G. Petraconi Filho

• Aeronautics Institute of Technology

Abstract In this work, a thermal plasma-based ablation test system was used to evaluate the ablative performance of the EPDM composite. The system produces a high enthalpy plasma jet generated by a plasma (DC) torch, operating at atmospheric pressure using compressed air as working gas, enabling the variation of the thermal flux concerned with the...

Thermal plasma-assisted processing is an effective process for the synthesis of gas (CO and H 2) and carbonaceous materials production from industrial waste. In this paper, a DC plasma torch designed with two vortices chambers has been developed, and its characteristics have been experimentally tested. The plasma torch operates with different plasm...

In this research naphthalene conversion in a non-equilibrium 2.45 GHz microwave (MW) plasma reformer was studied. These results show some improvement in conversion efficiency (over 94% vs. 80% under air plasma gas application) over work [5] in gliding arc for tar reforming.

This is an experimental study on the decolorization efficiency and the degradation of organic compounds from textile wastewater by the ozonation process in a batch system. The effects of different sample volumes of textile wastewater over time were investigated. The experiments were performed in a 1 L glass reactor with a magnetic stirrer and a bub...

Design of non-transferred DC electric arc plasma torches (EAPTs) operated with plasma gases containing alkane hydrocarbons, as a promising type of heaters for a number of technologies (thermal spraying, surface hardening, testing of thermal protection systems, etc.), requires taking into account the evaporation rate of surface cathode material (as...

The current production of carbon nanomaterials is facing the following two challenges: high selectivity toward specific chemical compositions or morphologies and their scalable production. Thermal plasma technology rises as an alternative method to produce carbonaceous materials. Thermal plasmas promote extreme process conditions which allow the co...

Coal tar pitch (CTP) processing for the production of clean fuel gas and carbon black (CB) was studied in plasma reactor equipped with a DC plasma torch. The composition of gas produced and energy costs were estimated theoretically for the CTP pyrolysis and gasification processes with two oxidant: oxygen and water vapor. We have found that the main...

Thermal plasma technology is a process that demonstrates high performance for the processing of different types of waste. This technology can also be applied in the treatment of radioactive wastes, which requires special care. Beyond that, volumetric reduction, inertization, as well as a cheap and efficient process are necessary. In this context, t...

Mercury and its compounds are very dangerous to environmental and human health. Methods to contain and/or limit its emission through the filters, gas cleaning systems, and alternative processes for purification of industrial residues are necessary. This study focused on mercury removal from diatomite sorbent samples–used as a filter in chemical ind...

Coal tar pitch (CTP) is a waste with a high carbon content produced on a large scale in the steel industries. Thermal plasma processing of waste with high carbon content has been promising for its potential of energy generation (combustible gases) and products of high added value (advanced carbonaceous materials). In this scenario, the present work...

The demand for the development of more efficient, low emission, and high-performance aircraft have required new methods to obtain lighter materials, with higher temperature resistance and chemical stability. For these purposes, Environmental Barrier Coatings (EBC) are largely studied. EBC's are commonly obtained through Atmospheric Plasma Spray, wh...

A significant, valuable percentage of waste stream produced on a large scale in the industries, consists of high carbon content materials. Currently, the lack of cost-effective recycling technology made the thermal plasma treatment a viable means for recycling these materials. Beyond that, the thermal plasma can convert the residues into nanostruct...

Dielectric Barrier Discharge (DBD) can be used to produce a large volume of non-thermal plasma at atmospheric pressure. Such plasmas are sources of highly reactive species (radicals, ozone, atoms, ions and excited molecules). Due to its characteristics, the DBD plasma can be applied for the pretreatment of lignocellulosic materials, in order to ext...

The purpose of the current study was to investigate the effect of ozone exposure on the process of water uptake and germination of lentil (Lens culinaris) seeds. For this, a commercial ozone generator that provides a concentration of 1 g/m 3 generated from atmospheric air was used. In the experiments 10 lentil seeds were used per treatment carried...

Nuclear reactors, hospitals, industries and research institutes generate considerable amounts of radioactive waste every day. To dispose this waste in a safe and cost-effective manner, it must be treated by immobilising the radionuclides and, for better stocking capacity, it must be volumetrically reduced as much as possible. To this end, plasma te...

