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1

Dielectric barrier discharge plasma actuator for flow control  

NASA Astrophysics Data System (ADS)

Electrohydrodynamic (EHD) and magnetohydrodynamic phenomena are being widely studied for aerodynamic applications. The major effects of these phenomena are heating of the gas, body force generation, and enthalpy addition or extraction, [1, 2, 3]. In particular, asymmetric dielectric barrier discharge (DBD) plasma actuators are known to be effective EHD device in aerodynamic control, [4, 5]. Experiments have demonstrated their effectiveness in separation control, acoustic noise reduction, and other aeronautic applications. In contrast to conventional DBD actuators driven by sinusoidal voltages, we proposed and used a voltage profile consisting of nanosecond pulses superimposed on dc bias voltage. This produces what is essentially a non-self-sustained discharge: the plasma is generated by repetitive short pulses, and the pushing of the gas occurs primarily due to the bias voltage. The advantage of this non-self-sustained discharge is that the parameters of ionizing pulses and the driving bias voltage can be varied independently, which adds flexibility to control and optimization of the actuators performance. Experimental studies were conducted of a flow induced in a quiescent room air by a single DBD actuator. A new approach for non-intrusive 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 2-D numerical fluid modeling. During the experiments, it was found that DBD performance is severely limited by surface charge accumulation on the dielectric. Several ways to mitigate the surface charge were found: using a reversing DC bias potential, three-electrode configuration, slightly conductive dielectrics, and semi conductive coatings. Force balance measurements proved the effectiveness of the suggested configurations and advantages of the new voltage profile (pulses+bias) over the traditional sinusoidal one at relatively low voltages. In view of practical applications certain questions have been also addressed, such as electrodynamic effects which accompany scaling of the actuators to real size models, and environmental effects of ozone production by the plasma actuators.

Opaits, Dmitry Florievich

2

Dielectric Barrier Discharge Plasma Actuator for Flow Control  

NASA Technical Reports Server (NTRS)

This report is Part II of the final report of NASA Cooperative Agreement contract no. NNX07AC02A. It includes a Ph.D. dissertation. The period of performance was January 1, 2007 to December 31, 2010. Part I of the final report is the overview published as NASA/CR-2012- 217654. Asymmetric dielectric barrier discharge (DBD) plasma actuators driven by nanosecond pulses superimposed on dc bias voltage are studied experimentally. This produces non-self-sustained discharge: the plasma is generated by repetitive short pulses, and the pushing of the gas occurs primarily due to the bias voltage. The parameters of ionizing pulses and the driving bias voltage can be varied independently, which adds flexibility to control and optimization of the actuators performance. The approach consisted of three elements coupled together: the Schlieren technique, burst mode of plasma actuator operation, and 2-D numerical fluid modeling. During the experiments, it was found that DBD performance is severely limited by surface charge accumulation on the dielectric. Several ways to mitigate the surface charge were found: using a reversing DC bias potential, three-electrode configuration, slightly conductive dielectrics, and semi conductive coatings. Force balance measurements proved the effectiveness of the suggested configurations and advantages of the new voltage profile (pulses+bias) over the traditional sinusoidal one at relatively low voltages. In view of practical applications certain questions have been also addressed, such as electrodynamic effects which accompany scaling of the actuators to real size models, and environmental effects of ozone production by the plasma actuators.

Opaits, Dmitry, F.

2012-01-01

3

Impedance matching for an asymmetric dielectric barrier discharge plasma actuator  

E-print Network

. © 2007 American Institute of Physics. DOI: 10.1063/1.2773932 Active control of air flow using surface plasma actuators has emerged in recent years. Such control involves modify- ing air flow pattern- strated for flow modification along flat plates4 and for stall control over airfoils.5 The weakly ionized

Roy, Subrata

4

Measurements and Simulations of Surface Dielectric Barrier Discharges Used as Plasma Actuators  

NASA Technical Reports Server (NTRS)

This report is a Ph.D. dissertation performed under NRA cooperative agreement and submitted as part of the final report. Asymmetric surface dielectric barrier discharges (DBDs) have shown promise for use as aerodynamic actuators for active flow control. In this project we studied DBD actuators experimentally and numerically. Our DBDs used a symmetric triangular high voltage waveform to generate plasma in atmospheric pressure air. Time-averaged measurements indicated that the induced force of a single barrier actuator design (one electrode insulated from the plasma) can be increased exponentially above the results of previous studies by decreasing both the length and thickness of the electrode exposed to the plasma. This increased force may allow these devices to control flow separation in a wider range of flow environments. Experiments using an intensified digital camera to examine the plasma on time scales of a few nanoseconds showed that, in addition to the previously-observed filamentary and jet-like plasma structures, discharges with very thin exposed electrodes exhibited a weak but constant plasma immediately adjacent to those electrodes. In double-barrier actuators (both electrodes insulated), decreasing the diameter of the narrower electrode lead to increasing forces, and recorded images showed the simultaneous existence of both filamentary and jet-like plasma structures. The development and application of a time-dependent, two-dimensional computational fluid plasma model has aided in understanding the detailed physics of surface DBDs at all-time scales. For simulated single-barrier discharges, the model qualitatively reproduced the filamentary and jet-like micro-discharge structures. The model was somewhat successful in reproducing the observed characteristics of double-barrier actuators. For both actuator geometries, the model indicated that the majority of the forces induced on the neutral gas occur in between micro-discharges as the plasmas decay.

Hoskinson, Alan R.

2012-01-01

5

Numerical analysis of plasma evolution on dielectric barrier discharge plasma actuator  

SciTech Connect

Time evolution of the discharge plasma in the dielectric barrier discharge (DBD) plasma actuator was simulated by the simple fluid model in which the electron and single positive ion species were considered. The characteristics of the discharge plasma evolution were investigated in detail, and the following results were obtained. When the positive-going voltage is applied, the streamer discharge is formed periodically. The periodically formed streamer expands from the exposed electrode, and its length becomes longer than the previous one. Periodic breakdown of the gas and step-by-step plasma expansion are also observed during the negative-going voltage; however, the streamer is not formed and the breakdown frequency is much higher. The simulation results with a triangular applied voltage waveform show the same characteristics as observed in the experiment; large discharge current spikes are observed during both the positive- and negative-going voltage phase, and the plasma in the negative-going voltage phase expands more smoothly than that in the positive phase because of its higher breakdown frequency. It was shown that even the simple numerical model could provide valuable insights into the physics of DBD plasma actuator; this indicates that the positive ions and electrons play a prominent role in determining the general characteristics of the plasma evolution.

Nishida, Hiroyuki [Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588 (Japan); Abe, Takashi [Institute of Space and Astronautical Science, JAXA, Sagamihara, Kanagawa 229-8510 (Japan)

2011-07-01

6

Effect of dielectric barrier discharge plasma actuators on non-equilibrium hypersonic flows  

NASA Astrophysics Data System (ADS)

A numerical study employing discontinuous Galerkin method demonstrating net surface heat reduction for a cylindrical body in Mach 17 hypersonic flow is presented. This application focuses on using sinusoidal dielectric barrier discharge plasma actuators to inject momentum near the stagnation point. A 5 species finite rate air chemistry model completes the picture by analyzing the effect of the actuator on the flow chemistry. With low velocity near the stagnation point, the plasma actuator sufficiently modifies the fluid momentum. This results in redistribution of the integrated surface heating load on the body. Specifically, a particular configuration of normally pinching plasma actuation is predicted to reduce the surface heat flux at the stagnation point. An average reduction of 0.246% for the integrated and a maximum reduction of 7.68% are reported for the surface heat flux. The temperature contours in the fluid flow (with maximum temperature over 12 000 K) are pinched away from the stagnation point, thus resulting in reduced thermal load. Plasma actuation in this configuration also affects the species concentration distribution near the wall, in addition to the temperature gradient. The combined effect of both, thus results in an average reduction of 0.0986% and a maximum reduction of 4.04% for non-equilibrium calculations. Thus, this study successfully demonstrates the impact of sinusoidal dielectric barrier discharge plasma actuation on the reduction of thermal load on a hypersonic body.

Bhatia, Ankush; Roy, Subrata; Gosse, Ryan

2014-10-01

7

American Institute of Aeronautics and Astronautics On Multi-Barrier Plasma Actuators  

E-print Network

American Institute of Aeronautics and Astronautics 1 On Multi-Barrier Plasma Actuators Ryan January 2011, Orlando, Florida AIAA 2011-958 Copyright © 2011 by the Authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. #12;American Institute of Aeronautics

Roy, Subrata

8

American Institute of Aeronautics and Astronautics Novel Multi-Barrier Plasma Actuators for Increased Thrust  

E-print Network

American Institute of Aeronautics and Astronautics 1 Novel Multi-Barrier Plasma Actuators by the American Institute of Aeronautics and Astronautics, Inc., with permission. #12;American Institute of Aeronautics and Astronautics 2 and 1-20 kHz, respectively. Such a high potential difference weakly ionizes

Roy, Subrata

9

Influence of shock wave propagation on dielectric barrier discharge plasma actuator performance  

NASA Astrophysics Data System (ADS)

Interest in plasma actuators as active flow control devices is growing rapidly due to their lack of mechanical parts, light weight and high response frequency. Although the flow induced by these actuators has received much attention, the effect that the external flow has on the performance of the actuator itself must also be considered, especially the influence of unsteady high-speed flows which are fast becoming a norm in the operating flight envelopes. The primary objective of this study is to examine the characteristics of a dielectric barrier discharge (DBD) plasma actuator when exposed to an unsteady flow generated by a shock tube. This type of flow, which is often used in different studies, contains a range of flow regimes from sudden pressure and density changes to relatively uniform high-speed flow regions. A small circular shock tube is employed along with the schlieren photography technique to visualize the flow. The voltage and current traces of the plasma actuator are monitored throughout, and using the well-established shock tube theory the change in the actuator characteristics are related to the physical processes which occur inside the shock tube. The results show that not only is the shear layer outside of the shock tube affected by the plasma but the passage of the shock front and high-speed flow behind it also greatly influences the properties of the plasma.

Erfani, Rasool; Zare-Behtash, Hossein; Kontis, Konstantinos

2012-06-01

10

Optical and electrical characterization of a surface dielectric barrier discharge plasma actuator  

NASA Astrophysics Data System (ADS)

An experimental characterization of the properties of asymmetric surface dielectric barrier discharges used as plasma actuators was performed. Optical emission spectroscopy was used to measure the radiated power and some plasma parameters such as the electron and vibrational temperature. Electrical characterization of the discharge was executed by recording individual current pulses with high temporal resolution, and collecting a large dataset of these events. Statistical analysis performed on them allowed one to correlate microdischarge (MD) properties with the voltage phase and to spot differences arising from the actual breakdown mechanism in such asymmetric configurations. In particular, the asymmetry between the two different half-cycles of the discharges was characterized, and it was found that it directly influences plasma actuator efficiency. Differences arising in the multiplicity, amplitude and temporal duration of the MDs were investigated. Some effects connected with the dielectric material and high voltage supply properties were evaluated and correlated with the induced velocity provided by the plasma actuators.

Biganzoli, I.; Barni, R.; Riccardi, C.; Gurioli, A.; Pertile, R.

2013-04-01

11

Force Measurements of Single and Double Barrier DBD Plasma Actuators in Quiescent Air  

NASA Technical Reports Server (NTRS)

We have performed measurements of the force induced by both single (one electrode insulated) and double (both electrodes insulated) dielectric barrier discharge plasma actuators in quiescent air. We have shown that, for single barrier actuators, as the electrode diameter decreased below those values previously studied the induced Force increases exponentially rather than linearly. This behavior has been experimentally verified using two different measurement techniques: stagnation probe measurements of the induced flow velocity and direct measurement of the force using an electronic balance. In addition, we have shown the the induced force is independent of the material used for the exposed electrode. The same techniques have shown that the induced force of a double barrier actuator increases with decreasing narrow electrode diameter.

Hoskinson, Alan R.; Hershkowitz, Noah; Ashpis, David E.

2008-01-01

12

Phase effect on flow control for dielectric barrier plasma actuators  

SciTech Connect

Active control of flow has a wide range of applications. Specifically, mitigation of detachment due to the weakly ionized gas flow past a flat plate at an angle of attack is studied using two asymmetric sets of electrode pairs kept at a phase lag. The equations governing the dynamics of electrons, helium ions, and neutrals are solved self-consistently with charge-Poisson equation. The electrodynamic forces produced by two actuators largely depend on the relative phase between the potentials applied to rf electrodes and distance between them. A suitable phase and an optimum distance exist between two actuators for effective separation control.

Singh, K. P.; Roy, Subrata [Computational Plasma Dynamics Laboratory, Mechanical Engineering, Kettering University, Flint, Michigan 48504 (United States)

2006-07-03

13

Characterization of nanosecond pulse driven dielectric barrier discharge plasma actuators for aerodynamic flow control  

NASA Astrophysics Data System (ADS)

Positive polarity nanosecond pulse driven dielectric barrier discharge (ns-DBD) plasma actuators are studied experimentally in quiescent atmosphere. Pulse energy and instantaneous pulse power (hereafter referred to as energy and power) are calculated using simultaneous voltage and current measurements. Electrical characteristics are evaluated as a function of peak voltage, pulse frequency, discharge length, and dielectric thickness. Schlieren imaging is used to provide a relative estimate of discharge energy that is coupled to the near surface gas as heat for the same parameters. Characteristics of the DBD load have a substantial effect on the individual voltage and current traces which are reflected in the energy and power values. Power is mainly dependent on actuator length which is inconsistent with schlieren data as expected. Higher per unit length energy indicates a stronger compression wave for a given actuator geometry, but this is not universally true across different actuators suggesting some constructions more efficiently couple energy to the gas. Energy and compression wave strength are linearly related. Higher pulse frequency produces higher energy but is primarily attributed to heating of the actuator and power supply components and not to an optimal discharge frequency. Both energy and wave strength increase as peak voltage to the power of approximately 3.5 over a substantial range similar to ac-DBD plasma actuators.

Dawson, Robert; Little, Jesse

2013-03-01

14

Online-characterization of dielectric barrier discharge plasma actuators for optimized efficiency of aerodynamical flow control applications  

NASA Astrophysics Data System (ADS)

The impact of fluctuating and transient kinematic and thermodynamic airflow conditions on the performance of dielectric barrier discharge (DBD) plasma actuators is demonstrated. A novel online-characterization and control approach is introduced, revealing the possibility of compensating for impaired discharge performance due to changing airflow scenarios during actuator operation. The goal of controlling the plasma actuator performance online and in situ is achieved and successfully demonstrated.

Kriegseis, J.; Schrter, D.; Grundmann, S.; Tropea, C.

2011-06-01

15

High-lift airfoil trailing edge separation control using a single dielectric barrier discharge plasma actuator  

NASA Astrophysics Data System (ADS)

Control of flow separation from the deflected flap of a high-lift airfoil up to Reynolds numbers of 240,000 (15 m/s) is explored using a single dielectric barrier discharge (DBD) plasma actuator near the flap shoulder. Results show that the plasma discharge can increase or reduce the size of the time-averaged separated region over the flap depending on the frequency of actuation. High-frequency actuation, referred to here as quasi-steady forcing, slightly delays separation while lengthening and flattening the separated region without drastically increasing the measured lift. The actuator is found to be most effective for increasing lift when operated in an unsteady fashion at the natural oscillation frequency of the trailing edge flow field. Results indicate that the primary control mechanism in this configuration is an enhancement of the natural vortex shedding that promotes further momentum transfer between the freestream and separated region. Based on these results, different modulation waveforms for creating unsteady DBD plasma-induced flows are investigated in an effort to improve control authority. Subsequent measurements show that modulation using duty cycles of 50-70% generates stronger velocity perturbations than sinusoidal modulation in quiescent conditions at the expense of an increased power requirement. Investigation of these modulation waveforms for trailing edge separation control similarly shows that additional increases in lift can be obtained. The dependence of these results on the actuator carrier and modulation frequencies is discussed in detail.

Little, Jesse; Nishihara, Munetake; Adamovich, Igor; Samimy, Mo

2010-03-01

16

One-equation modeling and validation of dielectric barrier discharge plasma actuator thrust  

NASA Astrophysics Data System (ADS)

Dielectric barrier discharge (DBD) plasma actuators with an asymmetric electrode configuration can generate a wall-bounded jet without mechanical moving parts, which require considerable modifications of existing aeronautical objects and which incur high maintenance costs. Despite this potential, one factor preventing the wider application of such actuators is the lack of a reliable actuator model. It is difficult to develop such a model because calculating the ion-electric field and fluid interaction consume a high amount calculation effort during the numerical analysis. Thus, the authors proposed a semi-empirical model which predicted the thrust of plasma actuators with a simple equation. It gave a numeric thrust value, and we implemented the value on a computational fluid dynamics (CFD) solver to describe the two-dimensional flow field induced by the actuator. However, the model had a narrow validation range, depending on the empirical formula, and it did not fully consider environment variables. This study presents an improved model by replacing the empirical formulae in the previous model with physical equations that take into account physical phenomena and environmental variables. During this process, additional operation parameters, such as pressure, temperature and ac waveforms, are newly taken to predict the thrust performance of the actuators with a wider range of existing parameters, the thickness of the dielectric barrier, the exposed electrode, the dielectric constant, the ac frequency and the voltage amplitude. Thrust prediction curves from the model are compared to those of earlier experimental results, showing that the average error is less than 5% for more than one hundred instances of data. As in the earlier work, the predicted thrust value is implemented on a CFD solver, and two-dimensional wall-jet velocity profiles induced by the actuator are compared to the previous experimental results.

Yoon, Jae-San; Han, Jae-Hung

2014-10-01

17

Simulation of an asymmetric single dielectric barrier plasma actuator  

SciTech Connect

Continuity equations governing electron and ion density are solved with Poisson's equation to obtain spatial and temporal profiles of electron density, ion density, and voltage. The motion of electrons and ions results in charge separation and generation of an electrostatic electric field. Electron deposition downstream of the overlap region of the electrode results in formation of a virtual negative electrode that always attracts the charge separation. The value of charge separation e(n{sub i}-n{sub e}) and the force per volume F=e(n{sub i}-n{sub e})E have been obtained near the dielectric surface for the 50th cycle. Domain integration of the force F=e(n{sub i}-n{sub e})E has been obtained for different plasma densities, frequencies, and rf voltage wave forms. The time average of the x force is positive and the y force is negative over the domain; therefore there is an average net force on the plasma in the positive x and negative y directions. This will result in a moving wave of plasma over the dielectric surface in the positive x direction, which can find application in flow control.

