avenue for the development of surface treatments for intricate and temperature-sensitive substrates materials.

Field parameters investigation of CO2 splitting in atmospheric DBD plasma by multi-physics coupling simulation and emission spectroscopy measurements

CO2 dissociation in DBD plasma was thoroughly studied by combining dissociation experiments, multi-physics coupling simulation and in-situ emission spectroscopy measurements. Evolution of spatial–temporal distributions of key field parameters such as discharge mode, electron density (Ne), electron temperature (Te), intermediate concentration and reaction rates were analyzed in depth, to uncover the underlying reaction mechanism. The specific energy input (SEI) had a large impact on CO2 conversion and energy efficiency, and there was a trade-off between plasma power and gas flow rate. The highest CO2 conversion was achieved a maximum of 15.5% at SEI = 177 J·cm−3 in this work. Meanwhile, the spectrum shows that there was a large amount of CO2+, CO, O, and O2 in the plasma. In addition, we proposed and validated a reduced CO2 splitting plasma chemistry set to explore the field parameter and key reactin rates distributions. According to the multiphysics modelling, the discharge gap greatly affected the discharge form of DBD, which will subsequently influence CO2 splitting. In discharge gap > 1.75 mm formation of discharge channels remarkably decreased, and an over small discharge gap (δg < 1.25 mm) would restrain the electric field range, causing shorter motion path of charged particles and less free electrons, both of which hindered the conversion of CO2. A thinner dielectric layer can promote CO2 conversion, due to the reduction in breakdown field strength and increase of high-energy electrons. Electron impact reactions (e + CO2 → CO + O−, e− + CO2 → CO + O + e−), reactions of the excited CO2* (CO2 + CO2* → CO2 + CO + O, CO2*+O → CO + O2) mainly contributed to the CO2 dissociation.

Characterisation of thin α-Al2O3 tribo-coating deposited by low-power gas tunnel plasma spray

This study used a unique, low-power (2.8 kW) gas tunnel plasma spray and γ-Al2O3 feedstock powder to deposit a thin Al2O3 coating (<2 µm) on mild steel substrate. By optimising the plasma gas flow rate, powder feed rate, spraying time, and distance, a dense and homogeneous Al2O3 coating was obtained at a very high deposition rate (150 nm/s). During plasma coating, the high energy density plasma transforms the γ-Al2O3 powder into a highly crystalline α-Al2O3 as the predominant microstructure of the coating. The performance of the Al2O3 coating on mild steel was then evaluated preliminary using a linear sliding wear test against a chrome-steel ball, with the results indicating an 18–26% reduction in wear when compared to the uncoated substrate.

Optimization of interfacial bonding properties between thermoplastic liners and carbon fiber‐reinforced composites by atmospheric‐pressure plasma and failure mechanism study

AbstractWeak interfacial bonding properties between thermoplastic liners and carbon fiber‐reinforced composites (CFRP) can easily lead to debonding failure, which is a major challenge in development of type IV composite hydrogen storage vessels. We optimized Box–Behnken design atmospheric‐pressure plasma process parameters for maximizing interfacial bonding properties between thermoplastic liner (PA11 liner) and CFRP using Design‐Expert software. From various designs, plasma process parameters, including time (t), nozzle‐to‐specimen distance (d) and gas flow rate (r) of treatment were selected for optimization to assess the effects of their interactions on climbing drum peel (CDP), flatwise tensile (FWT) and asymmetric double cantilever beams (ADCB). The CDP strength, FWT strength and strain energy release rate (GADCB) of untreated samples were 4.2 N·mm/mm, 0.26 MPa and 87.2 J/m2, respectively. After the plasma treatment, optimum process parameters of t = 200 s, d = 12.5 mm, and r = 700 L/h were used to achieve 33.8 N·mm/mm, 2.97 MPa and 1008.4 J/m2, respectively, which were 8.0, 11.4 and 11.6 times that of untreated PA11 surface, respectively. This method has the potential for guiding thermoplastic liner surface treatment of type IV hydrogen storage vessels before winding.