Os rejeitos radioativos provenientes de reatores nucleares, hospitais, indústrias e institutos de pesquisa são gerados diariamente com uma quantidade considerável. Para armazenar esses rejeitos radioativos de forma eficaz, com segurança e controle, eles devem ser transformados em produtos físicos e químicos adequados para a imobilização de radionuc...

Candida spp are present in 70%–90% of invasive infections and non-thermal plasmas operated at atmospheric pressure have been gaining attention as a new antimicrobial strategy for medical devices. This work presents studies on the inactivation efficacy of biofilms of Candida albicans grown in polyurethane (PU), main constituent of central venous cat...

Hollow cathode discharge (HCD) is widely used in material processing and plasma emission spectroscopy due to several advantages over other plasma sources. Basically, the HCD consists of a cathode with a hollow structure (cavity, hole, or parallel faces) and an anode of arbitrary shape. In this investigation, experimental studies on low-pressure pla...

The plasma torch design affects the particle-plasma interaction, in-flight properties and the coating microstructure. When spraying metallic powders, the in-flight oxidation as well as the particle velocity and temperature determine the mechanical, corrosion and oxidation properties, which have a major impact on the in-service degradation of bond c...

The radioactive waste arising from nuclear reactors, hospitals, industry, and research institutes are generated daily with a considerable amount. To final dispose of these radioactive waste safely and cost-effectively, they must be transformed into physical and chemical compounds suitable for radionuclides immobilization with maximum volume and exh...

Carbon/carbon (C/C) composites are widely used in structural components, particularly in the aerospace and aeronautics sectors. However, the application of C/C composites is limited by low oxidation resistance at high temperatures. In order to overcome this problem, graded SiO2/SiC coatings were deposited on C/C composites by a high-velocity soluti...

Results of experimental investigations of a new-type generator of an arc water plasma, having a high thermal efficiency close to 100%, are presented. This generator represents a system comprising a vortex arc plasma generator, in which an electric arc is stabilized by water vapor and a straight-through-flow tubular electric steam generator. Such a...

Plasma spray is a versatile technology used for production of environmental and thermal barrier coatings, mainly in the aerospace, gas turbine, and automotive industries, with potential application in the renewable energy industry. New plasma spray technologies have been developed recently to produce high-quality coatings as an alternative to the c...

The motion of particles axially injected into the plasma spray process has been studied using a one-dimensional model. The effect of the initial particle velocity and particle diameter on the final particle velocity and temperature was evaluated. The aim of the work is to optimize the spraying process by defining the favorable particle injection ve...

This work presents a plasma torch able to operate at supersonic regime with axial injection of feedstock. In contrast to commonly used linear scheme, the principal axis of the plasma torch is perpendicular to feedstock injection direction, which is aligned with coming out plasma jet. The plasma torch has slightly ascending current voltage character...

In this research a new approach of improvement of syngas combustible properties, which is used as a fuel in a spark ignition engine, is presented. The main purpose of the research is providing of high level of electrical autonomy of small village house through enhancement power of spark ignition engine, driving electricity generator, and decreasing...

Thermal plasma gasification technologies are the last two decades in commercialization stage for industrial wastes as, municipal solid waste (MSW), ash residues, low grade coals and biomass. These can be used to produce a high calorific syngas (HHV ≥ 20 MJ/kg) at low operating cost. Consequently, the potential market of the plants for Waste-to-Ener...

Thermal plasma gasification technologies are the last two decades in commercialization stage for industrial wastes as, municipal solid waste (MSW), ash residues, low grade coals and biomass. These can be used to produce a high calorific syngas (HHV ≥ 20 MJ/kg) at low operating cost. Consequently, the potential market of the plants for Waste-to-Ener...

This paper presents the analysis of ecological and economical availability for using syngas from gasification of biomass waste or other solid fuels into diesel with ICE-based combined cycle (CC). The new approach is proposed to improve the ecological efficiency of the CC system and decrease the cost of electricity which can be produced with electri...

Comparisons of heating tests at atmospheric pressure and low pressure by using a thermal plasma torch were performed. A constant heat flux on the sample surface was applied in the study of the oxidation mechanism of C/C-SiC composite, used in thermal protection systems. The SEM and EDS analysis show an intensive glassification at the surface, which...