Singh, K.P.; Roy, Subrata [Computational Plasma Dynamics Laboratory, Mechanical Engineering, Kettering University, Flint, Michigan 48504 (United States)

2005-10-15

18

Influence of operating pressure on surface dielectric barrier discharge plasma aerodynamic actuation characteristics  

SciTech Connect

This letter reports an experimental study of surface dielectric barrier discharge plasma aerodynamic actuation characteristics' dependence on operating pressure. As the pressure decreases, the N{sub 2}(C {sup 3}{pi}{sub u}) rotational temperature decreases, while its vibrational temperature decreases initially and then increases. In addition, the discharge mode changes from a filamentary type to a glow type at 45 Torr. In the filamentary mode, the electron density decreases with pressure, while the electron temperature remains almost unchanged. In the glow mode, however, both the electron density and the electron temperature increase while the pressure decreases. The induced velocity shows a maximum value at 445 Torr.

Wu Yun; Li Yinghong; Jia Min; Song Huimin [Engineering College, Air Force Engineering University, Xi'an 710038 (China); Guo Zhigang; Zhu Ximing; Pu Yikang [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)

2008-07-21

19

Forcing mechanisms of dielectric barrier discharge plasma actuators at carrier frequency of 625 Hz  

NASA Astrophysics Data System (ADS)

The forcing behavior of a dielectric barrier discharge (DBD) actuator is investigated experimentally using a time-resolved particle image velocimetry (PIV) system in conjunction with a phase shifting technique. The spatio-temporal evolution of the induced flowfield is accurately captured within one high voltage (HV) cycle allowing the calculation of the instantaneous velocity and acceleration. Additional voltage and current measurements provide the power consumption for each case. Four different applied voltage waveform shapes are independently tested, namely, sine, square, positive sawtooth, and negative sawtooth at fixed applied voltage (10 kVpp) and carrier frequency (625 Hz). The instantaneous flowfields reveal the effect of the plasma forcing during the HV cycle. Sine waveform provides large positive forcing during the forward stroke, with minimal but still positive forcing during the backward stroke. Square waveform provides strong and concentrated positive and negative forcing at the beginning of the forward and backward stroke, respectively. Positive sawtooth provides positive but weak forcing during both strokes while the negative sawtooth case produces observable forcing only during the forward stroke. Results indicate the inherent importance of negative ions on the force production mechanisms of DBD's. Furthermore, the revealed influence of the waveform shape on the force production can provide guidelines for the design of custom asymmetric waveforms for the improvement of the actuator's performance.

Kotsonis, M.; Ghaemi, S.

2011-12-01

20

Electrical and mechanical characteristics of surface AC dielectric barrier discharge plasma actuators applied to airflow control  

NASA Astrophysics Data System (ADS)

The present paper is a wide review on AC surface dielectric barrier discharge (DBD) actuators applied to airflow control. Both electrical and mechanical characteristics of surface DBD are presented and discussed. The first half of the present paper gives the last results concerning typical single plate-to-plate surface DBDs supplied by a sine high voltage. The discharge current, the plasma extension and its morphology are firstly analyzed. Then, time-averaged and time-resolved measurements of the produced electrohydrodynamic force and of the resulting electric wind are commented. The second half of the paper concerns a partial list of approaches having demonstrated a significant modification in the discharge behavior and an increasing of its mechanical performances. Typically, single DBDs can produce mean force and electric wind velocity up to 1 mN/W and 7 m/s, respectively. With multi-DBD designs, velocity up to 11 m/s has been measured and force up to 350 mN/m.

Benard, Nicolas; Moreau, Eric

2014-11-01

21

Effect of external flow velocity on momentum transfer of dielectric barrier discharge plasma actuators  

NASA Astrophysics Data System (ADS)

An experimental study is performed towards identifying cross-talk effects between DBD plasma actuators and external flow. An actuator is positioned in a boundary layer operated in a range of free stream velocities from 0 to 60 m/s, and tested both in counter-flow and co-flow forcing configurations. Electrical measurements are used for estimating the power consumption and the discharge formation is visualized using a CCD camera. The actuator's force is measured using a sensitive load cell. Results show the power consumption is constant for different flow velocities and actuator configurations. The plasma light emission is constant for co-flow forcing but shows a trend of increasing intensity with counter-flow forcing for increasing free stream velocities. The measured force is constant for free stream velocities larger than 20 m/s, with same magnitude and opposite direction for the counter-flow and co-flow configurations. In quiescent conditions, the measured force is smaller due to the change in wall shear force by the induced wall-jet. An analytical model is presented to estimate the influence of external flow on the actuator force. It is based on conservation of momentum through the ion-neutral collisional process while including the contribution of the wall shear force. Satisfactory agreement is found between the prediction of the model and experimental data at different external flow velocities.

Pereira, Ricardo; Ragni, Daniele; Kotsonis, Marios

2014-09-01

22

Simulation Tool for Dielectric Barrier Discharge Plasma Actuators at Atmospheric and Sub-Atmospheric Pressures: SBIR Phase I Final Report  

NASA Technical Reports Server (NTRS)

This report is the final report of a SBIR Phase I project. It is identical to the final report submitted, after some proprietary information of administrative nature has been removed. The development of a numerical simulation tool for dielectric barrier discharge (DBD) plasma actuator is reported. The objectives of the project were to analyze and predict DBD operation at wide range of ambient gas pressures. It overcomes the limitations of traditional DBD codes which are limited to low-speed applications and have weak prediction capabilities. The software tool allows DBD actuator analysis and prediction for subsonic to hypersonic flow regime. The simulation tool is based on the VORPAL code developed by Tech-X Corporation. VORPAL's capability of modeling DBD plasma actuator at low pressures (0.1 to 10 torr) using kinetic plasma modeling approach, and at moderate to atmospheric pressures (1 to 10 atm) using hydrodynamic plasma modeling approach, were demonstrated. In addition, results of experiments with pulsed+bias DBD configuration that were performed for validation purposes are reported.

Likhanskii, Alexandre

2012-01-01

23

Investigation of asymmetric dielectric barrier discharge plasma actuator, driven by repetitive nanosecond pulses.  

NASA Astrophysics Data System (ADS)

DBD plasma actuators are known to be effective for low speed flow control. A comprehensive physically-based numerical model has been developed for explanation of DBD operation. The modeling showed the advantages of using repetitive nanosecond pulses with bias over the sine voltage. If the sine voltage is applied, it carries two functions -- plasma generation and producing the body force on the gas. In the pulse case these processes are separated. The plasma is generated using repetitive nanosecond pulses, and the driving of charge particles, which produces the force on the gas, is between the pulses. In pulse configuration the variation of pulse amplitude, sign and the voltage between pulses can produce different force and heating effects on the flow. The verification of the modeling has been done in the experimental investigation of DBD. A new experimental approach for non-intrusive diagnostic of DBD induced flows in quiescent gas was proposed. The schlieren technique, burst mode of plasma actuator operation, and 2D Navier-Stokes numerical model coupled together allowed restoring the entire 2D induced flow and characteristics of the plasma induced force.

Likhanskii, Alexandre; Opaits, Dmitry; Shneider, Mikhail; Macheret, Sergey; Miles, Richard

2007-10-01

24

American Institute of Aeronautics and Astronautics Microscale Dielectric Barrier Discharge Plasma Actuators  

E-print Network

American Institute of Aeronautics and Astronautics 1 Microscale Dielectric Barrier Discharge Plasma by the Authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. DownloadedbySubrataRoyonDecember27,2012|http://arc.aiaa.org|DOI:10.2514/6.2012-3091 #12;American Institute

Roy, Subrata

25

Power consumption, discharge capacitance and light emission as measures for thrust production of dielectric barrier discharge plasma actuators  

SciTech Connect

A new procedure of determining the time resolved capacitance of a plasma actuator during operation is introduced, representing a simple diagnostic tool that provides insight into the phenomenological behavior of plasma actuators. The procedure is demonstrated by presenting example correlations between consumed electrical energy, size of the plasma region, and the operating voltage. It is shown that the capacitance of a plasma actuator is considerably increased by the presence of the plasma; hence a system that has previously been impedance matched can be considerably de-tuned when varying the operating voltage of the actuator. Such information is fundamental for any attempts to increase the energy efficiency of plasma-actuator systems. A combined analysis of the capacitance, light emission, size of the plasma region, force production, and power consumption is presented.

Kriegseis, J. [Institute of Fluid Mechanics and Aerodynamics, Technische Universitaet Darmstadt, Flughafenstr. 19, D-64347 Greisheim (Germany); Grundmann, S. [Center of Smart Interfaces, Technische Universitaet Darmstadt, Flughafenstr. 19, D-64347 Greisheim (Germany); Tropea, C. [Institute of Fluid Mechanics and Aerodynamics, Technische Universitaet Darmstadt, Flughafenstr. 19, D-64347 Greisheim (Germany); Center of Smart Interfaces, Technische Universitaet Darmstadt, Flughafenstr. 19, D-64347 Greisheim (Germany)

2011-07-01

26

Scaling of maximum velocity, body force, and power consumption of dielectric barrier discharge plasma actuators via particle image velocimetry  

NASA Astrophysics Data System (ADS)

This study presents Particle Image Velocimetry (PIV) measurements of the induced flow characteristics generated by single dielectric barrier discharge (DBD) actuators in quiescent conditions. The primary aim is to establish accurate empirical trends for model development on both the maximum induced velocity and body force with voltage and consumed power. The results reveal a power law variation for the maximum velocity at low voltages which is followed by an asymptotic behavior. In contrast, the body force is characterized by two power law regions. The power law exponent is shown to be a function of the dielectric thickness, frequency and dielectric constant. Reducing the former or increasing the latter two result in a higher coefficient and lower voltage at which the trend changes. The onset of the second region occurs at a Re 100 (based on the maximum velocity, um, and corresponding half height, y1/2) and is characterized by a velocity profile which no longer agrees with the laminar profile of Glauert whilst moving increasingly towards the turbulent case. Phase locked PIV measurements show that as the voltage increases the peak momentum transfer shifts from the middle of the AC cycle to the latter end of the forward stroke. Lissajous plots of um? against the corresponding x location and plasma length ?x demonstrate that the peak momentum transfer remains relatively fixed in space as the voltage and plasma length increase.

Murphy, J. P.; Kriegseis, J.; Lavoie, P.

2013-06-01

27

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)

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.

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

2008-08-01

28

Serpentine geometry plasma actuators for flow control  

NASA Astrophysics Data System (ADS)

In this paper, a curved class of plasma actuator geometries is presented. The intension of this paper is to extend the versatility of a dielectric barrier discharge plasma actuator by modifying the geometry of its electrodes, so that the plasma generated body force is able to excite a broader spectrum of flow physics than plasma actuators with a more standard geometry. Two examples of flow control are demonstrated numerically. An example of this class of actuators is shown to generate boundary layer streaks, which can be used to accelerate or delay the laminar to turbulent transition process, depending on how they are applied. Simulations of a low Reynolds number airfoil are also performed using additional examples of this class of actuators, where it is shown that this plasma actuator geometry is able to introduce energy into and excite a secondary instability mode and increase unsteady kinetic energy in the boundary layer. These two cases show that this general class of curved actuators possesses an increased versatility with respect to the standard geometry actuators.

Riherd, Mark; Roy, Subrata

2013-08-01

29

Plasma actuators for bluff body flow control  

NASA Astrophysics Data System (ADS)

The aerodynamic plasma actuators have shown to be efficient flow control devices in various applications. In this study the results of flow control experiments utilizing single dielectric barrier discharge plasma actuators to control flow separation and unsteady vortex shedding from a circular cylinder in cross-flow are reported. This work is motivated by the need to reduce landing gear noise for commercial transport aircraft via an effective streamlining created by the actuators. The experiments are performed at Re D = 20,000...164,000. Circular cylinders in cross-flow are chosen for study since they represent a generic flow geometry that is similar in all essential aspects to a landing gear oleo or strut. The minimization of the unsteady flow separation from the models and associated large-scale wake vorticity by using actuators reduces the radiated aerodynamic noise. Using either steady or unsteady actuation at ReD = 25,000, Karman shedding is totally eliminated, turbulence levels in the wake decrease significantly and near-field sound pressure levels are reduced by 13.3 dB. Unsteady actuation at an excitation frequency of St D = 1 is found to be most effective. The unsteady actuation also has the advantage that total suppression of shedding is achieved for a duty cycle of only 25%. However, since unsteady actuation is associated with an unsteady body force and produces a tone at the actuation frequency, steady actuation is more suitable for noise control applications. Two actuation strategies are used at ReD = 82,000: spanwise and streamwise oriented actuators. Near field microphone measurements in an anechoic wind tunnel and detailed study of the near wake using LDA are presented in the study. Both spanwise and streamwise actuators give nearly the same noise reduction level of 11.2 dB and 14.2 dB, respectively, and similar changes in the wake velocity profiles. The contribution of the actuator induced noise is found to be small compared to the natural shedding noise. A tandem cylinder configuration with the plasma actuation on the upstream cylinder is investigated using surface dynamic pressure sensors. As a result of the plasma actuation, the surface pressure fluctuations on the downstream cylinder are reduced by about two times at the free-stream velocity of 40 m/s (ReD = 164,000). In addition, this study presents the results of a parametric experimental investigation aimed at optimizing the body force produced by single dielectric barrier discharge (SDBD) plasma actuators used for aerodynamic flow control. A primary goal of the study is the improvement of actuator authority for flow control applications at higher Reynolds number than previously possible. The study examines the effects of dielectric material and thickness, applied voltage amplitude and frequency, voltage waveform, exposed electrode geometry, covered electrode width and multiple actuator arrays. The metric used to evaluate the performance of the actuator in each case is the measured actuator-induced thrust which is proportional to the total body force. It is demonstrated that actuators constructed with thick dielectric material of low dielectric constant and operated at low frequency AC voltage produce a body force that is an order of magnitude larger than that obtained by the Kapton-based actuators used in many previous plasma flow control studies. These actuators allow operation at much higher applied voltages without the formation of discrete streamers which lead to body force saturation.

Kozlov, Alexey V.

30

Thrust Measurement of Dielectric Barrier Discharge (DBD) Plasma Actuators: New Anti-Thrust Hypothesis, Frequency Sweeps Methodology, Humidity and Enclosure Effects  

NASA Technical Reports Server (NTRS)

We discuss thrust measurements of Dielectric Barrier Discharge (DBD) plasma actuators devices used for aerodynamic active flow control. After a review of our experience with conventional thrust measurement and significant non-repeatability of the results, we devised a suspended actuator test setup, and now present a methodology of thrust measurements with decreased uncertainty. The methodology consists of frequency scans at constant voltages. The procedure consists of increasing the frequency in a step-wise fashion from several Hz to the maximum frequency of several kHz, followed by frequency decrease back down to the start frequency of several Hz. This sequence is performed first at the highest voltage of interest, then repeated at lower voltages. The data in the descending frequency direction is more consistent and selected for reporting. Sample results show strong dependence of thrust on humidity which also affects the consistency and fluctuations of the measurements. We also observed negative values of thrust, or "anti-thrust", at low frequencies between 4 Hz and up to 64 Hz. The anti-thrust is proportional to the mean-squared voltage and is frequency independent. Departures from the parabolic anti-thrust curve are correlated with appearance of visible plasma discharges. We propose the anti-thrust hypothesis. It states that the measured thrust is a sum of plasma thrust and anti-thrust, and assumes that the anti-thrust exists at all frequencies and voltages. The anti-thrust depends on actuator geometry and materials and on the test installation. It enables the separation of the plasma thrust from the measured total thrust. This approach enables more meaningful comparisons between actuators at different installations and laboratories. The dependence on test installation was validated by surrounding the actuator with a grounded large-diameter metal sleeve. Strong dependence on humidity is also shown; the thrust significantly increased with decreasing humidity, e.g., 44 percent increase as relative humidity changed from 18 percent and dew point 33 degF to 50 percent and dew point of 57 degF.

Ashpis, David E.; Laun, Matthew C.

2014-01-01

31

Control of an axisymmetric subsonic air jet by plasma actuator  

Microsoft Academic Search

It is known that surface non-thermal plasma actuators have proved their efficiency for aerodynamics flow control. In this\\u000a study, a dielectric barrier discharge (DBD) is mounted on the diffuser of an axisymmetric turbulent air jet in order to control\\u000a the flow separation along a 12-degree diffuser bevel. The momentum created by the actuator is applied to separate an air flow

N. Benard; J. Jolibois; M. Forte; G. Touchard; E. Moreau

2007-01-01

32

On the role of oxygen in dielectric barrier discharge actuation of aerodynamic flows  

SciTech Connect

Phase-locked particle image velocimetry is used to study the mechanism of induced flow in the near field of a rf dielectric barrier discharge actuator mounted in the separated flow region of a bluff body. Flow actuation is found to be asymmetric, with suction toward the buried downstream electrode when it is biased positively relative to the upstream exposed electrode. Lesser flow is seen on the reverse voltage swing, where the buried electrode should attract positive ions. This phenomenon is enhanced when oxygen is added to the flow, suggesting that oxygen negative ions, possibly O{sub 2}{sup -}, play a dominant role in plasma actuation.

Kim, W.; Do, H.; Mungal, M. G.; Cappelli, M. A. [Mechanical Engineering Department, Stanford University, Stanford, California 94305-3032 (United States)

2007-10-29

33

Surface plasma actuators modeling for flow control  

NASA Astrophysics Data System (ADS)

The surface plasma actuators over the entire speed region have been intensely investigated for flow control. Most of the fundamental phenomena have been firmly identified by experimental observations but ambiguities still remained. The direct computational simulation for multiple microdischarges is presently beyond our reach, thus the essential physics may be better understood on the framework of physics-based modeling. To achieve this objective, the drift-diffusion approximation is adopted as a transport property approximation to the nonequilibrium air plasma. The most challenging issue of electron impact ionization process at the low-temperature environment is addressed by the Townsend mechanism together with electron attachment, detachment, bulk, and ion-ion recombination. The effects and quantifications of Joule heating, periodic electrostatic force, as well as, the Lorentz acceleration for flow control are examined. The clarification to the hot spot of heat transfer in direct current discharge and the orientations of the periodic force associated with AC cycle of dielectric barrier discharge are also included.

Shang, J. S.; Huang, P. G.

2014-05-01

34

Research on the Peristaltic Flow Acceleration Performance of Asynchronous and Duty Cycle Pulsed DBD Plasma Actuation  

NASA Astrophysics Data System (ADS)

Using a plexiglas plate model, the performance of peristaltic flow acceleration induced by multiple DBD (dielectric barrier discharge) plasma actuators was studied based on PIV (particle image velocimetry). The asynchronous and the duty cycle pulsed actuation modes were proposed and tested. The velocity fields induced by multiple DBD plasma actuators with different phase angles and duty cycle ratios were acquired and the momentum transfer characteristics of the flow field were discussed. Consequently, the mechanism of the peristalsis-acceleration multiple DBD plasma actuation was analyzed. The results show that the peristaltic flow acceleration effect of multiple plasma actuators occurs mainly in paraelectric direction, and the mechanism of peristaltic flow acceleration is ejection pushing effect rather than injection pumping effect. The asynchronous and the duty cycle pulsed actuation modes can, with energy consumption increase of merely 10%, achieve 65% and 42% increase of downstream velocity, and thus are promising in velocity improvement and energy saving.

