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Sample records for oxygen dc plasma

  1. Modelling chemical reactions in dc plasma inside oxygen bubbles in water

    NASA Astrophysics Data System (ADS)

    Takeuchi, N.; Ishii, Y.; Yasuoka, K.

    2012-02-01

    Plasmas generated inside oxygen bubbles in water have been developed for water purification. Zero-dimensional numerical simulations were used to investigate the chemical reactions in plasmas driven by dc voltage. The numerical and experimental results of the concentrations of hydrogen peroxide and ozone in the solution were compared with a discharge current between 1 and 7 mA. Upon increasing the water vapour concentration inside bubbles, we saw from the numerical results that the concentration of hydrogen peroxide increased with discharge current, whereas the concentration of ozone decreased. This finding agreed with the experimental results. With an increase in the discharge current, the heat flux from the plasma to the solution increased, and a large amount of water was probably vaporized into the bubbles.

  2. Argon–oxygen dc magnetron discharge plasma probed with ion acoustic waves

    SciTech Connect

    Saikia, Partha Saikia, Bipul Kumar; Goswami, Kalyan Sindhu; Phukan, Arindam

    2014-05-15

    The precise determination of the relative concentration of negative ions is very important for the optimization of magnetron sputtering processes, especially for those undertaken in a multicomponent background produced by adding electronegative gases, such as oxygen, to the discharge. The temporal behavior of an ion acoustic wave excited from a stainless steel grid inside the plasma chamber is used to determine the relative negative ion concentration in the magnetron discharge plasma. The phase velocity of the ion acoustic wave in the presence of negative ions is found to be faster than in a pure argon plasma, and the phase velocity increases with the oxygen partial pressure. Optical emission spectroscopy further confirms the increase in the oxygen negative ion density, along with a decrease in the argon positive ion density under the same discharge conditions. The relative negative ion concentration values measured by ion acoustic waves are compared with those measured by a single Langmuir probe, and a similarity in the results obtained by both techniques is observed.

  3. Effect of Si on DC arc plasma generation from Al-Cr and Al-Cr-Si cathodes used in oxygen

    NASA Astrophysics Data System (ADS)

    Zhirkov, I.; Landälv, L.; Göthelid, E.; Ahlgren, M.; Eklund, P.; Rosen, J.

    2017-02-01

    Al2O3 alloyed with Cr is an important material for the tooling industry. It can be synthesized from an arc discharge using Al-Cr cathodes in an oxygen atmosphere. Due to formation of Al-rich oxide islands on the cathode surface, the arc process stability is highly sensitive to oxygen pressure. For improved stability, the use of Al0.70Cr0.25Si0.05 cathodes has previously been suggested, where Si may reduce island formation. Here, we have investigated the effect of Si by comparing plasma generation and thin film deposition from Al0.7Cr0.3 and Al0.7Cr0.25Si0.05 cathodes. Plasma ion composition, ion energies, ion charge states, neutral species, droplet formation, and film composition have been characterized at different O2 flow rates for arc currents of 60 and 90 A. Si and related compounds are detected in plasma ions and in plasma neutrals. Scanning electron microscopy and energy dispersive X-ray analysis show that the cathode composition and the film composition are the same, with Si present in droplets as well. The effect of Si on the process stability, ion energies, and ion charge states is found to be negligible compared to that of the arc current. The latter is identified as the most relevant parameter for tuning the properties of the reactive discharge. The present work increases the fundamental understanding of plasma generation in a reactive atmosphere, and provides input for the choice of cathode composition and process parameters in reactive DC arc synthesis.

  4. First experimental results from DC/DC and AC/DC plasma-based power transformers

    NASA Astrophysics Data System (ADS)

    McEvoy, Aaron; Gibson, William; Nebel, Richard

    2016-10-01

    A plasma-based power transformer has been built and operated in both DC/DC and AC/DC mode. The proprietary Tibbar Plasma Technologies, Inc. transformer design consists of two cylindrically symmetric helical primary electrodes surrounding a low temperature plasma within which a secondary axial current is generated. Initial experimental results have compared well with simulations and moderate conversion efficiencies have been observed. A new proprietary device is currently being constructed that will utilize 3-phase 480 VAC input to achieve higher conversion efficiency and output power. A description of the apparatus and several potential applications will be presented along with preliminary experimental data demonstrating the DC/DC and AC/DC conversion processes. Work performed under ARPA-E contract DE-AR0000677.

  5. Pulsed-DC DBD Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Duong, Alan; McGowan, Ryan; Disser, Katherine; Corke, Thomas; Matlis, Eric

    2016-11-01

    A new powering system for dielectric barrier discharge (DBD) plasma actuators that utilizes a pulsed-DC waveform is presented. The plasma actuator arrangement is identical to most typical AC-DBD designs with staggered electrodes that are separated by a dielectric insulator. However instead of an AC voltage input to drive the actuator, the pulsed-DC utilizes a DC voltage source. The DC source is supplied to both electrodes, and remains constant in time for the exposed electrode. The DC source for the covered electrode is periodically grounded for very short instants and then allowed to rise to the source DC level. This process results in a plasma actuator body force that is significantly larger than that with an AC-DBD at the same voltages. The important characteristics used in optimizing the pulsed-DC plasma actuators are presented. Time-resolved velocity measurements near the actuator are further used to understand the underlying physics of its operation compared to the AC-DBD. Supported by NASA Glenn RC.

  6. A dc Penning Surface-Plasma Source

    DTIC Science & Technology

    2007-11-02

    LA-UR-93-2990 Title: A dc Penning Surface-Plasma Source Author(s): Submitted to: H. Vernon Smith, Jr., Paul Allison, Carl Geisik, David R...Type: HC Number of Copies In Library: 000001 Record ID: 28620 A de Penning Surface-Plasma Source* H. Vernon Smith, Jr., Paul Allison, Carl Geisik...Schechter, J. H. Whealton, and J. J. Donaghy, ATP Conf. Proc. No. 158, 366 (1987). 8) H. V. Smith, Jr., N. M. Schnurr, D. H. Whitaker , and K. E. Kalash

  7. CVD diamond growth by dc plasma torch

    NASA Astrophysics Data System (ADS)

    Klocek, Paul; Hoggins, James T.; Taborek, Peter; McKenna, Tom A.

    1990-12-01

    A dc arc discharge plasma torch has been developed for chemical vapor deposition (CVD) diamond growth. The apparatus and process parameters are described. Free-standing polycrystalline diamond samples of 50 mm by 50 mm by a few mm have been grown at high rates. The Raman spectra of the samples show little nondiamond structure. Transmission electron microscopy indicates that the diamond is highly twinned and has a high defect concentration. The infrared spectra indicate the presence of hydrogen contamination in the diamond via absorption bands associated with carbon-hydrogen motion. 2.

  8. Simulation of the dc Plasma in Carbon Nanotube Growth

    NASA Technical Reports Server (NTRS)

    Hash, David; Bose, Deepak; Govindan, T. R.; Meyyappan, M.; Biegel, Bryan (Technical Monitor)

    2003-01-01

    A model for the dc plasma used in carbon nanotube growth is presented, and one-dimensional simulations of an acetylene/ammonia/argon system are performed. The effect of dc bias is illustrated by examining electron temperature, electron and ion densities, and neutral densities. Introducing a tungsten filament in the dc plasma, as in hot filament chemical vapor deposition with plasma assistance, shows negligible influence on the system characteristics.

  9. Comparison of pulsating DC and DC power air-water plasma jet: A method to decrease plume temperature and increase ROS

    NASA Astrophysics Data System (ADS)

    Liu, K.; Hu, H.; Lei, J.; Hu, Y.; Zheng, Z.

    2016-12-01

    Most air-water plasma jets are rich in hydroxyl radicals (•OH), but the plasma has higher temperatures, compared to that of pure gas, especially when using air as working gas. In this paper, pulsating direct current (PDC) power was used to excite the air-water plasma jet to reduce plume temperature. In addition to the temperature, other differences between PDC and DC plasma jets are not yet clear. Thus, comparative studies of those plasmas are performed to evaluate characteristics, such as breakdown voltage, temperature, and reactive oxygen species. The results show that the plume temperature of PDC plasma is roughly 5-10 °C lower than that of DC plasma in the same conditions. The •OH content of PDC is lower than that of DC plasma, whereas the O content of PDC plasma is higher. The addition of water leads in an increase in the plume temperature and in the production of •OH with two types of power supplies. The production of O inversely shows a declining tendency with higher water ratio. The most important finding is that the PDC plasma with 100% water ratio achieves lower temperature and more abundant production of •OH and O, compared with DC plasma with 0% water ratio.

  10. Chamber For Testing Polymers In Oxygen Plasma

    NASA Technical Reports Server (NTRS)

    Whitaker, Ann F.

    1990-01-01

    Apparatus holds polymer specimen at constant temperature while exposing it to oxygen plasma. Copper tube (part of cooling coil) extends into plasma chamber, supporting copper block and thermoelectric module on which specimen mounted. Copper block made small - 4.4 by 3.8 by 1.6 cm - having little effect on plasma. Used to evaluate resistances of polymer materials to plasma environments, and for analysis of gases produced by attack of plasma on polymer specimen.

  11. Dust structurization observed in a dc glow discharge dusty plasma

    NASA Astrophysics Data System (ADS)

    Heinrich, Jonathon R.; Kim, Su-Hyun; Merlino, Robert L.

    2010-11-01

    Dusty plasmas, which are inherently open systems which require an ionization source to replenish the plasma absorbed on the grains, tend to exhibit self-organization. Various structures have been observed in dusty plasmas such as dust crystals, voids, and vortices. Due to the presence of drifting ions in dc discharge plasmas, spontaneously excited dust acoustic waves are also a common occurrence. By adjusting the discharge parameters we have observed a new phenomenon in dusty plasmas -- the spontaneous formation of three-dimensional stationary dust density structures. These structures appear as an ordered pattern consisting of alternating regions of high and low dust density arranged in a nested bowl-type configuration The stationary structure evolves from dust density waves that slow down as their wavelength decreases and eventually stop moving when the wavelength reaches some minimum size.

  12. dc-plasma-sprayed electronic-tube device

    DOEpatents

    Meek, T.T.

    1982-01-29

    An electronic tube and associated circuitry which is produced by dc plasma arc spraying techniques is described. The process is carried out in a single step automated process whereby both active and passive devices are produced at very low cost. The circuitry is extremely reliable and is capable of functioning in both high radiation and high temperature environments. The size of the electronic tubes produced are more than an order of magnitude smaller than conventional electronic tubes.

  13. FAST TRACK COMMUNICATION: Plasma agents in bio-decontamination by dc discharges in atmospheric air

    NASA Astrophysics Data System (ADS)

    Machala, Zdenko; Chládeková, Lenka; Pelach, Michal

    2010-06-01

    Bio-decontamination of water and surfaces contaminated by bacteria (Salmonella typhimurium) was investigated in two types of positive dc discharges in atmospheric pressure air, in needle-to-plane geometry: the streamer corona and its transition to a novel regime called transient spark with short high current pulses of limited energy. Both generate a cold non-equilibrium plasma. Electro-spraying of treated water through a needle electrode was applied for the first time and resulted in fast bio-decontamination. Experiments providing separation of various biocidal plasma agents, along with the emission spectra and coupled with oxidation stress measurements in the cell membranes helped to better understand the mechanisms of microbial inactivation. The indirect exposure of contaminated surfaces to neutral active species was almost as efficient as the direct exposure to the plasma, whereas applying only UV radiation from the plasma had no biocidal effects. Radicals and reactive oxygen species were identified as dominant biocidal agents.

  14. Determination of Ground-Laboratory to In-Space Effective Atomic Oxygen Fluence for DC 93?500 Silicone

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Banks, Bruce A.; Ma, David

    2004-01-01

    The objective of this research was to calibrate the ground-to-space effective atomic oxygen fluence for DC 93-500 silicone in a thermal energy electron cyclotron resonance (ECR) oxygen plasma facility. Silicones, commonly used spacecraft materials, do not chemically erode with atomic oxygen attack like other organic materials but form an oxidized hardened silicate surface layer. Therefore, the effective atomic oxygen fluence in a ground test facility should not be determined based on mass loss measurements, as they are with organic polymers. A technique has been developed at the Glenn Research Center to determine the equivalent amount of atomic oxygen exposure in an ECR ground test facility to produce the same degree of atomic oxygen damage as in space. The approach used was to compare changes in the surface hardness of ground test (ECR) exposed DC 93-500 silicone with DC 93-500 exposed to low Earth orbit (LEO) atomic oxygen as part of a shuttle flight experiment. The ground to in-space effective atomic oxygen fluence correlation was determined based on the fluence in the ECR source that produced the same hardness for the fluence in-space. Nanomechanical hardness versus contact depth measurements were obtained for five ECR exposed DC 93-500 samples (ECR exposed for 18 to 40 hrs, corresponding to Kapton effective fluences of 4.2 x 10(exp 20) to 9.4 x 10(exp 20) atoms/sq cm, respectively) and for space exposed DC 93-500 from the Evaluation of Oxygen Interactions with Materials III (EOIM III) shuttle flight experiment, exposed to LEO atomic oxygen for 2.3 x 10(exp 20) atoms/sq cm. Pristine controls were also evaluated. A ground-to-space correlation value was determined based on correlation values for four contact depths (150, 200, 250, and 300 nm), which represent the near surface depth data. The results indicate that the Kapton effective atomic oxygen fluence in the ECR facility needs to be 2.64 times higher than in LEO to replicate equivalent exposure damage in the

  15. Cold atmospheric plasma jet in an axial DC electric field

    NASA Astrophysics Data System (ADS)

    Lin, Li; Keidar, Michael

    2016-08-01

    Cold atmospheric plasma (CAP) jet is currently intensively investigated as a tool for new and potentially transformative cancer treatment modality. However, there are still many unknowns about the jet behavior that requires attention. In this paper, a helium CAP jet is tested in an electrostatic field generated by a copper ring. Using Rayleigh microwave scattering method, some delays of the electron density peaks for different ring potentials are observed. Meanwhile, a similar phenomenon associated with the bullet velocity is found. Chemical species distribution along the jet is analyzed based on the jet optical emission spectra. The spectra indicate that a lower ring potential, i.e., lower DC background electric field, can increase the amount of excited N2, N2+, He, and O in the region before the ring, but can decrease the amount of excited NO and HO almost along the entire jet. Combining all the results above, we discovered that an extra DC potential mainly affects the temporal plasma jet properties. Also, it is possible to manipulate the chemical compositions of the jet using a ring with certain electric potentials.

  16. Investigation of plasma parameters in an active screen cage-pulsed dc plasma used for plasma nitriding

    NASA Astrophysics Data System (ADS)

    Naeem, M.; Khattak, Z. I.; Zaka-ul-Islam, M.; Shabir, S.; Khan, A. W.; Zakaullah, M.

    2014-11-01

    Active screen cage-pulsed dc plasmas are widely used in the material processing applications such as plasma nitriding, carburizing and nitrocarburizing. Specifically for plasma nitriding applications, a H2-N2 mixture is used. In this article, a study of the electron number density (ne), atomic nitrogen density ([N]), electron temperature ? and the excitation temperature ? is reported in the presence of an active screen cage-pulsed dc plasma. The ne and ? are determined here by a triple Langmuir probe, while [N] and ? are estimated by optical emission spectroscopy (OES). The two temperatures and their ratio ? are compared for different input parameters (such as applied power, gas pressure and H2 percentage). This study is useful in active screen cage plasma nitriding applications where only few plasma diagnostic measurements have been reported.

  17. Biochar activated by oxygen plasma for supercapacitors

    NASA Astrophysics Data System (ADS)

    Gupta, Rakesh Kumar; Dubey, Mukul; Kharel, Parashu; Gu, Zhengrong; Fan, Qi Hua

    2015-01-01

    Biochar, also known as black carbon, is a byproduct of biomass pyrolysis. As a low-cost, environmental-friendly material, biochar has the potential to replace more expensive synthesized carbon nanomaterials (e.g. carbon nanotubes) for use in future supercapacitors. To achieve high capacitance, biochar requires proper activation. A conventional approach involves mixing biochar with a strong base and baking at a high temperature. However, this process is time consuming and energy inefficient (requiring temperatures >900 °C). This work demonstrates a low-temperature (<150 °C) plasma treatment that efficiently activates a yellow pine biochar. Particularly, the effects of oxygen plasma on the biochar microstructure and supercapacitor characteristics are studied. Significant enhancement of the capacitance is achieved: 171.4 F g-1 for a 5-min oxygen plasma activation, in comparison to 99.5 F g-1 for a conventional chemical activation and 60.4 F g-1 for untreated biochar. This enhancement of the charge storage capacity is attributed to the creation of a broad distribution in pore size and a larger surface area. The plasma activation mechanisms in terms of the evolution of the biochar surface and microstructure are further discussed.

  18. Inactivation of Microcystis aeruginosa by DC glow discharge plasma: Impacts on cell integrity, pigment contents and microcystins degradation.

    PubMed

    Zhang, Hong; Yang, Linfang; Yu, Zengliang; Huang, Qing

    2014-03-15

    We proposed a method to inactivate M. aeruginosa by using discharge plasma taking at the gas-solution interface supplied by DC power. Multiple analysis techniques including fluorescence excitation-emission matrix (EEM) and flow cytometry (FCM) were used to reveal the inactivation mechanism of M. aeruginosa. The photosynthetic pigment contents including phycocyanin, chlorophyll and metabolites were examined quantitatively. The DC glow discharge plasma caused an increased level of reactive oxygen species (ROS), and the damage of M. aeruginosa cells are mainly attributed to the oxidative stress including OH attack and H2O2 oxidation. Our findings demonstrate that plasma oxidation is a promising technology for inactivation of M. aeruginosa cells with simultaneous removal of microcystins and so it may lead us to a new route to efficient treatment of cyanobacterial blooms.

  19. Scaled-Up Nonequilibrium Air Plasmas Generated by DC and Pulsed Discharges

    DTIC Science & Technology

    2010-09-08

    scalability of nonequilibrium plasmas produced by electrical discharges in atmospheric pressure air. Both DC and repetitively pulsed discharges ...Key results demonstrate that both DC glow discharge and pulsed transient spark generate air plasmas of required parameters. Glow discharge is easier...Corona discharge as a temperature probe was developed to diagnose the microwave torch preheated air. A new concept of the DC-driven pulsed

  20. Wettability interpretation of oxygen plasma modified poly(methyl methacrylate).

    PubMed

    Chai, Jinan; Lu, Fuzhi; Li, Baoming; Kwok, Daniel Y

    2004-12-07

    Poly(methyl methacrylate) (PMMA) has been modified via a dc pulsed oxygen plasma for different treatment times. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS), optical profilometer, zeta potential, and advancing contact angle measurements. The measured advancing contact angles of water decreased considerably as a function of discharge. Several oxygen-based functionalities (carbonyl, carboxyl, carbonate, etc.) were detected by XPS, while zeta potential measurements confirmed an increase in negative charge for the treated PMMA surface. Evaluating the correlation between the concentration of polar chemical species and zeta potential, we found that increase in surface hydrophilicity results from the coeffect due to incorporation of oxygen functional groups and creation of charge states. The electrical double layer (EDL) effect was also considered in contact angle interpretation by introducing an additional surface tension term into Young's equation. We also found that EDL contribution to the solid-liquid interfacial tension is negligible and can be safely ignored for the systems considered here.

  1. PIC/MCC simulation for magnetized capacitively coupled plasmas driven by combined dc/rf sources

    NASA Astrophysics Data System (ADS)

    Yang, Shali; Zhang, Ya; Jiang, Wei; Wang, Hongyu; Wang, Shuai

    2016-09-01

    Hybrid dc/rf capacitively coupled plasma (CCP) sources have been popular in substrate etching due to their simplicity in the device structure and better plasma property. In this work, the characteristics of magnetized capacitively coupled plasmas driven by combined dc/rf sources are described by a one-dimensional Particle-in-cell/Monte Carlo collision (PIC/MCC) model. The simulation is using a rf source of 13.56MHz in argon and at a low pressure of 50mTorr. The effects of dc voltage and magnetic field on the plasmas are examined for 200-400V and 0-200Gs. It is found that, to some extent, dc voltage will increase the plasma density, but plasma density drops with increasing dc voltage. The magnetic field will enhance the plasma density significantly, due to the magnetic field will increase the electron life time and decrease the loss to the electrodes. In the bulk plasma, electron temperature is increased with the magnetic field but decreased with the dc voltage. The electron temperature in sheath is higher than in bulk plasma, due to stochastic heating in sheath is greater than Ohmic heating in bulk plasma under low gas pressure. National Natural Science Foundation of China (11405067, 11105057, 11305032, 11275039).

  2. Increase in transmittance of unbacked aluminum filters exposed to RF or dc discharges in oxygen

    NASA Technical Reports Server (NTRS)

    Hunter, W. R.; Steele, G. N.; Gillette, R. B.

    1973-01-01

    Results of an experimental study of the effect of discharges in oxygen on the oxide thickness and transmittance of aluminum filters. The studies were performed by exposing the filters to RF discharges and dc glow discharges in oxygen. In all experiments except one in which an aluminum ring was used as the cathode an increase in the transmittance of the filters is noted. It is thus demonstrated that the transmittance of aluminum filters increases on exposure to electrical discharges in oxygen, although it is not certain whether this phenomenon is caused by atomic oxygen.

  3. Study of the Characteristics of DC and ICP Hybrid Discharge Plasmas

    NASA Astrophysics Data System (ADS)

    WANG, Zhan; GAO, Wei; ZHANG, Peng; YAN, Huijie; REN, Chunsheng

    2015-03-01

    In this paper, the double-discharge plasma generated by radio frequency (RF) and direct current (DC) has been investigated. In comparison with their single-frequency counterpart, the interaction between the two excitations is significant and beneficial. The results show that the RF discharge can effectively increase the DC discharge current and decrease the DC voltage; meanwhile the DC discharge is favorable to feed abundant high energy seed electrons to the ICP discharge sustaining at 13.56 MHz for the latter to acquire higher plasma density and lower plasma potential by increasing the ionization rate. The innovative design has been demonstrated to facilitate more homogeneous performance with higher plasma density. supported by National Natural Science Foundation of China (No. 11475038)

  4. Replacement of hydrogen peroxide cleaning with oxygen plasma

    NASA Astrophysics Data System (ADS)

    Adams, B. E.

    1992-03-01

    Comparison between the standard peroxide cleaning method and an oxygen plasma modified version was run on thin film bond monitors. The plasma modified version substituted oxygen plasma for the peroxide cleaning step in the process and reduced the DI rinse water temperature from 75 C to 25 C. A direct surface cleanliness comparison was made between the two cleaning methods using Auger spectroscopy. A beam lead and ribbon bonding experiment was also run on plasma-cleaned networks. Results of both experiments indicate that plasma cleaning is superior to peroxide cleaning and that reliable bonding can be done on plasma-cleaned thin film networks.

  5. New oxygen plasma process rivals laser cutting methods

    SciTech Connect

    Fernicola, R.C. )

    1994-06-01

    For many years, oxygen plasma cutting has been looked upon as a desirable process for cutting steel but not practical in production because of very short consumable parts life. Recently, a number of technical advances in the oxygen plasma cutting process provides parts life several times that of older systems and cut quality approaching that of laser systems. This paper discusses these advances.

  6. Dynamics of runaway tails with time-dependent sub-Dreicer dc fields in magnetized plasmas

    NASA Technical Reports Server (NTRS)

    Moghaddam-Taaheri, E.; Vlahos, L.

    1987-01-01

    The evolution of runaway tails driven by sub-Dreicer time-dependent dc fields in a magnetized plasma are studied numerically using a quasi-linear code based on the Ritz-Galerkin method and finite elements. It is found that the runaway tail maintained a negative slope during the dc field increase. Depending on the values of the dc electric field at t = 0 and the electron gyrofrequency to the plasma frequency ratio the runaway tail became unstable to the anomalous Doppler resonance or remained stable before the saturation of the dc field at some maximum value. The systems that remained stable during this stage became unstable to the anomalous Doppler or the Cerenkov resonances when the dc field was kept at the saturation level or decreased. Once the instability is triggered, the runaway tail is isotropized.

  7. Dynamics of runaway tails with time-dependent sub-Dreicer dc fields in magnetized plasmas

    SciTech Connect

    Moghaddam-Taaheri, E.; Vlahos, L.

    1987-10-01

    The evolution of runaway tails driven by sub-Dreicer time-dependent dc fields in a magnetized plasma are studied numerically using a quasilinear code based on the Ritz--Galerkin method and finite elements. It is found that the runaway tail maintained a negative slope during the dc field increase. Depending on the values of the dc electric field at t = 0 and the electron gyrofrequency to the plasma frequency ratio the runaway tail became unstable to the anomalous Doppler resonance or remained stable before the saturation of the dc field at some maximum value. The systems that remained stable during this stage became unstable to the anomalous Doppler or the C-hacekerenkov resonances when the dc field was kept at the saturation level or decreased. Once the instability is triggered, the runaway tail is isotropized.

  8. Computational study of sheath structure in oxygen containing plasmas at medium pressures

    NASA Astrophysics Data System (ADS)

    Hrach, Rudolf; Novak, Stanislav; Ibehej, Tomas; Hrachova, Vera

    2016-09-01

    Plasma mixtures containing active species are used in many plasma-assisted material treatment technologies. The analysis of such systems is rather difficult, as both physical and chemical processes affect plasma properties. A combination of experimental and computational approaches is the best suited, especially at higher pressures and/or in chemically active plasmas. The first part of our study of argon-oxygen mixtures was based on experimental results obtained in the positive column of DC glow discharge. The plasma was analysed by the macroscopic kinetic approach which is based on the set of chemical reactions in the discharge. The result of this model is a time evolution of the number densities of each species. In the second part of contribution the detailed analysis of processes taking place during the interaction of oxygen containing plasma with immersed substrates was performed, the results of the first model being the input parameters. The used method was the particle simulation technique applied to multicomponent plasma. The sheath structure and fluxes of charged particles to substrates were analysed in the dependence on plasma pressure, plasma composition and surface geometry.

  9. DC Plasma Synthesis of Vertically Aligned Carbon Nanofibers for Biointerfacing

    NASA Astrophysics Data System (ADS)

    Pearce, Ryan Christopher

    Vertically aligned carbon nanofibers (VACNFs) are a class of materials whose nanoscale dimensions and physical properties makes them uniquely suitable as functional elements in many applications for biodetection and biointerfacing on a cellular level. Control of VACNF synthesis by catalytic plasma enhanced chemical vapor deposition (PECVD) presents many challenges in integration into devices and structures designed for biointerfacing, such as transparent or flexible substrates. This dissertation addresses ways to overcome many of these issues in addition to deepening the fundamental understanding of nano-synthesis in catalytic PECVD. First, a survey of the field of VACNF synthesis and biointerfacing is presented, identifying the present challenges and greatest experimental applications. It is followed by experimental observations that elucidate the underlying mechanism to fiber alignment during synthesis, a critical step for deterministic control of fiber growth. Using a grid of electrodes patterned by photolithography on an insulating substrate, it was found that the alignment of the fibers is controlled by the anisotropic etching provided by ions during dc-PECVD synthesis. The VACNFs that have been utilized for many cellular interfacing experiments have unique mechanical and fluorescent properties due to a SiNx coating. The mechanism for SiNx deposition to VACNF sidewalls during synthesis is explored in addition to a detailed study of the optical properties of the coating. To explain the optical properties of this coating it is proposed that the source of photoluminescence for the SiNx coated VACNFs is quantum confinement effects due to the presence of silicon nanoclusters embedded in a Si3N4 matrix. These luminescent fibers have proven useful as registry markers in cell impalefection studies. To realize VACNF arrays used as an inflatable angioplasty balloon with embedded fibers to deliver drugs across the blood-brain barrier, a method for transferring fibers to

  10. How plasma induced oxidation, oxygenation, and de-oxygenation influences viability of skin cells

    NASA Astrophysics Data System (ADS)

    Oh, Jun-Seok; Strudwick, Xanthe; Short, Robert D.; Ogawa, Kotaro; Hatta, Akimitsu; Furuta, Hiroshi; Gaur, Nishtha; Hong, Sung-Ha; Cowin, Allison J.; Fukuhara, Hideo; Inoue, Keiji; Ito, Masafumi; Charles, Christine; Boswell, Roderick W.; Bradley, James W.; Graves, David B.; Szili, Endre J.

    2016-11-01

    The effect of oxidation, oxygenation, and de-oxygenation arising from He gas jet and He plasma jet treatments on the viability of skin cells cultured in vitro has been investigated. He gas jet treatment de-oxygenated cell culture medium in a process referred to as "sparging." He plasma jet treatments oxidized, as well as oxygenated or de-oxygenated cell culture medium depending on the dissolved oxygen concentration at the time of treatment. He gas and plasma jets were shown to have beneficial or deleterious effects on skin cells depending on the concentration of dissolved oxygen and other oxidative molecules at the time of treatment. Different combinations of treatments with He gas and plasma jets can be used to modulate the concentrations of dissolved oxygen and other oxidative molecules to influence cell viability. This study highlights the importance of a priori knowledge of the concentration of dissolved oxygen at the time of plasma jet treatment, given the potential for significant impact on the biological or medical outcome. Monitoring and controlling the dynamic changes in dissolved oxygen is essential in order to develop effective strategies for the use of cold atmospheric plasma jets in biology and medicine.

  11. Effect of additive oxygen gas on cellular response of lung cancer cells induced by atmospheric pressure helium plasma jet

    NASA Astrophysics Data System (ADS)

    Joh, Hea Min; Choi, Ji Ye; Kim, Sun Ja; Chung, T. H.; Kang, Tae-Hong

    2014-10-01

    The atmospheric pressure helium plasma jet driven by pulsed dc voltage was utilized to treat human lung cancer cells in vitro. The properties of plasma plume were adjusted by the injection type and flow rate of additive oxygen gas in atmospheric pressure helium plasma jet. The plasma characteristics such as plume length, electric current and optical emission spectra (OES) were measured at different flow rates of additive oxygen to helium. The plasma plume length and total current decreased with an increase in the additive oxygen flow rate. The electron excitation temperature estimated by the Boltzmann plot from several excited helium emission lines increased slightly with the additive oxygen flow. The oxygen atom density in the gas phase estimated by actinometry utilizing argon was observed to increase with the additive oxygen flow. The concentration of intracellular reactive oxygen species (ROS) measured by fluorescence assay was found to be not exactly proportional to that of extracellular ROS (measured by OES), but both correlated considerably. It was also observed that the expression levels of p53 and the phospho-p53 were enhanced in the presence of additive oxygen flow compared with those from the pure helium plasma treatment.

  12. Effect of additive oxygen gas on cellular response of lung cancer cells induced by atmospheric pressure helium plasma jet.

    PubMed

    Joh, Hea Min; Choi, Ji Ye; Kim, Sun Ja; Chung, T H; Kang, Tae-Hong

    2014-10-16

    The atmospheric pressure helium plasma jet driven by pulsed dc voltage was utilized to treat human lung cancer cells in vitro. The properties of plasma plume were adjusted by the injection type and flow rate of additive oxygen gas in atmospheric pressure helium plasma jet. The plasma characteristics such as plume length, electric current and optical emission spectra (OES) were measured at different flow rates of additive oxygen to helium. The plasma plume length and total current decreased with an increase in the additive oxygen flow rate. The electron excitation temperature estimated by the Boltzmann plot from several excited helium emission lines increased slightly with the additive oxygen flow. The oxygen atom density in the gas phase estimated by actinometry utilizing argon was observed to increase with the additive oxygen flow. The concentration of intracellular reactive oxygen species (ROS) measured by fluorescence assay was found to be not exactly proportional to that of extracellular ROS (measured by OES), but both correlated considerably. It was also observed that the expression levels of p53 and the phospho-p53 were enhanced in the presence of additive oxygen flow compared with those from the pure helium plasma treatment.

  13. Effect of additive oxygen gas on cellular response of lung cancer cells induced by atmospheric pressure helium plasma jet

    PubMed Central

    Joh, Hea Min; Choi, Ji Ye; Kim, Sun Ja; Chung, T. H.; Kang, Tae-Hong

    2014-01-01

    The atmospheric pressure helium plasma jet driven by pulsed dc voltage was utilized to treat human lung cancer cells in vitro. The properties of plasma plume were adjusted by the injection type and flow rate of additive oxygen gas in atmospheric pressure helium plasma jet. The plasma characteristics such as plume length, electric current and optical emission spectra (OES) were measured at different flow rates of additive oxygen to helium. The plasma plume length and total current decreased with an increase in the additive oxygen flow rate. The electron excitation temperature estimated by the Boltzmann plot from several excited helium emission lines increased slightly with the additive oxygen flow. The oxygen atom density in the gas phase estimated by actinometry utilizing argon was observed to increase with the additive oxygen flow. The concentration of intracellular reactive oxygen species (ROS) measured by fluorescence assay was found to be not exactly proportional to that of extracellular ROS (measured by OES), but both correlated considerably. It was also observed that the expression levels of p53 and the phospho-p53 were enhanced in the presence of additive oxygen flow compared with those from the pure helium plasma treatment. PMID:25319447

  14. Generation of reactive oxygen and nitrogen species and its effects on DNA damage in lung cancer cells exposed to atmospheric pressure helium/oxygen plasma jets

    NASA Astrophysics Data System (ADS)

    Chung, Tae Hun; Joh, Hea Min; Kim, Sun Ja; Choi, Ji Ye; Kang, Tae-Hong

    2016-09-01

    We investigated the effects of the operating parameters on the generation of reactive oxygen and nitrogen species (RONS) in the gas and liquid phases exposed to atmospheric pressure a pulsed-dc helium plasma jets. The densities of reactive species including OH radicals were obtained at the plasma-liquid surface and inside the plasma-treated liquids using ultraviolet absorption spectroscopy and chemical probe method. And the nitrite concentration was detected by Griess assay. The data are very suggestive that there is a strong correlation among the production of RONS in the plasmas and liquids. Exposure of plasma to cancer cells increases the cellular levels of RONS, which has been linked to apoptosis and the damage of cellular proteins, and may also indirectly cause structural damage to DNA. To identify the correlation between the production of RONS in cells and plasmas, various assay analyses were performed on plasma treated human lung cancer cells (A549) cells. In addition, the effect of additive oxygen gas on the plasma-induced oxidative stress in cancer cells was investigated. It was observed that DNA damage was significantly increased with helium/oxygen plasma compared to with pure helium plasma.

  15. The hairline plasma: An intermittent negative dc-corona discharge at atmospheric pressure for plasma medical applications

    SciTech Connect

    Bussiahn, R.; Brandenburg, R.; Gerling, T.; Kindel, E.; Lange, H.; Lembke, N.; Weltmann, K.-D.; Woedtke, Th. von; Kocher, T.

    2010-04-05

    A cold atmospheric pressure plasma source, called hairline plasma, for biological and medical applications has been developed. Using the physical effect of the negative dc corona discharge, a nanosecond pulsed microplasma has been created. The device produces a very thin (dapprox30 mum) plasma filament with a length of up to 1.5 cm. Due to this geometrical parameters this plasma is particularly suitable for the treatment of microscopic cavities. The low plasma temperature allows to treat the human skin without any heating or painful irritation.

  16. Investigation on Plasma Jet Flow Phenomena During DC Air Arc Motion in Bridge-Type Contacts

    NASA Astrophysics Data System (ADS)

    Zhai, Guofu; Bo, Kai; Chen, Mo; Zhou, Xue; Qiao, Xinlei

    2016-05-01

    Arc plasma jet flow in the air was investigated under a bridge-type contacts in a DC 270 V resistive circuit. We characterized the arc plasma jet flow appearance at different currents by using high-speed photography, and two polished contacts were used to search for the relationship between roughness and plasma jet flow. Then, to make the nature of arc plasma jet flow phenomena clear, a simplified model based on magnetohydrodynamic (MHD) theory was established and calculated. The simulated DC arc plasma was presented with the temperature distribution and the current density distribution. Furthermore, the calculated arc flow velocity field showed that the circular vortex was an embodiment of the arc plasma jet flow progress. The combined action of volume force and contact surface was the main reason of the arc jet flow. supported by National Natural Science Foundation of China (Nos. 51307030, 51277038)

  17. Cleaning Carbon Nanotubes by Use of Mild Oxygen Plasmas

    NASA Technical Reports Server (NTRS)

    Petkov, Mihail

    2006-01-01

    Experiments have shown that it is feasible to use oxygen radicals (specifically, monatomic oxygen) from mild oxygen plasmas to remove organic contaminants and chemical fabrication residues from the surfaces of carbon nanotubes (CNTs) and metal/CNT interfaces. A capability for such cleaning is essential to the manufacture of reproducible CNT-based electronic devices. The use of oxygen radicals to clean surfaces of other materials is fairly well established. However, previously, cleaning of CNTs and of graphite by use of oxygen plasmas had not been attempted because both of these forms of carbon were known to be vulnerable to destruction by oxygen plasmas. The key to success of the present technique is, apparently, to ensure that the plasma is mild . that is to say, that the kinetic and internal energies of the oxygen radicals in the plasma are as low as possible. The plasma oxygen-radical source used in the experiments was a commercial one marketed for use in removing hydrocarbons and other organic contaminants from vacuum systems and from electron microscopes and other objects placed inside vacuum systems. In use, the source is installed in a vacuum system and air is leaked into the system at such a rate as to maintain a background pressure of .0.56 torr (.75 Pa). In the source, oxygen from the air is decomposed into monatomic oxygen by radio-frequency excitation of a resonance of the O2 molecule (N2 is not affected). Hence, what is produced is a mild (non-energetic) oxygen plasma. The oxygen radicals are transported along with the air molecules in the flow created by the vacuum pump. In the experiments, exposure to the oxygen plasma in this system was shown to remove organic contaminants and chemical fabrication residues from several specimens. Many high-magnification scanning electron microscope (SEM) images of CNTs were taken before and after exposure to the oxygen plasma. As in the example shown in the figure, none of these images showed evidence of degradation

  18. Oxygen plasma-treatment effects on Si transfer.

    PubMed

    Langowski, Bryan A; Uhrich, Kathryn E

    2005-07-05

    Oxygen plasma-treatment is commonly used to increase the hydrophilicity of poly(dimethylsiloxane) (PDMS) stamps used for microcontact printing (muCP) aqueous-based inks. Review of the literature reveals that a wide range of plasma parameters are currently employed to modify stamp surfaces. However, little is known about the effect of these parameters (e.g., power, chamber pressure, duration) on the undesirable transfer of low-molecular-weight silicon-containing fragments from the stamps that commonly occurs during muCP. To study the effect of oxygen plasma-treatment on Si transfer, unpatterned PDMS stamps were treated with oxygen plasma under various conditions and used to stamp deionized water on plasma-activated poly(methyl methacrylate) (PMMA) substrates. Once stamped, the PMMA substrates were analyzed with X-ray photoelectron spectroscopy (XPS) to quantify and characterize silicon present on the substrate surface. In addition, used PDMS stamps were analyzed with scanning electron microscopy (SEM) to observe topographical changes that occur during oxygen plasma-treatment. XPS results show that all plasma treatments studied significantly reduced the amount of Si transfer from the treated stamps during muCP as compared to untreated PDMS stamps and that the source of transfer is residual PDMS fragments not removed by oxygen plasma. SEM results show that, although the treated stamps undergo a variety of topographical changes, no correlation exists between stamp topography and extent of Si transfer from the stamps.

  19. Surface Modification of Poly Vinyl Chloride (PVC) Using Low Pressure Argon and Oxygen Plasma

    NASA Astrophysics Data System (ADS)

    Mahmood, Ghoranneviss; Sheila, Shahidi; Jakub, Wiener

    2010-04-01

    In this study, commercial poly vinyl chloride (PVC) films were treated by oxygen and argon plasmas in a cylindrical glass tube which was surrounded by a DC variable magnetic field, with different sample positions in the plasma reactor and also different exposure durations. Effects of the plasma treatment on the hydrophilic properties of the films were studied by measuring the water drop contact angle on the surface of the samples. The surface topography of the untreated and plasma treated films was analyzed and compared by atomic force microscopy (AFM). The optical characteristic changes in treated samples were investigated using reflective spectrophotometry. Also, the chemical changes which appeared on the surface of the samples were investigated using Fourier transform infrared spectroscopy (FTIR). The results show that the plasma treated PVC becomes more hydrophilic with an enhanced wettability. A sharp decrease in the water contact angle may also be a consequence of the surface texturization. The aging effect on wettability of the samples was also investigated. The results show that the effect of oxygen plasma on the surface properties of the samples is more pronounced compared with that of argon plasma.

  20. Submicrometre particle filtration with a dc activated plasma textile

    NASA Astrophysics Data System (ADS)

    Rasipuram, S. C.; Wu, M.; Kuznetsov, I. A.; Kuznetsov, A. V.; Levine, J. F.; Jasper, W. J.; Saveliev, A. V.

    2014-01-01

    Plasma textiles are novel fabrics incorporating the advantages of cold plasma and low-cost non-woven or woven textile fabrics. In plasma textiles, electrodes are integrated into the fabric, and a corona discharge is activated within and on the surface of the fabric by applying high voltages above 10 kV between the electrodes. When the plasma textile is activated, submicrometre particles approaching the textile are charged by the deposition of ions and electrons produced by the corona, and then collected by the textile material. A stable plasma discharge was experimentally verified on the surface of the textile that was locally smooth but not rigid. A filtration efficiency close to 100% was observed in experiments conducted on salt particles with diameters ranging from 50 to 300 nm. Unlike conventional fibrous filters, the plasma textile provided uniform filtration in this range, without exhibiting a maximum particle penetration size.

  1. [Study of plasma temperature measurements for oxygen discharge].

    PubMed

    Li, Liu-Cheng; Wang, Zeng-Qiang; Li, Gu-Fu; Duo, Li-Ping

    2011-10-01

    A radio-frequency discharge setup was constructed by two shell-shaped copper electrodes and a 30 cm long pyrex glass tube (i. d. = 1.65 cm) to examine the gas temperature of oxygen plasma in electric discharge oxygen iodine laser. The discharge was supplied by a 500 watt, 13.56 MHz radio-frequency power. The gas pressure in the discharge cavity was 1 330 Pa. The temperature of oxygen discharge plasma was measured by using the P branch of O2 (b, v = 0) rotational emission spectrum. Two methods were used to deduce the oxygen gas temperature. They are Boltzman plotting method and computer simulating spectrum method, respectively. Gauss fitting method was used to distinguish spectrum peaks for lower resolution spectrum. The spectrum peak area was used to characterize the optical emission intensity. The gas temperature of oxygen discharge plasma was obtained by Boltzmann plotting method. Alternatively, the optical emission spectrum was simulated by computer modeling with spectrometer slit function which was obtained by He-Ne laser. Consequently, the gas temperature of oxygen plasma was obtained by comparing the computer simulating spectrum and the experimentally observed spectrum according to the least square fitting rule. The measurement results with the two methods agree well. It was concluded that the simple optical technique can be used conveniently in the temperature diagnostics of oxygen radio-frequency discharge plasma.

  2. Long-distance oxygen plasma sterilization: Effects and mechanisms

    NASA Astrophysics Data System (ADS)

    Liu, Hongxia; Chen, Jierong; Yang, Liqing; Zhou, Yuan

    2008-01-01

    The distribution of electrons, ions and oxygen radicals in long-distance oxygen plasma and the germicidal effect (GE) of Escherichia coli on the surface of medical poly(tetrafluoroethylene) (PTFE) film were studied. The quantity of protein leakage and the production of lipid peroxide in bacterial suspension as well as the state of DNA were measured after sterilization to analyse the inactivation mechanisms. The results showed that the concentration of electrons and ions decreased rapidly with increasing the distance from the center of induction coil, which approximated to 0 at 30 cm, whereas the concentration of oxygen radicals reduced slowly, i.e. decreased 30% within 40 cm. GE value reached 3.42 in the active discharge zone (0 cm) and exceeded 3.32 within 40 cm when plasma treatment parameters were set as follows: plasma rf power at 100 W, treatment time at 60 s and oxygen flux at 40 cm 3/min. Fast etching action on cell membrane by electrons, ions and attacking polyunsaturation fatty acid (PUFA) in cell membrane by oxygen radicals are primary reasons of oxygen plasma sterilization in the active discharge and the afterglow zone, respectively. The GE of UV radiation in long-distance oxygen plasma is feebleness.

  3. Diagnostics of ballistic electrons in a DC/RF hybrid capacitively coupled plasma reactor

    NASA Astrophysics Data System (ADS)

    Xu, Lin; Chen, Lee; Ranjan, Alok; Funk, Merritt; Bravenec, Ron; Economou, Demetre; Donnelly, Vincent; Sundararajan, Radha

    2008-10-01

    The DC/RF hybrid is a capacitively coupled plasma etcher with RF voltage on the bottom electrode and negative DC bias on the upper electrode. This configuration can significantly alleviate the electron shading effect and preserve photoresist integrity during plasma etching. It is thought that a group of ballistic electrons is responsible for these results. These high-energy electrons start as secondaries emitted from the negatively-biased DC electrode and accelerate across the DC sheath. They acquire high enough energy in the sheath such that they can cross the bulk plasma without gas-phase collisions. The ballistic electrons either strike the RF electrode or are trapped in the plasma bulk depending on the RF phase. Two gridded energy analyzers mounted on the back of the RF electrode were used to determine the energy distribution of ballistic electrons. The dependence of the ballistic electron energy distribution on DC voltage, pressure and RF power will be presented and compared with simulation results.

  4. Polarity functions' characterization and the mechanism of starch modification by DC glow discharge plasma.

    PubMed

    Khorram, S; Zakerhamidi, M S; Karimzadeh, Z

    2015-01-01

    The wheat starch was investigated, before and after exposure to the argon and oxygen glow discharge plasma, without any added chemical reagents, using a novel media polarity functions method. The mechanisms of modification of starch in plasma discharge irradiation were explained using some methods such as; NMR, IR spectroscopy, Kamlet-Abboud-Taft polarity functions (specific and nonspecific interaction) of modified starch. The starch modification, by plasma treatment, shows valuable changes with plasma gas and relative ionized or active species. Characterizations indicate that argon glow discharge plasma increases crosslink in C-2 site of starch. Also, oxygen plasma discharge irradiation tends to oxidize the OH group in C-6 site of carbonyl group. Furthermore, the reported mechanisms show the highest efficiency, because of the stereo-chemical orientation of active sites of starch and plasma potential of wall in plasma media.

  5. Oxygen plasmas used to synthesize superoxides

    NASA Technical Reports Server (NTRS)

    Hollahan, J. R.; Wydeven, T.

    1972-01-01

    Production of alkali metal superoxides by interaction of molecular oxygen with alkali metals or their salts is discussed. Diagram of reactor to show components and operating principles is provided. Analysis of chemical reactions involved is developed.

  6. Thermal relaxation of a two dimensional plasma in a dc magnetic field. Part 2: Numerical simulation

    NASA Technical Reports Server (NTRS)

    Hsu, J. Y.; Joyce, G.; Montgomery, D.

    1974-01-01

    The thermal relaxation process for a spatially uniform two dimensional plasma in a uniform dc magnetic field is simulated numerically. Thermal relaxation times are defined in terms of the time necessary for the numerically computer Boltzman H-function to decrease through a given part of the distance to its minimum value. Dependence of relaxation time on two parameters is studied: number of particles per Debye square and ratio of gyrofrequency to plasma frequency.

  7. Thermal plasma treatment of stormwater sediments: comparison between DC non-transferred and partially transferred arc plasma.

    PubMed

    Li, O L; Guo, Y; Chang, J S; Saito, N

    2015-01-01

    The disposal of enormous amount of stormwater sediments becomes an emerging worldwide problem. Stormwater sediments are contaminated by heavy metals, phosphorus, trace organic and hydrocarbons, and cannot be disposed without treatment. Thermal plasma decontamination technology offers a high decomposition rate in a wide range of toxic organic compound and immobilization of heavy metal. In this study, we compared the treatment results between two different modes of thermal plasma: (1) a non-transferred direct current (DC) mode and (2) a partial DC-transferred mode. The reductions of total organic carbon (TOC) were, respectively, 25% and 80% for non-transferred and partially transferred plasma, respectively. Most of the toxic organic compounds were converted majorly to CxHy. In the gaseous emission, the accumulated CxHy, CO, NO and H2S were significantly higher in partially transferred mode than in non-transferred mode. The solid analysis demonstrated that the concentrations of Ca and Fe were enriched by 500% and 40%, respectively. New chemical compositions such as KAlSi3O8, Fe3O4, NaCl and CaSO4 were formed after treatment in partially DC-transferred mode. The power inputs were 1 and 10 kW, respectively, for non-transferred DC mode and a partially DC-transferred mode. With a lower energy input, non-transferred plasma treatment can be used for decontamination of sediments with low TOC and metal concentration. Meanwhile, partially transferred thermal plasma with higher energy input is suitable for treating sediments with high TOC percentage and volatile metal concentration. The organic compounds are converted into valuable gaseous products which can be recycled as an energy source.

  8. Experimental tests for carbon nanomaterial synthesis using DC plasma jet

    NASA Astrophysics Data System (ADS)

    Lange, H.; Łabȩdź, O.; Tylska, I.; Huczko, A.; Bystrzejewski, M.

    2014-11-01

    In the frame of this work some experimental tests were performed in the plasma jet. Pure ethanol vapour alone or with the addition of fine iron powder were used to synthesize few-layer graphene or carbon-encapsulated iron nanoparticles, respectively.

  9. Atomic oxygen patterning from a biomedical needle-plasma source

    SciTech Connect

    Kelly, Seán; Turner, Miles M.

    2013-09-28

    A “plasma needle” is a cold plasma source operating at atmospheric pressure. Such sources interact strongly with living cells, but experimental studies on bacterial samples show that this interaction has a surprising pattern resulting in circular or annular killing structures. This paper presents numerical simulations showing that this pattern occurs because biologically active reactive oxygen and nitrogen species are produced dominantly where effluent from the plasma needle interacts with ambient air. A novel solution strategy is utilised coupling plasma produced neutral (uncharged) reactive species to the gas dynamics solving for steady state profiles at the treated biological surface. Numerical results are compared with experimental reports corroborating evidence for atomic oxygen as a key bactericidal species. Surface losses are considered for interaction of plasma produced reactants with reactive solid and liquid interfaces. Atomic oxygen surface reactions on a reactive solid surface with adsorption probabilities above 0.1 are shown to be limited by the flux of atomic oxygen from the plasma. Interaction of the source with an aqueous surface showed hydrogen peroxide as the dominant species at this interface.

  10. Sintering of alumina in microwave-induced oxygen plasma

    SciTech Connect

    Su, H.; Johnson, D.L.

    1996-12-01

    Small cylindrical tubes were sintered in a microwave-induced oxygen plasma, initiated and sustained inside a tunable, single-mode cavity. Temperature and shrinkage measurements of the specimens were achieved using an optical-fiber thermometer black-body sensor and a dilatometer, respectively. Sintering experiments at constant heating rate were accomplished to obtain the activation energy for sintering of alumina in the plasma and in a conventional rapid-heating furnace. Diffusion of aluminum interstitials along grain boundaries was believed to be the dominant sintering mechanism, with an estimated activation energy of 488 {+-} 20 kJ/mol for conventional sintering and an average activation energy of 468 {+-} 20 kJ/mol for plasma sintering. A comparison of specimens sintered in the plasma to those sintered in a conventional furnace under the same temperature-time excursions and oxygen pressures showed an athermal effect due to the plasma. To further explore this athermal effect, sintering experiments in plasmas of different oxygen pressure were conducted. The athermal effect was ascribed to an increase of aluminum interstitial concentration during plasma sintering. Sintering data were interpreted using the combined-stage sintering model.

  11. Material Compatibility of Medical Sterilizer Using Oxygen Plasma

    NASA Astrophysics Data System (ADS)

    Tanaka, Hiroshi; Ono, Reoto; Hayashi, Nobuya; Hanada, Yasushi; Noda, Minoru; Goto, Masaaki

    2015-09-01

    Material compatibility of oxygen plasma sterilizer is investigated comparing with hydrogen peroxide (H2O2) sterilizers and a gaseous H2O2 sterilizer. Organic materials such as ABS, PE, PP, and PET are used as sample materials, and are irradiated by active oxygen species produced in oxygen plasma. After plasma irradiation, surface of the sample materials is observed using a scanning electron microscope and FTIR spectroscopy. Strengths of the organic materials are evaluated by the tension test. Also, H2O2 plasma sterilizer and a gaseous H2O2 sterilizer those are commercially available are utilized to compare the material compatibility, especially organic compounds. The ABS resin becomes slightly soft after irradiation by both plasmas and gaseous H2O2. Also, PET material becomes soften by each sterilization treatment. Decrease of peak heights of CH around 1200 and 1730 cm-1 and increase of that of OH at 3300 cm-1 in FTIR spectra indicates the oxidation of ABS resin by both plasma and gaseous H2O2. In the case of PET material, treatment by the plasma has not modified chemical composition but changed the crystal structure. The gaseous H2O2 is completely friendly for the PET material.

  12. Hot Plasma from Solar Active Region Cores: a Test of AC and DC Coronal Heating Models?

    NASA Astrophysics Data System (ADS)

    Schmelz, J. T.; Asgari-Targhi, M.; Christian, G. M.; Dhaliwal, R. S.; Pathak, S.

    2015-06-01

    Direct current (DC) models of solar coronal heating invoke magnetic reconnection to convert magnetic free energy into heat, whereas alternating current (AC) models invoke wave dissipation. In both cases the energy is supplied by photospheric footpoint motions. For a given footpoint velocity amplitude, DC models predict lower average heating rates but greater temperature variability when compared to AC models. Therefore, evidence of hot plasma (T > 5 MK) in the cores of active regions could be one of the ways for current observations to distinguish between AC and DC models. We have analyzed data from the X-Ray Telescope (XRT) and the Atmospheric Imaging Assembly for 12 quiescent active region cores, all of which were observed in the XRT Be_thick channel. We did Differential Emission Measure (DEM) analysis and achieved good fits for each data set. We then artificially truncated the hot plasma of the DEM model at 5 MK and examined the resulting fits to the data. For some regions in our sample, the XRT intensities continued to be well-matched by the DEM predictions, even without the hot plasma. This truncation, however, resulted in unacceptable fits for the other regions. This result indicates that the hot plasma is present in these regions, even if the precise DEM distribution cannot be determined with the data available. We conclude that reconnection may be heating the hot plasma component of these active regions.

  13. HOT PLASMA FROM SOLAR ACTIVE REGION CORES: A TEST OF AC AND DC CORONAL HEATING MODELS?

    SciTech Connect

    Schmelz, J. T.; Christian, G. M.; Dhaliwal, R. S.; Pathak, S.; Asgari-Targhi, M.

    2015-06-20

    Direct current (DC) models of solar coronal heating invoke magnetic reconnection to convert magnetic free energy into heat, whereas alternating current (AC) models invoke wave dissipation. In both cases the energy is supplied by photospheric footpoint motions. For a given footpoint velocity amplitude, DC models predict lower average heating rates but greater temperature variability when compared to AC models. Therefore, evidence of hot plasma (T > 5 MK) in the cores of active regions could be one of the ways for current observations to distinguish between AC and DC models. We have analyzed data from the X-Ray Telescope (XRT) and the Atmospheric Imaging Assembly for 12 quiescent active region cores, all of which were observed in the XRT Be-thick channel. We did Differential Emission Measure (DEM) analysis and achieved good fits for each data set. We then artificially truncated the hot plasma of the DEM model at 5 MK and examined the resulting fits to the data. For some regions in our sample, the XRT intensities continued to be well-matched by the DEM predictions, even without the hot plasma. This truncation, however, resulted in unacceptable fits for the other regions. This result indicates that the hot plasma is present in these regions, even if the precise DEM distribution cannot be determined with the data available. We conclude that reconnection may be heating the hot plasma component of these active regions.

  14. Electron-vibration relaxation in oxygen plasmas

    NASA Astrophysics Data System (ADS)

    Laporta, V.; Heritier, K. L.; Panesi, M.

    2016-06-01

    An ideal chemical reactor model is used to study the vibrational relaxation of oxygen molecules in their ground electronic state, X3Σg-, in presence of free electrons. The model accounts for vibrational non-equilibrium between the translational energy mode of the gas and the vibrational energy mode of individual molecules. The vibrational levels of the molecules are treated as separate species, allowing for non-Boltzmann distributions of their population. The electron and vibrational temperatures are varied in the range [0-20,000] K. Numerical results show a fast energy transfer between oxygen molecules and free electron, which causes strong deviation of the vibrational distribution function from Boltzmann distribution, both in heating and cooling conditions. Comparison with Landau-Teller model is considered showing a good agreement for electron temperature range [2000-12,000] K. Finally analytical fit of the vibrational relaxation time is given.

  15. Oxygen impurity radiation from Tokamak-like plasmas

    NASA Technical Reports Server (NTRS)

    Rogerson, J. E.; Davis, J.; Jacobs, V. L.

    1977-01-01

    We have constructed a nonhydrodynamic coronal model for calculating radiation from impurity atoms in a heated plasma. Some recent developments in the calculation of dielectronic recombination rate coefficients and collisional excitation rate coefficients are included. The model is applied to oxygen impurity radiation during the first few milliseconds of a TFR Tokamak plasma discharge, and good agreement with experimental results is obtained. Estimates of total line and continuum radiation from the oxygen impurity are given. It is shown that impurity radiation represents a considerable energy loss.

  16. Fluorophore-based sensor for oxygen radicals in processing plasmas

    SciTech Connect

    Choudhury, Faraz A.; Shohet, J. Leon; Sabat, Grzegorz; Sussman, Michael R.; Nishi, Yoshio

    2015-11-15

    A high concentration of radicals is present in many processing plasmas, which affects the processing conditions and the properties of materials exposed to the plasma. Determining the types and concentrations of free radicals present in the plasma is critical in order to determine their effects on the materials being processed. Current methods for detecting free radicals in a plasma require multiple expensive and bulky instruments, complex setups, and often, modifications to the plasma reactor. This work presents a simple technique that detects reactive-oxygen radicals incident on a surface from a plasma. The measurements are made using a fluorophore dye that is commonly used in biological and cellular systems for assay labeling in liquids. Using fluorometric analysis, it was found that the fluorophore reacts with oxygen radicals incident from the plasma, which is indicated by degradation of its fluorescence. As plasma power was increased, the quenching of the fluorescence significantly increased. Both immobilized and nonimmobilized fluorophore dyes were used and the results indicate that both states function effectively under vacuum conditions. The reaction mechanism is very similar to that of the liquid dye.

  17. Simulation Study of an Extended Density DC Glow Toroidal Plasma Source

    SciTech Connect

    Granda-Gutierrez, E. E.; Piedad-Beneitez, A. de la; Lopez-Callejas, R.; Godoy-Cabrera, O. G.; Benitez-Read, J. S.; Pacheco-Sotelo, J. O.; Pena-Eguiluz, R.; Mercado-Cabrera, A.; Valencia A, R.; Barocio, S. R.

    2006-12-04

    Conventional wisdom assigns the DC glow discharge regime to plasma currents below {approx}500 mA values, beyond which the discharge falls into the anomalous glow and the turbulent arc regimes. However, we have found evidence that, during toroidal discharges, this barrier can be ostensibly extended up to 800 mA. Thus, a computer simulation has been applied to the evolution of the main electrical characteristics of such a glow discharge plasma in a toroidal vessel in order to design and construct a respective voltage/current controlled source. This should be able to generate a DC plasma in the glow regime with which currents in the range 10-3-100 A can be experimented and 109-1010 cm-3 plasma densities can be achieved to PIII optimization purposes. The plasma is modelled as a voltage-controlled current source able to be turned on whenever the breakdown voltage is reached across the gap between the anode and the vessel wall. The simulation outcome fits well our experimental measurements showing that the plasma current obeys power laws that are dependent on the power current and other control variables such as the gas pressure.

  18. Numerical characterization of magnetized capacitively coupled argon plasmas driven by combined dc/rf sources

    NASA Astrophysics Data System (ADS)

    Yang, Shali; Zhang, Ya; Wang, Hong-Yu; Wang, Shuai; Jiang, Wei

    2017-03-01

    The characteristics of magnetized capacitively coupled plasmas (CCPs) driven by combined dc/rf sources in argon have been investigated by a one-dimensional implicit Particle-in-cell/Monte Carlo collision model. Discharges operating at 13.56 MHz with a fixed rf voltage of 300 V are simulated at the pressure of 50 mTorr in argon. Four cases, i.e., CCP driven by rf source, rf + dc sources, rf source with magnetic field, and rf + dc sources with magnetic field, are presented and compared at the Vdc = -100 V, B = 50 Gs, and γi = 0.2. It is found that, with the influence of dc voltage and magnetic field, the plasma density has been greatly enhanced by over one order of magnitude over the rf-only case. This is due to the fact that the mean free path of electrons decreases by the cyclotron motion and the energetic secondary electrons are trapped by the magnetic field, leading to a significant increase in heating and ionization rates. Moreover, transition of the stochastic to Ohmic electron heating mechanism takes place as the magnetic field increases because electron kinetics can be strongly affected by the magnetic field. In general, we have demonstrated that such a configuration will enhance the discharge and thus enable CCPs work under extremely high energy density stably that can never be operated by any other configurations. We expect that such a configuration can promote many related applications, like etching, sputtering, and deposition.

  19. Pulsed DC discharge for synthesis of conjugated plasma polymerized aniline thin film

    NASA Astrophysics Data System (ADS)

    Barman, Tapan; Pal, Arup R.

    2012-10-01

    The polymerization of aniline in pulsed dc plasma is studied and the effects of variation of pressure, power, frequency and duty cycle on the chemical structure of the obtained film are examined. During the film deposition optical emission spectroscopy is used to investigate the molecular dissociation of aniline. The chemical structure of the films is characterized using Fourier transform infra-red spectroscopy. The surface morphology is studied using atomic force microscopy. Results show the retention of polyaniline like structure having conjugated nature at some particular discharge conditions. Moreover, it is observed that a strong dependence of film chemistry is obvious on the discharge power, reactor pressure, pulse repetition frequency and duty cycle. The advantages of the pulsed dc for deposition of conjugated plasma polymerizes thin film have been highlighted.

  20. DC Electric Fields and Associated Plasma Drifts Observed with the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Bromund, K.; Rowland, D.

    2009-01-01

    Initial DC electric field observations and associated plasma drifts are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite. We present statistical averages of the vector fields for the first year of operations that include both the zonal and radial components of the resulting E x B plasma flows at low latitudes. Magnetic field data from the VEFI science magnetometer are used to compute the plasma flows. The DC electric field detector reveals zonal and radial electric fields that undergo strong diurnal variations, typically displaying eastward and outward-directed fields during the day and westward and downward-directed fields at night. There is considerable variation in the large scale DC electric field data, in both the daytime and nighttime cases, with enhanced structures typically observed at night. In general, the measured zonal DC electric field amplitudes include excursions that extend within the 0.4 - 2 m V/m range, corresponding to E x B drifts of the order of 30-150 m/s. The average vertical or radial electric fields may exceed the zonal fields in amplitude by a factor of 1.5 to 2. Although the data compare well, in a general sense, with previous satellite observations and statistical patterns of vertical ion drifts, the E x B drifts we report from C/NOFS rarely show a pronounced pre-reversal enhancement after sunset. We attribute this to a combination of extreme solar minimum conditions and the fact that the C/NOFS orbit of 401 by 867 km carries the probes essentially above the lower altitude regions where the wind-driven dynamo might be expected to create enhanced upwards drifts in the early evening. Evidence for wavenumber 4 tidal effects and other longitudinal signatures have been detected and will be presented. We also discuss off-equatorial electric fields and their relation to the ambient plasma density.

  1. Study on structural, morphological and thermal properties of surface modified polyvinylchloride (PVC) film under air, argon and oxygen discharge plasma

    NASA Astrophysics Data System (ADS)

    Suganya, Arjunan; Shanmugavelayutham, Gurusamy; Serra Rodríguez, Carmen

    2016-09-01

    The effect of air, argon, oxygen DC glow discharge plasma on the polyvinylchloride (PVC) film synthesized by solution casting technique, were evaluated via changes in physio-chemical properties such as structural, morphological, crystalline, thermal properties. The PVC film was plasma treated as a function of exposure time and different plasma forming gases, while other operating parameters such as power and pressure remained constant at 100 W and 2 Pa respectively. The plasma treated PVC were characterized by static contact angle, ATR-FTIR, XPS, AFM and T-peel analysis. It was found that various gaseous plasma treatments have improved the polar components, surface roughness on the surface of PVC which was confirmed by XPS, AFM, resulting in highly enhanced wettability and adhesion. X-ray diffraction study showed that plasma treatment does not persuade considerable change, even though it vaguely induces the crystallinity. The thermal properties of plasma treated PVC were evaluated by Differential Scanning Calorimetry and it was observed that O2 plasma treatment gives higher glass transition temperature of 87.21 °C compared with the untreated one. The glass transition temperature slightly increased for Oxygen plasma treated material due to the presence of higher concentration of the polar functional groups on the PVC surface due to strong intramolecular bonding.

  2. Band gap effects of hexagonal boron nitride using oxygen plasma

    SciTech Connect

    Sevak Singh, Ram; Leong Chow, Wai; Yingjie Tay, Roland; Hon Tsang, Siu; Mallick, Govind; Tong Teo, Edwin Hang

    2014-04-21

    Tuning of band gap of hexagonal boron nitride (h-BN) has been a challenging problem due to its inherent chemical stability and inertness. In this work, we report the changes in band gaps in a few layers of chemical vapor deposition processed as-grown h-BN using a simple oxygen plasma treatment. Optical absorption spectra show a trend of band gap narrowing monotonically from 6 eV of pristine h-BN to 4.31 eV when exposed to oxygen plasma for 12 s. The narrowing of band gap causes the reduction in electrical resistance by ∼100 fold. The x-ray photoelectron spectroscopy results of plasma treated hexagonal boron nitride surface show the predominant doping of oxygen for the nitrogen vacancy. Energy sub-band formations inside the band gap of h-BN, due to the incorporation of oxygen dopants, cause a red shift in absorption edge corresponding to the band gap narrowing.

  3. Study of dynamical behaviour of the plasma in a dc non-transferred plasma torch using fast imaging

    NASA Astrophysics Data System (ADS)

    Goyal, Vidhi; Ravi, G.; Bandyopadhyay, P.; Banerjee, S.; Yugesh, V.; Mukherjee, S.

    2017-03-01

    The dynamical behaviour of the plasma in a dc non-transferred plasma torch is the result of complex interactions between various forces acting on the plasma column. We have studied this behaviour in a novel experiment comprising a low power (˜25 kW) torch and fast imaging diagnostics. The nitrogen gas plasma torch was operated at atmospheric pressure for a wide range of gas flow rates (20-60 lpm) and currents (70-120 A). A strong axial external magnetic field (100-500 G) was introduced and end-on images of the plasma column were captured using a high speed camera of frame rate ˜117 000 fps. The studies have yielded dominant role of external magnetic on the arc root dynamics. The column is clearly distinguishable in three main parts: central plasma, cathode-anode junction, and radial component of column that attaches to the anode. The dynamics of the column, especially the angular rotational speed of the radial part of the column, is analyzed in detail in terms of the forces that act upon it. The nature of the arc root attachment is observed to vary with variation in main experimental parameters, such as current, magnetic field, and flow. Arguments are invoked to explain the observed phenomena and a model of the physical processes is presented to explain the phenomena.

  4. New perspectives on the dynamics of AC and DC plasma arcs exposed to cross-fields

    NASA Astrophysics Data System (ADS)

    Abdo, Youssef; Rohani, Vandad; Cauneau, François; Fulcheri, Laurent

    2017-02-01

    Interactions between an arc and external fields are crucially important for the design and the optimization of modern plasma torches. Multiple studies have been conducted to help better understand the behavior of DC and AC current arcs exposed to external and ‘self-induced’ magnetic fields, but the theoretical foundations remain very poorly explored. An analytical investigation has therefore been carried out in order to study the general behavior of DC and AC arcs under the effect of random cross-fields. A simple differential equation describing the general behavior of a planar DC or AC arc has been obtained. Several dimensionless numbers that depend primarily on arc and field parameters and the main arc characteristics (temperature, electric field strength) have also been determined. Their magnitude indicates the general tendency pattern of the arc evolution. The analytical results for many case studies have been validated using an MHD numerical model. The main purpose of this investigation was deriving a practical analytical model for the electric arc, rendering possible its stabilization and control, and the enhancement of the plasma torch power.

  5. Electrospray on superhydrophobic nozzles treated with argon and oxygen plasma

    NASA Astrophysics Data System (ADS)

    Byun, Doyoung; Lee, Youngjong; Tran, Si Bui Quang; Nugyen, Vu Dat; Kim, Sanghoon; Park, Baeho; Lee, Sukhan; Inamdar, Niraj; Bau, Haim H.

    2008-03-01

    We report on a simple process to fabricate electrohydrodynamic spraying devices with superhydrophobic nozzles. These devices are useful, among other things, in mass spectrometry and printing technology. The superhydrophobic nozzle is created by roughening the surface of the polyfluorotetraethylene (PTFE) by argon and oxygen plasma treatment. We have developed a polymer-based electrospray device with a flat, superhydrophobic nozzle capable of maintaining a high contact angle and stable jetting.

  6. Surface modification of polymers by atomic oxygen using ECR plasma

    NASA Astrophysics Data System (ADS)

    Abdul majeed, Riyadh M. A.; Datar, A.; Bhoraskar, S. V.; Bhoraskar, V. N.

    2007-05-01

    Polyimide (PI) and fluorinated ethylene propylene (FEP) samples were exposed to atomic oxygen ions of average energy ˜12 eV and flux ˜5 × 10 13 ions cm -2 s -1, produced in an ECR plasma. The fluence of the oxygen ions was varied from sample to sample over a range from ˜5 × 10 16 to 2 × 10 17 ions cm -2. The pre- and the post-irradiated samples were characterized by the contact angle, AFM and XPS techniques. The results indicate that the surface roughness of the polyimide increased from ˜7 to ˜65 nm, that of the FEP from ˜5 to ˜28 nm and the surface regions of both polyimide and FEP changed from hydrophobic to hydrophilic after exposure to atomic oxygen ions. The XPS results reveal that the concentrations of carbon, fluorine and oxygen changed even at a fluence of ˜10 17 ions cm -2 of the atomic oxygen ions. The results of the present study reveal that significant changes have been induced in the surface morphology and adhesion properties of polyimide and FEP after exposure to atomic oxygen ions.

  7. Production characteristics of reactive oxygen/nitrogen species in water using atmospheric pressure discharge plasmas

    NASA Astrophysics Data System (ADS)

    Takahashi, Kazuhiro; Satoh, Kohki; Itoh, Hidenori; Kawaguchi, Hideki; Timoshkin, Igor; Given, Martin; MacGregor, Scott

    2016-07-01

    A pulsed discharge, a DC corona discharge, and a plasma jet are separately generated above a water surface, and reactive oxygen species and reactive nitrogen species (ROS/RNS) in the water are investigated. ROS/RNS in water after the sparging of the off-gas of a packed-bed dielectric barrier discharge (PB-DBD) are also investigated. H2O2, NO2 -, and NO3 - are detected after plasma exposure and only NO3 - after off-gas sparging. Short-lifetime species in plasma are found to play an important role in H2O2 and NO2 - production and long-lifetime species in NO3 - production. NO x may inhibit H2O2 production through OH consumption to produce HNO2 and HNO3. O3 does not contribute to ROS/RNS production. The pulsed plasma exposure is found to be effective for the production of H2O2 and NO2 -, and the off-gas sparging of the PB-DBD for the production of NO3 -.

  8. Atomic Oxygen Energy in Low Frequency Hyperthermal Plasma Ashers

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; Miller, Sharon K R.; Kneubel, Christian A.

    2014-01-01

    Experimental and analytical analysis of the atomic oxygen erosion of pyrolytic graphite as well as Monte Carlo computational modeling of the erosion of Kapton H (DuPont, Wilmington, DE) polyimide was performed to determine the hyperthermal energy of low frequency (30 to 35 kHz) plasma ashers operating on air. It was concluded that hyperthermal energies in the range of 0.3 to 0.9 eV are produced in the low frequency air plasmas which results in texturing similar to that in low Earth orbit (LEO). Monte Carlo computational modeling also indicated that such low energy directed ions are fully capable of producing the experimentally observed textured surfaces in low frequency plasmas.

  9. Effects of Gas Flow Rate on the Discharge Characteristics of a DC Excited Plasma Jet

    NASA Astrophysics Data System (ADS)

    Li, Xuechen; Jia, Pengying; Di, Cong; Bao, Wenting; Zhang, Chunyan

    2015-09-01

    A direct current (DC) source excited plasma jet consisting of a hollow needle anode and a plate cathode has been developed to form a diffuse discharge plume in ambient air with flowing argon as the working gas. Using optical and electrical methods, the discharge characteristics are investigated for the diffuse plasma plume. Results indicate that the discharge has a pulse characteristic, under the excitation of a DC voltage. The discharge pulse corresponds to the propagation process of a plasma bullet travelling from the anode to the cathode. It is found that, with an increment of the gas flow rate, both the discharge plume length and the current peak value of the pulsed discharge decrease in the laminar flow mode, reach their minima at about 1.5 L/min, and then slightly increase in the turbulent mode. However, the frequency of the pulsed discharge increases in the laminar mode with increasing the argon flow rate until the argon flow rate equals to about 1.5 L/min, and then slightly decreases in the turbulent mode. supported by National Natural Science Foundation of China (Nos. 10805013, 11375051), Funds for Distinguished Young Scientists of Hebei Province, China (No. A2012201045), Department of Education for Outstanding Youth Project of China (No. Y2011120), and Youth Project of Hebei University of China (No. 2011Q14)

  10. Discharge modes of a DC operated atmospheric pressure air plasma jet

    NASA Astrophysics Data System (ADS)

    Kolb, Juergen; Pei, Xuekai; Kredl, Jana; Lu, Xinpei

    2016-09-01

    By flowing air or nitrogen through a microhollow cathode discharge geometry an afterglow plasma jet can be generated at atmospheric pressure in air. The plasma jet has been successfully used for the inactivation of bacteria and yeast. The responsible reaction chemistry is based on the production of high concentrations of nitric oxide. Production yields depend in particular on gas flow rate and energy dissipated in the plasma. The same parameters also determine different modes of operation for the jet. A true DC operation is achieved for low to moderate gas flow rate of about 1 slm and discharge currents on the order of 10 mA. When increasing the gas flow rate to 10 slm the operation is changing to a self-pulsing mode with characteristics similar to the ones observed for a transient spark. By increasing the current a DC operation can be achieved again also at higher gas flow rates. The parameter regimes for different modes of operation can be described by the reduced electric field E/N.

  11. Reactive oxygen species controllable non-thermal helium plasmas for evaluation of plasmid DNA strand breaks

    NASA Astrophysics Data System (ADS)

    Young Kim, Jae; Lee, Dong-Hoon; Ballato, John; Cao, Weiguo; Kim, Sung-O.