Graphite-assisted laser ablation dielectric barrier discharge optical emission spectrometry for rapid detection of cadmium and zinc in cigarettes

A study of the capability of graphite-assisted laser ablation dielectric barrier discharge optical emission spectrometry (GALA-DBD-OES) for direct analysis of cadmium and zinc in cigarettes was undertaken. GALA-DBD-OES allowed direct sampling of cigarette samples in the condensed phase with the irradiation of a continuous wave infrared laser for subsequent atomization/excitation by a DBD plasma. The graphite in the sample matrix functioned as a laser energy converter and a thermal transmitter to improve the desorption efficiency of analytes. Under optimal conditions of the plasma gas flow rate, the discharge current and the proportion of graphite in the matrix, Cd and Zn were detected with limits of detection of 0.09 μg/g and 0.20 μg/g, respectively. Inter-day relative standard deviations of 4.5% for Cd at 45 μg/g and 2.6% for Zn at 30 μg/g indicate a good method repeatability. The accuracy of the present technique was verified by analyzing a certified reference material of cigarette. Quantitative results of Cd and Zn in commercial cigarettes allowed direct comparisons of cigarettes of different prices and geographical locations. All these features suggest the promising role of GALA-DBD-OES as a routine tool for real-time and on-site analysis of heavy metals in cigarettes.

An Experimental Study and a Numerical Modelling of Microdroplets Charged in a Helium Atmospheric Pressure Plasma Jet

A droplet passing through a low temperature plasma acquires a net negative charge, Q, and the droplet floating potential increases negatively until positive and negative charge fluxes are balanced. Subsequently electrons arrive at the droplet with a very low net electron energy. Low energy electrons (LEE) may play an important role in for example water chemistry, DNA damage (e.g. in radiotherapy) and electron-initiated nanomaterials synthesis [1]. However obtaining true LEE (< 5 eV) sources compatible with liquid water has not been possible to date. In a previous study, we have shown extremely fast and enhanced metal salt reactions within droplets and it is thought LEE reactions from charge on the droplets was the major contributor, in comparison to radiolysis and electron-beam studies [2]. Charging models of collisional high pressure plasmas have received little experimental validation, especially for particles in the size range (microns) where droplets can survive the plasma-induced evaporation. Measuring the small charge on fast moving droplets, however, in a high plasma RF noise environment presents very significant challenges. We present an experimental study of microdroplets charged in a helium atmospheric pressure plasma jet (APPJ) and, along with numerical modelling, determine the dependence of droplet charge, Q, on droplet diameter (D) and plasma conditions e.g. electron density, ne, and temperature, Te. Our measurements were carried out on aerosol droplet streams under various plasma conditions (power and flow) using a 4 mm plate collector. Without droplets, the collector assumed a mean positive potential. This is likely due to the effect of the upstream plasma potential which is estimated at ~12 V, assuming a Te of 2 eV. The background signal variation due to noise and other sources was ~250 mV. With the addition of droplets, the collector mean potential decreased due to the impact of the negative charge flux. At the maximum power, floating potential (VF) is a factor of ~100 greater at 3 mm collector distance compared to 15 mm. On the addition of droplets, the characteristics remain similar at 3 mm but at 15 mm, the potential remains positive until a much higher power. An image charge model [3] was used to obtain charge per droplet estimates from stream of droplets based on droplet rate and size distribution. High resolution imaging was used to obtain droplet statistics at the edge of the capillary. Here, the maximum droplet rate was ~ 5 x 104 s-1 [4]. The voltage – charge calibration factor, obtained from simulation, varies from 4.6 – 7.6 nV per electron, depending on velocity. The average value of charge per droplet can be obtained from the net potential obtained at different powers. The possible influence of the plasma gas flow (Q2) and liquid delivery rate (QL) on collector potential was explored and maximum charging capability was found to occur around a total gas flow of 3.5 slm and for lower QL values.

