Processes In High-temperature Plasma Research Articles

Ultra-fast and low-cost electroactive biochar production for electroactive-constructed wetland applications: A circular concept for plant biomass utilization

This study demonstrates two sustainable processes to produce electroactive biochars and their application in electroactive constructed wetlands (CWs) for providing a circular route for biomass utilization and technology up-gradation for wastewater treatment along with electricity generation. With the use of Canna indica biomass generated in CWs operation, the current study produced two different biochars that differ in their physico-(electro)chemical properties related to the preparation method used. This study used plasma based processing to produce ultrafast biochar (PB) within a few minutes resulting in more crystalline biochar with high electrical conductivity compared to the amorphous biochar material produced by using the drum kiln processed biochar (KB) method. These biochars were used in developing electroactive constructed wetlands coupled with microbial fuel cells (CW-MFC) and were operated in batch mode together with commercial granular graphite (GG) substrate-based CW-MFC as control. PB was developed from high-temperature plasma processing in 6.0 min, whereas KB was prepared in bulk amount from semi-controlled combustion process in kiln method and took 3–4 days before final biochar preparation. Electrical conductivity (EC) of the biochar and GG material were found to be in the order of PB > GG > KB, indicating PB as a highly conductive material that assisted in microbial electron transfer. Accordingly, the highest current and power densities of 628 mA m-3 and 126 mW m-3, respectively, were also achieved with PB. The COD removal of 72.42 ± 2.61 %,72.32 ± 2.98 % and 59.91 ± 3.21 % was found in CW-MFC-GG, CW-MFC-KB and CW-MFC-PB microcosms, respectively.

Plasma Oscillations at Cathode Spot Region of Vacuum Arc

The model of ionization processes in high-temperature plasma of the near-cathode region of vacuum arc is given. The model is mathematically represented as a system of second-order nonlinear differential equations of drift diffusion for the electron density and mean energy of electrons. The solution of the presented system of equations was derived using the finite element method according to two coordinates in numerical form using the COMSOL Multiphysics program. It is shown that Langmuir waves, which result in a multiple-step ionization of metallic vapor, are generated in plasma owing to nonstationary processes.

Defective iron-oxide nanoparticles synthesised by high temperature plasma processing: a magnetic characterisation versus temperature

Magnetic properties and phase compositions of iron-oxide nanoparticles synthesised by a high temperature arc plasma route have been investigated by Mössbauer spectroscopy and high harmonic magnetic AC susceptibility measurements, and correlated with morphological and structural properties for different synthesis conditions. The Mössbauer spectra precisely determined the presence of different iron-oxide fractions in the investigated nanoparticles, while the high harmonic magnetic susceptibility measurements revealed the occurrence of metastable magnetic phases evolving in temperature and time. This study illustrates magnetic properties and dynamics of the magnetic configurations of iron-oxide nanoparticles grown by high temperature plasma, a process less explored so far but extremely useful for synthesising large numbers of nanoparticles for industrial applications.

Thermal plasma synthesis of Si/SiC nanoparticles from silicon and activated carbon powders

In this study, Si/SiC nanocomposites were synthesized by non-transferred arc thermal plasma processing of micron-sized SiC powder. First, micron-sized SiC was synthesized by solid-state method where waste silicon (Si) and activated carbon (C) powder were used as precursor materials. The effect of Si/C mole ratio and solid-state synthesis temperature on structural and phase formation of SiC was investigated. Diffraction pattern confirmed the formation of SiC at 1300°C. High C content was required for the synthesis of pure SiC as Si remained unreacted when Si/C mole ratio was below 1/1.5. Highly agglomerated micron-size (0.6–10µm) SiC particles were formed after solid-state synthesis. Thermal plasma processing of solid-state synthesized micron-sized SiC resulted into the formation of uniformly dispersed (20–60nm) Si/SiC nanoparticles. It was proposed that Si/SiC nanocomposites were formed due to partial decomposition of SiC during high temperature plasma processing. The formation of Si/SiC nanoparticles from micron-sized SiC was resulted from dissociation of grains from their grain boundary during plasma processing.

X-ray absorption spectroscopy characterization of iron-oxide nanoparticles synthesized by high temperature plasma processing

Iron-oxide nanoparticles have been synthesized by high temperature arc plasma route with different plasma currents and characterized for their structure, morphology and local atomic order. Fe K-edge x-ray absorption spectra reveal distinct local structure of the samples grown with different plasma currents. We have shown that the local disorder is higher for the higher plasma current grown samples that also have a larger average particle-size. The results provide useful information to control structural and morphological properties of nanoparticles grown by high temperature plasma synthesis process.