    2012-11-01

    Non-thermal, oxygen-rich helium plasmas were investigated to achieve an enhanced reactive oxygen species concentration at low voltage driving conditions. A non-thermal plasma device was fabricated based on a theta-shaped tube, and its potential was investigated for use in topological alteration of plasmid DNA. The optical emission spectra of the plasma showed that the oxygen flow affected the plasma properties, even though an oxygen plasma was not produced. The plasmid DNA strand breaks became more significant with the addition of oxygen flow to the helium in a single hollow, theta-shaped tube with other experimental conditions being unchanged.

  12. A low-energy linear oxygen plasma source

    SciTech Connect

    Anders, Andre; Yushkov, Georgy Yu.

    2007-01-08

    A new version of a Constricted Plasma Source is described,characterized by all metal-ceramic construction, a linear slit exit of180 mm length, and cw-operation (typically 50 kHz) at an average power of1.5 kW. The plasma source is here operated with oxygen gas, producingstreaming plasma that contains mainly positive molecular and atomic ions,and to a much lesser degree, negative ions. The maximum total ion currentobtained was about 0.5 A. The fraction of atomic ions reached more than10 percent of all ions when the flow rate was less then 10 sccm O2,corresponding to a chamber pressure of about 0.5 Pa for the selectedpumping speed. The energy distribution functions of the different ionspecies were measured with a combinedmass spectrometer and energyanalyzer. The time-averaged distribution functions were broad and rangedfrom about 30eV to 90 eV at 200 kHz and higher frequencies, while theywere only several eV broad at 50 kHz and lower frequencies, with themaximum located at about 40 eV for the grounded anode case. This maximumwas shifted down to about 7 eV when the anode was floating, indicatingthe important role of the plasma potential for the ion energy for a givensubstrate potential. The source could be scaled to greater length and maybe useful for functionalization of surfaces and plasma-assisteddeposition of compound films.

  13. Influence of injected silver content on synthesis of silver coated nickel particles by DC thermal plasma

    NASA Astrophysics Data System (ADS)

    Park, Si Taek; Kim, Tae-Hee; Park, Dong-Wha

    2016-06-01

    Silver nanoparticle-coated spherical nickel particles were prepared from a mixture of micro-sized silver and nickel as raw materials by DC thermal plasma treatment. The mixture of micro-sized silver and nickel powders was injected into the high-temperature region of an argon thermal plasma jet. Although the silver, with its very high thermal conductivity and relatively low boiling point, was thoroughly evaporated by this process, nickel was not evaporated perfectly because of its comparatively low thermal conductivity and high boiling point. The rough nickel powder was spheroidized as it melted. Finally, silver evaporated by the thermal plasma quickly condensed into nanoparticles on the surfaces of the micro-sized spherical nickel particles, aided by the sharp temperature gradient of the thermal plasma jet. With varying the ratios of silver to nickel feedstock from 1:10 to 5:1, the products synthesized in each condition were examined by XRD, XPS, FE-SEM, and FE-TEM. More silver nanoparticles were attached on the nickel by increasing the injected feedstock to 9.8 at% silver. Meanwhile, a decrease of silver in the products was observed when larger amounts of silver were introduced to the thermal plasma jet. The exposed silver components decreased with greater proportions of silver feedstock because of the metal's dendritic structure and the formation of silver-coated silver particles.

  14. Study on effect of plasma surface treatments for diamond deposition by DC arc plasmatron.

    PubMed

    Kang, In-Je; Joa, Sang-Beom; Lee, Heon-Ju

    2013-11-01

    To improve the thermal conductivity and wear resistance of ceramic materials in the field of renewable energy technologies, diamond coating by plasma processing has been carried out in recent years. This study's goal is to improve diamond deposition on Al2O3 ceramic substrates by plasma surface treatments. Before diamond deposition was carried out in a vacuum, plasma surface treatments using Ar gas were conducted to improve conditions for deposition. We also conducted plasma processing for diamond deposition on Al2O3 ceramic substrates using a DC arc Plasmatron. The Al2O3 ceramic substrates with diamond film (5 x 15 mm2), were investigated by SEM (Scanning Electron Microscopy), AFM (Atomic Force Microscopy) and XRD (X-ray Diffractometer). Then, the C-H stretching of synthetic diamond films by FTIR (Fourier Transform Infrared Spectroscopy) was studied. We identified nanocrystalline diamond films on the Al2O3 ceramic substrates. The results showed us that the deposition rate of diamond films was 2.3 microm/h after plasma surface treatments. Comparing the above result with untreated ceramic substrates, the deposition rate improved with the surface roughness of the deposited diamond films.

  15. Mixed mode oscillations in presence of inverted fireball in an excitable DC glow discharge magnetized plasma

    NASA Astrophysics Data System (ADS)

    Mitra, Vramori; Prakash, N. Hari; Solomon, Infant; Megalingam, Mariammal; Sekar Iyengar, A. N.; Marwan, Norbert; Kurths, Jürgen; Sarma, Arun; Sarma, Bornali

    2017-02-01

    The typical phenomena of mixed mode oscillations and their associated nonlinear behaviors have been investigated in collisionless magnetized plasma oscillations in a DC glow discharge plasma system. Plasma is produced between a cylindrical mesh grid and a constricted anode. A spherical mesh grid of 80% optical transparency is kept inside a cylindrical grid to produce an inverted fireball. Three Langmuir probes are kept in the ambient plasma to measure the floating potential fluctuations at different positions of the chamber. It has been observed that under certain conditions of discharge voltages and magnetic fields, the mixed mode oscillation phenomena (MMOs) appears, and it shows a sequential alteration with the variation of the magnetic fields and probe positions. Low frequency instability has been observed consistently in various experimental conditions. The mechanisms of the low frequency instabilities along with the origin of the MMOs have been qualitatively explained. Extensive linear and nonlinear analysis using techniques such as fast Fourier transform, recurrence quantification analysis, and the well-known statistical computing, skewness, and kurtosis are carried out to explore the complex dynamics of the MMO appearing in the plasma oscillations under various discharge conditions and external magnetic fields.

  16. Treatment Characteristics of Polysaccharides and Endotoxin Using Oxygen Plasma Produced by RF Discharge

    NASA Astrophysics Data System (ADS)

    Kitazaki, Satoshi; Hayashi, Nobuya; Goto, Masaaki

    2010-10-01

    Treatment of polysaccharides and endotoxin were attempted using oxygen plasma produced by RF discharge. Oxygen radicals observed by optical light emission spectra are factors of decomposition of polysaccharides and endotoxin. Fourier transform infrared spectra indicate that most of chemical bonds in the polysaccharides are dissociated after irradiation of the oxygen plasma. Also, the decomposition rate of endotoxin was approximately 90% after irradiation of the oxygen plasma for 180 min.

  17. Treatment Characteristics of Polysaccharides and Endotoxin Using Oxygen Plasma Produced by RF Discharge

    SciTech Connect

    Kitazaki, Satoshi; Hayashi, Nobuya; Goto, Masaaki

    2010-10-13

    Treatment of polysaccharides and endotoxin were attempted using oxygen plasma produced by RF discharge. Oxygen radicals observed by optical light emission spectra are factors of decomposition of polysaccharides and endotoxin. Fourier transform infrared spectra indicate that most of chemical bonds in the polysaccharides are dissociated after irradiation of the oxygen plasma. Also, the decomposition rate of endotoxin was approximately 90% after irradiation of the oxygen plasma for 180 min.

  18. Spectroscopic investigation of direct current (DC) plasma electrolytic oxidation of zirconium in citric acid.

    PubMed

    Stojadinović, Stevan; Radić-Perić, Jelena; Vasilić, Rastko; Perić, Miljenko

    2014-01-01

    Plasma electrolytic oxidation of zirconium in citric acid was investigated using optical spectroscopy. A rich emission spectrum consisting of about 360 zirconium and 170 oxygen atomic and ionic lines was identified in the spectral regions 313-320, 340-516, and 626-640 nm. It was shown that the remaining features observed in the spectrum could be ascribed to various molecular species, which involve zirconium, oxygen, hydrogen, and carbon. The temperature of the plasma core (T = 7500 ± 1000 K) was determined using measured Zr line intensities, and the temperature of peripheral plasma zone (T = 2800 ± 500 K) was estimated from the intensity distribution within a part of an OH spectrum. The composition of the plasma containing zirconium, oxygen, and hydrogen, under assumption of local thermal equilibrium, was calculated in the temperature range up to 12,000 K and for pressure of 10(5) and 10(7) Pa, in order to explain the appearance of the observed spectral features.

  19. The kinetics of energetic O‑ ions in oxygen discharge plasmas

    NASA Astrophysics Data System (ADS)

    Ponomarev, A. A.; Aleksandrov, N. L.

    2017-04-01

    Monte Carlo simulation was used to study the translational relaxation of energetic O‑ ions produced by dissociative electron attachment to O2 molecules in oxygen plasmas in a strong electric field. Initial O‑ ions have rather high energies and are more reactive than the ions reaching equilibrium with the electric field. Therefore, there is a noticeable probability that the energetic O‑ ions participate in endothermic reactions prior to energy relaxation of these ions. The probabilities of charge exchange, electron detachment and ion impact vibrational excitation of O2 molecules were calculated versus the reduced electric field. It was shown that up to 6% of energetic O‑ ions produced in oxygen by dissociative electron attachment to O2 molecules are rapidly transformed to {{{{O}}}2}- ions due to charge exchange collisions. The probability of electron detachment from energetic O‑ ions and the probability of vibrational excitation were smaller that the probability of charge exchange. Estimates showed that the increase in the effective rates of the ion–molecule reactions due to high reactivity of energetic O‑ ions can be important in oxygen plasmas for reduced electric fields of 50–100 Td.

  20. Structural and Dynamical Properties of Microrod Dusty Plasma in a Uniform DC Discharge under Microgravity

    SciTech Connect

    Usachev, Alexander; Zobnin, Andrey; Petrov, Oleg; Fortov, Vladimir

    2008-09-07

    In present experiment an ordering and dynamics of monodisperse nylon rods (D = 10 {mu}m, L = 300 {mu}m) in a uniform DC gas discharge plasma under microgravity have been investigated. Ordered rod structures were registered in DC discharge with a rod concentration of 400-8000 cm{sup -3} and a neon pressure range of 20-50 Pa. The structures revealed orientationally ordered hexagonal structures. DC discharge became unstable at rod number density more then 8000 cm{sup -3}. Rod drift velocities in a permanent electric field were measured for the neon pressure range. Dust acoustic instability ({nu}{approx}0.4{+-}0.1 Hz, {lambda}{approx}1.1{+-}0.4 cm, C{sub DAW}{approx}0.5 cm/s) in rod cloud was observed at a neon pressure of 25 Pa and a rod number density of 1500 cm{sup -3}. Using the 'low' frequency approximation of the linearized DAW dispersion relation and the measured rod drift velocity a rod electric charge had been estimated as Z{sub R}{approx}150000e.

  1. Desorption behavior of zinc atoms from zinc-sulfate solution irradiated with pulsed DC plasma

    NASA Astrophysics Data System (ADS)

    Takaba, Takafumi; Suzuki, Haruka; Toyoda, Hirotaka

    2016-07-01

    A DC pulsed plasma ignited between a metal needle and zinc sulfate (ZnSO4) solution electrode was used to investigate Zn metal desorption from an electrolyte solution. Using an ICCD camera and optical band-pass filter, 2D atomic absorption spectroscopy was carried out during irradiation of pulsed plasma to the surface of the solution. The time-resolved measurement of Zn atoms released to the gas phase revealed that the Zn desorption rate monotonically increased with increasing number of discharge repetitions. The surface temperature of the electrolyte solution was observed with a thermographic camera, and correlations between the H2O and Zn desorption rate were inspected. The correlation between the H2O and Zn desorption rate suggested that Zn desorption is assisted not only by the electric field of the discharge but also by H2O evaporating from the solution.

  2. Formation of ultrasharp vertically aligned Cu-Si nanocones by a DC plasma process.

    PubMed

    Klein, K L; Melechko, A V; Fowlkes, J D; Rack, P D; Hensley, D K; Meyer, H M; Allard, L F; McKnight, T E; Simpson, M L

    2006-03-16

    We report an effective method for the production of ultrasharp vertically oriented silicon nanocones with tip radii as small as 5 nm. These silicon nanostructures were shaped by a high-temperature acetylene and ammonia dc plasma reactive ion etch (RIE) process. Thin-film copper deposited onto Si substrates forms a copper silicide (Cu3Si) during plasma processing, which subsequently acts as a seed material masking the single-crystal cones while the exposed silicon areas are reactive ion etched. In this process, the cone angle is sharpened continually as the structure becomes taller. Furthermore, by lithographically defining the seed material as well as employing an etch barrier material such as titanium, the cone location and substrate topography can be controlled effectively.

  3. Inertization of heavy metals present in galvanic sludge by DC thermal plasma.

    PubMed

    Leal Vieira Cubas, Anelise; de Medeiros Machado, Marília; de Medeiros Machado, Marina; Gross, Frederico; Magnago, Rachel Faverzani; Moecke, Elisa Helena Siegel; Gonçalvez de Souza, Ivan

    2014-01-01

    Galvanic sludge results from the treatment of effluents generated by the industrial metal surface treatment of industrial material, which consists in the deposition of a metal on a surface or a metal surface attack, for example, electrodeposition of conductors (metals) and non conductive, phosphate, anodizing, oxidation and/or printed circuit. The treatment proposed here is exposure of the galvanic sludge to the high temperatures provided by thermal plasma, a process which aims to vitrify the galvanic sludge and render metals (iron, zinc, and chromium) inert. Two different plasma reactors were assembled: with a DC transferred arc plasma torch and with a DC nontransferred arc plasma torch. In this way it was possible to verify which reactor was more efficient in the inertization of the metals and also to investigate whether the addition of quartzite sand to the sludge influences the vitrification of the material. Quantification of water content and density of the galvanic raw sludge were performed, as well as analyzes of total organic carbon (TOC) and identify the elements that make up the raw sludge through spectroscopy X-ray fluorescence (XRF). The chemical composition and the form of the pyrolyzed and vitrified sludge were analyzed by scanning electron microscopy with energy-dispersive X-ray spectrometer (SEM-EDS) analysis, which it is a analysis that shows the chemical of the sample surface. The inertization of the sludge was verified in leaching tests, where the leachate was analyzed by flame atomic absorption spectroscopy (FAAS). The results of water content and density were 64.35% and 2.994 g.cm(-3), respectively. The TOC analysis determined 1.73% of C in the sample of galvanic raw sludge, and XRF analysis determined the most stable elements in the sample, and showed the highest peaks (higher stability) were Fe, Zn, and Cr. The efficiency of the sludge inertization was 100% for chromium, 99% for zinc, and 100% for iron. The results also showed that the most

  4. Structured DC Electric Fields With and Without Associated Plasma Density Gradients Observed with the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Rowland, D.; Klenzing, J.; Freudenreich, H.; Bromund, K.; Liebrecht, C.; Roddy, P.; Hunton, D.

    2009-01-01

    DC electric field observations and associated plasma drifts gathered with the Vector Electric Field Investigation on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite typically reveal considerable variation at large scales (approximately 100's of km), in both daytime and nighttime cases, with enhanced structures usually confined to the nightside. Although such electric field structures are typically associated with plasma density depletions and structures, as observed by the Planar Langmuir Probe on C/NOFS, what is surprising is the number of cases in which large amplitude, structured DC electric fields are observed without a significant plasma density counterpart structure, including their appearance at times when the ambient plasma density appears relatively quiescent. We investigate the relationship of such structured DC electric fields and the ambient plasma density in the C/NOFS satellite measurements observed thus far, taking into account both plasma density depletions and enhancements. We investigate the mapping of the electric fields along magnetic field lines from distant altitudes and latitudes to locations where the density structures, which presumably formed the original seat of the electric fields, are no longer discernible in the observations. In some cases, the electric field structures and spectral characteristics appear to mimic those associated with equatorial spread-F processes, providing important clues to their origins. We examine altitude, seasonal, and longitudinal effects in an effort to establish the origin of such structured DC electric fields observed both with, and without, associated plasma density gradients

  5. DC Electric Fields, Associated Plasma Drifts, and Irregularities Observed on the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Klenzing, J.

    2011-01-01

    Results are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite, a mission designed to understand, model, and forecast the presence of equatorial ionospheric irregularities. The VEFI instrument includes a vector DC electric field detector, a fixed-bias Langmuir probe operating in the ion saturation regime, a flux gate magnetometer, an optical lightning detector, and associated electronics including a burst memory. Compared to data obtained during more active solar conditions, the ambient DC electric fields and their associated E x B drifts are variable and somewhat weak, typically < 1 mV/m. Although average drift directions show similarities to those previously reported, eastward/outward during day and westward/downward at night, this pattern varies significantly with longitude and is not always present. Daytime vertical drifts near the magnetic equator are largest after sunrise, with smaller average velocities after noon. Little or no pre-reversal enhancement in the vertical drift near sunset is observed, attributable to the solar minimum conditions creating a much reduced neutral dynamo at the satellite altitude. The nighttime ionosphere is characterized by larger amplitude, structured electric fields, even where the plasma density appears nearly quiescent. Data from successive orbits reveal that the vertical drifts and plasma density are both clearly organized with longitude. The spread-F density depletions and corresponding electric fields that have been detected thus far have displayed a preponderance to appear between midnight and dawn. Associated with the narrow plasma depletions that are detected are broad spectra of electric field and plasma density irregularities for which a full vector set of measurements is available for detailed study. The VEFI data represents a new set of measurements that are germane to numerous fundamental aspects of the electrodynamics

  6. Synthesis of silicon carbide from rice husk in a dc arc plasma reactor

    SciTech Connect

    Nayak, B.B.; Mohanty, B.C.; Singh, S.K.

    1996-05-01

    SiC particles have been synthesized in the {alpha}-phase from a mixture of boiler-burnt rice husk and graphite powder in a dc extended arc plasma reactor on a 200--250 g scale. A SiC yield as high as 72% was achieved at a 3.03:1 carbon-to-silica ratio. 21R polytypism, which is rare to grow, was observed in the SiC. About 90% of the SiC particles produced were found to lie under 163 {micro}m, 50% under 90 {micro}m, and 10% under 28 {micro}m size. Very fine particles under 10 {micro}m size occurred to the extent of 3%. XRD and SEM characterizations were carried out to study the phase and morphology of the particles. Heterogeneous gas-phase reactions seem to be responsible for intermediate-size SiC particle growth in the multitemperature zone dc extended arc plasma reactor.

  7. Production of geopolymers using glass produced from DC plasma treatment of air pollution control (APC) residues.

    PubMed

    Kourti, Ioanna; Rani, D Amutha; Deegan, D; Boccaccini, A R; Cheeseman, C R

    2010-04-15

    Air pollution control (APC) residues are the hazardous waste produced from cleaning gaseous emissions at energy-from-waste (EfW) facilities processing municipal solid waste (MSW). APC residues have been blended with glass-forming additives and treated using DC plasma technology to produce a high calcium alumino-silicate glass. This research has investigated the optimisation and properties of geopolymers prepared from this glass. Work has shown that high strength geopolymers can be formed and that the NaOH concentration of the activating solution significantly affects the properties. The broad particle size distribution of the APC residue glass used in these experiments results in a microstructure that contains unreacted glass particles included within a geopolymer binder phase. The high calcium content of APC residues may cause the formation of some amorphous calcium silicate hydrate (C-S-H) gel. A mix prepared with S/L=3.4, Si/Al=2.6 and [NaOH]=6M in the activating solution, produced high strength geopolymers with compressive strengths of approximately 130 MPa. This material had high density (2070 kg/m(3)) and low porosity. The research demonstrates for the first time that glass derived from DC plasma treatment of APC residues can be used to form high strength geopolymer-glass composites that have potential for use in a range of applications.

  8. Transient electromagnetic behaviour in inductive oxygen and argon-oxygen plasmas

    NASA Astrophysics Data System (ADS)

    Chadwick, A. R.; Herdrich, G.; Kim, M.; Dally, B.

    2016-12-01

    In order to develop inductive electric propulsion as a flexible, throttleable technology for future space operations, a greater understanding of discharge transitions within the inductive plasma generator discharge chamber is required. This paper presents a non-intrusive method to determine the conditions under which transitions between the capacitive, low inductive, and high inductive regimes occur with greater accuracy, as well as determining the proportion of a single discharge cycle the plasma spends in either capacitive or inductive regime. Such a method allows a more robust method of classification of inductive discharges than previously available and can be applied to numerous gases. This approach presents an advantage over previous methods which relied on strongly radiating or thermally reactive gases to exhibit certain behaviour (due to the restriction of classical diagnostics on such high power sources) before a transition could be confirmed. This paper presents results from the proposed method applied to a pure oxygen plasma as well as two combinations of argon and oxygen (at 1:1 and 3:2 Ar:O2 volumetric ratios) in order to assess the tunability of electromagnetic regime transitions through modifications of gas composition rather than mechanical alterations. Transitions to the higher inductive mode were observed for much lower input powers for the argon-oxygen blends, as was expected, allowing final discharge conditions to occupy the inductive regime for 94% and 85% of a single discharge cycle for the 3:2 and 1:1 Ar:O2 mixtures, respectively. Pure oxygen achieved a maximum inductive proportion of 71% by comparison.

  9. Plasma kinetic processes in a strong d.c. magnetic field

    NASA Technical Reports Server (NTRS)

    Montgomery, D.

    1976-01-01

    Recent results in the kinetic theory of a strongly magnetized plasma are surveyed. Emphasis is on the electrostatic guiding-center plasma in two dimensions, in both the fluid and 'charged rod' descriptions. The basic kinetic description of the plasma is in terms of the statistically-distributed Fourier coefficients associated with the velocity and 'enstrophy' (charge density) fields. It is a universal tendency in such media for enstrophy to flow to shorter wavelengths but for energy to flow to longer wavelengths. A consequence of the energy flow to longer wavelengths is the generation of long-range order in the form of macroscopic vortices. These kinds of structure have been called 'convection cells' and can be extraordinarily efficient in transporting particles transverse to a magnetic field. The tendency to vortex formation can be disrupted by collisions between particles. Modifications of the Fokker-Planck equation for a plasma produced by a strong dc magnetic field are considered in both two and three dimensions.

  10. Coal pyrolysis to acetylene using dc hydrogen plasma torch: effects of system variables on acetylene concentration

    NASA Astrophysics Data System (ADS)

    Chen, Longwei; Meng, Yuedong; Shen, Jie; Shu, Xingsheng; Fang, Shidong; Xiong, Xinyang

    2009-03-01

    In order to unveil the inner mechanisms that determine acetylene concentration, experimental studies on the effect of several parameters such as plasma torch power, hydrogen flux and coal flux were carried out from coal pyrolysis in a dc plasma torch. Xinjiang long flame coals including volatile constituents at a level of about 42% were used in the experiment. Under the following experimental conditions, namely plasma torch power, hydrogen flow rate and pulverized coal feed speed of 2.12 MW, 32 kg h-1 and 900 kg h-1, respectively, acetylene volume concentration of about 9.4% was achieved. The experimental results indicate that parameters such as plasma torch power and coal flux play important roles in the formation of acetylene. Acetylene concentration increases inconspicuously with hydrogen flux. A chemical thermodynamic equilibrium model using the free energy method is introduced in this paper to numerically simulate each experimental condition. The numerical results are qualitatively consistent with the experimental results. Two parameters, i.e. the gas temperature and the ratio of hydrogen/carbon, are considered to be the dominant and independent factors that determine acetylene concentration.

  11. Plasma parameters of pulsed-dc discharges in methane used to deposit diamondlike carbon films

    SciTech Connect

    Corbella, C.; Rubio-Roy, M.; Bertran, E.; Andujar, J. L.

    2009-08-01

    Here we approximate the plasma kinetics responsible for diamondlike carbon (DLC) depositions that result from pulsed-dc discharges. The DLC films were deposited at room temperature by plasma-enhanced chemical vapor deposition (PECVD) in a methane (CH{sub 4}) atmosphere at 10 Pa. We compared the plasma characteristics of asymmetric bipolar pulsed-dc discharges at 100 kHz to those produced by a radio frequency (rf) source. The electrical discharges were monitored by a computer-controlled Langmuir probe operating in time-resolved mode. The acquisition system provided the intensity-voltage (I-V) characteristics with a time resolution of 1 mus. This facilitated the discussion of the variation in plasma parameters within a pulse cycle as a function of the pulse waveform and the peak voltage. The electron distribution was clearly divided into high- and low-energy Maxwellian populations of electrons (a bi-Maxwellian population) at the beginning of the negative voltage region of the pulse. We ascribe this to intense stochastic heating due to the rapid advancing of the sheath edge. The hot population had an electron temperature T{sub e}{sup hot} of over 10 eV and an initial low density n{sub e}{sup hot} which decreased to zero. Cold electrons of temperature T{sub e}{sup cold}approx1 eV represented the majority of each discharge. The density of cold electrons n{sub e}{sup cold} showed a monotonic increase over time within the negative pulse, peaking at almost 7x10{sup 10} cm{sup -3}, corresponding to the cooling of the hot electrons. The plasma potential V{sub p} of approx30 V underwent a smooth increase during the pulse and fell at the end of the negative region. Different rates of CH{sub 4} conversion were calculated from the DLC deposition rate. These were explained in terms of the specific activation energy E{sub a} and the conversion factor x{sub dep} associated with the plasma processes. The work deepens our understanding of the advantages of using pulsed power supplies

  12. Ground-Laboratory to In-Space Effective Atomic-Oxygen Fluence Determined for DC 93-500 Silicone

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Banks, Bruce A.; Ma, David

    2005-01-01

    Surfaces on the leading edge of spacecraft in low Earth orbit (e.g., surface facing the velocity direction), such as on the International Space Station, are subject to atomic oxygen attack, and certain materials are susceptible to erosion. Therefore, ground-based laboratory testing of the atomic oxygen durability of spacecraft materials is necessary for durability assessment when flight data are not available. For accurate space simulation, the facility is commonly calibrated on the basis of the mass loss of Kapton (DuPont, Wilmington, DE) as a control sample for effective fluence determination. This is because Kapton has a well-characterized atomic oxygen erosion yield (E(sub y), in cubic centimeters per atom) in the low Earth orbit (LEO) environment. Silicones, a family of commonly used spacecraft materials, do not chemically erode away with atomic oxygen attack like other organic materials that have volatile oxidation products. Instead, silicones react with atomic oxygen and form an oxidized hardened silicate surface layer. Often the loss of methyl groups causes shrinkage of the surface skin and "mud-tile" crazing degradation. But silicones often do not lose mass, and some silicones actually gain mass during atomic oxygen exposure. Therefore, the effective atomic oxygen fluence for silicones in a ground-test facility should not be determined on the basis of traditional mass-loss measurements, as it is with polymers that erode. Another method for determining effective fluence needs to be employed for silicones. A new technique has been developed at the NASA Glenn Research Center for determining the effective atomic oxygen fluence for silicones in ground-test facilities. This technique determines the equivalent amount of atomic oxygen oxidation on the basis of changes in the surface-oxide hardness. The specific approach developed was to compare changes in the surface hardness of ground-laboratory-exposed DC93-500 silicone with DC93-500 exposed to LEO atomic oxygen

  13. Interaction of non-equilibrium oxygen plasma with sintered graphite

    NASA Astrophysics Data System (ADS)

    Cvelbar, Uroš

    2013-03-01

    Samples made from sintered graphite with grain size of about 10 μm were exposed to highly non-equilibrium oxygen plasma created in a borosilicate glass tube by an electrodeless RF discharge. The density of charged particles was about 7 × 1015 m-3 and the neutral oxygen atom density 6 × 1021 m-3. The sample temperature was determined by a calibrated IR detector while the surface modifications were quantified by XPS and water drop techniques. The sample surface was rapidly saturated with carbonyl groups. Prolonged treatment of samples caused a decrease in concentration of the groups what was explained by thermal destruction. Therefore, the created functional groups were temperature dependent. The heating of samples resulted in extensive chemical interaction between the O atoms and samples what was best monitored by decreasing of the O atom density with increasing sample temperature. The saturation with functional groups could be restored only after cooling down of the samples and repeated short plasma treatment at low temperature.

  14. Geopolymers prepared from DC plasma treated air pollution control (APC) residues glass: properties and characterisation of the binder phase.

    PubMed

    Kourti, Ioanna; Devaraj, Amutha Rani; Bustos, Ana Guerrero; Deegan, David; Boccaccini, Aldo R; Cheeseman, Christopher R

    2011-11-30

    Air pollution control (APC) residues have been blended with glass-forming additives and treated using DC plasma technology to produce a high calcium aluminosilicate glass (APC glass). This has been used to form geopolymer-glass composites that exhibit high strength and density, low porosity, low water absorption, low leaching and high acid resistance. The composites have a microstructure consisting of un-reacted residual APC glass particles imbedded in a complex geopolymer and C-S-H gel binder phase, and behave as particle reinforced composites. The work demonstrates that materials prepared from DC plasma treated APC residues have potential to be used to form high quality pre-cast products.

  15. Influence of a transverse magnetic field on arc root movements in a dc plasma torch: Diamagnetic effect of arc column

    SciTech Connect

    Kim, Keun Su

    2009-03-23

    The effect of a transverse magnetic field on the anodic arc root movement inside a dc plasma torch has been investigated. The arc voltage fluctuation, which represents the degree of the arc instability, was reduced to 28.6% of the original value and the high frequency components in the voltage signal also decreased in their magnitudes. The inherent arc instability in a dc thermal plasma torch seems to be suppressed by a diamagnetic effect of the arc column. Furthermore, the measured voltage wave forms indicated that the arc root attachment mode would be controllable by a transverse magnetic field.

  16. Influence of absolute argon and oxygen flow values at a constant ratio on the growth of Zn/ZnO nanostructures obtained by DC reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Masłyk, M.; Borysiewicz, M. A.; Wzorek, M.; Wojciechowski, T.; Kwoka, M.; Kamińska, E.

    2016-12-01

    In the present work we analyze the growth mechanism of Zn/ZnO nanostructured thin films obtained by DC reactive magnetron sputtering with variable absolute gas flow values. Zn target was sputtered at 80 W DC power with variable absolute Ar:O2 flow values at a set ratio, in sccm: 3:0.3, 6:0.6, 8:0.8, 10:1, 15:1.5, 20:2 and 30:3. We obtained unique Zn/ZnO nanoflowers with morphology and properties changing as a function of gas flow values from dendritic/nanopetal structures for low flow to dense porous films for high flow. Zn core/ZnO shell composition results from surface oxidation of Zn crystallites to 4 nm thick ZnO after exposure to atmospheric air that causes an increase in resistivity especially for denser, more porous films. Taking into account that the plasma properties measures using the Langmuir probe and optical emission spectroscopy remain constant as a function of gas flow values, we put forward that the structural evolution of films is influenced by oxygen incorporating into the film surface acting as an inhibitor - incorporating into the films and decreasing crystallite sizes and amorphizing the film structure.

  17. A study of the transient plasma potential in a pulsed bi-polar dc magnetron discharge

    NASA Astrophysics Data System (ADS)

    Bradley, J. W.; Karkari, S. K.; Vetushka, A.

    2004-05-01

    The temporal evolution of the plasma potential, Vp, in a pulsed dc magnetron plasma has been determined using the emissive probe technique. The discharge was operated in the 'asymmetric bi-polar' mode, in which the discharge voltage changes polarity during part of the pulse cycle. The probe measurements, with a time-resolution of 20 ns or better, were made along a line above the racetrack, normal to the plane of the cathode target, for a fixed frequency (100 kHz), duty cycle (50%), argon pressure (0.74 Pa) and discharge power (583 W). At all the measured positions, Vp was found to respond to the large and rapid changes in the cathode voltage, Vd, during the different phases of the pulse cycle, with Vp always more positive than Vd. At a typical substrate position (>80 mm from the target), Vp remains a few volts above the most positive surface in the discharge at all times. In the 'on' phase of the pulse, the measurements show a significant axial electric field is generated in the plasma, with the plasma potential dropping by a total of about 30 V over a distance of 70 mm, from the bulk plasma to a position close to the beginning of the cathode fall. This is consistent with measurements made in the dc magnetron. During the stable 'reverse' phase of the discharge, for distances greater than 18 mm from the target, the axial electric field is found to collapse, with Vp elevated uniformly to about 3 V above Vd. Between the target and this field-free region an ion sheath forms, and the current flowing to the target is still an ion current in this 'reverse' period. During the initial 200 ns of the voltage 'overshoot' phase (between 'on' and 'reverse' phases), Vd reached a potential of +290 V; however, close to the target, Vp was found to attain a much higher value, namely +378 V. Along the line of measurement, the axial electric field reverses in direction in this phase, and an electron current of up to 9 A flows to the target. The spatial and temporal measurements of Vp

  18. Dynamics of a pulsed inductively coupled oxygen plasma

    NASA Astrophysics Data System (ADS)

    Zaka-ul-Islam, Mujahid

    2016-11-01

    Inductively coupled plasma system (ICPs) is extensively used for a wide range of nanofabrication applications. The ICPs operated in a pulsed or power modulated mode has shown several advantages compared to the continuous discharge. In this work, the plasma dynamics in a planar coil pulsed inductively coupled plasma system (ICPs) operated in oxygen has been investigated, using phase and space resolved optical emission spectroscopy. It is well-known that the ICPs operates in two distinct operational modes as a function of power known as E and H modes, generated dominantly by capacitive and inductive couplings, respectively. The measurements show that the discharge ignites due a capacitive coupling (in the E-mode) and later transits to the H-mode as a function of time. The inductive coupling, however, starts during the E-mode along with capacitive coupling. The relative contribution of inductive coupling increases until the discharge reaches the E-H transition where the growth rate of inductive coupling becomes much faster. It is found that the time to reach E-H transition decreases with the pressure. At the E-H transition, the total emission has a spike-like feature (i.e., it first achieves a peak emission which later decreases and finally settles to a lower value). The 2D images of the discharge show that at the time of peak total-emission, the discharge structure is sharp and bright, which later decreases in brightness and becomes diffusive.

  19. Effects of edge dc biasing on plasma rotation and transport in a toroidal geometry

    NASA Astrophysics Data System (ADS)

    Fredriksen, Åshild; Riccardi, Claudia; Magni, Simone

    2006-02-01

    We report results from experiments performed to study how a change in boundary conditions affects the plasma state in the toroidal geometry of the Blaamann device in Tromso. The boundary condition was changed by applying a dc bias on a limiter extended around the entire poloidal circumference of the plasma column. Two distinctly different plasma potential states were found. One state was associated with a bias at or negative with respect to the floating potential of the limiter, and a small ion-saturation current. The other state was associated with a positive bias with respect to the floating potential, near or in the electron saturation regime of the limiter. In the latter case the potential minimum in the middle of the cross-section was significantly less negative than in the case of ion-saturation current to the limiter. On the other hand, the grounded limiter provided the best confinement properties, for which the density maximum was significantly higher than for both more positive and more negative biases. This state also had the lowest fluctuation levels, and near zero poloidal velocities close to the boundaries, as well as the smallest radial, anomalous particle transport.

  20. Effects of Edge DC Biasing on Plasma Rotation and Transport in a Toroidal Geometry.

    NASA Astrophysics Data System (ADS)

    Fredriksen, Ashild; Riccardi, Claudia

    2005-10-01

    We report results from experiments performed to study how a change in boundary conditions is affecting the plasma states in the toroidal geometry of the Blaamann device in Tromso. The boundary condition was changed by applying a DC bias on a limiter extended around the entire poloidal circumference of the plasma column. Two distinctly different plasma potential states were found. One state was associated with a bias at or negative with respect to the floating potential of the limiter, and a small ion saturation current. The other state was associated with a positive bias with respect to the floating potential, near or in the electron saturation regime of the limiter. In the latter case the potential minimum in the middle of the cross-section was significantly less negative than in the case of ion-saturation current to the limiter. On the other hand, the grounded limiter provided the best confinement properties, for which the density maximum was significantly higher than for both more positive and more negative biases. This state also had the lowest fluctuation levels, and near zero poloidal velocities close to the boundaries, as well as the smallest radial, anomalous particle transport.

  1. Interaction of DC Microhollow Cathode Discharge Plasma Micro Jet with Liquid Media

    NASA Astrophysics Data System (ADS)

    Zhu, Weidong; Lopez, Jose; Becker, Kurt

    2008-10-01

    There have been different approaches in studying the interaction between plasma and liquid, such as sustained plasmas in contact with liquids and pulsed electric discharge in liquids. Recently, we have discovered that stable plasma can be sustained within a gas cavity maintained inside liquid media. A prototype device with key dimensions in sub-millimeter range were operated successfully in de-ionized water and turbo molecular pump oil with ambient air, pure nitrogen or pure oxygen used as the operating gas. Hydrogen Peroxide production in de-ionized water with ambient air as the working gas is estimated to be about 80 mg/L after 15 minutes plasma jet-water interaction while energy consumption is only about 8-10 W. With the radicals readily generated and directly introduced into the liquid media, it could lead to applications such as in-liquid bio-waste treatment, bio-rich liquid modification, in-situ monitoring/sensing, and filtration of by-products from VOC treatment by plasma.

  2. Studies on the room temperature growth of nanoanatase phase TiO2 thin films by pulsed dc magnetron with oxygen as sputter gas

    NASA Astrophysics Data System (ADS)

    Karuppasamy, A.; Subrahmanyam, A.

    2007-03-01

    The anatase phase titanium dioxide (TiO2) thin films were deposited at room temperature by pulsed dc magnetron sputtering using pure oxygen as sputter gas. The structural, optical, electrical, and electrochromic properties of the films have been studied as a function of oxygen pressure in the chamber. The x-ray diffraction results indicate that the films grown above 4.5×10-2mbar are nanocrystalline (grain size of 28-43nm) with anatase phase. The films deposited at the chamber pressure of 7.2×10-2mbar are found to be highly crystalline with a direct optical band gap of 3.40eV, refractive index of 2.54 (at λ =400nm), and work function of 4.77eV (determined by the Kelvin probe measurements). From the optical emission spectra of the plasma and transport of ions in matter calculations, we find that the crystallization of TiO2 at room temperature is due to the impingement of electrons and ions on the growing films. Particularly, the negative oxygen ions reflected from the target by "negative ion effects" and the enhanced density of TiO, TiO +, TiO2+, and O2+ particles in the plasma are found to improve the crystallization even at a relatively low temperature. From an application point of view, the film grown at 7.2×10-2mbar was studied for its electrochromic properties by protonic intercalation. It showed good electrochromic behavior with an optical modulation of ˜45%, coloration efficiency of 14.7 cm2C-1, and switching time (tc) of 50s for a 2×2 cm2 device at λ =633nm.

  3. Experimental and Theoretical Estimation of Excited Species Generation in Pulsed Electron Beam-Generated Plasmas Produced in Pure Argon, Nitrogen, Oxygen, and Their Mixtures

    DTIC Science & Technology

    2011-05-13

    Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6750--11-9333 Experimental and Theoretical Estimation of Excited Species Generation in ...Pulsed Electron Beam–Generated Plasmas Produced in Pure Argon, Nitrogen, Oxygen, and Their Mixtures May 13, 2011 Approved for public release...PAGE 18. NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Experimental and Theoretical Estimation of Excited Species Generation in Pulsed Electron Beam

  4. Characterization of undoped and Co doped ZnO nanoparticles synthesized by DC thermal plasma method

    NASA Astrophysics Data System (ADS)

    Nirmala, M.; Anukaliani, A.

    2011-02-01

    ZnO nanopowders doped with 5 and 10 at% cobalt were synthesized and their antibacterial activity was studied. Cobalt doped ZnO powders were prepared using dc thermal plasma method. Crystal structure and grain size of the particles were characterized by X-ray diffractometry and optical properties were studied using UV-vis spectroscopy. The particle size and morphology was observed by SEM and HRTEM, revealing rod like morphology. The antibacterial activity of undoped ZnO and cobalt doped ZnO nanoparticles against a Gram-negative bacterium Escherichia coli and a Gram-positive bacterium Bacillus atrophaeus was investigated. Undoped ZnO and cobalt doped ZnO exhibited antibacterial activity against both E. coli and Staphylococcus aureus but it was considerably more effective in the cobalt doped ZnO.

  5. Sterilization Effect of Wet Oxygen Plasma in the Bubbling Method.

    PubMed

    Tamazawa, Kaoru; Shintani, Hideharu; Tamazawa, Yoshinori; Shimauchi, Hidetoshi

    2015-01-01

    A new low-temperature sterilization method to replace the ethylene oxide gas sterilization is needed. Strong bactericidal effects of OH and O2H radicals are well known. The purpose of this study was to evaluate the sterilization effect of wet oxygen ("O2+H2O") plasma in the bubbling method, confirming the effect of humidity. Sterility assurance was confirmed by using a biological indicator (Geobacillus stearothermophilus ATCC7953, Namsa, USA). One hundred and eight samples (10(5) spores/carrier) were divided into three groups of 36 in each for treatment with a different type of gas (O2, O2+H2O, Air+H2O). Plasma processing was conducted using a plasma ashing apparatus (13.56 MHz, PACK-3(®), Y. A. C., Japan) under various gas pressures (13, 25, 50 Pa) and gas flows (50, 100, 200 sccm). Fixed plasma treatment parameters were power at 150 W, temperature of 60 ℃, treatment time of 10 min. The samples after treatment were incubated in trypticase soy broth at 58 ℃ for 72 h. The negative culture rate in the "O2+H2O" group was significantly (Mantel-Haenszel procedure, p<0.001) higher than in the other gas groups. It is suggested that the significant sterilization effect of the "O2+H2O" group depends on the bubbling method which is the method of introducing vapor into the chamber. The bubbling method seems able to generate OH and O2H radicals in a stable way.

  6. Dusty plasma microparticle cloud control and rapid electrostatic mutual-repulsion expansion in a DC glow discharge

    NASA Astrophysics Data System (ADS)

    Gillman, Eric; Amatucci, Bill

    2016-10-01

    Microparticles in plasma discharges rapidly charge up, typically collecting a net negative charge due to the relatively high mobility of electrons compared to ions. Electrostatic forces can be utilized to control charged microparticle behavior and motion in a plasma discharge. In these experiments a metal wire loop is supplied with an electric potential that can be controlled independently from the DC plasma glow discharge electrodes. By varying the voltage on the wire loop, we can attract, trap, manipulate, suspend, and/or repel microparticles that originate from the DC glow discharge. Experiments studied the properties of electrostatic self-repulsion of a cloud of charged microparticles. By pulsing the plasma and controlling wire loop potential, a cloud of trapped microparticles is released and allowed to rapidly expand. A simple force balance simulation code is used as a model to compare and benchmark actual experimental results. This work was supported by the Naval Research Laboratory base program.

  7. Evolution of an electron energy distribution function in a weak dc magnetic field in solenoidal inductive plasma

    SciTech Connect

    Lee, Min-Hyong; Choi, Seong Wook

    2008-12-01

    We investigated the evolution of the electron energy distribution function (EEDF) in a solenoidal inductively coupled plasma surrounded by an axial dc magnetic field. The increase in the dc magnetic field caused the EEDF to evolve from a bi-Maxwellian to a Maxwellian distribution. At the discharge center, the number of low energy electrons was significantly reduced while the high energy electron population showed little change when a weak dc magnetic field was present. However, at the discharge radial boundary, the high energy electron population decreased significantly with the magnetic field while the change in low energy population was not prominent compared to the discharge boundary. These changes in EEDFs at the boundary and center of the discharge are due to the radial confinement and the restriction of radial transport of electrons by dc magnetic field.

  8. Mechanisms of polymer degradation using an oxygen plasma generator

    NASA Technical Reports Server (NTRS)

    Colony, Joe A.; Sanford, Edward L.

    1987-01-01

    An RF oxygen plasma generator was used to produce polymer degradation which appears to be similar to that which has been observed in low Earth orbit. Mechanisms of this type of degradation were studied by collecting the reaction products in a cryogenic trap and identifying the molecular species using infrared, mass spectral, and X-ray diffraction techniques. No structurally dependent species were found from Kapton, Teflon, or Saran polymers. However, very reactive free radical entities are produced during the polymer degradation, as well as carbon dioxide and water. Reactions of the free radicals with the glass reaction vessel, with copper metal in the cold trap, and with a triphenyl phosphate scavenger in the cold trap, demonstrated the reactivity of the primary products.

  9. Tunable optical absorption and interactions in graphene via oxygen plasma

    NASA Astrophysics Data System (ADS)

    Santoso, Iman; Singh, Ram Sevak; Gogoi, Pranjal Kumar; Asmara, Teguh Citra; Wei, Dacheng; Chen, Wei; Wee, Andrew T. S.; Pereira, Vitor M.; Rusydi, Andrivo

    2014-02-01

    We report significant changes of optical conductivity (σ1) in single-layer graphene induced by mild oxygen plasma exposure and explore the interplay between carrier doping, disorder, and many-body interactions from their signatures in the absorption spectrum. The first distinctive effect is the reduction of the excitonic binding energy that can be extracted from the renormalized saddle point resonance at 4.64 eV. Secondly, σ1 is nearly completely suppressed (σ1≪σ0) below an exposure-dependent threshold in the near-infrared range. The clear steplike suppression follows the Pauli blocking behavior expected for doped monolayer graphene. The nearly zero residual conductivity below ω ˜ 2EF can be interpreted as arising from the weakening of the electronic self-energy. Our data shows that mild oxygen exposure can be used to controllably dope graphene without introducing the strong physical and chemical changes that are common in other approaches to oxidized graphene, allowing a controllable manipulation of the optical properties of graphene.

  10. Effect of a floating circular aperture on a dc glow discharge dusty plasma

    NASA Astrophysics Data System (ADS)

    Heinrich, Jonathon R.; Kim, Su-Hyun; Merlino, Robert L.

    2009-11-01

    We have investigated novel effects observed when a floating aperture, either 6 mm or 8 mm in diameter, is placed 1-2 cm in front of an anode disk (4 cm diameter) that is used to form a dc glow discharge dusty plasma. Dust is incorporated into the anode glow plasma from a tray located below the anode which contained kaolin powder. The glow discharge traps particles with an average size of 1 micron. When the aperture is placed in front of the disk, well-defined pear-shaped or spherical dust clouds are formed, depending on the diameter of the aperture and its distance from the anode. The dust interacts with the aperture through the potential structure associated with the floating (negative) plate in which the aperture is located. The dust cloud is imaged using a CCD camera and a thin sheet of 532 nm laser light. Some of the effects observed include: outwardly expanding spherical dust acoustic waves and shocks, dust rotation around a void formed at the aperture, and a dust/discharge instability in which the discharge is periodically quenched and reignited while the dust cloud expands and contracts, with the dust retaining a residual charge.

  11. Growth of ultrananocrystalline diamond film by DC Arcjet plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Chen, G. C.; Li, B.; Yan, Z. Q.; Liu, J.; Lu, F. X.; Ye, H.

    2012-06-01

    Self-standing diamond films were grown by DC Arcjet plasma enhanced chemical vapor deposition (CVD). The feed gasses were Ar/H2/CH4, in which the flow ratio of CH4 to H2 (F/F) was varied from 5% to 20%. Two distinct morphologies were observed by scanning electron microscope (SEM), i.e. the "pineapple-like" morphology and the "cauliflower-like" morphology. It was found that the morphologies of the as-grown films are strongly dependent on the flow ratio of CH4 to H2 in the feed gasses. High resolution transmission electron microscope (HRTEM) survey results revealed that there were nanocrystalline grains within the "pineapple-like" films whilst there were ultrananocrystalline grains within "cauliflower-like" films. X-ray diffraction (XRD) results suggested that (110) crystalline plane was the dominant surface in the "cauliflower-like" films whilst (100) crystalline plane was the dominant surface in the "pineapple-like" films. Raman spectroscopy revealed that nanostructured carbon features could be observed in both types of films. Plasma diagnosis was carried out in order to understand the morphology dependent growth mechanism. It could be concluded that the film morphology was strongly influenced by the density of gas phases. The gradient of C2 radical was found to be different along the growth direction under the different growth conditions.

  12. Combined complementary plasma diagnostics to characterize a 2f plasma with additional DC current with conditioning effects at the chamber wall

    NASA Astrophysics Data System (ADS)

    Klick, Michael; Rothe, Ralf; Baek, Kye Hyun; Lee, Eunwoo

    2016-09-01

    Multiple frequencies and DC current used in a low-pressure plasma rf discharge result in an increased complexity. This needs plasma diagnostics applied, in particular in a plasma process chamber. That is done under manufacturing conditions which restrict the applicable plasma diagnostics to non-invasive methods with small footprint. So plasma chamber parameters, optical emission spectroscopy (OES), and self-excited electron spectroscopy (SEERS) are used to characterize the plasma and to understand chamber wall conditioning effects in an Ar plasma. The parameters are classified according to their origin--the region they are representative for. The center ion density is estimated from the DC current and compared to the SEERS electron density reflecting the electron density close to that at the chamber wall. The conditioning effects are caused by Si sputtering at a Si wafer changing the chamber wall state only when the chamber is clean, subsequent plasmas in the same chamber are not affected in that way. Through the combination of the complementary methods it can be shown that the chamber wall condition finally changes the radial plasma density distribution. Also the heating of electrons in the sheath is shown to be influenced by conditioning effects.

  13. Effect of oxygen plasma on the properties of tantalum oxide films

    SciTech Connect

    Kalygina, V. M. Zarubin, A. N.; Novikov, V. A.; Petrova, Yu. S.; Skakunov, M. S.; Tolbanov, O. P.; Tyazhev, A. V.; Yaskevich, T. M.

    2010-09-15

    The effect of oxygen plasma on the leakage current, permittivity, and the dielectric loss tangent of Ta{sub 2}O{sub 5} thin layers (300-400 nm) is studied. It is suggested to treat tantalum oxide films in oxygen plasma to control their electrical and dielectric characteristics.

  14. Modeling and experimental validation of a 1.2 MW DC transferred well-type plasma torch

    NASA Astrophysics Data System (ADS)

    Chau, S. W.; Hsu, K. L.; Lin, D. L.; Chen, J. S.; Tzeng, C. C.

    2007-07-01

    This paper discusses the numerical modeling and experimental validation of a 1.2 MW DC transferred plasma torch, which is equipped with a well-type cathode (WTC). In order to investigate the complicated thermal and flow characteristics due to the interaction between the working gas and electric arc, the flow filed inside the plasma torch is modeled by the magnetic-hydrodynamic (MHD) equations. The governing equations are solved numerically using a finite volume discretization for both cold and hot flow simulations. The numerical simulations are then validated by experimental measurements at a specific operation condition. The predicted results successfully reflect some important features of the studied transferred WTC plasma torch.

  15. Atomic Oxygen Durability Evaluation of Protected Polymers Using Thermal Energy Plasma Systems

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; Rutledge, Sharon K.; Degroh, Kim K.; Stidham, Curtis R.; Gebauer, Linda; Lamoreaux, Cynthia M.

    1995-01-01

    The durability evaluation of protected polymers intended for use in low Earth orbit (LEO) has necessitated the use of large-area, high-fluence, atomic oxygen exposure systems. Two thermal energy atomic oxygen exposure systems which are frequently used for such evaluations are radio frequency (RF) plasma ashers and electron cyclotron resonance plasma sources. Plasma source testing practices such as ample preparation, effective fluence prediction, atomic oxygen flux determination, erosion measurement, operational considerations, and erosion yield measurements are presented. Issues which influence the prediction of in-space durability based on ground laboratory thermal energy plasma system testing are also addressed.

  16. Variation of antioxidative activity and growth enhancement of Brassicaceae induced by low-pressure oxygen plasma

    NASA Astrophysics Data System (ADS)

    Ono, Reoto; Hayashi, Nobuya

    2015-06-01

    The mechanism of growth enhancement induced by active oxygen species generated in an oxygen plasma is investigated. The plant growth enhancement induced by the active oxygen species would relate to an antioxidative activity, which is one of the biological responses. The amount of generated active oxygen species is varied by the oxygen gas pressure in a low-pressure RF glow discharge plasma. The antioxidative activity of sprouts of Brassicaceae induced by the oxygen plasma is maximized at pressures between 30 and 40 Pa, whereas the antioxidative activity becomes small at around 60 and 80 Pa. The pressure dependence of the antioxidative activity of sprout stems is opposite to that of the stem length of the sprouts. The growth enhancement would be induced by the increase in the concentration of active oxygen species in plants owing to the decrease in the amount of antioxidative substances.

  17. Electron ranaway and ion-ion plasma formation in afterglow low-pressure plasma of oxygen-containing gas mixtures

    NASA Astrophysics Data System (ADS)

    Kudryavtsev, Anatoly; Bogdanov, Eugene; Kosykh, Nikolay; Gutsev, Sergey

    2012-10-01

    Experimental investigation of temporal evolution of charged plasma species in afterglow plasma of oxygen-containing mixtures have been investigated. The probe VAC and the time dependence of the saturation positive and negative particles currents to a probe in a fixed bias voltage were performed. The decay of afterglow low-pressure electronegative gas plasmas take place in two distinct stages (the electron-ion stage, and the ion-ion stage) as it was shown in [1] for pure oxygen. In the first stage, the negative ions are locked within a discharge volume and plasma is depleted of electrons and positive ions. The electron density decay is faster, than exponential, and practically all electrons leave plasma volume during finite time followed by the ion--ion (electron-free) plasma formation. The decay of the ion-ion plasma depends on the presence of detachment. With a large content of electronegative gas (oxygen) in a mixture, when there is a ``detachment particles,'' a small fraction of the electrons appearing as a result of the detachment continue to hold all negative ions in the discharge volume. In this case, the densities of all charged plasma components decay according to the same exponential law with a characteristic detachment time. At a low oxygen content in the gas mixture there is no detachment and plasma decays by an ion--ion ambipolar diffusion mechanism.[4pt][1]. S.A.Gutsev, A.A.Kudryavtsev, V.A.Romanenko. Tech.Phys. 40, 1131, (1995).

  18. Linear and Nonlinear Dust Acoustic Waves, Shocks and Stationary Structures in a dc-Glow-Discharge Dusty Plasma

    NASA Astrophysics Data System (ADS)

    Merlino, Robert

    2011-10-01

    In 1990, Rao, Shukla, and Yu (Planet. Space Sci. 38, 543) predicted the existence of the dust acoustic (DA) wave, a low-frequency (~ few Hz), compressional dust density wave that propagates through a dusty plasma at a phase speed ~ several cm/s. The DA wave was first observed by Chu et. al., (J. Phys. D: Appl. Phys. 27, 296, 1994) in an rf-produced dusty plasma, and by Barkan et. al., (Barkan et. al. Phys. Plasmas 2, 2161, 1995) who obtained video images of the DA wave trains using light scattering from a dust suspension confined in an anodic glow discharge plasma formed within a Q machine plasma. The dispersion relation for DAWs was measured by Thompson et. al., (Phys. Plasmas 4, 2331, 1997) in a dc glow discharge dusty plasma by modulating the discharge current at a set frequency. DAWs have been investigated by many groups both in weakly-coupled and strongly-coupled dusty plasmas (E. Thomas, Jr., Contrib. Plasma Phys. 49, 316, 2009). In most experiments where DA waves are present, the wave amplitude is relatively high, indicating that they are nonlinear. In this talk, results of our recent experiments on DAWs will be presented. The following experiments, performed in a dc glow-discharge dusty plasma will be described: (1) Observations of spontaneously excited nonlinear, cylindrical DAWs, which exhibit confluence of waves propagating at different speeds. (2) Investigations of self-steepening DAWs that develop into DA shocks with thicknesses comparable to the interparticle separation (Heinrich et. al., Phys. Rev. Lett. 103, 115001, 2009). (3) Measurements of the linear growth rates of DAWs excited in merging dust clouds. (4) The formation of stationary, stable dust density structures appearing as non-propagating DAWs (Heinrich et. al., Phys. Rev. E, in press, 2011). This work was performed in collaboration with S. H. Kim, J. R. Heinrich, and J. K. Meyer. Work supported by DOE Grant No. DE-FG01-04ER54795

  19. Surface energy increase of oxygen-plasma-treated PET

    SciTech Connect

    Cioffi, M.O.H.; Voorwald, H.J.C.; Mota, R.P

    2003-03-15

    Prosthetic composite is a widely used biomaterial that satisfies the criteria for application as an organic implant without adverse reactions. Polyethylene therephthalate (PET) fiber-reinforced composites have been used because of the excellent cell adhesion, biodegradability and biocompatibility. The chemical inertness and low surface energy of PET in general are associated with inadequate bonds for polymer reinforcements. It is recognized that the high strength of composites, which results from the interaction between the constituents, is directly related to the interfacial condition or to the interphase. A radio frequency plasma reactor using oxygen was used to treat PET fibers for 5, 20, 30 and 100 s. The treatment conditions were 13.56 MHz, 50 W, 40 Pa and 3.33x10{sup -7} m{sup 3}/s. A Rame-Hart goniometer was used to measure the contact angle and surface energy variation of fibers treated for different times. The experimental results showed contact angle values from 47 deg. to 13 deg. and surface energies from 6.4x10{sup -6} to 8.3x10{sup -6} J for the range of 5 to 100 s, respectively. These results were confirmed by the average ultimate tensile strength of the PET fiber/ polymethylmethacrylate (PMMA) matrix composite tested in tensile mode and by scanning electron microscopy.

  20. Self-sustained criterion with photoionization for positive dc corona plasmas between coaxial cylinders

    SciTech Connect

    Zheng, Yuesheng; Zhang, Bo He, Jinliang

    2015-06-15

    The positive dc corona plasmas between coaxial cylinders in air under the application of a self-sustained criterion with photoionization are investigated in this paper. A photon absorption function suitable for cylindrical electrode, which can characterize the total photons within the ionization region, is proposed on the basis of the classic corona onset criteria. Based on the general fluid model with the self-sustained criterion, the role of photoionization in the ionization region is clarified. It is found that the surface electric field keeps constant under a relatively low corona current, while it is slightly weakened with the increase of the corona current. Similar tendencies can be found under different conductor radii and relative air densities. The small change of the surface electric field will become more significant for the electron density distribution as well as the ionization activity under a high corona current, compared with the results under the assumption of a constant surface field. The assumption that the surface electric field remains constant should be corrected with the increase of the corona current when the energetic electrons with a distance from the conductor surface are concerned.

  1. Use of dc Ar microdischarge with nonlocal plasma for identification of metal samples

    SciTech Connect

    Kudryavtsev, A. A.; Stefanova, M. S.; Pramatarov, P. M.

    2015-04-07

    The possibility of using the collisional electron spectroscopy (CES) method for the detection of atoms from metal samples is experimentally verified. The detection and identification of metal atoms from a Pt sample in the nonlocal plasma of short (without positive column) dc Ar microdischarge at intermediate pressures (5–30 Torr) is realized in this work. Cathode sputtering is used for atomization of the metal under analysis. The identification of the analyzed metal is made from the energy spectra of groups of fast nonlocal electrons—characteristic electrons released in the Penning ionization of the Pt atoms by Ar metastable atoms and molecules. The acquisition of the electron energy spectra is performed using an additional electrode—a sensor located at the boundary of the discharge volume. The Pt characteristic Penning electrons form the maxima in the electron energy spectra at the energies of their appearance, which are 2.6 eV and 1.4 eV. From the measured energy of the maxima, identification of the metal atoms is accomplished. The characteristic Ar maxima due to pair collisions between Ar metastable atoms and molecules and super-elastic collisions are also recorded. This study demonstrates the possibility of creating a novel microplasma analyzer for atoms from metal samples.

  2. Investigation of multifractal nature of floating potential fluctuations obtained from a dc glow discharge magnetized plasma

    NASA Astrophysics Data System (ADS)

    Shaw, Pankaj Kumar; Saha, Debajyoti; Ghosh, Sabuj; Janaki, M. S.; Iyengar, A. N. Sekar

    2017-03-01

    In this paper, multifractal detrended fluctuation analysis (MF-DFA) has been used to analyze the floating potential fluctuations obtained with a Langmuir probe from a dc glow discharge magnetized plasma device. The generalized Hurst exponents (h(q)) , local fluctuation function (Fq(s)) , the Rényi exponents (τ(q)) and the multifractal spectrum F(α) have been calculated by applying the MF-DFA method. The result of the MF-DFA shows the multifractal nature of these fluctuations. We have investigated the influence of magnetic field on the multifractal nature of the fluctuations and it is seen that degree of multifractality is reduced with the increase in the magnetic field strength. The values of h(q) have been restricted between 0.7 and 1 for the magnetized fluctuations. This result is evidence of the existence of long-range correlations in the fluctuations. Furthermore, we employed shuffle and surrogate approaches to analyze the origins of multifractality. Comparing the MF-DFA results for the data set to those for shuffled and surrogate series, we have found that its multifractal nature is due to the existence of significant long-term correlation.

  3. Decorative black TiCxOy film fabricated by DC magnetron sputtering without importing oxygen reactive gas

    NASA Astrophysics Data System (ADS)

    Ono, Katsushi; Wakabayashi, Masao; Tsukakoshi, Yukio; Abe, Yoshiyuki

    2016-02-01

    Decorative black TiCxOy films were fabricated by dc (direct current) magnetron sputtering without importing the oxygen reactive gas into the sputtering chamber. Using a ceramic target of titanium oxycarbide (TiC1.59O0.31), the oxygen content in the films could be easily controlled by adjustment of total sputtering gas pressure without remarkable change of the carbon content. The films deposited at 2.0 and 4.0 Pa, those are higher pressure when compared with that in conventional magnetron sputtering, showed an attractive black color. In particular, the film at 4.0 Pa had the composition of TiC1.03O1.10, exhibited the L* of 41.5, a* of 0.2 and b* of 0.6 in CIELAB color space. These values were smaller than those in the TiC0.29O1.38 films (L* of 45.8, a* of 1.2 and b* of 1.2) fabricated by conventional reactive sputtering method from the same target under the conditions of gas pressure of 0.3 Pa and optimized oxygen reactive gas concentration of 2.5 vol.% in sputtering gas. Analysis of XRD and XPS revealed that the black film deposited at 4.0 Pa was the amorphous film composed of TiC, TiO and C. The adhesion property and the heat resisting property were enough for decorative uses. This sputtering process has an industrial advantage that the decorative black coating with color uniformity in large area can be easily obtained by plain operation because of unnecessary of the oxygen reactive gas importing which is difficult to be controlled uniformly in the sputtering chamber.

  4. Treatment Characteristics of Second Order Structure of Proteins Using Low-Pressure Oxygen RF Plasma

    NASA Astrophysics Data System (ADS)

    Hayashi, Nobuya; Nakahigashi, Akari; Kawaguchi, Ryutaro; Goto, Masaaki

    2010-10-01

    Removal of proteins from the surface of medical equipments is attempted using oxygen plasma produced by RF discharge. FTIR spectra indicate that the bonding of C-H and N-H in the casein protein is reduced after irradiation of oxygen plasma. Also, the second order structure of a protein such as α-helix and β-sheet are modified by the oxygen plasma. Complete removal of casein protein with the concentration of 0.016 mg/cm2 that is equivalent to remnants on the medical equipment requires two hours avoiding the damage to medical equipments.

  5. Development of a DC Glow Discharge Exhibit for the Demonstration of Plasma Behavior in a Magnetic Field

    NASA Astrophysics Data System (ADS)

    Bruder, Daniel

    2010-11-01

    The DC Glow Discharge Exhibit is intended to demonstrate the effects a magnetic field produces on a plasma in a vacuum chamber. The display, which will be featured as a part of The Liberty Science Center's ``Energy Quest Exhibition,'' consists of a DC glow discharge tube and information panels to educate the general public on plasma and its relation to fusion energy. Wall posters and an information booklet will offer brief descriptions of fusion-based science and technology, and will portray plasma's role in the development of fusion as a viable source of energy. The display features a horse-shoe magnet on a movable track, allowing viewers to witness the effects of a magnetic field upon a plasma. The plasma is created from air within a vacuum averaging between 100-200 mTorr. Signage within the casing describes the hardware components. The display is pending delivery to The Liberty Science Center, and will replace a similar, older exhibit presently at the museum.

  6. DC-driven plasma gun: self-oscillatory operation mode of atmospheric-pressure helium plasma jet comprised of repetitive streamer breakdowns

    NASA Astrophysics Data System (ADS)

    Wang, Xingxing; Shashurin, Alexey

    2017-02-01

    This paper presents and studies helium atmospheric pressure plasma jet comprised of a series of repetitive streamer breakdowns, which is driven by pure DC high voltage (self-oscillatory behavior). The repetition frequency of the breakdowns is governed by the geometry of discharge electrodes/surroundings and gas flow rate. Each next streamer is initiated when the electric field on the anode tip recovers after the previous breakdown and reaches the breakdown threshold value of about 2.5 kV cm-1. One type of the helium plasma gun designed using this operational principle is demonstrated. The gun operates on about 3 kV DC high voltage and is comprised of the series of the repetitive streamer breakdowns at a frequency of about 13 kHz.

  7. An experimental study on discharge characteristics in a pulsed-dc atmospheric pressure CH3OH/Ar plasma jet

    NASA Astrophysics Data System (ADS)

    Qian, Muyang; Liu, Sanqiu; Yang, Congying; Pei, Xuekai; Lu, Xinpei; Zhang, Jialiang; Wang, Dezhen

    2016-10-01

    Recently, C/H/Ar plasma discharges found enormous potential and possibility in carbonaceous compounds conversion and production. In this work, a pulsed-dc CH3OH/Ar plasma jet generated at atmospheric pressure is investigated by means of optical and electrical diagnosis concerning the variation of its basic parameters, absolute concentration of OH radicals, and plasma temperature with different CH3OH/Ar volume ratios, in the core region of discharge with needle-to-ring electrode configuration. The voltage-current characteristics are also measured at different CH3OH/Ar ratios. Laser-induced fluorescence (LIF) results here show that only small amounts of added methanol vapor to argon plasma (about 0.05% CH3OH/Ar volume ratio) is favorable for the production of OH radicals. The optical emission lines of CH, CN, and C2 radicals have been detected in the CH3OH/Ar plasma. And, the plasma temperatures increase with successive amount of added methanol vapor to the growth plasma. Moreover, qualitative discussions are presented regarding the mechanisms for methanol dissociation and effect of the CH3OH component on the Ar plasma discharge at atmospheric pressure.

  8. The role of thermal energy accommodation and atomic recombination probabilities in low pressure oxygen plasmas

    NASA Astrophysics Data System (ADS)

    Gibson, Andrew Robert; Foucher, Mickaël; Marinov, Daniil; Chabert, Pascal; Gans, Timo; Kushner, Mark J.; Booth, Jean-Paul

    2017-02-01

    Surface interaction probabilities are critical parameters that determine the behaviour of low pressure plasmas and so are crucial input parameters for plasma simulations that play a key role in determining their accuracy. However, these parameters are difficult to estimate without in situ measurements. In this work, the role of two prominent surface interaction probabilities, the atomic oxygen recombination coefficient γ O and the thermal energy accommodation coefficient α E in determining the plasma properties of low pressure inductively coupled oxygen plasmas are investigated using two-dimensional fluid-kinetic simulations. These plasmas are the type used for semiconductor processing. It was found that α E plays a crucial role in determining the neutral gas temperature and neutral gas density. Through this dependency, the value of α E also determines a range of other plasma properties such as the atomic oxygen density, the plasma potential, the electron temperature, and ion bombardment energy and neutral-to-ion flux ratio at the wafer holder. The main role of γ O is in determining the atomic oxygen density and flux to the wafer holder along with the neutral-to-ion flux ratio. It was found that the plasma properties are most sensitive to each coefficient when the value of the coefficient is small causing the losses of atomic oxygen and thermal energy to be surface interaction limited rather than transport limited.

  9. Deposition and characterization of molybdenum thin films using dc-plasma magnetron sputtering

    SciTech Connect

    Khan, Majid; Islam, Mohammad

    2013-12-15

    Molebdenum (Mo) thin films were deposited on well-cleaned soda-lime glass substrates using DC-plasma magnetron sputtering. In the design of experiment deposition was optimized for maximum beneficial characteristics by monitoring effect of process variables such as deposition power (100–200 W). Their electrical, structural and morphological properties were analyzed to study the effect of these variables. The electrical resistivity of Mo thin films could be reduced by increasing deposition power. Within the range of analyzed deposition power, Mo thin films showed a mono crystalline nature and the crystallites were found to have an orientation along [110] direction. The surface morphology of thin films showed that a highly dense micro structure has been obtained. The surface roughness of films increased with deposition power. The adhesion of Mo thin films could be improved by increasing the deposition power. Atomic force microscopy was used for the topographical study of the films and to determine the roughness of the films. X-ray diffractrometer and scanning electron microscopy analysis were used to investigate the crystallinity and surface morphology of the films. Hall effect measurement system was used to find resistivity, carrier mobility and carrier density of deposited films. The adhesion test was performed using scotch hatch tape adhesion test. Mo thin films prepared at deposition power of 200 W, substrate temperature of 23°C and Ar pressure of 0.0123 mbar exhibited a mono crystalline structure with an orientation along (110) direction, thickness of ∼550 nm and electrical resistivity value of 0.57 × 10{sup −4} Ω cm.

  10. Effect of Argon/Oxygen Flow Rate Ratios on DC Magnetron Sputtered Nano Crystalline Zirconium Titanate Thin Films

    NASA Astrophysics Data System (ADS)

    Rani, D. Jhansi; Kumar, A. GuruSampath; Sarmash, T. Sofi; Chandra Babu Naidu, K.; Maddaiah, M.; Rao, T. Subba

    2016-06-01

    High transmitting, non absorbent, nano crystalline zirconium titanate (ZT) thin films suitable for anti reflection coatings (ARC) were deposited on to glass substrates by direct current (DC) magnetron reactive sputtering technique, under distinct Argon to Oxygen (Ar/O2) gas flow rate ratios of 31/1, 30/2, 29/3 and 28/4, with a net gas flow (Ar + O2) of 32sccm, at an optimum substrate temperature of 250°C. The influence of the gas mixture ratio on the film properties has been investigated by employing x-ray diffraction (XRD), ultra violet visible (UV-vis) spectroscopy, atomic force microscopy (AFM), energy dispersive x-ray analysis (EDX) and four point probe methods. The films showed a predominant peak at 30.85° with (111) orientation. The crystallite size reduced from 22.94 nm to 13.5 nm and the surface roughness increased from 11.53 nm to 50.58 nm with increase in oxygen content respectively. The films deposited at 31/1 and 30/2 showed almost similar chemical composition. Increased oxygen content results an increase in electrical resistivity from 3.59 × 103 to 2.1 × 106 Ωm. The film deposited at Ar/O2 of 28/4 exhibited higher average optical transmittance of 91%, but its refractive index is higher than that of what is required for ARC. The films deposited at 31/1 and 30/2 of Ar/O2 possess higher transmittance (low absorbance) apart from suitable refractive index. Thus, these films are preferable candidates for ARC.

  11. Design and Development of High Voltage Direct Current (DC) Sources for the Solar Array Module Plasma Interaction Experiment

    NASA Technical Reports Server (NTRS)

    Bibyk, Irene K.; Wald, Lawrence W.

    1995-01-01

    Two programmable, high voltage DC power supplies were developed as part of the flight electronics for the Solar Array Module Plasma Interaction Experiment (SAMPIE). SAMPIE's primary objectives were to study and characterize the high voltage arcing and parasitic current losses of various solar cells and metal samples within the space plasma of low earth orbit (LEO). High voltage arcing can cause large discontinuous changes in spacecraft potential which lead to damage of the power system materials and significant Electromagnetic Interference (EMI). Parasitic currents cause a change in floating potential which lead to reduced power efficiency. These primary SAMPIE objectives were accomplished by applying artificial biases across test samples over a voltage range from -600 VDC to +300 VDC. This paper chronicles the design, final development, and test of the two programmable high voltage sources for SAMPIE. The technical challenges to the design for these power supplies included vacuum, space plasma effects, thermal protection, Shuttle vibrations and accelerations.

  12. Oxygen post-treatment of plastic surface coated with plasma polymerized silicon-containing monomers

    NASA Technical Reports Server (NTRS)

    Wydeven, T. J.; Hollanhan, J. R., Jr. (Inventor)

    1979-01-01

    The abrasion resistance of plastic surfaces coated with polymerized organosilanes can be significantly improved by post-treatment of the polymerized silane in an oxygen plasma. For optical purposes, the advantages of this post-treatment are developed with a transparent polycarbonate resin substrate coated with plasma polymerized vinyltrimethoxysilane.

  13. Relationship between the discharge mode and the spatial oxygen plasma distribution in a large size ferrite inductively coupled plasmas

    SciTech Connect

    Kim, Hyun Jun; Hwang, Hye Ju; Cho, Jeong Hee; Chae, Hee Sun; Kim, Dong Hwan; Chung, Chin-Wook

    2015-04-15

    The electrical characteristics and the spatial distribution of oxygen plasma according to the number of turns in ferrite inductively coupled plasmas (ferrite ICPs) are investigated. Through a new ICP model, which includes the capacitive coupling and the power loss of the ferrite material with the conventional ICP model, the variation of the oxygen discharge characteristics depending on the number of turns is simply understood by the electrical measurement, such as the antenna voltages and the currents. As the number of the turns increases, the capacitive coupling dominantly affects the spatial plasma distribution. This capacitive coupling results in a center focused density profile along the radial direction. In spite of the same discharge conditions (discharge chamber, neutral gas, and pressure), the spatial plasma distribution over 450 mm has drastic changes by increasing number of the turns. In addition, the effect of the negative species to the density profile is compared with the argon discharge characteristics at the same discharge configuration.

  14. Effect of DC glow discharge plasma treatment on PET/TiO(2) thin film surfaces for enhancement of bioactivity.

    PubMed

    Navaneetha Pandiyaraj, K; Selvarajan, V; Rhee, Young Ha; Kim, Hyoung Woo; Pavese, Matteo

    2010-08-01

    In this paper, the surfaces of PET/TiO(2) thin film were modified by DC glow discharge plasma as a function of discharge potentials for improving the bioactivity. The hydrophilicity of the plasma-treated PET/TiO(2) film was measured by contact angle measurement and the surface energy was estimated by using Fowkes method. The structural and chemical composition of the plasma-treated PET/TiO(2) was analysed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Immersion in a simulated body solution (SBF) solution was used to evaluate the bioactivity of the plasma-treated PET/TiO(2) samples in vitro. It was found that the plasma treatment modified the surfaces both in chemical composition and crystallinity which makes surface of the PET/TiO(2) to become more hydrophilic compared with untreated one. Analytical and microstructural investigations of SBF results, showed considerable higher rates of apatite formation on the plasma-treated PET/TiO(2) compared to the untreated films.

  15. Oxygen plasma ashing effects on aluminum and titanium space protective coatings

    NASA Technical Reports Server (NTRS)

    Synowicki, R.; Kubik, R. D.; Hale, J. S.; Peterkin, Jane; Nafis, S.; Woollam, John A.; Zaat, S.