Influence of the atmospheric plasma spraying parameters on the coating structure and the deposition efficiency of silicon powder

Silicon coatings are usually produced by atmospheric plasma spraying (APS) and used as bond coats in environmental barrier coatings. The deposition efficiency (DE) of silicon powders is generally at a low level in APS processes. The reasons for the low DE values of silicon powders have not been sufficiently investigated in the literature. The aim of this study was to investigate in detail the influence of process parameters on the coating structure and deposition efficiency of a silicon powder processed with APS. A silicon powder with a size distribution of f = –53 + 15 µm was sprayed using a three-cathode plasma generator to produce coatings. The parameters such as plasma gas type, plasma gas flow rate and current intensity were varied widely. Accordingly, the power of the plasma generator increased from P = 19.4 to 51.3 kW, which allowed different melting and evaporation degrees of the powder. Particle velocities and temperatures were measured using a particle diagnostic method. The coatings were investigated in terms of their surfaces and structures using electron scanning microscopy (SEM). The porosities of the coatings were measured using an image analysis system. The deposition efficiency of the processed powder was determined. The results show that the used parameters led to high particle velocities in a range of about vp = 270–360 m/s. High particle temperatures of Tp = 2,650–3,390 °C were determined. The coating porosity varied from Φ = 2% to Φ = 15%. The porosity value of Φ = 2% is significantly lower than the values reported in the literature. The deposition efficiency of the powder changed from DE = 1.5% to DE = 28%. The value of DE = 28% is about 40% higher than the values reported in the literature. The strong grit-blasting effect was the main reason for the lowest DE value of DE = 1.5%. The strong evaporation effect was the main reason for the second lowest DE value of DE = 11.1%. Numerous melted particles and semi-melted particles splashed upon impact with the substrate, resulting in silicon melt loss. In addition, solid cores of semi-molten particles could bounce off, which also resulted in silicon loss. Splashing and bouncing were the main factors affecting DE for the parameter sets with DE values ranging from 18.7% to 28%.

Hardfacing of mild steel with wear-resistant Ni-based powders containing tungsten carbide particles using powder plasma transferred arc welding technology

Abstract This study explores the use of powder plasma transferred arc welding (PPTAW) as a surface layer deposition technology to form hardfaced coatings to improve upon the wear resistance of mild steel. Hardfaced layers were prepared using the PPTAW process with two different wear-resistant powders: PG 6503 (NiSiB + 60% WC) and PE 8214 (NiCrSiB + 45% WC). By varying the PPTAW process parameters of plasma gas flow rate (PGFR) and plasma arc current, hardfaced layers were prepared. Microscopic examinations, penetration tests, hardness tests, and abrasive wear resistance tests were carried out on the prepared samples. Hardfacings prepared with PG 6503 had a hardness of 46.3–48.3 HRC, while those prepared with PE 8214 had a hardness of 52.7–58.3 HRC. The microhardness of the matrix material was in the range of 573.3–893.0 HV, while that of the carbides was in the range of 2128.7–2436.3 HV. The abrasive wear resistance of the mild steel was improved after deposition of hardfaced layers by up to 5.7 times that of abrasion-resistant heat-treated steel, Hardox 400, having a nominal hardness of approximately 400 HV. The hardness and wear resistance were increased upon addition of Cr as an alloying element. Increasing the PGFR increased the hardness and wear resistance of the hardfacings, as well as increasing the number of surface cracks. Increasing the plasma transferred arc (PTA) current resulted in hardfacings with fewer cracks but lowered the wear resistance.

A Combined Thermal Spallation and Melting Technology by Plasma Jet for Deep and Hard Rock Reservoirs

Summary With the increasing demand for oil, gas, and geothermal resources worldwide, the efficient and economical construction of wells in deep and hard rocks has become very important, but conventional mechanical drilling technology cannot achieve this. In this paper, a new noncontact combined thermal spallation and melting technology by plasma jet is proposed. This technology can excavate rock materials by disintegrating brittle rocks into small fragments and melting plastic rock. Especially for hard granite, this method exhibits high rock removal efficiency with low specific energy. Furthermore, the plasma bit is not in contact with the rock, thus avoiding bit wear. A thermal spallation and melting experiment system is established, and laboratory tests are conducted. The influence of plasma current, plasma gas flow rate, confining pressure, and the types of rock-on-rock removal efficiency and specific energy are also researched. Results show that this novel technology can efficiently remove hard rocks, and hard granite is more likely to be removed under confining pressure than under the absence of confining pressure, indicating the feasibility of accessing geothermal, oil, and gas resources from deep and hard rock formations.