Li, Feng; Gao, Chao; Zheng, Borui; Wang, Yushuai

2014-09-01

35

Hybrid transition control approach for plasma actuators  

NASA Astrophysics Data System (ADS)

This work reports on the development of a novel hybrid transition control method for single DBD plasma actuators. The experiments have been carried out on a natural laminar flow airfoil in a wind tunnel and combine two methods previously used for transition control purposes with DBD plasma actuators: boundary-layer stabilization by quasi-steady wall-parallel momentum addition, and active wave cancelation by linear superposition utilizing modulated momentum injection. For this purpose, the modulated body force is controlled using an improved extremum seeking controller based on an extended Kalman filter. Combining the two methods in a single actuator has advantages. Applied to 2-D Tollmien-Schlichting waves, the achievable transition delay in hybrid mode is significantly larger than the isolated effects, while the energy consumption remains almost unchanged compared to the case of continuous actuation. For a Reynolds number of , a transition delay of could be observed.

Kurz, A.; Goldin, N.; King, R.; Tropea, C.; Grundmann, S.

2013-11-01

36

Use of Plasma Actuators as a Moving-Wake Generator  

NASA Technical Reports Server (NTRS)

The work documented in this report tests the concept of using plasma actuators as a simple and easy way to generate a simulated moving-wake and the disturbances associated with it in turbines. This wake is caused by the blades of the upstream stages of the turbine. Two types of devices, one constructed of arrays of NACA 0018 airfoils, and the one constructed of flat plates were studied. The airfoils or plates were equipped with surface mounted dielectric barrier discharge (DBD) plasma actuators, which were used to generate flow disturbances resembling moving-wakes. CTA hot-wire anemometry and flow visualization using a smoke-wire were used to investigate the wake independence at various spacings and downstream locations. The flat plates were found to produce better results than the airfoils in creating large velocity fluctuations in the free-stream flow. Different dielectric materials, plasma actuator locations, leading edge contours, angles of attack and plate spacings were investigated, some with positive results. The magnitudes of the velocity fluctuations were found to be comparable to existing mechanical moving-wake generators, thus proving the feasibility of using plasma actuators as a moving-wake generator.

Corke, Thomas C.; Thomas, Flint O.; Klapetzky Michael J.

2007-01-01

37

Three-dimensional effects of curved plasma actuators in quiescent air  

SciTech Connect

This paper presents results on a new class of curved plasma actuators for the inducement of three-dimensional vortical structures. The nature of the fluid flow inducement on a flat plate, in quiescent conditions, due to four different shapes of dielectric barrier discharge (DBD) plasma actuators is numerically investigated. The three-dimensional plasma kinetic equations are solved using our in-house, finite element based, multiscale ionized gas (MIG) flow code. Numerical results show electron temperature and three dimensional plasma force vectors for four shapes, which include linear, triangular, serpentine, and square actuators. Three-dimensional effects such as pinching and spreading the neighboring fluid are observed for serpentine and square actuators. The mechanisms of vorticity generation for DBD actuators are discussed. Also the influence of geometric wavelength ({lambda}) and amplitude ({Lambda}) of the serpentine and square actuators on vectored thrust inducement is predicted. This results in these actuators producing significantly better flow mixing downstream as compared to the standard linear actuator. Increasing the wavelengths of serpentine and square actuators in the spanwise direction is shown to enhance the pinching effect giving a much higher vertical velocity. On the contrary, changing the amplitude of the curved actuator varies the streamwise velocity significantly influencing the near wall jet. Experimental data for a serpentine actuator are also reported for validation purpose.

Wang Chincheng; Durscher, Ryan; Roy, Subrata

2011-04-15

38

Experimental Results in DBD Plasma Actuators for Air Flow Control  

Microsoft Academic Search

In this paper, several planar dielectric barrier discharge fluid-dynamics actuators have been experimentally investigated. The actuator is made by an electrode pair separated by a dielectric. It is characterized by a planar geometry, and it induces a volume force on the gas above it which modifies the fluid dynamics within the aerodynamic boundary layer. Several actuator geometries, dielectric materials, ac

Gabriele Neretti; Andrea Cristofolini; Carlo A. Borghi; Alessandro Gurioli; Roberto Pertile

2012-01-01

39

Separation Control in a 3D Diffuser using Plasma Actuators  

NASA Astrophysics Data System (ADS)

Control experiments were conducted for the fully-turbulent flow in a 3D diffuser with an expansion ratio of 4.8. The uncontrolled flow for the same diffuser has a stable, three-dimensional separation zone which begins as a slender bubble in one corner before spreading across the entire width of the diffuser, giving the opportunity to develop and test active separation control devices. Dielectric-barrier discharge actuators were used to actively control the flow separation with the goal of improving the pressure recovery. The most effective control was achieved using spanwise acting plasma actuators in the inlet section of the diffuser which create streamwise vortices. The pressure recovery can be clearly improved or degraded depending on whether the actuators are operated pulsed or continuously. Parameter studies showed the dependence of the pressure recovery along the diffuser wall on the actuator operating parameters, including the modulation frequency and duty cycle. Velocity profile measurements in the inlet and outlet planes of the diffuser show the creation of the streamwise vortices and their influence on the uniformity of the velocity in the end of the diffuser. Frequency spectra taken in the exit plane using a hotwire probe show the influence of the operating parameters on the diffuser flow. A closed-loop control circuit for the automated adaption of the operating parameters is being tested.

Grundmann, Sven; Eaton, John K.

2009-11-01

40

Comparisons of Force Measurement Methods for DBD Plasma Actuators in Quiescent Air  

NASA Technical Reports Server (NTRS)

We have performed measurements of the force induced by both single (one electrode insulated) and double (both electrodes insulated) dielectric barrier discharge plasma actuators in quiescent air. We have shown that, for single barrier actuators with cylindrical exposed electrodes, as the electrode diameter decrease the force efficiencies increase much faster than a previously reported linear trend. This behavior has been experimentally verified using two different measurement techniques: stagnation probe measurements of the induced flow velocity and direct measurement of the force using an electronic balance. Actuators with rectangular cross-section exposed electrodes do not show the same rapid increase at small thicknesses. We have also shown that the induced force is independent of the material used for the exposed electrode. The same techniques have shown that the induced force of a double barrier actuator increases with decreasing narrow electrode diameter.

Hoskinson, Alan R.; Hershkowitz, Noah; Ashpis, David E.

2009-01-01

41

Circular cylinder drag reduction by three-electrode plasma actuators  

Microsoft Academic Search

The drag reduction in a circular cylinder was explored by means of a novel three electrode plasma actuator (DBDE). The DBDE actuator can reduce the drag coefficient up to a ~25% respect to the base flow drag coefficient. It has been demonstrated that, within the present experimental conditions, the DBDE actuator, for a fixed value of the power coefficient, adds

R. Sosa; J. D'Adamo; G. Artana

2009-01-01

42

Shock Generation and Control Using DBD Plasma Actuators  

NASA Technical Reports Server (NTRS)

This report is the final report of a NASA Phase I SBIR contract, with some revisions to remove company proprietary data. The Shock Boundary Layer Interaction (SBLI) phenomena in a supersonic inlet involve mutual interaction of oblique shocks with boundary layers, forcing the boundary layer to separate from the inlet wall. To improve the inlet efficiency, it is desired to prevent or delay shock-induced boundary layer separation. In this effort, Innovative Technology Applications Company (ITAC), LLC and the University of Notre Dame (UND) jointly investigated the use of dielectric-barrier-discharge (DBD) plasma actuators for control of SBLI in a supersonic inlet. The research investigated the potential for DBD plasma actuators to suppress flow separation caused by a shock in a turbulent boundary layer. The research involved both numerical and experimental investigations of plasma flow control for a few different SBLI configurations: (a) a 12 wedge flow test case at Mach 1.5 (numerical and experimental), (b) an impinging shock test case at Mach 1.5 using an airfoil as a shock generator (numerical and experimental), and (c) a Mach 2.0 nozzle flow case in a simulated 15 X 15 cm wind tunnel with a shock generator (numerical). Numerical studies were performed for all three test cases to examine the feasibility of plasma flow control concepts. These results were used to guide the wind tunnel experiments conducted on the Mach 1.5 12 degree wedge flow (case a) and the Mach 1.5 impinging shock test case (case b) which were at similar flow conditions as the corresponding numerical studies to obtain experimental evidence of plasma control effects for SBLI control. The experiments also generated data that were used in validating the numerical studies for the baseline cases (without plasma actuators). The experiments were conducted in a Mach 1.5 test section in the University of Notre Dame Hessert Laboratory. The simulation results from cases a and b indicated that multiple spanwise actuators in series and at a voltage of 75 kVp-p could fully suppress the flow separation downstream of the shock. The simulation results from case c showed that the streamwise plasma actuators are highly effective in creating pairs of counter-rotating vortices, much like the mechanical vortex generators, and could also potentially have beneficial effects for SBLI control. However, to achieve these effects, the positioning and the quantity of the DBD actuators used must be optimized. The wind tunnel experiments mapped the baseline flow with good agreement to the numerical simulations. The experimental results were conducted with spanwise actuators for cases a and b, but were limited by the inability to generate a sufficiently high voltage due to arcing in the wind-tunnel test-section. The static pressure in the tunnel was lower than the static pressure in an inlet at flight conditions, promoting arching and degrading the actuator performance.

Patel, Mehul P.; Cain, Alan B.; Nelson, Christopher C.; Corke, Thomas C.; Matlis, Eric H.

2012-01-01

43

Investigation of microscale dielectric barrier discharge plasma devices  

NASA Astrophysics Data System (ADS)

This dissertation presents research performed on reduced-scale dielectric barrier discharge (DBD) plasma actuators. A first generation of microscale DBD actuators are designed and manufactured using polymeric dielectric layers, and successfully demonstrate operation at reduced scales. The actuators are 1 cm long and vary in width from tens of microns to several millimeters. A thin-film polymer or ceramic material is used as the dielectric barrier with thicknesses from 5 to 20 microns. The devices are characterized for their electrical, fluidic and mechanical performance. With electrical input of 5 kVpp, 1 kHz, the microscale DBD actuators induce a wall jet with velocity reaching up to 2 m/s and produce 3.5 mN/m of thrust, while consuming an average power of 20 W/m. A 5 mN/m plasma body force was observed, acting on the surrounding air. Failure of the microscale DBD actuators is investigated using thermal measurements of the dielectric surface in addition to both optical and scanning electron microscopy. The cause of device failure is identified as erosion of the dielectric surface due to collisions with ions from the discharge. A second generation of microscale actuators is then designed and manufactured using a more reliable dielectric material, namely silicon dioxide. These actuators demonstrate a significant improvement in device lifetime compared with first-generation microscale DBD actuators. The increase in actuator lifetime allowed the electrical, fluidic and mechanical characterization to be repeated over several input voltages and frequencies. At 7 kVpp, 1 kHz, the actuators with SiO2 dielectric induced velocities up to 1.5 m/s and demonstrated 1.4 mN/m of thrust while consuming an average power of 41 W/m. The plasma body force reached up to 2.5 mN/m. Depending on electrical input, the induced velocity and thrust span an order of magnitude in range. Comparisons are made with macroscale DBD actuators which relate the actuator's output performance and power consumption with the mass and volume of the actuator design. The small size and of microscale DBD actuators reduces its weight and power requirements, making them attractive for portable or battery-powered applications (e.g., on UAVs).

Zito, Justin C.

44

Electro-actuation characteristics of Cl2 and SF6 plasma-treated IPMC actuators  

NASA Astrophysics Data System (ADS)

This paper describes plasma treatments that improve the actuation properties by modifying the surface morphology of ionic polymer metal composites (IPMC). The proposed Cl2 and SF6 plasmas change the surface appearance of the electroactive polymer, and scanning electron microscopy (SEM) of the plasma-treated surfaces reveals the development of round and cone-shaped microstructures. After electroless chemical metal plating, these microstructures significantly alter the characteristics of the IPMC electrode. In plasma-treated IPMCs, the densely packed platinum nanoparticles have produced a relatively thick electrode layer. This configuration has led to the improvement in the electrical properties of the IPMC: surface resistance is noticeably decreased, whereas electrical capacitance is increased. These changes in the electrical properties have considerably enhanced the actuation parameters: displacement, force and operational life are increased by more than three times relative to the conventional IPMC. Our experimental data suggest a relationship between the IPMC actuator's electrical properties and actuation parameters: actuators with lower surface resistance generate large deflection and actuators with higher capacitance generate large actuation force. The actuation tests including coin lifting suggests the potential of the modified IPMC for artificial muscle applications.

Saher, Saim; Kim, Woojin; Moon, Sungwon; Kim, H. Jin; Hyup Kim, Yong

2010-10-01

45

Schlieren imaging in a dielectric barrier discharge actuator for airflow control  

NASA Astrophysics Data System (ADS)

The operation of a surface dielectric barrier discharge actuator for airflow control has been experimentally investigated. The actuator is constituted by an electrode pair separated by a dielectric Teflon sheet. Several ac supply conditions have been utilized. An electrohydrodynamics interaction was induced in still air, and several fluid-dynamic regimes were obtained. Visualization of the plasma boundary layer during the discharge ignition phase and during the steady state regime was obtained by utilizing a Schlieren diagnostic technique. The vortex morphology and propagation velocities at all supply conditions utilized have been evaluated. Velocity profiles perpendicular to the actuator surface, obtained from Pitot tube measurements, and line intensity profiles, determined by means of Schlieren imaging, have been determined for the steady regime operation. The integral along a line perpendicular to the actuator surface of the light intensity of the Schlieren image has been calculated. The profile obtained is in good agreement with the Pitot velocity profile in all the supply conditions investigated. Numerical simulations were also performed. The calculations confirm the relation between the flow velocity distribution in the boundary layer and the gas density distribution, which is the cause of the Schlieren image.

Cristofolini, A.; Neretti, G.; Roveda, F.; Borghi, C. A.

2012-02-01

46

Variable Structure Model for Flow-Induced Tonal Noise Control with Plasma Actuators  

E-print Network

to the plasma actuator [3]. More recently, plasma actuator technology has been applied to aeroacousticVariable Structure Model for Flow-Induced Tonal Noise Control with Plasma Actuators Xun Huang of plasma actuators in attenuating low-speed flow-induced cavity tones from a control point of view

Huang, Xun

47

Separation control over low pressure turbine blades using plasma actuators  

NASA Astrophysics Data System (ADS)

This work involved the documentation and control of flow separation that occurs over low pressure turbine (LPT) blades at low Reynolds numbers. A specially constructed linear cascade was utilized to study the flow field over a generic LPT cascade consisting of Pratt & Whitney "PakB" shaped blades. Flow visualization, pressure measurements, LDV measurements; and hot-wire measurements were conducted to examine the flow fields with and without separation control. Experimental conditions were chosen to give a range of chord Reynolds numbers from 10,000 to 100,000, and a range of freestream turbulence intensities from u'/ Uinfinity = 0.08% to 2.85%. The blade pressure distributions were measured and used to define a region of separation that depends on the freestream conditions. The location of separation was found to be relatively insensitive to the experimental conditions. However, the reattachment location was very sensitive to the Reynolds number and the turbulence intensity. Separation control was performed using plasma actuators. Both steady and unsteady actuation were implemented and found to work well. For the steady actuators, it was found that the separation control is the most effective when applied slightly upstream the separation location. There exists a threshold plasma amplitude for the actuator to take effect for separation control. However, the effectiveness of the actuator is saturated when the plasma amplitude is greater than certain value. The effectiveness of the steady actuator is not sensitive to the orientation of the plasma electrodes. For the unsteady actuators, there exists an optimum excitation frequency at which the unsteady actuator was the most effective. The optimum excitation frequency was corresponded to the unity Strouhal number, which is defined as St = fLsep/Umid-channel. It was also found that lowest plasma duty cycle (10% in this work) was as effective as the highest plasma duty cycle (50% in this work). This has an advantage for reducing the power to the actuators. The comparison between the steady and unsteady actuators showed that the unsteady actuators worked better than the steady ones. The mechanisms of the steady and unsteady plasma actuators were studied. It was suggested by the experimental results that the mechanism for the steady actuators is turbulence tripping, while the mechanism for the unsteady actuators is to generate a train of spanwise structures that promote mixing.

Huang, Junhui

48

Mechanism of flow separation control using plasma actuation  

NASA Astrophysics Data System (ADS)

The mechanism of flow separation control was investigated experimentally and computationally using pulse-modulated dielectric barrier discharge (DBD) plasma actuation on a stalled flat plate airfoil at a Reynolds number of 3000. Load measurements were complimented with two-dimensional phase-averaged particle image velocimetry performed in the flowfield above the airfoil. A parametric study was carried out where the pulse-modulation frequency, duty cycle, and peak plasma body-force were varied. The two-dimensional Navier-Stokes equations, with no turbulence modeling, were solved directly using a commercial flow solver and a simple but satisfactory heuristic DBD plasma body-force model was incorporated. The overall experimental trends were well predicted by the computations, where the frequencies that produced the largest increases in lift coefficient excited bluff-body shedding at a frequency corresponding approximately to its unforced sub-harmonic. At non-dimensional frequencies most effective for increasing lift (0.2 to 0.5), the leading-edge shear layer was severed by the perturbations and then merged with a downstream vortex. In a time-mean sense this mechanism forced relatively high momentum fluid towards the surface with typically two re-circulating structures present on the airfoil. Although the essential flow control mechanism was captured by the computation, the idealized 2D approach was identified as a weakness due to the shedding instability not being present in the baseline experiments and the inability to account for three-dimensional structures in the shear layer.