In this paper, the anisotropic model for the dc electric arc was expanded, which allows the obtaining of power function generalized expressions for calculating the characteristics of the electric discharge into the dc plasma torch channel without using a large number of experimental studies. The model is based on the power law approximation of temp...

This chapter presents the chemistry studies of low-pressure electrical discharges generated with argon gas. This noble gas is widely used in gas-discharge lamps, as sputtering gas for deposition and/or etching processes, arc welding, among others. Especially, in the semiconductor industry, this gas is present in most of the processing steps of a ch...

In this paper, we report on the existence of two electron temperature populations in the low pressure expanding dc plasma jet through the investigation of the spatial evolution of EEDF measured by a single Langmuir probe system. It was observed that for argon the plasma jet is Maxwellian type in all discharge axes. However, when an electronegative...

In this work the chemistry of CF4 capacitive plasma is studied. For this, experimental measurements were made by mass spectrometry technique which allowed the analysis of neutral species generated during the fragmentation of the source gas by the electrical gas discharge. Additionally, we use global model simulations in order to complement the expe...

This chapter presents the investigations about the characteristics of the cathode sheath generated in an argon low-pressure hollow cathode discharge (HCD). The theoretical model for the cathode sheath is considered to be non-collisional. Secondary electrons emitted from the cathode surface are taken into account in the discharge model and their inf...

In this work an oxygen asymmetric capacitive radio frequency discharge was investigated with numerical global model and Langmuir Probe to evaluate the behavior of the electron density (ne) and the electron temperature (Te) as a function of input power and gas pressure. The experimental Langmuir probe measurements show that Te increases for pressure...

In this work is proposed the automation of a gas injection (mass flow) system in order to generate timemultiplex SF 6/CH4 radiofrequency plasma applied for silicon (Si) etching process. The control of the gas injection system is important in order to better control the process anisotropy, i.e., the high-aspect-ratio of mask pattern transfer to subs...

In this work, a theoretical model for the cathode sheath using experimental data of a low pressure hollow cathode discharge (HCD) is derived considering it to be non-collisional. Secondary electrons emitted from the cathode surface are taken into account on the discharge model and their influence on the theoretical sheath potential profile is inves...

In this work, the surface of silicon etched by sulphur hexafluoride (SF 6) and carbon tetrafluoride (CF 4) plasma jet, pure or mixed with oxygen gas (O 2), was investigated by scanning electron microscope (SEM), optical perfilometry and x-ray photoelectron spectroscopy (XPS). Through these techniques it was possible to investigate the etching rate,...

A volume-averaged global model for inductively coupled carbon tetrafluoride (CF4) plasma was used to study the role of the different processes of production and loss of atomic fluorine on the two different ways to vary the gas pressure: under variable or constant gas flow rate. The results obtained by plasma modeling confirm the behavior of atomic...

The structure of molecular oxygen discharge generated by a capacitively coupled reactor was experimentally investigated using a Langmuir probe and the results were compared to the Particle-in-Cell (PIC) simulation. The electron energy distribution functions (EEDF) were measured for a pressure range of 10 to 100 mTorr, keeping the power injected int...

In this work, electrical and optical studies of SF6 and SF6/O2 plasmas generated in a hollow cathode reactive ion etching reactor were performed using the Langmuir probe and optical emission spectroscopy techniques, respectively. We carried out an investigation aimed at understanding the influence of radio-frequency power, gas pressure and O2 gas m...

A formula for quick calculation of thermal characteristics of materials used for thermal protection is proposed. The mode of heating of the sample external surface (subjected to thermal exposure) is approximated by two regions, which differ by corresponding boundary conditions on the heating surface: T_f=cτ (linear growing with time) and T_f=const...

Important questions on a plasma etching system arises from gas flow issues. This article represents a first step to obtain a thorough understanding of the gas behaviour on a Hollow Cathode Plasma Etching system. According to this objective, the pressure performance within a Plasma chamber, and on a remote positions of the gas feed line were analyse...