Powder Plasma Transferred Arc Welding of Ni-Si-B+60 wt%WC and Ni-Cr-Si-B+45 wt%WC for Surface Cladding of Structural Steel.

Increasing demand for sustainable approaches to mining and raw material extraction, has prompted the need to explore advanced methods of surface modification for structural steels used in the extractive industry. The technology of powder plasma transferred arc welding (PPTAW), was used in this study as a surface modification technique to improve upon the abrasive wear resistance of structural steel grade EN S355. PPTAW process parameters, namely, plasma transferred arc (PTA) current and plasma gas flow rate (PGFR), were varied, and the effects of the variation were studied and used as criteria for selecting optimum conditions for further studies and parametric reproducibility. Two metal matrix composite (MMC) powders were used in the process, having compositions of Ni-Si-B+60 wt%WC (PG) and Ni-Cr-Si-B+45 wt%WC (PE). Microstructural observation under a scanning electron microscope (SEM) revealed a dendritic, multi-directional microstructure consisting of partially dissolved primary tungsten carbide particles and secondary tungsten carbide precipitates within the MMC solid solution. The hardness of the surface layers was higher than that of a reference AR400 steel by more than 263 HV. Final surface layers obtained from the MMC powders had abrasive wear resistance up to 5.7 times that of abrasion-resistant reference AR400 steel. Alloying the MMC matrix with chromium increased the hardness by 29.4%. Under the same process conditions, MMC powder with 60 wt% WC reinforcement had better abrasive wear resistance by up to 45.8% more than the MMC powder with 45 wt% WC.

(Digital Presentation) Measurements of the Average Droplet Charge Using a Low Density Stream of Microdroplets in Atmospheric Pressure Plasma Jet

A droplet passing through a low temperature plasma acquires a net negative charge, Q, and the droplet floating potential increases negatively until positive and negative charge fluxes are balanced. Subsequently electrons arrive at the droplet with a very low net electron energy. Low energy electrons (LEE) may play an important role in for example water chemistry, DNA damage (e.g. in radiotherapy) and electron-initiated nanomaterials synthesis [1]. However obtaining true LEE (< 5 eV) sources compatible with liquid water has not been possible to date. In a previous study, we have shown extremely fast and enhanced metal salt reactions within droplets and it is thought LEE reactions from charge on the droplets was the major contributor, in comparison to radiolysis and electron-beam studies [2]. Charging models of collisional high pressure plasmas have received little experimental validation, especially for particles in the size range (microns) where droplets can survive the plasma-induced evaporation. Measuring the small charge on fast moving droplets, however, in a high plasma RF noise environment presents very significant challenges. We present an experimental study of microdroplets charged in a helium atmospheric pressure plasma jet (APPJ) and, along with numerical modelling, determine the dependence of droplet charge, Q, on droplet diameter (D) and plasma conditions e.g. electron density, ne, and temperature, Te. Our measurements were carried out on aerosol droplet streams under various plasma conditions (power and flow) using a 4 mm plate collector. Without droplets, the collector assumed a mean positive potential. This is likely due to the effect of the upstream plasma potential which is estimated at ~12 V, assuming a Te of 2 eV. The background signal variation due to noise and other sources was ~250 mV. With the addition of droplets, the collector mean potential decreased due to the impact of the negative charge flux. At the maximum power, floating potential (VF) is a factor of ~100 greater at 3 mm collector distance compared to 15 mm. On the addition of droplets, the characteristics remain similar at 3 mm but at 15 mm, the potential remains positive until a much higher power. An image charge model [3] was used to obtain charge per droplet estimates from stream of droplets based on droplet rate and size distribution. High resolution imaging was used to obtain droplet statistics at the edge of the capillary. Here, the maximum droplet rate was ~ 5 x 104 s-1 [[4]]. The voltage – charge calibration factor, obtained from simulation, varies from 4.6 – 7.6 nV per electron, depending on velocity. The average value of charge per droplet can be obtained from the net potential and is shown in Figure 1 for low and high powers. The possible influence of the plasma gas flow (Q2) and liquid delivery rate (QL) on collector potential was explored and maximum charging capability was found to occur around a total gas flow of 3.5 slm and for lower QL values. [1] Léon Sanche, ‘Cancer Treatment: Low-Energy Electron Therapy’, Nature Materials, 14.9 (2015), 861–63 https://doi.org/10.1038/nmat4333 [2] Paul Maguire et al., ‘Continuous In-Flight Synthesis for On-Demand Delivery of Ligand-Free Colloidal Gold Nanoparticles’, Nano Letters, 17.3 (2017), 1336–43 https://doi.org/10.1021/acs.nanolett.6b03440 [3] E. Borzabadi and A. G. Bailey, ‘The Measurement of Charge on Microscopic Particles’, Journal of Physics E: Scientific Instruments, 12.12 (1979), 1137–38 https://doi.org/10.1088/0022-3735/12/12/005 [4] Paul Maguire et al., ‘Controlled Microdroplet Transport in an Atmospheric Pressure Microplasma’, Applied Physics Letters, 106.22 (2015) https://doi.org/10.1063/1.4922034 Figure 1