    1991-01-01

    Using variable angle spectroscopic ellipsometry and atomic force microscopy (AFM), the surface roughness and oxidation of aluminum and titanium thin films have been studied as a function of substrate deposition temperature and oxygen plasma exposure. Increasing substrate deposition temperatures affect film microstructure by greatly increasing grain size. Short exposures to an oxygen plasma environment produce sharp spikes rising rapidly above the surface as seen by AFM. Ellipsometric measurements were made over a wide range of plasma exposure times, and results at longer exposure times suggest that the surface is greater than 30% void. This is qualitatively verified by the AFM images.

  16. Plasma corticosteroid dynamics in channel catfish, Ictalurus punctatus (Rafinesque), during and after oxygen depletion

    USGS Publications Warehouse

    Tomasso J.R., Davis; Parker, N.C.

    1981-01-01

    Plasma corticosteroid concentrations in channel catfish, Ictalurus punctatus, (normally 1.0 ± 0.3 μg/100 ml) increased significantly (to 5.9 ± 1.2μg/100 ml) in response to acute oxygen depletion and then returned to control levels within 30 min after the dissolved oxygen concentration was increased; however, a secondary increase in plasma corticosteroid levels was observed 6 h after exposure. Corticosteroid levels also increased in fish exposed to dissolved oxygen concentration of <0.2 mg/1 for three days. Methylene blue was not effective in preventing interrenal response to low dissolved oxygen. No diurnal plasma corticosteroid rhythm was observed in fish exposed to diurnal chemical rhythms of culture ponds.

  17. Theoretical studies on kinetics of singlet oxygen in nonthermal plasma

    NASA Astrophysics Data System (ADS)

    Frolov, Mikhail P.; Ionin, Andrei A.; Kotkov, Andrei A.; Kochetov, Igor V.; Napartovich, Anatolii P.; Podmarkov, Yurii P.; Seleznev, Leonid V.; Sinitsyn, Dmitrii V.; Vagin, Nikolai P.; Yuryshev, Nikolay N.

    2004-09-01

    An idea to replace singlet delta oxygen (SDO) generator working with wet chemistry by electric discharge generator has got much attention last years. Different kinds of discharge were examined for this purpose, but without a great success. The existing theoretical models are not validated by well-characterized experimental data. To describe complicated kinetics in gas discharge with oxygen one needs to know in detail processes involving numerous electronic excited oxygen molecules and atoms. To gain new knowledge about these processes experimental studies were made on electric discharge properties in gas mixture flow with independent control of inlet SDO concentration. The theoretical model extended to include minor additives like oxygen atoms, water molecules, ozone was developed. Comparison with careful experimental measurements of electric characteristics along with gas composition allows us to verify the model and make theoretical predictions more reliable. Results of numerical simulations using this model for an electron-beam sustained discharge are reported and compared with the experimental data.

  18. Analysis of processes in DC arc plasma torches for spraying that use air as plasma forming gas

    NASA Astrophysics Data System (ADS)

    Frolov, V.; Ivanov, D.; Toropchin, A.

    2014-11-01

    Developed in Saint Petersburg State Polytechnical University technological processes of air-plasma spraying of wear-resistant, regenerating, hardening and decorative coatings used in number of industrial areas are described. The article contains examples of applications of air plasma spraying of coatings as well as results of mathematical modelling of processes in air plasma torches for spraying.

  19. Enhancing surface functionality of reduced graphene oxide biosensors by oxygen plasma treatment for Alzheimer's disease diagnosis.

    PubMed

    Chae, Myung-Sic; Kim, Jinsik; Jeong, Dahye; Kim, YoungSoo; Roh, Jee Hoon; Lee, Sung Min; Heo, Youhee; Kang, Ji Yoon; Lee, Jeong Hoon; Yoon, Dae Sung; Kim, Tae Geun; Chang, Suk Tai; Hwang, Kyo Seon

    2017-06-15

    We performed oxygen plasma treatment on reduced graphene oxide (rGO) to improve its surface reactivity with respect to biomolecular interactions. Oxygen-plasma-treated rGO surfaces were employed as reactive interfaces for the detection of amyloid-beta (Aβ) peptides, the pathological hallmarks of Alzheimer's disease (AD), as the target analytes. By measuring the changes in electrical characteristics and confirmation through topographic analysis, the oxygen-plasma-treated rGO sensors had enhanced surface functionality for better antibody immobilization and sensing performance, with a 3.33-fold steeper slope for the electrical responses versus analyte concentration curve (logarithmic scale) compared to the untreated. The elicited biomolecular reactivity of the rGO surfaces with the oxygen plasma treatment remained at 46-51% of the initial value even after aging for 6h in ambient conditions. This phenomenon was also confirmed by pretreating the rGO surfaces with a blocking agent and subsequently subjecting them to antibody immobilization. Finally, the feasibility of the oxygen-plasma-treated rGO sensors as a diagnostic tool was evaluated with clinical samples of neural-derived exosomal Aβ peptides extracted from apparent AD patients and normal controls (NC). In contrast to the untreated sensors (p=0.0460), the oxygen-plasma-treated rGO sensors showed a significant p-value in the identification of clinical samples of AD and NC subjects (p<0.001). These results suggest that oxygen plasma treatment improves sensor performance without complicated fabrication procedures and should aid in the development of novel diagnostic tools based on carbon nanomaterials.

  20. AlN thin films deposited by DC reactive magnetron sputtering: effect of oxygen on film growth

    NASA Astrophysics Data System (ADS)

    García Molleja, Javier; José Gómez, Bernardo; Ferrón, Julio; Gautron, Eric; Bürgi, Juan; Abdallah, Bassam; Abdou Djouadi, Mohamed; Feugeas, Jorge; Jouan, Pierre-Yves

    2013-11-01

    Aluminum nitride is a ceramic compound with many technological applications in many fields, for example optics, electronics and resonators. Contaminants play a crucial role in the AlN performance. This paper focuses mainly in the effect of oxygen when AlN, with O impurities in its structure, is grown on oxidized layers. In this study, AlN thin films have been deposited at room temperature and low residual vacuum on SiO2/Si (1 0 0) substrates. AlN films were grown by DC reactive magnetron sputtering (aluminum target) and atmosphere composed by an argon/nitrogen mixture. Working pressure was 3 mTorr. Film characterization was performed by AES, XRD, SEM, EDS, FTIR, HRTEM, SAED and band-bending method. Our results show that oxidized interlayer imposes compressive stresses to AlN layer, developing a polycrystalline deposition. Indeed, when film thickness is over 900 nm, influence of oxidized interlayer diminishes and crystallographic orientation changes to the (0 0 0 2) one, i.e., columnar structure, and stress relief is induced (there is a transition from compressive to tensile stress). Also, we propose a growth scenario to explain this behaviour.

  1. Nutrients, oxygen dynamics, stable isotopes and fatty acid concentrations of a freshwater tidal system, Washington, D.C.

    PubMed

    MacAvoy, Stephen E; Ewers, Evan C; Bushaw-Newton, Karen L

    2009-09-01

    The Anacostia River in Washington, D.C., USA is an urban waterway contaminated with PAHs, PCBs, metals and sewage. Although several studies have examined the heavy metal geochemistry within the river, no studies have examined basic biogeochemical processes within the Anacostia river system. This study examines nutrients, bacterial biomarkers, organic material, and carbon, nitrogen and sulfur sources in the system. High biological oxygen demand and low nitrogen (0.33-0.56 mg L(-1)) and phosphorus (0.014-0.021 mg L(-1)) concentrations were observed in three areas of the river. Downstream sites had higher nutrient concentrations and dissolved organic matter (up to 13.7 mg L(-1)). Odd-chain length and branched fatty acids (FAs) in the sediments indicated bacterial sources, but long chain FAs indicative of terrestrial primary production were also abundant in some sediments. Sediment carbon stable isotope analyses showed a mix of autochthonous and allochthonous derived materials, but most carbon was derived from terrestrial sources (-23.3 to -31.7 per thousand). Sediment nitrogen stable isotopes ranged from -5.4 to 5.6 per thousand, showing nitrate uptake by plants and also recycling of nitrogen within the river. Sulfur sources were generally between 3 and -5 per thousand, reflecting local sulfate sources and anaerobic sulfate reduction.

  2. Effect of Low Pressure Nitrogen DC Plasma on Optical Properties of Biaxial-Oriented Polypropylene (BOPP), Poly Methyl Methacrylate (PMMA) and Poly Vinyl Chloride (PVC) Films

    NASA Astrophysics Data System (ADS)

    Mortazavi, S. H.; Ghoranneviss, M.; Faryadras, S.

    2012-06-01

    In this paper properties of Biaxial-Oriented Polypropylene, Poly Vinyl Chloride and Poly Methyl Methacrylate samples treated by DC glow discharge of N2 plasma have been investigated by UV-Vis_NIR spectrophotometer. It was found that plasma treatment change chemical structure of polymer surfaces. In addition, absorption coefficient, refractive index and extinction coefficient of all treated samples have been slightly changed.

  3. Enhancement of the crystalline Ge film growth by inductively coupled plasma-assisted pulsed DC sputtering.

    PubMed

    Kim, Eunkyeom; Han, Seung-Hee

    2014-11-01

    The effect of pulsed DC sputtering on the crystalline growth of Ge thin film was investigated. Ge thin films were deposited on the glass substrates using ICP-assisted pulsed DC sputtering. The Ge target was sputtered using asymmetric bipolar pulsed DC sputtering system with and without assistance of ICP source. The pulse frequency of 200 Hz and the pulse on time of 500 μsec (duty cycle = 10%) were kept during sputtering process. Crystal structures were studied from X-ray diffraction. The X-ray diffraction patterns clearly showed crystalline film structures. The Ge thin films with randomly oriented crystalline were obtained using pulsed DC sputtering without ICP, whereas they had well aligned (220) orientation crystalline using ICP source. Moreover, the combination of ICP assistance and pulsed DC sputtering enhanced the growth of crystalline Ge thin films without hydrogen and metal by in situ deposition. The structure and lattice of the films were studied from TEM images. The cross-sectional TEM images revealed the deposited Ge films with columnar structure.

  4. Treatment of enterococcus faecalis bacteria by a helium atmospheric cold plasma brush with oxygen addition

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Huang, Jun; Du, Ning; Liu, Xiao-Di; Wang, Xing-Quan; Lv, Guo-Hua; Zhang, Guo-Ping; Guo, Li-Hong; Yang, Si-Ze

    2012-07-01

    An atmospheric cold plasma brush suitable for large area and low-temperature plasma-based sterilization is designed. Results demonstrate that the He/O2 plasma more effectively kills Enterococcus faecalis than the pure He plasma. In addition, the sterilization efficiency values of the He/O2 plasma depend on the oxygen fraction in Helium gas. The atmospheric cold plasma brush using a proper ratio of He/O2 (2.5%) reaches the optimum sterilization efficiency. After plasma treatment, the cell structure and morphology changes can be observed by the scanning electron microscopy. Optical emission measurements indicate that reactive species such as O and OH play a significant role in the sterilization process.

  5. Treatment of enterococcus faecalis bacteria by a helium atmospheric cold plasma brush with oxygen addition

    SciTech Connect

    Chen Wei; Huang Jun; Wang Xingquan; Lv Guohua; Zhang Guoping; Du Ning; Liu Xiaodi; Guo Lihong; Yang Size

    2012-07-01

    An atmospheric cold plasma brush suitable for large area and low-temperature plasma-based sterilization is designed. Results demonstrate that the He/O{sub 2} plasma more effectively kills Enterococcus faecalis than the pure He plasma. In addition, the sterilization efficiency values of the He/O{sub 2} plasma depend on the oxygen fraction in Helium gas. The atmospheric cold plasma brush using a proper ratio of He/O{sub 2} (2.5%) reaches the optimum sterilization efficiency. After plasma treatment, the cell structure and morphology changes can be observed by the scanning electron microscopy. Optical emission measurements indicate that reactive species such as O and OH play a significant role in the sterilization process.

  6. Influence of oxygen in atmospheric-pressure argon plasma jet on sterilization of Bacillus atrophaeous spores

    NASA Astrophysics Data System (ADS)

    Lim, Jin-Pyo; Uhm, Han S.; Li, Shou-Zhe

    2007-09-01

    A nonequilibrium Ar /O2 plasma discharge at atmospheric pressure was carried out in a coaxial cylindrical reactor with a stepped electrode configuration powered by a 13.56MHz rf power supplier. The argon glow discharge with high electron density produces oxygen reactive species in large quantities. Argon plasma jets penetrate deep into ambient air and create a path for oxygen radicals to sterilize microbes. A sterilization experiment with bacterial endospores indicates that an argon-oxygen plasma jet very effectively kills endospores of Bacillus atrophaeus (ATCC 9372), thereby demonstrating its capability to clean surfaces and its usefulness for reinstating contaminated equipment as free from toxic biological warfare agents. The decimal reduction time (D values) of the Ar /O2 plasma jet at an exposure distance of 0.5-1.5cm ranges from 5 to 57s. An actinometric comparison of the sterilization data shows that atomic oxygen radicals play a significant role in plasma sterilization. When observed under a scanning electron microscope, the average size of the spores appears to be greatly reduced due to chemical reactions with the oxygen radicals.

  7. Influence of oxygen in atmospheric-pressure argon plasma jet on sterilization of Bacillus atrophaeous spores

    SciTech Connect

    Lim, Jin-Pyo; Uhm, Han S.; Li, Shou-Zhe

    2007-09-15

    A nonequilibrium Ar/O{sub 2} plasma discharge at atmospheric pressure was carried out in a coaxial cylindrical reactor with a stepped electrode configuration powered by a 13.56 MHz rf power supplier. The argon glow discharge with high electron density produces oxygen reactive species in large quantities. Argon plasma jets penetrate deep into ambient air and create a path for oxygen radicals to sterilize microbes. A sterilization experiment with bacterial endospores indicates that an argon-oxygen plasma jet very effectively kills endospores of Bacillus atrophaeus (ATCC 9372), thereby demonstrating its capability to clean surfaces and its usefulness for reinstating contaminated equipment as free from toxic biological warfare agents. The decimal reduction time (D values) of the Ar/O{sub 2} plasma jet at an exposure distance of 0.5-1.5 cm ranges from 5 to 57 s. An actinometric comparison of the sterilization data shows that atomic oxygen radicals play a significant role in plasma sterilization. When observed under a scanning electron microscope, the average size of the spores appears to be greatly reduced due to chemical reactions with the oxygen radicals.

  8. Oxygen transport in the internal xenon plasma of a dispenser hollow cathode

    SciTech Connect

    Capece, Angela M. Shepherd, Joseph E.; Polk, James E.; Mikellides, Ioannis G.

    2014-04-21

    Reactive gases such as oxygen and water vapor modify the surface morphology of BaO dispenser cathodes and degrade the electron emission properties. For vacuum cathodes operating at fixed temperature, the emission current drops rapidly when oxygen adsorbs on top of the low work function surface. Previous experiments have shown that plasma cathodes are more resistant to oxygen poisoning and can operate with O{sub 2} partial pressures one to two orders of magnitude higher than vacuum cathodes before the onset of poisoning occurs. Plasma cathodes used for electric thrusters are typically operated with xenon; however, gas phase barium, oxygen, and tungsten species may be found in small concentrations. The densities of these minor species are small compared with the plasma density, and thus, their presence in the discharge does not significantly alter the xenon plasma parameters. It is important, however, to consider the transport of these minor species as they may deposit on the emitter surface and affect the electron emission properties. In this work, we present the results of a material transport model used to predict oxygen fluxes to the cathode surface by solving the species conservation equations in a cathode with a 2.25 mm diameter orifice operated at a discharge current of 15 A, a Xe flow rate of 3.7 sccm, and 100 ppm of O{sub 2}. The dominant ionization process for O{sub 2} is resonant charge exchange with xenon ions. Ba is effectively recycled in the plasma; however, BaO and O{sub 2} are not. The model shows that the oxygen flux to the surface is not diffusion-limited; therefore, the high resistance to oxygen poisoning observed in plasma cathodes likely results from surface processes not considered here.

  9. Measuring atomic oxygen densities and electron properties in an Inductively Coupled Plasma for thin film deposition

    NASA Astrophysics Data System (ADS)

    Meehan, David; Gibson, Andrew; Booth, Jean-Paul; Wagenaars, Erik

    2016-09-01

    Plasma Enhanced Pulsed Laser Deposition (PE-PLD) is an advanced way of depositing thin films of oxide materials by using a laser to ablate a target, and passing the resulting plasma plume through a background Inductively-Coupled Plasma (ICP), instead of a background gas as is done in traditional PLD. The main advantage of PE-PLD is the control of film stoichiometry via the direct control of the reactive oxygen species in the ICP instead of relying on a neutral gas background. The aim is to deposit zinc oxide films from a zinc metal target and an oxygen ICP. In this work, we characterise the range of compositions of the reactive oxygen species achievable in ICPs; in particular the atomic oxygen density. The density of atomic oxygen has been determined within two ICPs of two different geometries over a range of plasma powers and pressures with the use of Energy Resolved Actinometry (ERA). ERA is a robust diagnostic technique with determines both the dissociation degree and average electron energy by comparing the excitation ratios of two oxygen and one argon transition. Alongside this the electron densities have been determined with the use of a hairpin probe. This work received financial support from the EPSRC, and York-Paris CIRC.

  10. Optical emission spectroscopy of 50 Hz pulsed dc nitrogen-hydrogen plasma in the presence of active screen cage

    NASA Astrophysics Data System (ADS)

    Saeed, A.; Abrar, M.; Khan, A. W.; Jan, F.; Khan, B. S.; Shah, H. U.; Zaka-ul-Islam, M.; Zakaullah, M.

    2016-05-01

    The N2-H2 plasma gas mixture, generated in a 50 Hz pulsed dc discharge system with active screen cage, is characterized by optical emission spectroscopy (OES), as a function of gas pressure, the fractions of hydrogen and current density. The N2 dissociation degree and N atomic density was measured with actinometery where argon gas is used as actinometer. It was shown that the increase in hydrogen fraction enhances the dissociation of N2, until the maximum of 40%. The excitation temperature is determined from Ar-I emission line intensities by using the simple Boltzmann plot method. The dissociation fraction and excitation temperature is found to increase with hydrogen mixing in nitrogen plasma.

  11. Hysteresis in amplitudes of self-excited oscillations for co-axial electrode-geometry DC glow discharge plasma

    SciTech Connect

    Kumar, R.; Narayanan, R.; Prasad, Awadhesh

    2014-12-15

    Hysteresis in amplitudes of the self-excited oscillations of the floating potential and discharge current is observed in an unmagnetized co-axial electrode-geometry DC glow discharge plasma system. The nonlinearities of these oscillations are studied using standard dynamical analysis tools. The characterization revealed the transition of low-amplitude high-frequency period-n oscillations to a large amplitude low frequency period-1 oscillations through a chaotic intermediate route. The transition of the low amplitude, high frequency period-n oscillations to chaotic type is observed to be linked to the dynamical change in the plasma system, i.e., after a negative differential resistance (NDR) region, whereas the transition from chaotic to period-1 is observed to be linked to a discharge current threshold.

  12. Determination of dissolved boron in fresh, estuarine, and geothermal waters by d.c. argon-plasma emission spectrometry

    USGS Publications Warehouse

    Ball, J.W.; Thompson, J.M.; Jenne, E.A.

    1978-01-01

    A d.c. argon-plasma emission spectrometer is used to determine dissolved boron in natural (fresh and estuarine) water samples. Concentrations ranged from 0.02 to 250 mg l-1. The emission-concentration function is linear from 0.02 to 1000 mg l-1. Achievement of a relative standard deviation of ??? 3% requires frequent restandardization to offset sensitivity changes. Dilution may be necessary to overcome high and variable electron density caused by differences in alkali-metal content and to avoid quenching of the plasma by high solute concentrations of sodium and other easily ionized elements. The proposed method was tested against a reference method and found to be more sensitive, equally or more precise and accurate, less subject to interferences, with a wider linear analytical range than the carmine method. Analyses of standard reference samples yielded results in all cases within one standard deviation of the means. ?? 1978.

  13. Hysteresis in amplitudes of self-excited oscillations for co-axial electrode-geometry DC glow discharge plasma

    NASA Astrophysics Data System (ADS)

    Kumar, R.; Narayanan, R.; Prasad, Awadhesh

    2014-12-01

    Hysteresis in amplitudes of the self-excited oscillations of the floating potential and discharge current is observed in an unmagnetized co-axial electrode-geometry DC glow discharge plasma system. The nonlinearities of these oscillations are studied using standard dynamical analysis tools. The characterization revealed the transition of low-amplitude high-frequency period-n oscillations to a large amplitude low frequency period-1 oscillations through a chaotic intermediate route. The transition of the low amplitude, high frequency period-n oscillations to chaotic type is observed to be linked to the dynamical change in the plasma system, i.e., after a negative differential resistance (NDR) region, whereas the transition from chaotic to period-1 is observed to be linked to a discharge current threshold.

  14. Catastrophic instabilities of modified DA-DC hybrid surface waves in a semi-bounded plasma system

    NASA Astrophysics Data System (ADS)

    Lee, Myoung-Jae; Jung, Young-Dae

    2016-06-01

    We find the catastrophic instabilities and derive the growth rates for the dust-cyclotron resonance (DCR) and dust-rotation resonance (DRR) modes of the modified dust-acoustic and dust-cyclotron (DA-DC) hybrid surface waves propagating at the plasma-vacuum interface where the plasma is semi-bounded and composed of electrons and rotating dust grains. The effects of magnetic field and dust rotation frequency on the DCR- and DDR-modes are also investigated. We find that the dust rotation frequency enhances the growth rate of DCR-mode and the effect of dust rotation on this resonance mode decreases with an increase of the wave number. We also find that an increase of magnetic field strength enhances the DCR growth rate, especially, for the short wavelength regime. In the case of DRR-mode, the growth rate is found to be decreased less sensitively with an increase of the wave number compared with the case of DCR, but much significantly enhanced by an increase of dust rotation frequency. The DRR growth rate also decreases with an increase of the magnetic field strength, especially in the long wavelength regime. Interestingly, we find that catastrophic instabilities occur for both DCR- and DRR-modes of the modified DA-DC hybrid surface waves when the rotational frequency is close to the dust-cyclotron frequency. Both modes can also be excited catastrophically due to the cooperative interaction between the DCR-mode and the DRR-mode.

  15. Structural evolution of Ti destroyable interlayer in large-size diamond film deposition by DC arc plasma jet

    NASA Astrophysics Data System (ADS)

    Guo, Jianchao; Li, Chengming; Liu, Jinlong; Wei, Junjun; Chen, Liangxian; Hua, Chenyi; Yan, Xiongbo

    2016-05-01

    The addition of titanium (Ti) interlayer was verified to reduce the residual stress of diamond films by self-fracturing and facilitate the harvest of a crack-free free-standing diamond film prepared by direct current (DC) arc plasma jet. In this study, the evolution of the Ti interlayer between large-area diamond film and substrate was studied and modeled in detail. The evolution of the interlayer was found to be relevant to the distribution of the DC arc plasma, which can be divided into three areas (arc center, arc main, and arc edge). The formation rate of titanium carbide (TiC) in the arc main was faster than in the other two areas and resulted in the preferred generation of crack in the diamond film in the arc main during cooling. Sandwich structures were formed along with the growth of TiC until the complete transformation of the Ti interlayer. The interlayer released stress via self-fracture. Avoiding uneven fragile regions that formed locally in the interlayer and achieving cooperatively released stress are crucial for the preparation of large crack-free diamond films.

  16. Dc to ac field conversion due to leaky-wave excitation in a plasma slab behind an ionization front

    NASA Astrophysics Data System (ADS)

    Kostin, V. A.; Vvedenskii, N. V.

    2015-03-01

    We present a way for generating coherent tunable electromagnetic radiation through dc to ac field conversion by an ionization front. The conversion is caused by the excitation of leaky waves behind the transversely limited ionization front propagating in a uniform electrostatic field. This differs significantly from the well-known dc-to-ac-radiation-converter models which consider Doppler-like frequency conversion by a transversely unlimited ionization front propagating in a spatially periodic electric field. We explore the dispersion properties and excitation of these leaky waves radiated through the transverse plasma boundary at the Cherenkov angle to the direction of propagation of a superluminal ionization front as dependent on the parameters of the plasma produced and on the speed of the ionization front. It is shown that not only the center frequency but also the duration and waveform of the generated pulse may significantly depend on the speed of the ionization front. The results indicate the possibility of using such converters based on planar photoconductive antennas to create sources of microwave and terahertz radiation with controllable waveforms that are transformed from video to radio pulse when the angle of incident ionizing radiation is tuned.

  17. Cold atmospheric pressure plasma jets as sources of singlet delta oxygen for biomedical applications

    SciTech Connect

    Sousa, J. S.; Niemi, K.; Cox, L. J.; Algwari, Q. Th.; Gans, T.; O'Connell, D.

    2011-06-15

    Absolute densities of singlet delta oxygen (SDO) molecules were measured using infrared optical emission spectroscopy in the flowing effluents of two different atmospheric-pressure plasma jets (APPJs): a capacitively coupled radio-frequency-driven jet (rf-APPJ) and a lower frequency kilohertz-driven dielectric barrier discharge jet. The plasma jets were operated in helium, with small admixtures of molecular oxygen (O{sub 2} < 2%). High absolute SDO densities of up to 6.2 x 10{sup 15} cm{sup -3} were measured at approximately 10 cm downstream. The rf-APPJ seems to be much more efficient in producing SDO. The influence of different parameters, such as gas flows and mixtures and power coupled to the plasmas, on the production of SDO by the two APPJs has been investigated. Despite the considerable differences between the two plasma jets (excitation frequency, electric field direction, inter-electrode distance, plasma propagation), similar dependencies on the oxygen admixture and on the dissipated power were found in both APPJs. However, opposite trends were observed for the gas flow dependence. The results presented in this paper show that the control of the external operating conditions of each APPJ enables the tailoring of the SDO composition of both plasma effluents. This provides scope to tune the plasma jets for desired applications, e.g., in biomedicine.

  18. Influence of oxygen traces on an atmospheric-pressure radio-frequency capacitive argon plasma discharge

    SciTech Connect

    Li Shouzhe; Wu Qi; Yan Wen; Wang Dezhen; Uhm, Han S.

    2011-10-15

    An atmospheric-pressure capacitive discharge source driven by radio-frequency power supply at 13.56 MHz has been developed experimentally that is capable of producing a homogeneous and cold glow discharge in O{sub 2}/Ar. With respect to the influence of oxygen component when diluted into argon plasma discharge on the discharge characteristics, the measurements of the electrical parameters (impedance, phase angle, resistance, and reactance) are made systematically and the densities of the metastable and resonant state of argon are determined by means of optical emission spectroscopy (OES). It is shown that the admixture of oxygen into argon plasma not only changes the electric characteristics but also alters the optical emission spectra greatly due to strong interaction between the oxygen content and the argon in the plasma environment.

  19. Differentiating the role of lithium and oxygen in retaining deuterium on lithiated plasma-facing components

    NASA Astrophysics Data System (ADS)

    Taylor, Chase

    2013-10-01

    Lithium wall conditioning has been implemented in nearly a dozen fusion devices, resulting in significantly improved plasma performance. Improvements are manifest as a reduction and eventual elimination of edge localized modes, reduced edge neutral density, reduced deuterium recycling, and some reduction in impurities. Initially, researchers assumed that lithium, via a direct lithium-deuterium bond, was directly responsible for these improvements. Our experiments and atomistic simulations have revealed that lithium coatings play a much more indirect role in improving plasma performance. The presence of oxygen in tokamaks is ubiquitously viewed as unfavorable. However, recent results show that lithium reduces oxygen impurities and surprisingly uses the oxygen to retain deuterium. Experiments using X-ray photoelectron spectroscopy identify that oxygen immediately begins to accumulate on lithium conditioned surfaces. Tight-binding density functional theory simulations tested various carbon matrices with and without lithium, oxygen, and hydrogen, and identified that oxygen plays the key role in retaining deuterium. In fact, a simulated PFC with 20% oxygen in carbon retains more deuterium than does 20% lithium in carbon. Recent experiments implanted oxygen in graphite to match simulations; however, we were unable to achieve the simulated results because all implanted oxygen was released upon deuterium bombardment. We therefore conclude that while oxygen retains deuterium, lithium plays an indispensible role in this process. Lithium attracts and retains oxygen, and then oxygen binds and retains deuterium. Work supported by USDOE Contracts DE-FG02-08ER54990 and DOE ID Field Office contract DE-AC07-05ID14517.

  20. The effect of oxygen-plasma treatment on the mechanical and piezoelectrical properties of ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Hussain, Mushtaque; Khan, Azam; Nur, Omer; Willander, Magnus; Broitman, Esteban

    2014-07-01

    We have studied the effect of oxygen plasma treatment on piezoelectric response and on the mechanical stability of ZnO nanorods synthesized on FTO by using ACG method. XRD and SEM techniques have shown highly dense and uniformly distributed nanorods. The piezoelectric properties and mechanical stability of as-grown and oxygen plasma treated samples were investigated by using nanoindentation technique. The comparison of load-displacement curves showed that the oxygen plasma treated samples are much stiffer and show higher generated piezo-voltage. This study demonstrates that the oxygen-plasma treatment is a good option to fabricate reliable and efficient nanodevices for enhanced generation of piezoelectricity.

  1. Efficiency of plasma density control with dc discharge and magnetic field for different surface types in low pressure hypersonic flow

    NASA Astrophysics Data System (ADS)

    Schweigert, Irina

    2013-09-01

    Recently the problem of communication blackout during reentrant flight still remains unsolved. The spacecrafts enter the upper atmospheric layers with a hypersonic speed and the shock heated air around them becomes weakly ionized. The gas ionization behind the shock front is associative in nature and occurs through chemical reactions between fragments of molecules. The formation of a plasma layer near the surfaces of spacecraft causes serious problems related to the blocking of communication channels with the Earth and other spacecrafts. A promising way of restoring the radio communications is the application of electrical and magnetic fields for controlling the plasma layer parameters. Nevertheless the flux of electrons and ions on the surface charges it that essentially decrease the effect of electro-magnetic control of local plasma density. In Ref. it is shown that there is the way to remove the surface charge using the lateral diode string structures. Based on two dimensional kinetic Particle in cell Monte Carlo collision simulations, we study the possibility of local control the plasma layer parameters near a flat surface of two different types. The gas velocity distribution is set with a model profile. We apply DC voltage up to 4 kV and magnetic field B up to 200 G.

  2. Controllable formation of graphene and graphene oxide sheets using photo-catalytic reduction and oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Ostovari, Fatemeh; Abdi, Yaser; Ghasemi, Foad

    2012-12-01

    Au/SiO2/Si interdigital electrodes with thickness of 1 μm were created on silicon substrate. Graphene oxide (GO) sheets hanging from these electrodes were obtained by spin coating of chemically synthesized GO dispersed in water. We used UV-light-induced photo-catalytic activity of titanium oxide nanoparticles to reduce the GO layer. Effects of the photo-induced chemical reduction on the conductivity of the GO were investigated. Also, low power DC plasma was used for oxidation of the sheets. Oxygen bombardment leads to sheets with low electrical conductivity. Measurements show that graphene and GO sheets with the controlled electrical conductivity were obtained by these processes. Scanning electron and atomic force microscopy were used to study the morphology of the TiO2/GO and graphene structures. X-ray diffraction and Raman scattering analysis were used to verify the structural characteristics of the prepared sheets. Analysis showed a gradual increase in the number of C-O bonds on the surface of the graphene layer as a result of increasing the time of plasma bombardment. Based on the Raman spectroscopy, the photo-catalytic activity of TiO2 nanoparticles resulted in a decrease in the number of C-O bonds.

  3. Dust particle circulation and vortices in a dc glow discharge dusty plasma

    NASA Astrophysics Data System (ADS)

    Kish, Ayden; Thomas, Edward

    2016-10-01

    Complex, or dusty, plasmas introduce a new charged species - dust grains of up to a few microns in diameter - to the dynamics of a background plasma discharge. While the size of these dust grains allow us to observe many plasma phenomena macroscopically, their presence also results in the generation of other processes that are unique to dusty plasmas. This presentation reports the observations of a recent study of toroidally-shaped dust clouds in a direct-current Argon plasma discharge. These dusty plasma clouds are formed by placing a conducting ring on a lower electrode while generating the plasma using an upper, biased electrode. Dust particles become suspended in the plasma between the two electrodes and, under the correct pressure and discharge conditions, the toroidally-shaped cloud is formed. This work reports on a variety of experimental configurations used to generate the clouds, measurements of particle flow and rotation using particle image velocimetry (PIV), and initial characterization of the plasma conditions that lead to the formation of these structures. Auburn University Undergraduate Research Fellowship and U.S. Department of Energy Grant Number DE-SC0010485.

  4. Cold plasma processing of local planetary ores for oxygen and metallurgically important metals

    NASA Technical Reports Server (NTRS)

    Lynch, D. C.; Bullard, D.; Ortega, R.

    1990-01-01

    The utilization of a cold plasma in chlorination processing is described. Essential equipment and instruments were received, the experimental apparatus assembled and tested, and preliminary experiments conducted. The results of the latter lend support to the original hypothesis: a cold plasma can both significantly enhance and bias chemical reactions. In two separate experiments, a cold plasma was used to reduce TiCl4 vapor and chlorinate ilmenite. The latter, reacted in an argon-chlorine plasma, yielded oxygen. The former experiment reveals that chlorine can be recovered as HCl vapor from metal chlorides in a hydrogen plasma. Furthermore, the success of the hydrogen experiments has lead to an analysis of the feasibility of direct hydrogen reduction of metal oxides in a cold plasma. That process would produce water vapor and numerous metal by-products.

  5. Method for determining the effects of oxygen plasma on a specimen

    NASA Technical Reports Server (NTRS)

    Whitaker, Ann F. (Inventor)

    1991-01-01

    A method for determining the effects of exposure of oxygen plasma on a specimen such as a thin film polymer or thin metals. The method includes providing an apparatus with a chamber having a holder supporting the polymer specimen in a plasma environment provided in the chamber. The chamber is regulated to a predetermined pressure and set temperature prior to the introduction of oxygen plasma therein. The specimen is then subjected to the plasma environment for a predetermined time during which time the temperature of the specimen is sensed and regulated to be maintained at the set temperature. Temperature sensing is accomplished by a probe which senses any changes in bulk sample temperature. Temperature regulation is provided by a thermoelectric module and by a coolant flow tube.

  6. Surface characterization and adhesion of oxygen plasma-modified LARC-TPI

    NASA Technical Reports Server (NTRS)

    Chin, J. W.; Wightman, J. P.

    1992-01-01

    LARC-TPI, an aromatic thermoplastic polyimide, was exposed to an oxygen plasma as a surface pretreatment for adhesive bonding. Chemical and physical changes which occurred in the polyimide surface as a result of the plasma treatment were investigated using X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IR-RAS), contact-angle analysis, ellipsometry, and high resolution SEM. A 180-deg peel test with an acrylate-based pressure sensitive adhesive as a flexible adherent was utilized to study the interactions of the plasma-treated polyimide surface with other polymeric materials. The surface characterization and adhesion testing results showed that the oxygen plasma treatment, while creating a more hydrophilic, polar surface, also caused chain scission, resulting in the formation of a weak boundary layer which inhibited adhesion.

  7. Optimizing the synthesis of vanadium-oxygen nanostructures by plasma plume dynamics using optical imaging

    NASA Astrophysics Data System (ADS)

    Masina, Bathusile N.; Lafane, Slimane; Wu, Lorinda; Abdelli-Messaci, Samira; Kerdja, Tahar; Forbes, Andrew

    2015-03-01

    The effect of an oxygen atmosphere on the expansion dynamics of a laser-produced vanadium-oxygen plasma has been investigated using a fast intensified charged-coupled device camera. We find regimes of the plasma plume expansion ranging from a free plume at vacuum and low oxygen pressures, through collisional and shock-wave-like hydrodynamic regimes at intermediate oxygen pressure, finally reaching a confined plume with subsequent thermalization of the plume particles at the highest pressure of the oxygen gas. Vanadium oxide nanostructures thin films were synthesized from this plasma and the resulting vanadium oxide phases studied as a function of the plume dynamics. We found monoclinic vanadium dioxide (VO2) (M1) and VO2 (B) nanoparticles in thin films deposited at 0.05 mbar. Pure phases of vanadium trioxide (V2O3) smooth and pentoxide (V2O5) nanorods thin films were detected at 0.01 and 0.1 to 0.2 mbar, respectively. Thin films containing VO2 (M1) were found to have a reversible metal-to-insulator transition at 61°C. This work paves the way to VO phase control by judicious choice of laser and plasma conditions.

  8. Analysis of EUV Oxygen Spectra from LLNL SSPX and UNR Laser Plasma Source of ``Sparky''

    NASA Astrophysics Data System (ADS)

    Wilcox, P. G.; Safronova, A. S.; Kantsyrev, V. L.; Safronova, U. I.; Williamson, K. M.; Weller, M. E.; Clementson, J.; Beiersdorfer, P.; Struve, K. W.

    2008-11-01

    In our recent work [Wilcox et al, RSI (2008, in press)] we applied a non- LTE kinetic model of oxygen to analyze an oxygen spectrum between 140 and 240 å, produced on LLNL SSPX. Here we study the whole collection of recent experimental SSPX EUV oxygen spectra produced under different plasma conditions, specifically in the broad range of temperatures from as low as 15 eV up to 280 eV, and at an electron density of around 10 ^14 cm-3. In addition, we analyze new experimental data from EUV oxygen and carbon spectra, recorded at much higher density at the compact laser plasma source of ``Sparky'' at UNR . The comprehensive comparison of EUV oxygen spectra from both experiments with theoretical calculations was accomplished, and temperature and density sensitive lines were identified.This work is relevant to diagnostics of plasma with low -- Z ions and Tokamak plasma in particular. Work is supported by DOE under grant DE-FG02-08ER54951 and in part under NNSA Coop. Agr. DE-FC52-06NA27588 and DE-FC52-06NA27586. Work at LLNL was performed under auspices of the DOE under contract DE-AC52-07NA2344.

  9. Modification of the Surface Properties of Polyimide Films using POSS Deposition and Oxygen Plasma Exposure

    NASA Technical Reports Server (NTRS)

    Wohl, Christopher J.; Belcher, Marcus A.; Ghose, Sayata; Connell, John W.

    2008-01-01

    Topographically rich surfaces were generated by spray-coating organic solutions of a polyhedral oligomeric silsesquioxane, octakis (dimethylsilyloxy) silsesquioxane (POSS), on Kapton HN films and exposing them to radio frequency generated oxygen plasma. Changes in both surface chemistry and topography were observed. High-resolution scanning electron microscopy indicated substantial modification of the POSS-coated polyimide surface topographies as a result of oxygen plasma exposure. Water contact angles varied from 104 deg for unexposed POSS-coated surfaces to approximately 5 deg, for samples exposed for 5 h. Modulation of the dispersive and polar contributions to the surface energy was determined using van Oss Good Chaudhury theory.

  10. Deposition of Lanthanum Strontium Cobalt Ferrite (LSCF) Using Suspension Plasma Spraying for Oxygen Transport Membrane Applications

    NASA Astrophysics Data System (ADS)

    Fan, E. S. C.; Kesler, O.

    2015-08-01

    Suspension plasma spray deposition was utilized to fabricate dense lanthanum strontium cobalt ferrite oxygen separation membranes (OSMs) on porous metal substrates for mechanical support. The as-sprayed membranes had negligible and/or reversible material decomposition. At the longer stand-off distance (80 mm), smooth and dense membranes could be manufactured using a plasma with power below approximately 81 kW. Moreover, a membrane of 55 μm was observed to have very low gas leakage rates desirable for OSM applications. This thickness could potentially be decreased further to improve oxygen diffusion by using metal substrates with finer surface pores.

  11. Sterilization of Bacillus subtilis Spores Using an Atmospheric Plasma Jet with Argon and Oxygen Mixture Gas

    NASA Astrophysics Data System (ADS)

    Shen, Jie; Cheng, Cheng; Fang, Shidong; Xie, Hongbing; Lan, Yan; Ni, Guohua; Meng, Yuedong; Luo, Jiarong; Wang, Xiangke

    2012-03-01

    To determine an efficient sterilization mechanism, Bacillus subtilis spore samples were exposed to an atmospheric plasma jet. By using argon/oxygen mixture gas, the decimal reduction value was reduced from 60 s (using argon gas) to 10 s. More dramatically, after 5 min treatment, the colony-forming unit (CFU) was reduced by six orders. To understand the underlying mechanism of the efficient sterilization by plasma, the contributions from heat, UV radiation, charged particles, ozone, and reactive oxygen radicals were distinguished in this work, showing that charged particles and ozone were the main killing factors. The shape changes of the spores were also discussed.

  12. Charge neutral MoS2 field effect transistors through oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Dhall, Rohan; Li, Zhen; Kosmowska, Ewa; Cronin, Stephen B.

    2016-11-01

    Lithographically fabricated MoS2 field effect transistors suffer from several critical imperfections, including low sub-threshold swings, large turn-on gate voltages (VT), and wide device-to-device variability. The large magnitude and variability of VT stems from unclean interfaces, trapped charges in the underlying substrate, and sulfur vacancies created during the mechanical exfoliation process. In this study, we demonstrate a simple and reliable oxygen plasma treatment, which mitigates the effects of unintentional doping created by surface defect sites, such as S vacancies, and surface contamination. This plasma treatment restores charge neutrality to the MoS2 and shifts the threshold turn-on voltage towards 0 V. Out of the 10 devices measured, all exhibit a shift of the FET turn-on voltage from an average of -18 V to -2 V. The oxygen plasma treatment passivates these defects, which reduces surface scattering, causing increased mobility and improved subthreshold swing. For as-prepared devices with low mobilities (˜0.01 cm2/V s), we observe up to a 190-fold increase in mobility after exposure to the oxygen plasma. Perhaps the most important aspect of this oxygen plasma treatment is that it reduces the device-to-device variability, which is a crucial factor in realizing any practical application of these devices.

  13. Method for minimizing decarburization and other high temperature oxygen reactions in a plasma sprayed material

    DOEpatents

    Lenling, William J.; Henfling, Joseph A.; Smith, Mark F.

    1993-06-08

    A method is disclosed for spray coating material which employs a plasma gun that has a cathode, an anode, an arc gas inlet, a first powder injection port, and a second powder injection port. A suitable arc gas is introduced through the arc gas inlet, and ionization of the arc gas between the cathode and the anode forms a plasma. The plasma is directed to emenate from an open-ended chamber defined by the boundary of the anode. A coating is deposited upon a base metal part by suspending a binder powder within a carrier gas that is fed into the plasma through the first powder injection port; a material subject to degradation by high temperature oxygen reactions is suspended within a carrier gas that is fed into the plasma through the second injection port. The material fed through the second injection port experiences a cooler portion of the plasma and has a shorter dwell time within the plasma to minimize high temperature oxygen reactions. The material of the first port and the material of the second port intermingle within the plasma to form a uniform coating having constituent percentages related to the powder-feed rates of the materials through the respective ports.

  14. Development of metal nanocluster ion source based on dc magnetron plasma sputtering at room temperature.

    PubMed

    Majumdar, Abhijit; Köpp, Daniel; Ganeva, Marina; Datta, Debasish; Bhattacharyya, Satyaranjan; Hippler, Rainer

    2009-09-01

    A simple and cost effective nanocluster ion source for the deposition of size selected metal nanocluster has been developed based on the dc magnetron discharge (including pulsed dc discharge). The most important and interesting feature of this cluster source is that it is working at room temperature, cooled by chilled water during the experiment. There is no extraction unit in this device and the cluster streams flow only due to the pressure gradient from source chamber to substrate via quadrupole mass filter. It has provision of multiple substrate holders in the deposition chamber, which can be controlled manually. The facility consists of quadrupole mass filter (QMF 200), which can select masses in the range of 2-125 000 atoms depending on the target materials, with a constant mass resolution (M/DeltaM approximately 25). The dc magnetron discharge at a power of about 130 W with Ar as feed/buffer gas was used to produce the Cu nanocluster in an aggregation tube and deposited on Si (100) wafer temperature.

  15. Numerical and experimental study on a pulsed-dc plasma jet

    NASA Astrophysics Data System (ADS)

    Liu, X. Y.; Pei, X. K.; Lu, X. P.; Liu, D. W.

    2014-06-01

    A numerical and experimental study of plasma jet propagation in a low-temperature, atmospheric-pressure, helium jet in ambient air is presented. A self-consistent, multi-species, two-dimensional axially symmetric plasma model with detailed finite-rate chemistry of helium-air mixture composition is used to provide insights into the propagation of the plasma jet. The obtained simulation results suggest that the sheath forms near the dielectric tube inner surface and shields the plasma channel from the tube surface. The strong electric field at the edge of the dielectric field enhances the ionization in the air mixing layer; therefore, the streamer head becomes ring-shaped when the streamer runs out of the tube. The avalanche-to-streamer transition is the main mechanism of streamer advancement. Penning ionization dominates the ionization reactions and increases the electrical conductivity of the plasma channel. The simulation results are supported by experimental observations under similar discharge conditions.

  16. Characterization of an oxygen plasma process for cleaning packaged semiconductor devices. Final report

    SciTech Connect

    Adams, B.E.

    1996-11-01

    The purpose of this research was to experimentally determine the operating {open_quotes}window{close_quotes} for an oxygen plasma cleaning process to be used on microelectronics components just prior to wire bonding. The process was being developed to replace one that used vapor degreasing with trichlorotrifluoroethane, an ozone-depleting substance. A Box-Behnken experimental design was used to generate data from which the oxygen plasma cleaning process could be characterized. Auger electron spectrophotometry was used to measure the contamination thickness on the dice after cleaning. An empirical equation correlating the contamination thickness on the die surface with the operating parameters of the plasma system was developed from the collected Auger data, and optimum settings for cleaning semiconductor devices were determined. Devices were also tested for undesirable changes in electrical parameters resulting from cleaning in the plasma system. An increase in leakage current occurred for bipolar transistors and diodes after exposure to the oxygen plasma. Although an increase in leakage current occurred, each device`s parameter remained well below the acceptable specification limit. Based upon the experimental results, the optimum settings for the plasma cleaning process were determined to be 200 watts of power applied for five minutes in an enclosure maintained at 0.7 torr. At these settings, all measurable contamination was removed without compromising the reliability of the devices.

  17. Is the mammalian cell plasma membrane a barrier to oxygen transport?

    PubMed Central

    1992-01-01

    Oxygen transport in the Chinese hamster ovary (CHO) plasma membrane has been studied by observing the collision of molecular oxygen with nitroxide radical spin labels placed in the lipid bilayer portion of the membrane at various distances from the membrane surface using the long-pulse saturation-recovery electron spin resonance (ESR) technique. The collision rate was estimated for 5-, 12-, and 16-doxylstearic acids from spin-lattice relaxation times (T1) measured in the presence and absence of molecular oxygen. Profiles of the local oxygen transport parameters across the membrane were obtained showing that the oxygen diffusion-concentration product is lower than in water for all locations at 37 degrees C. From oxygen transport parameter profiles, the membrane oxygen permeability coefficients were estimated according to the procedure developed earlier by Subczynski et al. (Subczynski, W. K., J. S. Hyde, and A. Kusumi. 1989. Proceedings of the National Academy of Sciences, USA. 86:4474-4478). At 37 degrees C, the oxygen permeability coefficient for the plasma membrane was found to be 42 cm/s, about two times lower than for a water layer of the same thickness as the membrane. The oxygen concentration difference across the CHO plasma membrane at physiological conditions is in the nanomolar range. It is concluded that oxygen permeation across the cell plasma membrane cannot be a rate-limiting step for cellular respiration. Correlations of the form PM = cKs between membrane permeabilities PM of small nonelectrolyte solutes of mol wt less than 50, including oxygen, and their partition coefficients K into hexadecane and olive oil are reported. Hexadecane: c = 26 cm/s, s = 0.95; olive oil: c = 23 cm/s, s = 1.56. These values of c and s differ from those reported in the literature for solutes of 50 less than mol wt less than 300 (Walter, A., and J. Gutknecht. 1986. Journal of Membrane Biology. 90:207-217). It is concluded that oxygen permeability through membranes can be

  18. Oxygen plasma damage to blanket and patterned ultralow-{kappa} surfaces

    SciTech Connect

    Bao, J.; Shi, H.; Huang, H.; Ho, P. S.; McSwiney, M. L.; Goodner, M. D.; Moinpour, M.; Kloster, G. M.

    2010-03-15

    Oxygen plasma damage to blanket and patterned ultralow-{kappa} (ULK) dielectric surfaces was investigated by examining the effect of plasma species and dielectric materials. Blanket ULK films and patterned structures were treated by O{sub 2} plasma in a remote plasma chamber where the ions and radicals from the plasma source can be separately controlled to study their respective roles in the damage process. The plasma damage was characterized by angle resolved x-ray photoelectron spectroscopy, x-ray reflectivity, and Fourier transform infrared spectroscopy. Studies of the angle dependence of oxygen plasma damage to blanket ULK films indicated that damage by ions was anisotropic while that by radicals was isotropic. Ions were found to play an important role in assisting carbon depletion by oxygen radicals on the blanket film surface. More plasma damage was observed with increasing porosity in ultralow-{kappa} films. Probable reaction paths were proposed by analyzing the reaction by-products. Plasma damage to the sidewall of low-{kappa} trenches was examined by electron energy loss (EELS) analysis. The depletion depth of carbon was found to be related to the penetration of radical species into the porous dielectric and the distribution at the sidewall and trench bottom was affected by the trench pattern geometry, i.e., the aspect ratio, which can be correlated with the electron potential distribution and subsequent trajectory of ions. Vapor silylation was applied for dielectric recovery of trench structure and the result was examined by EELS. The trimethylchlorosilane was found to be effective for recovery of the sidewall carbon loss. The recovery was better for loss induced by radical O{sub 2} than by hybrid O{sub 2} and the difference was attributed to the surface densification by ions limiting the mass transport of vapor chemicals.

  19. Oxygen plasma-treated thermoresponsive polymer surfaces for cell sheet engineering.

    PubMed

    Shimizu, Kazunori; Fujita, Hideaki; Nagamori, Eiji

    2010-06-01

    Although cell sheet tissue engineering is a potent and promising method for tissue engineering, an increase of mechanical strength of a cell sheet is needed for easy manipulation of it during transplantation or 3D tissue fabrication. Previously, we developed a cell sheet-polymer film complex that had enough mechanical strength that can be manipulated even by tweezers (Fujita et al., 2009. Biotechnol Bioeng 103(2): 370-377). We confirmed the polymer film involving a temperature sensitive polymer and extracellular matrix (ECM) proteins could be removed by lowering temperature after transplantation, and its potential use in regenerative medicine was demonstrated. However, the use of ECM proteins conflicted with high stability in long-term storage and low cost. In the present study, to overcome these drawbacks, we employed the oxygen plasma treatment instead of using the ECM proteins. A cast and dried film of thermoresponsive poly-N-isopropylacrylamide (PNIPAAm) was fabricated and treated with high-intensity oxygen plasma. The cells became possible to adhere to the oxygen plasma-treated PNIPAAm surface, whereas could not to the inherent surface of bulk PNIPAAm without treatment. Characterizations of the treated surface revealed the surface had high stability. The surface roughness, wettability, and composition were changed, depending on the plasma intensity. Interestingly, although bulk PNIPAAm layer had thermoresponsiveness and dissolved below lower critical solution temperature (LCST), it was found that the oxygen plasma-treated PNIPAAm surface lost its thermoresponsiveness and remained insoluble in water below LCST as a thin layer. Skeletal muscle C2C12 cells could be cultured on the oxygen plasma-treated PNIPAAm surface, a skeletal muscle cell sheet with the insoluble thin layer could be released in the medium, and thus the possibility of use of the cell sheet for transplantation was demonstrated.

  20. Streptococci biofilm decontamination on teeth by low-temperature air plasma of dc corona discharges

    NASA Astrophysics Data System (ADS)

    Kovalóvá, Z.; Zahoran, M.; Zahoranová, A.; Machala, Z.

    2014-06-01

    Non-thermal plasmas of atmospheric pressure air direct current corona discharges were investigated for potential applications in dental medicine. The objective of this ex vivo study was to apply cold plasmas for the decontamination of Streptococci biofilm grown on extracted human teeth, and to estimate their antimicrobial efficiency and the plasma's impact on the enamel and dentine of the treated tooth surfaces. The results show that both positive streamer and negative Trichel pulse coronas can reduce bacterial population in the biofilm by up to 3 logs in a 10 min exposure time. This bactericidal effect can be reached faster (within 5 min) by electrostatic spraying of water through the discharge onto the treated tooth surface. Examination of the tooth surface after plasma exposure by infrared spectroscopy and scanning electron microscopy did not show any significant alteration in the tooth material composition or the tooth surface structures.

  1. Characterization of DC magnetron plasma in Ar/Kr/N2 mixture during deposition of (Cr,Al)N coating

    NASA Astrophysics Data System (ADS)

    Bobzin, K.; Bagcivan, N.; Theiß, S.; Brugnara, R.; Bibinov, N.; Awakowicz, P.

    2017-02-01

    Reactive sputter deposition of (Cr,Al)N coatings in DC magnetron plasmas containing Ar/Kr/N2 mixtures is characterized by applying a combination of voltage–current measurement, optical emission spectroscopy (OES) and numerical simulation. Theoretical and experimental methods supplement each other and their combination permits us to obtain the most reliable information about the processes by physical vapor deposition. Gas temperature (T g) and plasma parameters, namely electron density n e and electron temperature T e are determined by spatial resolved measurements of molecular nitrogen photoemission. Steady-state densities of Cr and Al atoms are measured using OES. The sputtering of Cr and Al atoms is simulated using the TRIDYN code, measured electric current and applied voltage. Transport of sputtered atoms through the plasma volume is simulated by adopting a Monte-Carlo code. In order to quantify the ‘poisoning’ of the target surface with nitrogen, simulated steady state densities of Al and Cr atoms at different states of poisoning and at different distances from the target are compared with the measured densities. In addition, simulated fluxes of Cr and Al atoms to the substrate are compared with the measured deposition rates of the (Cr,Al)N coating.

  2. Effects of oxygen plasma treatment on the surface wettability and dissolution of furosemide compacts.

    PubMed

    Naseem, A; Olliff, C J; Martini, L G; Lloyd, A W

    2003-11-01

    The plasma irradiation of furosemide (frusemide) was investigated as a possible technique for increasing the dissolution rate of this drug. Oxygen plasma was used to generate oxygen-containing functional groups on the surface of the compact to increase the wettability of the surface and the dissolution rate of the drug. Compacts of furosemide (300 mg) were produced using a stainless steel die and punch assembly, which was placed into a KBr press. The time of the plasma treatment was varied to assess the effect if any upon the dissolution rate and the wettability of the drug. Dissolution experiments of the plasma-treated and untreated compacts were carried out using the paddle apparatus method. Dissolution was carried out at 37 degrees C using 1 L of 0.1 M HCl and phosphate buffer (pH 6). The wettability was assessed by contact angle measurements using the sessile drop technique. Untreated and plasma-treated samples were analysed by scanning electron microscopy at x 5000 magnification. Plasma treatment was found to lower the equilibrium contact angle from approximately 50 to 35 degrees but the dissolution rate was not significantly affected. This was attributed to fusion of the surface by the plasma treatment.

  3. Ratio of oxygen to sulfur in the Io plasma torus

    NASA Technical Reports Server (NTRS)

    Shemansky, Donald E.

    1987-01-01

    The relative concentrations of O and S ions in the hot dense region of the Io plasma torus (IPT) are investigated by means of model calculations based on collisional diffusive equilibrium. The spectroscopic constraints and uncertainties encountered in calculating the ion partitioning and the modeling procedures employed are discussed, and the results are presented in tables and graphs and compared with Voyager EUV data and the rocket observations of Skinner and Durrance (1986). It is found that the observed O and S emission from the IPT can be reproduced by models with approximately equal partitioning between O and S species. The assumptions and analyses leading to the conclusion (Moreno et al., 1985) that the IPT is S-dominated (by 3 to 1 or more) are analyzed in detail and rejected.

  4. Sterilization Performance and Material Compatibility of Sterilizer for Dental Instruments using RF Oxygen Plasma

    NASA Astrophysics Data System (ADS)

    Sakai, Yasuhiro; Liu, Zhen; Hayashi, Nobuya; Goto, Masaaki

    2015-09-01

    The sterilization performance and material compatibility of low-pressure RF plasma sterilization method for dental instruments were investigated. RF electrode used in this experiment has been optimized for sterilization of dental instruments. The vial-type biological indicator (BI) simulating tiny space of dental instrument was used for evaluation of the sterilization performance. The pressure in the stainless chamber was fixed at 60 Pa. Sterilization of BI was achieved in shortest time 40 min at 80 W, and the sterilization effect was confirmed using three BIs. Light emission spectra of oxygen plasma indicated that production of atomic oxygen and excited oxygen molecule are maximum at pressure of 20 Pa and 200 Pa, respectively. Sterilization results of BIs indicated that successful rate increases with the oxygen pressure towards 200 Pa. Therefore, the excited oxygen molecule is deduced to be a major factor of the sterilization of BI. Surface morphology of dental instruments such as diamond bar was evaluated using scanning electron microscope (SEM). The deterioration of fine crystals of diamond bar has not observed after the plasma irradiation for 120 min with RF input power was 60W and pressure was 200 Pa.

  5. Effect of ambient combinations of argon, oxygen, and hydrogen on the properties of DC magnetron sputtered indium tin oxide films

    NASA Astrophysics Data System (ADS)

    Marikkannan, M.; Subramanian, M.; Mayandi, J.; Tanemura, M.; Vishnukanthan, V.; Pearce, J. M.

    2015-01-01

    Sputtering has been well-developed industrially with singular ambient gases including neutral argon (Ar), oxygen (O2), hydrogen (H2) and nitrogen (N2) to enhance the electrical and optical performances of indium tin oxide (ITO) films. Recent preliminary investigation into the use of combined ambient gases such as an Ar+O2+H2 ambient mixture, which was suitable for producing high-quality (low sheet resistance and high optical transmittance) of ITO films. To build on this promising preliminary work and develop deeper insight into the effect of ambient atmospheres on ITO film growth, this study provides a more detailed investigation of the effects of ambient combinations of Ar, O2, H2 on sputtered ITO films. Thin films of ITO were deposited on glass substrates by DC magnetron sputtering using three different ambient combinations: Ar, Ar+O2 and Ar+O2+H2. The structural, electrical and optical properties of the three ambient sputtered ITO films were systematically characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman spectroscopy, four probe electrical conductivity and optical spectroscopy. The XRD and Raman studies confirmed the cubic indium oxide structure, which is polycrystalline at room temperature for all the samples. AFM shows the minimum surface roughness of 2.7 nm for Ar+O2+H2 sputtered thin film material. The thickness of the films was determined by the cross sectional SEM analysis and its thickness was varied from 920 to 817 nm. The columnar growth of ITO films was also discussed here. The electrical and optical measurements of Ar+O2+H2 ambient combinations shows a decreased sheet resistance (5.06 ohm/□) and increased optical transmittance (69%) than other samples. The refractive index and packing density of the films were projected using optical transmission spectrum. From the observed results the Ar+O2+H2 ambient is a good choice to enhance the total optoelectronic properties of the ITO films

  6. Effect of ambient combinations of argon, oxygen, and hydrogen on the properties of DC magnetron sputtered indium tin oxide films

    SciTech Connect

    Marikkannan, M.; Subramanian, M.; Tanemura, M.; Mayandi, J. E-mail: jeyanthinath@yahoo.co.in; Vishnukanthan, V.; Pearce, J. M. E-mail: jeyanthinath@yahoo.co.in

    2015-01-15

    Sputtering has been well-developed industrially with singular ambient gases including neutral argon (Ar), oxygen (O{sub 2}), hydrogen (H{sub 2}) and nitrogen (N{sub 2}) to enhance the electrical and optical performances of indium tin oxide (ITO) films. Recent preliminary investigation into the use of combined ambient gases such as an Ar+O{sub 2}+H{sub 2} ambient mixture, which was suitable for producing high-quality (low sheet resistance and high optical transmittance) of ITO films. To build on this promising preliminary work and develop deeper insight into the effect of ambient atmospheres on ITO film growth, this study provides a more detailed investigation of the effects of ambient combinations of Ar, O{sub 2}, H{sub 2} on sputtered ITO films. Thin films of ITO were deposited on glass substrates by DC magnetron sputtering using three different ambient combinations: Ar, Ar+O{sub 2} and Ar+O{sub 2}+H{sub 2}. The structural, electrical and optical properties of the three ambient sputtered ITO films were systematically characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman spectroscopy, four probe electrical conductivity and optical spectroscopy. The XRD and Raman studies confirmed the cubic indium oxide structure, which is polycrystalline at room temperature for all the samples. AFM shows the minimum surface roughness of 2.7 nm for Ar+O{sub 2}+H{sub 2} sputtered thin film material. The thickness of the films was determined by the cross sectional SEM analysis and its thickness was varied from 920 to 817 nm. The columnar growth of ITO films was also discussed here. The electrical and optical measurements of Ar+O{sub 2}+H{sub 2} ambient combinations shows a decreased sheet resistance (5.06 ohm/□) and increased optical transmittance (69%) than other samples. The refractive index and packing density of the films were projected using optical transmission spectrum. From the observed results the Ar+O{sub 2}+H

  7. Ground-Based Tests of Spacecraft Polymeric Materials under OXY-GEN Plasma-Beam

    NASA Astrophysics Data System (ADS)

    Chernik, Vladimir; Novikov, Lev; Gaidar, Anna

    2016-07-01

    Spacecraft LEO mission is accompanied by destruction of polymeric material surface under influence of atomic oxygen flow. Sources of molecular, plasma and ion beams are used for the accelerated ground-based tests of spacecraft materials. In the work application of oxygen plasma accelerator of a duoplasmatron type is described. Plasma particles have been accelerated up to average speed of 13-16 km/s. Influence of such beam on materials leads to more intensive destruction of polymers than in LEO. This fact allows to execute tests in the accelerated time scale by a method of an effective fluence. Special measures were given to decrease a concentration of both gaseous and electrode material impurities in the oxygen beam. In the work the results of simulative tests of spacecraft materials and experiments on LEO are considered. Comparison of plasma beam simulation with LEO data has shown conformity for structures of a number of polymeric materials. The relative erosion yields (normalized with respect to polyimide) of the tested materials are shown practically equal to those in LEO. The obtained results give grounds for using the plasma-generation mode with ion energies of 20-30 eV to accelerated testing of spacecraft materials for long -term LEO missions.

  8. Plasma jet-induced tissue oxygenation: potentialities for new therapeutic strategies

    NASA Astrophysics Data System (ADS)

    Collet, G.; Robert, E.; Lenoir, A.; Vandamme, M.; Darny, T.; Dozias, S.; Kieda, C.; Pouvesle, J. M.

    2014-02-01

    The lack of oxygen is a major reason for the resistance of tumor cells to treatments such as radiotherapies. A large number of recent publications on non-thermal plasma applications in medicine report cell behavior modifications and modulation of soluble factors. This in vivo study tested whether such modifications can lead to vascular changes in response to plasma application. Two in situ optical-based methods were used simultaneously, in real time, to assess the effect of non-thermal plasma on tissue vasculature. Tissue oxygen partial pressure (pO2) was measured using a time-resolved luminescence-based optical probe, and the microvascular erythrocyte flow was determined by laser Doppler flowmetry. When plasma treatment was applied on mouse skin, a rapid pO2 increase (up to 4 times) was subcutaneously measured and correlated with blood flow improvement. Such short duration, i.e. 5 min, plasma-induced effects were shown to be locally restricted to the treated area and lasted over 120 min. Further investigations should elucidate the molecular mechanisms of these processes. However, improvement of oxygenation and perfusion open new opportunities for tumor treatments in combination with radiotherapy, and for tumor blood vessel normalization based strategies.

  9. Flexible reduced graphene oxide supercapacitor fabricated using a nitrogen dc-pulse atmospheric-pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Yang, Cheng-Han; Kuok, Fei-Hong; Liao, Chen-Yu; Wan, Ting-Hao; Chen, Chieh-Wen; Hsu, Cheng-Che; Cheng, I.-Chun; Chen, Jian-Zhang

    2017-02-01

    We use a nitrogen dc-pulse atmospheric-pressure plasma jet to fabricate a flexible reduced graphene oxide (rGO) supercapacitor with polyvinyl alcohol (PVA)/sulfuric acid (H2SO4) gel electrolyte. An areal capacitance of 47.03 mF · cm‑2 (evaluated using cyclic voltammetry (CV) under a potential scan rate of 2 mV · s‑1) is achieved. The supercapacitor can be operated without apparent degradation under bending with a bending radius of 0.55 cm. After a 1000 cycle CV stability test, the capacitance retention rate is 100% when flat and is 98.6% under bending (bending radius  =  0.55 cm), indicating promising stability of the APPJ-processed flexible supercapacitor.

  10. Oxygen plasma immersion ion implantation treatment to enhance data retention of tungsten nanocrystal nonvolatile memory

    SciTech Connect

    Wang, Jer-Chyi Chang, Wei-Cheng; Lai, Chao-Sung; Chang, Li-Chun; Ai, Chi-Fong; Tsai, Wen-Fa

    2014-03-15

    Data retention characteristics of tungsten nanocrystal (W-NC) memory devices using an oxygen plasma immersion ion implantation (PIII) treatment are investigated. With an increase of oxygen PIII bias voltage and treatment time, the capacitance–voltage hysteresis memory window is increased but the data retention characteristics become degraded. High-resolution transmission electron microscopy images show that this poor data retention is a result of plasma damage on the tunneling oxide layer, which can be prevented by lowering the bias voltage to 7 kV. In addition, by using the elevated temperature retention measurement technique, the effective charge trapping level of the WO{sub 3} film surrounding the W-NCs can be extracted. This measurement reveals that a higher oxygen PIII bias voltage and treatment time induces more shallow traps within the WO{sub 3} film, degrading the retention behavior of the W-NC memory.

  11. A Comparison of Atomic Oxygen Degradation in Low Earth Orbit and in a Plasma Etcher

    NASA Technical Reports Server (NTRS)

    Townsend, Jacqueline A.; Park, Gloria

    1997-01-01

    In low Earth orbit (LEO) significant degradation of certain materials occurs from exposure to atomic oxygen (AO). Orbital opportunities to study this degradation for specific materials are limited and expensive. While plasma etchers are commonly used in ground-based studies because of their low cost and convenience, the environment produced in an etcher chamber differs greatly from the LEO environment. Because of the differences in environment, the validity of using etcher data has remained an open question. In this paper, degradation data for 22 materials from the orbital experiment Evaluation of Oxygen Interaction with Materials (EOIM-3) are compared with data from EOIM-3 control specimens exposed in a typical plasma etcher. This comparison indicates that, when carefully considered, plasma etcher results can produce order-of-magnitude estimates of orbital degradation. This allows the etcher to be used to screen unacceptable materials from further, more expensive tests.

  12. A Fiber Optic Catalytic Sensor for Neutral Atom Measurements in Oxygen Plasma

    PubMed Central

    Zaplotnik, Rok; Vesel, Alenka; Mozetic, Miran

    2012-01-01

    The presented sensor for neutral oxygen atom measurement in oxygen plasma is a catalytic probe which uses fiber optics and infrared detection system to measure the gray body radiation of the catalyst. The density of neutral atoms can be determined from the temperature curve of the probe, because the catalyst is heated predominantly by the dissipation of energy caused by the heterogeneous surface recombination of neutral atoms. The advantages of this sensor are that it is simple, reliable, easy to use, noninvasive, quantitative and can be used in plasma discharge regions. By using different catalyst materials the sensor can also be applied for detection of neutral atoms in other plasmas. Sensor design, operation, example measurements and new measurement procedure for systematic characterization are presented. PMID:22666005

  13. The use of ion chromatography-dc plasma atomic emission spectrometry for the speciation of trace metals

    SciTech Connect

    Urasa, I.T.

    1991-09-20

    The original objects of this research program were: to interface d.c. plasma atomic emission spectrometer with an ion chromatograph; to characterize and optimize the combined systems for application in the speciation of metals in aqueous solutions; to use this system in the study of the solution chemistry of various metals; and to find ways in which the measurement sensitivity of the method can be enhanced, thereby allowing the detection of metal species at low ppb concentration levels. This approach has been used to study the chemistry of and speciate several elements in solution including: arsenic, chromium, iron, manganese, nickel phosphorus, platinum, selenium, and vanadium. During the course of this research, we have found that the solution chemistry of the elements studied and the speciation data obtained can vary considerably depending on the solution, and the chromatographic conditions employed. The speciation of chromium, iron, and vanadium was found to be highly influenced by the acidity of the sample. The element selective nature of the d.c. plasma detector allows these changes to be monitored, thereby providing quantitative information on the new moieties formed. New approaches are being developed including the use of chelating ligands as preconcentration agents for purposes of reducing further the detection limits of the elements of interest and to improve the overall element speciation scheme. New thrusts are being directed towards the employment of post-column derivatization method coupled with colorimetric measurements to detect and quantify metal species eluting from the chromatographic column. The influence of sample acidity on these investigations will be carefully evaluated. These new thrusts are described in the accompanying Project Renewal Proposal.

  14. Initial Results of DC Electric Fields, Associated Plasma Drifts, Magnetic Fields, and Plasma Waves Observed on the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Bromund, K.; Klenzing, J.; Rowland, D.; Maynard, N.

    2010-01-01

    Initial results are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite, a mission designed to understand, model, and forecast the presence of equatorial ionospheric irregularities. The VEFI instrument includes a vector DC electric field detector, a fixed-bias Langmuir probe operating in the ion saturation regime, a flux gate magnetometer, an optical lightning detector, and associated electronics including a burst memory. Compared to data obtained during more active solar conditions, the ambient DC electric fields and their associated E x B drifts are variable and somewhat weak, typically < 1 mV/m. Although average drift directions show similarities to those previously reported, eastward/outward during day and westward/downward at night, this pattern varies significantly with longitude and is not always present. Daytime vertical drifts near the magnetic equator are largest after sunrise, with smaller average velocities after noon. Little or no pre-reversal enhancement in the vertical drift near sunset is observed, attributable to the solar minimum conditions creating a much reduced neutral dynamo at the satellite altitude. The nighttime ionosphere is characterized by larger amplitude, structured electric fields, even where the plasma density appears nearly quiescent. Data from successive orbits reveal that the vertical drifts and plasma density are both clearly organized with longitude. The spread-F density depletions and corresponding electric fields that have been detected thus far have displayed a preponderance to appear between midnight and dawn. Associated with the narrow plasma depletions that are detected are broad spectra of electric field and plasma density irregularities for which a full vector set of measurements is available for detailed study. Finally, the data set includes a wide range of ELF/VLF/HF oscillations corresponding to a variety of plasma waves

  15. Pressure and arc voltage coupling in dc plasma torches: Identification and extraction of oscillation modes

    SciTech Connect

    Rat, V.; Coudert, J. F.

    2010-08-15

    This work is devoted to the instabilities occurring in a plasma torch, such as those found in plasma spraying. These instabilities are responsible for a lack of reproducibility of coatings properties, especially in the case of suspension plasma spraying that is an innovative way to obtain thin coatings of submicron-sized particles. Strong Helmholtz oscillations are highlighted in the plasma flow and it is demonstrated that they overlap with different acoustic modes in addition with the more commonly admitted ''restrike'' mode, the later being due to rearcing events in the arc region. The instabilities occur in the arc voltage but it is experimentally shown in this paper that the pressure within the torch body presents the same kind of instabilities. Besides, a numerical filtering technique has been adapted to isolate the different instability components. The operating parameters of the plasma torch were varied in order to highlight their influence on the amplitude of the different modes, both for the arc voltage and the pressure.

  16. Oxygen radicals inhibit human plasma acetylhydrolase, the enzyme that catabolizes platelet-activating factor.

    PubMed Central

    Ambrosio, G; Oriente, A; Napoli, C; Palumbo, G; Chiariello, P; Marone, G; Condorelli, M; Chiariello, M; Triggiani, M

    1994-01-01

    Platelet-activating factor (PAF) can exert profound inflammatory effects at very low concentrations. In plasma, PAF is hydrolyzed to lyso-PAF by acetylhydrolase, an enzyme that circulates bound to LDL. Previous studies suggest that oxygen radicals may act synergistically with PAF to potentiate tissue injury. However, mechanisms underlying this interaction have not been elucidated. In this study we investigated whether oxygen radicals may inactivate PAF acetylhydrolase. PAF acetylhydrolase activity was measured in human plasma and purified LDL before and after exposure to radicals (10-20 nmol/min per ml) generated by xanthine/xanthine oxidase. Oxygen radicals induced > 50% loss of PAF acetylhydrolase activity within 60 s and almost complete inactivation by 10 min. This phenomenon was irreversible and independent of oxidative modification of LDL. Inactivation occurred without changes in the affinity constant of the enzyme (Km was 17.9 microM under control conditions and 15.1 microM after exposure to oxygen radicals). Inactivation was prevented by the scavengers superoxide dismutase or dimethylthiourea or by the iron chelator deferoxamine. Thus, superoxide-mediated, iron-catalyzed formation of hydroxyl radicals can rapidly and irreversibly inactivate PAF acetylhydrolase. Since concomitant production of PAF and oxygen radicals can occur in various forms of tissue injury, inactivation of acetylhydrolase might represent one mechanism by which oxygen radicals may potentiate and prolong the proinflammatory effects of PAF. Images PMID:8200975

  17. Experimental analysis on the nonlinear behavior of DC barrier discharge plasmas

    NASA Astrophysics Data System (ADS)

    Dogan, Mansuroglu; Ilker Umit, Uzun-Kaymak

    2017-01-01

    Nonlinear behavior of glow discharge plasmas is experimentally investigated. The glow is generated between a barrier semiconductor electrode, Chromium doped namely Gallium Arsenide (GaAs:Cr), as a cathode and an Indium-Tin Oxide (ITO) coated glass electrode as an anode, in reverse bias. The planar nature of electrodes provides symmetry in spatial geometry. The discharge behaves oscillatory in the time domain, with single and sometimes multi-periodicities in plasma current and voltage characteristics. In this paper, harmonic frequency generation and transition to chaotic behavior is investigated. The observed current-voltage characteristics of the discharge are discussed in detail.

  18. Surface activation of cyclo olefin polymer by oxygen plasma discharge: a molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Soberon, Felipe

    2014-07-01

    Thermoplastic substrates made of cyclo olefin polymer (COP) are treated with oxygen plasma discharges to introduce polar groups at the surface. This is the first step in the process of surface functionalization of COP substrates used in biosensor devices. A molecular dynamics model of basic COP structure is implemented using the second-generation reactive empirical bond order (REBO) potentials for hydrocarbon-oxygen interactions. The model includes covalent bond and Van der Waals interactions. The bombardment of a COP surface with mono-energetic atomic oxygen ions, energy in the range 1-35 eV, is simulated and reported here. The dynamics of the substrate modification reveals that the substrate top layer is de-hydrogenated and subsequently builds up an oxygen-carbon matrix layer, ˜10 Å thick. Analysis of the modified substrates indicates that surface yield is predominantly peroxide groups.