Greenblatt, David; Schneider, Torsten; Schle, Chan Yong

2012-07-01

49

Sensitivity of an asymmetric 3D diffuser to plasma-actuator induced inlet condition perturbations  

NASA Astrophysics Data System (ADS)

Experiments were conducted for the flow in a straight-walled 3D diffuser fed by a fully developed turbulent duct flow. Previous work found that this diffuser has a stable 3D separation bubble whose configuration is affected by the secondary flows in the upstream duct. Dielectric barrier discharge plasma actuators were used to produce low-momentum wall jets to determine if the separation behavior could be modified by weak forcing. Actuators producing a streamwise force along the wall where separation occurred in the baseline flow had a relatively small effect. However, spanwise acting plasma actuators that produced a pair of streamwise vortices in the inlet section of the diffuser had a strong effect on the diffuser pressure recovery. The diffuser performance could be either improved or degraded depending on the actuation parameters, including the actuator modulation frequency, duty cycle, and drive voltage. Velocity profile measurements in the diffuser inlet showed that the streamwise vortices affect the uniformity of the streamwise mean velocity accounting for some of the performance changes. However, phase-locked hotwire measurements at the diffuser exit indicate that the periodic nature of the forcing also plays an important role for cases with enhanced pressure recovery.

Grundmann, S.; Sayles, E. L.; Eaton, J. K.

2011-01-01

50

Numerical simulation of a plasma actuator based on ion transport  

SciTech Connect

Two-dimensional numerical simulation of ion transport and flow around a single dielectric barrier discharge plasma actuator (PA) is performed. Spatial distributions of ions and electrons as well as their time evolution are obtained by solving the transport equations of monovalent positive ions, monovalent negative ions, and electrons. Voltage and frequency of the driving alternating-current signal are assumed to be 8 kV and 5 kHz, respectively. Special focus is laid upon the effect of voltage gradient dV/dt on the magnitude of the body force. The validity of steady force models often used in flow simulation is also examined. The simulation results show that the magnitude of the body force induced by the PA increases as the voltage gradient dV/dt increases and its increase rate becomes milder at higher voltage. The mechanism of body force generation is explained from the time evolution of number density fields of ions and electrons. A comparison between flow simulations using a time-resolved body force and its time-averaged counterpart demonstrates that the time-averaged model gives sufficiently accurate results when the time scale of the flow is more than 30 times greater than that of the PA.

Yamamoto, Seiya; Fukagata, Koji [Department of Mechanical Engineering, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522 (Japan)] [Department of Mechanical Engineering, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522 (Japan)

2013-06-28

51

Controlling shedding from circular cylinders using plasma actuators  

NASA Astrophysics Data System (ADS)

Plasma actuators were used to control the phase relationship between vortex shedding from two side-by-side circular cylinders from Red = 16,700 to 76,500 in a low-speed flow. The motivation was to create, in a compressible cascade, a 'clean' and predictable upstream-propagating potential disturbance using synchronized shedding from a row of multiple cylinders so that the interaction of the disturbance with the trailing edge of a cascade vane could be investigated. In the low-speed flow, two cylinders of L/d = 8 were installed perpendicular to the flow, with the pitch-to-diameter ratio of 4. The 'natural' vortex shedding for this spacing is, predominantly, 180 out-of-phase. The performance of the plasma actuators was best, when they were installed on the sides (approximately +/-90 from the forward stagnation point) of each cylinder, along the full span. These actuators, by the formation of plasma, produce an air jet in downstream direction. The phase relationship of vortex shedding was determined using cross correlation of streamwise velocities, measured by hot-wire probes located downstream of each cylinder at symmetric positions with respect to the cylinder axes. The cross correlation of the unsteady velocities showed the effectiveness of the plasma actuators in phase synchronizing the vortex shedding. The coefficients of +0.4 to +0.6 (or -0.6 to -0.4) were obtained when the plasma actuators were activated, showing the in-phase (or out-of-phase) synchronization of the vortex shedding. The effectiveness of the plasma actuators was further demonstrated by the arbitrary-phase synchronization of vortex shedding. The phase synchronization up to the Reynolds number of 76,500 was obtained. No other method has been able to achieve the vortex-shedding control up to this high a Reynolds number. The power input to the actuators, before reaching a certain asymptotic value, increased with the increase in Reynolds number. The phase synchronization was sensitive to the excitation frequency, input power, and Reynolds number. Flow visualization was used to obtain a global view of the phase-synchronized shedding. The spanwise coherence of vortex shedding increased when the flow was excited. The upstream effect of the phase-synchronized shedding of cylinders in the low-speed flow (Re = 16,700) was investigated using PIV. The controlled in-phase shedding also produced a synchronized unsteady velocity field upstream of the cylinders. Through the scaling of the body force produced by the plasma actuator, it is demonstrated that it is possible to phase synchronize vortex shedding in a higher-speed, weakly-compressible, geometrically-similar flow.

Asghar, Asad

52

Separation control in low pressure turbines using plasma actuators with passing wakes  

NASA Astrophysics Data System (ADS)

A Dielectric Barrier Discharge (DBD) plasma actuator is operated in flow over the suction surface of a Pack-B Low Pressure Turbine (LPT) airfoil at a Reynolds number of 50,000 (based on exit velocity and suction surface length) and inlet free-stream turbulence intensity of 2.5%. Preliminary characterization studies were made of the effect of varying actuator pulsing frequency and duty cycle, actuator edge effects, and orientation of the actuator with the flow. Flow control was demonstrated with the actuator imparting momentum opposite to the stream-wise flow direction, showing that it is possible to use disturbances alone to destabilize the flow and effect transition. No frequencies of strong influence were found over the range tested, indicating that a broad band of effective frequencies exists. Edge effects were found to considerably enhance separation control. Total pressure measurements of the flow without passing wakes were taken using a glass total-pressure tube. Corrections for streamline displacement due to shear and wall effects were made, and comparisons with previous hot-wire measurements were used to validate data. Performance features of conventional two-electrode and a novel three-electrode actuator configuration were compared. Hot-wire anemometry was used to take time-varying ensemble-averaged near-wall velocity measurements of the flow with periodic passing wakes. Corrections were made for near-wall effects, temperature effects, and interference of the electric field. The wakes were generated by a wake generator mechanism located upstream of the airfoil passage. The near-suction-surface total pressure field (flow without wakes) and velocity field (flow with wakes) in the trailing part of the airfoil passage, and the wall-normal gradient of these quantities, were used to demonstrate effective prevention of flow separation using the plasma actuator. Both flows (with and without passing wakes) showed fully attached flow (or very thin separation zones) when the actuator was activated. The flow with passing wakes and the actuator on showed relatively little time variation in the boundary layer, and qualitative similarities to the corresponding flow without passing wakes and with the actuator on were noted.

Burman, Debashish

53

Mechanisms of plasma actuators for hypersonic flow control  

NASA Astrophysics Data System (ADS)

A summary of recent research progress in hypersonic plasma actuators for flow control is attempted. It is found that the most effective plasma actuator is derived from an electromagnetic perturbation and amplifies by a subsequent viscous-inviscid interaction. Computational efforts using drift-diffusion theory and a simple phenomenological plasma model, as well as experiments in a hypersonic plasma channel, have shown the effectiveness of using electro-aerodynamic interaction as a hypersonic flow control mechanism. In principle, the plasma actuator based on magneto-aerodynamic interaction should have an added mechanism in the Lorentz force, making it even more effective as a flow control mechanism. However, this approach also incurs additional challenges and complications due to the Hall effect. Magneto-aerodynamic interactions have also been demonstrated for separated flow control, albeit in a very limited scope. Numerical simulations based on a simple phenomenological plasma model have shown the feasibility of separated flow suppression in shock-boundary-layer interaction over a compression ramp at a hypersonic flow of Mach 14.1. The control mechanism relies on the Lorentz force to energize the retarded shear layer in the viscous interacting region, but the effectiveness of momentum transfer via inelastic collision requires further validation.

Shang, J. S.; Surzhikov, S. T.; Kimmel, R.; Gaitonde, D.; Menart, J.; Hayes, J.

2005-11-01

54

The response of a flat plate boundary layer to an orthogonally arranged dielectric barrier discharge actuator  

NASA Astrophysics Data System (ADS)

The jetting characteristics of dielectric barrier discharge (DBD) actuators make these devices suitable for augmenting boundary layer flows. The associated change to the hydrodynamic stability of the fluid arising from the actuator provides a mechanism through which a DBD-based laminar flow control (LFC) system can be developed. Historically, DBD actuators with electrodes arranged parallel to each other have been used for LFC with mixed results. An alternative is to use an actuator with electrodes placed orthogonally to each other. Orthogonally arranged actuators exhibit different jetting characteristics to conventional ones, and as such understanding the effect that these actuators have on the mean velocity profile within a flat plate boundary layer is of significant interest to the development of DBD-based LFC technology. In this investigation, the velocity distribution within a flat plate boundary layer in a zero pressure gradient is measured in response to the operation of an orthogonally arranged actuator. The results suggest that significant thinning of the boundary layer can be realized with an orthogonally arranged actuator, over a short distance downstream of the device, and used in conjunction with a subtle suction effect, this thinning can be exacerbated. However, further downstream, rapid thickening of the layer, supported by a decrease in the shape factor of the flow suggests that the layer becomes unstable, in an accelerated fashion, to the presence of the actuator. Hence the stability of the layer is found to be significantly altered by the presence of the orthogonally arranged actuator, a requisite for a LFC system. However, since the actuator produces a destabilizing effect, the development of a successful LFC system based on orthogonal actuators will require further work.

Gibson, B. A.; Arjomandi, M.; Kelso, R. M.

2012-01-01

55

High Mach Number Leading-edge Flow Separation Control using AC DBD Plasma Actuators  

NASA Astrophysics Data System (ADS)

Wind tunnel experiments were conducted to quantify the effectiveness of alternating current dielectric barrier discharge flow control actuators to suppress leading-edge stall on a NASA energy efficient transport airfoil at compressible freestream speeds. The objective of this research was to increase lift, reduce drag, and improve the stall characteristics of the supercritical airfoil near stall by flow reattachment at relatively high Mach and Reynolds numbers. In addition, the effect of unsteady (or duty cycle) operation on these aerodynamic quantities was also investigated. The experiments were conducted for a range of Mach numbers between 0.1 and 0.4. corresponding to a Reynolds number range of 560,000 through 2,260,000. Lift, drag, quarter chord moment, and suction side pressures were measured near stall for baseline, steady actuation, and a scan of nondimensional duty cycle frequencies. The results show that the plasma actuators were effective at reattaching the leading-edge separated flow as evidenced by the increase in maximum lift coefficient and stall angle (as much as 2.5 degrees). The experiment also showed that lift was increased the most when the plasma actuator was operated unsteady with a nondimensional frequency of unity.

Kelley, Christopher; Bowles, Patrick; Cooney, John; He, Chuan; Corke, Thomas; Osborne, Bradley; Silkey, Joseph; Zehnle, Joseph

2011-11-01

56

Plasma actuated heat transfer Subrata Roya  

E-print Network

crossflow creating a three-dimensional flow field entraining some hot gas to bend toward the blade the domain of influence as shown in Fig. 2 schematic below. The momentum transfer between the plasma and gas introduce plasmas for film cooling enhancement in gas turbines and other engineering applications. We

Roy, Subrata

57

Nanosecond-pulsed plasma actuation in quiescent air and laminar boundary layer  

NASA Astrophysics Data System (ADS)

An experimental investigation of the working principles of a nanosecond-pulsed dielectric barrier discharge (ns-DBD) plasma actuator has been conducted. Special emphasis is given on the thermal effects accompanying the rapid deposition of energy associated with this kind of actuation. A ns-DBD plasma actuator has been operated in quiescent air conditions as well as in a flat plate laminar boundary layer, with external flow velocity of 5 and 10 m s-1. Schlieren imaging and particle image velocimetry have been used to characterize the actuation. Additionally, the back-current shunt technique has been used for current measurements, from which energy input (per pulse) is calculated. Cases of 10-, 20- and 50-pulse bursts are tested. Schlieren imaging in still air conditions shows the formation of a high-temperature region in the vicinity of the discharge volume. The spatial extent of the visible hot spot depends upon the number of pulses within the burst, following a power law. Schlieren imaging of the span-wise effect of the plasma actuator reveals weak compression waves originating from the loci of discharge filaments. The thermal hot spots exhibit significant three-dimensionality. Particle image velocimetry is used to measure the velocity field resulting from the ns-DBDs acting on a laminar boundary layer. The disturbance leads to formation of a Tollmien-Schlichting wave train, with spectral content in good agreement with linear stability theory. It is observed that the group length of the wave train is proportional to the number of pulses within the burst.

Correale, G.; Michelis, T.; Ragni, D.; Kotsonis, M.; Scarano, F.

2014-03-01

58

Experimental Investigation of Lift Enhancement and Roll Control Using Plasma Actuators  

E-print Network

Experimental Investigation of Lift Enhancement and Roll Control Using Plasma Actuators Alexander N.2514/1.34659 An experimental investigation into the use of trailing-edge-mounted plasma actuators for lift enhancement and roll control is described. Data are presented showing the effect that the actuators have on lift, pitch

Jumper, Eric

59

Experimental Characterization of the Plasma Synthetic Jet Actuator  

NASA Astrophysics Data System (ADS)

The plasma synthetic jet is a novel active flow control method because of advantages such as fast response, high frequency and non-moving parts, and it has received more attention recently, especially regarding its application to high-speed flow control. In this paper, the experimental characterization of the plasma synthetic jet actuator is investigated. The actuator consists of a copper anode, a tungsten cathode and a ceramic shell, and with these three parts a cavity can be formed inside the actuator. A pulsed-DC power supply was adopted to generate the arc plasma between the electrodes, through which the gas inside was heated and expanded from the orifice. Discharge parameters such as voltage and current were recorded, respectively, by voltage and current probes. The schlieren system was used for flow visualization, and jet velocities with different discharge parameters were measured. The schlieren images showed that the strength of plasma jets in a series of pulses varies from each other. Through velocity measurement, it is found that at a fixed frequency, the jet velocity hardly increases when the discharge voltage ranges from 16 kV to 20 kV. However, with the discharge voltage fixed, the jet velocity suddenly decreases when the pulse frequency rises above 500 Hz, whereas at other testing frequencies no such decrease was observed. The maximum jet velocity measured in the experiment was up to 110 m/s, which is believed to be effective for high-speed flow control.

Jin, Di; Li, Yinghong; Jia, Min; Song, Huimin; Cui, Wei; Sun, Quan; Li, Fanyu

2013-10-01

60

Tethered cube stabilization by means of leading-edge DBD plasma actuation  

NASA Astrophysics Data System (ADS)

An experimental investigation was carried out to assess the effectiveness of active flow control as a means for suppressing oscillations of a tethered cube. Two experimental configurations were considered: a static configuration involving surface pressure and particle image velocimetry (PIV) flow field measurements and a dynamic, tethered, configuration. Corner-mounted, dielectric barrier discharge plasma actuators were employed at the leading-edges and were pulsed at reduced frequencies of order one and at varying duty cycles. On the static configuration, actuation changed the direction of the side-forces and virtually eliminated yawing-moment excursions. Surface pressure and flow field measurements showed that control of separation bubbles on the surfaces, as well as control of the separated shear layer, were responsible for these effects. Phase-averaged PIV measurements elucidated the mechanism whereby actuation severs the leading-edge vortex that subsequently sheds downstream. For the tethered cube, actuation dramatically reduced the yawing motions, particularly when the momentum coefficient exceeded 0.3 %. Drag reduction, based on the deflection of the cube, was estimated to be approximately 12 %, consistent with the static data. Reduced frequency and duty cycle had a marked effect on control effectiveness.

Goyta, Snir; Mueller-Vahl, Hanns; Greenblatt, David

2013-01-01

61

Progress Toward Accurate Measurements of Power Consumptions of DBD Plasma Actuators  

NASA Technical Reports Server (NTRS)

The accurate measurement of power consumption by Dielectric Barrier Discharge (DBD) plasma actuators is a challenge due to the characteristics of the actuator current signal. Micro-discharges generate high-amplitude, high-frequency current spike transients superimposed on a low-amplitude, low-frequency current. We have used a high-speed digital oscilloscope to measure the actuator power consumption using the Shunt Resistor method and the Monitor Capacitor method. The measurements were performed simultaneously and compared to each other in a time-accurate manner. It was found that low signal-to-noise ratios of the oscilloscopes used, in combination with the high dynamic range of the current spikes, make the Shunt Resistor method inaccurate. An innovative, nonlinear signal compression circuit was applied to the actuator current signal and yielded excellent agreement between the two methods. The paper describes the issues and challenges associated with performing accurate power measurements. It provides insights into the two methods including new insight into the Lissajous curve of the Monitor Capacitor method. Extension to a broad range of parameters and further development of the compression hardware will be performed in future work.

Ashpis, David E.; Laun, Matthew C.; Griebeler, Elmer L.

2012-01-01

62

Low pressure characterization of dielectric barrier discharge actuators Jignesh Soni and Subrata Roya)  

E-print Network

kPa ambient air pressure show that as the pressure decreases, the thrust increases to a maximum pressures. An increase in ambient air temperature from 30 to 200 C at atmospheric pressure resultedLow pressure characterization of dielectric barrier discharge actuators Jignesh Soni and Subrata

Roy, Subrata

63

Plasma Actuators for Turbomachinery Flow Control  

NASA Technical Reports Server (NTRS)

This report is Part I of the final report of NASA Cooperative Agreement contract no. NNX07AC02A. The period of performance was January 1, 2007 to December 31, 2010. This report includes the project summary, a list of publications and reprints of the publications that appeared in archival journals. Part II of the final report includes a Ph.D. dissertation and is published separately as NASA/CR-2012-2172655. The research performed under this project was focused on the operation of surface dielectric barrier discharge (DBD) devices driven by high voltage, nanosecond scale pulses plus constant or time varying bias voltages. The main interest was in momentum production and the range of voltages applied eliminated significant heating effects. The approach was experimental supplemented by computational modeling. All the experiments were conducted at Princeton University. The project provided comprehensive understanding of the associated physical phenomena. Limitations on the performance of the devices for the generation of high velocity surface jets were established and various means for overcoming those limitations were proposed and tested. The major limitations included the maximum velocity limit of the jet due to electrical breakdown in air and across the dielectric, the occurrence of backward breakdown during the short pulse causing reverse thrust, the buildup of surface charge in the dielectric offsetting the forward driving potential of the bias voltage, and the interaction of the surface jet with the surface through viscous losses. It was also noted that the best performance occurred when the nanosecond pulse and the bias voltage were of opposite sign. Solutions include the development of partially conducting surface coatings, the development of a semiconductor diode inlaid surface material to suppress the backward breakdown. Extension to long discharge channels was studied and a new ozone imaging method developed for more quantitative determination of surface jet properties.

Miles, Richard, B; Shneider, Mikhail, N.