The potential of transforming rice straw (Oryza sativa) and golden shower (Cassia fistula) seed waste into high-efficiency biochar by atmospheric pressure microwave plasma

Biochars were successfully produced from rice straw and golden shower seed wastes and used to obtain agricultural waste-derived and low-cost adsorbents to remove methylene blue (MB) dye pollutants. The biochars were prepared using atmospheric pressure microwave plasma in a nitrogen environment at three individual flow rates of 7, 9, and 11 L/min for 5 min via pyrolysis. After pyrolysis, RS biochar’s surface area and pore volume increased from 1.224 m2/g to 13.796 m2/g, 11.995 m2/g, 6.865 m2/g, and 0.006 cm3/g to 0.804 cm3/g, 0.168 cm3/g, 0.08 cm3/g, respectively, then GS increased from 11.874 m2/g to 40.423 m2/g, 45.731 m2/g, 73.067 m2/g, and 0.006 cm3/g to 0.181 cm3/g, 0.277 cm3/g, 4.227 cm3/g, respectively. FTIR results showed O–H stretching in hydroxyl groups, CO functional group, C-H bending of CH3, and C-H vibration aromatic compounds, essential for MB adsorption. The golden shower seed biochar activated by plasma gas flowrate 11 l/m (GS-11) and rice straw biochar activated by plasma gas flowrate 7 l/m (RS-7) had the highest adsorption capacity among all biochars, 344.82 mg/g, and 188.32 mg/g, respectively, which was 10.6 and 2.07 times higher than other golden shower and rice straw biochar from the previous research by much shorter pyrolysis duration of 24 and 48 times, respectively. In addition, both biochars had higher adsorption capacity than previous biochars from different biomass and pyrolysis methods even though they applied 5 times lower in dosage, 3 times higher on initial MB concentration, and 36–144 times shorter pyrolysis time. The equilibrium data fit well with the Langmuir model, and the adsorption kinetics followed pseudo-second-order kinetics. According to the current study, the atmospheric pressure microwave plasma can generate high-quality biochars quickly and be promoted as a recycling technology method. Then, the product biochars can reach high adsorption capacity with a low dosage, high initial MB concentration, low energy consumption, and no chemical added. Furthermore, the product can enhance the value of rice straw and golden shower seed waste, support a circular economy approach, reduce the waste released to the environment, and reduce air pollution generated.

