Air Plasma Torch Research Articles

Numeric Model for Assessment of Naphthalene Conversion through Ionization Reactions in a Microwave Air Plasma Torch

In this study, the authors have presented a numeric model (NM) for application to naphthalene (C10H8) conversion via ionization reaction in a microwave air plasma torch. The NM has included a pressure-independent enhanced electron energy distribution function (EEDF) and cross-section calculation, enhanced by a new formula of phase shift determination. Based on the validated NM, electron density ne and O2+, O–, C10H8, N2, and O2 particles densities were calculated, as well as the conversion rate of C10H8 molecules was predicted. The predicted results showed that the ionization impact on C10H8 molecules conversion has not exceeded 0.81 × 10–10%. Based on the calculated collision cross-section of each species (O2, N2, and C10H8) of carrier gas, the authors suggested using cubic polynomial approximations of the cross-section curves with R-Square (COD) parameter R2 = 99%. MW power increasing in the range 1.75–20 kW has raised the electron density in the range (0.5–4.5) × 1012 m–3. The maximal effect of electro...

Effects of O 2 gases addition on enhanced lithium ion intercalation and conduction of flexible-transparent-lithiated tantalum oxide thin films synthesized by an atmospheric pressure plasma jet

Abstract Flexible-transparent-lithiated-lithium tantalum oxide (Li x TaO y C z ) films deposited onto 40 Ω/□ flexible polyethylene terephthalate/indium tin oxide substrates by low temperature plasma polymerization with an atmospheric pressure plasma jet (APPJ) at various flow rates oxygen gases are investigated. Precursors [lithium tert -butoxide, (CH 3 ) 3 COLi] and [tantalum ethoxide, Ta(OC 2 H 5 ) 5 ] 2 ] vapors are carried by argon gas, mixed by oxygen gas and injected into air plasma torch for fast synthesis of Li x TaO y C z films by short durations of the substrates, 33–37 s, exposed in the plasmas. The flexible-transparent Li x TaO y C z films possess the notable Li + ion intercalation and conduction performance for 200 cycles of reversible Li + ion intercalation and de-intercalation in a 1 M LiClO 4 -propylene carbonate electrolyte by switching measurements with a potential sweep from − 1.25 V to 1.25 V at a scan rate of 50 mV/s, even after being bent 360° around a 2.5 cm diameter rod for 1000 cycles. The Li + ionic diffusion coefficient and conductivity are respectively of up to 1.2 × 10 − 10 cm 2 /s and 1 × 10 − 8 S/cm for Li x TaO y C z films synthesized using an APPJ with a certain O 2 gases addition of 9 sccm.

Impact of plasma processed air (PPA) on quality parameters of fresh produce

The ubiquitous presence of spoilage microorganisms and sporadic occurrences of human pathogens on heat-sensitive fresh produce are serious economic and health issues. A potential solution for the gentle sanitation of fresh fruit and vegetables is the application of atmospheric pressure plasmas. In this study, a microwave-driven air plasma torch was used for indirect treatment of whole pieces of fruits and vegetables within a remote exposure chamber for up to 10min. The impact of this technique on the external quality of apples, cucumbers, tomatoes and carrots, and its antimicrobial efficacy on indigenous and inoculated microorganisms were examined. After 5min of plasma application, total mesophilic counts were reduced by 3.4±0.4, 1.2±0.5, 5.2±0.5, and 3.3±0.5 log cycles on apples, cucumbers, carrots and tomatoes, respectively. After 10min, counts of artificially inoculated Escherichia coli were reduced by 4.6±2.0 and 6.0±0.8 log cycles on apples and carrots, respectively. Significant effects of plasma treatment were found on color of tomatoes and carrots, and on chlorophyll fluorescence parameters of cucumbers, whereas elasticity remained almost unaffected in all produce. The plasma processed air treatment proved to be suitable for apples as the most stable product. For more susceptible produces such as carrots, however, plasma induced effects on the surface. Hence, in such cases, the application of indirect plasma needs to be specifically adapted to ensure product quality and safety.