2012-01-01

64

Unmanned air vehicle flow separation control using dielectric barrier discharge plasma at high wind speed  

NASA Astrophysics Data System (ADS)

The present paper described an experimental investigation of separation control of an Unmanned Aerial Vehicle (UAV) at high wind speeds. The plasma actuator was based on Dielectric Barrier Discharge (DBD) and operated in a steady manner. The flow over a wing of UAV was performed with smoke flow visualization in the ?0.75 m low speed wind tunnel to reveal the flow structure over the wing so that the locations of plasma actuators could be optimized. A full model of the UAV was experimentally investigated in the ?3.2 m low speed wind tunnel using a six-component internal strain gauge balance. The effects of the key parameters, including the locations of the plasma actuators, the applied voltage amplitude and the operating frequency, were obtained. The whole test model was made of aluminium and acted as a cathode of the actuator. The results showed that the plasma acting on the surface of UAV could obviously suppress the boundary layer separation and reduce the model vibration at the high wind speeds. It was found that the maximum lift coefficient of the UAV was increased by 2.5% and the lift/drag ratio was increased by about 80% at the wind speed of 100 m/s. The control mechanism of the plasma actuator at the test configuration was also analyzed.

Zhang, Xin; Huang, Yong; Wang, WanBo; Wang, XunNian; Li, HuaXing

2014-06-01

65

Plasma morphology and induced airflow characterization of a DBD actuator with serrated electrode  

NASA Astrophysics Data System (ADS)

Plasma morphology and airflow induced by a dielectric barrier discharge (DBD) actuator, whose exposed electrode geometry is designed with a serrated configuration, are investigated in quiescent air and compared with a DBD actuator consisting of electrodes designed with a standard linear strip configuration. ICCD imaging, electrical measurements and three-component laser Doppler velocimetry were carried out to compare various features of these two actuators. With the serrated configuration, ICCD images of the discharge show that streamers are bent, whereas with the linear configuration they are straight. These curved streamers induce a three-dimensional flow topology, which is confirmed by friction line visualization and velocity measurements. Whereas a two-dimensional wall-jet is induced with the linear configuration, a transverse velocity component is measured with the serrated configuration, implying the creation of spanwise-periodic vorticity. Phase-averaged velocity measurements allow the temporal variation of this transverse velocity to be highlighted. On both sides of a tooth, it has qualitatively the same variation as the longitudinal velocity with respect to the negative or positive half-cycles of the high voltage signal. Moreover, with the same electrical operating parameters, the measured longitudinal velocity was higher, particularly at the tips.

Joussot, R.; Leroy, A.; Weber, R.; Rabat, H.; Loyer, S.; Hong, D.

2013-03-01

66

PIV measurements of flow characteristics induced by mini plate-wing plasma actuators  

NASA Astrophysics Data System (ADS)

The surface DBD plasma actuator is known to be effective for flow control process. Plasma is produced on actuator and gives a body force to the ambient air which is the mechanism for active flow control. Until now, the actuators have been mounted on the wall surface. The plasma actuator is thin and controllable electrically. If we combine the plasma actuator and the passive devices like a vortex generator and Large Eddy Break Up device, those passive devices would be activated. As the basis of the combination use, this paper investigated the wing-like plasma actuators, the width and chord length of which were 96mm and 19.6mm respectively. The electric wind was generated in the absence of external flow by the plasma actuator. Two electrodes were separated by a Kapton thin wing plate and were located at 5.75mm or 14mm from the leading edge. The induced flow was compared as a function of the distance from the leading edge to the actuator position. It was found that the increase in the distance shifted the point of maximum velocity downstream but the induce wake flow indicated the same momentum integral.

Mominul Islam Mukut, A. N. M.; Mizunuma, Hiroshi; Segawa, Takehiko; Hiromichi, Obara

2010-11-01

67

Airfoil Roll Control by Bang-Bang Optimal Control Method with Plasma Actuators  

E-print Network

The bang-bang optimal control method was proposed for glow discharge plasma actuators, taking account of practical issues, such as limited actuation states with instantaneously varied aerodynamic control performance. Hence, the main contribution of this Note is to integrate flight control with active flow control in particular for plasma actuators. Flow control effects were examined in wind tunnel experiments, which show that the plasma authority for flow control is limited. Flow control effects are only obvious at pitch angles near stall. However, flight control simulations suggest that even those small plasma-induced roll moments can satisfactorily fulfill the maneuver tasks and meet flight quality specifications. In addition, the disturbance from volatile plasma-induced roll moments can be rejected. Hence, the proposed bang-bang control method is a promising candidate of control design methodology for plasma actuators.

Wei, Qingkai; Chen, Bao; Huang, Xun

2012-01-01

68

Vacuum application of thermal barrier plasma coatings  

NASA Technical Reports Server (NTRS)

Coatings are presently applied to Space Shuttle Main Engine (SSME) turbine blades for protection against the harsh environment realized in the engine during lift off-to-orbit. High performance nickel, chromium, aluminum, and yttrium (NiCrAlY) alloy coatings, which are applied by atmospheric plasma spraying, crack and spall off because of the severe thermal shock experienced during start-up and shut-down of the engine. Ceramic coatings of yttria stabilized zirconia (ZrO2-Y2O3) were applied initially as a thermal barrier over coating to the NiCrAlY but were removed because of even greater spalling. Utilizing a vacuum plasma spraying process, bond coatings of NiCrAlY were applied in a low pressure atmosphere of argon/helium, producing significantly improved coating-to-blade bonding. The improved coatings showed no spalling after 40 MSFC burner rig thermal shock cycles, cycling between 1700 and -423 F. The current atmospheric plasma NiCrAlY coatings spalled during 25 test cycles. Subsequently, a process was developed for applying a durable thermal barrier coating of ZrO2-Y2O3 to the turbine blades of first stage high-pressure fuel turbopumps utilizing the vacuum plasma process. The improved thermal barrier coating has successfully passed 40 burner rig thermal shock cycles without spalling. Hot firing in an SSME turbine engine is scheduled for the blades. Tooling was installed in preparation for vacuum plasma spray coating other SSME hardware, e.g., the titanium main fuel valve housing (MFVH) and the fuel turbopump nozzle/stator.

Holmes, R. R.; Mckechnie, T. N.

1988-01-01

69

Active Control of Flow around NACA 0015 Airfoil by Using DBD Plasma Actuator  

NASA Astrophysics Data System (ADS)

In this study, effect of plasma actuator on a flat plate and manipulation of flow separation on NACA0015 airfoil with plasma actuator at low Reynolds numbers were experimentally investigated. In the first section of the study, plasma actuator which consists of positive and grounded electrode couple and dielectric layer, located on a flat plate was actuated at different frequencies and peak to peak voltages in range of 3-5 kHz and 6-12 kV respectively. Theinduced air flow velocity on the surface of flat plate was measured by pitot tube at different locations behind the actuator. The influence of dielectricthickness and unsteady actuation with duty cycle was also examined. In the second section, the effect of plasma actuator on NACA0015 airfoil was studied atReynolds number 15000 and 30000. Four plasma actuators were placed at x/C = 0.1, 0.3, 0.5 and 0.9, and different electrode combinations were activated by sinusoidal signal. Flow visualizations were done when the attack angles were 0, 5, 10, 15 and 20. The results indicate that up to the 15 attack angle, the separated flow was reattached by plasma actuator at 12kV peak to peak voltage and 4 kHz frequency. However, 12 kVpp voltage was insufficient to reattach the flow at 20 angle of attack. The separated flow could be reattached by increasing the voltage up to 13 kV. Lift coefficient was also increased by the manipulated flow over the airfoil. Results showed that even high attack angles, the actuators can control the flow separation and prevent the airfoil from stall at low Reynolds numbers.

Akansu, Y. E.; Karakaya, F.; ?anl?soy, A.

2013-04-01

70

Streamwise and spanwise plasma actuators for flow-induced cavity noise control  

E-print Network

in the atmosphere pressure air helps to yield an increase in flow control performance. Al- though the precise flowStreamwise and spanwise plasma actuators for flow-induced cavity noise control Xun Huang and Xin streamwise and spanwise actuators to control flow-induced noise from a cavity. It was found

Huang, Xun

71

Flow-control-induced vibrations for power generation using pulsed plasma actuators  

NASA Astrophysics Data System (ADS)

This paper describes flow-control-induced vibrations using pulsed dielectric barrier discharge plasma actuators, in which boundary layer separation on a structure is actively controlled to produce periodic loads that lead to its vibration. The concept is intended for energy generation and is demonstrated experimentally using a one-degree-of-freedom pivoted cylindrical body mounted vertically within a blow-down wind tunnel. Subcritical Reynolds numbers, less than 105, were considered where typical shedding frequencies were several times larger than the system natural frequency. Static deflection experiments were performed to determine the maximum imposed aerodynamic loads as a function of control parameters and these were complemented with flow-field measurements. Periodic loading of the cylinder was achieved by periodic modulation of the actuator. Large amplitude oscillations were observed when the modulation frequency was close to the system natural frequency. In contrast to natural vortex induced vibration, the large amplitude oscillations were achieved by alternating dynamic separation and attachment of the boundary layer. Estimation of the transient loads was performed using a system identification technique and the power generated by the system was estimated on the basis of a piecewise linear model. Peak estimated power coefficients were relatively small (0.042) but can be improved by increasing the lateral force coefficients and by proportionately increasing the system's physical size.

Greenblatt, David; Treizer, Alexander; Eidelman, Alexander; Mueller-Vahl, Hanns

2012-10-01

72

DBD Plasma Actuators for Flow Control in Air Vehicles and Jet Engines - Simulation of Flight Conditions in Test Chambers by Density Matching  

NASA Technical Reports Server (NTRS)

Dielectric Barrier Discharge (DBD) Plasma actuators for active flow control in aircraft and jet engines need to be tested in the laboratory to characterize their performance at flight operating conditions. DBD plasma actuators generate a wall-jet electronically by creating weakly ionized plasma, therefore their performance is affected by gas discharge properties, which, in turn, depend on the pressure and temperature at the actuator placement location. Characterization of actuators is initially performed in a laboratory chamber without external flow. The pressure and temperature at the actuator flight operation conditions need to be simultaneously set in the chamber. A simplified approach is desired. It is assumed that the plasma discharge depends only on the gas density, while other temperature effects are assumed to be negligible. Therefore, tests can be performed at room temperature with chamber pressure set to yield the same density as in operating flight conditions. The needed chamber pressures are shown for altitude flight of an air vehicle and for jet engines at sea-level takeoff and altitude cruise conditions. Atmospheric flight conditions are calculated from standard atmosphere with and without shock waves. The engine data was obtained from four generic engine models; 300-, 150-, and 50-passenger (PAX) aircraft engines, and a military jet-fighter engine. The static and total pressure, temperature, and density distributions along the engine were calculated for sea-level takeoff and for altitude cruise conditions. The corresponding chamber pressures needed to test the actuators were calculated. The results show that, to simulate engine component flows at in-flight conditions, plasma actuator should be tested over a wide range of pressures. For the four model engines the range is from 12.4 to 0.03 atm, depending on the placement of the actuator in the engine. For example, if a DBD plasma actuator is to be placed at the compressor exit of a 300 PAX engine, it has to be tested at 12.4 atm for takeoff, and 6 atm for cruise conditions. If it is to be placed at the low-pressure turbine, it has to be tested at 0.5 and 0.2 atm, respectively. These results have implications for the feasibility and design of DBD plasma actuators for jet engine flow control applications. In addition, the distributions of unit Reynolds number, Mach number, and velocity along the engine are provided. The engine models are non-proprietary and this information can be used for evaluation of other types of actuators and for other purposes.

Ashpis, David E.; Thurman, Douglas R.

2011-01-01

73

Adaptive flow control of low-Reynolds number aerodynamics using dielectric barrier discharge actuator  

NASA Astrophysics Data System (ADS)

Aerodynamic performance of low-Reynolds number flyers, for a chord-based Reynolds number of 10 5 or below, is sensitive to wind gusts and flow separation. Active flow control offers insight into fluid physics as well as possible improvements in vehicle performance. While facilitating flow control by introducing feedback control and fluidic devices, major challenges of achieving a target aerodynamic performance under unsteady flow conditions lie on the high-dimensional nonlinear dynamics of the flow system. Therefore, a successful flow control framework requires a viable as well as accessible control scheme and understanding of underlying flow dynamics as key information of the flow system. On the other hand, promising devices have been developed recently to facilitate flow control in this flow regime. The dielectric barrier discharge (DBD) actuator is such an example; it does not have moving parts and provides fast impact on the flow field locally. In this paper, recent feedback flow control studies, especially those focusing on unsteady low-Reynolds number aerodynamics, are reviewed. As an example of an effective flow control framework, it is demonstrated that aerodynamic lift of a high angle-of-attack wing under fluctuating free-stream conditions can be stabilized using the DBD actuator and an adaptive algorithm based on general input-output models. System nonlinearities and control challenges are discussed by assessing control performance and the variation of the system parameters under various flow and actuation conditions. Other fundamental issues from the flow dynamics view point, such as the lift stabilization mechanism and the influence on drag fluctuation are also explored. Both potentiality and limitation of the linear modeling approach are discussed. In addition, guidelines on system identification and the controller and actuator setups are suggested.

Cho, Young-Chang; Shyy, Wei

2011-10-01

74

Control of the corner separation in a compressor cascade by steady and unsteady plasma aerodynamic actuation  

NASA Astrophysics Data System (ADS)

This paper reports experimental results on using steady and unsteady plasma aerodynamic actuation to control the corner separation, which forms over the suction surface and end wall corner of a compressor cascade blade passage. Total pressure recovery coefficient distribution was adopted to evaluate the corner separation. Corner separation causes significant total pressure loss even when the angle of attack is 0. Both steady and unsteady plasma aerodynamic actuations suppress the corner separation effectively. The control effect obtained by the electrode pair at 25% chord length is as effective as that obtained by all four electrode pairs. Increasing the applied voltage improves the control effect while it augments the power requirement. Increasing the Reynolds number or the angle of attack makes the corner separation more difficult to control. The unsteady actuation is much more effective and requires less power due to the coupling between the unsteady actuation and the separated flow. Duty cycle and excitation frequency are key parameters in unsteady plasma flow control. There are thresholds in both the duty cycle and the excitation frequency, above which the control effect saturates. The maximum relative reduction in total pressure loss coefficient achieved is up to 28% at 70% blade span. The obvious difference between steady and unsteady actuation may be that wall jet governs the flow control effect of steady actuation, while much more vortex induced by unsteady actuation is the reason for better control effect.

Li, Ying-Hong; Wu, Yun; Zhou, Min; Su, Chang-Bing; Zhang, Xiong-Wei; Zhu, Jun-Qiang

2010-06-01

75

Flow Control over a Conical Forebody by Periodic Pulsed Plasma Actuation  

NASA Astrophysics Data System (ADS)

The flow control mechanism of plasma actuators with periodic pulsed discharge to control the bi-stable vortices over a cone-cylinder is investigated. The actuators are installed on the leeward surface near the apex of a cone which has a semi-apex angle of 10. The effectiveness of the plasma actuation under different free-stream velocities and angles of attack is analyzed. The pressure distributions over the conical forebody are measured by both steady and dynamic pressure transducers. The transient dynamic pressure distribution tends to gradually become steady as the free-stream velocity increases, that is, the pulsed actuation approximates a continuous one. Furthermore, the flow control effectiveness becomes less noticeable as the free-stream velocity or the angle of attack increases under certain controlling electrical parameters.

Zheng, Borui; Gao, Chao; Li, Yibin; Liu, Feng; Luo, Shijun

2013-04-01

76

Characterization of a Direct-Current Glow Discharge Plasma Actuator in Low-Pressure Supersonic Flow  

E-print Network

densities (1 A=m2 ) [9­11]. DBD discharges generate low (room) temperature plasmas and rely on the EHD on the generation of a Lorentz force on the bulk flow owing to the interaction of electrical currentsCharacterization of a Direct-Current Glow Discharge Plasma Actuator in Low-Pressure Supersonic Flow

Raja, Laxminarayan L.

77

Study of a pseudo-empirical model approach to characterize plasma actuators  

NASA Astrophysics Data System (ADS)

The use of plasma actuators is a recent technology that imposes a localized electric force that is used to control air flows. A suitable representation of actuation enables to undertake plasma actuators optimization, to design flow-control strategies, or to analyse the flow stabilization that can be attained by plasma forcing. The problem description may be clearly separated in two regions. An outer region, where the fluid is electrically neutral, in which the flow is described by the Navier-Stokes equation without any forcing term. An inner region, that forms a thin boundary layer, where the fluid is ionized and electric forces are predominant. The outer limit of the inner solution becomes the boundary condition for the outer problem. The outer problem can then be solved with a slip velocity that is issued from the inner solution. Although the solution for the inner problem is quite complex it can be contoured proposing pseudo-empirical models where the slip velocity of the outer problem is determined indirectly from experiments. This pseudo-empirical model approach has been recently tested in different cylinder flows and revealed quite adapted to describe actuated flow behaviour. In this work we determine experimentally the influence of the duty cycle on the slip velocity distribution. The velocity was measured by means of a pitot tube and flow visualizations of the starting vortex (i.e. the induced flow when actuation is activated in a quiescent air) have been done by means of the Schlieren technique. We also performed numerical experiments to simulate the outer region problem when actuation is activated in a quiescent air using a slip velocity distribution as a boundary condition. The experimental and numerical results are in good agreement showing the potential of this pseudo-empirical model approach to characterize the plasma actuation.

Marziali Bermudez, M.; Sosa, R.; Grondona, D.; Mrquez, A.; Kelly, H.; Artana, G.

2011-05-01

78

Simulations of Serpentine Plasma Actuators in a Laminar Boundary Layer  

E-print Network

as components of active and passive flow control systems. One concern with in applying these actuators of 11 American Institute of Aeronautics and Astronautics #12; Velocity ratio I Integrated value. Introduction Boundary layer control is one aspect of fluid dynamics that is becoming increasingly more

Roy, Subrata

79

Propagating-arc magnetohydrodynamic plasma actuator for directional high-authority flow control in atmospheric air  

NASA Astrophysics Data System (ADS)

A propagating-arc magnetohydrodynamic plasma actuator for aerodynamic flow control is reported. The actuator comprises two rail electrodes flush mounted on an aerodynamic surface. A pulsed arc is propelled down the length of the rails by Lorentz forces supported by a self-induced magnetic field. The arc induces a high velocity pulsed air wall jet due to the pushing and entrainment actions. Experiments in quiescent air demonstrate that the plasma arc achieves a peak velocity of around 100 m s-1 and requires a discharge energy on the order of 300 J per pulse. Wind tunnel tests on a 14.5 inch chord airfoil section, at a Reynolds number of 0.45 million show induced flow velocities on the order of 10's m s-1 with significant penetration of the flow actuation effect perpendicular to the wall surface.

Pafford, Brent; Sirohi, Jayant; Raja, Laxminarayan L.