Plasma-catalytic ammonia synthesis over BaTiO3 supported metal catalysts: Process optimization using response surface methodology

Non-thermal plasma (NTP) assisted ammonia (NH3) synthesis has been performed in a packed-bed dielectric barrier discharge (DBD) reactor. The presence of M/BaTiO3 (M = Fe, Co and Ni) catalysts in the DBD reactor significantly improved the NH3 concentration and energy efficiency with a sequence of Ni/BaTiO3 > Co/BaTiO3 > Fe/BaTiO3 > BaTiO3. Catalyst characterization, including N2 adsorption-desorption, X-ray diffraction analysis and temperature-programmed desorption of CO2, was performed to get insights into the relationships between the plasma-assisted NH3 synthesis process and M/BaTiO3 catalysts. The improved performance of plasma-assisted NH3 synthesis over Ni/BaTiO3 could be attributed to abundant basic sites and weaker metal-nitrogen (M-N) binding on its surfaces, which benefit the generation of NHx species and desorption of formed NH3. Response surface methodology (RSM) was used to assess the contribution of each independent process parameter and explore their mutual effects on the NH3 synthesis process systematically. The results of analysis of variance (AVONA) suggested that plasma discharge power and gas flow rate were the most significant factors in affecting the NH3 concentration and energy efficiency of the plasma-assisted NH3 synthesis process, respectively. Based on the proposed polynomial regression model, the maximum energy efficiency of 2.37 g kWh−1 was achieved at the predicted optimal operating conditions over Ni/BaTiO3.

Hardfacing of mild steel with wear-resistant Ni-based powders containing WC particles using PPTAW technology

This study explores the use of powder plasma transferred arc welding (PPTAW) as a surface layers deposition technology to form hardfaced coatings to improve upon the wear resistance of non-alloy structural steel. Hardfaced layers/coatings were prepared using the PPTAW process with two different wear-resistant powders: PG 6503 (NiSiB+60% WC) and PE 8214 (NiCrSiB+45% WC). By varying the PPTAW process parameters of plasma gas flow rate (PGFR) and plasma arc current, hardfaced layers were prepared. Microscopic examinations were carried out to ascertain information about the microstructure and surface characteristics of the prepared hardfaced layers. Penetration tests were performed to ascertain the number and depth of crack sites in the prepared samples by visual inspection. Hardness tests were also performed to determine the microhardness of the prepared hardfaced layers. Abrasive wear resistance tests were carried out on each prepared sample to determine their relative abrasive wear resistance relative to the reference material, abrasion resistant heat-treated steel having a nominal hardness of 400 HBW. The effects of the variations of PGFR and plasma arc current on the microstructure and mechanical properties of the coatings, and the wear mechanisms were discussed.

Surface modifications of PET in argon atmospheric pressure plasma: Gas flow rate effect

The correlation between plasma optical properties and the treated polyethylene terephthalate (PET) surface characteristics have been studied at various Ar flow rate. The rotational Trot and vibrational Tvib temperatures of APPJ were determined from SPS emission band. The pristine and plasma‐treated PET surfaces were characterized by several techniques including X‐ray photoelectrons spectroscopy (XPS), Raman spectroscopy, contact angle (CA), and atomic force microscope (AFM). The CA decreased rapidly in the flow rate range 1–3 L/min and weakly dependent as flow rate &gt; 3 L/min. XPS results showed that C 1s % of plasma‐treated PET surfaces decreases and has a minimum for samples treated at 3–4 L/min, while O 1s has a maximum at the same flow rate range. The carbon C 1s peak of pristine and plasma treated PET samples resolved into five subcomponents: C–C, C–O, C=O, O–C=O, and π–π bonds with variable percentage ratio accordance to the plasma gas flow rate. Raman data revealed a partial loss in the crystallinity of the treated PET samples and also confirm the incremental of C–O band at Ar flow rate of 3 L/min. AFM images showed that the surface roughness of treated PET films increases as Ar flow rate increases.