In this work the applicability of a low pressure sulphur hexafluoride (SF6) plasma jet for silicon etching was investigated by optical emission spectroscopy (OES) technique. Through the use of actinometry method the density of atomic fluorine was obtained as a function of process parameters namely radio-frequency (rf) power, axial magnetic field, S...

The results of experimental investigations of electrical and thermal characteristics of a vortex plasma torch with a reverse vortex, generated in a hollow blind-end electrode, are presented. It is shown that the reverse vortex essentially improves the performance of the plasma torch and contributes to an increase in the thermal efficiency and entha...

An experimental Plasma Wind Tunnel was developed at ITA (Technological Institute of Aeronautics). The setup allows simulating the hypersonic flight conditions at high altitudes using a plasma torch setup. This paper discus the particularity of the experimental setup and the methodology used to the Mach number measure in the plasma jet. The results...

This paper describes the effect of the SF6 gas residence time on the morphology of silicon (100) samples etched in a reactive ion etching system. Profilometry and atomic force microscopy techniques were used to characterize the etching process focusing attention on the evolution of the surface morphology. Under the condition of variable pressure an...

Amorphous and crystalline AlN thin films were deposited on Si (100) substrates by off-axis hollow cathode magnetron technique. The evolution of the crystalline orientation and the morphology of AlN thin films have been investigated depending on the nitrogen concentration. It has been demonstrated by using a combination of mass spectrometry, X-ray d...

A new dc hollow cathode plasma source has been assembled whith a conventional planar magnetron cathode used together with another plane cathode plate to form a hollow cathode cavity. The system comprises two cathode plates of aluminium separated by a distance d, one of them acting as target of the magnetron cathode, the other being an ordinary plat...

Sized PAN-based carbon fibers were treated with hydrochloric and nitric acids, as well as argon and oxygen cold plasmas, and the changes on their surfaces evaluated. The physicochemical properties and morphological changes were investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS),...

The electrical breakdown has been investigated for low-pressure argon and nitrogen discharges under the influ-ence of an external longitudinal magnetic field. Plane-parallel aluminum electrodes (5 cm diameter) separated by a variable distance d (4.0 cm < d < 11.0 cm) were sustained with a dc voltage (0 < V < 1 kV). A Helmholtz coil was used to prod...

Hollow cathode discharges (HCD) are capable of generating dense plasmas and have been used for development of high-rate, low-pressure, high-efficiency processing machines. The geometric feature of a HCD promotes oscillations of hot electrons inside the cathode, thereby enhancing ionization, ion bombardment of inner walls and other subsequent proces...

A theoretical and experimental study was developed about the applicability of a double probe system consisting of two directional Langmuir probes, both probes being located separately in a plasma column. The current- voltage characteristic of the double probe was obtained considering a plasma with a drifting maxwellian electron velocity distributio...

Experimental studies of the formation of electrostatic double layers (DLs) and electron-holes (e-holes) are reported. The measurements were performed in the positive column of a mercury arc discharge operating in the low-pressure range of (2.0–14.0) × 10−2 Pa with current density in the range of (3.0–8.0) × 103 A m−2. Stable and unstable modes of t...

The present research has been conducted aiming the study of mechanical characteristic improvement of Ti6Al4V alloy surface. The proposed process is based on an ion nitriding method performed in a low intensity plasma jet reactor. An objective of the study is to enlarge the applicability of this alloy in several industrial areas, mainly foccusing th...

The linear calorimetric probe is developed for the arc jet heat flux measurements. Method de Abel's inversion matrix is engaged for obtain the heat flux density distribution. Heat flux density from plasma jet to catalytically calorimetric probe is investigated for efficient study of the efficiency of thermal protection system (TPS) material used fo...

Having in mind the plasma assisted carbon material activation process development, samples of carbonized macadamia nut shells were treated in oxygen plasma. The carbonization process was performed at 800 o C in nitrogen atmosphere, and a titanium electrode Hollow Cathode Reactor (HCR) coupled with mass spectrometry monitoring system was set up for...

In this work the optical emission spectroscopy and neutral mass spectrometry techniques are used to monitor pure SF 6 and CF 4 plasmas and/or its mixture or mixed with O 2 . These plasmas were generated in a radiofrequency Hollow Cathode Reactive Ion Etching reactor at the following constant experimental condition: gas pressure at 26 mTorr, flow at...