Electrochromic Ni–Fe oxide thin films synthesized by an atmospheric pressure plasma jet for flexible electrochromic application

Flexible-electrochromic organo-nickel-iron oxide (NiFexOyCz) films deposited onto flexible polyethylene terephthalate (PET)/indium tin oxide (ITO) substrates using atmospheric-pressure plasma-enhanced chemical vapor deposition with an atmospheric pressure plasma jet under various flow rates of oxygen gases are investigated. Precursors [nickelocence, Ni(C5H5)2] and [ferrocence, Fe(C5H5)2] vapors are carried by argon gas, mixed by oxygen gas and injected into air plasma torch for a rapid synthesis of NiFexOyCz films by a short duration of the substrate, 32s, in the plasmas. Uniform light modulation on PET/ITO/NiFexOyCz is produced while the moving PET/ITO substrate is exposed to plasma torch at room temperature (~23°C) and atmospheric pressure. Light modulation with up to a 43.2% transmittance variation at a wavelength of 708nm even after 200cycles of Li+ intercalation and de-intercalation in a 1M LiClO4-propylene carbonate electrolyte is accomplished.

Assessment of atmospheric plasma treatment cleaning effect on steel surfaces

The present study deals with the ability of an atmospheric pressure air plasma torch (APPT) treatment to remove lubricant pollutants coming from machining processes on steel surfaces. This effect has been characterized by contact angle measurements, gravimetric analysis and reflection absorption infrared reflectance spectroscopy (RAIR-FTIR). Attending to the initial results of the investigation, further surface analysis has been done by means of X-ray photoelectron spectroscopy (XPS). In order to define the benefits of cleaning for adhesive bonding processes, pull-off tests were performed on all the coupons. Experimental data show the effectiveness of APPT to achieve not only a high rate of surface lubricant layer elimination, thus cleaning the metal samples by means of a solvent free and fast treatment, but also a remarkable improvement on the substrate adhesive bonding strength.

Novel three-phase steam–air plasma torch for gasification of high-caloric waste

Research results are presented for an AC electric arc that burns a mixture of steam and air in a three-phase high-voltage plasma torch and can be implemented to produce plasma for plastic waste gasification. The dependences of electric parameters on the ratio of the steam to air mass flows (H2O/air ∼1–6) at an approximately constant total mass flow of the plasma-forming gas are obtained during several experiments. During the experiments, the arc parameters were as follows: voltage drop of 1.0–1.8kV, current of ∼28.5A and power of ∼52–86kW. The thermal efficiency of the plasma torch was ∼94–95%. CCD cameras operating at 4000fps were used to determine the average discharge length of ∼798mm. Photography with a high shutter speed (1/8000s) was used to determine the average arc diameter (∼4.47mm). Arc temperatures were calculated (10,000–11,500K) using the thermodynamic equilibrium approach. Experimental results indicate that increases in the steam content of the steam–air plasma lead to a reduction of the arc’s temperature and electrical conductivity. Using an equilibrium approach, the main parameters of plasma gasification were estimated: syngas yield (3.62–3.48m3/kg), composition (H2 – 55.5–62.5, CO – 32.8–34.1vol.%) and energy consumption (11.0–12.3MJ/kg).

Degradation behavior of 4D carbon/carbon composites under supersonic oxidative air plasma

Abstract Four-directional (4D) carbon/carbon (C/C) composites were prepared using an intermediate modulus carbon fiber as the reinforcement and two kinds of coal tar pitches as the source for carbon matrix. After repeated high-pressure impregnation, carbonization and graphitization at 2250 °C, a high density of 1.86 g/cm3 was achieved. A plasma arc jet was applied to the composite for studying its degradation behavior. The oxidative supersonic jet was generated by an air plasma torch. For studying various stages of degradation during a long exposure time of 90-s, the intermittent ablation and erosion rates were measured for the C/C composite at time intervals of 70, 50 and 30 s. The mass ablation rate was increased rapidly with the time, while the erosion showed a bilinear response with a decreasing trend. The results were discussed based on the machined and eroded surfaces of the test samples. For studying the residual ablative performance, the samples of 30–70 s were then re-ablated and re-eroded in steps of 20-s so that all the samples are equal in total exposure time. The samples showed decreasing trends in the re-ablation and re-erosion rates and ultimately became zero for the last 20-s exposure time. There was a progressive increase in the char layer on the samples with the re-ablation. The porous char layer protected the samples against chemical and mechanical actions of the plasma stream. Compressive tests were carried out, and the decrease in the modulus was due to the presence of microcracks resulting from the mismatch in thermal expansion of the fiber and the matrix. The SEM micrographs reveal that inter- and intra-bundle cracks tend to grow through the weaker matrix pockets.