  19. Tailoring surface properties of polyethylene separator by low pressure 13.56 MHz RF oxygen plasma glow discharge

    NASA Astrophysics Data System (ADS)

    Li, Chun; Liang, Chia-Han; Huang, Chun

    2016-01-01

    Low-pressure plasma surface modification in a radio-frequency capacitively coupled glow discharge of oxygen gas was carried out to induce polar functional groups onto polyethylene membrane separator surfaces to enhance its hydrophilicity. The surface changes in surface free energy were monitored by static contact angle measurement. A significant increase in the surface energy of polyethylene membrane separators caused by the oxygen gas plasma modifications was observed. The static water contact angle of the plasma-modified membrane separator significantly decreased with the increase in treatment duration and plasma power. An obvious increase in the surface energy of the membrane separators owing to the oxidative effect of oxygen-gas-plasma modifications was also observed. Optical emission spectroscopy was carried out to analyze the chemical species generated by oxygen gas plasma surface modification. The variations in the surface morphology and chemical structure of the separators were confirmed by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). XPS showed significantly higher surface concentrations of oxygen functional groups in the oxygen-gas-plasma-modified polymeric separator surfaces than in the unmodified polymeric separator surface. The experimental results show the important role of chemical species in the interaction between oxygen gas plasmas and the separator surface, which can be controlled by surface modification to tailor the hydrophilicity of the separator.

  20. Targeting cancer cells with reactive oxygen and nitrogen species generated by atmospheric-pressure air plasma.

    PubMed

    Ahn, Hak Jun; Kim, Kang Il; Hoan, Nguyen Ngoc; Kim, Churl Ho; Moon, Eunpyo; Choi, Kyeong Sook; Yang, Sang Sik; Lee, Jong-Soo

    2014-01-01

    The plasma jet has been proposed as a novel therapeutic method for cancer. Anticancer activity of plasma has been reported to involve mitochondrial dysfunction. However, what constituents generated by plasma is linked to this anticancer process and its mechanism of action remain unclear. Here, we report that the therapeutic effects of air plasma result from generation of reactive oxygen/nitrogen species (ROS/RNS) including H2O2, Ox, OH-, •O2, NOx, leading to depolarization of mitochondrial membrane potential and mitochondrial ROS accumulation. Simultaneously, ROS/RNS activate c-Jun NH2-terminal kinase (JNK) and p38 kinase. As a consequence, treatment with air plasma jets induces apoptotic death in human cervical cancer HeLa cells. Pretreatment of the cells with antioxidants, JNK and p38 inhibitors, or JNK and p38 siRNA abrogates the depolarization of mitochondrial membrane potential and impairs the air plasma-induced apoptotic cell death, suggesting that the ROS/RNS generated by plasma trigger signaling pathways involving JNK and p38 and promote mitochondrial perturbation, leading to apoptosis. Therefore, administration of air plasma may be a feasible strategy to eliminate cancer cells.

  1. Atomic oxygen behavior at downstream of AC excited atmospheric pressure He plasma jet

    NASA Astrophysics Data System (ADS)

    Takeda, Keigo; Ishikawa, Kenji; Tanaka, Hiromasa; Sekine, Makoto; Hori, Masaru

    2016-09-01

    Applications of atmospheric pressure plasma jets (APPJ) have been investigated in the plasma medical fields such as cancer therapy, blood coagulation, etc. Reactive species generated by the plasma jet interacts with the biological surface. Therefore, the issue attracts much attentions to investigate the plasma effects on targets. In our group, a spot-size AC excited He APPJ have been used for the plasma medicine. From diagnostics of the APPJ using optical emission spectroscopy, the gas temperature and the electron density was estimated to be 299 K and 3.4 ×1015 cm-3. The AC excited He APPJ which affords high density plasma at room temperature is considered to be a powerful tool for the medical applications. In this study, by using vacuum ultraviolet absorption spectroscopy, the density of atomic oxygen on a floating copper as a target irradiated by the He APPJ was measured as a function of the distance between the plasma source and the copper wire. The measured density became a maximum value around 8 ×1013 cm-3 at 12 mm distance, and then decreased over the distance. It is considered that the behavior was due to the changes in the plasma density on the copper wire and influence of ambient air.

  2. Improvement of photocatalytic activity of silver nanoparticles by radio frequency oxygen plasma irradiation

    NASA Astrophysics Data System (ADS)

    Fang, Yingcui; Zhang, Bing; Hong, Liu; Yao, Damao; Xie, Zhiqiang; Jiang, Yang

    2015-07-01

    Photocatalytic activity (PA) of silver nanoparticles (AgNPs) induced by radio frequency (RF) oxygen plasma irradiation (OPI) is investigated in this paper. An improvement in PA by 365% and 181% has been achieved when 15 nm AgNPs irradiated by oxygen plasma for 2 s were used to degrade 10-5 M Rhodamine 6 G (R6G) under ultraviolet (UV) and visible lights, respectively. The PA caused by OPI is better than that induced by the localized surface plasma resonance (LSPR) of AgNPs. The mechanism for the improvement was explored by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and UV-vis absorption spectra. The OPI-induced formation of AgO/AgNP and Ag2O/AgNP-heterogeneous photocatalysts and electrophilic oxygen are considered to be responsible for the PA improvement. This investigation deepens our understanding of oxygen-assisted photocatalysis of AgNPs and provides a practical approach using solar light for broad spectra photocatalysis with high efficiency.

  3. dc field-emission analysis of GaAs and plasma-source ion-implanted stainless steel

    SciTech Connect

    C. Hernandez; T. Wang; T. Siggins; D. Bullard; H. F. Dylla; C. Reece; N. D. Theodore; D. M. Manos

    2003-06-01

    Field-emission studies have been performed on a GaAs wafer and a sample of its stainless-steel (SS) support electrode that are part of a photocathode gun for the 10 kW Upgrade infrared free electron laser at Jefferson Lab. The objective of the studies presented here is to characterize the effect of both the cleanliness of the wafer and the plasma-source ion-implanted layer on the electrode to suppress field emission. Field emission is the limiting factor to achieve the required 6 MV/m at the surface of the wafer. Potential field emitters are first located on the surface of 1 in. diameter samples with a dc scanning field-emission microscope at 60 MV/m, then each emitter is characterized in a scanning electron microscope equipped with an energy dispersive spectrometer. The GaAs wafer was hydrogen cleaned before the study. The results show three emitters caused by indium contamination during wafer handling. The GaAs wafer thus shows good high-voltage characteristics and the need to maintain cleanliness during handling. The SS sample is hand polished with diamond paste to a 1-m surface finish, then implanted with N2/SiO2 in a plasma-source ion-implantation chamber in preparation for the field-emission studies.

  4. Non-thermal dielectric barrier discharge plasma induces angiogenesis through reactive oxygen species

    PubMed Central

    Arjunan, Krishna Priya; Friedman, Gary; Fridman, Alexander; Clyne, Alisa Morss

    2012-01-01

    Vascularization plays a key role in processes such as wound healing and tissue engineering. Non-thermal plasma, which primarily produces reactive oxygen species (ROS), has recently emerged as an efficient tool in medical applications including blood coagulation, sterilization and malignant cell apoptosis. Liquids and porcine aortic endothelial cells were treated with a non-thermal dielectric barrier discharge plasma in vitro. Plasma treatment of phosphate-buffered saline (PBS) and serum-free medium increased ROS concentration in a dose-dependent manner, with a higher concentration observed in serum-free medium compared with PBS. Species concentration inside cells peaked 1 h after treatment, followed by a decrease 3 h post treatment. Endothelial cells treated with a plasma dose of 4.2 J cm–2 had 1.7 times more cells than untreated samples 5 days after plasma treatment. The 4.2 J cm–2 plasma dose increased two-dimensional migration distance by 40 per cent compared with untreated control, while the number of cells that migrated through a three-dimensional collagen gel increased by 15 per cent. Tube formation was also enhanced by plasma treatment, with tube lengths in plasma-treated samples measuring 2.6 times longer than control samples. A fibroblast growth factor-2 (FGF-2) neutralizing antibody and ROS scavengers abrogated these angiogenic effects. These data indicate that plasma enhanced proliferation, migration and tube formation is due to FGF-2 release induced by plasma-produced ROS. Non-thermal plasma may be used as a potential tool for applying ROS in precise doses to enhance vascularization. PMID:21653568

  5. In situ oxygen plasma cleaning of a PECVD source for hard disk overcoats

    NASA Astrophysics Data System (ADS)

    Ochs, D.; Cord, B.

    Reducing the thickness of the diamond-like carbon protective overcoat to a thickness of about 2-3 nm is one major key to increase the recording density of magnetic disk drives. Plasma-enhanced chemical vapor deposition (PECVD) deposited carbon layers have been shown to be denser and harder than those produced by conventional sputter deposition. One key problem of PECVD deposited carbon is the contamination of the carbon film by particles produced inside the carbon source after long-time operation. This particle production limits the runtime of the source drastically. To avoid this particle generation the source was cleaned by an intermittent in situ oxygen plasma process. The cleaning efficiency was investigated by recording the pressure change inside the source during the cleaning process caused by the CO production. The ratio of the cleaning time and the deposition time shows no significant dependence on the deposition time. An almost linear increase of the ratio with the acetylene flow was observed. This results from a higher deposition rate at higher acetylene flow, leading to a higher contamination inside the source. A strong dependence of the cleaning rate on the oxygen flow in the cleaning process was measured. More oxygen leads to a strong decrease of the needed cleaning time. Adding Ar gas to the oxygen discharge shows no improvement of the needed cleaning time. The cleaning process seems to be dependent only on the amount of reactive oxygen species in the discharge .

  6. Morphology of zirconia particles exposed to D.C. arc plasma jet

    NASA Technical Reports Server (NTRS)

    Zaplatynsky, Isidor

    1987-01-01

    Zirconia particles were sprayed into water with an arc plasma gun in order to determine the effect of various gun operating parameters on their morphology. The collected particles were examined by XRD and SEM techniques. A correlation was established between the content of spherical (molten) particles and the operating parameters by visual inspection and regression analysis. It was determined that the composition of the arc gas and the power input were the predominant parameters that affected the melting of zirconia particles.

  7. Plasma reactivity in high-power impulse magnetron sputtering through oxygen kinetics

    SciTech Connect

    Vitelaru, Catalin; Lundin, Daniel; Brenning, Nils; Minea, Tiberiu

    2013-09-02

    The atomic oxygen metastable dynamics in a Reactive High-Power Impulse Magnetron Sputtering (R-HiPIMS) discharge has been characterized using time-resolved diode laser absorption in an Ar/O{sub 2} gas mixture with a Ti target. Two plasma regions are identified: the ionization region (IR) close to the target and further out the diffusion region (DR), separated by a transition region. The μs temporal resolution allows identifying the main atomic oxygen production and destruction routes, which are found to be very different during the pulse as compared to the afterglow as deduced from their evolution in space and time.

  8. Numerical Experiments on Oxygen Plasma Focus: Scaling Laws of Soft X-Ray Yields

    NASA Astrophysics Data System (ADS)

    Akel, M.

    2013-08-01

    Numerical experiments have been investigated on UNU/ICTP PFF low energy plasma focus device with oxygen filling gas. In these numerical experiments, the temperature window of 119-260 eV has been used as a suitable temperature range for generating oxygen soft X-rays. The Lee model was applied to characterize the UNU/ICTP PFF plasma focus. The optimum soft X-ray yield (Ysxr) was found to be 0.75 J, with the corresponding efficiency of about 0.03 % at pressure of 2.36 Torr and the end axial speed was va = 5 cm/μs. The practical optimum combination of p0, z0 and `a' for oxygen Ysxr was found to be 0.69 Torr, 4.8 cm and 2.366 cm respectively, with the outer radius b = 3.2 cm. This combination gives Ysxr ~ 5 J, with the corresponding efficiency of about 0.16 %. Thus we expect to increase the oxygen Ysxr of UNU/ICTP PFF, without changing the capacitor bank, merely by changing the electrode configuration and operating pressure. Scaling laws on oxygen soft X-ray yield, in terms of storage energies E0, peak discharge current Ipeak and focus pinch current Ipinch were found over the range from 1 kJ to 1 MJ. It was found that the oxygen soft X-ray yields scale well with and for the low inductance (L0 = 30 nH) (where yields are in J and currents in kA). While the soft X-ray yield scaling laws in terms of storage energies were found to be as (E0 in kJ and Ysxr in J) with the scaling showing gradual deterioration as E0 rises over the range. The oxygen soft X-ray yield emitted from plasma focus is found to be about 8.7 kJ for storage energy of 1 MJ. The optimum efficiency for soft X-ray yield (1.1 %) is with capacitor bank energy of 120 kJ. This indicates that oxygen plasma focus is a good soft X-ray source when properly designed.

  9. Oxygen transport through polyethylene terephthalate (PET) coated with plasma-polymerized acetylene at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Wemlinger, Erik; Pedrow, Patrick; Garcia-Pérez, Manuel; Sablani, Shyam

    2011-10-01

    Moser et al. have shown that oxygen transport through polyethyleneterephthalate (PET) is reduced by a factor of up to 120 when, at reduced pressure, hydrogenated amorphous carbon film with thickness less than 100 nm is applied to the PET substrate. Our work includes using atmospheric pressure cold plasma to grow a plasma-polymerized acetylene film on PET substrate and measuring reductions in oxygen transport. The reactor utilizes corona discharges and is operated at 60 Hz with a maximum voltage of 10 kV RMS. Corona streamers emanate from an array of needles with an average radius of curvature of 50 μm. The reactor utilizes a cylindrical reaction chamber with a vertical orientation such that argon carrier gas and acetylene precursor gas are introduced at the top then pass through the cold plasma activation zone and then through a grounded stainless steel mesh. Acetylene radicals are incident on the PET substrate and form plasma-polymerized acetylene film. Moser et al. have shown that oxygen transport through polyethyleneterephthalate (PET) is reduced by a factor of up to 120 when, at reduced pressure, hydrogenated amorphous carbon film with thickness less than 100 nm is applied to the PET substrate. Our work includes using atmospheric pressure cold plasma to grow a plasma-polymerized acetylene film on PET substrate and measuring reductions in oxygen transport. The reactor utilizes corona discharges and is operated at 60 Hz with a maximum voltage of 10 kV RMS. Corona streamers emanate from an array of needles with an average radius of curvature of 50 μm. The reactor utilizes a cylindrical reaction chamber with a vertical orientation such that argon carrier gas and acetylene precursor gas are introduced at the top then pass through the cold plasma activation zone and then through a grounded stainless steel mesh. Acetylene radicals are incident on the PET substrate and form plasma-polymerized acetylene film. E.M. Moser, R. Urech, E. Hack, H. Künzli, E. Müller, Thin

  10. Cleaning of diamond nanoindentation probes with oxygen plasma and carbon dioxide snow

    SciTech Connect

    Morris, Dylan J.

    2009-12-15

    Diamond nanoindentation probes may perform thousands of indentations over years of service life. There is a broad agreement that the probes need frequent cleaning, but techniques for doing so are mostly anecdotes shared between experimentalists. In preparation for the measurement of the shape of a nanoindentation probe by a scanning probe microscope, cleaning by carbon dioxide snow jets and oxygen plasma was investigated. Repeated indentation on a thumbprint-contaminated surface formed a compound that was very resistant to removal by solvents, CO{sub 2} snow, and plasma. CO{sub 2} snow cleaning is found to be a generally effective cleaning procedure.

  11. Experimental Studies of DC-excited Plasma Discharges in HMDSN-SF6 Mixtures

    NASA Astrophysics Data System (ADS)

    Pinto Mota, Rogério; Godoy de Santana, Regiane; Algatti, Mauricio Antonio; Yzumi Honda, Roberto; Eiji Kayama, Milton

    1996-10-01

    The study of the structure of thin films from glow discharges and their correlation with discharge parameters is very important for choosing a pre- determined physical property. In this work, we performed measurements of electron temperature using a cylindrical Langmuir probe in DC discharges of HMDSN/SF6 for several mixtures with the proportion of SF6 varying from 0 to 50%, at a total pressure of 0.6 mbar. The voltage applied across the discharge was kept constant at 800V. The electron temperature varied from 0.6 to 2.0 eV, presenting a parabolic profile decreasing from the middle towards the edge of the electrode. The same behavior was also observed for the film thickness profile. The film growth rate varied from 12 to 155 Åmin, presenting a maximum at 20% SF_6. The FTIR spectra of the polymeric films showed the disappearance of the chemical bonds C-H, Si-H, and Si-CH3 for SF6 percentages above 30%, and the appearance C-F and Si-F chemical bonds.

  12. Observation of inactivation of Bacillus sbtilis spores under exposures of oxygen added argon atmospheric pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Shen, Jie; Cheng, Cheng; Zhao, Ying; Xiao, Dezhi; Lan, Yan; Xie, Hongbing; Cheng, Junli; Meng, Yuedong; Li, Jiangang; Chu, Paul K.

    2014-11-01

    The inactivation of Bacillus subtilis spores by an Ar plasma jet mixed with different amounts of oxygen is reported. 5.8 × 106 B. subtilis spores are sterilized by an Ar/O2 (8.7%) plasma jet after exposure for 2 min. The densities of ozone and oxygen radicals in the Ar/O2 plasma jet increase with oxygen concentration and are estimated by optical spectroscopy diagnostic. The malondialdehyde (MDA) test shows that oxygen radicals participate in bacterial inactivation. Scanning electron microscopy (SEM) reveals the deformation of the spore shape due to etching by oxygen radicals and the dependence of the degree of deformation on the density of oxygen radicals.

  13. Oxygen Plasma Modification of Poss-Coated Kapton(Registered TradeMark) HN Films

    NASA Technical Reports Server (NTRS)

    Wohl, C. J.; Belcher, M. A.; Ghose, S.; Connell, J. W.

    2008-01-01

    The surface energy of a material depends on both surface composition and topographic features. In an effort to modify the surface topography of Kapton(Registered TradeMark) HN film, organic solutions of a polyhedral oligomeric silsesquioxane, octakis(dimethylsilyloxy)silsesquioxane (POSS), were spray-coated onto the Kapton(Registered TradeMark) HN surface. Prior to POSS application, the Kapton(Registered TradeMark) HN film was activated by exposure to radio frequency (RF)-generated oxygen plasma. After POSS deposition and solvent evaporation, the films were exposed to various durations of RF-generated oxygen plasma to create a topographically rich surface. The modified films were characterized using optical microscopy, attenuated total reflection infrared (ATR-IR) spectroscopy, and high-resolution scanning electron microscopy (HRSEM). The physical properties of the modified films will be presented.

  14. Vibrational excitation in O2and Cl2inductively-coupled plasmas and DC discharges

    NASA Astrophysics Data System (ADS)

    Booth, Jean-Paul; Marinov, Daniil; Foucher, Mickael; Annusova, Adriana; Guerra, Vasco

    2016-09-01

    Low-energy electrons can interact with molecules via resonances to cause vibrational excitation with large cross-sections. Such processes can absorb significant energy from the plasma electrons, affecting the electron energy distribution and potentially (via vibration-translation (VT) energy transfer) causing substantial gas heating. The presence of vibrationally excited molecules may significant increase the rates of collisional processes, including electron dissociative attachment and electron impact dissociation into neutral atoms. However, the cross-sections of these processes are often poorly known since they are extremely difficult to measure directly, and reliable theoretical calculations are only now appearing for simple diatomic molecules. We have measured the vibrational distributions in discharges in pure O2 and pure Cl2, using high-sensitivity ultra-broadband ultraviolet absorption spectroscopy. In O2 plasmas significant vibrational excitation is observed, up to v'' =18, with a tail temperature of around 8000K. In Cl2 excitation is only observed up to v'' =3, and the distribution appears to be in local equilibrium with the gas translational temperature (up to 1500K). We are developing a detailed self-consistent 0D global model of these systems including vibrational excitation. Work performed in the LABEX Plas@par project, with financial state aid (ANR-11-IDEX-0004-02 and ANR-13-BS09-0019).

  15. Photooxidation of plasma polymerized polydimethylsiloxane film by 172 nm vacuum ultraviolet light irradiation in dilute oxygen

    SciTech Connect

    Ichikawa, S.

    2006-08-01

    Plasma polymerized polydimethylsiloxane films irradiated under different partial pressures of oxygen with a 172 nm vacuum ultraviolet light were investigated in order to clarify the roles of molecular oxygen and photons in photooxidation. The thickness, densities, surface roughness, elemental compositions, and molecular structures of the irradiated and unirradiated films were examined by using glazing incidence x-ray reflectivity, Rutherford backscattering, infrared, and x-ray absorption (XAS) spectroscopies. Photooxidation is hardly promoted by irradiation in a high vacuum of 1x10{sup -4} Pa, though photodesorption of the methyl group and formation of Si-H bonds were observed. Silica films thicker than 140 nm were formed at room temperature by irradiating them in low pressure oxygen gases. The degree of oxidation was smaller for the oxygen pressure of 10 kPa than for 83 Pa. Si K-edge XAS was performed to clarify the change of coordination environment of silicon by photooxidation in dilute oxygen flow containing less than 5 ppm of molecular oxygen.

  16. Surface monofunctionalized polymethyl pentene hollow fiber membranes by plasma treatment and hemocompatibility modification for membrane oxygenators

    NASA Astrophysics Data System (ADS)

    Huang, Xin; Wang, Weiping; Zheng, Zhi; Fan, Wenling; Mao, Chun; Shi, Jialiang; Li, Lei

    2016-01-01

    The hemocompatibility of polymethyl pentene (PMP) hollow fiber membranes (HFMs) was improved through surface modification for membrane oxygenator applications. The modification was performed stepwise with the following: (1) oxygen plasma treatment, (2) functionalization of monosort hydroxyl groups through NaBH4 reduction, and (3) grafting 2-methacryloyloxyethyl phosphorylcholine (MPC) or heparin. SEM, ATR-FTIR, and XPS analyses were conducted to confirm successful grafting during the modification. The hemocompatibility of PMP HFMs was analyzed and compared through protein adsorption, platelet adhesion, and coagulation tests. Pure CO2 and O2 permeation rates, as well as in vitro gas exchange rates, were determined to evaluate the mass transfer properties of PMP HFMs. SEM results showed that different nanofibril topographies were introduced on the HFM surface. ATR-FTIR and XPS spectra indicated the presence of functionalization of monosort hydroxyl group and the grafting of MPC and heparin. Hemocompatibility evaluation results showed that the modified PMP HFMs presented optimal hemocompatibility compared with pristine HFMs. Gas permeation results revealed that gas permeation flux increased in the modified HFMs because of dense surface etching during the plasma treatment. The results of in vitro gas exchange rates showed that all modified PMP HFMs presented decreased gas exchange rates because of potential surface fluid wetting. The proposed strategy exhibits a potential for fabricating membrane oxygenators for biomedical applications to prevent coagulation formation and alter plasma-induced surface topology and composition.

  17. Numerical Analysis of Microdischarge Oxygen Plasma and Prediction of Ozone Production Efficiency

    NASA Astrophysics Data System (ADS)

    Kawano, Satoyuki; Misaka, Takashi

    In this research, numerical simulation of oxygen plasma produced by dielectric barrier discharge (DBD) is made as a basic research for the application of bioprocesses such as sterilization. Numerical simulation is based on an appropriate modeling of microdischarges including 9 kinds of species and 54 chemical reactions. Behavior of the oxygen plasma is analyzed by finite difference method in two-dimensional computational region. The detailed characteristics of filamentous discharge formed between parallel dielectric surfaces which cover the electrodes are investigated. The qualitative tendency of the discharge formation process agrees with the previous experimental observation. Ozone production efficiency (OPE) is obtained and compared with experimental results. Dependency of reduced electric field E/n on OPE is investigated by comparing the numerical results with previous experimental results by other researcher, where E/n is the ratio of electric field EE to number density n of neutral molecule in the gas. It is confirmed that the present numerical simulation has practically enough accuracy for the evaluation of the OPE to optimize the oxygen plasma sterilization devices.

  18. Treatment of Second-Order Structures of Proteins Using Oxygen Radio Frequency Plasma

    NASA Astrophysics Data System (ADS)

    Hayashi, Nobuya; Nakahigashi, Akari; Liu, Hao; Goto, Masaaki

    2010-08-01

    Decomposition characteristics of second-order structures of proteins are determined using an oxygen radio frequency (RF) plasma sterilizer in order to prevent infectious proteins from contaminating medical equipment in hospitals. The removal of casein protein as a test protein with a concentration of 50 mg/cm2 on the plane substrate requires approximately 8 h when singlet atomic oxygen is irradiated. The peak intensity of Fourier transform infrared spectroscopy (FTIR) spectra of the β-sheet structures decreases at approximately the same rate as those of the α-helix and first-order structures of proteins. Active oxygen has a sufficient oxidation energy to dissociate hydrogen bonds within the β-sheet structure.

  19. Plasma potential of a moving ionization zone in DC magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Panjan, Matjaž; Anders, André

    2017-02-01

    Using movable emissive and floating probes, we determined the plasma and floating potentials of an ionization zone (spoke) in a direct current magnetron sputtering discharge. Measurements were recorded in a space and time resolved manner, which allowed us to make a three-dimensional representation of the plasma potential. From this information we could derive the related electric field, space charge, and the related spatial distribution of electron heating. The data reveal the existence of strong electric fields parallel and perpendicular to the target surface. The largest E-fields result from a double layer structure at the leading edge of the ionization zone. We suggest that the double layer plays a crucial role in the energization of electrons since electrons can gain several 10 eV of energy when crossing the double layer. We find sustained coupling between the potential structure, electron heating, and excitation and ionization processes as electrons drift over the magnetron target. The brightest region of an ionization zone is present right after the potential jump, where drifting electrons arrive and where most local electron heating occurs. The ionization zone intensity decays as electrons continue to drift in the Ez × B direction, losing energy by inelastic collisions; electrons become energized again as they cross the potential jump. This results in the elongated, arrowhead-like shape of the ionization zone. The ionization zone moves in the -Ez × B direction from which the to-be-heated electrons arrive and into which the heating region expands; the zone motion is dictated by the force of the local electric field on the ions at the leading edge of the ionization zone. We hypothesize that electron heating caused by the potential jump and physical processes associated with the double layer also apply to magnetrons at higher discharge power, including high power impulse magnetron sputtering.

  20. Afterglow chemistry of atmospheric-pressure helium-oxygen plasmas with humid air impurity

    NASA Astrophysics Data System (ADS)

    Murakami, Tomoyuki; Niemi, Kari; Gans, Timo; O'Connell, Deborah; Graham, William G.

    2014-04-01

    The formation of reactive species in the afterglow of a radio-frequency-driven atmospheric-pressure plasma in a fixed helium-oxygen feed gas mixture (He+0.5%O2) with humid air impurity (a few hundred ppm) is investigated by means of an extensive global plasma chemical kinetics model. As an original objective, we explore the effects of humid air impurity on the biologically relevant reactive species in an oxygen-dependent system. After a few milliseconds in the afterglow environment, the densities of atomic oxygen (O) decreases from 1015 to 1013 cm-3 and singlet delta molecular oxygen (O2(1D)) of the order of 1015 cm-3 decreases by a factor of two, while the ozone (O3) density increases from 1014 to 1015 cm-3. Electrons and oxygen ionic species, initially of the order of 1011 cm-3, recombine much faster on the time scale of some microseconds. The formation of atomic hydrogen (H), hydroxyl radical (OH), hydroperoxyl (HO2), hydrogen peroxide (H2O2), nitric oxide (NO) and nitric acid (HNO3) resulting from the humid air impurity as well as the influence on the afterglow chemistry is clarified with particular emphasis on the formation of dominant reactive oxygen species (ROS). The model suggests that the reactive species predominantly formed in the afterglow are major ROS O2(1D) and O3 (of the order of 1015 cm-3) and rather minor hydrogen- and nitrogen-based reactive species OH, H2O2, HNO3 and NO2/NO3, of which densities are comparable to the O-atom density (of the order of 1013 cm-3). Furthermore, the model quantitatively reproduces the experimental results of independent O and O3 density measurements.

  1. Morphological evolution of self-deposition Bi2Se3 nanosheets by oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Jia, Guozhi; Wu, Zengna; Wang, Peng; Yao, Jianghong; Chang, Kai

    2016-02-01

    Bi2Se3 nanosheets were successfully synthesized by a microwave-assisted approach in the presence of polyvinylpyrroli done at a temperature of 180 °C for 2 h. The thin film was prepared on a silicon wafer via a self-deposition process in a Bi2Se3 nanosheet ink solution using the evaporation-induced self-assembly method. The structure and morphology of the obtained products were characterized by X-ray diffraction, scanning electron microscopy (SEM), x-ray photoelectron spectroscopy, and Raman spectroscopy. The highly uniform Bi2Se3 particles could be formed by controlling the oxygen plasma treatment time. After the plasma pretreatment from 10 to 20 s, the surface of Bi2Se3 film evolved from the worm-like structure to particles. The highly uniform thin film was formed on further increasing the plasma treatment time, which is consistent with the observed SEM results. Several important processes can result in the morphological evolution of Bi2Se3 nanosheets: (1) formation of Bi2Se3 oxide layer; (2) self-assembly of oxide nanoparticles under the action of high-energy oxygen plasma; and (3) electrostatic interaction and etching mechanism.

  2. Tunable electrical properties of multilayer HfSe2 field effect transistors by oxygen plasma treatment.

    PubMed

    Kang, Moonshik; Rathi, Servin; Lee, Inyeal; Li, Lijun; Khan, Muhammad Atif; Lim, Dongsuk; Lee, Yoontae; Park, Jinwoo; Yun, Sun Jin; Youn, Doo-Hyeb; Jun, Chungsam; Kim, Gil-Ho

    2017-01-26

    HfSe2 field effect transistors are systematically studied in order to selectively tune their electrical properties by optimizing layer thickness and oxygen plasma treatment. The optimized plasma-treated HfSe2 field effect transistors showed a high on/off ratio improvement of four orders of magnitude, from 27 to 10(5), a field effect mobility increase from 2.16 to 3.04 cm(2) V(-1) s(-1), a subthreshold swing improvement from 30.6 to 4.8 V dec(-1), and a positive threshold voltage shift between depletion mode and enhancement mode, from -7.02 to 11.5 V. The plasma-treated HfSe2 photodetector also demonstrates a reasonable photoresponsivity from the visible to the near-infrared region of light.

  3. Real time sensor for monitoring oxygen in radio-frequency plasma applications.

    PubMed

    Milosavljevic, Vladimir; Faulkner, R; Hopkins, M B

    2007-10-17

    Real time closed loop control of plasma assisted semiconductor manufacturing processes has received significant attention in recent years. Therefore we have developed and tested a customized optical sensor based on buffer gas (argon) actinometry which has been used to determine relative densities of atomic and molecular oxygen in an Ar/O(2) radio-frequency ICP chamber. The operation and accuracy of our optical sensor compared favorably with a high resolution commercial spectrometer but at lower cost and exhibited improved actinometric performance over a low resolution commercial spectrometer. Furthermore, threshold tests have been performed on the validity of buffer gas based actinometry in Ar/O(2) ICP plasmas where Ar is no longer a trace gas through Xe actinometry. The plasma conditions for which this customized optical sensor can be used for closed loop control have been established.

  4. Effects of temperature and molecular oxygen on the use of atmospheric pressure plasma as a novel method for insect control.

    PubMed

    Donohue, Kevin V; Bures, Brian L; Bourham, Mohamed A; Roe, R Michael

    2008-04-01

    Helium atmospheric pressure plasma discharge (APPD) was previously shown to have insecticidal activity with a possible site of action on the insect nervous, neuromuscular system, or both. In the current study, methods to increase the insecticidal activity of plasma by using increased APPD temperature and the introduction of molecular oxygen were investigated for the first time. An increase in the helium plasma temperature from 37 to 50 degrees C increased the insecticidal activity of plasma for the control of the German cockroach, Blattella germanica (L.); western flower thrips, Frankliniella occidentalis (Pergande); and citrus mealybug, Planococcus citri (Risso). This increase in activity could not be explained by the increase in air temperature alone, and it suggests that the enhanced insecticidal activity resulted from increased ionization of the APPD and ion bombardment of the insect. Emission spectroscopy showed that the introduction of 0.5% oxygen into helium plasma produced ionic molecular oxygen at 559.7 and 597.3 nm. The introduction of oxygen to the APPD greatly increased the insecticidal activity of plasma for the citrus mealybug but not the German cockroach or western flower thrips. For the mealybug as an example, the mortality of a 60-s exposure of 37 degrees C helium plasma was 0% at 1 h after exposure and 100% under the same conditions after the introduction of oxygen. It seems that increases in temperature and the introduction of oxygen even at low levels can increase the insecticidal activity of plasma to varying degrees depending on the insect species. The symptomology of cockroach death for both hot plasma and plasma containing trace amounts of molecular oxygen continued to suggest that the site of action of APPD is the insect nervous system, neuromuscular system, or both.

  5. The effect of UV radiation from oxygen and argon plasma on the adhesion of organosilicon coatings on polypropylene

    NASA Astrophysics Data System (ADS)

    Jaritz, M.; Behm, H.; Hopmann, Ch; Kirchheim, D.; Mitschker, F.; Awakowicz, P.; Dahlmann, R.

    2017-01-01

    The influence of ultraviolet (UV) radiation from oxygen and argon pretreatment plasmas on a plastic substrate has not been fully understood yet. In particular, its influence on the adhesion properties has not been sufficiently researched so far. This paper addresses this issue by comparing the bond strength of a plasmapolymerized silicon organic coating (SiO x C y H z ) on polypropylene (PP) after oxygen and argon plasma pretreatment and pretreatment by UV radiation emitted by the same plasmas. The UV radiation is isolated from the other species from the plasma by means of a magnesium fluoride (MgF2) optical filter. It could be shown that UV radiation originating from an oxygen plasma has a significant impact on both substrate surface chemistry and coating adhesion. The same maximum bond strength enhancement can be reached by pretreating the polypropylene surface either with pulsed oxygen plasma, or with only the UV radiation from this oxygen plasma. Also, similar surface chemistry and topography modifications are induced. For argon plasma no significant influence of its UV radiation on the substrate could be observed in this study.

  6. Design of experiments on a DC Steady State Atmospheric Pressure Plasma Sterilizer

    NASA Astrophysics Data System (ADS)

    Alexeff, Igor; Balasundaram, Arun; Sawheny, Rapinder

    2009-11-01

    Our Resistive Barrier Discharge has been demonstrated to be successful on E. coli, Pseudomonas fluorescens (5RL), spores and bacteriophages. It has been tested successfully in sterilizing pagers at the St. Jude Research Hospital in Memphis, TN. In this recent work, we evaluate three primary factors in the atmospheric pressure resistive barrier discharge, hydrogen peroxide, charged ions and air (oxygen). The experiment used was Analysis of Variance (ANOVA) and regression analysis. The tests used 144 Petri Dishes and the bacteria used were E. coli. The hydrogen peroxide was used as a replacement for the water conductor on the resistive barrier discharge electrode. The charged ions were removed by a double charged wire mesh between the discharge and the Petri Dish. The air was displaced by a slow flow of nitrogen into the experimental area. The basic conclusions are that air, and charged ions are both extremely effective in killing bacteria. In addition, air and charged ions together strongly enhance each other. Hydrogen peroxide in our experiments did not enhance the kill rate.

  7. Microstructure and dry-sliding wear properties of DC plasma nitrided 17-4 PH stainless steel

    NASA Astrophysics Data System (ADS)

    Li, Gui-jiang; Wang, Jun; Li, Cong; Peng, Qian; Gao, Jian; Shen, Bao-luo

    2008-05-01

    An attempt that the precipitation hardening steel 17-4PH was conducted by DC plasma nitriding (DCPN) is made to develop a kind of candidate material for nuclear reactor. Nitriding process performed at temperature ⩽ 400 °C takes effect on creation of the layers composed of S-phase (expanded austenite) and αN‧ (expanded martensite). Up to the temperature of 420 °C, the S-phase peaks disappear due to the transformation occurrence (S-phase → αN‧ + CrN). For the samples nitrided at temperature ⩾ 450 °C, no evidence of αN‧ is found owing to a precipitation (αN‧ → α +CrN) taking place. For the 480 °C/4 h treated sample, it is the surface microhardness that plays the lead role in the wear rate reduction but the surface roughness; while for the 400 °C/4 h treated sample, it is both of the surface roughness and the S-phase formation. Dry sliding wear of the untreated 17-4PH is mainly characterized by strong adhesion, abrasion and oxidation mechanism. Samples nitrided at 400 °C which is dominated by slight abrasion and plastic deformation exhibit the best dry sliding wear resistance compared to the samples nitrided at other temperatures.

  8. Numerical study of an ArH2 gas mixture flowing inside and outside a dc plasma torch

    NASA Astrophysics Data System (ADS)

    Eichert, P.; Imbert, M.; Coddet, C.

    1998-12-01

    The flow of gas mixtures in a dc plasma torch is studied using the CFD PHOENICS (CFD PHOENICS, Berkeley, CA) code. In the model, the cold gas mixture (300 K), initially constituted of 85 vol% Ar and 15 vol% H, is introduced into a power input zone where it takes energy and is ejected in the surrounding atmosphere at constant pressure (105 Pa). The flow is assumed to be in chemical equilibrium. Equations of mass, momentum, and energy are discretized using a control-volume method. The turbulent flow is modeled by a k-ɛ two-equations model for the turbulent kinetic energy and its dissipation rate. Finally, the algebraic coupling equations set is solved by means of the SIMPLEST algorithm, implemented into the CFD code, using a hybrid interpolation scheme. Results concern the effect of the torch power on the ArH2 flow. The phenomenon is analyzed through the evolution of velocity and temperature inside and outside the torch. From these calculations, the effect of ambient gas entrainment by the jet is emphasized and a comparison of the level of entrained gas is made with experimental data.

  9. Effect of oxygen plasma treatment on CdSe/CdZnS quantum-dot light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Cho, Nam-Kwang; Yu, Jae-woong; Kim, Young Heon; Kang, Seong Jun

    2014-03-01

    Red-light-emitting diodes (LEDs) were fabricated using CdSe/CdZnS quantum dots (QDs). During the device fabrication process, the oxygen plasma treatment of the indium-tin oxide (ITO) surface was performed to improve the interfacial contact between the ITO anode and the hole injection layer. The device showed red emission at 622 nm, which was consistent with the dimensions of the QDs (band gap: 1.99 eV). The luminance was 108.77 cd/m2 and the current density was 230.2 mA/cm2 at an operating voltage of 7 V, when the oxygen plasma treatment was performed on the ITO surface. The luminance showed 207% improvement compared with that of LEDs fabricated without oxygen plasma treatment. These results suggested that the oxygen plasma treatment of the ITO surface improved the contact between ITO and PEDOT:PSS, and that the light emitting intensity was markedly improved.

  10. Surface cleaning for enhanced adhesion to packaging surfaces: Effect of oxygen and ammonia plasma

    SciTech Connect

    Gaddam, Sneha; Dong, Bin; Driver, Marcus; Kelber, Jeffry; Kazi, Haseeb

    2015-03-15

    The effects of direct plasma chemistries on carbon removal from silicon nitride (SiN{sub x}) and oxynitride (SiO{sub x}N{sub y}) surfaces have been studied by in-situ x-ray photoelectron spectroscopy (XPS) and ex-situ contact angle measurements. The data indicate that O{sub 2} and NH{sub 3} capacitively coupled plasmas are effective at removing adventitious carbon from silicon nitride (SiN{sub x}) and Si oxynitride (SiO{sub x}N{sub y}) surfaces. O{sub 2} plasma treatment results in the formation of a silica overlayer. In contrast, the exposure to NH{sub 3} plasma results in negligible additional oxidation of the SiN{sub x} or SiO{sub x}N{sub y} surface. Ex-situ contact angle measurements show that SiN{sub x} and SiO{sub x}N{sub y} surfaces exposed to oxygen plasma are initially more hydrophilic than surfaces exposed to NH{sub 3} plasma, indicating that the O{sub 2} plasma-induced SiO{sub 2} overlayer is highly reactive toward ambient. At longer ambient exposures (≳10 h), however, surfaces treated by either O{sub 2} or NH{sub 3} plasma exhibit similar steady state contact angles, correlated with rapid uptake of adventitious carbon, as determined by XPS. Surface passivation by exposure to molecular hydrogen prior to ambient exposure significantly retards the increase in contact angle upon exposure to ambient. The results suggest a practical route to enhancing the time available for effective bonding to surfaces in microelectronics packaging applications.

  11. Reactivity and analytical performance of oxygen as cell gas in inductively coupled plasma tandem mass spectrometry

    NASA Astrophysics Data System (ADS)

    Virgilio, Alex; Amais, Renata S.; Amaral, Clarice D. B.; Fialho, Lucimar L.; Schiavo, Daniela; Nóbrega, Joaquim A.

    2016-12-01

    The reactivity and analytical performance of O2 as cell gas in inductively coupled plasma tandem mass spectrometry was investigated. Selected analytes in a wide mass range were divided in three groups according to their reactivity: G1 represents elements with high oxygen affinity (Ce, La, P, Sc, Ti, and Y), G2 contains elements that may partially react with oxygen (As, Ba, Mo, Si, Sr, and V), and G3 comprises elements expected to be less reactive towards oxygen (Al, Bi, Cu, Mg, Pb, and Pd). On-mass and mass-shift modes were evaluated by monitoring atomic and metal oxide ions, respectively. Analytical signal profiles, oxide percentages, sensitivities and limits of detection for oxygen flow rates varying from 0.1 to 1.0 mL min- 1 were also studied. Group 1 elements plus As and V presented better sensitivities and LODs when measuring oxides, which were the major species for all flow rates evaluated. Molybdenum and Si oxides presented intermediate behavior and MoO fraction was up to 47% and limit of detection was the same as that obtained in on-mass mode. For others G2 and G3 elements, on-mass mode presented higher sensitivity and better LODs, with estimated oxide contents lower than 10%. In most cases, increasing oxygen flow rates led to lower sensitivities and worse LODs.

  12. Particle modelling of magnetically confined oxygen plasma in low pressure radio frequency discharge

    SciTech Connect

    Benyoucef, Djilali; Yousfi, Mohammed

    2015-01-15

    The main objective of this paper is the modelling and simulation of a radio frequency (RF) discharge in oxygen at low pressure and at room temperature, including the effect of crossed electric and magnetic fields for generation and confinement of oxygen plasma. The particle model takes into account one axial dimension along the electric field axis and three velocity components during the Monte Carlo treatment of the collisions between charged particles and background gas. The simulation by this developed code allows us not only to determine the electrodynamics characteristics of the RF discharge, but also to obtain kinetics and energetic description of reactive oxygen plasma at low pressure. These information are very important for the control of the deep reactive-ion etching technology of the silicon to manufacture capacitors with high density and for the deposition thick insulating films or thick metal to manufacture micro-coils. The simulation conditions are as follows: RF peak voltage of 200 V, frequency of 13.56 MHz, crossed magnetic field varying from 0 to 50 Gauss, and oxygen pressure of 13.8 Pa. In the presence of magnetic field, the results show an increase of the plasma density, a decrease of the electron mean energy, and also a reduction of the ratio between electron density and positive ion density. Finally in order to validate, the results are successfully compared with measurements already carried out in the literature. The conditions of comparison are from 100 to 300 V of the peak voltage at 13.56 MHz under a pressure of 13.8 Pa and a gap distance of 2.5 cm.

  13. DC and Structured Electric Fields Observed on the C/NOFS Satellite and Their Association with Longitude, Plasma Density, and Solar Activity

    NASA Technical Reports Server (NTRS)

    Pfaff, Robert; Freudenreich, H.; Rowland, D.; Klenzing, J.

    2012-01-01

    Observations of DC electric fields and associated E x B plasma drifts gathered by the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite are presented. We show statistical averages of the vector fields and resulting E x B plasma flows for the first three years of operations as a function of season, longitude, local time, and Fl 0.7 conditions. Magnetic field data from the VEFI science magnetometer are used to compute the plasma flows. Although typically displaying eastward and outward-directed fields during the day and westward and downward-directed fields at night, the data from DC electric field detector often reveal variations from this pattern that depend on longitude, solar activity, and plasma density. Clear "wave-4" tidal effects in both electric field components have been detected and will be presented. Zonal plasma drifts show a marked variation with solar activity and may be used as a proxy for neutral winds at night. Evidence for pre-reversal enhancements in the meridional drifts that depend on solar activity is present for some longitudes, and are corroborated by clear evidence in the plasma density data that the spacecraft journeyed below the F-peak during evenings when the rise in the ionosphere is most pronounced. In addition to DC electric fields, the data reveal considerable electric field structures at large scales (approx 100's of km) that are usually confined to the nightside. Although such electric field structures are typically associated with plasma density depletions and structures, what is surprising is the number of cases in which large amplitude, structured DC electric fields are observed without a significant plasma density counterpart structure, including their appearance at times when the ambient plasma density appears relatively quiescent. We investigate the mapping of structured electric fields along magnetic field lines from distant locations and consider

  14. Electron scattering cross sections for the modelling of oxygen-containing plasmas*

    NASA Astrophysics Data System (ADS)

    Alves, Luís Lemos; Coche, Philippe; Ridenti, Marco Antonio; Guerra, Vasco

    2016-06-01

    This work proposes a set of electron scattering cross sections for molecular and atomic oxygen, with interest for the modelling of oxygen-containing plasmas. These cross sections, compiled for kinetic energies up to 1 keV, are part of the IST-LISBON database with LXCat, being used as input data to the LoKI (LisbOn KInetics) numerical code. The cross sections for ground-state molecular oxygen describe elastic and inelastic collision mechanisms, the latter including rotational excitations/de-excitations (treated using either a discrete or a continuous approach), vibrational and electronic excitations (including dissociation), dissociative attachment and ionisation. This set yields calculated swarm parameters that reproduce measurements within 5-20% (transport parameters) and within a factor of 2 difference (Townsend coefficients), for reduced electric fields in the range 10-3-103 Td. The cross sections describing the kinetics of atomic oxygen by electron-impact comprise elastic mechanisms, electronic excitation and ionisation from O(3P) ground-state, dissociation of O2(X,a,b) (including dissociative ionisation and attachment) and of O3, and detachment. These cross sections are indirectly validated, together with other elementary data for oxygen, by comparing the densities of O((4S0)3 p 5P) obtained from the self-consistent modelling and from calibrated optical emission spectroscopy diagnostics of microwave-sustained micro-plasmas in dry air (80% N2: 20% O2), produced using a surface-wave excitation (2.45 GHz frequency) within a small radius capillary ( R = 345 μm) at low pressure ( p = 300 Pa). The calculated densities are in good qualitative agreement with measurements, overestimating them by a factor ˜1.5.

  15. Electron scattering cross sections for the modelling of oxygen-containing plasmas

    NASA Astrophysics Data System (ADS)

    Lemos Alves, Luís; Coche, Philippe; Ridenti, Marco Antonio; Guerra, Vasco

    2016-05-01

    This work proposes a set of electron scattering cross sections for molecular and atomic oxygen, with interest for the modelling of oxygen-containing plasmas. These cross sections, compiled for kinetic energies up to 1 keV, are part of the IST-LISBON database with LXCat, being used as input data to the LoKI (LisbOn KInetics) numerical code. The cross sections for ground-state molecular oxygen describe elastic and inelastic collision mechanisms, the latter including rotational excitations/de-excitations (treated using either a discrete or a continuous approach), vibrational and electronic excitations (including dissociation), dissociative attachment and ionisation. This set yields calculated swarm parameters that reproduce measurements within 5-20% (transport parameters) and within a factor of 2 difference (Townsend coefficients), for reduced electric fields in the range 10-3-103 Td. The cross sections describing the kinetics of atomic oxygen by electron-impact comprise elastic mechanisms, electronic excitation and ionisation from O(3P) ground-state, dissociation of O2(X,a,b) (including dissociative ionisation and attachment) and of O3, and detachment. These cross sections are indirectly validated, together with other elementary data for oxygen, by comparing the densities of O((4S0)3p 5P) obtained from the self-consistent modelling and from calibrated optical emission spectroscopy diagnostics of microwave-sustained micro-plasmas in dry air (80% N2: 20% O2), produced using a surface-wave excitation (2.45 GHz frequency) within a small radius capillary (R = 345 μm) at low pressure (p = 300 Pa). The calculated densities are in good qualitative agreement with measurements, overestimating them by a factor ˜1.5. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

  16. Plasma effects on the generation of reactive oxygen and nitrogen species in cancer cells in-vitro exposed by atmospheric pressure pulsed plasma jets

    NASA Astrophysics Data System (ADS)

    Kim, Sun Ja; Chung, T. H.

    2015-08-01

    Atmospheric pressure pulsed helium plasma jets are utilized for plasma-cell interactions. The effect of operating parameters such as applied voltage, pulse repetition frequency, and duty ratio on the generation of specific reactive oxygen and nitrogen species in gas and liquid phases and within cells is investigated. The apoptotic changes detected by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling assay in cells caused by plasma exposure are observed to correlate well with the levels of extracellular and intracellular reactive oxygen and nitrogen species.

  17. Plasma decay in high-voltage nanosecond discharges in oxygen-containing mixtures

    SciTech Connect

    Anokhin, E. M.; Popov, M. A.; Kochetov, I. V.; Aleksandrov, N. L.; Starikovskii, A. Yu.

    2016-01-15

    Plasma decay in high-voltage nanosecond discharges in CO{sub 2}: O{sub 2} and Ar: O{sub 2} mixtures at room gas temperature and a pressure of 10 Torr is studied experimentally and theoretically. The time dependence of the electron density during plasma decay is measured using microwave interferometry. The time evolution of the charged particle density, ion composition, and electron temperature is simulated numerically. It is shown that, under the given conditions, the discharge plasma is dominated for the most time by O{sub 2}{sup +} ions and plasma decay is determined by dissociative and three-body electron−ion recombination. As in the previous studies performed for air and oxygen plasmas, agreement between measurements and calculations is achieved only under the assumption that the rate of three-body recombination of molecular ions is much greater than that for atomic ions. The values of the rate constant of three-body recombination of electrons with O{sub 2}{sup +} ions in a wide range of electron temperatures (500–5500 K), as well as for thermal (300 K) electrons, are obtained by processing the experimental results.

  18. Reactive oxygen species in plasma against E. coli cells survival rate

    NASA Astrophysics Data System (ADS)

    Zhou, Ren-Wu; Zhang, Xian-Hui; Zong, Zi-Chao; Li, Jun-Xiong; Yang, Zhou-Bin; Liu, Dong-Ping; Yang, Si-Ze

    2015-08-01

    In this paper, we report on the contrastive analysis of inactivation efficiency of E. coli cells in solution with different disinfection methods. Compared with the hydrogen peroxide solution and the ozone gas, the atmospheric-pressure He plasma can completely kill the E. coli cells in the shortest time. The inactivation efficiency of E. coli cells in solution can be well described by using the chemical reaction rate model. X-ray photoelectron spectroscopy (XPS) analysis shows that the C-O or C=O content of the inactivated E. coli cell surface by plasma is predominantly increased, indicating the quantity of oxygen-containing species in plasma is more than those of two other methods, and then the C-C or C-H bonds can be broken, leading to the etching of organic compounds. Analysis also indicates that plasma-generated species can play a crucial role in the inactivation process by their direct reactions or the decompositions of reactive species, such as ozone into OH radicals in water, then reacting with E. coli cells. Project supported by the Natural Science Foundation of Fujian Province, China (Grant No. 2014J01025), the National Natural Science Foundation of China (Grant No. 11275261), and the Funds from the Fujian Provincial Key Laboratory for Plasma and Magnetic Resonance, China.

  19. [Effect of oxygen partial pressure on the band-gap of the TiO2 films prepared by DC reactive sputtering].

    PubMed

    Zhao, Qing-nan; Li, Chun-ling; Liu, Bao-shun; Zhao, Xiu-jian

    2004-05-01

    TiO2 films have been deposited on glass substrates using DC reactive magnetron sputtering at different oxygen partial pressures from 0.10 to 0.65 Pa. The photoluminescence (PL) spectra of the films were recorded. The results of the PL spectra showed that there were three emission peaks at 370, 472 and 514 nm for the films sputtered at 0.35 and 0.65 Pa, and there were two peaks at 370 and 490 nm for the films sputtered at 0.10 and 0.15 Pa. The band-gap for the films was 3.35 eV. For the films sputtered at 0.35 and 0.65 Pa there were two defect energy levels at 2.63 and 2.41 eV, corresponding to 0.72 and 0.94 eV below conduction band for the band-gap, respectively. For the films sputtered at 0.10 and 0.15 Pa, there was an energy band formed between 3.12 and 2.06 eV, corresponding to 0.23 and 1.29 eV below the conduction band. With increasing the oxygen partial pressure, the defect energy band changed to two energy levels, and the energy levels nearly disappeared for the film sputtered at 0.65 Pa of oxygen partial pressure.

  20. Bacterial adhesion to orthopaedic implant materials and a novel oxygen plasma modified PEEK surface.

    PubMed

    Rochford, E T J; Poulsson, A H C; Salavarrieta Varela, J; Lezuo, P; Richards, R G; Moriarty, T F

    2014-01-01

    Despite extensive use of polyetheretherketone (PEEK) in biomedical applications, information about bacterial adhesion to this biomaterial is limited. This study investigated Staphylococcus aureus and Staphylococcus epidermidis adhesion to injection moulded and machined PEEK OPTIMA(®) using a custom-built adhesion chamber with medical grade titanium and Thermanox for comparison. Additionally, bacterial adhesion to a novel oxygen plasma modified PEEK was also investigated in both a pre-operative model in physiological saline, and additionally in a post-operative model in human blood plasma. In the pre-operative model, the rougher machined PEEK had a significantly greater number of adherent bacteria compared to injection moulded PEEK. Bacterial adhesion to titanium and Thermanox was similar. Oxygen plasma surface modification of PEEK did not lead to a significant change in bacterial adhesion in the pre-operative contamination model, despite observed changes in surface characteristics. In the post-operative contamination model, S. aureus adhesion was increased from 5×10(5) CFU cm(-2) to approximately 1.3×10(7) CFU cm(-2) on the modified surfaces due to differential protein adhesion during the conditioning period. However, S. epidermidis adhesion to modified PEEK was less than to unmodified PEEK in the post-operative model. These results illustrate the importance of testing bacterial adhesion of several strains in both a pre-operative and post-operative, clinically relevant bacterial contamination model.

  1. In situ oxygen plasma cleaning of microswitch surfaces—comparison of Ti and graphite electrodes

    NASA Astrophysics Data System (ADS)

    Oh, Changho; Streller, Frank; Ashurst, W. Robert; Carpick, Robert W.; de Boer, Maarten P.

    2016-11-01

    Ohmic micro- and nanoswitches are of interest for a wide variety of applications including radio frequency communications and as low power complements to transistors. In these switches, it is of paramount importance to maintain surface cleanliness in order to prevent frequent failure by tribopolymer growth. To prepare surfaces, an oxygen plasma clean is expected to be beneficial compared to a high temperature vacuum bakeout because of shorter cleaning time (<5 min compared to ~24 h) and active removal of organic contaminants. We demonstrate that sputtering of the electrode material during oxygen plasma cleaning is a critical consideration for effective cleaning of switch surfaces. With Ti electrodes, a TiO x layer forms that increases electrical contact resistance. When plasma-cleaned using graphite electrodes, the resistance of Pt-coated microswitches exhibit a long lifetime with consistently low resistance (<0.5 Ω variation over 300 million cycles) if the test chamber is refilled with ultra-high purity nitrogen and if the devices are not exposed to laboratory air. Their current-voltage characteristic is also linear at the millivolt level. This is important for nanoswitches which will be operated in that range.

  2. DC and Wave Electric Fields and Other Plasma Parameters Observed on Two Sounding Rockets in the Dark Cusp During IMF Bz North and South Conditions

    NASA Technical Reports Server (NTRS)

    Pfaff, R. F.; Acuna, M.; Bounds, S.; Farrell, W.; Freudenreich, H.; Lepping, R.; Vondrak, R.; Maynard, N. C.; Moen, J.; Egeland, A.

    1997-01-01

    Two Black Brant IX sounding rockets were launched into the dark, dayside cusp near magnetic noon on December 2 and 3, 1997, from Ny Alesund, Spitzbergen at 79 N reaching altitudes of approximately 450 km. Real-time ground-based and Wind IMF data were used to determine the launch conditions. The first launch, with Bz north conditions, crossed into and back out of an open field region with merging poleward of the projected trajectory. The second flight, into Bz south conditions, was timed to coincide with an enhancement in the merging rate from a increase in the negative Bz, while the DMSP F13 satellite was situated slightly to the north of the rocket trajectory. Each payload returned DC electric and magnetic fields, plasma waves, energetic particles, photometer data, and thermal plasma data. Data from both flights will be shown, with an emphasis on the DC electric field results. In particular, the data gathered on December 2, 1997 will be used to discuss ionospheric signatures of merging and the open/closed character of the the cusp/low latitude boundary layer. In contrast, the data gathered on December 3, 1997 shows evidence of pulsed electric field structures which will be examined in the context of cusp plasma entry processes. Both data sets returned a rich variety of plasma waves, as well as optical emissions and thermal plasma data.

  3. DC and Wave Electric Fields and Other Plasma Parameters Observed on Two Sounding Rockets in the Dark Cusp during IMF BZ North and South Conditions

    NASA Technical Reports Server (NTRS)

    Pfaff, R. F.; Bounds, S.; Acuna, M.; Maynard, N. C.; Moen, J.; Egeland, A.; Holtet, J.; Maseide, K.; Sandholt, P. E.; Soraas, F.

    1999-01-01

    Two Black Brant IX sounding rockets were launched into the dark, dayside cusp near magnetic noon on December 2 and 3, 1997, from Ny Alesund, Spitzbergen at 79degN reaching altitudes of approximately 450 km. Real-time ground-based and Wind (interplanetary magnetic field) IMF data were used to determine the launch conditions. The first launch, with Bz north conditions, crossed into and back out of an open field region with merging poleward of the projected trajectory. The second flight, into Bz south conditions, was timed to coincide with an enhancement in the merging rate from a increase in the negative Bz, while the (Defense Meteorological Satellite Program) DMSP F13 satellite was situated slightly to the north of the rocket trajectory. Each payload returned DC electric and magnetic fields, plasma waves, energetic particles, photometer data, and thermal plasma data. Data from both flights will be shown, with an emphasis on the DC electric field results. In particular, the data gathered on December 2, 1997 will be used to discuss ionospheric signatures of merging and the open/closed character of the the cusp/low latitude boundary layer. In contrast, the data gathered on December 3, 1997 shows evidence of pulsed electric field structures which will be examined in the context of cusp plasma entry processes. Both data sets returned a rich variety of plasma waves, as well as optical emissions and thermal plasma data.

  4. DC and Wave Electric Fields and Other Plasma Parameters Observed on Two Sounding Rockets in the Dark Cusp during IMF Bz North and South Conditions

    NASA Technical Reports Server (NTRS)

    Pfaff, R. F.; Acuna, M.; Bounds, S.; Farrell, W.; Freudenreich, W.; Lepping, R.; Vondrak, R.; Maynard, N. C.; Moen, J.; Egeland, A.

    1999-01-01

    Two Black Brant IX sounding rockets were launched into the dark, dayside cusp near magnetic noon on December 2 and 3, 1997, from Ny Alesund, Spitzbergen at 79 deg N reaching altitudes of about 450 km. Real-time ground-based and Wind IMF data were used to determine the launch conditions. The first launch, with Bz north conditions, crossed into and back out of an open field region with merging poleward of the projected trajectory. The second flight, into Bz south conditions, was timed to coincide with an enhancement in the merging rate from a increase in the negative Bz, while the DMSP Fl 3 satellite was situated slightly to the north of the rocket trajectory. Each payload returned DC electric and magnetic fields, plasma waves, energetic particles, photometer data, and thermal plasma data. Data from both flights will be shown, with an emphasis on the DC electric field results. In particular, the data gathered on December 2, 1997 will be used to discuss ionospheric signatures of merging and the open/closed character of the the cusp/low latitude boundary layer. In contrast, the data gathered on December 3, 1997 shows evidence of pulsed electric field structures which will be examined in the context of cusp plasma entry processes. Both data sets returned a rich variety of plasma waves, as well as optical emissions and thermal plasma data.

  5. Growth of MoO3 films by oxygen plasma assisted molecular beam epitaxy

    SciTech Connect

    Altman, Eric I.; Droubay, Timothy C.; Chambers, Scott A.

    2002-07-22

    The growth of MoO₃ films on SrLaAlO₄(0 0 1), a substrate lattice-matched to b-MoO , by oxygen plasma assisted molecular beam epitaxy was characterized using reflection high-energy electron diffraction (RHEED), X-ray photoelectron spectroscopy, Xray diffraction (XRD), and atomic force and scanning tunneling microscopies (AFM and STM).It was found that the flux of reactive oxygen species to the surface was not high enough to maintain the proper stoichiometry, even at the lowest measurable deposition rates. Therefore, the films were grown by depositing Mo in small increments and then allowing the Mo to oxidize. At 675 K, the films grew epitaxially but in a three-dimensional manner. XRD of films grown under these conditions revealed atetragonal structure that has not been previously observed in bulk MoO₃ samples.

  6. Increased Oxygen Recovery from Sabatier Systems Using Plasma Pyrolysis Technology and Metal Hydride Separation

    NASA Technical Reports Server (NTRS)

    Greenwood, Zachary W.; Abney, Morgan B.; Perry, Jay L.; Miller, Lee A.; Dahl, Roger W.; Hadley, Neal M.; Wambolt, Spencer R.; Wheeler, Richard R.

    2015-01-01

    State-of-the-art life support carbon dioxide (CO2) reduction technology is based on the Sabatier reaction where less than 50% of the oxygen required for the crew is recovered from metabolic CO2. The reaction produces water as the primary product and methane as a byproduct. Oxygen recovery is constrained by the limited availability of reactant hydrogen. This is further exacerbated when Sabatier methane (CH4) is vented as a waste product resulting in a continuous loss of reactant hydrogen. Post-processing methane with the Plasma Pyrolysis Assembly (PPA) to recover hydrogen has the potential to dramatically increase oxygen recovery and thus drastically reduce the logistical challenges associated with oxygen resupply. The PPA decomposes methane into predominantly hydrogen and acetylene. Due to the highly unstable nature of acetylene, a separation system is necessary to purify hydrogen before it is recycled back to the Sabatier reactor. Testing and evaluation of a full-scale Third Generation PPA is reported and investigations into metal hydride hydrogen separation technology is discussed.

  7. Sterilization characteristics of dental instruments using oxygen plasma produced by narrow gap RF discharge

    NASA Astrophysics Data System (ADS)

    Sakai, Yasuhiro; Liu, Zhen; Goto, Masaaki; Hayashi, Nobuya

    2016-07-01

    Sterilization characteristics and material compatibility of low-pressure RF oxygen plasma sterilization method for dental instruments are investigated. Regarding the characteristics of the plasma sterilizer for dental instruments, it is small and can rapidly sterilize owing to a narrow gap discharge. Sterilization of vial-type biological indicators is achieved for the shortest treatment period of 40 min at an RF power of 80 W at a temperature of 70 °C. At a temperature lower than 60 °C, a sterilization period of 90 min is required using a water-cooled electrode. No surface modifications of dental instruments such as chemical composition and deterioration of fine crystals of a diamond bar were observed under a scanning electron microscope.

  8. Anchoring gold nanoparticles onto a mica surface by oxygen plasma ashing for sequential nanocomponent assembly

    NASA Astrophysics Data System (ADS)

    Takagi, Akihiko; Ojima, Kaoru; Mikamo, Eriko; Matsumoto, Takuya; Kawai, Tomoji

    2007-01-01

    Water-soluble gold nanoparticles were immobilized in both polar (water) and nonpolar (chloroform) liquids on hydrophilic mica surface by oxygen plasma ashing. It is then demonstrated that a DNA with a thiol at an extremity is attached to the immobilized nanoparticles due to the gold-thiol coupling and stretched in the flow direction of the following water rinse. This technique allows a sequential integration of nanoparticles and molecules for various solutions, since the nanoparticles remain on a solid surface rather than dissolve into the solution.

  9. Analysis by oxygen atom number density measurement of high-speed hydrophilic treatment of polyimide using atmospheric pressure microwave plasma

    SciTech Connect

    Ono, S.

    2015-03-30

    This paper describes the fundamental experimental data of the plasma surface modification of the polyimide using atmospheric pressure microwave plasma source. The experimental results were discussed from the point of view of the radical’s behavior, which significantly affects the modification mechanism. The purpose of the study is to examine how the value of the oxygen atom density will affect the hydrophilic treatment in the upstream region of the plasma where gas temperature is very high. The surface modification experiments were performed by setting the polyimide film sample in the downstream region of the plasma. The degree of the modification was measured by a water contact angle measurement. The water contact angle decreased less than 30 degrees within 1 second treatment time in the upstream region. Very high speed modification was observed. The reason of this high speed modification seems that the high density radical which contributes the surface modification exist in the upstream region of the plasma. This tendency is supposed to the measured relatively high electron density (~10{sup 15}cm{sup −3}) at the center of the plasma. We used the electric heating catalytic probe method for oxygen radical measurement. An absolute value of oxygen radical density was determined by catalytic probe measurement and the results show that ~10{sup 15}cm{sup −3} of the oxygen radical density in the upstream region and decreases toward downstream region. The experimental results of the relation of the oxygen radical density and hydrophilic modification of polyimide was discussed.

  10. Tensile strength of oxygen plasma-created surface layer of PDMS

    NASA Astrophysics Data System (ADS)

    Ohishi, Taiki; Noda, Haruka; Matsui, Tsubasa S.; Jile, Huge; Deguchi, Shinji

    2017-01-01

    Polydimethylsiloxane (PDMS) is a commonly used silicone elastomer with broad applications. Particularly for bioengineering use, PDMS is treated with oxygen plasma with which its surface is oxidized to allow positive interaction with water and live cells. In exchange for the acquisition of hydrophilicity, the oxidized PDMS becomes mechanically brittle so that resulting formation of cracks affects the system in various ways. However, tensile strength (TS), which is an inherent capacity of a material to withstand tensile loads before breaking and is thus a key parameter limiting the use of the material, remains unclear regarding oxidized PDMS. Here we determine the TS of oxide layers created on the surface of PDMS based on micro-stretch experiments using a custom-made device. We show that the surface layer displays cracks upon tensile loading of small strains of within 10% to have a TS of ~10-100 kPa, which is approximately two orders of magnitude lower than that of unmodified PDMS. We further show that the TS sharply decreases with oxidation duration to become highly brittle, while the thickness of the resulting oxide layer finally reaches a plateau even with prolonged plasma treatment. Consequently, we suggest that gradual surface modification of PDMS takes place only within a finite region even with prolonged plasma treatment, as distinct from previously held assumptions. These quantitative data provide critical design information for the oxide layer of plasma-hydrophilized PDMS.

  11. The different effects of oxygen and air DBD plasma byproducts on the degradation of methyl violet 5BN.

    PubMed

    Chen, Guangliang; Zhou, Mingyan; Chen, Shihua; Chen, Wenxing

    2009-12-30

    Through a novel design of the dielectric barrier discharge (DBD) plasma plume used in fabric-fiber surface modification, its discharge byproducts mainly including downstream gases and ultraviolet light were used to treat the dye solution. The different influence of oxygen and air DBD plasmas on the degradation of methyl violet 5BN (MV-5BN), which is widely used in textile industry, was investigated in this paper. The results showed that the cooperation between ultraviolet light and active species generated by the DBD plasma can decolorize MV-5BN effectively, and the chromophore peaks attributed to the -NN- bonds in MV-5BN molecule disappeared entirely when the azo dye solutions were treated for 25 min by the air and oxygen DBD plasmas. The degradation reaction followed an exponential kinetics over time, and the peak of aromatic derivatives at 209 nm in UV-vis spectra increased nearly 2.7 times when the dye solution was treated for 30 min by air DBD plasma. However, the oxygen DBD plasma could deplete the aromatic derivatives entirely. It is found that the formation of O(3) and NO(x) in the downstream gases of air and oxygen plasmas may be responsible for the different effects on the azo dye degradation.

  12. Effect of oxygen atoms dissociated by non-equilibrium plasma on flame of methane oxygen and argon pre-mixture gas

    NASA Astrophysics Data System (ADS)

    Akashi, Haruaki; Yoshinaga, Tomokazu; Sasaki, Koichi

    2014-10-01

    For more efficient way of combustion, plasma-assisted combustion has been investigated by many researchers. But it is very difficult to clarify the effect of plasma even on the flame of methane. Because there are many complex chemical reactions in combustion system. Sasaki et al. has reported that the flame length of methane and air premixed burner shortened by irradiating microwave power. They also measured emission from Second Positive Band System of nitrogen during the irradiation. The emission indicates existence of high energy electrons which are accelerated by the microwave. The high energy electrons also dissociate oxygen molecules easily and oxygen atom would have some effects on the flame. But the dissociation ratio of oxygen molecules by the non-equilibrium plasma is significantly low, compared to that in the combustion reaction. To clarify the effect of dissociated oxygen atoms on the flame, dependence of dissociation ratio of oxygen on the flame has been examined using CHEMKIN. It is found that in the case of low dissociation ratio of 10-6, the ignition of the flame becomes slightly earlier. It is also found that in the case of high dissociation ratio of 10-3, the ignition time becomes significantly earlier by almost half. This work was supported by KAKENHI (22340170).

  13. Analysis of plasma protein adsorption onto DC-Chol-DOPE cationic liposomes by HPLC-CHIP coupled to a Q-TOF mass spectrometer.

    PubMed

    Capriotti, Anna Laura; Caracciolo, Giulio; Caruso, Giuseppe; Cavaliere, Chiara; Pozzi, Daniela; Samperi, Roberto; Laganà, Aldo

    2010-12-01

    Plasma protein adsorption is regarded as a key factor in the in vivo organ distribution of intravenously administered drug carriers, and strongly depends on vector surface characteristics. The present study aimed to characterize the "protein corona" absorbed onto DC-Chol-DOPE cationic liposomes. This system was chosen because it is one of the most efficient and widely used non-viral formulations in vitro and a potential candidate for in vivo transfection of genetic material. After incubation of human plasma with cationic liposomes, nanoparticle-protein complex was separated from plasma by centrifugation. An integrated approach based on protein separation by one-dimensional 12% polyacrylamide gel electrophoresis followed by the automated HPLC-Chip technology coupled to a high-resolution mass spectrometer was employed for protein corona characterization. Thirty gel lanes, approximately 2 mm, were cut, digested and analyzed by HPLC-MS/MS. Fifty-eight human plasma proteins adsorbed onto DC-Chol-DOPE cationic liposomes were identified. The knowledge of the interactions of proteins with liposomes can be exploited for future controlled design of colloidal drug carriers and possibly in the controlled creation of biocompatible surfaces of other devices that come into contact with proteins in body fluids.

  14. Guided Discharge Path by Weak Ionized Region between Two Plasmas Produced by YAG Laser in Atmospheric Air Gap with Non-Uniform DC Electric Field

    NASA Astrophysics Data System (ADS)

    Okano, Daisuke

    1998-11-01

    Guided Discharge Path by Weak Ionized Region between Two Plasmas Produced by YAG Laser in Atmospheric Air Gap with Non-Uniform DC Electric Field*, Daisuke Okano, Kyushu Tokai University, 9-1-1 Toroku, Kumamoto, Japan. -----We have studied on guiding discharge path by weak ionized region between plasmas produced by a visible laser, that is, a YAG laser with wavelength 532nm, in an atmospheric air gap with DC non-uniform electric field using a rod-to-plate electrode. We succeeded in capturing the framing images in the temporal evolution on guiding discharge along the YAG laser light path. From the results of experiments, the region between two plasmas produced by a YAG laser can guide a discharge path, and the region between two plasmas on the laser light path is considered as well as a weak ionized one [1] produced by an excimer laser. [1]J.Sasaki, S.Kubodera, R.Ozaki and T.Uchiyama, J. Appl. Phys., 60 (1986) 3845. *This work was supported by Grant-in-Aid for Scientific Research (C)-no.10650295 of The Ministry of education, Science Sports and Culture in japan.

  15. Surface modification of argon/oxygen plasma treated vulcanized ethylene propylene diene polymethylene surfaces for improved adhesion with natural rubber

    NASA Astrophysics Data System (ADS)

    Basak, Ganesh C.; Bandyopadhyay, Abhijit; Neogi, Sudarsan; Bhowmick, Anil K.

    2011-01-01

    Vulcanized ethylene propylene diene polymethylene (EPDM) rubber surface was treated in a radio frequency capacitatively coupled low pressure argon/oxygen plasma to improve adhesion with compounded natural rubber (NR) during co-vulcanization. The plasma modified surfaces were analyzed by means of contact angle measurement, surface energy, attenuated total reflection-infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray sulfur mapping and atomic force microscopy. Several experimental variables such as plasma power, length of exposure time and composition of the argon-oxygen gas mixture were considered. It was delineated that plasma treatment changed both surface composition and roughness, and consequently increased peel strength. The change in surface composition was mainly ascribed to the formation of C-O and -Cdbnd O functional groups on the vulcanized surfaces. A maximum of 98% improvement in peel strength was observed after plasma treatment.

  16. Impact of plasma jet vacuum ultraviolet radiation on reactive oxygen species generation in bio-relevant liquids

    SciTech Connect

    Jablonowski, H.; Hammer, M. U.; Reuter, S.; Bussiahn, R.; Weltmann, K.-D.; Woedtke, Th. von

    2015-12-15

    Plasma medicine utilizes the combined interaction of plasma produced reactive components. These are reactive atoms, molecules, ions, metastable species, and radiation. Here, ultraviolet (UV, 100–400 nm) and, in particular, vacuum ultraviolet (VUV, 10–200 nm) radiation generated by an atmospheric pressure argon plasma jet were investigated regarding plasma emission, absorption in a humidified atmosphere and in solutions relevant for plasma medicine. The energy absorption was obtained for simple solutions like distilled water (dH{sub 2}O) or ultrapure water and sodium chloride (NaCl) solution as well as for more complex ones, for example, Rosewell Park Memorial Institute (RPMI 1640) cell culture media. As moderate stable reactive oxygen species, hydrogen peroxide (H{sub 2}O{sub 2}) was studied. Highly reactive oxygen radicals, namely, superoxide anion (O{sub 2}{sup •−}) and hydroxyl radicals ({sup •}OH), were investigated by the use of electron paramagnetic resonance spectroscopy. All species amounts were detected for three different treatment cases: Plasma jet generated VUV and UV radiation, plasma jet generated UV radiation without VUV part, and complete plasma jet including all reactive components additionally to VUV and UV radiation. It was found that a considerable amount of radicals are generated by the plasma generated photoemission. From the experiments, estimation on the low hazard potential of plasma generated VUV radiation is discussed.