Energy Loss on High-Temperature Plasma Processing Waste Printed Circuit Boards

This paper estimates the electrical energy loss on high-temperature plasma processing waste printed circuit boards. Using three plasma torch powers in big output power (60W) and a plasma torch power in relatively small output power (30W), after 4.5 hours of high-temperature plasma incineration, 43 kilograms of waste printed circuit boards was successively fused at high temperature plasma incinerator. After calculating, the total electrical energy loss for four powers was about 1,070 kilowatts hours during sample incineration.

Microheterogeneous plasma from polymer aerogel and foam at powerful laser interaction

New results obtained in experiments on laser irradiation (I = 5×1013 W/cm2, λ = 1.054 micrometer) of low-density (10 mg/cm3) fibrous materials (agar and triacetate cellulose) are presented and discussed. The effect of low-density material microstructure of irradiated samples on physical processes in high-temperature plasma was investigated using a variety of plasma diagnostic methods.

Study on Temperature Distribution in Double Glow Discharge Zone

This paper deals with the temperature measuring of the glow discharge zone in double glow plasma surface alloying process. CCD technique was employed to get the temperature distribution profile. The results show that CCD method is a simple and effective non-contact temperature measuring technique, applicable in fields of low temperature and high temperature plasma processes.

Study of physical processes in laser-irradiated porous targets of different microstructure

New results obtained in experiments on laser irradiation (I = 10 14 W/cm 2 , λ = 1.055μm) of low-density (1-30 mg/cm 3 ) fibrous and foam-like materials are presented and discussed. The effect of low-density material microstructure of irradiated samples on physical processes in high-temperature plasma was investigated. Using a variety of complementary X-ray and optical methods the pronounced effect of material microstructure on the parameters and dynamics of produced plasma was found.

AFar Ultraviolet Spectroscopic ExplorerSurvey of Coronal Forbidden Lines in Late‐Type Stars

We present a survey of coronal forbidden lines detected in Far Ultraviolet Spectroscopic Explorer (FUSE) spectra of nearby stars. Two strong coronal features, Fe XVIII λ974 and Fe XIX λ1118, are observed in 10 of the 26 stars in our sample. Various other coronal forbidden lines, observed in solar flares, also were sought but not detected. The Fe XVIII feature, formed at log T = 6.8 K, appears to be free of blends, whereas the Fe XIX line can be corrupted by a C I multiplet. FUSE observations of these forbidden iron lines at spectral resolution λ/Δλ ~ 15,000 provides the opportunity to study dynamics of hot coronal plasmas. We find that the velocity centroid of the Fe XVIII feature deviates little from the stellar rest frame, confirming that the hot coronal plasma is confined. The observed line widths generally are consistent with thermal broadening at the high temperatures of formation and show little indication of additional turbulent broadening. The fastest rotating stars, 31 Com, α Aur Ab, and AB Dor, show evidence for excess broadening beyond the thermal component and the photospheric v sin i. The anomalously large widths in these fast-rotating targets may be evidence for enhanced rotational broadening, consistent with emission from coronal regions extending an additional ΔR ~ 0.4-1.3 R* above the stellar photosphere, or represent the turbulent broadening caused by flows along magnetic loop structures. For the stars in which Fe XVIII is detected, there is an excellent correlation between the observed Rontgensatellit (ROSAT) 0.2-2.0 keV soft X-ray flux and the coronal forbidden line flux. As a result, Fe XVIII is a powerful new diagnostic of coronal thermal conditions and dynamics that can be utilized to study high-temperature plasma processes in late-type stars. In particular, FUSE provides the opportunity to obtain observations of important transition region lines in the far-UV, as well as simultaneous measurements of soft X-ray coronal emission, using the Fe XVIII coronal forbidden line.

Preparation of Thick Functionally Graded Layers of Ceramics by Surface Modification of Tantalum and Titanium Using High Temperature Plasma Processing

Surfaces of metals, such as Ta and Ti, have been changed successfully to a new type of ceramic layers having the compositional gradient by means of the plasma processing at high temperature above 900°C. Surfaces of Ta and Ti were transformed to thick layers of ceramics, i.e. TiC, TiN, TaC or TaN components, respectively, by carburizing or nitriding. Resultantly, a Vicker’s hardness of each modified sample surface remarkably increased over 3000 kg/mm2. The density of carbides or nitrides in the modified layer and at the interface was measured to decrease with depth. The width of interface was wide about 7 \\micron, in the case of TiC . Additionally, the irradiation of 20 MeV-electron beam to samples as the pretreatment before the plasma processing was effective to increase the thickness of modified layer.

Simulation of MHD processes in high-temperature plasma

The paper analyzes a number of mathematical models and numerical codes developed for the study of magnetohydrodynamic (MHD) processes in high-temperature tokamak plasma. Various approaches are discussed to numerical solution of the nonlinear problems for systems of MHD equations arising in controlled thermonuclear fusion research.