2013-12-01

80

Flow and Noise Control in High Speed and High Reynolds Number Jets Using Plasma Actuators  

NASA Technical Reports Server (NTRS)

The idea of manipulating flow to change its characteristics is over a century old. Manipulating instabilities of a jet to increase its mixing and to reduce its radiated noise started in the 1970s. While the effort has been successful in low-speed and low Reynolds number jets, available actuators capabilities in terms of their amplitude, bandwidth, and phasing have fallen short in control of high-speed and high Reynolds number jets of practical interest. Localized arc filament plasma actuators have recently been developed and extensively used at Gas Dynamics and Turbulence Laboratory (GDTL) for control of highspeed and high Reynolds number jets. While the technique has been quite successful and is very promising, all the work up to this point had been carried out using small high subsonic and low supersonic jets from a 2.54 cm diameter nozzle exit with a Reynolds number of about a million. The preliminary work reported in this paper is a first attempt to evaluate the scalability of the technique. The power supply/plasma generator was designed and built in-house at GDTL to operate 8 actuators simultaneously over a large frequency range (0 to 200 kHz) with independent control over phase and duty cycle of each actuator. This allowed forcing the small jet at GDTL with azimuthal modes m = 0, 1, 2, 3, plus or minus 1, plus or minus 2, and plus or minus 4 over a large range of frequencies. This power supply was taken to and used, with minor modifications, at the NASA Nozzle Acoustic Test Rig (NATR). At NATR, 32 actuators were distributed around the 7.5 in. nozzle (a linear increase with nozzle exit diameter would require 60 actuators). With this arrangement only 8 actuators could operate simultaneously, thus limiting the forcing of the jet at NATR to only three azimuthal modes m = plus or minus 1, 4, and 8. Very preliminary results at NATR indicate that the trends observed in the larger NASA facility in terms of the effects of actuation frequency and azimuthal modes are similar in both small GDTL and larger NASA jets. However, the actuation authority seems to fall short in the larger jet at higher Mach numbers, resulting in decreased amplitude response compared to the small jet, which is attributed at this point to the lack of sufficient number of actuators. The preliminary results seem also to suggest that amplitude of actuation tones is similar in both the small and larger jets.

Samimy, M.; Kastner, J.; Kim, J.-H.; Utkin, Y.; Adamovich, I.; Brown, C. A.

2006-01-01

81

Aerodynamic plasma actuators: A directional micro-jet device  

Microsoft Academic Search

In recent years electroaerodynamic actuators have been rather intensively studied in order to control airflow [H. Velkoff, R. Godfrey, J. of Heat Transfer 101 (1979) 157; S. El-Khabiry, G.M. Colver, Phys. Fluids 9 3 (1997) 587; A. Soldati, S. Banerjee, Phys. Fluids 10 (1998) 1742; R. Vilela Mendes, J.A. Dente, J. Fluids Eng. 120 (1998) 626; A. Schtze, et al.,

Nicolas Bnard; Jrme Jolibois; Eric Moreau; Roberto Sosa; Guillermo Artana; Grard Touchard

2008-01-01

82

RESEARCH ARTICLE The use of plasma actuators for bluff body broadband  

E-print Network

the attention of communities that live near airports to the problem of noise pollution (Raman and Mc (Crighton 1991; Macaraeg 1998). Since airframe noise is normally caused by the interactions betweenRESEARCH ARTICLE The use of plasma actuators for bluff body broadband noise control Yong Li · Xin

Huang, Xun

83

Modeling plasma actuators with air chemistry for effective flow control Kunwar Pal Singh and Subrata Roya  

E-print Network

Modeling plasma actuators with air chemistry for effective flow control Kunwar Pal Singh modifications of air flowing around flat plates and air craft wings have been documented both experi- mentally several benefits in active flow control appli- cations, including absence of moving parts, rapid on-off de

Roy, Subrata

84

American Institute of Aeronautics and Astronautics Induced Flow from Serpentine Plasma Actuators Acting in  

E-print Network

American Institute of Aeronautics and Astronautics 1 Induced Flow from Serpentine Plasma Actuators-957 Copyright © 2011 by the Authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. #12;American Institute of Aeronautics and Astronautics 2 Figure 1. Generic (standard) linear

Roy, Subrata

85

Performance enhancement of IPMC actuator by plasma surface treatment  

Microsoft Academic Search

IPMC (ionic polymer metal composite) is composed of ionic polymer and metal electrodes on both surfaces of the polymer. In this study, we changed the surface morphology of the ionic polymer by using plasma treatment. Plasma treatment made needle-shaped microstructures on the surface of the polymer and the microstructures helped to form a thicker uniform metal electrode which is deposited

Seong Jun Kim; In Taek Lee; Yong Hyup Kim

2007-01-01

86

American Institute of Aeronautics and Astronautics Geometry Effects of Dielectric Barrier Discharge on a Flat Surface  

E-print Network

flow code. We numerically test these actuators in quiescent air. Numerical results show plasma force. Introduction he plasma actuator is becoming a popular device for active flow control. The advantages and numerical data show that dielectric barrier discharge (DBD) actuators are useful in controlling the flow

Roy, Subrata

87

1316 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 36, NO. 4, AUGUST 2008 Schlieren Imaging of Flow Actuation Produced  

E-print Network

comprises the supersonic free stream flowing parallel to a flat plate and abruptly turned by a 30 wedge Actuation Produced by Direct-Current Surface Glow Discharge in Supersonic Flows Jichul Shin, Noel T. Clemens. Index Terms--DC sheath, dc surface discharge, electrostatic force, plasma actuation, supersonic flow

Raja, Laxminarayan L.

88

Control of oblique shock wave/boundary layer interactions using plasma actuators  

NASA Astrophysics Data System (ADS)

Localized arc filament plasma actuators (LAFPAs) are used for shock wave/boundary layer interaction induced separation control in a Mach 2.3 flow. The boundary layer is fully turbulent with a Reynolds number based on the incompressible momentum thickness of 22,000 and shape factor of 1.37, and the impinging shock wave is generated by a 10 compression ramp. The LAFPAs are observed to have significant control authority over the interaction. The main effect is the displacement of the reflected shock and most of the interaction region upstream by approximately one boundary layer thickness (~5 mm). The initial goal of the control was to manipulate the low-frequency ( St~0.03) unsteadiness associated with the interaction region. A detailed investigation of the effect of actuator placement, frequency, and duty cycle on the control authority indicates the actuators' primary control mechanism is not the manipulation of low-frequency unsteadiness. Detailed measurements and analysis indicate that a modification to the boundary layer through heat addition by the actuators is the control mechanism, despite the extremely small power input of the actuators.

Webb, N.; Clifford, C.; Samimy, M.

2013-06-01

89

Simulation of stresses and delamination in a plasma-sprayed thermal barrier system upon thermal cycling  

E-print Network

Simulation of stresses and delamination in a plasma-sprayed thermal barrier system upon thermal barrier system with plasma-sprayed thermal barrier coating (TBC) has been analyzed subject to thermal Thermal barrier systems made using plasma spray coatings are widely used in power turbines as well

Hutchinson, John W.

90

Large tunnel magnetoresistance with plasma oxidized MgO barrier  

Microsoft Academic Search

This work focuses on magnetic tunnel junctions with a polycrystalline MgO barrier, prepared by plasma oxidation. Combined with Co50Fe50 ferromagnetic electrodes, a large tunnel magnetoresistance (TMR) of 60% is obtained at room temperature. The TMR effect is comparable to state-of-the-art Al oxide barriers with amorphous CoFeB electrodes. It is also found to decrease with the MgO thickness. Two most significant

T. Dimopoulos; G. Gieres; J. Wecker; N. Wiese; Y. Luo; K. Samwer

2005-01-01

91

Alternative plasma-oxidized barriers for spin-polarized tunneling  

Microsoft Academic Search

We have obtained high-quality tunnel junctions with MgO barriers and superconducting Al bottom electrodes by sputter deposition and plasma oxidation. These junctions were used for spin-polarized tunneling measurements in which the Zeeman-split superconducting density of states is used to determine directly the tunneling spin polarization with Co and Fe top electrodes. Similar attempts with Ta2O5 barriers resulted in poor quality

C. H. Kant; J. T. Kohlhepp; K. Knechten; H. J. M. Swagten; W. J. M. de Jonge

2004-01-01

92

Micro Actuators Electrostatic actuator  

E-print Network

·Piezoelectric actuator ·Shape memory alloy actuator ·Pneumatic actuator #12;Pneumatic Actuators Applications. #12;Pneumatic Microvalve ·External pneumatic power is required to actuate a actuator. ·Sustain high

Leu, Tzong-Shyng "Jeremy"

93

Stall control at high angle of attack with plasma sheet actuators  

Microsoft Academic Search

We analyzed the modifications of the airflow around an NACA 0015 airfoil when the flow was perturbed with electrohydrodynamic\\u000a forces. The actuation was produced with a plasma sheet device (PSD) consisting in two bare electrodes flush mounted on the\\u000a surface of the wing profile operated to obtain a discharge contouring the body in the inter-electrode space. We analyze the\\u000a influence

Roberto Sosa; Guillermo Artana; Eric Moreau; Grard Touchard

2007-01-01

94

One-dimensional analytical model development of a plasma-based actuator  

NASA Astrophysics Data System (ADS)

This dissertation provides a method for modeling the complex, multi-physics, multi-dimensional processes associated with a plasma-based flow control actuator, also known as the SparkJet, by using a one-dimensional analytical model derived from the Euler and thermodynamic equations, under varying assumptions. This model is compared to CFD simulations and experimental data to verify and/or modify the model where simplifying assumptions poorly represent the real actuator. The model was exercised to explore high-frequency actuation and methods of improving actuator performance. Using peak jet momentum as a performance metric, the model shows that a typical SparkJet design (1 mm orifice diameter, 84.8 mm3 cavity volume, and 0.5 J energy input) operated over a range of frequencies from 1 Hz to 10 kHz shows a decrease in peak momentum corresponding to an actuation cutoff frequency of 800 Hz. The model results show that the cutoff frequency is primarily a function of orifice diameter and cavity volume. To further verify model accuracy, experimental testing was performed involving time-dependent, cavity pressure and arc power measurements as a function of orifice diameter, cavity volume, input energy, and electrode gap. The cavity pressure measurements showed that pressure-based efficiency ranges from 20% to 40%. The arc power measurements exposed the deficiency in assuming instantaneous energy deposition and a calorically perfect gas and also showed that arc efficiency was approximately 80%. Additional comparisons between the pressure-based modeling and experimental results show that the model captures the actuator dependence on orifice diameter, cavity volume, and input energy but over-estimates the duration of the jet flow during Stage 2. The likely cause of the disagreement is an inaccurate representation of thermal heat transfer related to convective heat transfer or heat loss to the electrodes.

Popkin, Sarah Haack

95

Active control of massively separated high-speed/base flows with electric arc plasma actuators  

NASA Astrophysics Data System (ADS)

The current project was undertaken to evaluate the effects of electric arc plasma actuators on high-speed separated flows. Two underlying goals motivated these experiments. The first goal was to provide a flow control technique that will result in enhanced flight performance for supersonic vehicles by altering the near-wake characteristics. The second goal was to gain a broader and more sophisticated understanding of these complex, supersonic, massively-separated, compressible, and turbulent flow fields. The attainment of the proposed objectives was facilitated through energy deposition from multiple electric-arc plasma discharges near the base corner separation point. The control authority of electric arc plasma actuators on a supersonic axisymmetric base flow was evaluated for several actuator geometries, frequencies, forcing modes, duty cycles/on-times, and currents. Initially, an electric arc plasma actuator power supply and control system were constructed to generate the arcs. Experiments were performed to evaluate the operational characteristics, electromagnetic emission, and fluidic effect of the actuators in quiescent ambient air. The maximum velocity induced by the arc when formed in a 5 mm x 1.6 mm x 2 mm deep cavity was about 40 m/s. During breakdown, the electromagnetic emission exhibited a rise and fall in intensity over a period of about 340 ns. After breakdown, the emission stabilized to a near-constant distribution. It was also observed that the plasma formed into two different modes: "high-voltage" and "low-voltage". It is believed that the plasma may be switching between an arc discharge and a glow discharge for these different modes. The two types of plasma do not appear to cause substantial differences on the induced fluidic effects of the actuator. In general, the characterization study provided a greater fundamental understanding of the operation of the actuators, as well as data for computational model comparison. Preliminary investigations of actuator geometry in the supersonic base flow determined that inclined cavity and normal cavity actuators positioned on the base near the base edge could produce significant disturbances in the shear layer. The disturbances were able to be tracked in time with phase-locked schlieren imaging and particle image velocimetry (PIV). The final set of flow control experiments were therefore performed with an eight-actuator base using the inclined cavity actuator geometry. The actuators were able to cause moderate influences on the axisymmetric shear layer velocity profile and base pressure. The most substantial changes to the shear layer and base pressure were noted for the highest current and duty cycle tests. At 1 A and 20% duty cycle, the base pressure was reduced by 3.5%. Similar changes were noted for all modes and a range of frequencies from about 10-30 kHz. Increases in duty cycle between 4% and 20% caused a nearly linear decrease in base pressure. Analysis of the shear layer velocity profiles acquired through PIV show a local thickening of the shear layer in the region of the disturbances caused by the actuator. A slight increase in thickness was also observed away from the disturbance. Disturbances were able to be tracked at all frequencies and translated along the shear layer at a convective velocity of 430 +/- 20 m/s. A fairly clear trend of increasing velocity disturbance amplitude correlating to increasing base pressure changes was noted. Moreover, the ability of the disturbances to stay well organized further down the shear layer also appears to be a significant factor in the actuators' effect on base pressure. Consistent with these observations, it appears that increased duty cycle causes increased shear layer disturbance amplitudes. The use of PIV has enabled substantial insight to be gained into the effects of the actuators on the ensemble-averaged flow field and on the variability of the instantaneous flow field with and without control. A sensitive bimodal recirculation region behavior was found in the no-control flow field tha

DeBlauw, Bradley G.

96

Airflow control by non-thermal plasma actuators  

Microsoft Academic Search

Active flow control is a topic in full expansion due to associated industrial applications of huge importance, particularly for aeronautics. Among all flow control methods, such as the use of mechanical flaps, wall synthetic jets or MEMS, plasma-based devices are very promising. The main advantages of such systems are their robustness, simplicity, low power consumption and ability for real-time control

Eric Moreau

2007-01-01

97

Shockwaveboundary layer interaction control by plasma aerodynamic actuation: An experimental investigation  

NASA Astrophysics Data System (ADS)

The potential of controlling shockwaveboundary layer interactions (SWBLIs) in air by plasma aerodynamic actuation is demonstrated. Experiments are conducted in a Mach 3 in-draft air tunnel. The separation-inducing shock is generated with a diamond-shaped shockwave generator located on the wall opposite to the surface electrodes, and the flow properties are studied with schlieren imaging and static wall pressure probes. The measurements show that the separation phenomenon is weakened with the plasma aerodynamic actuation, which is observed to have significant control authority over the interaction. The main effect is the displacement of the reflected shock. Perturbations of incident and reflected oblique shocks interacting with the separation bubble in a rectangular cross section supersonic test section are produced by the plasma actuation. This interaction results in a reduction of the separation bubble size, as detected by phase-lock schlieren images. The measured static wall pressure also shows that the separation-inducing shock is restrained. Our results suggest that the boundary layer separation control through heating is the primary control mechanism.

Sun, Quan; Cui, Wei; Li, Ying-Hong; Cheng, Bang-Qin; Jin, Di; Li, Jun

2014-07-01

98

Comparison of plasma treatment and sandblast preprocessing for IPMC actuator  

NASA Astrophysics Data System (ADS)

As a new kind of ionic-driven smart materials, ionic polymer metal composite (IPMC ) is normally fabricated by depositing noble metal (gold, platinum, palladium etc.) on both sides of base membrane (Nafion, Flemion etc.) and shows large bending deflection under low voltage. In the process of fabricating IPMC, surface roughening of base membrane has a significant effect on the performance of IPMC. At present, there are many ways to roughen the base membrane, including physical and chemical ways. In this paper, we analyze the effects of different surface treatment time by plasma etching on surface resistance and mechanical properties of IPMCs fabricated by the treated base membranes. Experimental results show that the base membrane treated by plasma etching displays uniform surface roughness, consequently reducing IPMC's surface resistance effectively and forming more uniform and homogeneous external and penetrative electrodes. However, due to the use of reactive gas, the plasma treatment leads to complex chemical reaction on Nafion surface, changing element composition and material properties and resulting in the performance degradation of IPMC. And sandblast way should be adopted and improved without any changes on element and material structure.

Zhang, Chi; Chen, Hualing; Wang, Yanjie; Wang, Yongquan; Jia, Shuhai

2014-03-01

99

Sterilization of Turmeric by Atmospheric Pressure Dielectric Barrier Discharge Plasma  

NASA Astrophysics Data System (ADS)

In this study atmospheric pressure dielectric barrier discharge (DBD) plasma has been employed for sterilizing dry turmeric powders. A 6 kV, 6 kHz frequency generator was used to generate plasma with Ar, Ar/O2, He, and He/O2 gases between the 5 mm gap of two quartz covered electrodes. The complete sterilization time of samples due to plasma treatment was measured. The most important contaminant of turmeric is bacillus subtilis. The results show that the shortest sterilization time of 15 min is achieved by exposing the samples to Ar/O2 plasma. Survival curves of samples are exponential functions of time and the addition of oxygen to plasma leads to a significant increase of the absolute value of time constant of the curves. Magnitudes of protein and DNA in treated samples were increased to a similar value for all samples. Taste, color, and solubility of samples were not changed after the plasma treatment.

Setareh, Salarieh; Davoud, Dorranian

2013-11-01

100

Two-dimensional plasma photonic crystals in dielectric barrier discharge  

SciTech Connect

A series of two-dimensional plasma photonic crystals have been obtained by filaments' self-organization in atmospheric dielectric barrier discharge with two water electrodes, which undergo the transition from square to square superlattice and finally to the hexagon. The spatio-temporal behaviors of the plasma photonic crystals in nanosecond scale have been studied by optical method, which show that the plasma photonic crystal is actually an integration of different transient sublattices. The photonic band diagrams of the transverse electric (TE) mode and transverse magnetic mode for each sublattice of these plasma photonic crystals have been investigated theoretically. A wide complete band gap is formed in the hexagonal plasma photonic crystal with the TE mode. The changes of the band edge frequencies and the band gap widths in the evolvement of different structures are studied. A kind of tunable plasma photonic crystal which can be controlled both in space and time is suggested.