  17. Impact of plasma jet vacuum ultraviolet radiation on reactive oxygen species generation in bio-relevant liquids

    NASA Astrophysics Data System (ADS)

    Jablonowski, H.; Bussiahn, R.; Hammer, M. U.; Weltmann, K.-D.; von Woedtke, Th.; Reuter, S.

    2015-12-01

    Plasma medicine utilizes the combined interaction of plasma produced reactive components. These are reactive atoms, molecules, ions, metastable species, and radiation. Here, ultraviolet (UV, 100-400 nm) and, in particular, vacuum ultraviolet (VUV, 10-200 nm) radiation generated by an atmospheric pressure argon plasma jet were investigated regarding plasma emission, absorption in a humidified atmosphere and in solutions relevant for plasma medicine. The energy absorption was obtained for simple solutions like distilled water (dH2O) or ultrapure water and sodium chloride (NaCl) solution as well as for more complex ones, for example, Rosewell Park Memorial Institute (RPMI 1640) cell culture media. As moderate stable reactive oxygen species, hydrogen peroxide (H2O2) was studied. Highly reactive oxygen radicals, namely, superoxide anion (O2•-) and hydroxyl radicals (•OH), were investigated by the use of electron paramagnetic resonance spectroscopy. All species amounts were detected for three different treatment cases: Plasma jet generated VUV and UV radiation, plasma jet generated UV radiation without VUV part, and complete plasma jet including all reactive components additionally to VUV and UV radiation. It was found that a considerable amount of radicals are generated by the plasma generated photoemission. From the experiments, estimation on the low hazard potential of plasma generated VUV radiation is discussed.

  18. Plasma processing of ? in a hydrogen/oxygen radio-frequency discharge

    NASA Astrophysics Data System (ADS)

    Turcicová, H.; Perina, V.; Vacík, J.; Cervená, J.; Zemek, J.; Zelezný, V.; Arend, H.

    1998-05-01

    Monocrystalline 0022-3727/31/9/004/img10 was processed in a radio-frequency (27.12 MHz) discharge in hydrogen and subsequently in oxygen and the composition of the thus produced surface layers evaluated. The hydrogen plasma treatment caused a heavy blackening of the sample due to chemical reduction. At low 0022-3727/31/9/004/img11 pressures (0022-3727/31/9/004/img12 Torr) the niobate structure on the sample surface was completely destroyed; only niobium and its oxides remained on the surface. At higher pressures (0022-3727/31/9/004/img13 Torr) the niobate structure was preserved. Hydrogenation of the surface layer was found which persisted up to 5000022-3727/31/9/004/img14C. Subsequent treatment in an oxygen plasma under similar processing conditions brought about the restoration of the transparency of the sample. The following methods were used for the modified surface structure analysis: neutron depth profiling, Rutherford backscattering, x-ray photoelectron spectroscopy and VIS and IR spectrometry.

  19. Determination of the neutral oxygen atom density in a plasma reactor loaded with metal samples

    NASA Astrophysics Data System (ADS)

    Mozetic, Miran; Cvelbar, Uros

    2009-08-01

    The density of neutral oxygen atoms was determined during processing of metal samples in a plasma reactor. The reactor was a Pyrex tube with an inner diameter of 11 cm and a length of 30 cm. Plasma was created by an inductively coupled radiofrequency generator operating at a frequency of 27.12 MHz and output power up to 500 W. The O density was measured at the edge of the glass tube with a copper fiber optics catalytic probe. The O atom density in the empty tube depended on pressure and was between 4 and 7 × 1021 m-3. The maximum O density was at a pressure of about 150 Pa, while the dissociation fraction of O2 molecules was maximal at the lowest pressure and decreased with increasing pressure. At about 300 Pa it dropped below 10%. The measurements were repeated in the chamber loaded with different metallic samples. In these cases, the density of oxygen atoms was lower than that in the empty chamber. The results were explained by a drain of O atoms caused by heterogeneous recombination on the samples.

  20. Preparation of Ag-containing diamond-like carbon films on the interior surface of tubes by a combined method of plasma source ion implantation and DC sputtering

    NASA Astrophysics Data System (ADS)

    Hatada, R.; Flege, S.; Bobrich, A.; Ensinger, W.; Dietz, C.; Baba, K.; Sawase, T.; Watamoto, T.; Matsutani, T.

    2014-08-01

    Adhesive diamond-like carbon (DLC) films can be prepared by plasma source ion implantation (PSII), which is also suitable for the treatment of the inner surface of a tube. Incorporation of a metal into the DLC film provides a possibility to change the characteristics of the DLC film. One source for the metal is DC sputtering. In this study PSII and DC sputtering were combined to prepare DLC films containing low concentrations of Ag on the interior surfaces of stainless steel tubes. A DLC film was deposited using a C2H4 plasma with the help of an auxiliary electrode inside of the tube. This electrode was then used as a target for the DC sputtering. A mixture of the gases Ar and C2H4 was used to sputter the silver. By changing the gas flow ratios and process time, the resulting Ag content of the films could be varied. Sample characterizations were performed by X-ray photoelectron spectroscopy, secondary ion mass spectrometry, atomic force microscopy and Raman spectroscopy. Additionally, a ball-on-disk test was performed to investigate the tribological properties of the films. The antibacterial activity was determined using Staphylococcus aureus bacteria.

  1. In vivo stimulation of bone formation by aluminum and oxygen plasma surface-modified magnesium implants.

    PubMed

    Wong, Hoi Man; Zhao, Ying; Tam, Vivian; Wu, Shuilin; Chu, Paul K; Zheng, Yufeng; To, Michael Kai Tsun; Leung, Frankie K L; Luk, Keith D K; Cheung, Kenneth M C; Yeung, Kelvin W K

    2013-12-01

    A newly developed magnesium implant is used to stimulate bone formation in vivo. The magnesium implant after undergoing dual aluminum and oxygen plasma implantation is able to suppress rapid corrosion, leaching of magnesium ions, as well as hydrogen gas release from the biodegradable alloy in simulated body fluid (SBF). No released aluminum is detected from the SBF extract and enhanced corrosion resistance properties are confirmed by electrochemical tests. In vitro studies reveal enhanced growth of GFP mouse osteoblasts on the aluminum oxide coated sample, but not on the untreated sample. In addition to that a small amount (50 ppm) of magnesium ions can enhance osteogenic differentiation as reported previously, our present data show a low concentration of hydrogen can give rise to the same effect. To compare the bone volume change between the plasma-treated magnesium implant and untreated control, micro-computed tomography is performed and the plasma-treated implant is found to induce significant new bone formation adjacent to the implant from day 1 until the end of the animal study. On the contrary, bone loss is observed during the first week post-operation from the untreated magnesium sample. Owing to the protection offered by the Al2O3 layer, the plasma-treated implant degrades more slowly and the small amount of released magnesium ions stimulate new bone formation locally as revealed by histological analyses. Scanning electron microscopy discloses that the Al2O3 layer at the bone-implant interface is still present two months after implantation. In addition, no inflammation or tissue necrosis is observed from both treated and untreated implants. These promising results suggest that the plasma-treated magnesium implant can stimulate bone formation in vivo in a minimal invasive way and without causing post-operative complications.

  2. Titanium dioxide nanoparticles increase plasma glucose via reactive oxygen species-induced insulin resistance in mice.

    PubMed

    Hu, Hailong; Guo, Qian; Wang, Changlin; Ma, Xiao; He, Hongjuan; Oh, Yuri; Feng, Yujie; Wu, Qiong; Gu, Ning

    2015-10-01

    There have been few reports about the possible toxic effects of titanium dioxide (TiO2 ) nanoparticles on the endocrine system. We explored the endocrine effects of oral administration to mice of anatase TiO2 nanoparticles (0, 64 and 320 mg kg(-1) body weight per day to control, low-dose and high-dose groups, respectively, 7 days per week for 14 weeks). TiO2 nanoparticles were characterized by scanning and transmission electron microscopy (TEM) and dynamic light scattering (DLS), and their physiological distribution was investigated by inductively coupled plasma. Biochemical analyzes included plasma glucose, insulin, heart blood triglycerides (TG), free fatty acid (FFA), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), total cholesterol (TC), tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6 and reactive oxygen species (ROS)-related markers (total SOD, GSH and MDA). Phosphorylation of IRS1, Akt, JNK1, and p38 MAPK were analyzed by western blotting. Increased titanium levels were found in the liver, spleen, small intestine, kidney and pancreas. Biochemical analyzes showed that plasma glucose significantly increased whereas there was no difference in plasma insulin secretion. Increased ROS levels were found in serum and the liver, as evidenced by reduced total SOD activity and GSH level and increased MDA content. Western blotting showed that oral administration of TiO2 nanoparticles induced insulin resistance (IR) in mouse liver, shown by increased phosphorylation of IRS1 (Ser307) and reduced phosphorylation of Akt (Ser473). The pathway by which TiO2 nanoparticles increase ROS-induced IR were included in the inflammatory response and phosphokinase, as shown by increased serum levels of TNF-α and IL-6 and increased phosphorylation of JNK1 and p38 MAPK in liver. These results show that oral administration of TiO2 nanoparticles increases ROS, resulting in IR and increasing plasma glucose in mice.

  3. Microwave-Plasma-Coupled Re-Ignition of Methane-and-Oxygen Mixture Under Auto-Ignition Temperature

    DTIC Science & Technology

    2011-12-01

    plasma coupling (60-SCCM total flow rate at φ = 1.1). in situ fuel reforming (to hydrogen and carbon monoxide), as well as the temperature increase...Adamovich, “Non- thermal ignition of premixed hydrocarbon-air flows by nonequilibrium rf plasma ,” J. Propulsion Power, vol. 21, no. 4, pp. 583–590, Jul./Aug...IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 39, NO. 12, DECEMBER 2011 3307 Microwave- Plasma -Coupled Re-Ignition of Methane-and-Oxygen Mixture Under

  4. STUDENT AWARD FINALIST: Oxygen Pathways in Streamer Discharge for Transient Plasma Ignition

    NASA Astrophysics Data System (ADS)

    Pendleton, S. J.; Bowman, S.; Singleton, D.; Watrous, J.; Carter, C.; Lempert, W.; Gundersen, M. A.

    2011-10-01

    The use of streamers for the ignition of fuels, also known as transient plasma ignition (TPI), has been shown in a variety of engines to improve combustion through decreased ignition delay, increased lean burn capability and increased energy release relative to conventional spark ignition. The mechanisms behind these improvements, however, remain poorly understood. Temperature measurements by optical emission spectroscopy demonstrate that ignition by TPI is a nonthermal process, and thus is almost entirely dependent on the production and presence of electron impact-created active species in the discharge afterglow. Of particular interest are active oxygen species due to their relatively long lifetimes at high pressures and the pivotal role they play in combustion reactions. In order to elucidate the oxygen pathways, here we report the investigation of the temporal evolution of the populations of atomic oxygen and ozone by use of two-photon absorption laser induced fluorescence (TALIF) and UV absorption, respectively. Experimental results are presented and compared to kinetic modeling of the streamers. Future experiments are proposed to better understand the physics behind TPI. Supported by NSF, AFOSR, NumerEx-ONR, AFRL-WPAFB.

  5. Atomic oxygen recombination on the ODS PM 1000 at high temperature under air plasma

    NASA Astrophysics Data System (ADS)

    Balat-Pichelin, M.; Bêche, E.

    2010-06-01

    High temperature materials are necessary for the design of primary heat shields for future reusable space vehicles re-entering atmospheric planet at hypersonic velocity. During the re-entry phase on earth, one of the most important phenomena occurring on the heat shield is the recombination of atomic oxygen and this phenomenon is more or less catalyzed by the material of the heat shield. PM 1000 is planned to be use on the EXPERT capsule to study in real conditions its catalycity. Before the flight, it is necessary to perform measurements on ground test facility. Experimental data of the recombination coefficient of atomic oxygen under air plasma flow were obtained in the diffusion reactor MESOX on pre-oxidized PM 1000, for two total pressures 300 and 1000 Pa in the temperature range (850-1650 K) using actinometry and optical emission spectroscopy. In this investigation, the evolution of the recombination coefficient is dependent of temperature, pressure level and also of the chemical composition of the surface leading to one order of magnitude for a given temperature. The recombination coefficient is increasing with temperature and also dependent on the static pressure. The surface change due to the plasma exposure is inspected with SEM, XRD and XPS. As chromium oxide is the main part of the oxide layer formed during the oxidation in air plasma conditions, a sintered Cr 2O 3 sample was elaborated from powders to compare the data of the recombination coefficient obtained on PM 1000. Pre- and post-test analyses on the several materials were carried out using SEM, WDS, XRD and XPS.

  6. Aluminium metallisation of argon and oxygen plasma-modified polycarbonate thin film surfaces

    NASA Astrophysics Data System (ADS)

    Rastomjee, C. S.; Keil, M.; Sotobayashi, H.; Bradshaw, A. M.; Lamont, C. L. A.; Gador, D.; Umbach, E.

    1998-12-01

    The influence of plasma treatment on the metallisation of polycarbonate surfaces was studied using X-ray absorption spectroscopy (XAFS) and core level X-ray photoelectron spectroscopy (XPS). Thin films of two different molecules were chosen: bis-phenol-A polycarbonate with phenol endgroups (P-PC) prepared ex situ by the spin-coating technique onto MoTe 2{0001}surfaces, and the model compound bis-phenol-A polycarbonate ( n=1) with tert-butyl phenyl endgroups (tBP-PC) evaporated in situ in UHV onto Cu{110}, Ag{100} and Ag{111} surfaces with film thicknesses of up to several monolayers. Surfaces of untreated samples and of samples which were pre-treated with either an inert argon or a reactive oxygen microwave plasma were metallised with Al (evaporated by electron beam heating) at film thicknesses ranging from the sub-monolayer region up to several monolayers. For the untreated surface, XAFS and XPS spectra suggest that the Al reacts with the carbonate groups leading to a breaking of the CO double bonds (and/or a reduction in bond order) as well as formation of Al oxide, Al hydroxide and Al-O-C linkages. A study of the time-dependent oxidation of the evaporated Al leads to the conclusion that Al slowly diffuses to the reactive sites in the first few subsurface layers of the polymer. Argon plasma treatment of samples leads to a reduction in the number of carbonyl groups in the near surface region. After metal deposition a higher ratio of metallic, non-reacted, Al was observed covering the polycarbonate surface and the diffusion rate into the polymer bulk seems to be higher than in the case of the untreated surface. Oxygen plasma treatment leads to the creation of additional CO containing species which also react with the Al in the subsequent metallisation process. Here, the ratio of oxidised Al on the polymer surface is higher than observed for untreated and argon plasma pre-treated polymer surfaces.

  7. Etching of CVD diamond films using oxygen ions in ECR plasma

    NASA Astrophysics Data System (ADS)

    Ma, Zhibin; Wu, Jun; Shen, Wulin; Yan, Lei; Pan, Xin; Wang, Jianhua

    2014-01-01

    Etching with oxygen ions produced by ECR plasma with an asymmetric magnetic mirror field was investigated as a potential technique for polishing CVD diamond. The morphology, structure and roughness of the diamond film surface before and after etching were analyzed respectively using scanning electron microscope (SEM), Raman spectroscopy and surface roughness measuring instrument. It was found that the ridges on diamond surface had been preferentially etched away and thereby the surface roughness decreased from 3.061 to 1.083 μm after 4 h etching. Meanwhile, non-diamond phase appeared on surface and dramatically increased with the extending of etching time. In order to fundamentally understand the etching mechanism, an etching model of diamond film was reasonably proposed on the ground of the experimental results and the theory of plasma physics. The as-generated ions taking screw movement are firstly accelerated along the magnetic field lines in the plasma and collisional presheath, and then deflected from their route towards the diamond film in the MP. When coming into Debye sheath, the motion of ions will be deflected further and strongly accelerated by electric field in the direction normal to the (1 1 1) crystal facets. This process gave rise to energetic ion bombardment towards every (1 1 1) crystal face, and thereby caused preferential etching of pyramidal crystallites.

  8. Oxygen activation at the plasma membrane: relation between superoxide and hydroxyl radical production by isolated membranes.

    PubMed

    Heyno, Eiri; Mary, Véronique; Schopfer, Peter; Krieger-Liszkay, Anja

    2011-07-01

    Production of reactive oxygen species (hydroxyl radicals, superoxide radicals and hydrogen peroxide) was studied using EPR spin-trapping techniques and specific dyes in isolated plasma membranes from the growing and the non-growing zones of hypocotyls and roots of etiolated soybean seedlings as well as coleoptiles and roots of etiolated maize seedlings. NAD(P)H mediated the production of superoxide in all plasma membrane samples. Hydroxyl radicals were only produced by the membranes of the hypocotyl growing zone when a Fenton catalyst (FeEDTA) was present. By contrast, in membranes from other parts of the seedlings a low rate of spontaneous hydroxyl radical formation was observed due to the presence of small amounts of tightly bound peroxidase. It is concluded that apoplastic hydroxyl radical generation depends fully, or for the most part, on peroxidase localized in the cell wall. In soybean plasma membranes from the growing zone of the hypocotyl pharmacological tests showed that the superoxide production could potentially be attributed to the action of at least two enzymes, an NADPH oxidase and, in the presence of menadione, a quinone reductase.

  9. Superhydrophilic poly(L-lactic acid) electrospun membranes for biomedical applications obtained by argon and oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Correia, D. M.; Ribeiro, C.; Botelho, G.; Borges, J.; Lopes, C.; Vaz, F.; Carabineiro, S. A. C.; Machado, A. V.; Lanceros-Méndez, S.

    2016-05-01

    Poly(L-lactic acid), PLLA, electrospun membranes and films were plasma treated at different times and power with argon (Ar) and oxygen (O2), independently, in order to modify the hydrophobic nature of the PLLA membranes. Both Ar and O2 plasma treatments promote an increase in fiber average size of the electrospun membranes from 830 ± 282 nm to 866 ± 361 and 1179 ± 397 nm, respectively, for the maximum exposure time (970 s) and power (100 W). No influence of plasma treatment was detected in the physical-chemical characteristics of PLLA, such as chemical structure, polymer phase or degree of crystallinity. On the other hand, an increase in the roughness of the films was obtained both with argon and oxygen plasma treatments. Surface wettability studies revealed a decrease in the contact angle with increasing plasma treatment time for a given power and with increasing power for a given time in membranes and films and superhydrophilic electrospun fiber membranes were obtained. Results showed that the argon and oxygen plasma treatments can be used to tailor hydrophilicity of PLLA membranes for biomedical applications. MTT assay results indicated that plasma treatments under Ar and O2 do not influence the metabolic activity of MC3T3-E1 pre-osteoblast cells.

  10. Characterization of oxygenated metabolites of ginsenoside Rg1 in plasma and urine of rat.

    PubMed

    Wang, Jing-Rong; Tong, Tian-Tian; Yau, Lee-Fong; Chen, Cheng-Yu; Bai, Li-Ping; Ma, Jing; Hu, Ming; Liu, Liang; Jiang, Zhi-Hong

    2016-07-15

    This study describes the characterization of oxygenated metabolites of ginsenoside Rg1 in rat urine and plasma. These in vivo metabolites were profiled by using UHPLC-QTOF MS-based method. On the basis of high-resolution MS/MS data, and comparison with chemically synthesized authentic compounds, nine oxygenated metabolites of Rg1 were characterized as vinaginsenosides 21 and 22 (M1 and M2), vinaginsenoside R15 (M3), 6-O-(β-d-glucopyranosyl)-20-O-(β-d-glucopyranosyl) 3β, 6α, 12β, 20(S)-tetrahydroxy-24ξ-hydroxydammar-25-ene (M4 and M5), floralginsenoside A (M7 and M8), floralginsenoside B (M9) and epoxyginsenoside Rg1 (M13), respectively. Among these metabolites, M4, M5 and M13 are new ginsenosides and others were detected as in vivo metabolites of Rg1 for the first time. In addition, a series of oxygenated metabolites of Rh1 and deglycosylated metabolite of Rg1, were observed and characterized by comparing with compounds synthesized by us, which revealed an association between C-20 configuration and the extent of oxidation metabolism. Appearance of all these metabolites in blood stream and urine after i.v. dosing and oral administration of Rg1 was further examined, which clearly showed that mono-oxygenated metabolites of Rg1 were major circulating metabolites at the early stage after dosing. Characterization of exact chemical structures of these circulating metabolites contribute greatly to our understanding of chemical exposure after consumption of ginseng products, and provide valuable information for explaining multiple bioactivities of ginseng products.

  11. Persistent Longitudinal Variations of Plasma Density and DC Electric Fields in the Low Latitude Ionosphere Observed with Probes on the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Klenzing, J.; Rowland, D.; Liebrecht, C.; Bromund, K.; Roddy, P.

    2010-01-01

    Continuous measurements using in situ probes on consecutive orbits of the C/N0FS satellite reveal that the plasma density is persistently organized by longitude, in both day and night conditions and at all locations within the satellite orbit, defined by its perigee and apogee of 401 km and 867 km, respectively, and its inclination of 13 degrees. Typical variations are a factor of 2 or 3 compared to mean values. Furthermore, simultaneous observations of DC electric fields and their associated E x B drifts in the low latitude ionosphere also reveal that their amplitudes are also strongly organized by longitude in a similar fashion. The drift variations with longitude are particularly pronounced in the meridional component perpendicular to the magnetic field although they are also present in the zonal component as well. The longitudes of the peak meridional drift and density values are significantly out of phase with respect to each other. Time constants for the plasma accumulation at higher altitudes with respect to the vertical drift velocity must be taken into account in order to properly interpret the detailed comparisons of the phase relationship of the plasma density and plasma velocity variations. Although for a given period corresponding to that of several days, typically one longitude region dominates the structuring of the plasma density and plasma drift data, there is also evidence for variations organized about multiple longitudes at the same time. Statistical averages will be shown that suggest a tidal "wave 4" structuring is present in both the plasma drift and plasma density data. We interpret the apparent association of the modulation of the E x B drifts with longitude as well as that of the ambient plasma density as a manifestation of tidal forces at work in the low latitude upper atmosphere. The observations demonstrate how the high duty cycle of the C/NOFS observations and its unique orbit expose fundamental processes at work in the low latitude

  12. Surface Modification of C3N4 through Oxygen-Plasma Treatment: A Simple Way toward Excellent Hydrophilicity.

    PubMed

    Bu, Xiuming; Li, Jipeng; Yang, Siwei; Sun, Jing; Deng, Yuan; Yang, Yucheng; Wang, Gang; Peng, Zheng; He, Peng; Wang, Xianying; Ding, Guqiao; Yang, Junhe; Xie, Xiaoming

    2016-11-16

    We developed a universal method to prepare hydrophilic carbon nitrogen (C3N4) nanosheets. By treating C3N4 nanosheets with oxygen plasma, hydroxylamine groups (N-OH) with intense protonation could be introduced on the surface; moreover, the content of N-OH groups increased linearly with the oxygen-plasma treatment time. Thanks to the excellent hydrophilicity, uniformly dispersed C3N4 solution were prepared, which was further translated into C3N4 paper by simple vacuum filtration. Pure C3N4 paper with good stability, excellent hydrophilicity, and biocompatibility were proved to have excellent performance in tissue repair. Further research demonstrated that the oxygen-plasma treatment method can also introduce N-OH groups into other nitrogen-containing carbon materials (NCMs) such as N-doped graphene, N-doped carbon nanotube, and C2N, which offers a new perspective on the surface modification and functionalization of these carbon nanomaterials.

  13. Raman spectra investigation of the defects of chemical vapor deposited multilayer graphene and modified by oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Li, Zongyao; Xu, Yu; Cao, Bing; Qi, Lin; He, Shunyu; Wang, Chinhua; Zhang, Jicai; Wang, Jianfeng; Xu, Ke

    2016-11-01

    Graphene, a two dimensional material, can be modified its properties by defects engineering. Here, we present Raman spectra studies of the multilayer graphene (MLG) fabricated by low-pressure chemical vapor deposition over copper foil, and report that the defects of MLG can be controlled by adjusting methane concentration. Moreover, MLG can be changed from metallic to semiconductoring properties by using oxygen plasma treatment, and we investigate the defects evolution of the graphene after exposing to oxygen plasma by Raman spectra. Our results indicate that the amount of defects in graphene can be changed by regulating the methane concentration and oxygen plasma exposure times, but the primary type of defect in MLG is still boundary-like defect. It is valuable for understanding the physics of defects evolution through artificially generated defects, and such defect engineering will greatly open up the future application of the novel material.

  14. Preparation of silicon carbide SiC-based nanopowders by the aerosol-assisted synthesis and the DC thermal plasma synthesis methods

    SciTech Connect

    Czosnek, Cezary; Bućko, Mirosław M.; Janik, Jerzy F.; Olejniczak, Zbigniew; Bystrzejewski, Michał; Łabędź, Olga; Huczko, Andrzej

    2015-03-15

    Highlights: • Make-up of the SiC-based nanopowders is a function of the C:Si:O ratio in precursor. • Two-stage aerosol-assisted synthesis offers conditions close to equilibrium. • DC thermal plasma synthesis yields kinetically controlled SiC products. - Abstract: Nanosized SiC-based powders were prepared from selected liquid-phase organosilicon precursors by the aerosol-assisted synthesis, the DC thermal plasma synthesis, and a combination of the two methods. The two-stage aerosol-assisted synthesis method provides at the end conditions close to thermodynamic equilibrium. The single-stage thermal plasma method is characterized by short particle residence times in the reaction zone, which can lead to kinetically controlled products. The by-products and final nanopowders were characterized by powder XRD, infrared spectroscopy FT-IR, scanning electron microscopy SEM, and {sup 29}Si MAS NMR spectroscopy. BET specific surface areas of the products were determined by standard physical adsorption of nitrogen at 77 K. The major component in all synthesis routes was found to be cubic silicon carbide β-SiC with average crystallite sizes ranging from a few to tens of nanometers. In some cases, it was accompanied by free carbon, elemental silicon or silica nanoparticles. The final mesoporous β-SiC-based nanopowders have a potential as affordable catalyst supports.

  15. Osteoblast behavior on polytetrafluoroethylene modified by long pulse, high frequency oxygen plasma immersion ion implantation.

    PubMed

    Wang, Huaiyu; Kwok, Dixon T K; Wang, Wei; Wu, Zhengwei; Tong, Liping; Zhang, Yumei; Chu, Paul K

    2010-01-01

    Polytetrafluoroethylene (PTFE) is a commonly used medical polymer due to its biological stability and other attractive properties such as high hardness and wear resistance. However, the low surface energy and lack of functional groups to interact with the cellular environment have severely limited its applications in bone or cartilage replacements. Plasma immersion ion implantation (PIII) is a proven effective surface modification technique. However, when conducted on polymeric substrates, conventional PIII experiments typically employ a low pulsing frequency and short pulse duration in order to avoid sample overheating, charging, and plasma sheath extension. In this paper, a long pulse, high frequency O(2) PIII process is described to modify PTFE substrates by implementing a shielded grid in the PIII equipment without these aforementioned adverse effects. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measurements are carried out to reveal the surface effects of PTFE after long pulse, high frequency O(2) PIII and the results are compared to those obtained from conventional short pulse, low frequency O(2) PIII, O(2) plasma immersion, and the untreated control samples. Our results show that less oxygen-containing, rougher, and more hydrophobic surfaces are produced on PTFE after long pulse, high frequency O(2) PIII compared to the other 2 treatments. Cell viability assay, ALP activity test, and real-time PCR analysis are also performed to investigate the osteoblast behavior. It is clear that all 3 surface modification techniques promote osteoblast adhesion and proliferation on the PTFE substrates. Improvements on the ALP, OPN, and ON expression of the seeded osteoblasts are also obvious. However, among these treatments, only long pulse, high frequency O(2) PIII can promote the OCN expression of osteoblasts when the incubation time is 12 days. Our data unequivocally disclose that the long pulse, high frequency O(2) PIII

  16. Combining oxygen plasma treatment with anchorage of cationized gelatin for enhancing cell affinity of poly(lactide-co-glycolide).

    PubMed

    Shen, Hong; Hu, Xixue; Yang, Fei; Bei, Jianzhong; Wang, Shenguo

    2007-10-01

    Surface characteristics greatly influence attachment and growth of cells on biomaterials. Although polylactone-type biodegradable polymers have been widely used as scaffold materials for tissue engineering, lack of cell recognition sites, poor hydrophilicity and low surface energy lead to a bad cell affinity of the polymers, which limit the usage of polymers as scaffolds in tissue engineering. In the present study, surface of poly (L-lactide-co-glycolide) (PLGA) was modified by a method of combining oxygen plasma treatment with anchorage of cationized gelatin. Modification effect of the method was compared with other methods of oxygen plasma treatment, cationized gelatin or gelatin coating and combining oxygen plasma treatment with anchorage of gelatin. The change of surface property was compared by contact angles, surface energy, X-ray photoelectron spectra (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM) measurement. The optimum oxygen pretreatment time determined by surface energy was 10 min when the power was 50 W and the oxygen pressure was 20 Pa. Analysis of the stability of gelatin and cationized gelatin anchored on PLGA by XPS, ATR-FTIR, contact angles and surface energy measurement indicated the cationized gelatin was more stable than gelatin. The result using mouse NIH 3T3 fibroblasts as model cells to evaluate cell affinity in vitro showed the cationized gelatin-anchored PLGA (OCG-PLGA) was more favorable for cell attachment and growth than oxygen plasma treated PLGA (O-PLGA) and gelatin-anchored PLGA (OG-PLGA). Moreover cell affinity of OCG-PLGA could match that of collagen-anchored PLGA (AC-PLGA). So the surface modification method combining oxygen plasma treatment with anchorage of cationized gelatin provides a universally effective way to enhance cell affinity of polylactone-type biodegradable polymers.

  17. Irradiation of silver and agar/silver nanoparticles with argon, oxygen glow discharge plasma, and mercury lamp.

    PubMed

    Ahmad, Mahmoud M; Abdel-Wahab, Essam A; El-Maaref, A A; Rawway, Mohammed; Shaaban, Essam R

    2014-01-01

    The irradiation effect of argon, oxygen glow discharge plasma, and mercury lamp on silver and agar/silver nanoparticle samples is studied. The irradiation time dependence of the synthesized silver and agar/silver nanoparticle absorption spectra and their antibacterial effect are studied and compared. In the agar/silver nanoparticle sample, as the irradiation time of argon glow discharge plasma or mercury lamp increases, the peak intensity and the full width at half maximum, FWHM, of the surface plasmon resonance absorption band is increased, however a decrease of the peak intensity with oxygen glow plasma has been observed. In the silver nanoparticle sample, as the irradiation time of argon, oxygen glow discharge plasma or mercury lamp increases, the peak intensity of the surface plasmon resonance absorption band is increased, however, there is no significant change in the FWHM of the surface plasmon resonance absorption band. The SEM results for both samples showed nanoparticle formation with mean size about 50 nm and 40 nm respectively. Throughout the irradiation time with the argon, oxygen glow discharge plasma or mercury lamp, the antibacterial activity of several kinds of Gram-positive and Gram-negative bacteria has been examined.

  18. Improved reliability predictions in high permittivity dielectric oxide capacitors under high dc electric fields with oxygen vacancy induced electromigration

    NASA Astrophysics Data System (ADS)

    Randall, C. A.; Maier, R.; Qu, W.; Kobayashi, K.; Morita, K.; Mizuno, Y.; Inoue, N.; Oguni, T.

    2013-01-01

    This paper attempts to improve upon the range of applicability and predictability of the empirical highly accelerated lifetime testing (HALT) equation that has been traditionally used to estimate time dependent breakdown strength performance in multilayer ceramic capacitors (MLCC) and integrated thin film capacitor structures. The present and traditional HALT equation shows evidence of being limited in thin dielectric layers under high fields, for example, in high capacitance MLCCs. When the traditional HALT equations are applied to MLCCs with higher operating electric fields, there are often field dependent voltage acceleration factors resulting in ambiguous data analysis. Here, we introduce a physical model to account for a critical ionic space charge accumulation preceded by the ionic hopping or electromigration of oxygen vacancies leading to an ultimate increase in leakage current typical of dielectric resistance degradation. Mean time to failure degradation data on experimental capacitors indicates superior predictions with the new non-linear equation than with the traditional HALT equation to provide more accurate and simpler testing in future components. It is further noted that this approach may be applicable to many capacitive devices that operate under a high bias and can have ionic space charge accumulation at interfaces prior to breakdown.

  19. Charge state distribution studies of pure and oxygen mixed krypton ECR plasma - signature of isotope anomaly and gas mixing effect.

    PubMed

    Kumar, Pravin; Mal, Kedar; Rodrigues, G

    2016-11-01

    We report the charge state distributions of the pure, 25% and 50% oxygen mixed krypton plasma to shed more light on the understanding of the gas mixing and the isotope anomaly [A. G. Drentje, Rev. Sci. Instrum. 63 (1992) 2875 and Y Kawai, D Meyer, A Nadzeyka, U Wolters and K Wiesemann, Plasma Sources Sci. Technol. 10 (2001) 451] in the electron cyclotron resonance (ECR) plasmas. The krypton plasma was produced using a 10 GHz all-permanent-magnet ECR ion source. The intensities of the highly abundant four isotopes, viz. (82) Kr (~11.58%), (83) Kr (~11.49%), (84) Kr (~57%) and (86) Kr (17.3%) up to ~ +14 charge state have been measured by extracting the ions from the plasma and analysing them in the mass and the energy using a large acceptance analyzer-cum-switching dipole magnet. The influence of the oxygen gas mixing on the isotopic krypton ion intensities is clearly evidenced beyond +9 charge state. With and without oxygen mixing, the charge state distribution of the krypton ECR plasma shows the isotope anomaly with unusual trends. The anomaly in the intensities of the isotopes having quite closer natural abundance, viz. (82) Kr, (86) Kr and (83) Kr, (86) Kr is prominent, whereas the intensity ratio of (86) Kr to (84) Kr shows a weak signature of it. The isotope anomaly tends to disappear with increasing oxygen mixing in the plasma. The observed trends in the intensities of the krypton isotopes do not follow the prediction of linear Landau wave damping in the plasma. Copyright © 2016 John Wiley & Sons, Ltd.

  20. Experimental investigation of dielectric barrier discharge plasma actuators driven by repetitive high-voltage nanosecond pulses with dc or low frequency sinusoidal bias

    NASA Astrophysics Data System (ADS)

    Opaits, Dmitry F.; Likhanskii, Alexandre V.; Neretti, Gabriele; Zaidi, Sohail; Shneider, Mikhail N.; Miles, Richard B.; Macheret, Sergey O.

    2008-08-01

    Experimental studies were conducted of a flow induced in an initially quiescent room air by a single asymmetric dielectric barrier discharge driven by voltage waveforms consisting of repetitive nanosecond high-voltage pulses superimposed on dc or alternating sinusoidal or square-wave bias voltage. To characterize the pulses and to optimize their matching to the plasma, a numerical code for short pulse calculations with an arbitrary impedance load was developed. A new approach for nonintrusive diagnostics of plasma actuator induced flows in quiescent gas was proposed, consisting of three elements coupled together: the schlieren technique, burst mode of plasma actuator operation, and two-dimensional numerical fluid modeling. The force and heating rate calculated by a plasma model was used as an input to two-dimensional viscous flow solver to predict the time-dependent dielectric barrier discharge induced flow field. This approach allowed us to restore the entire two-dimensional unsteady plasma induced flow pattern as well as characteristics of the plasma induced force. Both the experiments and computations showed the same vortex flow structures induced by the actuator. Parametric studies of the vortices at different bias voltages, pulse polarities, peak pulse voltages, and pulse repetition rates were conducted experimentally. The significance of charge buildup on the dielectric surface was demonstrated. The charge buildup decreases the effective electric field in the plasma and reduces the plasma actuator performance. The accumulated surface charge can be removed by switching the bias polarity, which leads to a newly proposed voltage waveform consisting of high-voltage nanosecond repetitive pulses superimposed on a high-voltage low frequency sinusoidal voltage. Advantages of the new voltage waveform were demonstrated experimentally.

  1. Cellular-automata model of oxygen plasma impact on porous low-K dielectric

    NASA Astrophysics Data System (ADS)

    Rezvanov, Askar; Matyushkin, Igor V.; Gutshin, Oleg P.; Gornev, Evgeny S.

    2016-12-01

    Cellular-automata model of oxygen plasma influence on the integral properties of porous low-K dielectric is studied. The present work investigates the imitative simulation of this process. In our model we consider one isolated pore, which is simulated by cylinder with length L=200 nm and radius 1 nm ignoring the curvature factor. The simulation was performed for 2 million automata steps that correspond to 2 seconds in the real process time. Extrapolating the data to the longer time shows that more and more •CH3 groups will be replaced by the •OH groups, and over time almost all methyl groups will leave the pore surface (there is not more than 20% of the initial methyl groups amount on the first low-K dielectric 40nm after 2 seconds simulation).

  2. Electron energy distribution functions in low-pressure oxygen plasma columns sustained by propagating surface waves

    SciTech Connect

    Stafford, L.; Margot, J.; Moisan, M.; Khare, R.; Donnelly, V. M.

    2009-01-12

    Electron energy distribution functions (EEDFs) were measured in a 50 mTorr oxygen plasma column sustained by propagating surface waves. Trace-rare-gas-optical-emission spectroscopy was used to derive EEDFs by selecting lines to extract ''electron temperature''(T{sub e}) corresponding to either lower energy electrons that excite high-lying levels through stepwise excitation via metastable states or higher energy electrons that excite emission directly from the ground state. Lower energy T{sub e}'s decreased from 8 to 5.5 eV with distance from the wave launcher, while T{sub e}{approx_equal}6 eV for higher energy electrons and T{sub e}>20 eV for a high-energy tail. Mechanisms for such EEDFs are discussed.

  3. The adhesion of oxygen-plasma treated poly(ethylene) and poly(ethylene terephthlate) films

    SciTech Connect

    Holton, S.L.; Kinloch, A.J.; Watts, J.F.

    1996-12-31

    The effects of low-pressure oxygen-plasma treatment on the surfaces of poly(ethylene) (PE) and poly(ethylene terephthlate) (PET) films and its influence on the adhesion of PE/PET laminates were assessed. The 90{degree} peel test was used to estimate the adhesive fracture energy, G{sub c} for the laminates. XPS, SEM and AFM were used to analyse the treated films and fracture surfaces. Significant improvements in bond strength occurred within very short treatment times (5s at 50W) with the maximum adhesion occurring after 300s. For longer treatment times the bond strengths decrease slightly. G{sub c} values were found to be low when PET was the peel arm. When PE was the peel arm, the G{sub c} values were substantially larger using the current analysis.

  4. Improving the electrical performance of MoS2 by mild oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Nan, Haiyan; Wu, Zhangting; Jiang, Jie; Zafar, Amina; You, Yumeng; Ni, Zhenhua

    2017-04-01

    Two-dimensional (2D) molybdenum disulfide (MoS2) is considered as a promising candidate for electronic and optoelectronic devices. However, structural defects in MoS2 are widely reported and can greatly degrade its electrical and optical properties. In this work, we investigate the structural defects in MoS2 by low temperature photoluminescence (PL) spectroscopy and study their effects on the electrical performance, i.e. carrier mobility. We also adopt the mild oxygen plasma treatment to repair the structural defects and found that the carrier mobility of monolayer MoS2 can be greatly improved. This work would therefore offer a practical route to improve the performance of 2D dichalcogenide-based electrical and optoelectronic devices.

  5. Competitive Low Pressure Oxygen Plasma Interactions with Different= Carbon-Carbon Double Bonds

    NASA Astrophysics Data System (ADS)

    Patiño, P.; Sifontes, A.; Gambús, G.

    1999-10-01

    Recently we have shown advances from reactions of O(^3P) with both, l ong-chain hydrocarbons and refinery residuum. The oxidation products of t he process, a mixture of alcohols, epoxides and carbonyl compounds, might have potential properties as additives in formulating fuels. This work s hows the results of the interactions of an oxygen plasma with double bond s, both olefin and aromatic, in the same compound. The reactions have bee n carried out by making the plasma, created by a high voltage glow discha rge, reach the low vapor pressure surface of liquid 4-phenyl-1-butene. Th is (3 mL) was cooled down to -45 ^oC in a glass reactor, applied power was 24 W, at an oxygen pressure of 20 Pa. Products were analyzed by IR, N MR and mass spectroscopies. Conversions were studied as a function of the reaction time, this ranging from 5 to 120 minutes. At short times the O( ^3P) atoms produced in the discharge only reacted with the alkene fra ction of the hydrocarbon, 4-phenyl-1,2-epoxibutane (52%) and 4-phenyl-bu tanal (48%) being the products. Reactions on the benzene ring were obser ved from about 30 minutes on, the corresponding phenols having being prod uced at ratios ortho:para:meta :: 4:1:0.7. At 120 minutes, the ol efin have been completely oxidized and a low fraction of the non-equivale nt two methylene groups have reacted to produce alcohols and ketones.

  6. Effect of Low-Pressure Nitrogen DC Plasma Treatment on the Surface Properties of Biaxially Oriented Polypropylene, Poly (Methyl Methacrylate) and Polyvinyl Chloride Films

    NASA Astrophysics Data System (ADS)

    S. Hamideh, Mortazavi; Mahmood, Ghoranneviss; Soheil, Pilehvar; Sina, Esmaeili; Shamim, Zargham; S. Ebrahim, Hashemi; Hamzeh, Jodat

    2013-04-01

    In this study, commercial biaxially oriented polypropylene (BOPP), polyvinyl chloride (PVC) and poly (methyl methacrylate) (PMMA) films were treated with nitrogen plasma over different exposure times in a Pyrex tube surrounded by a DC variable magnetic field. The chemical changes that appeared on the surface of the samples were investigated using Fourier transform infrared (FT-IR) spectroscopy and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy after treatment for 2 min, 4 min and 6 min in a nitrogen plasma chamber. Effects of the plasma treatment on the surface topographies and contact angles of the untreated and plasma treated films were also analyzed by atomic force microscopy (AFM) and a contact angle measuring system. The results show that the plasma treated films become more hydrophilic with an enhanced wettability due to the formation of some new polar groups on the surface of the treated films. Moreover, at higher exposure times, the total surface energy in all treated films increased while a reduction in contact angle occurred. The behavior of surface roughness in each sample was completely different at higher exposure times.

  7. Evaluation of fatty acid oxidation by reactive oxygen species induced in liquids using atmospheric-pressure nonthermal plasma jets

    NASA Astrophysics Data System (ADS)

    Tani, Atsushi; Fukui, Satoshi; Ikawa, Satoshi; Kitano, Katsuhisa

    2015-10-01

    We investigated fatty acid oxidation by atmospheric-pressure nonthermal helium plasma using linoleic acid, an unsaturated fatty acid, together with evaluating active species induced in liquids. If the ambient gas contains oxygen, direct plasma such as plasma jets coming into contact with the liquid surface supplies various active species, such as singlet oxygen, ozone, and superoxide anion radicals, to the liquid. The direct plasma easily oxidizes linoleic acid, indicating that fatty acid oxidation will occur in the direct plasma. In contrast, afterglow flow, where the plasma is terminated in a glass tube and does not touch the surface of the liquid sample, supplies mainly superoxide anion radicals. The fact that there was no clear observation of linoleic acid oxidation using the afterglow reveals that it may not affect lipids, even in an atmosphere containing oxygen. The afterglow flow can potentially be used for the sterilization of aqueous solutions using the reduced pH method, in medical and dental applications, because it provides bactericidal activity in the aqueous solution despite containing a smaller amount of active species.

  8. Tuning the electrical property via defect engineering of single layer MoS2 by oxygen plasma

    NASA Astrophysics Data System (ADS)

    Islam, Muhammad R.; Kang, Narae; Bhanu, Udai; Paudel, Hari P.; Erementchouk, Mikhail; Tetard, Laurene; Leuenberger, Michael N.; Khondaker, Saiful I.

    2014-08-01

    We have demonstrated that the electrical property of single-layer molybdenum disulfide (MoS2) can be significantly tuned from the semiconducting to the insulating regime via controlled exposure to oxygen plasma. The mobility, on-current and resistance of single-layer MoS2 devices were varied by up to four orders of magnitude by controlling the plasma exposure time. Raman spectroscopy, X-ray photoelectron spectroscopy and density functional theory studies suggest that the significant variation of electronic properties is caused by the creation of insulating MoO3-rich disordered domains in the MoS2 sheet upon oxygen plasma exposure, leading to an exponential variation of resistance and mobility as a function of plasma exposure time. The resistance variation calculated using an effective medium model is in excellent agreement with the measurements. The simple approach described here can be used for the fabrication of tunable two-dimensional nanodevices based on MoS2 and other transition metal dichalcogenides.We have demonstrated that the electrical property of single-layer molybdenum disulfide (MoS2) can be significantly tuned from the semiconducting to the insulating regime via controlled exposure to oxygen plasma. The mobility, on-current and resistance of single-layer MoS2 devices were varied by up to four orders of magnitude by controlling the plasma exposure time. Raman spectroscopy, X-ray photoelectron spectroscopy and density functional theory studies suggest that the significant variation of electronic properties is caused by the creation of insulating MoO3-rich disordered domains in the MoS2 sheet upon oxygen plasma exposure, leading to an exponential variation of resistance and mobility as a function of plasma exposure time. The resistance variation calculated using an effective medium model is in excellent agreement with the measurements. The simple approach described here can be used for the fabrication of tunable two-dimensional nanodevices based on MoS2

  9. The effect of oxygen flow rate and radio frequency plasma power on cubic ZnMgO ultraviolet sensors grown by plasma-enhanced molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Casey Boutwell, R.; Wei, Ming; Schoenfeld, Winston V.

    2013-07-01

    Cubic Zn1-xMgxO thin films were produced by Plasma-Enhanced Molecular Beam Epitaxy. Oxygen flow rate and applied Radio-Frequency (RF) plasma power were varied to investigate the impact on film growth and optoelectronic device performance. Solar-blind and visible-blind detectors were fabricated with metal-semiconductor-metal interdigitated Ni/Mg/Au contacts and responsivity is compared under different growth conditions. Increasing oxygen flow rate and RF plasma power increased Zn incorporation in the film, which leads to phase segregation at relatively high Zn/Mg ratio. Responsivity as high as 61 A/W was measured in phase-segregated ZnMgO visible-blind detectors.

  10. Analytical study of whistler mode waves in presence of parallel DC electric field for relativistic plasma in the magnetosphere of Uranus

    NASA Astrophysics Data System (ADS)

    Pandey, R. S.; Kaur, Rajbir

    2016-10-01

    In present paper, field aligned whistler mode waves are analyzed, in the presence of DC field in background plasma having relativistic distribution function in the magnetosphere of Uranus. The work has been examined for relativistic Maxwellian and loss-cone distribution function. In both the cases, we have studied the effect of various plasma parameters on the growth rate of waves by using the method of characteristics and discussed using data provided by Voyager 2. Growth rate has increased by increasing the magnitude of electric field, temperature anisotropy, energy density and number density of particles for Maxwellian and loss-cone background. However, when relativistic factor (λ =√{ 1 -v2 /c2 }) increases, growth rate decreases. The significant increase in real frequency of whistler waves can be observed. The results can be used for comparative study of planetary magnetospheres. The derivation can also be adapted to study various other instabilities in magnetosphere of Uranus.

  11. Solid-Sampling Electrothermal Vaporization Inductively Coupled Plasma Optical Emission Spectrometry for Direct Determination of Total Oxygen in Coal.

    PubMed

    Vogt, Thomas; Bauer, Daniela; Nennstiel, David; Otto, Matthias

    2015-10-20

    A new analytical method for direct determination of total oxygen contents in eight coal samples of the Argonne Premium Coal (APC) series and in the NIST SRM 1632d is presented. The development of a suitable calibration procedure, optimization of measurement conditions, and the application of a tailored data processing for handling of plasma effects and high blanks enable the quantification of oxygen simultaneously with other trace, minor, or major elements in whole coal samples by means of electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP OES). For comparison, the oxygen contents were determined by a direct oxygen analyzer. The obtained oxygen values of the APC and the reference material NIST SRM 1632d were compared to data in the literature. The precision of the ETV-ICP OES was within ±3.5%, and the recovery better than 92%. With this good accuracy, the developed direct solid sampling method ETV-ICP OES is well suited for the fast determination of oxygen in coals, varying in rank from lignite to semianthracite, in a content range of about 100 ppm up to 27% using 1.5 mg sample weight. This direct analysis method represents an accurate, advantageous alternative to currently used methods for estimation of total oxygen contents in coals.

  12. Rapid assessment of singlet oxygen-induced plasma lipid oxidation and its inhibition by antioxidants with diphenyl-1-pyrenylphosphine (DPPP).

    PubMed

    Morita, Mayuko; Naito, Yuji; Yoshikawa, Toshikazu; Niki, Etsuo

    2016-01-01

    Recent studies suggesting the involvement of singlet oxygen in the pathogenesis of multiple diseases have attracted renewed attention to lipid oxidation mediated by singlet oxygen. Although the rate constants for singlet oxygen quenching by antioxidants have been measured extensively, the inhibition of lipid oxidation mediated by singlet oxygen has received relatively less attention, partly because a convenient method for measuring the rate of lipid oxidation is not available. The objective of this study was to develop a convenient method to measure plasma lipid oxidation mediated by singlet oxygen which may be applied to a rapid assessment of the antioxidant capacity to inhibit this oxidation using a conventional microplate reader. Singlet oxygen was produced from naphthalene endoperoxide, and lipid hydroperoxide production was followed by using diphenyl-1-pyrenylphosphine (DPPP). Non-fluorescent DPPP reacts stoichiometrically with lipid hydroperoxides to give highly fluorescent DPPP oxide. It was found that plasma oxidation by singlet oxygen increased the fluorescence intensity of DPPP oxide, which was suppressed by antioxidants. Fucoxanthin suppressed the oxidation more efficiently than β-carotene and α-tocopherol, while ascorbic acid and Trolox were not effective. The present method may be useful for monitoring lipid oxidation and also for rapid screening of the capacity of dietary antioxidants and natural products to inhibit lipid oxidation in a biologically relevant system.

  13. Cell attachment and biocompatibility of polytetrafluoroethylene (PTFE) treated with glow-discharge plasma of mixed ammonia and oxygen.

    PubMed

    Chen, Meng; Zamora, Paul O; Som, Prantika; Peña, Louis A; Osaki, Shigemasa

    2003-01-01

    The plasma generated from a gas mixture of NH3 plus O2 (NH3 + O2) has been used to impart unique chemical and biological characteristics to polytetrafluoroethylene (PTFE). PTFE treated with NH3 + O2 plasma was physiochemically distinct from surfaces treated with plasma of either NH3 or O2 alone, as determined by electron spectroscopy for chemical analysis (ESCA). The contact angle analysis revealed that the PTFE surfaces became less hydrophobic after plasma treatments. ESCA results indicate the presence of oxygen-containing groups and nitrogen-containing groups at the plasma-treated surfaces. PTFE treated with NH3 + O2 plasma resisted the attachment of platelets and leukocytes in a manner similar to untreated PTFE; however, the attachment of bovine aorta endothelial cells was substantially increased. Once attached, these cells grew to confluency. The increased endothelial cell attachment was higher than that observed following plasma treatment with each gas used separately, which could be attributed to the considerable amount of CF(OR)2-CF2 formed on the NH3 + O2 plasma-treated PTFE surface. At 14 days after subcutaneous implantation in rats, the PTFE wafers treated with NH3 + O2 plasma demonstrated less encapsulation and lower levels of inflammatory cells compared to controls. Collectively, the results suggest that NH3 + O2 plasma treatment imparts a unique character to PTFE and could be useful in certain in vivo applications.

  14. The surface chemistry resulting from low-pressure plasma treatment of polystyrene: The effect of residual vessel bound oxygen

    NASA Astrophysics Data System (ADS)

    Dhayal, Marshal; Alexander, Morgan R.; Bradley, James W.

    2006-09-01

    The surface chemistry of plasma treated polystyrene samples has been studied in a specially designed low-pressure argon discharge system incorporating in situ XPS analysis. By using an electrostatic grid biasing technique, the plasma source can also be used in a mode preventing ion interactions with the sample. The system, which utilizes a vacuum transfer chamber between plasma and XPS analysis has allowed us to differentiate between the level of oxygen incorporated at the polystyrene surface from residual gas during treatment and that from the exposure of the treated sample to the laboratory atmosphere. Using typical base pressures of about 5 × 10 -3 Pa (4 × 10 -5 Torr) the XPS results show that significant oxygen surface incorporation resulted from oxygen containing species in the plasma itself (i.e. water vapour with 2 × 10 -3 Pa partial pressure). The surface concentration of O was measured at 7.6 at.%. Subsequent atmospheric exposure of the treated samples resulted in only a small increase (of 0.6 at.%) in oxygen incorporation in the form of acid anhydride functionalities. XPS measurements of PS samples exposed to plasmas with no ion-surface component (i.e. exposure from VUV, UV and excited neutral species only) showed no appreciable change in oxygen incorporation compared to those with low-energy ion bombardment from the plasma (<20 eV). Given the energetics of the remaining bombarding species, it indicates that VUV radiation may be chiefly responsible for the production of free radical sites in this discharge regime.

  15. Mitigation of electron attachment to oxygen in high pressure air plasmas by vibrational excitation

    NASA Astrophysics Data System (ADS)

    Frederickson, K.; Lee, W.; Palm, P.; Adamovich, I. V.; Rich, J. W.; Lempert, W. R.

    2007-05-01

    A series of time resolved microwave attenuation measurements are performed of the electron number density of an electron beam generated, CO laser excited nonequilibrium O2/N2 plasma. Resonant absorption of infrared radiation from the CO laser produces the nonequilibrium state, in which the heavy species vibrational modes are disproportionately excited, compared to the rotational and translational modes (Tvib≈2000-3000K vs TR /T≈300K). It is shown that this results in an increase in the plasma free electron lifetime by two orders of magnitude compared to the unexcited cold gas, an effect which is ascribed to complete mitigation of rapid three-body electron attachment to molecular oxygen. A series of heavy species filtered pure rotational Raman scattering measurements are also presented, which exhibit minimal temperature change (+50K), indicating that the observed lifetime increase cannot be due to heavy-species thermal effects. Finally, computational modeling results infer an increase in the rate of O2- detachment by four to five orders of magnitude, compared to the equilibrium value.

  16. Anisotropic etching of amorphous perfluoropolymer films in oxygen-based inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Ono, Takao; Akagi, Takanori; Ichiki, Takanori

    2009-01-01

    An amorphous perfluoropolymer, "Cytop™" (Asahi Glass Co., Ltd.), is a preferable material for the fabrication of micro total analysis system devices because of its superior optical transparency over a wide wavelength range and low refractive index of 1.34, which is almost the same as that of water, as well as excellent chemical stability. To establish the precise microfabrication technology for this unique resin, the dry etching of the amorphous perfluoropolymer in Ar/O2 low-pressure inductively coupled plasma has been studied. A relatively high etch rate of approximately 6.3 μm/min at maximum and highly anisotropic etched features was attained. Plasma measurements by a single Langmuir probe technique and actinometry revealed that etching is dominated by ion-assisted surface desorption above a 10% O2 mixing ratio, whereas the supply of active oxygen species is the rate-limiting process below 10%. Moreover, angled x-ray photoelectron spectroscopy measurements of an etched trench pattern revealed that a high anisotropy is attributed to the formation of a carbon-rich sidewall protection layer.

  17. On the E-H transition in inductively coupled radio frequency oxygen plasmas: I. Density and temperature of electrons, ground state and singlet metastable molecular oxygen

    NASA Astrophysics Data System (ADS)

    Wegner, Th; Küllig, C.; Meichsner, J.

    2017-02-01

    In this series of two papers, the E-H transition in a planar inductively coupled radio frequency discharge (13.56 MHz) in pure oxygen is studied using comprehensive plasma diagnostic methods. The electron density serves as the main plasma parameter to distinguish between the operation modes. The (effective) electron temperature, which is calculated from the electron energy distribution function and the difference between the floating and plasma potential, halves during the E-H transition. Furthermore, the pressure dependency of the RF sheath extension in the E-mode implies a collisional RF sheath for the considered total gas pressures. The gas temperature increases with the electron density during the E-H transition and doubles in the H-mode compared to the E-mode, whereas the molecular ground state density halves at the given total gas pressure. Moreover, the singlet molecular metastable density reaches 2% in the E-mode and 4% in the H-mode of the molecular ground state density. These measured plasma parameters can be used as input parameters for global rate equation calculations to analyze several elementary processes. Here, the ionization rate for the molecular oxygen ions is exemplarily determined and reveals, together with the optical excitation rate patterns, a change in electronegativity during the mode transition.

  18. REACTIVE OXYGEN SPECIES IN WHOLE BLOOD, BLOOD PLASMA AND BREAST MILK: VALIDATION OF A POTENTIAL MARKER OF EXPOSURE AND EFFECT

    EPA Science Inventory

    Reactive oxygen species (ROS) are recognized to contribute to the pathobiology of many diseases. We have applied a simple chemiluminescent (CL) probe to detect ROS in various biological fluids (plasma, whole blood, urine and breast milk) in an environmental arsenic drinking wate...

  19. Surface Evaluation by X-Ray Photoelectron Spectroscopy of High Performance Polyimide Foams After Exposure to Oxygen Plasma

    NASA Technical Reports Server (NTRS)

    Melendez, Orlando; Hampton, Michael D.; Williams, Martha K.; Brown, Sylvia F.; Nelson, Gordon L.; Weiser, Erik S.

    2002-01-01

    Aromatic polyimides have been attractive in the aerospace and electronics industries for applications such as cryogenic insulation, flame retardant panels and structural subcomponents. Newer to the arena of polyimides is the synthesis of polyimide foams and their applications. In the present work, three different, closely related, polyimide foams developed by NASA Langley Research Center (LaRC) are studied by X-ray Photoelectron Spectroscopy (XPS) after exposure to radio frequency generated Oxygen Plasma. Although polyimide films exposure to atomic oxygen and plasma have been studied previously and reported, the data relate to films and not foams. Foams have much more surface area and thus present new information to be explored. Understanding degradation mechanisms and properties versus structure, foam versus solid is of interest and fundamental to the application and protection of foams exposed to atomic oxygen in Low Earth Orbit (LEO).

  20. Transparent ultra water-repellent poly(ethylene terephthalate) substrates fabricated by oxygen plasma treatment and subsequent hydrophobic coating

    NASA Astrophysics Data System (ADS)

    Teshima, Katsuya; Sugimura, Hiroyuki; Inoue, Yasushi; Takai, Osamu; Takano, Atsushi

    2005-05-01

    Wettability of solid surfaces with water is well-known to be governed by chemical properties and nanotextures of the surfaces. A proper nanotexture of surfaces enhances their hydrophobicity. In this study, a novel method consisting of two dry process techniques, that is, nanotexturing by an oxygen plasma treatment and subsequent hydrophobic coating by means of low temperature chemical vapor deposition or plasma-enhanced chemical vapor deposition, was employed to form ultra water-repellent polymer sheets. A nanotexture was formed on a poly(ethylene terephthalate) substrate surface via selective oxygen plasma etching. This surface nanotexture remained after the hydrophobic coatings using organosilane precursors. The surface-modified substrate was transparent and ultra water-repellent, showing a water contact angle greater than 150°.

  1. Biodegradability of oxygen-plasma treated cellulose textile functionalized with ZnO nanoparticles as antibacterial treatment

    NASA Astrophysics Data System (ADS)

    Primc, Gregor; Tomšič, Brigita; Vesel, Alenka; Mozetič, Miran; Ercegović Ražić, Sanja; Gorjanc, Marija

    2016-08-01

    Samples of bleached cellulose fabric were treated with weakly ionized highly dissociated oxygen plasma in order to improve the binding of ZnO nanoparticles, antibacterial properties and biodegradability. Low specific discharge power of about 24 W l-1 was applied in order to minimize thermal effects following plasma treatment. Optical emission spectroscopy revealed weak etching of the fabric while x-ray photoelectron spectroscopy showed formation of oxygen-rich functional groups. Scanning electron microscopy revealed an improved uptake of ZnO nanoparticles and the standard transfer method highlighted excellent antimicrobial effects for Staphylococcus aureus and Escherichia coli. The biodegradability of all samples was determined using the standard ISO test and revealed excellent results for plasma-treated samples even in cases when they were functionalized using ZnO nanoparticles.

  2. Effects of hyperbaric oxygen therapy combined with platelet-rich plasma on diabetic wounds: an experimental rat model

    PubMed Central

    Kahaman, Cüneyt; Kahaman, Nail; Yalçınkaya, Ulviye; Akçılar, Aydin; Akgül, Engin; Vural, Ahmet Hakan

    2016-01-01

    Introduction Hyperbaric oxygen and platelet-rich plasma are used in the treatment of diabetic wounds. The aim of this study is to evaluate the effects of hyperbaric oxygen therapy and autologous platelet concentrates in healing diabetic wounds. Material and methods Thirty-six female Wistar albino rats were used in this study. Diabetes mellitus was induced chemically with an intraperitoneal injection of streptozotocin. The rats were divided into a control group, a hyperbaric oxygen group, a platelet-rich plasma group, and a combined therapy group. Platelet-rich plasma was applied just after the creation of the wound; hyperbaric oxygen treatment was carried out daily over 7 days. Wound healing was evaluated according to four parameters: ulcerations, epidermal thickness, density of dermal collagen fibers, and proliferation of dermal blood vessels. Results The number of active ulcers in the combined therapy group was fewer than in the control group (p = 0.039), and the wound area was greatest in controls (p < 0.001). The epidermal thickness in platelet-rich plasma and combined therapy groups was non-significantly greater than in the control group (p = 0.097 and p = 0.074, respectively). The amount of fibrous collagen in these two groups was greater than in the control group (p = 0.002). Conclusions Combined hyperbaric oxygen and platelet-rich plasma therapy was found to be successful in diabetic wound healing. The combination therapy had no additive effect in terms of angiogenesis and the development of new collagen fibers. PMID:27904531

  3. Cold atmospheric-pressure air plasma treatment of C6 glioma cells: effects of reactive oxygen species in the medium produced by the plasma on cell death

    NASA Astrophysics Data System (ADS)

    Yuyang, Wang; Cheng, Cheng; Peng, Gao; Shaopeng, Li; Jie, Shen; Yan, Lan; Yongqiang, Yu; Paul, K. Chu

    2017-02-01

    An atmospheric-pressure air plasma is employed to treat C6 glioma cells in vitro. To elucidate on the mechanism causing cell death and role of reactive species (RS) in the medium produced by the plasma, the concentration of the long-lived RS such as hydrogen peroxide, nitrate, and ozone in the plasma-treated liquid (phosphate-buffered saline solution) is measured. When vitamin C is added to the medium as a ROS quencher, the viability of C6 glioma cells after the plasma treatment is different from that without vitamin C. The results demonstrate that reactive oxygen species (ROS) such as H2O2, and O3 constitute the main factors for inactivation of C6 glioma cells and the reactive nitrogen species (RNS) may only play an auxiliary role in cell death.

  4. Role of DC Electric Fields and Wave Heating in Cavity Profiles of Depleted Density and Transverse Ion Acceleration in Laboratory and Space Plasmas

    NASA Astrophysics Data System (ADS)

    Koepke, M. E.; Reynolds, E. W.; Knudsen, D. J.

    2007-05-01

    Laboratory experiments on the WVU Q Machine, test-particle simulations, and Monte Carlo simulations are shown to provide evidence for explaining the inhomogeneity in both the plasma-density profile and the ion- temperature profile associated with cylindrically symmetric lower-hybrid cavities observed by the GEODESIC sounding rocket, the OEDIPUS-C sounding rocket, and the Freja satellite. Two potential contributions to the inhomogeneous profiles are identified. Both mechanisms (one dc and the other ac) rely on finite values of the Larmor radius and can result in nonlocal effects that deplete ion density within the cavity and enhance ion density immediately outside the cavity to form ion-gyroradius-scale shoulders encircling the cavity perimeter. In the absence of waves, a cylindrically symmetric, radial, DC electric field can be responsible for a polarization shift that produces such inhomogeneity in the density profile [1]. In the presence of waves, wave-induced transverse ion acceleration occurring within the cavity can produce such inhomogeneity in the density profile [2]. In combination, the two effects are shown to be comparable, necessitating an interpretation that includes both mechanisms for quantitative agreement. For the lab data, laser-induced fluorescence techniques provide high resolution in coordinate space and velocity space. [1] Reynolds et al., Inhomogeneity scale lengths in a magnetized, low temperature, collisionless, Q-machine plasma column containing perpendicular-velocity shear, Phys. Plasmas 13, 092106 (2006). [2] Knudsen et al., Lower-hybrid cavity density depletions as a result of transverse ion acceleration localized on the gyroradius scale, J. Geophys. Res. 109, A04212 (2004). This research is supported by NSF.

  5. Study of optical properties of asymmetric bipolar pulse DC magnetron sputtered Ta{sub 2}O{sub 5} thin film as a function of oxygen content in deposition ambient

    SciTech Connect

    Haque, S. Maidul Shinde, D. D. Misal, J. S.; Bhattacharyya, D.; Sahoo, N. K.

    2014-04-24

    Tantalum penta-oxide thin films have been deposited by reactive sputtering technique using asymmetric bipolar pulsed DC source at various oxygen percentage viz. 0 to 50 %. The optical properties of the films have been studied by spectroscopic ellipsometry measurements. It has been observed that compact films with low void fraction, high refractive index and band gap can be obtained by the above technique with oxygen percentage in the range of 30–40%. The films deposited with zero or very low oxygen content have high deposition rate and yield metal rich films with large voids, defects, low band gap and high refractive index. Similarly films deposited with >40% oxygen content again contain voids and defects due to the presence of large amount of gas molecules in the sputtering ambient.

  6. Plasma osmolality and oxygen consumption of perch Perca fluviatilis in response to different salinities and temperatures.

    PubMed

    Christensen, E A F; Svendsen, M B S; Steffensen, J F

    2017-03-01

    The present study determined the blood plasma osmolality and oxygen consumption of the perch Perca fluviatilis at different salinities (0, 10 and 15) and temperatures (5, 10 and 20° C). Blood plasma osmolality increased with salinity at all temperatures. Standard metabolic rate (SMR) increased with salinity at 10 and 20° C. Maximum metabolic rate (MMR) and aerobic scope was lowest at salinity of 15 at 5° C, yet at 20° C, they were lowest at a salinity of 0. A cost of osmoregulation (SMR at a salinity of 0 and 15 compared with SMR at a salinity of 10) could only be detected at a salinity of 15 at 20° C, where it was 28%. The results show that P. fluviatilis have capacity to osmoregulate in hyper-osmotic environments. This contradicts previous studies and indicates intraspecific variability in osmoregulatory capabilities among P. fluviatilis populations or habitat origins. An apparent cost of osmoregulation (28%) at a salinity of 15 at 20° C indicates that the cost of osmoregulation in P. fluviatilis increases with temperature under hyperosmotic conditions and a power analysis showed that the cost of osmoregulation could be lower than 12·5% under other environmental conditions. The effect of salinity on MMR is possibly due to a reduction in gill permeability, initiated to reduce osmotic stress. An interaction between salinity and temperature on aerobic scope shows that high salinity habitats are energetically beneficial during warm periods (summer), whereas low salinity habitats are energetically beneficial during cold periods (winter). It is suggested, therefore, that the seasonal migrations of P. fluviatilis between brackish and fresh water is to select an environment that is optimal for metabolism and aerobic scope.

  7. Experiments with Plasmas Produced by Potassium-Seeded Cyanogen Oxygen Flames for Study of Radio Transmission at Simulated Reentry Vehicle Plasma Conditions

    NASA Technical Reports Server (NTRS)

    Huber, Paul W.; Gooderum, Paul B.

    1961-01-01

    A method for the chemical production of an ionized gas stream for application to radio transmission studies is described. Involved is the combustion of gaseous cyanogen and oxygen with the addition of vaporized potassium in some cases to further increase the ionization. Experiments are described in which a 3-inch-diameter subsonic free jet at atmospheric pressure is used, and the results are presented. The plasma obtained by using this method is sufficient to simulate plasma conditions expected for reentering hypersonic vehicles. The unseeded plasma stream temperature is indicated to be about 4,200 K, with the degree of ionization indicated to be that expected from thermal equilibrium considerations. Measurements of radio-signal loss due to the unseeded flame plasma are presented for microwaves of 8 to 20 kmc transmitted through the stream and for a dipole transmitting model of 219.5 mc immersed in the stream. Favorable comparison of these results with the simple plane-wave signal-attenuation theory was obtained. In the case of a 9.4-kmc microwave signal of 30-kw peak power, the preliminary indication is that the plasma characteristics were not changed due to this strong signal. Comparison of a simplified concept of radio-signal attenuation due to plasmas is made with some hypersonic reentry vehicle signal-loss data. Other areas of plasma research using this method for the transmission problem are indicated.

  8. Effect of oxygen plasma treatment on the electrical characteristics of Pt/n-type Si Schottky diodes

    NASA Astrophysics Data System (ADS)

    Janardhanam, V.; Jyothi, I.; Yuk, Shim-Hoon; Choi, Chel-Jong; Lee, Sung-Nam; Reddy, V. Rajagopal

    2016-10-01

    The electrical properties of Pt/n-type Si Schottky diodes fabricated from n-type Si wafers subjected to an oxygen (O2) plasma treatment were investigated as a function of the power of the O2 plasma. The Pt/n-type Si Schottky diode with an O2 plasma treatment at a power of 100 W showed better rectifying characteristics with increasing barrier height and decreasing ideality factor compared to the conventional Pt/n-type Si Schottky diodes. This could be attributed to an improvement in the interface homogeneity associated with damage-free surface smoothing driven by the O2 plasma treatment at a power of 100 W. On the other hand, with increasing power of the O2 plasma for powers above 150 W, the barrier height decreased and the leakage current increased, indicating degradation of the device performance. The degradation in the rectifying properties after the O2 plasma treatment at a higher plasma power in excess of 150 W could be associated with increases in the series resistance and the interface state density caused by plasma-induced damage to the Si surface.

  9. Effect of an oxygen plasma on the physical and chemical properties of several fluids for the liquid droplet radiator

    NASA Technical Reports Server (NTRS)

    Gulino, D. A.; Coles, C. E.

    1986-01-01

    The Liquid Droplet Radiator is one of several radiator systems currently under investigation by NASA Lewis Research Center. It involves the direct exposure of the radiator working fluid to the space environment. An area of concern is the potential harmful effects of the low-Earth-orbit atomic oxygen environment on the radiator working fluid. To address this issue, seven candidate fluids were exposed to an oxygen plasma environment in a laboratory plasma asher. The fluids studied included Dow Corning 705 Diffusion Pump Fluid, polymethylphenylsiloxane and polydimethlsiloxane, both of which are experimental fluids made by Dow Corning, Fomblin Z25, made by Montedison, and three fluids from the Krytox family of fluids, Krytox 143AB, 1502, and 16256, which are made by DuPont. The fluids were characterized by noting changes in visual appearance, physical state, mass, and infrared spectra. Of the fluids tested, the Fomblin and the three Krytoxes were the least affected by the oxygen plasma. The only effect noted was a change in mass, which was most likely due to an oxygen-catalyzed deploymerization of the fluid molecule.

  10. Effect of an oxygen plasma on the physical and chemical properties of several fluids for the Liquid Droplet Radiator

    NASA Technical Reports Server (NTRS)

    Gulino, Daniel A.; Coles, Carolyn E.

    1987-01-01

    The Liquid Droplet Radiator is one of several radiator systems currently under investigation by NASA Lewis Research Center. It involves the direct exposure of the radiator working fluid to the space environment. An area of concern is the potential harmful effects of the low-Earth-orbit atomic oxygen environment on the radiator working fluid. To address this issue, seven candidate fluids were exposed to an oxygen plasma environment in a laboratory plasma asher. The fluids studied included Dow Corning 705 Diffusion Pump Fluid, polymethylphenylsiloxane and polydimethylsiloxane, both of which are experimental fluids made by Dow Corning, Fomblin Z25, made by Montedison, and three fluids from the Krytox family of fluids, Krytox 143AB, 1502, and 16256, which are made by DuPont. The fluids were characterized by noting changes in visual appearance, physical state, mass, and infrared spectra. Of the fluids tested, the Fomblin and the three Krytoxes were the least affected by the oxygen plasma. The only effect noted was a change in mass, which was most likely due to an oxygen-catalyzed depolymerization of the fluid molecule.

  11. Investigation of Atomic Oxygen Erosion of Polyimide Kapton H Exposed to a Plasma Asher Environment

    NASA Technical Reports Server (NTRS)

    Snyder, Aaron

    1999-01-01

    Experimental results are presented on the erosion characteristics of the polyimide Kapton H, which serves as a blanket material in solar arrays. This polymer has a number of characteristics that make it a suitable choice for both terrestrial and space applications. In this paper attention is focused on the durability of protected Kapton when exposed to atomic oxygen (AO) in a plasma asher. A strip of 0.025-mm thick Kapton film, coated on both sides with SiO2, was studied during a 1306 hour exposure. The erosion, located at defect sites in the protective coating and measured optically, is described in terms of volume loss as a function of AO fluence. Three simple geometric profiles are used to generate a useful array of cavity shapes to model erosion evolution. These models connect the volume erosion rate to the observed lateral expansion of the developing cavities via their diameters, measured adviacent to the upper and lower protective film, and fitted by least-squares regression to simple power law functions of fluence. The rationale for the choice of models is discussed. It was found that lateral growth in cavity size evolves less than linearly with fluence.

  12. HEMORHEOLOGICAL IMPLICATIONS OF PERFLUOROCARBON BASED OXYGEN CARRIER INTERACTION WITH COLLOID PLASMA EXPANDERS AND BLOOD

    PubMed Central

    Vásquez, Diana M.; Ortiz, Daniel; Alvarez, Oscar A.; Briceño, Juan C.; Cabrales, Pedro

    2013-01-01

    Perfluorocarbon (PFC) emulsion based oxygen carriers lack colloid osmotic pressure (COP) and must be administered with colloid-based plasma expanders (PEs). Although PFC emulsions have been widely studied, there is limited information about PFC emulsion interaction with PEs and blood. Their interaction forms aggregates due to electrostatic and rheological phenomena, and change blood rheology and blood flow. This study analyzes the effects of the interaction between PFC emulsions with blood in the presence of clinically-used PEs. The rheological behavior of the mixtures was analyzed in parallel with in vivo analysis of blood flow in microvessels using intravital microscopy when administered in a clinically relevant scenario. The interaction between the PFC emulsion and PE with blood produced PFC droplets and red blood cell (RBCs) aggregation, and increased blood viscosity. The PFC droplets formed aggregates when mixed with PEs containing electrolytes, and the aggregation increased with the electrolyte concentration. Mixtures of PFC with PEs that produced PFC aggregates also induced RCBs aggregation when mixed with blood, increasing blood viscosity at low shear rates. The more viscous suspension at low shear rates produced a blunted blood flow velocity profile in vivo relative to non-aggregating mixtures of PFC and PEs. For the PEs evaluated, albumin produced minimal to undetectable aggregation. PFC and PEs interaction with blood can affect sections of the microcirculation with low shear rate (e.g. arterioles, venules, and pulmonary circulation) because aggregates could cause capillary occlusion, decrease perfusion, pulmonary emboli, or focal ischemia. PMID:23606592

  13. Oxygen bomb combustion of biological samples for inductively coupled plasma optical emission spectrometry

    NASA Astrophysics Data System (ADS)

    Souza, Gilberto B.; Carrilho, Elma Neide V. M.; Oliveira, Camila V.; Nogueira, Ana Rita A.; Nóbrega, Joaquim A.