Atmospheric-pressure plasma-enhanced chemical vapor deposition of electrochromic organonickel oxide thin films with an atmospheric pressure plasma jet

Deposition of electrochromic organonickel oxide (NiOxCy) films onto glass/indium tin oxide (ITO) substrates using atmospheric-pressure plasma-enhanced chemical vapor deposition with an atmospheric pressure plasma jet under various precursor injection angles is investigated. A precursor [nickelocene, Ni(C5H5)2] vapor, carried by argon gas and mixed with oxygen gas, is injected into an air plasma torch for the deposition of NiOxCy films by a short exposure of the substrate, 20s, in the plasma. Uniform light modulation on glass/ITO/NiOxCy is produced while the moving glass/ITO substrate is exposed to the plasma torch at room temperature (~23°C) and under atmospheric pressure. Light modulation with up to a 40.9% transmittance variation at a wavelength of 513.9nm under Li+ intercalation and de-intercalation in a 1M LiClO4–propylene carbonate electrolyte is achieved.

Atmospheric pressure plasma jet-synthesized electrochromic organomolybdenum oxide thin films for flexible electrochromic devices

An investigation is conducted into fast synthesis of electrochromic organomolybdenum oxide (MoOxCy) thin films onto 40Ω/□ flexible polyethylene terephthalate/indium tin oxide substrates via atmospheric pressure plasma jet. A precursor [molybdenum carbonyl, Mo(CO)6] vapor, carried by argon gas, is injected into air plasma torch to synthesize MoOxCy films for offering extraordinary electrochromic performance. Only low driving voltages from −1V to 1V are needed to offer reversible Li+ ion intercalation and deintercalation in a 1M LiClO4-propylene carbonate electrolyte. Light modulation with transmittance variation of up to 61%, optical density change of 0.54 and coloration efficiency of 37.5cm2/C at a wavelength of 550nm after 200cycles of cyclic voltammetry switching measurements is achieved.

Hydrogen-rich syngas production through coal and charcoal gasification using microwave steam and air plasma torch

In the present study, microwave plasma gasification of two kinds of coal and one kind of charcoal was performed with various O2/fuel ratios of 0–0.544. Plasma-forming gases used under 5 kW microwave plasma power were steam and air. The changes in the syngas composition and gasification efficiency in relation to the location of the coal supply to the reactor were also compared. As the O2/fuel ratio was increased, the H2 and CH4 contents in the syngas decreased, and CO and CO2 increased. When steam plasma was used to gasify the fuel with the O2/fuel ratio being zero, it was possible to produce syngas with a high content of hydrogen in excess of 60% with an H2/CO ratio greater than 3. Depending on the O2/fuel ratio, the composition of the syngas varied widely, and the H2/CO ratio necessary for using the syngas to produce synthetic fuel could be adjusted by changing the O2/fuel ratio alone. Carbon conversion increased as the O2/fuel ratio was increased, and cold gas efficiency was maximized when the O2/fuel ratio was 0.272. Charcoal with high carbon and fixed carbon content had a lower carbon conversion and cold gas efficiency than the coals used in this study.

Development of improved polypropylene adhesive bonding by abrasion and atmospheric plasma surface modifications

The present work deals with the problematic adhesive bonding of substrates with low surface energy. Different approaches have been explored with the aim of creating adequate adhesive joints based on polyolefinic substrate and polyurethane adhesive. The selected material under study was polypropylene (PP) as adherend, and a commercial Sikaflex ®-252 polyurethane one component based structural adhesive (PU) as joint fluid. Among the diverse pre-treatments typically used to prepare surfaces prior to bonding, mechanical abrasion with emery paper of 80 grain size, the use of a chemical primer and atmospheric pressure air plasma torch (APPT) were the selected methods to facilitate the application of the PU by means of surface energy enhancement as well as to create a correct mechanical interlocking of the adherent–adhesive interface. Changes in the wettability of the polymer were evaluated by contact angle measurements following the UNE EN 828:2010. Surface energy was calculated both in terms of Owens approximation and acid–base considerations, leading to the possibility of determining a relationship between changes in surface energy and adhesion. Changes in the chemical composition of the surface were studied by X-ray photoelectron spectroscopy (XPS), electron diffraction X-Ray (EDX) probe and attenuated total multiple reflection mode infrared spectroscopy (ATR-FTIR). Morphological modifications were investigated with scanning electron microscopy (SEM). Variations in the strength of single-lap PP–PP joints with the treatments were evaluated by lap shear tests following the UNE-EN 1465:2008 standard. Experimental evidence supports the superiority of the APPT treatment to increase wettability and adhesion of polyolefinic surfaces, especially when combined with the use of a primer.