Fan Weili; Dong Lifang [College of Physics Science and Technology, Hebei University, Baoding 071002 (China); Zhang Xinchun [School of Energy and Power Engineering, North China Electric Power University, Baoding 071003 (China)

2010-11-15

101

Failure analysis of plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

Plasma-sprayed thermal barrier coatings have been subjected to thermal cycling tests with simultaneous acoustic emission (AE) monitoring. Process variables and their effect on coating integrity were evaluated in terms of cracking behavior. Failure of the thermal protection is progressive since cracking and crack growth were observed prior to ultimate failure. Catastrophic failure occurs when microcracks are transformed to macrocracks.

C. C. Berndt; R. A. Miller

1984-01-01

102

Pulsed laser processing of plasma sprayed thermal barrier coatings  

Microsoft Academic Search

The requirements for thermal barrier coatings on turbine blades in jet engines and gas turbines are stringent due to the extreme temperatures and constant thermal cycling that demand a material with excellent thermal shock resistant and thermal insulation properties. Plasma sprayed zirconia alloys have been found to fit this role with some degrees of success. However, the presence of surface

K. A. Khor; S. Jana

1997-01-01

103

Hot Isostatic Pressing of Plasma Sprayed Thermal Barrier Coating Systems  

Microsoft Academic Search

Thermal barrier coatings (TBC) are important to aerospace and high performance gas turbine engines because they help to keep the temperature experienced by the base metal low; thus, prolonging the life span of the material. Plasma spraying is a technique commonly used to deposit the ceramic-based TBC. An intermediate layer is applied to enhance the bond between the substrate and

K. A. Khor; N. L. Loh

1995-01-01

104

Feedback control of slowly-varying transient growth by an array of plasma actuators  

NASA Astrophysics Data System (ADS)

Closed-loop feedback control of boundary layer streaks embedded in a laminar boundary layer and experiencing transient growth, which is inherent to bypass boundary layer transition, is experimentally investigated. Streaky disturbances are introduced by a spanwise array of cylindrical roughness elements, and a counter disturbance is provided by a spanwise array of plasma actuators, which are capable of generating spanwise-periodic counter rotating vortices in the boundary layer. Feedback is provided by a spanwise array of shear stress sensors. An input/output model of the system is obtained from measurements of the boundary layer response to steady forcing, and used to design and analyze a proportional-integral controller, which targets a specific spanwise wavenumber of the disturbance. Attention is directed towards a quasi-steady case in which the controller update is slower than the convective time scale. This choice enables addressing issues pertinent to sensing, actuation, and control strategy that are also relevant to the control of unsteady disturbances but without the full complexity of transient effects. The feedback controller and plasma actuators perform well, attenuating the streamwise streaks both in the vicinity of the sensors and farther downstream. The controller remains effective for a range of off-design flow conditions, such as when the free-stream velocity is varied.

Hanson, Ronald E.; Bade, Kyle M.; Belson, Brandt A.; Lavoie, Philippe; Naguib, Ahmed M.; Rowley, Clarence W.

2014-02-01

105

Wide ultrarelativistic plasma beam -- magnetic barrier collision and astrophysical applications  

E-print Network

The interaction between a wide ultrarelativistic fully-ionized plasma beam and a magnetic barrier is studied numerically. It is assumed that the plasma beam is initially homogeneous and impacts with the Lorentz factor $\\Gamma_0\\gg 1$ on the barrier. The magnetic field of the barrier $B_0$ is uniform and transverse to the beam velocity. When the energy densities of the beam and the magnetic field are comparable, $\\alpha = 8\\pi n_0m_pc^2(\\Gamma_0-1)/B^2_0\\sim 1$, the process of the beam -- barrier interaction is strongly nonstationary, and the density of reversed protons is modulated in space by a factor of 10 or so. The modulation of reversed protons decreases with decrease of $\\alpha$. The beam is found to penetrate deep into the barrier provided that $\\alpha > \\alpha_{cr}$, where $\\alpha_{cr}$ is about 0.4. The speed of such a penetration is subrelativistic and depends on $\\alpha$. Strong electric fields are generated near the front of the barrier, and electrons are accelerated in these fields up to the mean energy of protons, i.e. up to $\\sim m_pc^2\\Gamma_0$. The synchrotron radiation of high-energy electrons from the front vicinity is calculated. Stationary solutions for the beam -- barrier collision are considered. It is shown that such a solution may be only at $\\alpha \\lesssim 0.2 - 0.5$ depending on the boundary conditions for the electric field in the region of the beam -- barrier interaction. Some astrophysical applications of these results are briefly discussed.

V. V. Usov; M. V. Smolsky

1997-04-15

106

Control of supersonic axisymmetric base flows using passive splitter plates and pulsed plasma actuators  

NASA Astrophysics Data System (ADS)

An experimental investigation evaluating the effects of flow control on the near-wake downstream of a blunt-based axisymmetric body in supersonic flow has been conducted. To better understand and control the physical phenomena that govern these massively separated high-speed flows, this research examined both passive and active flow-control methodologies designed to alter the stability characteristics and structure of the near-wake. The passive control investigation consisted of inserting splitter plates into the recirculation region. The active control technique utilized energy deposition from multiple electric-arc plasma discharges placed around the base. The flow-control authority of both methodologies was evaluated with experimental diagnostics including particle image velocimetry, schlieren photography, surface flow visualization, pressure-sensitive paint, and discrete surface pressure measurements. Using a blowdown-type wind tunnel reconstructed specifically for these studies, baseline axisymmetric experiments without control were conducted for a nominal approach Mach number of 2.5. In addition to traditional base pressure measurements, mean velocity and turbulence quantities were acquired using two-component, planar particle image velocimetry. As a result, substantial insight was gained regarding the time-averaged and instantaneous near-wake flow fields. This dataset will supplement the previous benchmark point-wise laser Doppler velocimetry data of Herrin and Dutton (1994) for comparison with new computational predictive techniques. Next, experiments were conducted to study the effects of passive triangular splitter plates placed in the recirculation region behind a blunt-based axisymmetric body. By dividing the near-wake into 1/2, 1/3, and 1/4 cylindrical regions, the time-averaged base pressure distribution, time-series pressure fluctuations, and presumably the stability characteristics were altered. While the spatial base pressure distribution was influenced considerably, the area-integrated pressure was only slightly affected. Normalized RMS levels indicate that base pressure fluctuations were significantly reduced with the addition of the splitter plates. Power-spectral-density estimates revealed a spectral broadening of fluctuating energy for the 1/2 cylinder configuration and a bimodal distribution for the 1/3 and 1/4 cylinder configurations. It was concluded that the recirculation region is not the most sensitive location to apply flow control; rather, the shear layer may be a more influential site for implementing flow control methodologies. For active flow control, pulsed plasma-driven fluidic actuators were investigated. Initially, the performance of two plasma actuator designs was characterized to determine their potential as supersonic flow control devices. For the first actuator considered, the pulsed plasma jet, electro-thermal heating from an electric discharge heats and pressurizes gas in a small cavity which is exhausted through a circular orifice forming a synthetic jet. Depending on the electrical energy addition, peak jet velocities ranged between 130 to nearly 500 m/s when exhausted to quiescent, ambient conditions. The second plasma actuator investigated is the localized arc filament plasma actuator (LAFPA), which created fluidic perturbations through the rapid, local thermal heating, generated from an electric arc discharge between two electrodes within a shallow open cavity. Electrical and emission properties of the LAFPA were first documented as a function of pressure in a quiescent, no-flow environment. Rotational and vibrational temperatures from N2 spectra were obtained for select plasma conditions and ambient pressures. Results further validate that the assumption of optically thin conditions for these electric arc plasmas is not necessary valid, even at low ambient pressure. Breakdown voltage, sustained plasma voltage, power, and energy per pulse were demonstrated to decrease with decreasing pressure. Implementing an array of eight electric arcs circumferentially around the base nea

Reedy, Todd Mitchell

107

Large tunnel magnetoresistance with plasma oxidized MgO barrier  

NASA Astrophysics Data System (ADS)

This work focuses on magnetic tunnel junctions with a polycrystalline MgO barrier, prepared by plasma oxidation. Combined with Co50Fe50 ferromagnetic electrodes, a large tunnel magnetoresistance (TMR) of 60% is obtained at room temperature. The TMR effect is comparable to state-of-the-art Al oxide barriers with amorphous CoFeB electrodes. It is also found to decrease with the MgO thickness. Two most significant advantages of the MgO junctions are pointed out: (a) The resistance-area product is approximately two orders of magnitude lower than for AlOX- based junctions of the same thickness. (b) MgO presents unsurpassed thermal stability for high annealing temperatures (up to 370 C) and long annealing periods. In addition, for small, patterned elements, we have tested the switching behavior of the soft electrode grown on the polycrystalline MgO barrier.

Dimopoulos, T.; Gieres, G.; Wecker, J.; Wiese, N.; Luo, Y.; Samwer, K.

2005-10-01

108

Failure modes in plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

Commercial plasma-sprayed thermal barrier coatings (TBCs) were investigated in an effort to elucidate the failure modes during thermal-cycling. Residual stresses in the thermally grown oxide (TGO) was measured using the Cr3+ photoluminescence piezo-spectroscopy (PLPS) method and the microstructures of the TBCs were characterized as a function of thermal cycles. The average residual stress in the TGO was found to be

K. W Schlichting; N. P Padture; E. H Jordan; M Gell

2003-01-01

109

Air plasma sprayed thermal barrier coatings on titanium alloy substrates  

Microsoft Academic Search

Titanium alloys as lightweight structure materials have been shown more interest in the use at moderately elevated temperatures. However, their poor oxidation resistance at temperature above 600C limits a wide application. Consequently, thermal protection becomes a concern. 8wt.% yttria partially stabilized zirconia thermal barrier coatings (TBCs) were air plasma sprayed on titanium alloy substrates (Ti6.6Al3.61Mo1.69Zr0.28Si in wt.%). The microstructures and

Hong Zhou; Fei Li; Bo He; Jun Wang; Bao-de Sun

2007-01-01

110

Plasma spraying of micro-composite thermal barrier coatings  

Microsoft Academic Search

The thermal barrier coatings (TBCs) by gas tunnel-type plasma spraying exhibited ceramic-composite features consisting of a host oxide matrix ceramic with an embedded second phase material. The densities of the composite TBC were found to be higher than those sprayed with 100wt% ZrO2 or Al2O3. In the coatings produced with powder mixtures of 50wt%, the embedded splats are found to

S. Sharafat; A. Kobayashi; Y. Chen; N. M. Ghoniem

2002-01-01

111

Failure modes of plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

Conventional plasma-sprayed thermal barrier coatings (TBCs) are known to fail by spallation of the yttria-stabilized zirconia (YSZ) topcoat exposing the underlying metal to high temperatures. Failure takes place by crack propagation in the YSZ just above the YSZ\\/thermally grown oxide (TGO) interface. Compressive stress in the TGO due to thermal expansion coefficient mismatch and oxidation is believed to play a

Kevin Walter Schlichting

2000-01-01

112

Vacuum 65 (2002) 415425 Plasma spraying of micro-composite thermal barrier coatings  

E-print Network

Vacuum 65 (2002) 415­425 Plasma spraying of micro-composite thermal barrier coatings S. Sharafata. Keywords: Plasma spraying; Gas tunnel-type; Thermal barrier-composite coatings; Aluminum oxide; Zirconium, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan Abstract The thermal barrier coatings

Ghoniem, Nasr M.

113

Low resistance tunnel junctions with remote plasma underoxidized thick barriers  

NASA Astrophysics Data System (ADS)

Low resistance tunnel junctions suitable for >200Gb/inch2 read heads require R A<1??m2 and TMR >10%, usually achieved by natural oxidation with tAl <0.7nm barriers. This paper shows that as-deposited junctions with competitive electrical and magnetic properties can be produced starting from 0.9nm Al barriers and remote plasma oxidation in ion beam-deposited stacks using Co73.8Fe16.2B10 electrodes. TMR 20% for R A2-15??m2 is obtained, while in the R A40-140??m2 range TMR can reach 40%-45%, in as-deposited samples. A limited number of junctions exhibits considerably lower R A values with respect to the average while keeping similar MR (down to 0.44??m2 with 20% and down to 2.2??m2 with 51%).

Ferreira, R.; Freitas, P. P.; MacKenzie, M.; Chapman, J. N.

2005-05-01

114

Grain-Boundary Grooving of Plasma-Sprayed Yttria-Stabilized Zirconia Thermal Barrier Coatings  

E-print Network

Grain-Boundary Grooving of Plasma-Sprayed Yttria-Stabilized Zirconia Thermal Barrier Coatings- sponsible for the microstructural changes of plasma-sprayed 7 wt% Y2O3­ZrO2 thermal barrier coatings with annealing from 8001 to 14001C. Mullins's thermal grooving theories have been applied to plasma-sprayed TBCs

Trice, Rodney W.

115

Force generation due to three-dimensional plasma discharge on a conical forebody using pulsed direct current actuators  

E-print Network

. Such force successfully controlled flow separation on airfoils at a high angle-of-attack, increased the lift-consistent multibody system of neutral oxygen species and its plasma. The equations governing the motion of charged,15 The actuator power can be reduced by 90% and its durability can be improved by operating it in an unsteady

Roy, Subrata

116

Failure of Thick, Low Density Air Plasma Sprayed Thermal Barrier Coatings.  

E-print Network

??This research was directed at developing fundamental understandings of the variables that influence the performance of air plasma sprayed (APS) yttria-stabilized zirconia (YSZ) thermal barrier (more)

Helminiak, Michael / MAH

2013-01-01

117

MERCURY OXIDIZATION IN NON-THERMAL PLASMA BARRIER DISCHARGE SYSTEM  

SciTech Connect

In the past decade, the emission of toxic elements from human activities has become a matter of great public concern. Hg, As, Se and Cd typically volatilize during a combustion process and are not easily caught with conventional air pollution control techniques. In addition, there is no pollution prevention technique available now or likely be available in the foreseeable future that can prevent the emission of these trace elements. These trace elements pose additional scientific challenge as they are present at only ppb levels in large gas streams. Mercury, in particular, has attracted significant attention due to its high volatility, toxicity and potential threat to human health. In the present research work, a non-thermal plasma dielectric barrier discharge technique has been used to oxidize Hg{sup 0}(g) to HgO. The basic premise of this approach is that Hg{sup 0} in vapor form cannot be easily removed in an absorption tower whereas HgO as a particulate is amiable to water scrubbing. The work presented in this report consists of three steps: (1) setting-up of an experimental apparatus to generate mercury vapors at a constant rate and modifying the existing non-thermal plasma reactor system, (2) solving the analytical challenge for measuring mercury vapor concentration at ppb level, and (3) conducting experiments on mercury oxidation under plasma conditions to establish proof of concept.

V.K. Mathur

2003-02-01

118

Acoustic emission evaluation of plasma-sprayed thermal barrier coatings  

NASA Technical Reports Server (NTRS)

Acoustic emission techniques have recently been used in a number of studies to investigate the performance and failure behavior of plasma-sprayed thermal barrier coatings. Failure of the coating is a complex phenomena, especially when the composite nature of the coating is considered in the light of possible failure mechanisms. Thus it can be expected that both the metal and ceramic components (i.e., the bond coat and ceramic overlay) of a composite thermal protection system influence the macroscopic behavior and performance of the coating. The aim of the present work is to summarize the 'state-of-the-art' in terms of this initial work and indicate where future progress may be made.

Berndt, C. C.

1984-01-01

119

Inter- and intracellular signaling induced by magnetomechanical actuation of plasma membrane channels  

NASA Astrophysics Data System (ADS)

Magnetic particles allow for non-invasive control over their spatial orientation and motion which makes them ideally suitable for studying real-time processes in living cells. Lithographically defined ferromagnetic disks with spin-vortex ground state have the advantage of zero net magnetization in remanence. This eliminates long-range magnetic forces which otherwise lead to the interaction between particles and their agglomeration. Moreover, magnetically soft permalloy particles have high magnetization of saturation thus requiring very low external field for inducing high magnetomotive force, compared to superparamagnetic particles. Our group has previously demonstrated that micron-sized permalloy disks can be used for destruction of cancer cells (D.-H. Kim, E. A. Rozhkova, I. V. Ulasov, S. D. Bader, T. Rajh, M. S. Lesniak, V. Novosad, Nat. Mater. 9, 165-171 (2010). In this work, we investigate the effects of magnetomechanical stimulation of human brain cancer cells with these particles. It will be shown that the actuation of ion channels in cell plasma membrane induces, on the one hand side, intracellular signaling triggering cell apoptosis and, on the other hand, it stimulates the energy transfer between the cells which carries the information about apoptotic signal.

Vitol, Elina A.; Rozhkova, Elena A.; Novosad, Valentyn; Bader, Samuel D.

2012-02-01

120

Effect of Dielectric and Liquid on Plasma Sterilization Using Dielectric Barrier Discharge Plasma  

PubMed Central

Plasma sterilization offers a faster, less toxic and versatile alternative to conventional sterilization methods. Using a relatively small, low temperature, atmospheric, dielectric barrier discharge surface plasma generator, we achieved ?6 log reduction in concentration of vegetative bacterial and yeast cells within 4 minutes and ?6 log reduction of Geobacillus stearothermophilus spores within 20 minutes. Plasma sterilization is influenced by a wide variety of factors. Two factors studied in this particular paper are the effect of using different dielectric substrates and the significance of the amount of liquid on the dielectric surface. Of the two dielectric substrates tested (FR4 and semi-ceramic (SC)), it is noted that the FR4 is more efficient in terms of time taken for complete inactivation. FR4 is more efficient at generating plasma as shown by the intensity of spectral peaks, amount of ozone generated, the power used and the speed of killing vegetative cells. The surface temperature during plasma generation is also higher in the case of FR4. An inoculated FR4 or SC device produces less ozone than the respective clean devices. Temperature studies show that the surface temperatures reached during plasma generation are in the range of 30C66C (for FR4) and 20C49C (for SC). Surface temperatures during plasma generation of inoculated devices are lower than the corresponding temperatures of clean devices. pH studies indicate a slight reduction in pH value due to plasma generation, which implies that while temperature and acidification may play a minor role in DBD plasma sterilization, the presence of the liquid on the dielectric surface hampers sterilization and as the liquid evaporates, sterilization improves. PMID:23951023

Mastanaiah, Navya; Johnson, Judith A.; Roy, Subrata

2013-01-01

121

Gas-confined barrier discharges: a simplified model for plasma dynamics in flame environments  

E-print Network

In this paper we evaluate the dynamics of non-thermal plasmas developing in extremely non-homogeneous environments. We present the gas-confined barrier discharge (GBD) concept and justify its importance as a first step to ...