    2002-12-01

    A rapid sample preparation method is proposed for decomposition of milk powder, corn bran, bovine and fish tissues, containing certified contents of the analytes. The procedure involves sample combustion in a commercial stainless steel oxygen bomb operating at 25 bar. Most of the samples were decomposed within 5 min. Diluted nitric acid or water-soluble tertiary amines 10% v/v were used as absorption solutions. Calcium, Cu, K, Mg, Na, P, S and Zn were recovered with the bomb washings and determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Ethanol mixed with paraffin was used as a combustion aid to allow complete combustion. A cooling step prior releasing of the bomb valve was employed to increase the efficiency of sample combustion. Iodine was also determined in milk samples spiked with potassium iodide to evaluate the volatilization and collection of iodine in amine CFA-C medium and the feasibility of its determination by ICP-OES with axial view configuration. Most of the element recoveries in the samples were between 91 and 105% and the certified and found contents exhibited a fair agreement at a 95% confidence level.

  14. Metal-insulator transition at lanthanum aluminate-strontium titanate interface induced by oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Dai, Weitao; Cen, Cheng

    The formation of two-dimensional electron gas (2DEG) at lanthanum aluminate (LAO)-strontium titanate (STO) interface, as well as the 2DEG's unique characters in metal-insulator transition, have evoked widespread interest. Highly insulating interfaces are obtained for the structures with LAO thickness below 3 unit cell (uc) and abrupt transition from an insulating to conducting interface was observed for samples with thicker LAO layers. For 3uc LAO/STO samples, reversible nanoscale control of the metal-insulator transition was implemented by a conductive AFM writing. Our research furtherly discovered a very stable metal-insulator transition can be achieved by oxygen plasma (OP) treatment for samples with thicker LAO layers. AFM imaging and XPS measurement demonstrated the low energy OP treatment altered only the surface bonds, which confirmed the importance of surface properties in the heterostructures. Then microscale Hall bars were patterned at the interface and imaged by electrostatic force microscope. Their transport and magnetic properties were measured. This research will promote deeper understanding about the interfacial metal-insulator transition mechanism and open new device opportunities. This work is supported by the Department of Energy Grant No. DE-SC-0010399 and National Science Foundation Grant No. NSF-1454950.

  15. A dominant role of oxygen additive on cold atmospheric-pressure He + O{sub 2} plasmas

    SciTech Connect

    Yang, Aijun; Liu, Dingxin E-mail: xhw@mail.xjtu.edu.cn; Rong, Mingzhe; Wang, Xiaohua E-mail: xhw@mail.xjtu.edu.cn; Kong, Michael G.

    2014-08-15

    We present in this paper how oxygen additive impacts on the cold atmospheric-pressure helium plasmas by means of a one-dimensional fluid model. For the oxygen concentration [O{sub 2}] > ∼0.1%, the influence of oxygen on the electron characteristics and the power dissipation becomes important, e.g., the electron density, the electron temperature in sheath, the electron-coupling power, and the sheath width decreasing by 1.6 to 16 folds with a two-log increase in [O{sub 2}] from 0.1% to 10%. Also the discharge mode evolves from the γ mode to the α mode. The reactive oxygen species are found to peak in the narrow range of [O{sub 2}] = 0.4%–0.9% in the plasmas, similar to their power-coupling values. This applies to their wall fluxes except for those of O* and O{sub 2}{sup −}. These two species have very short lifetimes, thus only when generated in boundary layers within several micrometers next to the electrode can contribute to the fluxes. The dominant reactive oxygen species and the corresponding main reactions are schematically presented, and their relations are quantified for selected applications.

  16. Study of sterilization-treatment in pure and N- doped carbon thin films synthesized by inductively coupled plasma assisted pulsed-DC magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Javid, Amjed; Kumar, Manish; Han, Jeon Geon

    2017-01-01

    Electrically-conductive nanocrystalline carbon films, having non-toxic and non-immunogenic characteristics, are promising candidates for reusable medical devices. Here, the pure and N- doped nanocrystalline carbon films are deposited by the assistance of inductively coupled plasma (ICP) in an unbalanced facing target pulsed-DC magnetron sputtering process. Through the optical emission spectroscopy study, the role of ICP assistance and N-doping on the reactive components/radicals during the synthesis is presented. The N-doping enhances the three fold bonding configurations by increasing the ionization and energies of the plasma species. Whereas, the ICP addition increases the plasma density to control the deposition rate and film structure. As a result, sputtering-throughput (deposition rate: 31-55 nm/min), electrical resistivity (4-72 Ωcm) and water contact angle (45.12°-54°) are significantly tailored. Electric transport study across the surface microchannel confirms the superiority of N-doped carbon films for sterilization stability over the undoped carbon films.

  17. Oxygen plasma treatment and deposition of CN{sub x} on a fluorinated polymer matrix composite for improved erosion resistance

    SciTech Connect

    Muratore, C.; Korenyi-Both, A.; Bultman, J. E.; Waite, A. R.; Jones, J. G.; Storage, T. M.; Voevodin, A. A.

    2007-07-15

    The use of polymer matrix composites in aerospace propulsion applications is currently limited by insufficient resistance to erosion by abrasive media. Erosion resistant coatings may provide necessary protection; however, adhesion to many high temperature polymer matrix composite (PMC) materials is poor. A low pressure oxygen plasma treatment process was developed to improve adhesion of CN{sub x} coatings to a carbon reinforced, fluorinated polymer matrix composite. Fullerene-like CN{sub x} was selected as an erosion resistant coating for its high hardness-to-elastic modulus ratio and elastic resilience which were expected to reduce erosion from media incident at different angles (normal or glancing) relative to the surface. In situ x-ray photoelectron spectroscopy was used to evaluate the effect of the plasma treatment on surface chemistry, and electron microscopy was used to identify changes in the surface morphology of the PMC substrate after plasma exposure. The fluorine concentration at the surface was significantly reduced and the carbon fibers were exposed after plasma treatment. CN{sub x} coatings were then deposited on oxygen treated PMC substrates. Qualitative tests demonstrated that plasma treatment improved coating adhesion resulting in an erosion resistance improvement of a factor of 2 compared to untreated coated composite substrates. The combination of PMC pretreatment and coating with CN{sub x} reduced the erosion rate by an order of magnitude for normally incident particles.

  18. Real-time in situ electron spin resonance measurements on fungal spores of Penicillium digitatum during exposure of oxygen plasmas

    NASA Astrophysics Data System (ADS)

    Ishikawa, Kenji; Mizuno, Hiroko; Tanaka, Hiromasa; Tamiya, Kazuhiro; Hashizume, Hiroshi; Ohta, Takayuki; Ito, Masafumi; Iseki, Sachiko; Takeda, Keigo; Kondo, Hiroki; Sekine, Makoto; Hori, Masaru

    2012-07-01

    We report the kinetic analysis of free radicals on fungal spores of Penicillium digitatum interacted with atomic oxygen generated plasma electric discharge using real time in situ electron spin resonance (ESR) measurements. We have obtained information that the ESR signal from the spores was observed and preliminarily assignable to semiquinone radical with a g-value of around 2.004 and a line width of approximately 5G. The decay of the signal is possibly linked to the inactivation of the fungal spore. The real-time in situ ESR has proven to be a useful method to elucidate plasma-induced surface reactions on biological specimens.

  19. Control of reactive oxygen and nitrogen species production in liquid by nonthermal plasma jet with controlled surrounding gas

    NASA Astrophysics Data System (ADS)

    Ito, Taiki; Uchida, Giichiro; Nakajima, Atsushi; Takenaka, Kosuke; Setsuhara, Yuichi

    2017-01-01

    We present the development of a low-frequency nonthermal plasma-jet system, where the surrounding-gas condition of the plasma jet is precisely controlled in open air. By restricting the mixing of the ambient air into the plasma jet, the plasma jet can be selectively changed from a N2 main discharge to an O2 main discharge even in open air. In the plasma-jet system with the controlled surrounding gas, the production of reactive oxygen and nitrogen species is successfully controlled in deionized water: the concentration ratio of NO2 - to H2O2 is tuned from 0 to 0.18, and a high NO2 - concentration ratio is obtained at a N2 gas ratio of 0.80 relative to the total N2/O2 gas mixture in the main discharge gas. We also find that the NO2 - concentration is much higher in the plasma-activated medium than in the plasma-activated deionized water, which is mainly explained by the contribution of amino acids to NO2 - generation in the medium.

  20. The use of ion chromatography-dc plasma atomic emission spectrometry for the speciation of trace metals. Annual performance report, February 1, 1989--January 31, 1992

    SciTech Connect

    Urasa, I.T.

    1991-09-20

    The original objects of this research program were: to interface d.c. plasma atomic emission spectrometer with an ion chromatograph; to characterize and optimize the combined systems for application in the speciation of metals in aqueous solutions; to use this system in the study of the solution chemistry of various metals; and to find ways in which the measurement sensitivity of the method can be enhanced, thereby allowing the detection of metal species at low ppb concentration levels. This approach has been used to study the chemistry of and speciate several elements in solution including: arsenic, chromium, iron, manganese, nickel phosphorus, platinum, selenium, and vanadium. During the course of this research, we have found that the solution chemistry of the elements studied and the speciation data obtained can vary considerably depending on the solution, and the chromatographic conditions employed. The speciation of chromium, iron, and vanadium was found to be highly influenced by the acidity of the sample. The element selective nature of the d.c. plasma detector allows these changes to be monitored, thereby providing quantitative information on the new moieties formed. New approaches are being developed including the use of chelating ligands as preconcentration agents for purposes of reducing further the detection limits of the elements of interest and to improve the overall element speciation scheme. New thrusts are being directed towards the employment of post-column derivatization method coupled with colorimetric measurements to detect and quantify metal species eluting from the chromatographic column. The influence of sample acidity on these investigations will be carefully evaluated. These new thrusts are described in the accompanying Project Renewal Proposal.

  1. Optical emission spectroscopic diagnostics of a non-thermal atmospheric pressure helium-oxygen plasma jet for biomedical applications

    NASA Astrophysics Data System (ADS)

    Thiyagarajan, Magesh; Sarani, Abdollah; Nicula, Cosmina

    2013-06-01

    In this work, we have applied optical emission spectroscopy diagnostics to investigate the characteristics of a non-thermal atmospheric pressure helium plasma jet. The discharge characteristics in the active and afterglow region of the plasma jet, that are critical for biomedical applications, have been investigated. The voltage-current characteristics of the plasma discharge were analyzed and the average plasma power was measured to be around 18 W. The effect of addition of small fractions of oxygen at 0.1%-0.5% on the plasma jet characteristics was studied. The addition of oxygen resulted in a decrease in plasma plume length due to the electronegativity property of oxygen. Atomic and molecular lines of selected reactive plasma species that are considered to be useful to induce biochemical reactions such as OH transitions A2Σ+(ν=0,1)→X2Π(Δν =0) at 308 nm and A2Σ+(ν=0,1)→X2Π(Δν =1) at 287 nm, O I transitions 3p5P→3s5S0 at 777.41 nm, and 3p3P→3s3S0 at 844.6 nm, N2(C-B) second positive system with electronic transition C3Πu→B3Πg in the range of 300-450 nm and N2+(B-X) first negative system with electronic transition B2Σu+→X2Σg+(Δν =0) at 391.4 nm have been studied. The atomic emission lines of helium were identified, including the He I transitions 3p3P0→2s3S at 388.8 nm, 3p1P0→ 2s1S at 501.6 nm, 3d3D→2p3P0 at 587.6 nm, 3d1D→2p1P0 at 667.8 nm, 3s3S1→2p3P0 at 706.5 nm, 3s1S0→2p1P0 at 728.1 nm, and Hα transition 2p-3d at 656.3 nm. Using a spectral fitting method, the OH radicals at 306-312 nm, the rotational and vibrational temperatures equivalent to gas temperatures of the discharge was measured and the effective non-equilibrium nature of the plasma jet was demonstrated. Our results show that, in the entire active plasma region, the gas temperature remains at 310 ± 25 K and 340 ± 25 K and it increases to 320 ± 25 K and 360 ± 25 K in the afterglow region of the plasma jet for pure helium and helium/oxygen (0.1%) mixture

  2. Effect of N{sub 2} and Ar gas on DC arc plasma generation and film composition from Ti-Al compound cathodes

    SciTech Connect

    Zhirkov, Igor Rosen, Johanna; Oks, Efim

    2015-06-07

    DC arc plasma from Ti, Al, and Ti{sub 1−x}Al{sub x} (x = 0.16, 0.25, 0.50, and 0.70) compound cathodes has been characterized with respect to plasma chemistry (charged particles) and charge-state-resolved ion energy for Ar and N{sub 2} pressures in the range 10{sup −6} to 3 × 10{sup −2} Torr. Scanning electron microscopy was used for exploring the correlation between the cathode and film composition, which in turn was correlated with the plasma properties. In an Ar atmosphere, the plasma ion composition showed a reduction of Al of approximately 5 at. % compared to the cathode composition, while deposited films were in accordance with the cathode stoichiometry. Introducing N{sub 2} above ∼5 × 10{sup −3} Torr, lead to a reduced Al content in the plasma as well as in the film, and hence a 1:1 correlation between the cathode and film composition cannot be expected in a reactive environment. This may be explained by an influence of the reactive gas on the arc mode and type of erosion of Ti and Al rich contaminations, as well as on the plasma transport. Throughout the investigated pressure range, a higher deposition rate was obtained from cathodes with higher Al content. The origin of generated gas ions was investigated through the velocity rule, stating that the most likely ion velocities of all cathode elements from a compound cathode are equal. The results suggest that the major part of the gas ions in Ar is generated from electron impact ionization, while gas ions in a N{sub 2} atmosphere primarily originate from a nitrogen contaminated layer on the cathode surface. The presented results provide a contribution to the understanding processes of plasma generation from compound cathodes. It also allows for a more reasonable approach to the selection of composite cathode and experimental conditions for thin film depositions.

  3. [Spectral analysis of oxygen radical in a synergistic system of pulsed discharge plasma/TiO2].

    PubMed

    Wang, Hui-Juan; Li, Jie; Chu, Jin-Yu

    2011-01-01

    Based on the synergistic effect of pulsed discharge plasma and titanium dioxide (TiO2) photocatalysis, a coupling system of pulsed discharge plasma/TiO2 was set up in the present paper, by using the ultraviolet radiation produced during the pulsed discharge process. TiO2 film immobilized on the glass beads was used as the photocatalyst in the synergistic system. In the research, the synergistic mechanism of pulsed discharge plasma and TiO2 photocatalysis was reviewed by the spectral diagnosis of oxygen radical (* O radical) produced in different reaction systems. The obtained results showed that the characteristic emission spectrum of * O radical could be observed at 777 nm and the corresponding transitions was 3p5 P --> 3s5 S. When air was used as bubbling gas, the relative emission intensity of * O radical recorded in the synergistic system was stronger than that in the plasma alone system, and the same result was also obtained when oxygen (O2) was used as bubbling gas. This result revealed that the photocatalytic activity of the immobilized TiO2 in the synergistic system could be induced by the ultraviolet radiation formed during the pulsed discharge process. In the systems of pulsed discharge plasma alone and pulsed discharge plasma combined with TiO2 photocatalysis, the relative emission intensity of * O radical in distilled water was stronger than that in phenol solutions. The results showed that * O radical was one of responsible radicals for phenol degradation in the pulsed discharge plasma alone system as well as the synergistic system.

  4. Extremely high wear resistance and ultra-low friction behaviour of oxygen-plasma-treated nanocrystalline diamond films

    NASA Astrophysics Data System (ADS)

    Radhika, R.; Kumar, N.; Sankaran, K. J.; Dumpala, Ravikumar; Dash, S.; Ramachandra Rao, M. S.; Arivuoli, D.; Tyagi, A. K.; Tai, N. H.; Lin, I.-Nan

    2013-10-01

    The diamond nanowire (DNW) film was deposited by N2-enriched microwave plasma-enhanced chemical vapour deposition (MPECVD) process. As-deposited DNW film was treated in O2 plasma which resulted in chemical and microstructural modification. Sheath of the DNW film is chemically constituted by amorphous carbon (a-C)- and graphite (sp2C=C)-like bonding. However, nanowires transformed into ultra-small spherical grains after the O2-plasma treatments. In this condition, a-C and sp2C=C bonding significantly reduced due to plasma etching caused by oxygen atoms. After the O2-plasma treatment, formation of functional groups such as C=O, C-O-C, O-H, O-CH3 and H2O was observed on the surface and inside the wear track as evident from the micro FTIR analysis. H2O is hydrogen bonded to oxygen-containing groups such as -OH and -H. The O2-plasma-exposed DNW film exhibits surface charging and causes formation of dangling bonds and electron trapping centres. This results in significant decrease in contact angle, hence superhydrophilic behaviour. The friction coefficient of O2-plasma-treated film showed super low value ˜0.002 with high wear resistance 2 × 10-12 mm3 N-1 m-1. In the reciprocating ball-on-disc tribology test, only ˜80 nm wear loss was observed after the 1 km of sliding distance at 10 N loads. Such an advance in tribological properties is explained by passivation of covalent carbon bonding and transformation of sliding surfaces by weak van der Waals and hydrogen bondings. High surface energy and the consequent superhydrophilic behaviour of film is attributed to the formation of the above-mentioned functional groups on the surface. This protects against deformation of the wear track leading to extremely high wear resistance.

  5. Hydrodynamic and direct-current insulator-based dielectrophoresis (H-DC-iDEP) microfluidic blood plasma separation.

    PubMed

    Mohammadi, Mahdi; Madadi, Hojjat; Casals-Terré, Jasmina; Sellarès, Jordi

    2015-06-01

    Evaluation and diagnosis of blood alterations is a common request for clinical laboratories, requiring a complex technological approach and dedication of health resources. In this paper, we present a microfluidic device that owing to a novel combination of hydrodynamic and dielectrophoretic techniques can separate plasma from fresh blood in a microfluidic channel and for the first time allows optical real-time monitoring of the components of plasma without pre- or post-processing. The microchannel is based on a set of dead-end branches at each side and is initially filled using capillary forces with a 2-μL droplet of fresh blood. During this process, stagnation zones are generated at the dead-end branches and some red blood cells (RBCs) are trapped there. An electric field is then applied and dielectrophoretic trapping of RBCs is used to prevent more RBCs entering into the channel, which works like a sieve. Besides, an electroosmotic flow is generated to sweep the rest of the RBCs from the central part of the channel. Consequently, an RBC-free zone of plasma is formed in the middle of the channel, allowing real-time monitoring of the platelet behavior. To study the generation of stagnation zones and to ensure RBC trapping in the initial constrictions, two numerical models were solved. The proposed experimental design separates up to 0.1 μL blood plasma from a 2-μL fresh human blood droplet. In this study, a plasma purity of 99 % was achieved after 7 min, according to the measurements taken by image analysis. Graphical Abstract Schematics of a real-time plasma monitoring system based on a Hydrodynamic and direct-current insulator-based dielectrophoresis microfluidic channel.

  6. Oxygen plasma surface modification augments poly(L-lactide-co-glycolide) cytocompatibility toward osteoblasts and minimizes immune activation of macrophages.

    PubMed

    Scislowska-Czarnecka, Anna; Szmigiel, Dariusz; Genet, Michel; Dupont-Gillain, Christine; Pamula, Elzbieta; Kolaczkowska, Elzbieta

    2015-12-01

    Here, we report on modification of one of the model biomedical polymers, poly L-lactide-co-glycolide (PLGA; 85:15), by reactive ion etching (RIE) oxygen plasma treatment. PLGA's major disadvantage is high hydrophobicity which restrains binding of cell-adhesive proteins and host cells. In the current approach, we aimed to answer two questions: (1) will only short (10 s) and moderate (20-200 mTorr, 45-90 W) RIE oxygen plasma treatment, leading to decrease of water contact angle by only up to 10°, sufficiently improve PLGA adherence to cells, and (2) how will this affect osteoblasts and activation of the immune system? All obtained modified PLGAs had improved hydrophilicity but unaltered roughness (as revealed by water contact angle measurements, X-ray photoelectron spectroscopy, and atomic force microscopy) resulting in significantly improved adhesion of osteoblasts (MG-63) and their low activation. Importantly, macrophages (RAW 264.7), one of the key cells initiating inflammation and bone resorption, responded significantly less vigorously to the modified polymers, expressing/releasing lower amounts of nitric oxide, matrix metalloproteinases (MMP-9), and pro-inflammatory cytokines (TNF-α, IL-6, IL-12p70, IFN-γ, IL-10). We conclude that already slight RIE oxygen plasma modification of PLGA is sufficient to improve its surface properties, and enhance cytocompatibility. Most importantly, this type of modification prevents excessive immune response.

  7. Surface modification of PdlLGA microspheres with gelatine methacrylate: Evaluation of adsorption, entrapment, and oxygen plasma treatment approaches.

    PubMed

    Baki, Abdulrahman; Rahman, Cheryl V; White, Lisa J; Scurr, David J; Qutachi, Omar; Shakesheff, Kevin M

    2017-01-16

    Injectable poly (dl-lactic-co-glycolic acid) (PdlLGA) microspheres are promising candidates as biodegradable controlled release carriers for drug and cell delivery applications; however, they have limited functional groups on the surface to enable dense grafting of tissue specific biocompatible molecules. In this study we have evaluated surface adsorption, entrapment and oxygen plasma treatment as three approaches to modify the surfaces of PdlLGA microspheres with gelatine methacrylate (gel-MA) as a biocompatible and photo cross-linkable macromolecule. Time of flight secondary ion mass spectroscopy (TOF SIMS) and X-ray photoelectron spectroscopy (XPS) were used to detect and quantify gel-MA on the surfaces. Fluorescent and scanning electron microscopies (SEM) were used to image the topographical changes. Human mesenchymal stem cells (hMSCs) of immortalised cell line were cultured on the surface of gel-MA modified PdlLGA microspheres and Presto-Blue assay was used to study the effect of different surface modifications on cell proliferation. Data analysis showed that the oxygen plasma treatment approach resulted in the highest density of gel-MA deposition. This study supports oxygen plasma treatment as a facile approach to modify the surface of injectable PdlLGA microspheres with macromolecules such as gel-MA to enhance proliferation rate of injected cells and potentially enable further grafting of tissue specific molecules.

  8. Improvement in nano-hardness and corrosion resistance of low carbon steel by plasma nitriding with negative DC bias voltage

    NASA Astrophysics Data System (ADS)

    Alim, Mohamed Mounes; Saoula, Nadia; Tadjine, Rabah; Hadj-Larbi, Fayçal; Keffous, Aissa; Kechouane, Mohamed

    2016-10-01

    In this work, we study the effect of plasma nitriding on nano-hardness and corrosion resistance of low carbon steel samples. The plasma was generated through a radio-frequency inductively coupled plasma source. The substrate temperature increased (by the self-induced heating mechanism) with the treatment time for increasing negative bias voltages. X-rays diffraction analysis revealed the formation of nitride phases (ɛ-Fe2-3N and γ'-Fe4N) in the compound layer of the treated samples. A phase transition occurred from 3.5 kV to 4.0 kV and was accompanied by an increase in the volume fraction of the γ'-Fe4N phase and a decrease in that of the ɛ-Fe2-3N phase. Auger electron spectroscopy revealed a deep diffusion of the implanted nitrogen beyond 320 nm. The nano-hardness increased by ~400% for the nitrogen-implanted samples compared to the untreated state, the nitride phases are believed to participate to the hardening. Potentiodynamic polarization measurements revealed that the plasma nitriding has improved the corrosion resistance behavior of the material. When compared to the untreated state, the sample processed at 4.0 kV exhibits a shift of +500 mV and a reduction to 3% in its corrosion current. These results were obtained for relatively low bias voltages and short treatment time (2 h).

  9. Reactive molecular dynamics simulations of oxygen species in a liquid water layer of interest for plasma medicine

    NASA Astrophysics Data System (ADS)

    Yusupov, M.; Neyts, E. C.; Simon, P.; Berdiyorov, G.; Snoeckx, R.; van Duin, A. C. T.; Bogaerts, A.

    2014-01-01

    The application of atmospheric pressure plasmas in medicine is increasingly gaining attention in recent years, although very little is currently known about the plasma-induced processes occurring on the surface of living organisms. It is known that most bio-organisms, including bacteria, are coated by a liquid film surrounding them, and there might be many interactions between plasma species and the liquid layer before the plasma species reach the surface of the bio-organisms. Therefore, it is essential to study the behaviour of the reactive species in a liquid film, in order to determine whether these species can travel through this layer and reach the biomolecules, or whether new species are formed along the way. In this work, we investigate the interaction of reactive oxygen species (i.e. O, OH, HO2 and H2O2) with water, which is assumed as a simple model system for the liquid layer surrounding biomolecules. Our computational investigations show that OH, HO2 and H2O2 can travel deep into the liquid layer and are hence in principle able to reach the bio-organism. Furthermore, O, OH and HO2 radicals react with water molecules through hydrogen-abstraction reactions, whereas no H-abstraction reaction takes place in the case of H2O2. This study is important to gain insight into the fundamental operating mechanisms in plasma medicine, in general, and the interaction mechanisms of plasma species with a liquid film, in particular.

  10. An atmospheric-pressure cold plasma leads to apoptosis in Saccharomyces cerevisiae by accumulating intracellular reactive oxygen species and calcium

    NASA Astrophysics Data System (ADS)

    Ma, R. N.; Feng, H. Q.; Liang, Y. D.; Zhang, Q.; Tian, Y.; Su, B.; Zhang, J.; Fang, J.

    2013-07-01

    A non-thermal plasma is known to induce apoptosis of various cells but the mechanism is not yet clear. A eukaryotic model organism Saccharomyces cerevisiaewas used to investigate the cellular and biochemical regulations of cell apoptosis and cell cycle after an atmospheric-pressure cold plasma treatment. More importantly, intracellular calcium (Ca2+) was first involved in monitoring the process of plasma-induced apoptosis in this study. We analysed the cell apoptosis and cell cycle by flow cytometry and observed the changes in intracellular reactive oxygen species (ROS) and Ca2+ concentration, cell mitochondrial membrane potential (Δψm) as well as nuclear DNA morphology via fluorescence staining assay. All experimental results indicated that plasma-generated ROS leads to the accumulation of intracellular ROS and Ca2+ that ultimately contribute to apoptosis associated with cell cycle arrest at G1 phase through depolarization of Δψm and fragmenting nuclear DNA. This work provides a novel insight into the physical and biological mechanism of apoptosis induced by a plasma which could benefit for promoting the development of plasmas applied to cancer therapy.

  11. Tuning the electrical property via defect engineering of single layer MoS2 by oxygen plasma.

    PubMed

    Islam, Muhammad R; Kang, Narae; Bhanu, Udai; Paudel, Hari P; Erementchouk, Mikhail; Tetard, Laurene; Leuenberger, Michael N; Khondaker, Saiful I

    2014-09-07

    We have demonstrated that the electrical property of single-layer molybdenum disulfide (MoS2) can be significantly tuned from the semiconducting to the insulating regime via controlled exposure to oxygen plasma. The mobility, on-current and resistance of single-layer MoS2 devices were varied by up to four orders of magnitude by controlling the plasma exposure time. Raman spectroscopy, X-ray photoelectron spectroscopy and density functional theory studies suggest that the significant variation of electronic properties is caused by the creation of insulating MoO3-rich disordered domains in the MoS2 sheet upon oxygen plasma exposure, leading to an exponential variation of resistance and mobility as a function of plasma exposure time. The resistance variation calculated using an effective medium model is in excellent agreement with the measurements. The simple approach described here can be used for the fabrication of tunable two-dimensional nanodevices based on MoS2 and other transition metal dichalcogenides.

  12. Modification of polypropylene foils by low pressure oxygen plasma and its influence on the formation of titanium dioxide films

    NASA Astrophysics Data System (ADS)

    Sadowski, Rafal; Macyk, Wojciech

    2014-10-01

    Commercially available polypropylene foils were pre-treated with low pressure, room temperature radio frequency (RF) oxygen plasma at constant power and pressure. Various durations of pre-treatment process were applied. Afterwards the samples were covered with titanium dioxide thin film by dip-coating technique and photosensitized by titanium(IV) surface complexes formed upon impregnation with catechol-like ligands. Optical emission spectroscopy (OES) measurements were used for determining plasma species. The surface properties before and after plasma treatment were characterized by contact angle measurements, FTIR-ATR, UV-Vis, and X-ray photoelectron spectroscopy (XPS). Titanium dioxide thin films were characterized by scanning electron microscopy (SEM) and UV-Vis spectroscopy. The photoactivity of TiO2 films was tested by photocurrent measurements. It was shown that plasma pre-treatment is essential for oxygen groups formation which contribute to titanium dioxide binding to polymer surface. The support from National Science Centre within the DEC-2012/05/N/ST5/01497 grant is highly acknowledged.

  13. Deposition and properties of high-velocity-oxygen-fuel and plasma-sprayed Mo-Mo2C composite coatings

    NASA Astrophysics Data System (ADS)

    Prchlik, L.; Gutleber, J.; Sampath, S.

    2001-12-01

    Molybdenum thermal-spray coatings, dispersion strengthened by molybdenum oxides and molybdenum carbides, play an important role in industrial tribological applications. Traditionally, they have been prepared by plasma and wire flame spraying. High porosity and lower cohesion strength limit their application in situations where both galling and abrasion wear is involved. In this study, high-velocity-oxygen-fuel (HVOF) deposition of molybdenum and molybdenum carbide coatings was attempted. Deposition was achieved for all powders used. Composition, microstructure, mechanical, and wear properties of the HVOF synthesized coatings were evaluated and compared with plasma-sprayed counterparts. The HVOF coatings possessed a very good abrasion resistance, whereas plasma deposits performed better in dry sliding tests. Measurements showed a close relationship between the coating surface hardness and its abrasion resistance. Results also suggested correlation between molybdenum carbide distribution in the molybdenum matrix and the sliding friction response of Mo-Mo2C coatings.

  14. Effect of oxygen plasma on field emission characteristics of single-wall carbon nanotubes grown by plasma enhanced chemical vapour deposition system

    SciTech Connect

    Kumar, Avshish; Parveen, Shama; Husain, Samina; Ali, Javid; Zulfequar, Mohammad; Harsh; Husain, Mushahid

    2014-02-28

    Field emission properties of single wall carbon nanotubes (SWCNTs) grown on iron catalyst film by plasma enhanced chemical vapour deposition system were studied in diode configuration. The results were analysed in the framework of Fowler-Nordheim theory. The grown SWCNTs were found to be excellent field emitters, having emission current density higher than 20 mA/cm{sup 2} at a turn-on field of 1.3 V/μm. The as grown SWCNTs were further treated with Oxygen (O{sub 2}) plasma for 5 min and again field emission characteristics were measured. The O{sub 2} plasma treated SWCNTs have shown dramatic improvement in their field emission properties with emission current density of 111 mA/cm{sup 2} at a much lower turn on field of 0.8 V/μm. The as grown as well as plasma treated SWCNTs were also characterized by various techniques, such as scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy before and after O{sub 2} plasma treatment and the findings are being reported in this paper.

  15. Bidirectional DC/DC Converter

    NASA Astrophysics Data System (ADS)

    Pedersen, F.

    2008-09-01

    The presented bidirectional DC/DC converter design concept is a further development of an already existing converter used for low battery voltage operation.For low battery voltage operation a high efficient low parts count DC/DC converter was developed, and used in a satellite for the battery charge and battery discharge function.The converter consists in a bidirectional, non regulating DC/DC converter connected to a discharge regulating Buck converter and a charge regulating Buck converter.The Bidirectional non regulating DC/DC converter performs with relatively high efficiency even at relatively high currents, which here means up to 35Amps.This performance was obtained through the use of power MOSFET's with on- resistances of only a few mille Ohms connected to a special transformer allowing paralleling several transistor stages on the low voltage side of the transformer. The design is patent protected. Synchronous rectification leads to high efficiency at the low battery voltages considered, which was in the range 2,7- 4,3 Volt DC.The converter performs with low switching losses as zero voltage zero current switching is implemented in all switching positions of the converter.Now, the drive power needed, to switch a relatively large number of low Ohm , hence high drive capacitance, power MOSFET's using conventional drive techniques would limit the overall conversion efficiency.Therefore a resonant drive consuming considerable less power than a conventional drive circuit was implemented in the converter.To the originally built and patent protected bidirectional non regulating DC/DC converter, is added the functionality of regulation.Hereby the need for additional converter stages in form of a Charge Buck regulator and a Discharge Buck regulator is eliminated.The bidirectional DC/DC converter can be used in connection with batteries, motors, etc, where the bidirectional feature, simple design and high performance may be useful.

  16. Oxygen-Plasma-Treated Indium-Tin-Oxide Films on Nonalkali Glass Deposited by Super Density Arc Plasma Ion Plating

    NASA Astrophysics Data System (ADS)

    Kim, Soo Young; Hong, Kihyon; Son, Jun Ho; Jung, Gwan Ho; Lee, Jong-Lam; Choi, Kyu Han; Song, Kyu Ho; Ahn, Kyung Chul

    2008-02-01

    The effects of O2 plasma treatment on both the chemical composition and work function of an indium-tin-oxide (ITO) film were investigated. ITO films were deposited on non-alkali glass substrate by super density arc plasma ion plating for application in active-matrix organic light-emitting diodes (OLEDs). The water contact angle decreased from 38 to 11° as the ITO films were treated with O2 plasma for 60 s at a plasma power of 150 W, indicating an increase in the hydrophilicity of the surface. It was found that there were no distinct changes in the microstructure or electrical properties of the ITO films with O2 plasma treatment. Synchrotron radiation photoemission spectroscopy data revealed that O2 plasma treatment decreased the amount of carbon contamination and increased the number of unscreened states of In3+ and (O2)2- peroxo species. This played the role of increasing the work function of the ITO films by 1.7 eV. As a result, the turn-on voltage of the OLED decreased markedly from 24 to 8 V and the maximum luminance value of the OLED increased to 2500 cd/m2.

  17. M3D-C1 simulations of the plasma response to n = 3 magnetic perturbations applied to the NSTX-U snowflake divertor

    NASA Astrophysics Data System (ADS)

    Canal, G. P.; Ferraro, N. M.; Evans, T. E.; Osborne, T. H.; Menard, J. E.; Ahn, J.-W.; Maingi, R.; Wingen, A.; Ciro, D.; Frerichs, H.; Schmitz, O.; Soukhanoviskii, V.; Waters, I.

    2016-10-01

    Single- and two-fluid resistive magnetohydrodynamic simulations, performed with the code M3D-C1, are used to investigate the effect of n = 3 magnetic perturbations on the SF divertor configuration. The calculations are based on simulated NSTX-U plasmas and the results show that additional and longer magnetic lobes are created in the null-point region of the SF configuration, compared to those in the conventional single-null. The intersection of these additional and longer lobes with the divertor plates are expected to cause more striations in the particle and heat flux target profiles. In addition, the results indicate that the size of the magnetic lobes, in both single-null and SF configurations, are more sensitive to resonant than to non-resonant magnetic perturbations. The results also suggest that lower values of current in non-axisymmetric control coils close enough to the primary x-point would be required to suppress edge localized modes in plasmas with the SF configuration. This work has been supported by the US Department of Energy, Office of Science, Office of Fusion Energy Science under DOE Award DE-SC0012706.

  18. The Effects of Oxygen Plasma on the Chemical Composition and Morphology of the Ru Capping Layer of the Extreme Ultraviolet (EUV) Mask Blanks

    SciTech Connect

    Belau, Leonid; Park, Jeong Y.; Liang, Ted; Somorjai, Gabor A.

    2008-06-07

    Contamination removal from extreme ultraviolet (EUV) mask surfaces is one of the most important aspects to improve reliability for the next generation of EUV lithography. We report chemical and morphological changes of the ruthenium (Ru) mask surface after oxygen plasma treatment using surface sensitive analytical methods: X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and transmission electron microscopy (TEM). Chemical analysis of the EUV masks shows an increase in the subsurface oxygen concentration, Ru oxidation and surface roughness. XPS spectra at various photoelectron takeoff angles suggest that the EUV mask surface was covered with chemisorbed oxygen after oxygen plasma treatment. It is proposed that the Kirkendall effect is the most plausible mechanism that explains the Ru surface oxidation. The etching rate of the Ru capping layer by oxygen plasma was estimated to be 1.5 {+-} 0.2 {angstrom}/min, based on TEM cross sectional analysis.

  19. Penicillin impregnation on oxygen plasma surface functionalized chitosan/Antheraea assama silk fibroin: Studies of antibacterial activity and antithrombogenic property.

    PubMed

    Choudhury, Arup Jyoti; Gogoi, Dolly; Kandimalla, Raghuram; Kalita, Sanjeeb; Chaudhari, Yogesh B; Khan, Mojibur R; Kotoky, Jibon; Chutia, Joyanti

    2016-03-01

    Low temperature plasma can effectively tailor the surface properties of natural polymeric biomaterials according to the need for various biomedical applications. Non-mulberry silk, Antheraea assama silk fibroin (AASF) is a natural polymer having excellent biocompatibility and mechanical strength yet unlike mulberry silk, Bombyx mori silk fibroin, has drawn less interest in biomedical research. In the quest for developing as potential biomaterial, surface functionalization of plasma induced chitosan (Cs) grafted AASF ((AASF/O2-CS)g/O2) yarn is carried out using oxygen (O2) plasma. The (AASF/O2-CS)g/O2 yarn exhibits enhanced antithrombogenic property as well as antimicrobial activity against Gram positive (Bacillus subtilis) and Gram negative (Escherichia coli) bacteria as compared to AASF yarn. Moreover, impregnation of antibiotic drug (penicillin G sodium salt, PEN) on (AASF/O2-CS)g/O2 yarn further improves the observed properties. In-vitro hemolysis assay reveals that O2 plasma treatment and subsequent impregnation of PEN do not affect the hemocompatibility of AASF yarn. The present research findings demonstrate that plasma induced grafting of Cs followed by penicillin impregnation could significantly improve the potential applicability of AASF in the field of surgical research.

  20. Changes in peak oxygen uptake and plasma volume in fit and unfit subjects following exposure to a simulation of microgravity

    NASA Technical Reports Server (NTRS)

    Convertino, V. A.

    1998-01-01

    To test the hypothesis that the magnitude of reduction in plasma volume and work capacity following exposure to simulated microgravity is dependent on the initial level of aerobic fitness, peak oxygen uptake (VO2peak) was measured in a group of physically fit subjects and compared with VO2peak in a group of relatively unfit subjects before and after 10 days of continuous 6 degrees head-down tilt (HDT). Ten fit subjects (40 +/- 2 year) with mean +/- SE VO2peak = 48.9 +/- 1.7 mL kg-1 min-1 were matched for age, height, and lean body weight with 10 unfit subjects (VO2peak = 37.7 +/- 1.6 mL kg-1 min-1). Before and after HDT, plasma, blood, and red cell volumes and body composition were measured and all subjects underwent a graded supine cycle ergometer test to determine VO2peak period needed. Reduced VO2peak in fit subjects (-16.2%) was greater than that of unfit subjects (-6.1%). Similarly, reductions in plasma (-18.3%) and blood volumes (-16.0%) in fit subjects were larger than those of unfit subjects (blood volume = -5.6%; plasma volume = -6.6%). Reduced plasma volume was associated with greater negative body fluid balance during the initial 24 h of HDT in the fit group (912 +/- 154 mL) compared with unfit subjects (453 +/- 200 mL). The percentage change for VO2peak correlated with percentage change in plasma volume (r = +0.79). Following exposure to simulated microgravity, fit subjects demonstrated larger reductions in VO2peak than unfit subjects which was associated with larger reductions in plasma and blood volume. These data suggest that the magnitude of physical deconditioning induced by exposure to microgravity without intervention of countermeasures was influenced by the initial fitness of the subjects.

  1. Roles of plasma-generated vacuum-ultraviolet photons and oxygen radicals in damaging nanoporous low-k films

    SciTech Connect

    Lee, Joe; Graves, David B.

    2013-07-15

    One important class of low-k materials used as interconnect dielectrics employs methyl groups added to nanoporous SiO{sub 2} matrices. These carbon-doped oxide materials are known to be susceptible to damage from plasma species during various stages of plasma processing. Two key active species generated in O{sub 2} plasma are oxygen (O) radicals and vacuum-ultraviolet (VUV) photons. These species are known to cause carbon loss, resulting in damaging increases in dielectric constant throughout the film. However, the mechanisms through which this damage is incurred are poorly understood. By capping the substrate in different ways during plasma exposure, it is possible to expose films to either photons alone or O atoms alone. The authors report measurements of damage induced by VUV photons only, O radicals only, and the combination of O radicals and photons. Through HF stripping, they note that carbon extraction from photons and from radicals yields different outcomes; the profile of carbon concentration within the modified region is different for each case. Damage from photons alone can be modeled and model predictions are in good agreement with measurements. Damage from O atoms alone can only be modeled if it is assumed that the near-surface region has a significantly reduced diffusivity compared to the bulk of the film. Experiment and model agree that both photons alone and O radicals alone damage the material by removing carbon. When radicals and photons are present simultaneously during plasma exposure, however, more C removal appears to be occurring in the model than experimentally observed. Remarkably, if only radicals are exposed to the film after short (10-30 s) plasma exposures, very little additional damage is incurred during this radical-only exposure. The most straightforward interpretation of these results appears to be that photons combine synergistically with radicals in the pores to narrow the pores, thereby reducing film diffusivity in the C

  2. Effect of oxygen plasma modification on refractive index sensing with micro-cavity in-line Mach-Zehnder interferometer

    NASA Astrophysics Data System (ADS)

    Debowska, Anna K.; Dominik, Magdalena; Koba, Marcin; Janik, Monika; Bock, Wojtek; Śmietana, Mateusz

    2016-12-01

    A micro-cavity in-line Mach-Zehnder interferometer (μIMZI) is an optical sensing structure fabricated in an optical fiber. Its design allows for refractive index sensing of liquid and gas in picoliter volumes, making it suitable for biochemical and medical sensing where measured material is often scarce. The fabricated structures show satisfactory levels of sensitivity, from about 400 nm/RIU in the near-water range of solutions (nD 1.336+/-0.003 RIU) to about 16 000 nm/RIU for solutions in approximate range from nD = 1.35 RIU to nD = 1.4 RIU. The structures were subjected to oxygen plasma, the process which was supposed to modify physical parameters of the structures, i.e., cavity surface wettability and roughness, and in consequence their sensitivity. As a result of the oxygen plasma modification we have observed a improved wettability of the structure surface, what makes it easier to introduce liquid into the cavity and simplifies the measurement process. In the case where the plasma processing is preceded by biological layer deposition, the bottom surface of the structure is smoothed and slightly deepened, causing a shift in the transmission spectrum and change in sensitivity.

  3. Milliwatt dc/dc Inverter

    NASA Technical Reports Server (NTRS)

    Mclyman, C. W.

    1983-01-01

    Compact dc/dc inverter uses single integrated-circuit package containing six inverter gates that generate and amplify 100-kHz square-wave switching signal. Square-wave switching inverts 10-volt local power to isolated voltage at another desired level. Relatively high operating frequency reduces size of filter capacitors required, resulting in small package unit.

  4. Cold plasma processing of local planetary ores for oxygen and metallurgically important metals

    NASA Technical Reports Server (NTRS)

    Lynch, D. C.; Bullard, D.; Ortega, R.

    1991-01-01

    The utilization of a cold or nonequilibrium plasma in chlorination processing is discussed. Titanium dioxide (TiO2) was successfully chlorinated at temperatures between 700 and 900 C without the aid of carbon. In addition to these initial experiments, a technique was developed for determining the temperature of a specimen in a plasma. Development of that technique has required evaluating the emissivity of TiO2, ZrO2, and FeOTiO2 and analyzing the specimen temperature in a plasma as a function of both power absorbed by the plasma and the pressure of the plasma. The mass spectrometer was also calibrated with TiCl4 and CCl4 vapor.

  5. Mass spectrometric study on inactivation mechanism of spore-forming bacteria by low-pressure surface-wave excited oxygen plasma

    SciTech Connect

    Zhao Ying; Ogino, Akihisa; Nagatsu, Masaaki

    2011-05-09

    In this letter, the etching phenomena of the spore-forming bacteria by oxygen plasma were investigated by using quadrupole mass spectrometry. The etching by-products of H{sub 2}O and CO{sub 2} were obviously detected during the oxygen plasma irradiation by the multiple ion detection measurement. Inactivation of roughly 10{sup 6} spores population was achieved under almost the same reduced spore shapes for three different incident microwave powers. It is considered from the present results that the oxygen radical etching could cause damage to the germinant receptors located in the inner membrane inevitable for germination of spores, without any damage of the DNA in the cores.

  6. Mass spectrometric study on inactivation mechanism of spore-forming bacteria by low-pressure surface-wave excited oxygen plasma

    NASA Astrophysics Data System (ADS)

    Zhao, Ying; Ogino, Akihisa; Nagatsu, Masaaki

    2011-05-01

    In this letter, the etching phenomena of the spore-forming bacteria by oxygen plasma were investigated by using quadrupole mass spectrometry. The etching by-products of H2O and CO2 were obviously detected during the oxygen plasma irradiation by the multiple ion detection measurement. Inactivation of roughly 106 spores population was achieved under almost the same reduced spore shapes for three different incident microwave powers. It is considered from the present results that the oxygen radical etching could cause damage to the germinant receptors located in the inner membrane inevitable for germination of spores, without any damage of the DNA in the cores.

  7. Case Report of Severe Antithrombin Deficiency During Extracorporeal Membrane Oxygenation and Therapeutic Plasma Exchange for Double Lung Transplantation.

    PubMed

    Williams, Brittney; Mazzeffi, Michael A; Sanchez, Pablo G; Pham, Si M; Kon, Zachary; Tanaka, Kenichi A

    2017-01-01

    Acquired antithrombin (AT) deficiency is not uncommon in cardiothoracic surgery because of heparin exposure and dilutional or consumptive losses. We report a case of acquired AT deficiency and resultant multiple deep vein thrombosis in a patient with pulmonary fibrosis on veno-venous extracorporeal membrane oxygenation who underwent double lung transplantation with intraoperative therapeutic plasma exchange (TPE) as a part of an immunomodulation regimen for allosensitization. Preoperative heparin anticoagulation resulted in AT deficiency, which was further exacerbated by TPE using albumin. The recovery of AT activity after TPE with plasma was incomplete, and postoperative deficiencies of AT and other anticoagulants might have contributed to deep vein thromboses. The limitation of thromboelastometry in detecting AT deficiency was evident.

  8. Atmospheric plasma generates oxygen atoms as oxidizing species in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Mokhtar Hefny, Mohamed; Pattyn, Cedric; Lukes, Petr; Benedikt, Jan

    2016-10-01

    A remote microscale atmospheric pressure plasma jet (µAPPJ) with He, He/H2O, He/O2, and He/O2/H2O gas mixtures was used to study the transport of reactive species from the gas phase into the liquid and the following aqueous phase chemistry. The effects induced by the µAPPJ in water were quantitatively studied using phenol as a chemical probe and by measuring H2O2 concentration and pH values. These results were combined with the analysis of the absolute densities of the reactive species and the modeling of convective/diffusion transport and recombination reactions in the effluent of the plasma jet. Additionally, modified plasma jets were used to show that the role of emitted photons in aqueous chemistry is negligible for these plasma sources. The fastest phenol degradation was measured for the He/O2 plasma, followed by He/H2O, He/O2/H2O, and He plasmas. The modeled quantitative flux of O atoms into the liquid in the He/O2 plasma case was highly comparable with the phenol degradation rate and showed a very high transfer efficiency of reactive species from the plasma into the liquid, where more than half of the O atoms leaving the jet nozzle entered the liquid. The results indicate that the high oxidative effect of He/O2 plasma was primarily due to solvated O atoms, whereas OH radicals dominated the oxidative effects induced in water by plasmas with other gas mixtures. These findings help to understand, in a quantitative way, the complex interaction of cold atmospheric plasmas with aqueous solutions and will allow a better understanding of the interaction of these plasmas with water or buffered solutions containing biological macromolecules, microorganisms, or even eukaryotic cells. Additionally, the µAPPJ He/O2 plasma source seems to be an ideal tool for the generation of O atoms in aqueous solutions for any future studies of their reactivity.

  9. COMPARATIVE ANALYSIS OF REACTIVE OXYGEN SPECIES IN HUMAN PLASMA AND BLOOD

    EPA Science Inventory

    Reactive oxygen species (ROS) are commonly associated with diseased states (including asthma, cardiovascular disease, cancer) infections, and exposure to various toxicants in humans. It is of interest in epidemiology studies to characterize the association of oxidative stress in...

  10. Effects of irradiation distance on supply of reactive oxygen species to the bottom of a Petri dish filled with liquid by an atmospheric O2/He plasma jet

    NASA Astrophysics Data System (ADS)

    Kawasaki, Toshiyuki; Kusumegi, Shota; Kudo, Akihiro; Sakanoshita, Tomohiro; Tsurumaru, Takuya; Sato, Akihiro; Uchida, Giichiro; Koga, Kazunori; Shiratani, Masaharu

    2016-05-01

    The impact of irradiation distances on plasma jet-induced specific effects on the supply of reactive oxygen species (ROS) to the bottom of a Petri dish filled with liquid was investigated using a KI-starch gel reagent that can be employed as a ROS indicator even in water. O3 exposure experiments without plasma irradiation were also performed to elucidate the specific effects of the plasma jet. Relative concentrations of ROS transported to the bottom were evaluated using absorbance measurements. The results indicated that ROS supply to the bottom is markedly enhanced by the plasma jet irradiation at shorter irradiation distances, whereas similar results could not be obtained for the O3 exposure. In these cases, the liquid mixing in the depth direction was also enhanced by the plasma jet irradiation only, and the supply of reactive atomic oxygen to the liquid surface was markedly increased as well.

  11. The interaction of atmospheric pressure plasma jets with cancer and normal cells: generation of intracellular reactive oxygen species and changes of the cell proliferation and cell cycle

    NASA Astrophysics Data System (ADS)

    Chung, Tae Hun; Joh, Hea Min; Kim, Sun Ja; Leem, Sun Hee

    2013-09-01

    The possibility of atmospheric pressure plasmas is emerging as a candidate in cancer therapy. The primary role is played by reactive oxygen species (ROS), UV photons, charged particles and electric fields. Among them, intracellular ROS induced by plasma are considered to be the key constituents that induce cellular changes and apoptosis. In this study, the effects of atmospheric pressure plasma jet on cancer cells (human lung carcinoma cells) and normal cells (embryonic kidney cells and bronchial epithelial cells) were investigated. The plasma treatment was performed under different working gases, applied voltages, gas flow rates, and with and without additive oxygen flow. Using a detection dye, we observed that plasma exposure leads to the increase of the intracellular ROS and that the intracellular ROS production can be controlled by plasma parameters. A significant ROS generation was induced by plasma exposure on cancer cells and the overproduction of ROS contributes to the reduced cell proliferation. Normal cells were observed to be less affected by the plasma-mediated ROS and cell proliferation was less changed. The plasma treatment also resulted in the alteration of the cell cycle that contributes to the induction of apoptosis in cancer cells. The selective effect on cancer and normal cells provides a promising prospect of cold plasma as cancer therapy. This work was supported by the National Research Foundation of Korea under Contract No. 2012R1A1A2002591 and 2012R1A1A3010213.

  12. Low temperature deposition of Ga{sub 2}O{sub 3} thin films using trimethylgallium and oxygen plasma

    SciTech Connect

    Donmez, Inci; Ozgit-Akgun, Cagla; Biyikli, Necmi

    2013-01-15

    Gallium oxide (Ga{sub 2}O{sub 3}) thin films were deposited by plasma-enhanced atomic layer deposition (ALD) using trimethylgallium as the gallium precursor and oxygen plasma as the oxidant. A wide ALD temperature window was observed from 100 to 400 Degree-Sign C, where deposition rate was constant at {approx}0.53 A/cycle. X-ray photoelectron spectroscopy survey scans indicated the presence of gallium, oxygen, and carbon elements with concentrations of {approx}36, {approx}51.8, and {approx}12.2 at. %, respectively. As-deposited films were amorphous; upon annealing at 900 Degree-Sign C under N{sub 2} atmosphere for 30 min, polycrystalline {beta}-Ga{sub 2}O{sub 3} phase with a monoclinic crystal structure was obtained. Refractive index and root mean square roughness of the annealed Ga{sub 2}O{sub 3} film were higher than those of the as-deposited due to crystallization.

  13. Formation of cerussite and hydrocerussite during adsorption of lead from aqueous solution on oxidized carbons by cold oxygen plasma

    NASA Astrophysics Data System (ADS)

    De Velasco Maldonado, Paola S.; Hernández-Montoya, Virginia; Concheso, A.; Montes-Morán, Miguel A.

    2016-11-01

    A new procedure of elimination of Pb2+ from aqueous solution using carbon adsorbents, in which high amounts of cerussite and hydrocerussite are deposited on the carbon surfaces, is reported. The procedure includes the preparation of carbons from selected lignocellulosic wastes (pecan nut shells and peach stones) by single carbonization and further oxidation with cold oxygen plasma. The materials prior and after the oxidation treatment were characterized using elemental analysis, FT-IR spectroscopy, SEM/EDX analysis, adsorption of N2 at -196 °C and X-ray photoelectron spectroscopy. The adsorption of Pb2+ was carried out in batch systems under constant agitation. The formation of cerussite and hydrocerussite on the spent carbon surfaces was confirmed by XRD, SEM/EDX and FT-IR. A Pb2+ removal mechanism is proposed in which a co-precipitation of lead nitrate and calcium carbonate would render the formation of the lead carbonates. In such mechanism, the occurrence of CaCO3 on the surface of the adsorbents plays a crucial role. The presence of calcium carbonate on the precursors is understood on the basis of the thermal evolution of calcium oxalate originally present in the biomass. The oxygen plasma treatment helps to expose the calcium carbonate nanocrystals thus improving dramatically the removal capacity of Pb2+. Accordingly, retention capacities as high as 63 mg of Pb2+ per gram of adsorbent have been attained.

  14. Effect of plasma jet diameter on the efficiency of reactive oxygen and nitrogen species generation in water

    NASA Astrophysics Data System (ADS)

    Oh, Jun-Seok; Kakuta, Maito; Furuta, Hiroshi; Akatsuka, Hiroshi; Hatta, Akimitsu

    2016-06-01

    The plasma jet generation of reactive oxygen and nitrogen species (RONS) in solution is important in biology, medicine, and disinfection. Studies using a wide variety of plasma jet devices have been carried out for this purpose, making it difficult to compare the performance between devices. In this study, we compared the efficiency of RONS generation in deionized (DI) water between 3.7-mm- and 800-µm-sized helium (He) plasma jets (hereafter mm-jet and µm-jet, respectively) at different treatment distances and times. The efficiency of RONS generation was determined by considering the total amount of RONS generated in DI water with respect to the input energy and gas consumption. We found that the mm-jet generated 20% more RONS in the DI water than the µm-jet at the optimized distance. However, when the input power and He gas consumption were taken into account, we discovered that the µm-jet was 5 times more efficient in generating RONS in the DI water. Under the parameters investigated in this study, the concentration of RONS continued to increase as a function of treatment time (up to 30 min). However treatment distance had a marked effect on the efficiency of RONS generation: treatment distances of 25 and 30 mm were optimal for the mm-jet and µm-jet, respectively. Our method of comparing the efficiency of RONS generation in solution between plasma jets could be used as a reference protocol for the development of efficient plasma jet sources for use in medicine, biology, and agriculture.

  15. Surface reaction mechanisms during ozone and oxygen plasma assisted atomic layer deposition of aluminum oxide.

    PubMed

    Rai, Vikrant R; Vandalon, Vincent; Agarwal, Sumit

    2010-09-07

    We have elucidated the reaction mechanism and the role of the reactive intermediates in the atomic layer deposition (ALD) of aluminum oxide from trimethyl aluminum in conjunction with O(3) and an O(2) plasma. In situ attenuated total reflection Fourier transform infrared spectroscopy data show that both -OH groups and carbonates are formed on the surface during the oxidation cycle. These carbonates, once formed on the surface, are stable to prolonged O(3) exposure in the same cycle. However, in the case of plasma-assisted ALD, the carbonates decompose upon prolonged O(2) plasma exposure via a series reaction kinetics of the type, A (CH(3)) --> B (carbonates) --> C (Al(2)O(3)). The ratio of -OH groups to carbonates on the surface strongly depends on the oxidizing agent, and also the duration of the oxidation cycle in plasma-assisted ALD. However, in both O(3) and O(2) plasma cycles, carbonates are a small fraction of the total number of reactive sites compared to the hydroxyl groups.

  16. Effect of substrate temperature on the structure of amorphous oxygenated hydrocarbon films grown with a pulsed supersonic methane plasma flow

    NASA Astrophysics Data System (ADS)

    Fedoseeva, Yu. V.; Pozdnyakov, G. A.; Okotrub, A. V.; Kanygin, M. A.; Nastaushev, Yu. V.; Vilkov, O. Y.; Bulusheva, L. G.

    2016-11-01

    Since amorphous oxygenated hydrocarbon (COxHy) films are promising engineering materials a study of the structure and composition of the films depending on the conditions of synthesis is important for controlling of their physicochemical properties. Here, we used the methods of scanning and transmission electron microscopy, X-ray photoelectron, near-edge X-ray absorption fine structure, Fourier transform infrared and Raman spectroscopy to reveal changes in the chemical connectivity of COxHy films grown on silicon substrates heated to 300, 500, and 700 °C using a supersonic flow of methane plasma. It was found that the COxHy films, deposited at 300 and 500 °C, were mainly composed of the sp2-hybridized carbon areas with various oxygen species. A rise of the substrate temperature caused an increase of the portion of tetrahedral carbon atoms as well as carboxyl and hydroxyl groups. With growth of the substrate temperature, the film thickness reduced monotonically from 400 to 180 nm, while the film adhesion improved substantially. The films, deposited at lower temperatures, showed high hydrophilicity due to porosity and presence of oxygenated groups both at the surface and in the bulk.

  17. Oxygen reduction reaction on highly-durable Pt/nanographene fuel cell catalyst synthesized employing in-liquid plasma

    NASA Astrophysics Data System (ADS)

    Amano, Tomoki; Kondo, Hiroki; Takeda, Keigo; Ishikawa, Kenji; Kano, Hiroyuki; Hiramatsu, Mineo; Sekine, Makoto; Hori, Masaru

    2016-09-01

    We recently have established ultrahigh-speed synthesis method of nanographene materials employing in-liquid plasma, and reported high durability of Pt/nanographene composites as a fuel cell catalyst. Crystallinity and domain size of nanographene materials were essential to their durability. However, their mechanism is not clarified yet. In this study, we investigated the oxygen reduction reaction using three-types of nanographene materials with different crystallinity and domain sizes, which were synthesized using ethanol, 1-propanol and 1-butanol, respectively. According to our previous studies, the nanographene material synthesized using the lower molecular weight alcohol has the higher crystallinity and larger domain size. Pt nanoparticles were supported on the nanographene surfaces by reducing 8 wt% H2PtCl6 diluted with H2O. Oxygen reduction current densities at a potential of 0.2 V vs. RHE were 5.43, 5.19 and 3.69 mA/cm2 for the samples synthesized using ethanol, 1-propanol and 1-butanol, respectively. This means that the higher crystallinity nanographene showed the larger oxygen reduction current density. The controls of crystallinity and domain size of nanographene materials are essential to not only their durability but also highly efficiency as catalyst electrodes.

  18. Rainbow trout (Oncorhynchus mykiss) exposed to oxygen supersaturation and handling stress: plasma cortisol and hepatic glutathione status.

    PubMed

    Ritola, O; Kiuru, T; Koponen, K; Mölsä, H; Hänninen, O; Lindström-Seppä, P

    1999-01-01

    Three groups of one summer old rainbow trout were exposed for 22 days either to normoxia (100%) or moderate oxygen supersaturation; 120% and 140%. After the exposure, all groups were transported for three hours in hyperoxic conditions (123% O2) thus simultaneously experiencing density and handling stress. The recovery of rainbow trout to multiple stressors was measured in normoxic conditions. Moderate oxygen supersaturation did not have any negative effects on growth, feed conversion and blood hematology measured over 22 days. On the other hand, the combined effects of the stressful environment in the fish farm and oxygen supersaturation resulted in a 3-fold increase in plasma cortisol levels in those with 100% and 120% O2 supersaturation and a 2-fold increase in the 140% supersaturation group. Furthermore, the stress response after transportation was lowest in the 140% group 24 hours after recovery but highest after 70 hours. Moderate hyperoxia or transportation stress did not change glutathione concentrations in liver indicating that routine sampling does not affect hepatic glutathione status. Our results indicate that moderate O2 supersaturation (<140%) could be considered as feasible in cultivation of rainbow trout since no harmful effects were found.

  19. Synergistic effect of EUV from the laser-sustained detonation plasma in a ground-based atomic oxygen simulation on fluorinated polymers

    SciTech Connect

    Tagawa, Masahito; Abe, Shingo; Kishida, Kazuhiro; Yokota, Kumiko; Okamoto, Akio

    2009-01-05

    The contribution of extreme ultraviolet (EUV) from a laser-sustained plasma on the mass loss phenomenon of fluorinated polymer in a ground-based laser-detonation atomic oxygen beam source was evaluated. The atomic oxygen beam and EUV from the oxygen plasma were separated by the high-speed chopper wheel installed in the beam source. The mass changes of the fluorinated polymer and polyimide were measured from the frequency shift of the quartz crystal microbalance during the beam exposures. It has been made clear that the fluorinated polymer erodes by EUV exposure alone. In contrast, no erosion was detected for polyimide by EUV alone. The atomic oxygen-induced erosion was measured for both materials even without EUV exposure. However, no strong synergistic effect was observed for a fluorinated polymer even under the simultaneous exposure condition of atomic oxygen and EUV. Similar results were observed even in simultaneous exposure of atomic oxygen (without EUV) and 172 nm vacuum ultraviolet (VUV) from an excimer lamp. These experiments suggest that the primary origin of the accelerated erosion of fluorinated polymer observed in a laser detonation atomic oxygen source is not the EUV from the laser-sustained plasma.

  20. Oxygen and nitrogen plasma etching of three-dimensional hydroxyapatite/chitosan scaffolds fabricated by additive manufacturing

    NASA Astrophysics Data System (ADS)

    Myung, Sung-Woon; Kim, Byung-Hoon

    2016-01-01

    Three-dimensional (3D) chitosan and hydroxyapatite (HAp)/chitosan (CH) scaffolds were fabricated by additive manufacturing, then their surfaces were etched with oxygen (O2) and nitrogen (N2) plasma. O2 and N2 plasma etching was performed to increase surface properties such as hydrophilicity, roughness, and surface chemistry on the scaffolds. After etching, hydroxyapatite was exposed on the surface of 3D HAp/CH scaffolds. The surface morphology and chemical properties were characterized by contact angle measurement, scanning electron microscopy, X-ray diffraction, and attenuated total reflection Fourier infrared spectroscopy. The cell viability of 3D chitosan scaffolds was examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The differentiation of preosteoblast cells was evaluated by alkaline phosphatase assay. The cell viability was improved by O2 and N2 plasma etching of 3D chitosan scaffolds. The present fabrication process for 3D scaffolds might be applied to a potential tool for preparing biocompatible scaffolds.

  1. Effects of surface modification by atmospheric oxygen dielectric barrier discharge plasma on PBO fibers and its composites

    NASA Astrophysics Data System (ADS)

    Liu, Zhe; Chen, Ping; Zhang, Xiaoliang; Yu, Qi; Ma, Keming; Ding, Zhenfeng

    2013-10-01

    In this paper, oxygen dielectric barrier discharge (oxy-DBD) plasma was employed to modify PBO fibers and enhance the interfacial adhesion of PBO fiber/bismaleimide composites. The interlaminar shear strength (ILSS) of the composites was improved greatly to 62.0 MPa with an increment of 41.2% at 30 W/cm3, 24 s. The SEM images of fracture morphology indicated that the failure place shifted from the interface to the matrix, and the water absorption decreased from 1.96 to 1.53%, the two results demonstrated the improved adhesive strength in other ways. In addition, the ILSS retention ratio of PBO/BMI composites after boiling in water were about 90%, confirming good humid resistance of the composites. The results obtained from XPS and AFM revealed that some polar groups were introduced onto PBO fibers and the surface morphology of PBO fibers was roughened. As a result, the wettability, reactivity and roughness of PBO fibers were all improved, they contributed to the improvement of the ILSS of the composites. The comparisons with air-DBD plasma showed that the chemical changes of PBO fibers were not alike because of different plasma gases.

  2. Chemical role of oxygen plasma in wafer bonding using borosilicate glasses

    NASA Astrophysics Data System (ADS)

    Hansen, D. M.; Albaugh, C. E.; Moran, P. D.; Kuech, T. F.

    2001-11-01

    Plasma-treated oxide layers are commonly used in wafer bonding applications. Borosilicate glass (BSG) layers deposited by low-pressure chemical vapor deposition treated with an O2 plasma in reactive ion etching mode for 5 min at 0.6 W/cm2 and rinsed with DI H2O readily bond to GaAs and Si. The chemical role of this prebonding treatment was investigated using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The peak intensities for both the Si-O and B-O absorbance bands decreased in intensity as a result of the plasma treatment is consistent with the uniform sputtering of 9.8 nm±0.8 nm of BSG. Polarization dependent ATR-FTIR revealed that the H2O/OH absorbance bands decreased in peak intensity with the OH groups being preferentially oriented perpendicular to the sample surface after the plasma treatment. The subsequent DI H2O rinse restores the water to the surface while removing B2O3 from the BSG layer. This prebonding treatment, therefore, results in a hydrophilic bond, but alters the composition of the BSG film at the bonded interface.

  3. Surface modification of high-performance polymeric fibers by an oxygen plasma. A comparative study of poly(p-phenylene terephthalamide) and poly(p-phenylene benzobisoxazole).

    PubMed

    Tamargo-Martínez, K; Martínez-Alonso, A; Villar-Rodil, S; Paredes, J I; Montes-Morán, M A; Tascón, J M D

    2011-06-17

    Poly(p-phenylene terephthalamide) (PPTA) and poly(p-phenylene benzobisoxazole) (PBO) fibers were exposed to an oxygen plasma under equivalent conditions. The resulting changes in the surface properties of PPTA and PBO were comparatively investigated using inverse gas chromatography (IGC) and atomic force microscopy (AFM). Both non-polar (n-alkanes) and polar probes of different acid-base characteristics were used in IGC adsorption experiments. Following plasma exposure, size-exclusion phenomena, probably associated to the formation of pores (nanoroughness), were detected with the largest n-alkanes (C(9) and C(10)). From the adsorption of polar probes, an increase in the number or strength of the acidic and basic sites present at the fiber surfaces following plasma treatment was detected. The effects of the oxygen plasma treatments were similar for PPTA and PBO. In both cases, oxygen plasma introduces polar groups onto the surfaces, involving an increase in the degree of surface nanoroughness. AFM measurements evidenced substantial changes in the surface morphology at the nanometer scale, especially after plasma exposure for a long time. For the PBO fibers, the outermost layer - contaminant substances - was removed thanks to the plasma treatment, which indicates that this agent had a surface cleaning effect.

  4. Etching high aspect ratio structures in silicon using sulfur hexafluoride/oxygen plasma

    NASA Astrophysics Data System (ADS)

    Belen, Rodolfo Jun

    Plasma etching of high aspect ratio structures in Si is an important step in manufacturing capacitors for memory devices and integrated components of microelectromechanical systems. In these applications, the goal is to etch deep features anisotropically with high etch rates and selectivities to the mask while maintaining good uniformity and reproducibility. This study investigates the etching of deep sub-half-micron diameter holes in Si using SF6/O 2 plasma. Etching experiments and plasma diagnostics are combined with modeling to gain a fundamental understanding of the etching and passivation kinetics and mechanism necessary in developing and scaling-up processes. Etching experiments are conducted in an inductively coupled plasma reactor with a planar coil. The substrate electrode is biased with a separate rf power supply to achieve independent control of the ion flux and energy. The effects of pressure, rf-bias and SF6-to-O2 ratio in the feed gas on the etch rate, selectivity and feature profile shape are studied using Si wafers patterned with 0.35 mum-diameter holes in a SiO2 mask. Visualization of profiles using scanning electron microscopy is complemented by plasma diagnostics such as mass spectrometry and actinometry. Simultaneous with experiments, reactor-scale and feature-scale models are developed to quantify the etching and passivation kinetics and identify the important kinetic parameters that affect feature profile evolution. Information from plasma diagnostics and previously published data are used to reduce the degrees of freedom in the model. Experiments are designed to directly measure kinetic parameters such as the chemical etch rate constant and the incidence angle dependence of the etching yield. Experimentally inaccessible parameters such as the sticking coefficients, etching yield and ion scattering parameters are determined through feature profile simulation. The key internal plasma parameters that affect profile evolution are the F-to-O and F

  5. The Role of Oxygen Partial Pressure in Controlling the Phase Composition of La1- x Sr x Co y Fe1- y O3- δ Oxygen Transport Membranes Manufactured by Means of Plasma Spray-Physical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Marcano, D.; Mauer, G.; Sohn, Y. J.; Vaßen, R.; Garcia-Fayos, J.; Serra, J. M.

    2016-04-01

    La0.58Sr0.4Co0.2Fe0.8O3 - δ (LSCF) deposited on a metallic porous support by plasma spray-physical vapor deposition is a promising candidate for oxygen-permeation membranes. Ionic transport properties are regarded to depend on the fraction of perovskite phase present in the membrane. However, during processing, the LSCF powder decomposes into perovskite and secondary phases. In order to improve the ionic transport properties of the membranes, spraying was carried out at different oxygen partial pressures p(O2). It was found that coatings deposited at lower and higher oxygen partial pressures consist of 70% cubic/26% rhombohedral and 61% cubic/35% rhombohedral perovskite phases, respectively. During annealing, the formation of non-perovskite phases is driven by oxygen non-stoichiometry. The amount of oxygen added during spraying can be used to increase the perovskite phase fraction and suppress the formation of non-perovskite phases.

  6. Monomeric Immunoglobulin A from Plasma Inhibits Human Th17 Responses In Vitro Independent of FcαRI and DC-SIGN

    PubMed Central

    Saha, Chaitrali; Das, Mrinmoy; Patil, Veerupaxagouda; Stephen-Victor, Emmanuel; Sharma, Meenu; Wymann, Sandra; Jordi, Monika; Vonarburg, Cédric; Kaveri, Srini V.; Bayry, Jagadeesh

    2017-01-01

    Circulating immunoglobulins including immunoglobulin G (IgG) and IgM play a critical role in the immune homeostasis by modulating functions of immune cells. These functions are mediated in part by natural antibodies. However, despite being second most abundant antibody in the circulation, the immunoregulatory function of IgA is relatively unexplored. As Th17 cells are the key mediators of a variety of autoimmune, inflammatory, and allergic diseases, we investigated the ability of monomeric IgA (mIgA) isolated from pooled plasma of healthy donors to modulate human Th17 cells. We show that mIgA inhibits differentiation and amplification of human Th17 cells and the production of their effector cytokine IL-17A. mIgA also suppresses IFN-γ responses under these experimental conditions. Suppressive effect of mIgA on Th17 responses is associated with reciprocal expansion of FoxP3-positive regulatory T cells. The effect of mIgA on Th17 cells is dependent on F(ab′)2 fragments and independent of FcαRI (CD89) and DC-SIGN. Mechanistically, the modulatory effect of mIgA on Th17 cells implicates suppression of phosphorylation of signal transducer and activator of transcription 3. Furthermore, mIgA binds to CD4+ T cells and recognizes in a dose-dependent manner the receptors for cytokines (IL-6Rα and IL-1RI) that mediate Th17 responses. Our findings thus reveal novel anti-inflammatory functions of IgA and suggest potential therapeutic utility of mIgA in autoimmune and inflammatory diseases that implicate Th17 cells. PMID:28352269

  7. Surface recombination of oxygen atoms in O2 plasma at increased pressure: II. Vibrational temperature and surface production of ozone

    NASA Astrophysics Data System (ADS)

    Lopaev, D. V.; Malykhin, E. M.; Zyryanov, S. M.

    2011-01-01

    Ozone production in an oxygen glow discharge in a quartz tube was studied in the pressure range of 10-50 Torr. The O3 density distribution along the tube diameter was measured by UV absorption spectroscopy, and ozone vibrational temperature TV was found comparing the calculated ab initio absorption spectra with the experimental ones. It has been shown that the O3 production mainly occurs on a tube surface whereas ozone is lost in the tube centre where in contrast the electron and oxygen atom densities are maximal. Two models were used to analyse the obtained results. The first one is a kinetic 1D model for the processes occurring near the tube walls with the participation of the main particles: O(3P), O2, O2(1Δg) and O3 molecules in different vibrational states. The agreement of O3 and O(3P) density profiles and TV calculated in the model with observed ones was reached by varying the single model parameter—ozone production probability (\\gamma_{O_{3}}) on the quartz tube surface on the assumption that O3 production occurs mainly in the surface recombination of physisorbed O(3P) and O2. The phenomenological model of the surface processes with the participation of oxygen atoms and molecules including singlet oxygen molecules was also considered to analyse \\gamma_{O_{3}} data obtained in the kinetic model. A good agreement between the experimental data and the data of both models—the kinetic 1D model and the phenomenological surface model—was obtained in the full range of the studied conditions that allowed consideration of the ozone surface production mechanism in more detail. The important role of singlet oxygen in ozone surface production was shown. The O3 surface production rate directly depends on the density of physisorbed oxygen atoms and molecules and can be high with increasing pressure and energy inputted into plasma while simultaneously keeping the surface temperature low enough. Using the special discharge cell design, such an approach opens up the

  8. Influence of the residual oxygen in the plasma immersion ion implantation (PI3) processing of materials

    NASA Astrophysics Data System (ADS)

    Ueda, M.; Silva, A. R.; Mello, Carina B.; Silva, G.; Reuther, H.; Oliveira, V. S.