Large-Scale Plasma Waste Gasification

The plasma resource recovery system is a two-stage plasma gasification and vitrification system used to process municipal solid waste. A transferred arc discharge is used to generate syngas from the waste, and an air plasma torch is used to polish the gasification products. Online syngas monitoring can be employed to compensate for variations in waste feed, thus maintaining both the syngas composition (quality) and production rate.

Two-Dimensional Distribution of Atomic-Oxygen Multiplet Radiation Produced by an Air-Plasma Torch

A pen-size low-temperature air-plasma torch is designed for dental applications. A narrow-band-filtered charge-coupled-device camera is used to record the 2-D distribution of the intensities of 777.4-nm emissions from the 5P state of atomic oxygen produced in the plasma effluent of the torch.

Approaches to Poly(Tetrafluoroethylene) Adhesive Bonding

In this work, we present an approach to achieve improved adhesive bonding with a poly(tetrafluoroethylene) (PTFE) substrate. Surfaces were modified by abrasion, atmospheric air plasma torch (APPT) treatment, and by immersion in basic (NaOH) and strongly acidic/oxidizing (HNO3/KMnO4) solutions. The wetting properties of the polymer were studied in terms of surface energy, and adhesion tests were carried out using polyurethane, acrylic, and epoxy adhesives. The surface characterisation included surface energy calculation through contact angle measurements, infrared spectroscopy (FTIR-ATR), scanning electron microscopy (SEM), and X-ray electron diffraction (EDX). Adhesion was evaluated by pull-off tests following the UNE EN-24624 standard. Experiments revealed that both oxidation and plasma treatment enhanced surface energy, defluorination, and the creation of a rougher PTFE surface, resulting in adhesion. Simple oxidation and its combination with plasma treatments yielded the higher tensile strength results, with epoxy as the most suitable adhesive among those studied. Samples presented adhesive or mixed type failure modes.

High‐Rate Deposition of Electrochromic Organotungsten Oxide Thin Films for Flexible Electrochromic Devices by Atmospheric Pressure Plasma Jet: The Effect of Substrate Distance

AbstractHigh‐rate deposition of electrochromic organotungsten oxide (WOxCy) films onto flexible PET (polyethylene terephthalate)/ITO (indium tin oxide) substrates by atmospheric pressure‐plasma enhanced chemical vapor deposition (AP‐PECVD) with atmospheric pressure plasma jet (APPJ) under various substrate distances is investigated. A precursor (tungsten carbonyl, W(CO)6, TC) vapor, carried by argon gas, is injected into air plasma torch for the synthesis of WOxCy films. Uniform light modulation up to 1 cm wide on PET/ITO/WOxCy is produced, while the moving PET/ITO substrate is exposed to a 0.3 cm diameter plasma torch at room temperature (≈23 °C) and atmospheric pressure. The porous APPJ‐synthesized WOxCy films result in fast responses using potential steps for coloration of 11.5 s at −1V and bleaching of 7.2 s at +1V, respectively. APPJ‐synthesized WOxCy films offer noteworthy electrochromic performance in light modulation with up to 73.0% of transmittance variation, optical density change of 0.72 and coloration efficiency of 67.7 cm2 · C−1 at a wavelength of 800 nm. magnified image

Electrochromic properties of novel atmospheric pressure plasma jet-synthesized-organotungsten oxide films for flexible electrochromic devices

An investigation was conducted in electrochromic performance of organotungsten oxide WO x C y films deposited onto 40 Ω/square flexible PET (polyethylene terephthalate)/ITO (indium tin oxide) substrates using atmospheric pressure plasma jet (APPJ) at various precursor injection angles. A precursor [tungsten carbonyl, W(CO) 6;TC] vapor, carried by argon gas, was injected into air plasma torch. The APPJ-synthesized WO x C y films were proven to offer extraordinary electrochromic performance. Cyclic voltammetry (CV) switching measurements indicated that only low driving voltages from −1 to +1 V are needed to offer reversible Li + ion intercalation and de-intercalation in a 1 M LiClO 4–propylene carbonate (PC) electrolyte. Light modulation with up to 72.5% transmittance variation, optical density change of 0.84 and coloration efficiency of 49.6 cm 2/mC at a wavelength of 797.6 nm after 200 cycles of Li + ion intercalation and deintercalation were obtained.