    2011-12-01

    In this work, we investigated the effects of the contaminants present in the vacuum chamber of the PI3 system, in particular, the residual oxygen, which results in the formation of the oxide compounds on the surface and hence is responsible for the high implantation energies required to achieve reasonably thick treated layers. We used a mass spectrometer (RGA) with a quadruple filter to verify the composition of the residual vacuum and pressure of the elements present in the chamber. Initially we found a high proportion of residual oxygen in a vacuum with a pressure of 1 × 10 -3 Pa. Minimizing the residual oxygen percentage in about 80%, by efficient cleaning of the chamber walls and by improving the gas feeding process, we mitigated the formation of oxides during the PI3 process. Therefore we achieved a highly efficient PI3 processing obtaining implanted layers reaching about 50 nm, even in cases such as an aluminum alloy, where is very difficult to nitrogen implant at low energies. We performed nitrogen PI3 treatment of SS304 and Al7075 using pulses of only 3 kV and 15 × 10 -6 s at 1 kHz with an operating pressure of 1 Pa.

  9. The Role of Helium Metastable States in Radio-Frequency Helium-Oxygen Atmospheric Pressure Plasma Jets: Measurement and Numerical Simulation

    NASA Astrophysics Data System (ADS)

    Niemi, Kari; Waskoenig, Jochen; Sadeghi, Nader; Gans, Timo; O'Connell, Deborah

    2011-10-01

    Absolute densities of metastable He atoms were measured line-of sight integrated along the plasma channel of a capacitively-coupled radio-frequency driven atmospheric pressure plasma jet operated in helium oxygen mixtures by tunable diode-laser absorption spectroscopy. Dependencies of the He metastable density with oxygen admixtures up to 1 percent were investigated. Results are compared to a 1-d numerical simulation, which includes a semi-kinetical treatment of the electron dynamics and the complex plasma chemistry (20 species, 184 reactions), and very good agreement is found. The main formation mechanisms for the helium metastables are identified and analyzed, including their pronounced spatio-temporal dynamics. Penning ionization through helium metastables is found to be significant for plasma sustainment, while it is revealed that helium metastables are not an important energy carrying species into the jet effluent and therefore will not play a direct role in remote surface treatments.

  10. Two-dimensional concentration distribution of reactive oxygen species transported through a tissue phantom by atmospheric-pressure plasma-jet irradiation

    NASA Astrophysics Data System (ADS)

    Kawasaki, Toshiyuki; Sato, Akihiro; Kusumegi, Shota; Kudo, Akihiro; Sakanoshita, Tomohiro; Tsurumaru, Takuya; Uchida, Giichiro; Koga, Kazunori; Shiratani, Masaharu

    2016-07-01

    The two-dimensional concentration distribution of reactive oxygen species (ROSs) transported through an agarose-film tissue phantom by atmospheric-pressure plasma-jet irradiation is visualized using a KI-starch gel reagent. Oxygen addition to helium enhances ROS transportation through the film. A radial ROS distribution pattern at the plasma-irradiated film surface changes into a doughnut-shaped pattern after passing through the film. The ROS transportation speed is 0.14-0.2 mm/min. We suggest that there are two types of ROS transportation pathways in the plasma-irradiated film: linear and circular. The majority of ROSs are transported through the circular pathway. ROS concentration distributions changed markedly with irradiation distance. Diffusive ROS transportation due to a concentration gradient is negligible in plasma-irradiated films.

  11. Surface modification of starch based biomaterials by oxygen plasma or UV-irradiation.

    PubMed

    Pashkuleva, Iva; Marques, Alexandra P; Vaz, Filipe; Reis, Rui L

    2010-01-01

    Radiation is widely used in biomaterials science for surface modification and sterilization. Herein, we describe the use of plasma and UV-irradiation to improve the biocompatibility of different starch-based blends in terms of cell adhesion and proliferation. Physical and chemical changes, introduced by the used methods, were evaluated by complementary techniques for surface analysis such as scanning electron microscopy, atomic force microscopy, contact angle analysis and X-ray photoelectron spectroscopy. The effect of the changed surface properties on the adhesion of osteoblast-like cells was studied by a direct contact assay. Generally, both treatments resulted in higher number of cells adhered to the modified surfaces. The importance of the improved biocompatibility resulting from the irradiation methods is further supported by the knowledge that both UV and plasma treatments can be used as cost-effective methods for sterilization of biomedical materials and devices.

  12. Element- and charge-state-resolved ion energies in the cathodic arc plasma from composite AlCr cathodes in argon, nitrogen and oxygen atmospheres.

    PubMed

    Franz, Robert; Polcik, Peter; Anders, André

    2015-06-25

    The energy distribution functions of ions in the cathodic arc plasma using composite AlCr cathodes were measured as a function of the background gas pressure in the range 0.5 to 3.5 Pa for different cathode compositions and gas atmospheres. The most abundant aluminium ions were Al(+) regardless of the background gas species, whereas Cr(2+) ions were dominating in Ar and N2 and Cr(+) in O2 atmospheres. The energy distributions of the aluminium and chromium ions typically consisted of a high-energy fraction due to acceleration in the expanding plasma plume from the cathode spot and thermalised ions that were subjected to collisions in the plasma cloud. The fraction of the latter increased with increasing background gas pressure. Atomic nitrogen and oxygen ions showed similar energy distributions as the aluminium and chromium ions, whereas the argon and molecular nitrogen and oxygen ions were formed at greater distance from the cathode spot and thus less subject to accelerating gradients. In addition to the positively charged metal and gas ions, negatively charged oxygen and oxygen-containing ions were observed in O2 atmosphere. The obtained results are intended to provide a comprehensive overview of the ion energies and charge states in the arc plasma of AlCr composite cathodes in different gas atmospheres as such plasmas are frequently used to deposit thin films and coatings.

  13. Element- and charge-state-resolved ion energies in the cathodic arc plasma from composite AlCr cathodes in argon, nitrogen and oxygen atmospheres

    PubMed Central

    Franz, Robert; Polcik, Peter; Anders, André

    2015-01-01

    The energy distribution functions of ions in the cathodic arc plasma using composite AlCr cathodes were measured as a function of the background gas pressure in the range 0.5 to 3.5 Pa for different cathode compositions and gas atmospheres. The most abundant aluminium ions were Al+ regardless of the background gas species, whereas Cr2+ ions were dominating in Ar and N2 and Cr+ in O2 atmospheres. The energy distributions of the aluminium and chromium ions typically consisted of a high-energy fraction due to acceleration in the expanding plasma plume from the cathode spot and thermalised ions that were subjected to collisions in the plasma cloud. The fraction of the latter increased with increasing background gas pressure. Atomic nitrogen and oxygen ions showed similar energy distributions as the aluminium and chromium ions, whereas the argon and molecular nitrogen and oxygen ions were formed at greater distance from the cathode spot and thus less subject to accelerating gradients. In addition to the positively charged metal and gas ions, negatively charged oxygen and oxygen-containing ions were observed in O2 atmosphere. The obtained results are intended to provide a comprehensive overview of the ion energies and charge states in the arc plasma of AlCr composite cathodes in different gas atmospheres as such plasmas are frequently used to deposit thin films and coatings. PMID:26120236

  14. Study of short atmospheric pressure dc glow microdischarge in air

    NASA Astrophysics Data System (ADS)

    Kudryavtsev, Anatoly; Bogdanov, Eugene; Chirtsov, Alexander; Emelin, Sergey

    2011-10-01

    The results of experiments and simulations of short (without positive column) atmospheric pressure dc glow discharge in air are presented. We used metal steel electrodes with a gap of 5-100 microns. The experimental voltage-current characteristic's (VAC) have a constant or slightly increasing form at low gap. The most stable microdischarges were burning with a flat cathode and rounded anode, when the length of the discharge is automatically established near the minimum of the Paschen curve by changing their binding on the anode. In this case microdischarge was stable and it had growing VAC. For simulations we used 2D fluid model with kinetic description of electrons. We solved the balance equations for the vibrationally- and the electronically-excited states of a nitrogen and oxygen molecules; nitrogen and oxygen atoms; ozone molecule; and different nitrogen and oxygen ions with different plasmochemical reactions between them. Simulations predicted the main regions of the dc glow discharges including cathode and anode sheath and plasma of negative glow, Faraday dark space and transition region. Gas heating plays an important role in shaping the discharge profiles. The results of experiments and simulations of short (without positive column) atmospheric pressure dc glow discharge in air are presented. We used metal steel electrodes with a gap of 5-100 microns. The experimental voltage-current characteristic's (VAC) have a constant or slightly increasing form at low gap. The most stable microdischarges were burning with a flat cathode and rounded anode, when the length of the discharge is automatically established near the minimum of the Paschen curve by changing their binding on the anode. In this case microdischarge was stable and it had growing VAC. For simulations we used 2D fluid model with kinetic description of electrons. We solved the balance equations for the vibrationally- and the electronically-excited states of a nitrogen and oxygen molecules; nitrogen

  15. Excitation of Josephson Plasma Resonance in BISMUTH(2) STRONTIUM(2) Calcium COPPER(2) OXYGEN(8+DELTA)

    NASA Astrophysics Data System (ADS)

    Tsui, Ophelia Kwan Chui

    A novel magnetic resonance is observed in Bi_2Sr_2CaCu_2O_{8+ delta} single crystals exposed to microwave radiation (26 to 95 GHz) in the presence of a magnetic field. The resonance exhibits unconventional field and temperature dependence. At a fixed temperature below the melting transition of the vortex solid, T_ {m}(B), the resonance frequency decreases with the applied field and displays a power-law dependence, viz. omega~ B^{-mu }. The exponent was found to be 0.8 within 10% across all samples and temperatures studied. However, when the temperature is increased above T_ {m}(B), mu becomes sample dependent and is equal to 0.64 and 1.08 for the two samples studied. At fixed microwave frequencies, the resonance field, B_0 increases exponentially with temperature to a maximum at T_{m }(B) and decreases slowly with temperature above. We attribute the resonance to Josephson plasma oscillations excited along the sample c-axis. The model explains many features of the experiment. Recently, Bulaevskii et al. proposed an explanation for the field dependence of the Josephson plasma frequency. By assuming that disorder in vortex pancakes is caused by strong pinning at low temperatures, the authors obtained the power-law dependence of omega on B, which agrees with the experiment. Rotating the microwave E-field, { bf E}_{rf} relatively to the sample, we find maximum resonance absorption when {bf E}_{rf} has the maximum projection along the sample c-axis, and minimum when there is none. This identification of {bf E}_{rf} parallel to the sample c-axis as the one responsible for the resonance, supports the Josephson plasma hypothesis. The strongest evidence for the Josephson plasma model is obtained by tilting the magnetic field close to alignment with the ab-plane of the crystal. In that case, an unusual re-entrant cusp in B_0 is observed when the tilt angle is in the range -5.5^circ to 5.5^circ. This is consistent with Bulaevskii et al.'s calculation. They propose that pancake

  16. In Vitro Corrosion Behavior and Apatite Growth of Oxygen Plasma Ion Implanted Titanium Alloy β-21S

    NASA Astrophysics Data System (ADS)

    Anandan, C.; Mohan, L.

    2013-11-01

    Titanium alloy beta 21S was implanted with oxygen ions by plasma immersion ion implantation. The implanted surface was characterized by micro-Raman, XPS and FESEM before and after potentiodynamic polarization and electrochemical impedance studies in Hanks' solution and after incubation in Hanks' solution for 1 and 7 days. The investigations show that the native oxide on the sample is replaced by a compact oxide by implantation and the new oxide layer behaves in a different way in that a two layer model is required to explain the observed electrochemical impedance data. The analysis of layers formed in the electrochemical studies and after incubation in Hanks' solution by XPS and FESEM shows that the new oxide surface is capable of inducing apatite growth on it.

  17. The fabrication of diversiform nanostructure forests based on residue nanomasks synthesized by oxygen plasma removal of photoresist

    NASA Astrophysics Data System (ADS)

    Mao, Haiyang; Wu, Di; Wu, Wengang; Xu, Jun; Hao, Yilong

    2009-11-01

    A simple lithography-free approach for fabricating diversiform nanostructure forests is presented. The key technique of the approach is that randomly distributed nanoscale residues can be synthesized on substrates simply by removing photoresist with oxygen plasma bombardment. These nanoresidues can function as masks in the subsequent etching process for nanopillars. By further spacer and then deep etching processes, a variety of forests composed of regular, tulip-like or hollow-head nanopillars as well as nanoneedles are successfully achieved in different etching conditions. The pillars have diameters of 30-200 nm and heights of 400 nm-3 µm. The needles reach several microns in height, with their tips less than 10 nm in diameter. Moreover, microstructures containing these nanostructure forests, such as surface microchannels, have also been fabricated. This approach is compatible with conventional micro/nano-electromechanical system (MEMS/NEMS) fabrication.

  18. A hybrid plasma technology life support system for the generation of oxygen on Mars: Considerations on materials and geometry

    NASA Astrophysics Data System (ADS)

    Gruenwald, J.

    2016-06-01

    As there is a growing interest in conducting human missions to Mars, the need for suitable life support systems becomes more and more important. The reliability of such systems has to increase with the duration of manned missions. Furthermore the maintenance requirements have to be low in order to ensure their efficient use over a long period of time. A proposal for a hybrid life support system that is based on plasma technology for the creation of oxygen from the dissociation of carbon dioxide is given in this paper. The main focus lies on geometrical considerations regarding the optimal shape of the main reactor chamber as well as on suitable materials, which are most promising for the construction of such a system.

  19. Investigation into the effect of plasma pretreatment on the adhesion of parylene to various substrates

    NASA Technical Reports Server (NTRS)

    Riley, T.; Mahuson, T. C.; Seibert, K.

    1979-01-01

    A procedure is described for using argon and oxygen plasmas to promote adhesion of parylene coatings upon many difficult-to-bond substrates. Substrates investigated were gold, nickel, kovar, teflon (FEP), kapton, silicon, tantalum, titanium, and tungsten. Without plasma treatment, 180 deg peel tests yield a few g/cm (oz/in) strengths. With dc plasma treatment in the deposition chamber, followed by coating, peel strengths are increased by one to two orders of magnitude.

  20. Comprehensive study of the conditions for obtaining hydrogenated amorphous erbium- and oxygen-doped silicon suboxide films, a-SiO{sub x}:H Left-Pointing-Angle-Bracket Er,O Right-Pointing-Angle-Bracket , by dc-magnetron deposition

    SciTech Connect

    Undalov, Yu. K. Terukov, E. I.; Gusev, O. B.; Lebedev, V. M.; Trapeznikova, I. N.

    2011-12-15

    The results of a comprehensive study of the conditions for growing a-SiO{sub x}:H Left-Pointing-Angle-Bracket Er,O Right-Pointing-Angle-Bracket films are presented. The effect of the composition of various erbium-containing targets (a-SiO{sub x}:H , ErO{sub x}, Er{sub 2}SiO{sub 5}, Er{sub 2}O{sub 3}, and Er), substrate temperature, and annealing temperatures in argon, air, and under conditions of SiH{sub 4} + Ar + O{sub 2} plasma glow is studied. In order to obtain a-SiO{sub x}:H Left-Pointing-Angle-Bracket Er,O Right-Pointing-Angle-Bracket films with the highest photoluminescence intensity of erbium ions, it is recommended for the following technological conditions to be used: the substrate holder should be insulated from dc-magnetron electrodes and the working gas mixture should include silane, argon, and oxygen. Single-crystal silicon and metal erbium should be used as targets. The erbium target should be placed only in the Si-target erosion zone.

  1. Hampering Effect of Cholesterol on the Permeation of Reactive Oxygen Species through Phospholipids Bilayer: Possible Explanation for Plasma Cancer Selectivity

    NASA Astrophysics Data System (ADS)

    van der Paal, Jonas; Verheyen, Claudia; Neyts, Erik C.; Bogaerts, Annemie

    2017-01-01

    In recent years, the ability of cold atmospheric pressure plasmas (CAPS) to selectively induce cell death in cancer cells has been widely established. This selectivity has been assigned to the reactive oxygen and nitrogen species (RONS) created in CAPs. To provide new insights in the search for an explanation for the observed selectivity, we calculate the transfer free energy of multiple ROS across membranes containing a varying amount of cholesterol. The cholesterol fraction is investigated as a selectivity parameter because membranes of cancer cells are known to contain lower fractions of cholesterol compared to healthy cells. We find that cholesterol has a significant effect on the permeation of reactive species across a membrane. Indeed, depending on the specific reactive species, an increasing cholesterol fraction can lead to (i) an increase of the transfer free energy barrier height and width, (ii) the formation of a local free energy minimum in the center of the membrane and (iii) the creation of extra free energy barriers due to the bulky sterol rings. In the context of plasma oncology, these observations suggest that the increased ingress of RONS in cancer cells can be explained by the decreased cholesterol fraction of their cell membrane.

  2. Cold Oxygen Plasma Treatments for the Improvement of the Physicochemical and Biodegradable Properties of Polylactic Acid Films for Food Packaging.

    PubMed

    Song, Ah Young; Oh, Yoon Ah; Roh, Si Hyeon; Kim, Ji Hyeon; Min, Sea C

    2016-01-01

    The effects of cold plasma (CP) treatment on the physicochemical and biodegradable properties of polylactic acid (PLA) films were studied. The PLA films were exposed to CP for 40 min at 900 W and 667 Pa using oxygen as the plasma-forming gas. The tensile, optical, and dynamic mechanical thermal properties, surface morphology, printability, water contact angle, chemical structure, weight change, and biodegradability properties of the films were evaluated during storage for up to 56 d. The tensile and optical properties of the PLA films were not significantly affected by CP treatment (CPT; P > 0.05). The surface roughness and water contact angle of PLA films increased by CPT and further increased during storage for 56 d. The printability of the PLA films increased following CPT and remained stable throughout the storage period. CP-induced hydrophilicity was also sustained during the storage period. The PLA films lost 1.9% of their weight after CPT, but recovered 99.5% of this loss after 14 d in storage. Photodegradation, thermal, and microbial biodegradable properties of the films were significantly improved by CPT (P < 0.05). Accelerated biodegradation of CP-treated PLA sachets with and without cheese was observed in compost. These results demonstrate the potential of CPT for modifying the stiffness, water contact angle, and chemical structure of PLA films and improving the printability and biodegradability of the films for food packaging.

  3. Hemocompatibility and oxygenation performance of polysulfone membranes grafted with polyethylene glycol and heparin by plasma-induced surface modification.

    PubMed

    Wang, Weiping; Zheng, Zhi; Huang, Xin; Fan, Wenling; Yu, Wenkui; Zhang, Zhibing; Li, Lei; Mao, Chun

    2016-05-14

    Polyethylene glycol (PEG) and heparin (Hep) were grafted onto polysulfone (PSF) membrane by plasma-induced surface modification to prepare PSF-PEG-Hep membranes used for artificial lung. The effects of plasma treatment parameters, including power, gas type, gas flow rate, and treatment time, were investigated, and different PEG chains were bonded covalently onto the surface in the postplasma grafting process. Membrane surfaces were characterized by water contact angle, PEG grafting degree, attenuated total reflectance-Fourier transform infrared spectroscopy, ultraviolet-visible spectrophotometry, X-ray photoelectron spectroscopy, critical water permeability pressure, and scanning electron microscopy. Protein adsorption, platelet adhesion, and coagulation tests showed significant improvement in the hemocompatibility of PSF-PEG-Hep membranes compared to pristine PSF membrane. Gas exchange tests through PSF-PEG6000-Hep membrane showed that when the flow rate of porcine blood reached 5.0 L/min, the permeation fluxes of O2 and CO2 reached 192.6 and 166.9 mL/min, respectively, which were close to the gas exchange capacity of a commercial membrane oxygenator. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2016.

  4. Plasmonic gold helices for the visible range fabricated by oxygen plasma purification of electron beam induced deposits

    NASA Astrophysics Data System (ADS)

    Haverkamp, Caspar; Höflich, Katja; Jäckle, Sara; Manzoni, Anna; Christiansen, Silke

    2017-02-01

    Electron beam induced deposition (EBID) currently provides the only direct writing technique for truly three-dimensional nanostructures with geometrical features below 50 nm. Unfortunately, the depositions from metal-organic precursors suffer from a substantial carbon content. This hinders many applications, especially in plasmonics where the metallic nature of the geometric surfaces is mandatory. To overcome this problem a post-deposition treatment with oxygen plasma at room temperature was investigated for the purification of gold containing EBID structures. Upon plasma treatment, the structures experience a shrinkage in diameter of about 18 nm but entirely keep their initial shape. The proposed purification step results in a core-shell structure with the core consisting of mainly unaffected EBID material and a gold shell of about 20 nm in thickness. These purified structures are plasmonically active in the visible wavelength range as shown by dark field optical microscopy on helical nanostructures. Most notably, electromagnetic modeling of the corresponding scattering spectra verified that the thickness and quality of the resulting gold shell ensures an optical response equal to that of pure gold nanostructures.

  5. Two-photon absorption laser induced fluorescence measurement of atomic oxygen density in an air atmospheric pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Conway, Jim; Gogna, Gurusharan; Daniels, Stephen

    2016-09-01

    Two-photon Absorption Laser Induced Fluorescence (TALIF) is used to measure atomic oxygen number density [O] in an air Atmospheric Pressure Plasma Jet (APPJ). A novel technique based on photolysis of O2 is used to calibrate the TALIF system ensuring the same species (O) is probed during calibration and measurement. As a result, laser intensity can be increased outside the TALIF quadratic laser power region without affecting calibration reliability as any high intensity saturation effects will be identical for calibration and experiment. Higher laser intensity gives stronger TALIF signals helping overcome weak TALIF signals often experienced at atmospheric pressure due to collisional quenching. O2 photo-dissociation and two-photon excitation of the resulting [O] are both achieved within the same laser pulse. The photolysis [O] is spatially non-uniform and time varying. To allow valid comparison with [O] in a plasma, spatial and temporal correction factors are required. Knowledge of the laser pulse intensity I0(t), and wavelength allows correction factors to be found using a rate equation model. The air flow into the jet was fixed and the RF power coupled into the system varied. The resulting [O] was found to increase with RF power.

  6. Plasmonic gold helices for the visible range fabricated by oxygen plasma purification of electron beam induced deposits.

    PubMed

    Haverkamp, Caspar; Höflich, Katja; Jäckle, Sara; Manzoni, Anna; Christiansen, Silke

    2017-02-03

    Electron beam induced deposition (EBID) currently provides the only direct writing technique for truly three-dimensional nanostructures with geometrical features below 50 nm. Unfortunately, the depositions from metal-organic precursors suffer from a substantial carbon content. This hinders many applications, especially in plasmonics where the metallic nature of the geometric surfaces is mandatory. To overcome this problem a post-deposition treatment with oxygen plasma at room temperature was investigated for the purification of gold containing EBID structures. Upon plasma treatment, the structures experience a shrinkage in diameter of about 18 nm but entirely keep their initial shape. The proposed purification step results in a core-shell structure with the core consisting of mainly unaffected EBID material and a gold shell of about 20 nm in thickness. These purified structures are plasmonically active in the visible wavelength range as shown by dark field optical microscopy on helical nanostructures. Most notably, electromagnetic modeling of the corresponding scattering spectra verified that the thickness and quality of the resulting gold shell ensures an optical response equal to that of pure gold nanostructures.

  7. Hampering Effect of Cholesterol on the Permeation of Reactive Oxygen Species through Phospholipids Bilayer: Possible Explanation for Plasma Cancer Selectivity

    PubMed Central

    Van der Paal, Jonas; Verheyen, Claudia; Neyts, Erik C.; Bogaerts, Annemie

    2017-01-01

    In recent years, the ability of cold atmospheric pressure plasmas (CAPS) to selectively induce cell death in cancer cells has been widely established. This selectivity has been assigned to the reactive oxygen and nitrogen species (RONS) created in CAPs. To provide new insights in the search for an explanation for the observed selectivity, we calculate the transfer free energy of multiple ROS across membranes containing a varying amount of cholesterol. The cholesterol fraction is investigated as a selectivity parameter because membranes of cancer cells are known to contain lower fractions of cholesterol compared to healthy cells. We find that cholesterol has a significant effect on the permeation of reactive species across a membrane. Indeed, depending on the specific reactive species, an increasing cholesterol fraction can lead to (i) an increase of the transfer free energy barrier height and width, (ii) the formation of a local free energy minimum in the center of the membrane and (iii) the creation of extra free energy barriers due to the bulky sterol rings. In the context of plasma oncology, these observations suggest that the increased ingress of RONS in cancer cells can be explained by the decreased cholesterol fraction of their cell membrane. PMID:28059085

  8. Prostaglandin D2 synthase: Apoptotic factor in alzheimer plasma, inducer of reactive oxygen species, inflammatory cytokines and dialysis dementia

    PubMed Central

    Maesaka, John K.; Sodam, Bali; Palaia, Thomas; Ragolia, Louis; Batuman, Vecihi; Miyawaki, Nobuyuki; Shastry, Shubha; Youmans, Steven; El-Sabban, Marwan

    2013-01-01

    Background: Apoptosis, reactive oxygen species (ROS) and inflammatory cytokines have all been implicated in the development of Alzheimer’s disease (AD). Objectives: The present study identifies the apoptotic factor that was responsible for the fourfold increase in apoptotic rates that we previously noted when pig proximal tubule, LLC-PK1, cells were exposed to AD plasma as compared to plasma from normal controls and multi-infarct dementia. Patients and Methods: The apoptotic factor was isolated from AD urine and identified as lipocalin-type prostaglandin D2 synthase (L-PGDS). L-PGDS was found to be the major apoptotic factor in AD plasma as determined by inhibition of apoptosis approximating control levels by the cyclo-oxygenase (COX) 2 inhibitor, NS398, and the antibody to L-PGDS. Blood levels of L-PGDS, however, were not elevated in AD. We now demonstrate a receptor-mediated uptake of L-PGDS in PC12 neuronal cells that was time, dose and temperature-dependent and was saturable by competition with cold L-PGDS and albumin. Further proof of this endocytosis was provided by an electron microscopic study of gold labeled L-PGDS and immunofluorescence with Alexa-labeled L-PGDS. Results: The recombinant L-PGDS and wild type (WT) L-PGDS increased ROS but only the WTL-PGDS increased IL6 and TNFα, suggesting that differences in glycosylation of L-PGDS in AD was responsible for this discrepancy. Conclusions: These data collectively suggest that L-PGDS might play an important role in the development of dementia in patients on dialysis and of AD. PMID:24475446

  9. Low Pressure Radio-Frequency Oxygen Plasma Induced Oxidation of Titanium – Surface Characteristics and Biological Effects

    PubMed Central

    Tseng, Wan-Yu; Hsu, Sheng-Hao; Huang, Chieh-Hsiun; Tu, Yu-Chieh; Tseng, Shao-Chin; Chen, Hsuen-Li; Chen, Min-Huey; Su, Wei-Fang; Lin, Li-Deh

    2013-01-01

    Objective This research was designed to investigate the effects of low pressure radio-frequency (RF) oxygen plasma treatment (OPT) on the surface of commercially pure titanium (CP-Ti) and Ti6Al4V. Surface topography, elemental composition, water contact angle, cell viability, and cell morphology were surveyed to evaluate the biocompatibility of titanium samples with different lengths of OP treating time. Materials and Methods CP-Ti and Ti6Al4V discs were both classified into 4 groups: untreated, treated with OP generated by using oxygen (99.98%) for 5, 10, and 30 min, respectively. After OPT on CP-Ti and Ti6Al4V samples, scanning probe microscopy, X-ray photoelectron spectrometry (XPS), and contact angle tests were conducted to determine the surface topography, elemental composition and hydrophilicity, respectively. The change of surface morphology was further studied using sputtered titanium on silicon wafers. 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and F-actin immunofluorescence stain were performed to investigate the viability and spreading behavior of cultivated MG-63 cells on the samples. Results The surface roughness was most prominent after 5 min OPT in both CP-Ti and Ti6Al4V, and the surface morphology of sputtered Ti sharpened after the 5 min treatment. From the XPS results, the intensity of Ti°, Ti2+, and Ti3+ of the samples’ surface decreased indicating the oxidation of titanium after OPT. The water contact angles of both CP-Ti and Ti6Al4V were increased after 5 min OPT. The results of MTT assay demonstrated MG-63 cells proliferated best on the 5 min OP treated titanium sample. The F-actin immunofluorescence stain revealed the cultivated cell number of 5 min treated CP-Ti/Ti6Al4V was greater than other groups and most of the cultivated cells were spindle-shaped. Conclusions Low pressure RF oxygen plasma modified both the composition and the morphology of titanium samples’ surface. The CP-Ti/Ti6Al4V treated with 5 min

  10. Fast Degradation for High Activity: Oxygen- and Nitrogen-Functionalised Carbon Nanotubes in Solid-Acid Fuel-Cell Electrodes.

    PubMed

    Naumov, Olga; Naumov, Sergej; Flyunt, Roman; Abel, Bernd; Varga, Aron

    2016-12-08

    Similar to polymer electrolyte membrane fuel cells, the widespread application of solid acid fuel cells (SAFCs) has been hindered partly by the necessity of the use of the precious-metal catalyst Pt in the electrodes. Here we investigate multi-walled carbon nanotubes (MWCNTs) for their potential catalytic activity by using symmetric cell measurements of solid-acid-based electrochemical cells in a cathodic environment. For all measurements, the carbon nanotubes were Pt free and subject to either nitrogen or oxygen plasma treatment. AC impedance spectroscopy of the electrochemical cells, with and without a DC bias, was performed and showed significantly lower initial impedances for oxygen-plasma-treated MWCNTs compared to those treated with a nitrogen plasma. In symmetric cell measurements with a DC bias, the current declines quickly for oxygen-plasma-treated MWCNTs and more slowly, over 12 days, for nitrogen-plasma-treated MWCNTs. To elucidate the degradation mechanisms of the oxygen-plasma-treated MWCNTs under SAFC operating conditions, theoretical calculations were performed using DFT. The results indicate that several degradation mechanisms are likely to occur in parallel through the reduction of the surface oxygen groups that were introduced by the plasma treatment. This finally leads to an inert MWCNT surface and a very low electrode performance. Nitrogen-plasma-treated MWCNTs appear to have a higher stability and may be worthwhile for future investigations.

  11. Influence of Operating Parameters on Surface Properties of RF Glow Discharge Oxygen Plasma Treated TiO2/PET Film for Biomedical Application

    EPA Science Inventory

    Thin transparent titania (TiO2) films were coated on the surface of flexible poly (ethylene terephthalate) (PET) surface using standard sol gel techniques. The TiO2/PET thin film surfaces were further modified by exposing the films to a RF glow discharge oxygen plasma. The exposu...

  12. A new approach for orientation-controlled growth of CNTs: an in-depth analysis on the role of oxygen plasma treatment to catalyst

    NASA Astrophysics Data System (ADS)

    Tripathi, Nishant; Islam, S. S.

    2017-02-01

    In this paper, a novel and easy technique is proposed for orientation controlled growth of MWNTs. The results indicate that when CNT growth was carried over the substrate, not treated with plasma, horizontal network of MWNTs was formed. Plasma treatment to the substrate prior to CNTs growth led to formation of vertically aligned MWNTs. An in situ growth as a function of plasma treatment time reveals the mechanism behind this flip process. All experiments were performed under atmospheric pressure. At every step during time-dependent growth process, CNTs were characterized using FESEM, HRTEM, and Raman spectroscopy. Iron sputtered silicon substrate was also investigated to validate the excellent formation of as-grown vertical CNTs and also to analyze the role of oxygen plasma behind the orientation-controlled growth. The as-grown CNTs over the iron sputtered silicon substrate with or without plasma treatment were characterized by FESEM and AFM. The successful orientation-controlled growth of CNTs was achieved.

  13. Production of intracellular reactive oxygen species and change of cell viability induced by atmospheric pressure plasma in normal and cancer cells

    NASA Astrophysics Data System (ADS)

    Ja Kim, Sun; Min Joh, Hea; Chung, T. H.

    2013-10-01

    The effects of atmospheric pressure plasma jet on cancer cells (human lung carcinoma cells) and normal cells (embryonic kidney cells and bronchial epithelial cells) were investigated. Using a detection dye, the production of intracellular reactive oxygen species (ROS) was found to be increased in plasma-treated cells compared to non-treated and gas flow-treated cells. A significant overproduction of ROS and a reduction in cell viability were induced by plasma exposure on cancer cells. Normal cells were observed to be less affected by the plasma-mediated ROS, and cell viability was less changed. The selective effect on cancer and normal cells provides a promising prospect of cold plasma as a cancer therapy.

  14. A New Radio Frequency Plasma Oxygen Primary Ion Source on Nano Secondary Ion Mass Spectrometry for Improved Lateral Resolution and Detection of Electropositive Elements at Single Cell Level.

    PubMed

    Malherbe, Julien; Penen, Florent; Isaure, Marie-Pierre; Frank, Julia; Hause, Gerd; Dobritzsch, Dirk; Gontier, Etienne; Horréard, François; Hillion, François; Schaumlöffel, Dirk

    2016-07-19

    An important application field of secondary ion mass spectrometry at the nanometer scale (NanoSIMS) is the detection of chemical elements and, in particular, metals at the subcellular level in biological samples. The detection of many trace metals requires an oxygen primary ion source to allow the generation of positive secondary ions with high yield in the NanoSIMS. The duoplasmatron oxygen source is commonly used in this ion microprobe but cannot achieve the same quality of images as the cesium primary ion source used to produce negative secondary ions (C(-), CN(-), S(-), P(-)) due to a larger primary ion beam size. In this paper, a new type of an oxygen ion source using a rf plasma is fitted and characterized on a NanoSIMS50L. The performances of this primary ion source in terms of current density and achievable lateral resolution have been characterized and compared to the conventional duoplasmatron and cesium sources. The new rf plasma oxygen source offered a net improvement in terms of primary beam current density compared to the commonly used duoplasmatron source, which resulted in higher ultimate lateral resolutions down to 37 nm and which provided a 5-45 times higher apparent sensitivity for electropositive elements. Other advantages include a better long-term stability and reduced maintenance. This new rf plasma oxygen primary ion source has been applied to the localization of essential macroelements and trace metals at basal levels in two biological models, cells of Chlamydomonas reinhardtii and Arabidopsis thaliana.

  15. The effect of nitrogen and oxygen plasma on the wear properties and adhesion strength of the diamond-like carbon film coated on PTFE

    NASA Astrophysics Data System (ADS)

    Ozeki, K.; Hirakuri, K. K.

    2008-01-01

    Diamond-like carbon (DLC) films were deposited on polytetrafluoroethylene (PTFE) using a radiofrequency plasma chemical vapour deposition method. Prior to DLC coating, the PTFE substrates were modified with O 2 and N 2 plasma to enhance the adhesion strength of the DLC film to the substrate. The effect of the plasma pre-treatment on the chemical composition and the surface energy of the plasma pre-treated PTFE surface was investigated by X-ray photoelectron spectroscopy (XPS) and static water contact angle measurement, respectively. A pull-out test and a ball-on-disc test were carried out to evaluate the adhesion strength and the wear properties of the DLC-coated PTFE. In the N 2 plasma pre-treatment, the XPS result indicated that defluorination and the nitrogen grafting occurred on the plasma pre-treated PTFE surface, and the water contact angle decreased with increasing the plasma pre-treatment time. In the O 2 plasma pre-treatment, no grafting of the oxygen occurred, and the water contact angle slightly increased with the treatment time. In the pull-out test, the adhesion strength of the DLC film to the PTFE substrate was improved with the plasma pre-treatment to the PTFE substrate, and N 2 plasma pre-treatment was more effective than the O 2 plasma pre-treatment. In the ball-on-disc test, the DLC film with the N 2 plasma pre-treatment showed good wear resistance, compared with that with O 2 plasma pre-treatment.

  16. Suppression of Oxygen Impurity Incorporation into Silicon Films Prepared from Surface-Wave Excited H2/SiH4 Plasma

    NASA Astrophysics Data System (ADS)

    Somiya, Satoru; Toyoda, Hirotaka; Hotta, Yoshihiko; Sugai, Hideo

    2004-11-01

    Surface-wave plasma (SWP) in SiH4 highly diluted with H2 at 2.45 GHz and 2 kW is applied to the deposition of polycrystalline silicon thin films. When a quartz window is used as a microwave injection for discharge, an oxygen impurity level of up to ˜1.5% is observed in the deposited films. Mass spectrometry reveals that the origin of oxygen is water, i.e., the chemical erosion product of the quartz window (SiO2) caused by many hydrogen radicals in high-density plasma. By replacing the quartz window with an alumina (Al2O3) window, oxygen impurity level is markedly reduced, along with the increase in the grain size of films.

  17. In vitro study of 3D PLGA/n-HAp/β-TCP composite scaffolds with etched oxygen plasma surface modification in bone tissue engineering

    NASA Astrophysics Data System (ADS)

    Roh, Hee-Sang; Jung, Sang-Chul; Kook, Min-Suk; Kim, Byung-Hoon

    2016-12-01

    Three-dimensional (3D) scaffolds have many advantageous properties for bone tissue engineering application, due to its controllable properties such as pore size, structural shape and interconnectivity. In this study, effects on oxygen plasma surface modification and adding of nano-hydroxyapatite (n-HAp) and β-tricalcium phosphate (β-TCP) on the 3D PLGA/n-HAp/β-TCP scaffolds for improving preosteoblast cell (MC3T3-E1) adhesion, proliferation and differentiation were investigated. The 3D PLGA/n-HAp/β-TCP scaffolds were fabricated by 3D Bio-Extruder equipment. The 3D scaffolds were prepared with 0°/90° architecture and pore size of approximately 300 μm. In addition 3D scaffolds surface were etched by oxygen plasma to enhance the hydrophilic property and surface roughness. After oxygen plasma treatment, the surface chemistry and morphology were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. And also hydrophilic property was measured by contact angle. The MC3T3-E1 cell proliferation and differentiation were investigated by MTT assay and ALP activity. In present work, the 3D PLGA/HAp/beta-TCP composite scaffold with suitable structure for the growth of osteoblast cells was successfully fabricated by 3D rapid prototyping technique. The surface hydrophilicity and roughness of 3D scaffold increased by oxygen plasma treatment had a positive effect on cell adhesion, proliferation, and differentiation. Furthermore, the differentiation of MC3T3-E1 cell was significantly enhanced by adding of n-HAp and β-TCP on 3D PLGA scaffold. As a result, combination of bioceramics and oxygen plasma treatment showed a synergistic effect on biocompatibility of 3D scaffolds. This result confirms that this technique was useful tool for improving the biocompatibility in bone tissue engineering application.

  18. The effect of oxygen plasma ashing on the resistance of TiN bottom electrode for phase change memory

    NASA Astrophysics Data System (ADS)

    Dan, Gao; Bo, Liu; Ying, Li; Zhitang, Song; Wanchun, Ren; Juntao, Li; Zhen, Xu; Shilong, Lü; Nanfei, Zhu; Jiadong, Ren; Yipeng, Zhan; Hanming, Wu; Songlin, Feng

    2015-05-01

    Phase change memory (PCM) has been regarded as a promising candidate for the next generation of nonvolatile memory. To decrease the power required to reset the PCM cell, titanium nitride (TiN) is preferred to be used as the bottom electrode of PCM due to its low thermal and suitable electrical conductivity. However, during the manufacture of PCM cell in 40 nm process node, abnormally high and discrete distribution of the resistance of TiN bottom electrode was found, which might be induced by the surface oxidation of TiN bottom electrode during the photoresist ashing process by oxygen plasma. In this work, we have studied the oxidation of TiN and found that with the increasing oxygen plasma ashing time, the thickness of the TiO2 layer became thicker and the state of the TiO2 layer changed from amorphous to crystalline, respectively. The resistance of TiN electrode contact chain with 4-5 nm TiO2 layer was confirmed to be almost three-orders of magnitude higher than that of pure TiN electrode, which led to the failure issue of PCM cell. We efficiently removed the oxidation TiO2 layer by a chemical mechanical polishing (CMP) process, and we eventually recovered the resistance of TiN bottom electrode from 1 × 105 Ω/via back to 6 × 102 Ω/via and successfully achieved a uniform resistance distribution of the TiN bottom electrode. Project supported by the National Key Basic Research Program of China (Nos. 2010CB934300, 2013CBA01900, 2011CBA00607, 2011CB932804), the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDA09020402), the National Integrate Circuit Research Program of China (No. 2009ZX02023-003), the National Natural Science Foundation of China (Nos. 61176122, 61106001, 61261160500, 61376006), and the Science and Technology Council of Shanghai (Nos. 12nm0503701, 13DZ2295700, 12QA1403900, 13ZR1447200).

  19. Nanoporous Silver Film Fabricated by Oxygen Plasma: A Facile Approach for SERS Substrates.

    PubMed

    Ma, Chaoxiong; Trujillo, Michael J; Camden, Jon P

    2016-09-14

    Nanoporous metal films are promising substrates for surfaced-enhanced Raman scattering (SERS) measurement, owing to their homogeneity, large surface area, and abundant hot-spots. Herein, a facile procedure was developed to fabricate nanoporous Ag film on various substrate surfaces. Thermally deposited Ag film was first treated with O2 plasma, resulting in porous Ag/AgxO film (AgxO-NF) with nanoscale feature. Sodium citrate was then used to reduce AgxO to Ag, forming nanoporous Ag film (AgNF) with similar morphology. The AgNF substrate demonstrates 30-fold higher Raman intensity than Ag film over polystyrene nanospheres (d = 600 nm) using 4-mercaptobenzoic acid (4-MBA) as the sensing molecule. Comparing with ordinary Raman measurement on 4-MBA solution, an enhancement factor of ∼6 × 10(6) was determined for AgNF. The AgNF substrate was evaluated for benzoic acid, 4-nitrophenol, and 2-mercaptoethanesulfonate, showing high SERS sensitivity for chemicals that bind weakly to Ag surface and molecules with relatively small Raman cross section at micromolar concentration. In addition to its simplicity, the procedure can be applied to various materials such as transparency film, filter paper, hard polystyrene film, and aluminum foil, revealing similar Raman sensitivity. By testing the durability of the substrate, we found that the AgxO films can be stored in ambient conditions for more than 90 days and still deliver the same SERS intensity if the films are treated with sodium citrate before use. These results demonstrate the advantage of the proposed approach for mass production of low-cost, sensitive, and durable SERS substrates. The transferable nature of these AgNF to different flexible surfaces also allows their easy integration with other sensing schemes.

  20. Adaptable DC offset correction

    NASA Technical Reports Server (NTRS)

    Golusky, John M. (Inventor); Muldoon, Kelly P. (Inventor)

    2009-01-01

    Methods and systems for adaptable DC offset correction are provided. An exemplary adaptable DC offset correction system evaluates an incoming baseband signal to determine an appropriate DC offset removal scheme; removes a DC offset from the incoming baseband signal based on the appropriate DC offset scheme in response to the evaluated incoming baseband signal; and outputs a reduced DC baseband signal in response to the DC offset removed from the incoming baseband signal.

  1. Responses of Solid Tumor Cells in DMEM to Reactive Oxygen Species Generated by Non-Thermal Plasma and Chemically Induced ROS Systems

    NASA Astrophysics Data System (ADS)

    Kaushik, Neha; Uddin, Nizam; Sim, Geon Bo; Hong, Young June; Baik, Ku Youn; Kim, Chung Hyeok; Lee, Su Jae; Kaushik, Nagendra Kumar; Choi, Eun Ha

    2015-02-01

    In this study, we assessed the role of different reactive oxygen species (ROS) generated by soft jet plasma and chemical-induced ROS systems with regard to cell death in T98G, A549, HEK293 and MRC5 cell lines. For a comparison with plasma, we generated superoxide anion (O2-), hydroxyl radical (HO.), and hydrogen peroxide (H2O2) with chemicals inside an in vitro cell culture. Our data revealed that plasma decreased the viability and intracellular ATP values of cells and increased the apoptotic population via a caspase activation mechanism. Plasma altered the mitochondrial membrane potential and eventually up-regulated the mRNA expression levels of BAX, BAK1 and H2AX gene but simultaneously down-regulated the levels of Bcl-2 in solid tumor cells. Moreover, a western blot analysis confirmed that plasma also altered phosphorylated ERK1/2/MAPK protein levels. At the same time, using ROS scavengers with plasma, we observed that scavengers of HO. (mannitol) and H2O2 (catalase and sodium pyruvate) attenuated the activity of plasma on cells to a large extent. In contrast, radicals generated by specific chemical systems enhanced cell death drastically in cancer as well as normal cell lines in a dose-dependent fashion but not specific with regard to the cell type as compared to plasma.

  2. Plasma chemistry in wire chambers

    SciTech Connect

    Wise, J.

    1990-05-01

    The phenomenology of wire chamber aging is discussed and fundamentals of proportional counters are presented. Free-radical polymerization and plasma polymerization are discussed. The chemistry of wire aging is reviewed. Similarities between wire chamber plasma (>1 atm dc-discharge) and low-pressure rf-discharge plasmas, which have been more widely studied, are suggested. Construction and use of a system to allow study of the plasma reactions occurring in wire chambers is reported. A proportional tube irradiated by an {sup 55}Fe source is used as a model wire chamber. Condensable species in the proportional tube effluent are concentrated in a cryotrap and analyzed by gas chromatography/mass spectrometry. Several different wire chamber gases (methane, argon/methane, ethane, argon/ethane, propane, argon/isobutane) are tested and their reaction products qualitatively identified. For all gases tested except those containing methane, use of hygroscopic filters to remove trace water and oxygen contaminants from the gas resulted in an increase in the average molecular weight of the products, consistent with results from low-pressure rf-discharge plasmas. It is suggested that because water and oxygen inhibit polymer growth in the gas phase that they may also reduce polymer deposition in proportional tubes and therefore retard wire aging processes. Mechanistic implications of the plasma reactions of hydrocarbons with oxygen are suggested. Unresolved issues in this work and proposals for further study are discussed.

  3. Formation of oxygen vacancies and Ti3+ state in TiO2 thin film and enhanced optical properties by air plasma treatment

    PubMed Central

    Bharti, Bandna; Kumar, Santosh; Lee, Heung-No; Kumar, Rajesh

    2016-01-01

    This is the first time we report that simply air plasma treatment can also enhances the optical absorbance and absorption region of titanium oxide (TiO2) films, while keeping them transparent. TiO2 thin films having moderate doping of Fe and Co exhibit significant enhancement in the aforementioned optical properties upon air plasma treatment. The moderate doping could facilitate the formation of charge trap centers or avoid the formation of charge recombination centers. Variation in surface species viz. Ti3+, Ti4+, O2−, oxygen vacancies, OH group and optical properties was studied using X-ray photon spectroscopy (XPS) and UV-Vis spectroscopy. The air plasma treatment caused enhanced optical absorbance and optical absorption region as revealed by the formation of Ti3+ and oxygen vacancies in the band gap of TiO2 films. The samples were treated in plasma with varying treatment time from 0 to 60 seconds. With the increasing treatment time, Ti3+ and oxygen vacancies increased in the Fe and Co doped TiO2 films leading to increased absorbance; however, the increase in optical absorption region/red shift (from 3.22 to 3.00 eV) was observed in Fe doped TiO2 films, on the contrary Co doped TiO2 films exhibited blue shift (from 3.36 to 3.62 eV) due to Burstein Moss shift. PMID:27572095

  4. Formation of oxygen vacancies and Ti(3+) state in TiO2 thin film and enhanced optical properties by air plasma treatment.

    PubMed

    Bharti, Bandna; Kumar, Santosh; Lee, Heung-No; Kumar, Rajesh

    2016-08-30

    This is the first time we report that simply air plasma treatment can also enhances the optical absorbance and absorption region of titanium oxide (TiO2) films, while keeping them transparent. TiO2 thin films having moderate doping of Fe and Co exhibit significant enhancement in the aforementioned optical properties upon air plasma treatment. The moderate doping could facilitate the formation of charge trap centers or avoid the formation of charge recombination centers. Variation in surface species viz. Ti(3+), Ti(4+), O(2-), oxygen vacancies, OH group and optical properties was studied using X-ray photon spectroscopy (XPS) and UV-Vis spectroscopy. The air plasma treatment caused enhanced optical absorbance and optical absorption region as revealed by the formation of Ti(3+) and oxygen vacancies in the band gap of TiO2 films. The samples were treated in plasma with varying treatment time from 0 to 60 seconds. With the increasing treatment time, Ti(3+) and oxygen vacancies increased in the Fe and Co doped TiO2 films leading to increased absorbance; however, the increase in optical absorption region/red shift (from 3.22 to 3.00 eV) was observed in Fe doped TiO2 films, on the contrary Co doped TiO2 films exhibited blue shift (from 3.36 to 3.62 eV) due to Burstein Moss shift.

  5. Absolute atomic oxygen density measurements for nanosecond-pulsed atmospheric-pressure plasma jets using two-photon absorption laser-induced fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Jiang, C.; Carter, C.

    2014-12-01

    Nanosecond-pulsed plasma jets that are generated under ambient air conditions and free from confinement of electrodes have become of great interest in recent years due to their promising applications in medicine and dentistry. Reactive oxygen species that are generated by nanosecond-pulsed, room-temperature non-equilibrium He-O2 plasma jets among others are believed to play an important role during the bactericidal or sterilization processes. We report here absolute measurements of atomic oxygen density in a 1 mm-diameter He/(1%)O2 plasma jet at atmospheric pressure using two-photon absorption laser-induced fluorescence spectroscopy. Oxygen number density on the order of 1013 cm-3 was obtained in a 150 ns, 6 kV single-pulsed plasma jet for an axial distance up to 5 mm above the device nozzle. Temporally resolved O density measurements showed that there are two maxima, separated in time by 60-70 µs, and a total pulse duration of 260-300 µs. Electrostatic modeling indicated that there are high-electric-field regions near the nozzle exit that may be responsible for the observed temporal behavior of the O production. Both the field-distribution-based estimation of the time interval for the O number density profile and a pulse-energy-dependence study confirmed that electric-field-dependent, direct and indirect electron-induced processes play important roles for O production.

  6. Formation of oxygen vacancies and Ti3+ state in TiO2 thin film and enhanced optical properties by air plasma treatment

    NASA Astrophysics Data System (ADS)

    Bharti, Bandna; Kumar, Santosh; Lee, Heung-No; Kumar, Rajesh

    2016-08-01

    This is the first time we report that simply air plasma treatment can also enhances the optical absorbance and absorption region of titanium oxide (TiO2) films, while keeping them transparent. TiO2 thin films having moderate doping of Fe and Co exhibit significant enhancement in the aforementioned optical properties upon air plasma treatment. The moderate doping could facilitate the formation of charge trap centers or avoid the formation of charge recombination centers. Variation in surface species viz. Ti3+, Ti4+, O2‑, oxygen vacancies, OH group and optical properties was studied using X-ray photon spectroscopy (XPS) and UV-Vis spectroscopy. The air plasma treatment caused enhanced optical absorbance and optical absorption region as revealed by the formation of Ti3+ and oxygen vacancies in the band gap of TiO2 films. The samples were treated in plasma with varying treatment time from 0 to 60 seconds. With the increasing treatment time, Ti3+ and oxygen vacancies increased in the Fe and Co doped TiO2 films leading to increased absorbance; however, the increase in optical absorption region/red shift (from 3.22 to 3.00 eV) was observed in Fe doped TiO2 films, on the contrary Co doped TiO2 films exhibited blue shift (from 3.36 to 3.62 eV) due to Burstein Moss shift.

  7. Preanalytical standardization for reactive oxygen species derived oxysterol analysis in human plasma by liquid chromatography-tandem mass spectrometry.

    PubMed

    Helmschrodt, C; Becker, S; Thiery, J; Ceglarek, U

    2014-04-11

    The analysis of the oxysterols 7-keto-, 7-α/β-hydroxy-, 5α,6α-epoxy-, 5β,6β-epoxycholesterol and cholestane-3β,5α,6β-triol derived from reactive oxygen species (ROS) is of interest as biomarkers in the field of atherosclerosis. Preanalytical validation is a crucial point to minimize the susceptibility of oxysterols to in vitro autoxidation. The aim of this study was to standardize a preanalytical protocol for ROS-derived oxysterol analysis by liquid chromatography-tandem mass spectrometry in human plasma. Sample matrices were compared and stability of free oxysterols in whole blood and EDTA-plasma was investigated with regard to short-term storage until sample preparation, freeze-thaw cycles, addition of butylated hydroxytoluene and long-term storage up to 1 year at different temperatures (-20 °C, -80 °C and -130 °C) as well as different storage containers (safe-lock tubes, cryo tubes and straws). Sample preparation prior LC-MS/MS analysis was reduced to a simple concentration and protein precipitation step. Storing EDTA-whole blood for 30 min at room temperature resulted in <25% concentration changes, within acceptable change limits (ACL). In freshly prepared plasma samples, free oxysterols were stable for 90 min stored at 4 °C with concentration changes <23.5% (within ACL). Up to nine freeze-thaw cycles did not affect analyte concentrations (concentration change -8.5% to +5.0%). 7-Ketocholesterol was stable for 2 years stored <-80 °C; concentration changes below 20.5% (within ACL). The remaining oxysterols were stored for a maximum of 2-4 weeks without exceeding ACL. The addition of BHT did not reveal improvement in analyte stability for storage at -80 or -130 °C. We developed a standardized preanalytical protocol for oxysterol analysis based on LC-MS/MS, compared cryobanking conditions for each oxysterol and present data for long-term storage up to 2 years.

  8. Effects of oolong tea on plasma antioxidative capacity in mice loaded with restraint stress assessed using the oxygen radical absorbance capacity (ORAC) assay.

    PubMed

    Kurihara, Hiroshi; Fukami, Harukazu; Asami, Sumio; Toyoda, Yoshiko; Nakai, Masaaki; Shibata, Hiroshi; Yao, Xin-Sheng

    2004-07-01

    In the present study, we investigated the antioxidative effect of oolong tea in vitro and in vivo using the oxygen radical absorbance capacity (ORAC) assay. An oolong tea extract, catechin and related compounds suppressed the oxidation of fluorescence induced by AAPH in a dose-dependent manner, that is, they prolonged the antioxidant time in vitro. Oral administration of the oolong tea extract to mice treated with restraint stress increased ORAC activity in plasma as compared with a stress control group. The extract also increased plasma vitamin C levels, and there was a good relationship between ORAC activity and the vitamin C level in plasma. The elevation of plasma ORAC and vitamin C level may have been related to the stress-relieving effect of oolong tea. These effects are probably due to the antioxidative properties of the tea. Thus, these findings suggested that oolong tea has beneficial effects on health related to its antioxidative action.

  9. Absolute atomic oxygen and nitrogen densities in radio-frequency driven atmospheric pressure cold plasmas: Synchrotron vacuum ultra-violet high-resolution Fourier-transform absorption measurements

    SciTech Connect

    Niemi, K.; O'Connell, D.; Gans, T.; Oliveira, N. de; Joyeux, D.; Nahon, L.; Booth, J. P.

    2013-07-15

    Reactive atomic species play a key role in emerging cold atmospheric pressure plasma applications, in particular, in plasma medicine. Absolute densities of atomic oxygen and atomic nitrogen were measured in a radio-frequency driven non-equilibrium plasma operated at atmospheric pressure using vacuum ultra-violet (VUV) absorption spectroscopy. The experiment was conducted on the DESIRS synchrotron beamline using a unique VUV Fourier-transform spectrometer. Measurements were carried out in plasmas operated in helium with air-like N{sub 2}/O{sub 2} (4:1) admixtures. A maximum in the O-atom concentration of (9.1 {+-} 0.7) Multiplication-Sign 10{sup 20} m{sup -3} was found at admixtures of 0.35 vol. %, while the N-atom concentration exhibits a maximum of (5.7 {+-} 0.4) Multiplication-Sign 10{sup 19} m{sup -3} at 0.1 vol. %.

  10. Film Characteristics of Low-Temperature Plasma-Enhanced Chemical Vapor Deposition Silicon Dioxide Using Tetraisocyanatesilane and Oxygen

    NASA Astrophysics Data System (ADS)

    Idris, Irman; Sugiura, Osamu

    1998-12-01

    Silicon dioxide films were deposited in a parallel-plate electrode RF plasma-enhanced chemical vapor deposition (PECVD) system using hydrogen-free tetraisocyanatesilane (TICS) and oxygen. The deposition parameters were varied systematically, and the films were characterized by measuring infrared spectra, density, etch rate, refractive index, and current-voltage (I V) and capacitance-voltage (C V) characteristics, as well as by examining their annealing behavior. At 300°C and a TICS partial pressure ratio of 20%, a water-free and hydroxyl-group-free SiO2 film was obtained. The film density, BHF etch rate, refractive index, resistivity, and dielectric constant were 2.3 g/cm3, 330 nm/min, 1.46, 7×1015 Ω·cm, and 3.6, respectively. The film quality degraded and, simultaneously, the film absorbed moisture from the atmosphere with decreasing deposition temperature; however, the quality can be improved by reducing TICS partial pressure. SiO2 films could be deposited even at 15°C, and had a resistivity of about 1013Ω·cm. Infrared measurements showed that SiO2 films deposited from TICS/O2 contained less absorbed water than those deposited from hydrogen-containing source materials at the same deposition temperature.

  11. Surface characteristics, mechanical properties, and cytocompatibility of oxygen plasma-implanted porous nickel titanium shape memory alloy.

    PubMed

    Wu, S L; Chu, Paul K; Liu, X M; Chung, C Y; Ho, J P Y; Chu, C L; Tjong, S C; Yeung, K W K; Lu, W W; Cheung, K M C; Luk, K D K

    2006-10-01

    Good surface properties and biocompatibility are crucial to porous NiTi shape memory alloys (SMA) used in medical implants, as possible nickel release from porous NiTi may cause deleterious effects in the human body. In this work, oxygen plasma immersion ion implantation (O-PIII) was used to reduce the amount of nickel leached from porous NiTi alloys with a porosity of 42% prepared by capsule-free hot isostatic pressing. The mechanical properties, surface properties, and biocompatibility were studied by compression tests, X-ray photoelectron spectroscopy (XPS), and cell culturing. The O-PIII porous NiTi SMAs have good mechanical properties and excellent superelasticity, and the amount of nickel leached from the O-PIII porous NiTi is much less than that from the untreated samples. XPS results indicate that a nickel-depleted surface layer predominantly composed of TiO(2) is produced by O-PIII and acts as a barrier against out-diffusion of nickel. The cell culturing tests reveal that both the O-PIII and untreated porous NiTi alloys have good biocompatibility.

  12. Atomic oxygen TALIF measurements in an atmospheric-pressure microwave plasma jet with in situ xenon calibration

    NASA Astrophysics Data System (ADS)

    van Gessel, A. F. H.; van Grootel, S. C.; Bruggeman, P. J.

    2013-10-01

    Two-photon absorption laser-induced fluorescence (TALIF) is used to measure the absolute density of atomic oxygen (O) in a coaxial microwave jet in ambient air at atmospheric pressure, operated with a mixture of He and a few per cent of air. The TALIF signal is calibrated using a gas mixture containing Xe. A novel method to perform calibration in situ, at atmospheric pressure, is introduced. The branching ratios of several Xe mixtures are reported, to enable us to perform the Xe calibration without the need for a vacuum vessel. The O densities are measured spatially resolved, and as a function of admixed air to the He, and microwave power. The electron density and temperatures are measured using Thomson scattering, and the N2 and O2 densities are measured using Raman scattering. O densities are found to have a maximum of (4-6) × 1022 m-3, which indicate that O2 is close to fully dissociated in the plasma. This is confirmed by the Raman scattering measurements. O is found to recombine mainly into species other than O2 in the afterglow, which is suggested to consist of O3 and oxidized components of NO.

  13. Simple fabrication of hydrophilic nanochannels using the chemical bonding between activated ultrathin PDMS layer and cover glass by oxygen plasma.

    PubMed

    Kim, So Hyun; Cui, Yidan; Lee, Min Jung; Nam, Seong-Won; Oh, Doori; Kang, Seong Ho; Kim, Youn Sang; Park, Sungsu

    2011-01-21

    This study describes a simple and low cost method for fabricating enclosed transparent hydrophilic nanochannels by coating low-viscosity PDMS (monoglycidyl ether-terminated polydimethylsiloxane) as an adhesion layer onto the surface of the nanotrenches that are molded with a urethane-based UV-curable polymer, Norland Optical Adhesive (NOA 63). In detail, the nanotrenches made of NOA 63 were replicated from a Si master mold and coated with 6 nm thick layer of PDMS. These nanotrenches underwent an oxygen plasma treatment and finally were bound to a cover glass by chemical bonding between silanol and hydroxyl groups. Hydrophobic recovery that is observed in the bulk PDMS was not observed in the thin film of PDMS on the mold and the PDMS-coated nanochannel maintained its surface hydrophilicity for at least one month. The potentials of the nanochannels for bioapplications were demonstrated by stretching λ-DNA (48,502 bp) in the channels. Therefore, this fabrication approach provides a practical solution for the simple fabrication of the nanochannels for bioapplications.

  14. Impact of cyclic plasma treatment on oxygen vacancy defects in TiN/HfZrO/SiON/Si gate stacks

    SciTech Connect

    Bhuyian, Md Nasir Uddin Misra, D.; Poddar, S.; Tapily, K.; Clark, R. D.; Consiglio, S.; Wajda, C. S.; Nakamura, G.; Leusink, G. J.

    2015-05-11

    This work evaluates the defects in HfZrO as a function of Zr addition into HfO{sub 2} and when the dielectric was subjected to a slot-plane-antenna (SPA) plasma treatment in a cyclic process to form TiN/HfZrO/SiON/Si gate stacks. The defect energy levels, estimated by temperature-dependent current-voltage measurements, suggest that Zr addition in HfO{sub 2} modifies the charge state of the oxygen vacancy formation, V{sup +}. The influence of electron affinity variation of Hf and Zr ions on the charged oxygen vacancy levels seems to have contributed to the increase in defect activation energy, E{sub a}, from 0.32 eV to 0.4 eV. The cyclic SPA plasma exposure further reduces the oxygen vacancy formation because of the film densification. When the dielectric was subjected to a constant voltage stress, the charge state oxygen vacancy formation changes to V{sup 2+} and improvement was eliminated. The trap assisted tunneling behavior, as observed by the stress induced leakage current characteristics, further supports the oxygen vacancy formation model.

  15. Impact of cyclic plasma treatment on oxygen vacancy defects in TiN/HfZrO/SiON/Si gate stacks

    NASA Astrophysics Data System (ADS)

    Bhuyian, Md Nasir Uddin; Poddar, S.; Misra, D.; Tapily, K.; Clark, R. D.; Consiglio, S.; Wajda, C. S.; Nakamura, G.; Leusink, G. J.

    2015-05-01

    This work evaluates the defects in HfZrO as a function of Zr addition into HfO2 and when the dielectric was subjected to a slot-plane-antenna (SPA) plasma treatment in a cyclic process to form TiN/HfZrO/SiON/Si gate stacks. The defect energy levels, estimated by temperature-dependent current-voltage measurements, suggest that Zr addition in HfO2 modifies the charge state of the oxygen vacancy formation, V+. The influence of electron affinity variation of Hf and Zr ions on the charged oxygen vacancy levels seems to have contributed to the increase in defect activation energy, Ea, from 0.32 eV to 0.4 eV. The cyclic SPA plasma exposure further reduces the oxygen vacancy formation because of the film densification. When the dielectric was subjected to a constant voltage stress, the charge state oxygen vacancy formation changes to V2+ and improvement was eliminated. The trap assisted tunneling behavior, as observed by the stress induced leakage current characteristics, further supports the oxygen vacancy formation model.

  16. Reactive plasma synthesis of nanocrystalline ceramic oxides

    NASA Astrophysics Data System (ADS)

    Sreekumar, K. P.; Vijay, M.; Thiyagarajan, T. K.; Krishnan, K.; Ananthapadmanabhan, P. V.

    2010-02-01

    Reactive plasma synthesis is an attractive route to synthesize nanocrystalline materials. A 40 kW DC non-transferred arc plasma reactor has been designed and developed in our laboratory for synthesis of nanocrystalline materials. The main components of the plasma reactor include a 40 kW DC plasma generator or plasma torch, water-cooled reactor segment, product collection facility, DC power supply, cooling-water system and exhaust gas vent. The system has been used to synthesize nano-crystalline oxides of aluminium, titanium and zirconium. Aluminium metal powder was used as the starting material to synthesize alumina. The hydrides of Ti and Zr were used as the precursor for synthesis of nanocrystalline titania and zirconia respectively. The precursor powders were injected into the thermal plasma jet and were allowed to react with oxygen injected downstream the jet. The precursor powder particles were oxidized 'in-flight' to form nano-sized powder of the respective metal, which deposited on the walls of the reactor and collector assembly. Various analytical tools were used to characterized the products.

  17. Effective enhancement of hydrophilicity of solution indium zinc oxide-based thin-film transistors by oxygen plasma treatment of deposition layer surface

    NASA Astrophysics Data System (ADS)

    You, Hsin-Chiang; Wang, Yu-Chih

    2016-06-01

    In this paper, we describe the use of a simple and efficient sol-gel solution method for synthesizing indium zinc oxide (IZO) films for use as semiconductor channel layers in thin-film transistors (TFTs) on p-type silicon substrates. The performance of IZO-based TFTs was investigated, and the effect of oxygen plasma treatment on the surface of dielectric SiN x was observed. Oxygen plasma treatment effectively enhanced the electron mobility in IZO-based TFT devices from 0.005 to 1.56 cm2 V-1 s-1, an increase of more than 312 times, and effectively enhanced device performance. X-ray photoelectron spectroscopy analysis of the IZO film was performed to clarify element bonding.

  18. Radiative power and electron cooling rates for oxygen in steady-state and transient plasmas at densities beyond the coronal limit

    SciTech Connect

    Keane, C.; Skinner, C.H.

    1986-01-01

    We have developed a time-dependent, collisional-radiative model to calculate radiative power and electron cooling rates for oxygen at intermediate densities (10/sup 16/ cm/sup -3/ less than or equal to n/sub e/ less than or equal to 10/sup 20/ cm/sup -3/) where the usual coronal approximation is not valid. Large differences from coronal values are predicted. The behavior of the steady-state radiative power loss coefficient, L/sub Z, is investigated as the electron density is increased. Generalized power loss coefficients applicable to transient plasmas are derived and applied to ionizing and recombining oxygen plasmas. Time-dependent effects are found to play a large role both in terms of the total radiated power and the net electron energy loss rate. 41 refs., 11 figs.

  19. Simulation of a non-equilibrium helium plasma bullet emerging into oxygen at high pressure (250-760 Torr) and interacting with a substrate

    NASA Astrophysics Data System (ADS)

    Yan, Wen; Economou, Demetre J.

    2016-09-01

    A two-dimensional computational study of a plasma bullet emanating from a helium gas jet in oxygen ambient at high pressure (250-760 Torr) was performed, with emphasis on the bullet interaction with a substrate. Power was applied in the form of a trapezoidal +5 kV pulse lasting 150 ns. A neutral gas transport model was employed to predict the concentration distributions of helium and oxygen in the system. These were then used in a plasma dynamics model to investigate the characteristics of the plasma bullet during its propagation and interaction with a substrate. Upon ignition, the discharge first propagated as a surface wave along the inner wall of the containing tube, and then exited the tube with a well-defined ionization front (streamer or plasma bullet). The plasma bullet evolved from a hollow (donut-shaped) feature to one where the maximum of ionization was on axis. The bullet propagated in the gap between the tube exit and the substrate with an average speed of ˜2 × 105 m/s. Upon encountering a metal substrate, the bullet formed a conductive channel to the substrate. Upon encountering a dielectric substrate, the bullet turned into an ionization wave propagating radially along the substrate surface. For a conductive substrate, the radial species fluxes to the surface peaked on the symmetry axis. For a dielectric substrate, a ring-shaped flux distribution was observed. The "footprint" of plasma-surface interaction increased either by decreasing the gap between tube exit and substrate, decreasing the relative permittivity of an insulating substrate, or decreasing pressure. As the system pressure was lowered from 760 to 250 Torr, the discharge was initiated earlier, and the plasma bullet propagation speed increased. A reverse electric field developed during the late stages of the ramp-down of the pulse, which accelerated electrons forming a brief backward discharge.

  20. Bio-Decontamination of Water and Surfaces by DC Discharges in Atmospheric Air

    NASA Astrophysics Data System (ADS)

    Machala, Zdenko; Tarabová, Barbora; Pelach, Michal; Šipoldová, Zuzana; Hensel, Karol; Janda, Mário; Šikurová, Libuša

    Two types of DC-driven atmospheric air discharges, including a streamer corona and a transient spark with short high current pulses of limited energy, were employed for bio-decontamination of water and various surfaces (agar plates, plastic foils, human teeth) contaminated by bacteria or spores (Salmonella typhimurium, Bacillus cereus). Both discharges generate cold non-equilibrium plasma. The discharges combined with the electro-spraying of the treated water through the needle electrode lead to fast and efficient bio-decontamination. Experiments comparing direct and indirect plasma effects, oxidation stress measurements in the cell membranes, and chemical changes induced in the treated water enable assessment of the plasma agents being responsible for microbial inactivation. Radicals and reactive oxygen species seem to be dominant biocidal agents, although deeper understanding of the plasma-induced water chemistry and of the temporal evolution of the bio-inactivation processes is needed.

  1. Energetic electron avalanches and mode transitions in planar inductively coupled radio-frequency driven plasmas operated in oxygen

    SciTech Connect

    Zaka-ul-Islam, M.; Niemi, K.; Gans, T.; O'Connell, D.

    2011-07-25

    Space and phase resolved optical emission spectroscopic measurements reveal that in certain parameter regimes, inductively coupled radio-frequency driven plasmas exhibit three distinct operation modes. At low powers, the plasma operates as an alpha-mode capacitively coupled plasma driven through the dynamics of the plasma boundary sheath potential in front of the antenna. At high powers, the plasma operates in inductive mode sustained through induced electric fields due to the time varying currents and associated magnetic fields from the antenna. At intermediate powers, close to the often observed capacitive to inductive (E-H) transition regime, energetic electron avalanches are identified to play a significant role in plasma sustainment, similar to gamma-mode capacitively coupled plasmas. These energetic electrons traverse the whole plasma gap, potentially influencing plasma surface interactions as exploited in technological applications.

  2. Effects of oxygen plasma treatment on interfacial shear strength and post-peak residual strength of a PLGA fiber-reinforced brushite cement.

    PubMed

    Maenz, Stefan; Hennig, Max; Mühlstädt, Mike; Kunisch, Elke; Bungartz, Matthias; Brinkmann, Olaf; Bossert, Jörg; Kinne, Raimund W; Jandt, Klaus D

    2016-04-01

    Biodegradable calcium phosphate cements (CPCs) are promising materials for minimally invasive treatment of bone defects. However, CPCs have low mechanical strength and fracture toughness. One approach to overcome these limitations is the modification of the CPC with reinforcing fibers. The matrix-fiber interfacial shear strength (ISS) is pivotal for the biomechanical properties of fiber-reinforced CPCs. The aim of the current study was to control the ISS between a brushite-forming CPC and degradable PLGA fibers by oxygen plasma treatment and to analyze the impact of the ISS alterations on its bulk mechanical properties. The ISS between CPC matrix and PLGA fibers, tested in a single-fiber pull-out test, increased up to 2.3-fold to max. 3.22±0.92MPa after fiber oxygen plasma treatment (100-300W, 1-10min), likely due to altered surface chemistry and morphology of the fibers. This ISS increase led to more efficient crack bridging and a subsequent increase of the post-peak residual strength at biomechanically relevant, moderate strains (up to 1%). At the same time, the work of fracture significantly decreased, possibly due to an increased proportion of fractured fibers unable to further absorb energy by frictional sliding. Flexural strength and flexural modulus were not affected by the oxygen plasma treatment. This study shows for the first time that the matrix-fiber ISS and some of the resulting mechanical properties of fiber-reinforced CPCs can be improved by chemical modifications such as oxygen plasma treatment, generating the possibility of avoiding catastrophic failures at the implant site and thus enhancing the applicability of biodegradable CPCs for the treatment of (load-bearing) bone defects.

  3. Femtosecond, two-photon-absorption, laser-induced-fluorescence (fs-TALIF) imaging of atomic hydrogen and oxygen in non-equilibrium plasmas

    NASA Astrophysics Data System (ADS)

    Schmidt, Jacob B.; Roy, Sukesh; Kulatilaka, Waruna D.; Shkurenkov, Ivan; Adamovich, Igor V.; Lempert, Walter R.; Gord, James R.

    2017-01-01

    Femtosecond, two-photon-absorption laser-induced fluorescence (fs-TALIF) is employed to measure space- and time-resolved distributions of atomic hydrogen and oxygen in moderate-pressure, non-equilibrium, nanosecond-duration pulsed-discharge plasmas. Temporally and spatially resolved hydrogen and oxygen TALIF images are obtained over a range of low-temperature plasmas in mixtures of helium and argon at 100 Torr total pressure. The high-peak-intensity, low-average-energy fs pulses combined with the increased spectral bandwidth compared to traditional ns-duration laser pulses provide a large number of photon pairs that are responsible for the two-photon excitation, which results in an enhanced TALIF signal. Krypton and xenon TALIF are used for quantitative calibration of the hydrogen and oxygen concentrations, respectively, with similar excitation schemes being employed. This enables 2D collection of atomic-hydrogen and -oxygen TALIF signals with absolute number densities ranging from 2  ×  1012 cm-3 to 6  ×  1015 cm-3 and 1  ×  1013 cm-3 to 3  ×  1016 cm-3, respectively. These 2D images are the first application of TALIF imaging in moderate-pressure plasma discharges. 1D self-consistent modeling predictions show agreement with experimental results within the estimated experimental error of 25%. The present results can be used to further the development of higher fidelity kinetic models while quantifying plasma-source characteristics.

  4. Effects of oxygen plasma source ion implantation on microstructure evolution and mechanical properties of nickel-titanium shape memory alloy

    NASA Astrophysics Data System (ADS)

    Tan, Lizhen

    Near-equiatomic NiTi is an important shape memory alloy used in both medical and non-medical applications, which are dependent upon the surface characteristics of NiTi. The work presented here is the first use of plasma source ion implantation with oxygen as the incident species to modify the surface structure of NiTi shape memory alloy. Two levels of voltage bias and three levels of ion dose were employed to investigate the effect of processing parameters on surface microstructure and surface-related properties. Several surface analytical techniques, Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM), were employed to analyze the effects of the surface modification on surface characteristics including oxide thickness, oxide constitution, phase distribution, morphology and topography. A two-layer surface structure consisting of an oxide layer and a precipitate accommodation layer was observed on modified NiTi. The surface morphology, roughness and hydrophilicity, which are considered to play important roles in affecting protein adsorption behavior, were found to be altered by surface modification. The effects of surface modification on surface-related properties including corrosion resistance, hardness and wear resistance were evaluated by cyclic potentiodynamic polarization tests, Knoop hardness microindentation and fretting wear tests, respectively. The optimum corrosion and wear resistance of NiTi were achieved with ion implantation under high bias and moderate dose. Archard's equation was modified by incorporating the pseudoelasticity effect on wear resistance in addition to hardness. The modified Archard's equation better describes the fretting wear resistance of NiTi. A combination of nanoindentation and AES was employed to understand the relationship between mechanical properties and composition of the modified material.