Wound Bleeding Control by Low Temperature Air Plasma

A portable low temperature air plasma torch was used to control bleeding from wounds. As animal models, two pigs were used in the tests: one for the plasma treatment, and the other as the untreated control. Plasma effects on the bleeding times of three types of wounds (straight cut and cross cut in the ham area, and a hole in the saphenous vein of an ear) were examined. The results were that this plasma torch shortened the bleeding time for these three types of wounds from about 3 min to 18 s, about 4 min to 13 s, and 88 s to 15 s, respectively. Emission spectroscopy of the torch was performed to explore the reactive species carried by the plasma effluent of the torch. The results show that this torch carries abundant reactive atomic oxygen (RAO), which is the dominant reactive species in the plasma effluent. RAO can activate erythrocyte-platelet interactions to enhance blood coagulation for plug formation. The present tests indicate that RAO can also penetrate through the skin surrounding the wound to block capillary blood flow to the wound.

Extreme durability of wettability changes on polyolefin surfaces by atmospheric pressure plasma torch

In the present work three common polyolefins: high density polyethylene (HDPE), low density polyethylene (LDPE) and polypropylene (PP) have been treated with an atmospheric pressure air plasma torch (APPT) in order to improve their wettability properties. The variations in surface energy (γ s), as well as the durability of the treatment are determined by means of contact angle measurements for different aging times after plasma exposure (up to 270 days) using five test liquids which cover a wide range of polarities. The introduction of new polar moieties (carbonyl, amine or hydroxyl) is confirmed by Fourier transform infrared spectroscopy in attenuated total multiple reflection mode (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Furthermore, scanning electron microscopy (SEM) provides information on the morphological changes and variation on surface roughness, revealing that smoother, lamellar and semispheric micrometric structures are created on the LDPE, HDPE and PP surfaces, respectively. Results show that APPT treatment enhances both the total and polar components of the γ s under study, with an unprecedent stability (> 8 months) in time.

Contribution of a portable air plasma torch to rapid blood coagulation as a method of preventing bleeding

The effectiveness and mechanism of a low temperature air plasma torch in clotting blood are explored. Both blood droplets and smeared blood samples were used in the tests. The treated droplet samples reveal how blood clotting depends on the distance at which the torch operated, and for how long the droplets have been exposed to the torch. Microscopy and cell count of smeared blood samples shed light on dependencies of erythrocyte and platelet counts on torch distance and exposure time. With an increase of torch distance, the platelet count of treated blood samples increases but is less than that of the control. The flux of reactive atomic oxygen (RAO) and the degree of blood clotting decreased. With an increase of exposure time, platelet count of treated samples decreased, while the degree of clot increased. The correlation among these dependencies and published data support a blood clotting mechanism that RAO as well as other likely reactive oxygen species generated by the plasma torch activate erythrocyte–platelets interactions and induces blood coagulation.

Development of a laboratory scale air plasma torch and its application to electronic waste treatment

Expansion in electrical and electronic equipment trade has led to significant increase in electronic waste which should be dealt with special priority due to its potential negative impact to the public health and the environment. Thermal plasma technology offers a very promising alternative of hazardous waste treatment for the near future. In this study, a laboratory scale apparatus for generating high temperature plasma flame was presented. Design of a 20 kW plasma torch system was based on a non transferred direct current arc discharge with air as a medium gas. In this investigation, measurements of temperature distribution were performed. It was shown that high temperature flames can be generated, comparable to those reported in the literature. The gas temperature was found to increase with an increase in power input. The flame temperature was found to further increase from 1210 K to 1480 K when a small amount of added fuel gas. Assessment of electronic waste treatment using the air plasma system in a batch operation was also carried out. It was shown that the system was able to convert the electronic waste into combustible gas and inert solid residues. High mass loss rate of bulk electronic waste was demonstrated.