  5. Study on the effect of hydrogen addition on the variation of plasma parameters of argon-oxygen magnetron glow discharge for synthesis of TiO2 films

    NASA Astrophysics Data System (ADS)

    Saikia, Partha; Saikia, Bipul Kumar; Bhuyan, Heman

    2016-04-01

    We report the effect of hydrogen addition on plasma parameters of argon-oxygen magnetron glow discharge plasma in the synthesis of H-doped TiO2 films. The parameters of the hydrogen-added Ar/O2 plasma influence the properties and the structural phases of the deposited TiO2 film. Therefore, the variation of plasma parameters such as electron temperature (Te), electron density (ne), ion density (ni), degree of ionization of Ar and degree of dissociation of H2 as a function of hydrogen content in the discharge is studied. Langmuir probe and Optical emission spectroscopy are used to characterize the plasma. On the basis of the different reactions in the gas phase of the magnetron discharge, the variation of plasma parameters and sputtering rate are explained. It is observed that the electron and heavy ion density decline with gradual addition of hydrogen in the discharge. Hydrogen addition significantly changes the degree of ionization of Ar which influences the structural phases of the TiO2 film.

  6. Special features of oxygen distribution in the surface region of steel IOKhN2 under the effect of gas-discharge plasma

    NASA Astrophysics Data System (ADS)

    Nosenko, V. Yu.; Pivovarov, A. L.; Chenakin, S. P.; Cherepin, V. T.

    1996-04-01

    In recent years technological processes and methods of treatment that include the use of low-temperature gas-discharge plasma have become very popular. Ion-plasma technologies are used successfully for cleaning the surface of materials or creating thin-film structures and coatings and for chemicothermal treatment (nitriding, siliconizing, boronizing, carburizing, etc.) of various metals and alloys. The effect of the plasma of a gas glow discharge on a solid body can be manifested in a change in the chemical composition of its surface region. This is caused by the introduction of elements from the gas atmosphere into the specimen and by the redistribution of the matrix components in this region. The nature of such a redistribution of the components under the action of a gas-discharge plasma is not completely clear, which, among other reasons, is associated with the insufficiency of experimental and theoretical data on the problem. The present work concerns the causes and possible mechanism of the appearance of an oxygen-rich layer in the near-surface region of steel 10KhN2 after the action of a glow-discharge plasma in He, N2 + 25% H2, and Ar atmospheres. A correct explanation of this phenomenon can have a decisive role in understanding the special features of the diffusion processes occurring in a solid body under the effect of a gas-discharge plasma.

  7. The role of helium metastable states in radio-frequency driven helium-oxygen atmospheric pressure plasma jets: measurement and numerical simulation

    NASA Astrophysics Data System (ADS)

    Niemi, K.; Waskoenig, J.; Sadeghi, N.; Gans, T.; O'Connell, D.

    2011-10-01

    Absolute densities of metastable He(23S1) atoms were measured line-of-sight integrated along the discharge channel of a capacitively coupled radio-frequency driven atmospheric pressure plasma jet operated in technologically relevant helium-oxygen mixtures by tunable diode-laser absorption spectroscopy. The dependences of the He(23S1) density in the homogeneous-glow-like α-mode plasma with oxygen admixtures up to 1% were investigated. The results are compared with a one-dimensional numerical simulation, which includes a semi-kinetical treatment of the pronounced electron dynamics and the complex plasma chemistry (in total 20 species and 184 reactions). Very good agreement between measurement and simulation is found. The main formation mechanisms for metastable helium atoms are identified and analyzed, including their pronounced spatio-temporal dynamics. Penning ionization through helium metastables is found to be significant for plasma sustainment, while it is revealed that helium metastables are not an important energy carrying species into the jet effluent and therefore will not play a direct role in remote surface treatments.

  8. Differentiating the role of lithium and oxygen in retaining deuterium on lithiated graphite plasma-facing components

    SciTech Connect

    C.N. Taylor; J. P. Allain; P. S. Krstic; J. Dadras; C. H. Skinner; K. E. Luitjohan

    2013-11-01

    Laboratory experiments have been used to investigate the fundamental interactions responsible for deuterium retention in lithiated graphite. Oxygen was found to be present and play a key role in experiments that simulated NSTX lithium conditioning, where the atomic surface concentration can increase to >40% when deuterium retention chemistry is observed. Quantum-classical molecular dynamic simulations elucidated this oxygen-deuterium effect and showed that oxygen retains significantly more deuterium than lithium in a simulated matrix with 20% lithium, 20% oxygen, and 60% carbon. Simulations further show that deuterium retention is even higher when lithium is removed from the matrix. Experiments artificially increased the oxygen content in graphite to approximately 16% and then bombarded with deuterium. XPS showed depletion of the oxygen and no enhanced deuterium retention, thus demonstrating that lithium is essential in retaining the oxygen that thereby retains deuterium.

  9. Differentiating the role of lithium and oxygen in retaining deuterium on lithiated graphite plasma-facing components

    SciTech Connect

    Taylor, C. N.; Allain, J. P.; Luitjohan, K. E.; Krstic, P. S.; Dadras, J.; Skinner, C. H.

    2014-05-15

    Laboratory experiments have been used to investigate the fundamental interactions responsible for deuterium retention in lithiated graphite. Oxygen was found to be present and play a key role in experiments that simulated NSTX lithium conditioning, where the atomic surface concentration can increase to >40% when deuterium retention chemistry is observed. Quantum-classical molecular dynamic simulations elucidated this oxygen-deuterium effect and showed that oxygen retains significantly more deuterium than lithium in a simulated matrix with 20% lithium, 20% oxygen, and 60% carbon. Simulations further show that deuterium retention is even higher when lithium is removed from the matrix. Experiments artificially increased the oxygen content in graphite to ∼16% and then bombarded with deuterium. X-ray photoelectron spectroscopy showed depletion of the oxygen and no enhanced deuterium retention, thus demonstrating that lithium is essential in retaining the oxygen that thereby retains deuterium.

  10. Photosensitized damage inflicted on plasma membranes of live cells by an extracellular generator of singlet oxygen--a linear dependence of a lethal dose on light intensity.

    PubMed

    Zarębski, Mirosław; Kordon, Magdalena; Dobrucki, Jurek W

    2014-01-01

    We describe a study of the influence of a dose rate, i.e. light intensity or photon flux, on the efficiency of induction of a loss of integrity of plasma membranes of live cells in culture. The influence of a photon flux on the size of the light dose, which was capable of causing lethal effects, was measured in an experimental system where singlet oxygen was generated exclusively outside of live cells by ruthenium(II) phenantroline complex. Instantaneous, sensitive detection of a loss of integrity of a plasma membrane was achieved by fluorescence confocal imaging of the entry of this complex into a cell interior. We demonstrate that the size of the lethal dose of light is directly proportional to the intensity of the exciting light. Thus, the probability of a photon of the exciting light inflicting photosensitized damage on plasma membranes diminishes with increasing density of the incident photons.

  11. Direct Water-treatment by DC Driven Micro-hollow Cathode Discharge

    NASA Astrophysics Data System (ADS)

    Yamatake, Atsushi; Yasuoka, Koichi; Ishii, Shozo

    Direct water-treatment method by O and OH radicals has been developed using DC driven atmospheric micro-plasmas operated in fast gas flow conditions. Over atmospheric pressure gas of pure oxygen, moist oxygen or water vapor passed through a small cavity of 200 μm in diameter where micro-plasmas were generated. The resident time of the feed gas within the cavity was around microsecond. The emission spectra of OH radical were observed. The oxidizing effects depend on the gas flow rate from the decolorizing rate for a food color. In comparison with the ozone decolorization, the fast gas-flow conditions are inevitable for utilizing short-lived radicals such as O and OH, to react with the water directly.

  12. Oxygen depth profiling by resonant backscattering and glow discharge optical emission spectroscopy of Ti-6Al-4V alloy oxidized by ion implantation and plasma based treatment

    NASA Astrophysics Data System (ADS)

    Nsengiyumva, S.; Topic, M.; Pichon, L.; Comrie, C. M.; Mtshali, C.

    2016-10-01

    Oxygen depth profiling by means of 16O(α,α)16O backscattering and glow discharge optical emission spectroscopy (GDOES) was investigated in two different sets of Ti-6Al-4V samples. The first set was made of Ti-6Al-4V samples implanted at room temperature and 550 °C with 50 and 150 keV O+ ions at fluences ranging from 1.5 × 1017 to 6.0 × 1017 ions/cm2. The second set consisted of Ti-6Al-4V samples treated at 550 °C for 7 h and 24 h under low pressure (8 Pa) oxygen, eventually with RF plasma activation. These results are part of a wider investigation on Ti-6Al-4V motivated by recent publications which have shown that an oxide layer can enhance hydrogen absorption and can then promote Ti-6Al-4V alloys as efficient hydrogen storage materials. The results obtained by the two characterization techniques were compared and discussed, enabling to adjust the dependence to the oxygen concentration of the sputtering rates to be used in the time-to-depth transformation required in GDOES analysis. Considering the low thickness of oxidized alloy, usual procedures employed in GDOES depth calculation were indeed not adapted. Once calibrated thanks to the resonant RBS, GDOES can then be easily employed as fast characterization of oxidized and/or hydrogenated surface of Ti-6Al-4V. The obtained results show that the oxygen content into the surface oxidized layer slightly increases in samples implanted at higher fluence and higher temperature. However the overall oxidized layer thickness (<200 nm) remains within the projected ion depth range and is not significantly increased by thermal diffusion at 550 °C. Taken into account the initial oxide layer, the incorporated oxygen quantity mainly corresponds to the implanted fluence but it can be slightly higher with 550 °C implantation, indicating a slight additional oxidation by residual oxygen or surface contamination. The oxygen penetrations and contents in samples oxidized by thermally activated diffusion treatments were more

  13. Effect of oxygen plasma treatment on the electrochemical performance of the rayon and polyacrylonitrile based carbon felt for the vanadium redox flow battery application

    NASA Astrophysics Data System (ADS)

    Dixon, D.; Babu, D. J.; Langner, J.; Bruns, M.; Pfaffmann, L.; Bhaskar, A.; Schneider, J. J.; Scheiba, F.; Ehrenberg, H.

    2016-11-01

    Oxygen plasma treatment was applied on commercially available graphite felt electrodes based on rayon (GFA) and polyacrylonitrile (GFD). The formation of functional groups on the surface of the felt was confirmed by X-ray photoelectron spectroscopy measurements. The BET studies of the plasma treated electrodes showed no significant increase in surface area for both the rayon as well as the PAN based felts. Both plasma treated electrodes showed significantly enhanced V3+/V2+ redox activity compared to the pristine electrodes. Since an increase of the surface area has been ruled out for plasma treated electrode the enhanced activity could be attributed to surface functional groups. Interestingly, plasma treated GFD felts showed less electrochemical activity towards V5+/V4+ compared to the pristine electrode. Nevertheless, an overall increase of the single cell performance was still observed as the negative electrode is known to be the performance limiting electrode. Thus, to a great extent the present work helps to preferentially understand the importance of functional groups on the electrochemical activity of negative and positive redox reaction. The study emphasizes the need of highly active electrodes especially at the negative electrode side as inactive electrodes can still facilitate hydrogen evolution and degrade the electrolyte in VRFBs.

  14. Influence of operating parameters on surface properties of RF glow discharge oxygen plasma treated TiO₂/PET film for biomedical application.

    PubMed

    Pandiyaraj, K Navaneetha; Deshmukh, R R; Mahendiran, R; Su, Pi-G; Yassitepe, Emre; Shah, Ismat; Perni, Stefano; Prokopovich, Polina; Nadagouda, Mallikarjuna N

    2014-03-01

    In this paper, a thin transparent titania (TiO2) film was coated on the surface of flexible poly(ethylene terephthalate) (PET) film using the sol-gel method. The surface properties of the obtained TiO2/PET film were further improved by RF glow discharge oxygen plasma as a function of exposure time and discharge power. The changes in hydrophilicity of TiO2/PET films were analyzed by contact angle measurements and surface energy. The influence of plasma on the surface of the TiO2/PET films was analyzed by atomic force microscopy (AFM) as well as the change in chemical state and composition that were investigated by X-ray photo electron spectroscopy (XPS). The cytotoxicity of the TiO2/PET films was analyzed using human osteoblast cells and the bacterial eradication behaviors of TiO2/PET films were also evaluated against Staphylococcus bacteria. It was found that the surface roughness and incorporation of oxygen containing polar functional groups of the plasma treated TiO2/PET films increased substantially as compared to the untreated one. Moreover the increased concentration of Ti(3+) on the surface of plasma treated TiO2/PET films was due to the transformation of chemical states (Ti(4+)→Ti(3+)). These morphological and chemical changes are responsible for enhanced hydrophilicity of the TiO2/PET films. Furthermore, the plasma treated TiO2/PET film exhibited no citotoxicity against osteoblast cells and antibacterial activity against Staphylococcus bacteria which can find application in manufacturing of biomedical devices.

  15. Plasma reactive oxygen metabolites and non-enzymatic antioxidant capacity are not affected by an acute increase of metabolic rate in zebra finches.

    PubMed

    Beamonte-Barrientos, Rene; Verhulst, Simon

    2013-07-01

    Understanding the sources of variation in oxidative stress level is a challenging issue due to the implications of oxidative stress for late age diseases, longevity and life-history trade-offs. Reactive oxygen species that cause oxidative stress are mostly a by-product of energy metabolism and it is therefore often assumed that oxidative stress is proportional to energy consumption. In mammals, an increased metabolic rate induced by cold exposure generally increases oxidative stress. However, compared to mammals, birds generate fewer free radicals per ATP produced and hence it is not obvious that, in birds, a cold-induced increase of metabolic rate increase oxidative stress. We tested whether cold-induced increase in metabolic rate increased oxidative stress in zebra finches by exposing individuals to cold and warm overnight temperatures. We registered metabolic rate and plasma levels of non-enzymatic antioxidants and reactive oxygen metabolites (ROMs), a measure of oxidative damage. Metabolic rate was on average 88 % higher in cold compared to warm temperature, with females being stronger affected than males. However, temperature had no effect on plasma antioxidants or our measure of oxidative damage. Middle-age birds had higher levels of plasma antioxidants than younger and older birds, but age was unrelated to ROMs. Birds showed repeatability of plasma ROMs across temperatures but not of non-enzymatic antioxidants. In contrast to similar studies in mammals, our results do not show evidence of increased oxidative stress in plasma after an acute cold-induced increase of metabolic rate but research in more bird species is needed to assess the generality of this pattern.

  16. Impact of oxygen plasma postoxidation process on Al2O3/n-In0.53Ga0.47As metal-oxide-semiconductor capacitors

    NASA Astrophysics Data System (ADS)

    Lechaux, Y.; Fadjie-Djomkam, A. B.; Bollaert, S.; Wichmann, N.

    2016-09-01

    Capacitance-voltage (C-V) measurements and x-ray photoelectron spectroscopy (XPS) analysis were performed in order to investigate the effect of a oxygen (O2) plasma after oxide deposition on the Al2O3/n-In0.53Ga0.47As metal-oxide-semiconductor structure passivated with ammonia NH4OH solution. From C-V measurements, an improvement of charge control is observed using the O2 plasma postoxidation process on In0.53Ga0.47As, while the minimum of interface trap density remains at a good value lower than 1 × 1012 cm-2 eV-1. From XPS measurements, we found that NH4OH passivation removes drastically the Ga and As native oxides on the In0.53Ga0.47As surface and the O2 plasma postoxidation process enables the reduction of interface re-oxidation after post deposition annealing (PDA) of the oxide. The advanced hypothesis is the formation of interfacial barrier between Al2O3 and In0.53Ga0.47As which prevents the diffusion of oxygen species into the semiconductor surface during PDA.

  17. Efficient dc-to-dc converter

    NASA Technical Reports Server (NTRS)

    Black, J. M.

    1978-01-01

    Circuit consists of chopper section which converts input dc to square wave, followed by bridge-rectifier stage. Chopper gives nearly-ideal switching characteristics, and bridge uses series of full-wave stages rather than less-efficient half-wave rectifiers found in previous circuits. Special features of full-wave circuit allow redundant components to be eliminated, lowering parts count. Circuit can also be adapted for use as dc-to-dc converter or as combination dc-and-ac source.

  18. DC/DC Converter Stability Testing Study

    NASA Technical Reports Server (NTRS)

    Wang, Bright L.

    2008-01-01

    This report presents study results on hybrid DC/DC converter stability testing methods. An input impedance measurement method and a gain/phase margin measurement method were evaluated to be effective to determine front-end oscillation and feedback loop oscillation. In particular, certain channel power levels of converter input noises have been found to have high degree correlation with the gain/phase margins. It becomes a potential new method to evaluate stability levels of all type of DC/DC converters by utilizing the spectral analysis on converter input noises.

  19. Model polymer etching and surface modification by a time modulated RF plasma jet: role of atomic oxygen and water vapor

    NASA Astrophysics Data System (ADS)

    Luan, P.; Knoll, A. J.; Wang, H.; Kondeti, V. S. S. K.; Bruggeman, P. J.; Oehrlein, G. S.

    2017-01-01

    The surface interaction of a well-characterized time modulated radio frequency (RF) plasma jet with polystyrene, poly(methyl methacrylate) and poly(vinyl alcohol) as model polymers is investigated. The RF plasma jet shows fast polymer etching but mild chemical modification with a characteristic carbonate ester and NO formation on the etched surface. By varying the plasma treatment conditions including feed gas composition, environment gaseous composition, and treatment distance, we find that short lived species, especially atomic O for Ar/1% O2 and 1% air plasma and OH for Ar/1% H2O plasma, play an essential role for polymer etching. For O2 containing plasma, we find that atomic O initiates polymer etching and the etching depth mirrors the measured decay of O atoms in the gas phase as the nozzle-surface distance increases. The etching reaction probability of an O atom ranging from 10-4 to 10-3 is consistent with low pressure plasma research. We also find that adding O2 and H2O simultaneously into Ar feed gas quenches polymer etching compared to adding them separately which suggests the reduction of O and OH density in Ar/O2/H2O plasma.

  20. Sapphire substrate-induced effects in VO{sub 2} thin films grown by oxygen plasma-assisted pulsed laser deposition

    SciTech Connect

    Skuza, J. R. E-mail: apradhan@nsu.edu; Scott, D. W.; Pradhan, A. K. E-mail: apradhan@nsu.edu

    2015-11-21

    We investigate the structural and electronic properties of VO{sub 2} thin films on c-plane sapphire substrates with three different surface morphologies to control the strain at the substrate-film interface. Only non-annealed substrates with no discernible surface features (terraces) provided a suitable template for VO{sub 2} film growth with a semiconductor-metal transition (SMT), which was much lower than the bulk transition temperature. In addition to strain, oxygen vacancy concentration also affects the properties of VO{sub 2}, which can be controlled through deposition conditions. Oxygen plasma-assisted pulsed laser deposition allows favorable conditions for VO{sub 2} film growth with SMTs that can be easily tailored for device applications.

  1. In Situ Control of Oxygen Vacancies in TaOx Thin Films via Plasma-Enhanced Atomic Layer Deposition for Resistive Switching Memory Applications.

    PubMed

    Egorov, Konstantin V; Kuzmichev, Dmitry S; Chizhov, Pavel S; Lebedinskii, Yuri Yu; Hwang, Cheol Seong; Markeev, Andrey M

    2017-04-06

    The plasma-enhanced atomic layer deposition (PEALD) process using Ta(OC2H5)5 as a Ta precursor and plasma-activated hydrogen as a reactant for the deposition of TaOx films with a controllable concentration of oxygen vacancies (VO) is reported herein. The VO concentration control was achieved by varying the hydrogen volume fraction of the hydrogen-argon mixture in the plasma, allowing the control of the leakage current density in the tantalum oxide films within the range of 5 orders of magnitude compared with the Ta2O5 film grown via thermal ALD using the identical Ta precursor and H2O. Temperature-dependent current-voltage measurements combined with Poole-Frenkel emission modeling demonstrated that the bulk trap depth decreases with the increasing hydrogen volume fraction, which could be attributed to the increase of the VO concentration. The possible chemical change in the PEALD TaOx films grown under different hydrogen volume fractions was confirmed by the in situ X-ray photoelectron spectroscopy (XPS) measurements of the Ta 4f core and valence band spectra. The comparison of the XPS-measured nonstoichiometry and the secondary ion mass spectrometry analysis of the hydrogen content allowed this study to conclude that the nonstoichiometry is largely related to the formation of Ta-VO sites rather than of Ta-H sites. Such oxygen-deficient TaOx layers were studied for application as an oxygen-deficient layer in a resistance switching random access memory stack (Ta2O5/TaOx) where the actual switching occurred within the stoichiometric Ta2O5 layer. The bilayer memory stack showed reliable resistance switching up to ∼10(6) switching cycles, whereas the single-layer Ta2O5 memory showed only several hundred switching cycles.

  2. Quantitative Determination of Density of Ground State Atomic Oxygen from Both TALIF and Emission Spectroscopy in Hot Air Plasma Generated by Microwave Resonant Cavity

    NASA Astrophysics Data System (ADS)

    Marchal, F.; Yousfi, M.; Merbahi, N.; Wattieaux, G.; Piquemal, A.

    2016-03-01

    Two experimental techniques have been used to quantify the atomic oxygen density in the case of hot air plasma generated by a microwave (MW) resonant cavity. The latter operates at a frequency of 2.45 GHz inside a cell of gas conditioning at a pressure of 600 mbar, an injected air flow of 12 L/min and an input MW power of 1 kW. The first technique is based on the standard two photon absorption laser induced fluorescence (TALIF) using xenon for calibration but applied for the first time in the present post discharge hot air plasma column having a temperature of about 4500 K near the axis of the nozzle. The second diagnostic technique is an actinometry method based on optical emission spectroscopy (OES). In this case, we compared the spectra intensities of a specific atomic oxygen line (844 nm) and the closest wavelength xenon line (823 nm). The two lines need to be collected under absolutely the same spectroscopic parameters. The xenon emission is due to the addition of a small proportion of xenon (1% Xe) of this chemically inert gas inside the air while a further small quantity of H2 (2%) is also added in the mixture in order to collect OH(A-X) and NH(A-X) spectra without noise. The latter molecular spectra are required to estimate gas and excitation temperatures. Optical emission spectroscopy measurements, at for instance the position z=12 mm on the axis plasma column that leads to a gas measured temperature equal to 3500 K, an excitation temperature of about 9500 K and an atomic oxygen density 2.09×1017±0.2×1017 cm-3. This is in very good agreement with the TALIF measurement, which is equal to 2.0×1017 cm-3.

  3. Influence of Oxygenated Compounds on Reaction Products in a Microwave Plasma Methane Pyrolysis Assembly for Post-Processing of Sabatier Methane

    NASA Technical Reports Server (NTRS)

    Mansell, J. Matthew; Abney, Morgan B.

    2012-01-01

    The state-of-the-art Carbon Dioxide Reduction Assembly (CRA) was delivered to the International Space Station (ISS) in April 2010. The system is designed to accept carbon dioxide from the Carbon Dioxide Removal Assembly and hydrogen from the Oxygen Generation Assembly. The two gases are reacted in the CRA in a Sabatier reactor to produce water and methane. Venting of methane results in an oxygen resupply requirement of about 378 lbs per crew member per year. If the oxygen is supplied as water, the total weight for resupply is about 476 lb per crew member per year. For long-term missions beyond low Earth orbit, during which resupply capabilities will be further limited, recovery of hydrogen from methane is highly desirable. For this purpose, NASA is pursuing development of a Plasma Pyrolysis Assembly (PPA) capable of recovering hydrogen from methane. Under certain conditions, water vapor and carbon dioxide (nominally intended to be separated from the CRA outlet stream) may be present in the PPA feed stream. Thus, testing was conducted in 2010 to determine the effect of these oxygenated compounds on PPA performance, particularly the effect of inlet carbon dioxide and water variations on the PPA product stream. This paper discusses the test set-up, analysis, and results of this testing.

  4. Influence of Oxygenated Compounds on Reaction Products in a Microwave Plasma Methane Pyrolysis Assembly for Post-Processing of Sabatier Methane

    NASA Technical Reports Server (NTRS)

    Mansell, J. Matthew; Abney, Morgan B.; Miller, Lee A.

    2011-01-01

    The state-of-the-art Carbon Dioxide Reduction Assembly (CRA) was delivered to the International Space Station (ISS) in April 2010. The system is designed to accept carbon dioxide from the Carbon Dioxide Removal Assembly and hydrogen from the Oxygen Generation Assembly. The two gases are reacted in the CRA in a Sabatier reactor to produce water and methane. Venting of methane results in an oxygen resupply requirement of about 378 lbs per crew member per year. If the oxygen is supplied as water, the total weight for resupply is about 476 lb per crew member per year. For long-term missions beyond low Earth orbit, during which resupply capabilities will be further limited, recovery of hydrogen from methane is highly desirable. For this purpose, NASA is pursuing development of a Plasma Pyrolysis Assembly (PPA) capable of recovering hydrogen from methane. Under certain conditions, water vapor and carbon dioxide (nominally intended to be separated from the CRA outlet stream) may be present in the PPA feed stream. Thus, testing was conducted in 2010 to determine the effect of these "oxygenated" compounds on PPA performance, particularly the effect of inlet carbon dioxide and water variations on the PPA product stream. This paper discusses the test set-up, analysis, and results of this testing

  5. Impact of interstitial oxygen trapped in silicon during plasma growth of silicon oxy-nitride films for silicon solar cell passivation

    NASA Astrophysics Data System (ADS)

    Saseendran, Sandeep S.; Saravanan, S.; Raval, Mehul C.; Kottantharayil, Anil

    2016-03-01

    Low temperature oxidation of silicon in plasma ambient is a potential candidate for replacing thermally grown SiO2 films for surface passivation of crystalline silicon solar cells. In this work, we report the growth of silicon oxy-nitride (SiOxNy) film in N2O plasma ambient at 380 °C. However, this process results in trapping of interstitial oxygen within silicon. The impact of this trapped interstitial oxygen on the surface passivation quality is investigated. The interstitial oxygen trapped in silicon was seen to decrease for larger SiOxNy film thickness. Effective minority carrier lifetime (τeff) measurements on n-type float zone silicon wafers passivated by SiOxNy/silicon nitride (SiNv:H) stack showed a decrease in τeff from 347 μs to 68 μs, for larger SiOxNy film thickness due to degradation in interface properties. From high frequency capacitance-voltage measurements, it was concluded that the surface passivation quality was governed by the interface parameters (fixed charge density and interface state density). High temperature firing of the SiOxNy/SiNv:H stack resulted in a severe degradation in τeff due to migration of oxygen across the interface into silicon. However, on using the SiOxNy/SiNv:H stack for emitter surface passivation in screen printed p-type Si solar cells, an improvement in short wavelength response was observed in comparison to the passivation by SiNv:H alone, indicating an improvement in emitter surface passivation quality.

  6. Humidity sensors applicative characteristics of granularized and porous Bi2O3 thin films prepared by oxygen plasma-assisted pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Tudorache, Florin; Petrila, Iulian; Condurache-Bota, Simona; Constantinescu, Catalin; Praisler, Mirela

    2015-01-01

    Pulsed laser ablation of pure bismuth targets in a plasma discharge followed by thermal treatment as preparation method for humidity high-sensitive bismuth trioxide thin films deposited onto Si/Pt substrates were analyzed. Several thin films were deposited at different substrate temperatures during the pulsed laser deposition namely between 300 °C and 600 °C. Near to the electrical investigation, the structure and the morphology of the films as keys features for water adsorption are thoroughly investigated and correlated with their sensitivity as humidity sensors. Thus, it has been found that strong granularized Bi2O3 thin films obtained through oxygen plasma-assisted pulsed laser deposition onto Si/Pt substrate at 500 °C provide the most interesting humidity sensing characteristics.

  7. TiC supported Pt-Ir electrocatalyst prepared by a plasma process for the oxygen electrode in unitized regenerative fuel cells

    NASA Astrophysics Data System (ADS)

    Sui, Sheng; Ma, Lirong; Zhai, Yuchun

    Unitized regenerative fuel cells (URFCs) have become more attractive for some time due to its potentially wide energy storage application such as in fields of space and renewable energy. In this study, TiC supported Pt-Ir electrocatalysts (Pt-Ir/TiC) for oxygen electrode in URFCs were synthesized, respectively, by chemical reduction process and plasma reduction process. Their physical and electrochemical properties are characterized and compared using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), cyclic voltammogram (CV), potentiostatic technique, and electrochemical impedance spectroscopy (EIS). The results from XRD, XPS and TEM demonstrate that the plasma process gives a finer metal crystals and higher metal dispersion on the TiC support. The CV, polarization, potentiostatic and EIS results show that the Pt-Ir/TiC electrocatalyst prepared by the plasma reduction process is obviously more active than that by the chemical reduction process, in agreement with the above metal-dispersion observations. The plasma process is a promising way for the preparation of supported electrocatalysts.

  8. Oxygen Gas Barrier Properties of Hydrogenated Amorphous Carbon Thin Films Deposited with a Pulse-Biased Inductively Coupled Plasma Chemical Vapor Deposition Method

    NASA Astrophysics Data System (ADS)

    Baek, Sang-min; Shirafuji, Tatsuru; Cho, Sung-pyo; Saito, Nagahiro; Takai, Osamu

    2010-08-01

    Hydrogenated amorphous carbon (a-C:H) films have been deposited on poly(ethylene terephthalate) (PET) films with an pulse-biased inductively coupled plasma chemical vapor deposition method using CH4 and C2H2 gases. We have investigated the effects of the pulse-bias frequency on the oxygen transmission rate (OTR) of the a-C:H-coated PET sample, and discussed relationship between the OTR characteristics and the structure of the films based on the results of Raman and infrared absorption spectroscopy. In case of CH4 plasmas, the OTR of the sample has been reduced down to 1.12 cm3/(m2·day·atm) by increasing the bias-frequency to 2 kHz, and the structure of the a-C:H films has been modified from polymer-like to tetrahedral one. In case of C2H2 plasmas, the OTR of the samples has been 1.18 cm3/(m2·day·atm) with the lower bias frequency of 0.5 kHz, and has not shown strong dependence on the pulse-bias frequency. This has been explained by the fact that the films prepared with C2H2 plasma can be modified to tetrahedral structures by applying the bias with the lower frequency.

  9. Proceedings of the Conference on the Numerical Simulation of Plasmas (4th) Held at the Naval Research Laboratory, Washington, D.C. on 2, 3 November 1970

    DTIC Science & Technology

    1971-07-19

    computers than the latter and considerably shortens the lead time to results. In other words it is often better to use brute force subtly in computational...code ’ . Every effort has been made to make the code efficient and accurate. With the FFT subroutine in assembly language and the tridiagonal...being coded 52 L m .^^— — „,—....., Relatives tic Plasma Simulation in PL360, a symbolic assembly language for 360 computers, and is being

  10. Towards highly stable aqueous dispersions of multi-walled carbon nanotubes: the effect of oxygen plasma functionalization.

    PubMed

    Garzia Trulli, Marta; Sardella, Eloisa; Palumbo, Fabio; Palazzo, Gerardo; Giannossa, Lorena Carla; Mangone, Annarosa; Comparelli, Roberto; Musso, Simone; Favia, Pietro

    2017-04-01

    In order to improve the dispersion of multi-walled carbon nanotubes (MWCNTs) in aqueous media, their surface functionalization was carried out in O2-fed low-pressure plasmas. Differently from what can be found in the literature of this field, homogeneous functionalization was achieved by generating the plasma inside vials containing the nanotube powders properly stirred. Experimental parameters, such as input power, treatment time and pressure, were varied to investigate their influence on the process efficiency. A detailed characterization of the plasma treated nanotubes, dry and in aqueous suspension, was carried out with a multi-diagnostic analytical approach, to evaluate their surface chemical properties, morphology, structural integrity and stability in the colloidal state. The plasma grafting of polar ionizable (e.g. acid) groups has been proved to successfully limit the agglomeration of MWCNTs and to produce nanotubes suspensions that are stable for one month and more in water.

  11. Modification of the PTFE wettability by oxygen plasma treatments: influence of the operating parameters and investigation of the ageing behaviour

    NASA Astrophysics Data System (ADS)

    Zanini, Stefano; Barni, Ruggero; Della Pergola, Roberto; Riccardi, Claudia

    2014-08-01

    The effects of O2 plasma treatments on poly(tetrafluoroethylene) (PTFE) sheets are deeply investigated. The chemical modifications owing to the plasma treatment are studied by means of attenuated total reflectance Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy (XPS), while the surface topography of the plasma-treated samples is assessed by atomic force microscopy (AFM) analyses. Results are correlated with the wettability characteristics of the plasma-modified PTFE sheets, which is studied by means of contact angle (CA) and roll-off angle measurements. Finally, the ageing of the plasma-treated surfaces is investigated. The RF power input and the treatment time influence the chemical/morphological characteristics and the wettability of the plasma-treated samples. PTFE samples treated at low-power input (up to 50 W) are more hydrophilic than the untreated one. The XPS analysis reveals that OH functionalization of the outermost layers of polymeric chains decreases by increasing the RF power input, and dynamic CAs gradually increase. The AFM analysis shows a strong increase in the surface roughness as a consequence of the differential etching of the PTFE surface for samples treated at power inputs ⩾100 W, with formation of globular structures. XPS analyses of the aged samples reveal a post-plasma oxidation. However, the dynamic CAs measured after 30 days are greater than those measured immediately after treatment, and for power input ⩾100 W the aged plasma-treated PTFE surfaces are super-hydrophobic. This result suggests a decrease in the surface density of the exposed hydroxyl groups during ageing time, as a consequence of surface adaptation.

  12. Treatment surfaces with atomic oxygen excited in dielectric barrier discharge plasma of O{sub 2} admixed to N{sub 2}

    SciTech Connect

    Shun'ko, E. V.; Belkin, V. S.

    2012-06-15

    This paper describes the increase in surface energy of substrates by their treatment with gas composition generated in plasmas of DBD (Dielectric Barrier Discharge) in O2 admixed with N2. Operating gas dissociation and excitation was occurred in plasmas developed in two types of reactors of capacitively-coupled dielectric barrier configurations: coaxial cylindrical, and flat rectangular. The coaxial cylindrical type comprised an inner cylindrical electrode encapsulated in a ceramic sheath installed coaxially inside a cylindrical ceramic (quartz) tube passing through an annular outer electrode. Components of the flat rectangular type were a flat ceramic tube of a narrow rectangular cross section supplied with two flat electrodes mounted against one another outside of the long parallel walls of this tube. The operating gas, mixture of N{sub 2} and O{sub 2}, was flowing in a completely insulated discharge gap formed between insulated electrodes of the devices with an average velocity of gas inlet of about 7 to 9 m/s. Dielectric barrier discharge plasma was excited in the operating gaps with a bipolar pulse voltage of about 6 kV for 2 ms at 50 kHz repetition rate applied to the electrodes of the coaxial device, and of about 14 kV for 7 ms at 30 kHz repetition rate for the flat linear device. A lifetime of excited to the 2s{sup 2}2p{sup 4}({sup 1}S{sub 0}) state in DBD plasma and streaming to the surfaces with a gas flow atomic oxygen, responsible presumably for treating surfaces, exceeded 10 ms in certain cases, that simplified its separation from DBD plasma and delivery to substrates. As it was found in particular, surfaces of glass and some of polymers revealed significant enhancement in wettability after treatment.

  13. DC source assemblies

    DOEpatents

    Campbell, Jeremy B; Newson, Steve

    2013-02-26

    Embodiments of DC source assemblies of power inverter systems of the type suitable for deployment in a vehicle having an electrically grounded chassis are provided. An embodiment of a DC source assembly comprises a housing, a DC source disposed within the housing, a first terminal, and a second terminal. The DC source also comprises a first capacitor having a first electrode electrically coupled to the housing, and a second electrode electrically coupled to the first terminal. The DC source assembly further comprises a second capacitor having a first electrode electrically coupled to the housing, and a second electrode electrically coupled to the second terminal.

  14. Effect of oxygen plasma treatment on surface charge and wettability of PVC blood bag—In vitro assay

    NASA Astrophysics Data System (ADS)

    Khorasani, M. T.; Mirzadeh, H.

    2007-06-01

    Wettability and zeta potential studies were performed to characterize the hydrophobicity and surface charge of PVC blood bag samples and evaluate the effect of these properties on fibroblast cells growth. The surface properties of PVC and plasma treated PVC were compared by water drop contact angle and zeta potential measurement. Light microscopy was used to study the behavior of cell attachment and growth on these surfaces. Water drop contact angle measurement shows that the plasma treated PVC becomes more hydrophilic and wettability increased. Zeta potential and in vitro cell culture measurements noticed that the plasma treated PVC surface is more negatively charge and consequently attachment of the L929 fibroblast cells decreased on this surface.

  15. Cold streams of ionospheric oxygen in the plasma sheet during the CDAW 6 event of March 22, 1979

    NASA Technical Reports Server (NTRS)

    Orsini, S.; Amata, E.; Candidi, M.; Balsiger, H.; Stokholm, M.; Huang, C.; Lennartsson, W.; Lindqvist, P.-A.

    1985-01-01

    During magnetospheric substorm events, the plasma and ion composition experiments in the ISEE-1 and 2 satellites detected cold ionospheric O+ streams, moving tailwards in the near earth magnetotail. Flow is parallel to the magnetic field lines, with drift velocity in agreement with the electric field topology obtained by mapping the model ionospheric field along the magnetic field lines. Fluctuations of the flow velocity of the streams can be related to magnetotail movements. Oscillations of the flow direction and speed with periods ranging from 5 to 10 min that suggest the presence of waves are observed. The streams are observed at all distances between 15 and 6 Re from the earth. When averaged over 360 deg, the streams show up as a low energy peak, superimposed on the distribution of isotropic plasma sheet ions. This double-peak structure of the energy spectrum seems typical of the disturbed plasma sheet.

  16. Cold streams of ionospheric oxygen in the plasma sheet during the CDAW 6 event of March 22, 1979

    SciTech Connect

    Orsini, S.; Amata, E.; Candidi, M.; Balsiger, H.; Stokholm, M.; Huang, C.; Lennartsson, W.; Lindqvist, P.A.

    1985-05-01

    During magnetospheric substorm events, the plasma and ion composition experiments in the ISEE-1 and 2 satellites detected cold ionospheric O+ streams, moving tailwards in the near earth magnetotail. Flow is parallel to the magnetic field lines, with drift velocity in agreement with the electric field topology obtained by mapping the model ionospheric field along the magnetic field lines. Fluctuations of the flow velocity of the streams can be related to magnetotail movements. Oscillations of the flow direction and speed with periods ranging from 5 to 10 min that suggest the presence of waves are observed. The streams are observed at all distances between 15 and 6 Re from the earth. When averaged over 360 deg, the streams show up as a low energy peak, superimposed on the distribution of isotropic plasma sheet ions. This double-peak structure of the energy spectrum seems typical of the disturbed plasma sheet. 25 references.

  17. Cold streams of ionospheric oxygen in the plasma sheet during the CDAW-6 event of March 22, 1979

    NASA Technical Reports Server (NTRS)

    Orsini, S.; Amata, E.; Candidi, M.; Balsiger, H.; Stokholm, M.; Huang, C. Y.; Lennartsson, W.; Lindqvist, P. A.

    1983-01-01

    During magnetospheric substorm events, the plasma and ion composition experiments in the ISEE-1 and 2 satellites detected cold ionospheric O+ streams, moving tailwards in the near Earth magnetotail. Flow is parallel to the magnetic field lines, with drift velocity in agreement with the electric field topology obtained by mapping the model ionospheric field along the magnetic field lines. Fluctuations of the flow velocity of the streams can be related to magnetotail movements. Oscillations of the flow direction and speed with periods ranging from 5 to 10 min that suggest the presence of waves are observed. The streams are observed at all distances between 15 and 6 Re from the Earth. When averaged over 360 deg, the streams show up as a low energy peak, superimposed on the distribution of isotropic plasma sheet ions. This double-peak structure of the energy spectrum seems typical of the disturbed plasma sheet.

  18. The emerging role of reactive oxygen and nitrogen species in redox biology and some implications for plasma applications to medicine and biology

    NASA Astrophysics Data System (ADS)

    Graves, David B.

    2012-07-01

    Reactive oxygen species (ROS) and the closely related reactive nitrogen species (RNS) are often generated in applications of atmospheric pressure plasmas intended for biomedical purposes. These species are also central players in what is sometimes referred to as ‘redox’ or oxidation-reduction biology. Oxidation-reduction biochemistry is fundamental to all of aerobic biology. ROS and RNS are perhaps best known as disease-associated agents, implicated in diabetes, cancer, heart and lung disease, autoimmune disease and a host of other maladies including ageing and various infectious diseases. These species are also known to play active roles in the immune systems of both animals and plants and are key signalling molecules, among many other important roles. Indeed, the latest research has shown that ROS/RNS play a much more complex and nuanced role in health and ageing than previously thought. Some of the most potentially profound therapeutic roles played by ROS and RNS in various medical interventions have emerged only in the last several years. Recent research suggests that ROS/RNS are significant and perhaps even central actors in the actions of antimicrobial and anti-parasite drugs, cancer therapies, wound healing therapies and therapies involving the cardiovascular system. Understanding the ways ROS/RNS act in established therapies may help guide future efforts in exploiting novel plasma medical therapies. The importance of ROS and RNS to plant biology has been relatively little appreciated in the plasma biomedicine community, but these species are just as important in plants. It appears that there are opportunities for useful applications of plasmas in this area as well.

  19. Effect of gamma radiation on resting B lymphocytes. I. Oxygen-dependent damage to the plasma membrane results in increased permeability and cell enlargement

    SciTech Connect

    Ashwell, J.D.; Schwartz, R.H.; Mitchell, J.B.; Russo, A.

    1986-05-15

    Although the susceptibility of resting B lymphocytes to radiation-induced interphase death is well known, the mechanism by which this occurs is not understood. In this report, we use three measures of plasma membrane integrity (increase in cell volume, uptake of trypan blue, and release of /sup 51/Cr) to assess the effect of radiation on the resting B cell plasma membrane. The delivery of 500 to 1000 rad caused the majority of resting B cells to enlarge slightly, whereas 3000 rad caused virtually all of the cells to approximately double in size within 3 to 4 hr. Measurement of the release of /sup 51/Cr from resting B cells revealed a similar relationship between the dose of radiation and the loss of radioactive label. Trypan blue exclusion was also found to diminish as a function of radiation dose. An analysis of a variety of lymphoid cells suggested that sensitivity to the membrane damaging effects of gamma radiation was in the order of resting B cells greater than resting T cells greater than a long-term L3T4+ T cell clone greater than a B cell lymphoma. LPS-induced B cell blasts treated with 3000 rad were equivalent to 1000 rad-treated resting B cells. The effects of the gamma radiation could be ameliorated by excluding oxygen at the time of irradiation, or by adding the free radical scavenging agent cysteamine. These data are compatible with the hypothesis that gamma radiation results in damage to the plasma membrane of resting lymphocytes via the generation of highly reactive free radical species. This damage is reflected in a rapid increase in plasma membrane permeability and swelling of the cells, and may play a major role in causing interphase death.

  20. Recombination of atomic oxygen on α-Al 2O 3 at high temperature under air microwave-induced plasma

    NASA Astrophysics Data System (ADS)

    Balat-Pichelin, M.; Bedra, L.; Gerasimova, O.; Boubert, P.

    2007-11-01

    New ceramic materials are necessary for the design of primary heat shields for future reusable space vehicles re-entering atmospheric planet. During the re-entry phase on earth, one of the most important phenomena occurring on the heat shield is the recombination of atomic species and among them atomic oxygen. The recombination of atomic oxygen is catalyzed by the material of the heat shield. This paper presents some experimental results for the recombination coefficient γ and the thermal flux of recombination transferred to the material in the surface-catalyzed recombination of oxygen atoms based on experiments performed on the MESOX set-up using optical emission spectroscopy, actinometry and calorimetry techniques. Experimental results on the recombination coefficient are presented for three types of α-Al 2O 3 in the temperature range 900-2400 K for 300 Pa total air pressure. The thermal flux of recombination is given for only two representative samples. These three alumina differ essentially by their content of sintering additives. Different behaviors of the recombination coefficient versus temperature are observed according to the impurity level of the α-alumina.

  1. SELECTIVE REDUCTION OF NOX IN OXYGEN RICH ENVIRONMENTS WITH PLASMA-ASSISTED CATALYSIS: CATALYST DEVELOPMENT AND MECHANISTIC STUDIES

    SciTech Connect

    Peden, C; Barlow, S; Hoard, J; Kwak, J; *Balmer-Millar, M; *Panov, A; Schmieg, S; Szanyi, J; Tonkyn, R

    2003-08-24

    The control of NOx (NO and NO2) emissions from so-called ''lean-burn'' vehicle engines remains a challenge. In recent years, there have been a number of reports that show that a plasma device combined with a catalyst can reduce as high as 90% or more of NOx in simulated diesel and other ''lean-burn'' exhaust. In the case of propylene containing simulated diesel exhaust, the beneficial role of a plasma treatment is now thought to be due to oxidation of NO to NO2, and the formation of partially oxidized hydrocarbons that are more active for the catalytic reduction of NO2 than propylene. Thus, the overall system can be most usefully described as hydrocarbon selective catalytic reduction (SCR) enhanced by 'reforming' the exhaust with a non-thermal plasma (NTP) device. For plasma-enhanced catalysis, both zeolite- and alumina-based materials have shown high activity, albeit in somewhat different temperature ranges, when preceded by an NTP reactor. This paper will briefly describe our research efforts aimed at optimizing the catalyst materials for NTP-catalysis devices based, in part, on our continuing studies of the NTP- and catalytic-reaction mechanisms. Various alkali- and alkaline earth-cation-exchanged Y zeolites have been prepared, their material properties characterized, and they have been tested as catalytic materials for NOx reduction in laboratory NTP-catalysis reactors. Interestingly, NO2 formed in the plasma and not subsequently removed over these catalysts, will back-convert to NO, albeit to varying extents depending upon the nature of the cation. Besides this comparative reactivity, we will also discuss selected synthesis strategies for enhancing the performance of these zeolite-based catalyst materials. A particularly important result from our mechanistic studies is the observation that aldehydes, formed during the plasma treatment of simulated diesel exhaust, are the important species for the reduction of NOx to N2. Indeed, acetaldehyde has been found to

  2. 76 FR 13926 - Airworthiness Directives; The Boeing Company Model DC-8-11, DC-8-12, DC-8-21, DC-8-31, DC-8-32...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-15

    ... Model DC-8-11, DC-8- 12, DC-8-21, DC-8-31, DC-8-32, DC-8-33, DC-8-41, DC-8-42, and DC-8-43 Airplanes; DC-8-50 Series Airplanes; DC-8F-54 and DC-8F-55 Airplanes; DC-8-60 Series Airplanes; DC-8-60F Series Airplanes; DC-8-70 Series Airplanes; and DC-8-70F Series Airplanes AGENCY:......

  3. 75 FR 61989 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-8-31, DC-8-32, DC-8-33, DC-8-41...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-07

    ... Corporation Model DC- 8-31, DC-8-32, DC-8-33, DC-8-41, DC-8-42, and DC-8-43 Airplanes; Model DC-8-50 Series Airplanes; Model DC-8F-54 and DC-8F-55 Airplanes; Model DC-8-60 Series Airplanes; Model DC-8-60F Series Airplanes; Model DC-8- 70 Series Airplanes; and Model DC-8-70F Series Airplanes AGENCY:......

  4. Microfluidic surface-enhanced Raman scattering sensors based on nanopillar forests realized by an oxygen-plasma-stripping-of-photoresist technique.

    PubMed

    Mao, Haiyang; Wu, Wengang; She, Didi; Sun, Gongchen; Lv, Pengpeng; Xu, Jun

    2014-01-15

    A novel surface-enhanced Raman scattering (SERS) sensor is developed for real-time and highly repeatable detection of trace chemical and biological indicators. The sensor consists of a polydimethylsiloxane (PDMS) microchannel cap and a nanopillar forest-based open SERS-active substrate. The nanopillar forests are fabricated based on a new oxygen-plasma-stripping-of-photoresist technique. The enhancement factor (EF) of the SERS-active substrate reaches 6.06 × 10(6) , and the EF of the SERS sensor is about 4 times lower due to the influence of the PDMS cap. However, the sensor shows much higher measurement repeatability than the open substrate, and it reduces the sample preparation time from several hours to a few minutes, which makes the device more reliable and facile for trace chemical and biological analysis.

  5. DC-to-DC switching converter

    NASA Technical Reports Server (NTRS)

    Cuk, Slobodan M. (Inventor); Middlebrook, Robert D. (Inventor)

    1980-01-01

    A dc-to-dc converter having nonpulsating input and output current uses two inductances, one in series with the input source, the other in series with the output load. An electrical energy transferring device with storage, namely storage capacitance, is used with suitable switching means between the inductances to DC level conversion. For isolation between the source and load, the capacitance may be divided into two capacitors coupled by a transformer, and for reducing ripple, the inductances may be coupled. With proper design of the coupling between the inductances, the current ripple can be reduced to zero at either the input or the output, or the reduction achievable in that way may be divided between the input and output.

  6. Oxygen Plasma Treatment and Deposition of CNx on a Fluorinated Polymer Matrix Composite for Improved Erosion Resistance (Preprint)

    DTIC Science & Technology

    2006-12-01

    applications,1 however, their use in propulsion applications such as air intake and compression in jet engines or leading edges of rotor blades, is...characterization chamber. The processing chamber was pumped to a base pressure ≤ 3 x 10-7 Torr , then 40 sccm of UHP oxygen or argon gas was admitted to...protective hard Muratore et. al Submitted to Journal of Vacuum Science and Technology A 10 coatings used on metal alloys in jet engines are on an order of

  7. Monolithic solid electrolyte oxygen pump

    DOEpatents

    Fee, Darrell C.; Poeppel, Roger B.; Easler, Timothy E.; Dees, Dennis W.

    1989-01-01

    A multi-layer oxygen pump having a one-piece, monolithic ceramic structure affords high oxygen production per unit weight and volume and is thus particularly adapted for use as a portable oxygen supply. The oxygen pump is comprised of a large number of small cells on the order of 1-2 millimeters in diameter which form the walls of the pump and which are comprised of thin, i.e., 25-50 micrometers, ceramic layers of cell components. The cell components include an air electrode, an oxygen electrode, an electrolyte and interconnection materials. The cell walls form the passages for input air and for exhausting the oxygen which is transferred from a relatively dilute gaseous mixture to a higher concentration by applying a DC voltage across the electrodes so as to ionize the oxygen at the air electrode, whereupon the ionized oxygen travels through the electrolyte and is converted to oxygen gas at the oxygen electrode.

  8. Improvements of anti-corrosion and mechanical properties of NiTi orthopedic materials by acetylene, nitrogen and oxygen plasma immersion ion implantation

    NASA Astrophysics Data System (ADS)

    Poon, Ray W. Y.; Ho, Joan P. Y.; Liu, Xuanyong; Chung, C. Y.; Chu, Paul K.; Yeung, Kelvin W. K.; Lu, William W.; Cheung, Kenneth M. C.

    2005-08-01

    Nickel-titanium shape memory alloys (NiTi) are useful materials in orthopedics and orthodontics due to their unique super-elasticity and shape memory effects. However, the problem associated with the release of harmful Ni ions to human tissues and fluids has been raising safety concern. Hence, it is necessary to produce a surface barrier to impede the out-diffusion of Ni ions from the materials. We have conducted acetylene, nitrogen and oxygen plasma immersion ion implantation (PIII) into NiTi alloys in an attempt to improve the surface properties. All the implanted and annealed samples surfaces exhibit outstanding corrosion and Ni out-diffusion resistance. Besides, the implanted layers are mechanically stronger than the substrate underneath. XPS analyses disclose that the layer formed by C2H2 PIII is composed of mainly TiCx with increasing Ti to C concentration ratios towards the bulk. The nitrogen PIII layer is observed to be TiN, whereas the oxygen PIII layer is composed of oxides of Ti4+, Ti3+ and Ti2+.

  9. The effects of oxygen plasma and humidity on surface roughness, water contact angle and hardness of silicon, silicon dioxide and glass

    NASA Astrophysics Data System (ADS)

    Alam, A. U.; Howlader, M. M. R.; Deen, M. J.

    2014-03-01

    For heterogeneous integration in many More-than-Moore applications, surface preparation is the key step to realizing well-bonded multiple substrates for electronics, photonics, fluidics and/or mechanical components without a degradation in performance. Therefore, it is critical to understand how various processing and environmental conditions affect their surface properties. In this paper, we investigate the effects of oxygen plasma and humidity on some key surface properties such as the water contact angle, roughness and hardness of three materials: silicon (Si), silicon dioxide (SiO2) and glass, and their impact on bondability. The low surface roughness, high surface reactivity and high hydrophilicity of Si, SiO2 and glass at lower activation times can result in better bondability. Although, the surface reactivity of plasma-ambient-humidity-treated Si and SiO2 is considerably reduced, their reduction of roughness and increase of hydrophilicity may enable good bonding at low temperature heating due to augmented hydroxyl groups. The decrease of hardness of Si and SiO2 with increased activation time is attributed to higher surface roughness and the formation of amorphous layers of Si. While contact angle and surface roughness results show a correlation with bondability, the role of hardness on bondability requires further investigation.

  10. Feasibility of low energy plasma torch for reaction control thruster ignition

    NASA Astrophysics Data System (ADS)

    Park, Chunyoung

    A DC--thermal plasma jet is proposed as a reliable ignition source for reaction control system (RCS) thrusters employing oxygen with hydrocarbons, like methane. Industrial plasma torch systems are analyzed to understand the behavioral characteristics of DC--thermal plasmas. Nitrogen is used as a working gas for the source of plasma jet to understand the general mechanism of thermal plasma formation. DC--thermal plasmas require high electrical energy to maintain their arc discharge status which presents challenges in space systems. The purpose of this study is, therefore, to find a suitable configuration which minimizes power consumption. Various physical and electrical conditions relate to a thermal plasma formation. In this study, the input voltage (221--332V) and pressure (5--15 psi) are applied as initial conditions. The DC--power module and starter module are designed as plasma drivers and a commercial off--the--shelf torch head is used for this research. The normalized method is developed to estimate the arc temperature. Test results show that the lowest power consumption and arc--starting voltage are 1,321W and 248.8 VDC, respectively. In addition, it is found that the current is a major factor for varying the mass flow rate. Since the lowest power consumption is still high, future improvements and research should focus on integrating a high--power and lightweight energy source, developing a high--frequency and half--duty cycle power system, and incorporating a composite cathode. In addition, a new conceptual torch design is proposed to be considered as an igniter for RCS thrusters. The next step would be to repeat the plasma torch tests with the new configuration at ambient and vacuum conditions. These would be followed by combustion tests to verify the actual functionality of the plasma igniter for RCS thrusters with various oxidizer and fuel mixture ratios. In parallel, research should focus on miniaturization of the electrical system.

  11. Pulsed dc self-sustained magnetron sputtering

    SciTech Connect

    Wiatrowski, A.; Posadowski, W. M.; Radzimski, Z. J.

    2008-09-15

    The magnetron sputtering has become one of the commonly used techniques for industrial deposition of thin films and coatings due to its simplicity and reliability. At standard magnetron sputtering conditions (argon pressure of {approx}0.5 Pa) inert gas particles (necessary to sustain discharge) are often entrapped in the deposited films. Inert gas contamination can be eliminated during the self-sustained magnetron sputtering (SSS) process, where the presence of the inert gas is not a necessary requirement. Moreover the SSS process that is possible due to the high degree of ionization of the sputtered material also gives a unique condition during the transport of sputtered particles to the substrate. So far it has been shown that the self-sustained mode of magnetron operation can be obtained using dc powering (dc-SSS) only. The main disadvantage of the dc-SSS process is its instability related to random arc formation. In such case the discharge has to be temporarily extinguished to prevent damaging both the magnetron source and power supply. The authors postulate that pulsed powering could protect the SSS process against arcs, similarly to reactive pulsed magnetron deposition processes of insulating thin films. To put this concept into practice, (i) the high enough plasma density has to be achieved and (ii) the type of pulsed powering has to be chosen taking plasma dynamics into account. In this article results of pulsed dc self-sustained magnetron sputtering (pulsed dc-SSS) are presented. The planar magnetron equipped with a 50 mm diameter and 6 mm thick copper target was used during the experiments. The maximum target power was about 11 kW, which corresponded to the target power density of {approx}560 W/cm{sup 2}. The magnetron operation was investigated as a function of pulse frequency (20-100 kHz) and pulse duty factor (50%-90%). The discharge (argon) extinction pressure level was determined for these conditions. The plasma emission spectra (400-410 nm range

  12. Quasi-DC electrical discharge characterization in a supersonic flow

    NASA Astrophysics Data System (ADS)

    Houpt, Alec; Hedlund, Brock; Leonov, Sergey; Ombrello, Timothy; Carter, Campbell

    2017-04-01

    A Quasi-DC (Q-DC) electrical discharge generates a highly transient filamentary plasma in high-speed airflow. Major specific properties of this type of discharge are realized due to a strong coupling of the plasma to the moving gas. The plasma, supplied by a DC voltage waveform, demonstrates a pulsed-periodic pattern of dynamics significantly affecting the flow structure. In this study, the dynamics and plasma parameters of the Q-DC discharge are analyzed in the Supersonic Test Rig (SBR-50) at the University of Notre Dame at Mach number M = 2, stagnation pressure P 0 = (0.9-2.6) × 105 Pa, stagnation temperature T 0 = 300 K, unit Reynolds number ReL = 7-25 × 106 m-1, and plasma power W pl = 3-21 kW. The plasma parameters are measured with current-voltage probes and optical emission spectroscopy. An unsteady pattern of interaction is depicted by high-speed image capturing. The result of the plasma-flow interaction is characterized by means of pressure measurements and schlieren visualization. It is considered that the Q-DC discharge may be employed for active control of duct-driven flows, cavity-based flow, and for effective control of shock wave-boundary layer interaction.

  13. Impact of high microwave power on hydrogen impurity trapping in nanocrystalline diamond films grown with simultaneous nitrogen and oxygen addition into methane/hydrogen plasma

    NASA Astrophysics Data System (ADS)

    Tang, C. J.; Fernandes, A. J. S.; Jiang, X. F.; Pinto, J. L.; Ye, H.

    2016-01-01

    In this work, we study for the first time the influence of microwave power higher than 2.0 kW on bonded hydrogen impurity incorporation (form and content) in nanocrystalline diamond (NCD) films grown in a 5 kW MPCVD reactor. The NCD samples of different thickness ranging from 25 to 205 μm were obtained through a small amount of simultaneous nitrogen and oxygen addition into conventional about 4% methane in hydrogen reactants by keeping the other operating parameters in the same range as that typically used for the growth of large-grained polycrystalline diamond films. Specific hydrogen point defect in the NCD films is analyzed by using Fourier-transform infrared (FTIR) spectroscopy. When the other operating parameters are kept constant (mainly the input gases), with increasing of microwave power from 2.0 to 3.2 kW (the pressure was increased slightly in order to stabilize the plasma ball of the same size), which simultaneously resulting in the rise of substrate temperature more than 100 °C, the growth rate of the NCD films increases one order of magnitude from 0.3 to 3.0 μm/h, while the content of hydrogen impurity trapped in the NCD films during the growth process decreases with power. It has also been found that a new H related infrared absorption peak appears at 2834 cm-1 in the NCD films grown with a small amount of nitrogen and oxygen addition at power higher than 2.0 kW and increases with power higher than 3.0 kW. According to these new experimental results, the role of high microwave power on diamond growth and hydrogen impurity incorporation is discussed based on the standard growth mechanism of CVD diamonds using CH4/H2 gas mixtures. Our current experimental findings shed light into the incorporation mechanism of hydrogen impurity in NCD films grown with a small amount of nitrogen and oxygen addition into methane/hydrogen plasma.

  14. Experimental observation of further frequency upshift from dc to ac radiation converter with perpendicular dc magnetic field

    PubMed

    Higashiguchi; Yugami; Gao; Niiyama; Sasaki; Takahashi; Ito; Nishida

    2000-11-20

    A frequency upshift of a short microwave pulse is generated by the interaction between a relativistic underdense ionization front and a periodic electrostatic field with a perpendicular dc magnetic field. When the dc magnetic field is applied, further frequency upshift of 3 GHz is observed with respect to an unmagnetized case which has typically a GHz range. The radiation frequency depends on both the plasma density and the strength of the dc magnetic field, i.e., the plasma frequency and the cyclotron frequency. The frequency of the emitted radiation is in reasonable agreement with the theoretical values.

  15. ‘Reliability of new poly (lactic-co-glycolic acid) membranes treated with oxygen plasma plus silicon dioxide layers for pre-prosthetic guided bone regeneration processes’

    PubMed Central

    Castillo-Dalí, Gabriel; Batista-Cruzado, Antonio; López-Santos, Carmen; Rodríguez-González-Elipe, Agustín; Saffar, Jean-Louis; Lynch, Christopher D.; Gutiérrez-Pérez, José-Luis; Torres-Lagares, Daniel

    2017-01-01

    Background The use of cold plasmas may improve the surface roughness of poly(lactic-co-glycolic) acid (PLGA) membranes, which may stimulate the adhesion of osteogenic mediators and cells, thus accelerating the biodegradation of the barriers. Moreover, the incorporation of metallic-oxide particles to the surface of these membranes may enhance their osteoinductive capacity. Therefore, the aim of this paper was to evaluate the reliability of a new PLGA membrane after being treated with oxygen plasma (PO2) plus silicon dioxide (SiO2) layers for guided bone regeneration (GBR) processes. Material and Methods Circumferential bone defects (diameter: 11 mm; depth: 3 mm) were created on the top of eight experimentation rabbits’ skulls and were randomly covered with: (1) PLGA membranes (control), or (2) PLGA/PO2/SiO2 barriers. The animals were euthanized two months afterwards. A micromorphologic study was then performed using ROI (region of interest) colour analysis. Percentage of new bone formation, length of mineralised bone, concentration of osteoclasts, and intensity of ostheosynthetic activity were assessed and compared with those of the original bone tissue. The Kruskal-Wallis test was applied for between-group com Asignificance level of a=0.05 was considered. Results The PLGA/PO2/SiO2 membranes achieved the significantly highest new bone formation, length of mineralised bone, concentration of osteoclasts, and ostheosynthetic activity. The percentage of regenerated bone supplied by the new membranes was similar to that of the original bone tissue. Unlike what happened in the control group, PLGA/PO2/SiO2 membranes predominantly showed bone layers in advanced stages of formation. Conclusions The addition of SiO2 layers to PLGA membranes pre-treated with PO2 improves their bone-regeneration potential. Although further research is necessary to corroborate these conclusions in humans, this could be a promising strategy to rebuild the bone architecture prior to rehabilitate

  16. Multilevel DC link inverter

    DOEpatents

    Su, Gui-Jia

    2003-06-10

    A multilevel DC link inverter and method for improving torque response and current regulation in permanent magnet motors and switched reluctance motors having a low inductance includes a plurality of voltage controlled cells connected in series for applying a resulting dc voltage comprised of one or more incremental dc voltages. The cells are provided with switches for increasing the resulting applied dc voltage as speed and back EMF increase, while limiting the voltage that is applied to the commutation switches to perform PWM or dc voltage stepping functions, so as to limit current ripple in the stator windings below an acceptable level, typically 5%. Several embodiments are disclosed including inverters using IGBT's, inverters using thyristors. All of the inverters are operable in both motoring and regenerating modes.

  17. Graphene oxide induces plasma membrane damage, reactive oxygen species accumulation and fatty acid profiles change in Pichia pastoris.

    PubMed

    Zhang, Meng; Yu, Qilin; Liang, Chen; Liu, Zhe; Zhang, Biao; Li, Mingchun

    2016-10-01

    During the past couple of years, graphene nanomaterials were extremely popular among the scientists due to the promising properties in many aspects. Before the materials being well applied, we should first focus on their biosafety and toxicity. In this study, we investigated the toxicity of synthesized graphene oxide (GO) against the model industrial organism Pichia pastoris. We found that the synthesized GO showed dose-dependent toxicity to P. pastoris, through cell membrane damage and intracellular reactive oxygen species (ROS) accumulation. In response to these cell stresses, cells had normal unsaturated fatty acid (UFA) levels but increased contents of polyunsaturated fatty acid (PUFA) with up-regulation of UFA synthesis-related genes on the transcriptional level, which made it overcome the stress under GO attack. Two UFA defective strains (spt23Δ and fad12Δ) were used to demonstrate the results above. Hence, this study suggested a close connection between PUFAs and cell survival against GO.

  18. Rapid extraction and reverse phase-liquid chromatographic separation of mercury(II) and methylmercury in fish samples with inductively coupled plasma mass spectrometric detection applying oxygen addition into plasma.

    PubMed

    Döker, Serhat; Boşgelmez, İffet İpek

    2015-10-01

    A simple and sensitive procedure was developed for extraction and speciation of mercury in fish. Species separation was accomplished with reverse phase-high performance liquid chromatography (HPLC) hyphenated to inductively coupled plasma mass spectrometry (ICP-MS). Oxygen addition into plasma allowed use of organic-rich mobile phase, achieving species separation in 4 min. Mercury species extraction was achieved by microwave exposure for 2 min at mild conditions (60°C, pH 2.0), avoiding necessity of neutralizing sample prior to injection in HPLC, and reducing number of sample preparation steps, analytical source of errors and inter conversion of species. Limit of detection for entire procedure was found to be 0.2 and 0.1 ng g(-1) for mercuric ion and methylmercury, respectively. The method was applied to certified reference materials (TORT-2 and DORM-2) and commercialized fish samples (Mullus barbatus, Sparus aurata, Trachurus mediterraneus, Mugil soiuy, Dicentrarchus labrax, and Pomatomus saltatrix) from Black Sea.

  19. Radiation-Tolerant DC-DC Converters

    NASA Technical Reports Server (NTRS)

    Skutt, Glenn; Sable, Dan; Leslie, Leonard; Graham, Shawn

    2012-01-01

    A document discusses power converters suitable for space use that meet the DSCC MIL-PRF-38534 Appendix G radiation hardness level P classification. A method for qualifying commercially produced electronic parts for DC-DC converters per the Defense Supply Center Columbus (DSCC) radiation hardened assurance requirements was developed. Development and compliance testing of standard hybrid converters suitable for space use were completed for missions with total dose radiation requirements of up to 30 kRad. This innovation provides the same overall performance as standard hybrid converters, but includes assurance of radiation- tolerant design through components and design compliance testing. This availability of design-certified radiation-tolerant converters can significantly reduce total cost and delivery time for power converters for space applications that fit the appropriate DSCC classification (30 kRad).

  20. 75 FR 6160 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, DC-10-15, DC...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-08

    ... Douglas Corporation Model DC- 10-10, DC-10-10F, DC-10-15, DC-10-30, DC-10-30F (KC-10A and KDC-10), DC-10... airworthiness directive (AD) for certain Model DC-10-10, DC-10-10F, DC-10-15, DC-10-30, DC-10-30F (KC- 10A and... would require a one-time installation of electrical bonding jumpers for the fill valve controllers...

  1. Forback DC-to-DC converter

    NASA Technical Reports Server (NTRS)

    Lukemire, Alan T. (Inventor)

    1993-01-01

    A pulse-width modulated DC-to-DC power converter including a first inductor, i.e. a transformer or an equivalent fixed inductor equal to the inductance of the secondary winding of the transformer, coupled across a source of DC input voltage via a transistor switch which is rendered alternately conductive (ON) and nonconductive (OFF) in accordance with a signal from a feedback control circuit is described. A first capacitor capacitively couples one side of the first inductor to a second inductor which is connected to a second capacitor which is coupled to the other side of the first inductor. A circuit load shunts the second capacitor. A semiconductor diode is additionally coupled from a common circuit connection between the first capacitor and the second inductor to the other side of the first inductor. A current sense transformer generating a current feedback signal for the switch control circuit is directly coupled in series with the other side of the first inductor so that the first capacitor, the second inductor and the current sense transformer are connected in series through the first inductor. The inductance values of the first and second inductors, moreover, are made identical. Such a converter topology results in a simultaneous voltsecond balance in the first inductance and ampere-second balance in the current sense transformer.

  2. Forback DC-to-DC converter

    NASA Technical Reports Server (NTRS)

    Lukemire, Alan T. (Inventor)

    1995-01-01

    A pulse-width modulated DC-to-DC power converter including a first inductor, i.e. a transformer or an equivalent fixed inductor equal to the inductance of the secondary winding of the transformer, coupled across a source of DC input voltage via a transistor switch which is rendered alternately conductive (ON) and nonconductive (OFF) in accordance with a signal from a feedback control circuit is described. A first capacitor capacitively couples one side of the first inductor to a second inductor which is connected to a second capacitor which is coupled to the other side of the first inductor. A circuit load shunts the second capacitor. A semiconductor diode is additionally coupled from a common circuit connection between the first capacitor and the second inductor to the other side of the first inductor. A current sense transformer generating a current feedback signal for the switch control circuit is directly coupled in series with the other side of the first inductor so that the first capacitor, the second inductor and the current sense transformer are connected in series through the first inductor. The inductance values of the first and second inductors, moreover, are made identical. Such a converter topology results in a simultaneous voltsecond balance in the first inductance and ampere-second balance in the current sense transformer.

  3. On the E-H transition in inductively coupled radio frequency oxygen plasmas: II. Electronegativity and the impact on particle kinetics

    NASA Astrophysics Data System (ADS)

    Wegner, Th; Küllig, C.; Meichsner, J.

    2017-02-01

    In this series of two papers we present results about the E-H transition of an inductively coupled oxygen discharge driven at radio frequency (13.56 MHz) for different total gas pressures. The mode transition from the low density E-mode to the high density H-mode is studied using comprehensive plasma diagnostics. The measured electron density can be used to distinguish between the different operation modes. This paper focuses on the determination of the negative atomic ion density and the electronegativity by two experimental methods and global rate equation calculation. As a result, the electronegativity significantly decreases over two orders of magnitude from about 25 in the E-mode to about 0.1 in the H-mode. The temporal behavior of the electronegativity in pulsed ICP shows that the negative atomic ion density reaches a steady state after 10 ms. Negative atomic ions are mainly produced by the dissociative attachment with the molecular ground state. The ion-ion recombination with the positive molecular ions and the collisional detachment with the singlet molecular metastables contribute significantly to the loss of the negative atomic ions.

  4. Modification of the hydrophilic/hydrophobic characteristic of zein film surfaces by contact with oxygen plasma treated PDMS and oleic acid content.

    PubMed

    Gezer, P Gizem; Brodsky, Serena; Hsiao, Austin; Liu, G Logan; Kokini, Jozef L

    2015-11-01

    Zein has been widely studied as a biopolymer due to its unique film-forming abilities. Surface properties are of high importance for certain applications which include microfluidics and tissue engineering, as they drastically affect the end result. It is important to develop techniques to modify zein surface properties without compromising bulk material properties. In this study, we developed a facile technique to change the water affinity of zein film surfaces, compatible with patterning techniques via soft lithography. This is achieved by a simple solvent casting technique onto a polydimethylsilohexane (PDMS) substrate that was exposed to oxygen plasma. Water contact angle measurements (WCA) were used to assess the hydrophillicity of zein surfaces and they reached as low as 20°. Atomic force microscopy, optical absorbance and light microscopy were used to study the characteristics of the film and its surface topography. Hydrophilic zein surfaces had higher roughness values compared to hydrophobic ones. Surface roughness, introduced by sandpaper and gratings does not have the same effect as surface chemistry. The amphiphilic nature of plasticizer oleic acid also contributed to the change in the water contact angle of the films. In conclusion, we demonstrated that zein film's surface properties can be controlled by its ability to self-assemble depending on the substrate that it is being cast on.

  5. Adhesion of Pseudomonas aeruginosa strains to untreated and oxygen-plasma treated poly(vinyl chloride) (PVC) from endotracheal intubation devices.

    PubMed

    Triandafillu, K; Balazs, D J; Aronsson, B-O; Descouts, P; Tu Quoc, P; van Delden, C; Mathieu, H J; Harms, H

    2003-04-01

    Pseudomonas aeruginosa pneumonia is a life threatening complication in mechanically ventilated patients that requires the ability of the bacteria to adhere to, and colonize the endotracheal intubation device. New strategies to prevent or reduce these nosocomial infections are greatly needed. We report here the study of a set of P. aeruginosa clinical isolates, together with specific mutants, regarding their adhesion on native and chemically modified poly(vinyl chloride) (PVC) surfaces from endotracheal intubation devices. The adhesion of the different strains to untreated PVC varied widely, correlating with several physico-chemical characteristics known to influence the attachment of bacteria to inert surfaces. The adhesion patterns were compared to the calculations obtained with the DLVO theory of colloidal stability. These results illustrate the importance of testing different clinical isolates when investigating bacterial adhesion. Oxygen plasma treatment of the PVC pieces yielded a hydrophilic surface and reduced the number of adhering bacteria by as much as 70%. This reduction is however unlikely to be sufficient to prevent P. aeruginosa colonization of endotracheal intubation devices.

  6. Mixed culture biofilms of Salmonella Typhimurium and cultivable indigenous microorganisms on lettuce show enhanced resistance of their sessile cells to cold oxygen plasma.

    PubMed

    Jahid, Iqbal Kabir; Han, Noori; Zhang, Cheng-Yi; Ha, Sang-Do

    2015-04-01

    Control of foodborne pathogens in fresh produce is crucial for food safety, and numerous Salmonella Typhimurium (ST) outbreaks have been reported already. The present study was done to assess effectiveness of cold oxygen plasma (COP) against biofilms of ST mixed with cultivable indigenous microorganisms (CIM). ST and CIM were grown at 15 °C as monocultures and mixed cultures for planktonic state, biofilm on stainless steel, and lettuce leaves. Thereafter, the samples were treated with COP and surviving populations were counted using plate counting methods. Biofilms and stomatal colonization were examined using field emission scanning electron microscopy (FESEM) and food quality was assessed after treatment. Mixed cultures of ST and CIM showed an antagonistic interaction on lettuce but not on SS or in planktonic state. Mixed cultures showed significantly (p < 0.05) greater resistance to COP compared to monoculture biofilms on lettuce but not on SS or planktonic state. Shift from smooth to rugose colony type was found for planktonic and for biofilms on SS but not on lettuce for ST. Mixed culture biofilms colonized stomata on the inside as demonstrated by FESEM. Although, lettuce quality was not affected by COP, this technology has to be optimized for further development of the successful inactivation of complex multispecies biofilm structures presented by real food environment.