Guerra-Garcia, Carmen

122

Micronucleus formation induced by dielectric barrier discharge plasma exposure in brain cancer cells  

NASA Astrophysics Data System (ADS)

Induction of micronucleus formation (cytogenetic damage) in brain cancer cells upon exposure of dielectric barrier discharge plasma has been investigated. We have investigated the influence of exposure and incubation times on T98G brain cancer cells by using growth kinetic, clonogenic, and micronucleus formation assay. We found that micronucleus formation rate directly depends on the plasma exposure time. It is also shown that colony formation capacity of cells has been inhibited by the treatment of plasma at all doses. Cell death and micronucleus formation are shown to be significantly elevated by 120 and 240 s exposure of dielectric barrier discharge plasma.

Kaushik, Nagendra K.; Uhm, Hansup; Ha Choi, Eun

2012-02-01

123

In-situ formation of multiphase air plasma sprayed barrier coatings for turbine components  

DOEpatents

A turbine component (10), such as a turbine blade, is provided which is made of a metal alloy (22) and a base, planar-grained thermal barrier layer (28) applied by air plasma spraying on the alloy surface, where a heat resistant ceramic oxide overlay material (32') covers the bottom thermal barrier coating (28), and the overlay material is the reaction product of the precursor ceramic oxide overlay material (32) and the base thermal barrier coating material (28).

Subramanian, Ramesh (Oviedo, FL)

2001-01-01

124

Laser drilling of cooling holes through plasma sprayed thermal barrier coatings  

Microsoft Academic Search

Laser drilling is a non-contact process that can be used to form small holes in a wide variety of materials with a high degree of precision and reproducibility. The advantages of being able to drill difficult materials, specifically superalloys and ceramics, are exploited in the laser drilling of cooling holes in thermal barrier coated superalloys. Plasma sprayed thermal barrier coatings

K. T. Voisey; T. W. Clyne

2004-01-01

125

Fatigue testing of plasma-sprayed thermal barrier coatings, Volume 2. Final report  

Microsoft Academic Search

A plasma sprayed thermal barrier coating for diesel engines were fatigue tested. Candidate thermal barrier coating materials were fatigue screened and a data base was generated for the selected candidate material. Specimen configurations are given for the bend fatigue tests, along with test setup, specimen preparation, test matrix and procedure, and data analysis.

T. A. Cruse; A. Nagy; C. F. Popelar

1990-01-01

126

Enhanced Design of Turbo-jet LPT by Separation Control Using Phased Plasma Actuators  

NASA Technical Reports Server (NTRS)

This work deals with the documentation and control of flow separation that occurs over turbine blades in the low-pressure turbine stage at low Reynolds numbers that exist at high altitude cruise. We utilize a specially constructed linear cascade that is designed to study the flow field over a generic LPT cascade consisting of Pratt & Whitney 'Pak B' shaped blades. This facility was constructed under a previous one-year NASA Glenn RC initiative. The center blade in the cascade is instrumented to measure the surface pressure coefficient distribution. Optical access allows two-component LDV measurement for boundary layer profiles. Experimental conditions have been chosen to give a range of chord Reynolds numbers from 10 to 100K, and a range of free-stream turbulence levels from u'/U(sub infinity)= 0.08 to 3 percent. The surface pressure measurements were used to define a region of separation and reattachment that depend on the free-stream conditions. The location of separation was found to be relatively insensitive to the experimental conditions. However, reattachment location was very sensitive to the turbulence level and Reynolds number. Excellent agreement was found between the measured pressure distributions and predictions from Euler and RANS simulations. Two-component LDV measurements are presently underway to document the mean and fluctuating velocity components in the boundary layer over the center blade for the range of experimental conditions. The fabrication of the plasma actuator is underway. These are designed to produce either streamwise vortices, or a downstream-directed wall jet. A precursor experiment for the former approach was performed with an array of vortex generators placed just upstream of the separation line. These led to reattachment except for the lowest Reynolds number. Progress has also been made on the proposed concept for a laterally moving wake. This involved constructing a smaller wind tunnel and molding an array of symmetric airfoils to form an array. Following its development, it will be scaled up and used to introduce lateral moving wakes upstream up the Pak-B cascade.

Ashpis, David (Technical Monitor); Corke, Thomas C.; Thomas, Flint O.

2003-01-01

127

Morphological and microstructural characterization of laser-glazed plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

Laser glazing has been revealing a high potential for the improvement of plasma-sprayed (PS) thermal barrier coatings (TBCs) by reducing surface roughness, eliminating open porosity on the surface and generating a controlled segmented crack network, although the relationship of the processing parameters with the resultant properties has not yet been completely established. In this investigation, TBCs consisting of atmospheric plasma-sprayed

C. Batista; A. Portinha; R. M. Ribeiro; V. Teixeira; M. F. Costa; C. R. Oliveira

2006-01-01

128

Understanding crack formation in plasma sprayed thermal barrier coatings and their effects on coating properties  

Microsoft Academic Search

As a key microstructural feature of plasma sprayed thermal barrier coatings (TBCs), microcracks determine the performance and service lifetimes of the coatings by influencing their thermal conductivity and compliance. The goal of this research is to obtain a fundamental understanding of crack formation in plasma sprayed microstructures, and their effect on mechanical and thermal properties through a synergistic combination of

Guosheng Ye

2004-01-01

129

Deposition of thermal barrier coatings using the solution precursor plasma spray process  

Microsoft Academic Search

The solution-precursor plasma-spray (SPPS) process is capable of producing highly durable thermal barrier coatings. In an effort to improve the understanding of the deposition mechanisms in this novel process, a series of specific experiments, where the substrate is held stationary and the plasma torch is programmed to scan a single pass across the substrate, were conducted and the resulting deposits

Liangde Xie; Xinqing Ma; Eric H. Jordan; Nitin P. Padture; Danny T. Xiao; Maurice Gell

2004-01-01

130

Examining the Role of Ozone in Surface Plasma Sterilization Using Dielectric Barrier  

E-print Network

Examining the Role of Ozone in Surface Plasma Sterilization Using Dielectric Barrier Discharge (DBD (DBD) devices are known ozone generators. Authors have previously demonstrated a DBD surface plasma and sterilization in 20 min (bacterial spores). The aim of this paper is to examine the role of the ozone in surface

Roy, Subrata

131

A hypersonic plasma bullet train traveling in an atmospheric dielectric-barrier discharge jet  

Microsoft Academic Search

An experimental observation of fast-moving plasma bullets produced in an atmospheric dielectric-barrier discharge jet is reported in this paper. Nanosecond imaging suggests that the atmospheric discharge jet consists of a plasma bullet train traveling at a hypersonic speed from 7.0 km\\/s to 43.1 km\\/s. Yet on a millisecond scale, the bullet train appears as a plasma jet of several centimeters

Jianjun Shi; Fangchun Zhong; Jing Zhang; D. W. Liu; M. G. Kong

2008-01-01

132

Recent Developments in the Field of Plasma-Sprayed Thermal Barrier Coatings  

Microsoft Academic Search

Thermal barrier coating (TBC) systems are widely used in gas turbines on thermally highly loaded parts as blades, vanes or combustion chamber to improve the performance of the engines. The standard plasma-sprayed systems consist of a vacuum plasma-sprayed (VPS) MCrAlY (M = Ni or Co) and an atmospherically plasma sprayed (APS) ceramic top layer made of yttria partially stabilised zirconia

R. Vaen; J.-E. Dring; M. Dietrich; H. Lehmann; D. Stver

133

Monitoring delamination of plasma-sprayed thermal barrier coatings by reflectance-enhanced luminescence  

Microsoft Academic Search

Plasma-sprayed thermal barrier coatings (TBCs) present a challenge for optical diagnostic methods to monitor TBC delamination, because the strong scattering exhibited by plasma-sprayed TBCs severely attenuates light transmitted through the TBC. This paper presents a new approach that indicates delamination in plasma-sprayed TBCs by utilizing a luminescent sublayer that produces significantly greater luminescence intensity from delaminated regions of the TBC.

Jeffrey I. Eldridge; Timothy J. Bencic

2006-01-01

134

Technical note: Plasma-sprayed ceramic thermal barrier coatings for smooth intermetallic alloys  

Microsoft Academic Search

A durable ceramic thermal barrier coating is applied directly to a smooth, highly oxidation resistant intermetallic alloy\\u000a in two layers. The first layer of ceramic is applied by low pressure plasma spraying and the second layer is applied by conventional\\u000a atmospheric pressure plasma spraying. This approach would allow the use of plasma sprayed ceramic coatings in applications\\u000a where a metallic

R. A. Miller; J. Doychak

1992-01-01

135

Local and Bi-Global Stability Analysis of a Plasma Actuated Boundary Layer  

E-print Network

of active and passive flow control systems. This type of actuator has a number of beneficial properties, Associate Fellow AIAA 1 of 14 American Institute of Aeronautics and Astronautics #12;I. Introduction, the TS wave is the instability that is most closely tied to the controlled transition of turbulence

Roy, Subrata

136

Numerical Investigation of Serpentine Plasma Actuators for Separation Control at Low Reynolds Number  

E-print Network

. For these types of applications, the flow often has some level of laminar behavior, which is important for control behavior of the flow control mechanism relative to the standard `linear' actuator due to the introduction to reattach them are two highly documented issues in flow control research1 . The separated flows that can

Roy, Subrata

137

Force Production Mechanisms of a Dielectric-Barrier Discharge Plasma Actuator  

E-print Network

charged particles is then transferred to the surrounding air through collisions with neutral particles. Lon Enloe , Gabriel I. Font , and Thomas E. McLaughlin� United States Air Force Academy, USAF Academy of ions through the applied electric field, and subsequent collisions with neutral particles. This work

Gregory, James W.

138

Plasma Surface Modification of Polymer Backsheets: Origins of Future Interfacial Barrier/Backsheet Failure (Poster)  

SciTech Connect

Flexible polymer substrates coated with inorganic oxide moisture barriers are a potential replacement for glass backsheets in thin-film PV (photovoltaic) modules. Silicon oxynitride (SiO{sub x}N{sub y}) deposited by plasma enhanced chemical vapor deposition (PECVD) on polyethylene terephthalate (PET) represents one potential new backsheet candidate. Barrier deposition runs at NREL have included a nitrogen-rich plasma pretreatment prior to barrier deposition with the intention of cleaning the PET surface and enhancing adhesion of the SiO{sub x}N{sub y} barrier film to PET; however, test coupons of PET/barrier/EVA/TPE failed after damp-heat exposure. (EVA is ethylene vinyl acetate and TPE is Tedlar{reg_sign}-PET-EVA). PET substrates exposed to plasma conditions similar to those used in pretreatment were examined by X-ray photoelectron spectroscopy (XPS) to reveal that new low molecular weight PET fragments were created at the PET surface. These fragments are responsible for barrier/PET interfacial failure and barrier transfer to the EVA encapsulant side following damp heat exposure.

Pankow, J. W.; Glick, S. H.

2006-05-01

139

Improving plasma actuator performance at low pressure, and an analysis of the pointing capabilities of cubeSats using Plasmonic Force Propulsion (PFP) thrusters  

NASA Astrophysics Data System (ADS)

This thesis details the work done on two unrelated projects, plasma actuators, an aerodynamic flow control device, and Plasmonic Force Propulsion (PFP) thrusters, a space propulsion system for small satellites. The first half of the thesis is a paper published in the International Journal of Flow Control on plasma actuators. In this paper the thrust and power consumption of plasma actuators with varying geometries was studied at varying pressure. It was found that actuators with longer buried electrodes produce the most thrust over all and that they substantially improved thrust at low pressure. In particular actuators with 75 mm buried electrodes produced 26% more thrust overall and 34% more thrust at low pressure than the standard 15 mm design. The second half details work done modeling small satellite attitude and reaction control systems in order to compare the use of Plasmonic Force Propulsion thrusters with other state of the art reaction control systems. The model uses bang bang control algorithms and assumes the worst case scenario solar radiation pressure is the only disturbing force. It was found that the estimated 50-500 nN of thrust produced by PFP thrusters would allow the spacecraft which use them extremely high pointing and positioning accuracies (<10-9 degrees and 3 pm). PFP thrusters still face many developmental challenges such as increasing specific impulse which require more research, however, they have great potential to be an enabling technology for future NASA missions such as the Laser Interferometer Space Antenna, and The Stellar Imager.

Friz, Paul Daniel

140

Thermal properties of plasma-sprayed functionally graded thermal barrier coatings  

Microsoft Academic Search

Plasma-sprayed thermal barrier coatings often have the problems of spallation and cracking in service owing to their poor bond strength and high residual stresses. Functionally graded thermal barrier coatings with a gradual compositional variation from heat resistant ceramics to fracture-resistant metals are proposed to mitigate these problems. In this paper, functionally graded yttria stabilized ZrO2\\/NiCoCrAlY coatings were prepared using pre-alloyed

K. A Khor; Y. W Gu

2000-01-01

141

Temperature measurements and adhesion properties of plasma sprayed thermal barrier coatings  

Microsoft Academic Search

Metal-ceramic coatings have been widely used for industrial applications, mainly in the gas turbine and diesel engine industries\\u000a as thermal barrier coatings (TBCs). Conventional thermal barrier coatings consist of a metallic bond coat and an insulating\\u000a ceramic topcoat. Temperatures and temperature gradients in the coating during plasma spraying play an important role on the\\u000a final coating quality, especially the temperature

C. R. C. Lima; R. da Exaltacao Trevisan

1999-01-01

142

Comparison of thermal cycling behavior of plasma-sprayed nanostructured and traditional thermal barrier coatings  

Microsoft Academic Search

Nanostructured and traditional thermal barrier coatings have been prepared by atmospherical plasma spraying (APS) on NiCrAlY-coated superalloy substrates. Nanostructured thermal barrier coating has relatively longer lifetime than the common coating after cyclic testing at 1050, 1100 and 1150C. A transient thermal structural finite element solution was employed to analyze the stress distribution in the coatings. The reasons why the two

Chungen Zhou; Na Wang; Huibin Xu

2007-01-01

143

Feasibility study of plasma sprayed Al2O3 coatings as diffusion barrier on CFC components  

NASA Astrophysics Data System (ADS)

Carbon fibre reinforced carbon (CFC) materials are increasingly applied as sample carriers in modern furnaces. Only their tendency to react with different metals at high temperatures by C-diffusion is a disadvantage, which can be solved by application of diffusion barriers. Within this study the feasibility of plasma sprayed Al2O3 coatings as diffusion barrier was studied. Al2O3 coatings were prepared by air plasma spraying (APS). The coatings were investigated in terms of their microstructure, bonding to CFC substrates and thermal stability. The results showed that Al2O3 could be well deposited onto CFC substrates. The coatings had a good bonding and thermal shock behavior at 1060C. At higher temperature of 1270C, crack network formed within the coating, showing that the plasma sprayed Al2O3 coatings are limited regarding to their application temperatures as diffusion barrier on CFC components.

Bobzin, Kirsten; Zhao, Lidong; Kopp, Nils; Warda, Thomas

2012-12-01

144

Development of a stable dielectric-barrier discharge enhanced laminar plasma jet generated at atmospheric pressure  

NASA Astrophysics Data System (ADS)

A stable nonthermal laminar atmospheric-pressure plasma source equipped with dielectric-barrier discharge was developed to realize more efficient plasma generation, with the total energy consumption reduced to nearly 25% of the original. Temperature and emission spectra monitoring indicates that this plasma is uniform in the lateral direction of the jet core region. It is also found that this plasma contains not only abundant excited argon atoms but also sufficient excited N2 and OH. This is mainly resulted from the escape of abundant electrons from the exit, due to the sharp decrease of sustaining voltage and the coupling between ions and electrons.

Tang, Jie; Li, Shibo; Zhao, Wei; Wang, Yishan; Duan, Yixiang

2012-06-01

145

Tunable one-dimensional plasma photonic crystals in dielectric barrier discharge  

SciTech Connect

A tunable one-dimensional plasma photonic crystal is obtained by using a dielectric barrier discharge with two liquid electrodes. It is formed by the self-organization of the filaments, rather than that in an artificial array of electrodes. The dispersion relations of the plasma photonic crystals are calculated by solving the Helmholtz equation using a method analogous to Kronig-Penney's problem. The photonic band diagrams of the plasma photonic crystals are studied when changing the filling factor, the lattice constant, and the electron density, based on the experimental results. The critical electron density is given, beyond which the plasma photonic crystal will have a remarkable band structure.

Fan Weili; Dong Lifang [College of Physics Science and Technology, Hebei University, Baoding 071002 (China)

2010-07-15

146

Critical Threshold Behavior for Steady-State Internal Transport Barriers in Burning Plasmas  

SciTech Connect

Burning tokamak plasmas with internal transport barriers are investigated by means of integrated modeling simulations. The barrier sustainment in steady state, differently from the barrier formation process, is found to be characterized by a critical behavior, and the critical number of the phase transition is determined. Beyond a power threshold, alignment of self-generated and noninductively driven currents occurs and steady state becomes possible. This concept is applied to simulate a steady-state scenario within the specifications of the International Thermonuclear Experimental Reactor.

Garcia, J.; Giruzzi, G.; Artaud, J. F.; Basiuk, V.; Decker, J.; Imbeaux, F.; Peysson, Y.; Schneider, M. [Association EURATOM-CEA, CEA/DSM/IRFM, Cadarache, F-13108 St. Paul lez Durance (France)

2008-06-27

147

Technical note - Plasma-sprayed ceramic thermal barrier coatings for smooth intermetallic alloys  

NASA Technical Reports Server (NTRS)

A new approach for plasma spray deposition of ceramic thermal barrier coatings directly to smooth substrates is described. Ceramic thermal barrier coatings were directly applied to substrates that had been coated with low-pressure plasma sprayed NiCrAlY bond coats and then centerless ground to simulate a smooth oxidation-resistant substrate. As the high-temperature oxidation behavior of NiAl+Zr is superior to that of MCrALY alloy, the bond coat is not required for oxidation resistance.

Miller, R. A.; Doychak, J.

1992-01-01

148

Atmospheric pressure resistive barrier air plasma jet induced bacterial inactivation in aqueous environment  

NASA Astrophysics Data System (ADS)

An atmospheric pressure resistive barrier air plasma jet is designed to inactivate bacteria in aqueous media in direct and indirect exposure modes of treatment. The resistive barrier plasma jet is designed to operate at both dc and standard 50-60 Hz low frequency ac power input and the ambient air at 50% humidity level was used as the operating gas. The voltage-current characteristics of the plasma jet were analyzed and the operating frequency of the discharge was measured to be 20 kHz and the plasma power was measured to be 26 W. The plasma jet rotational temperatures (Trot) are obtained from the optical emission spectra, from the N2C-B(2+) transitions by matching the experimental spectrum results with the Spectra Air (SPECAIR) simulation spectra. The reactive oxygen and nitrogen species were measured using optical emission spectroscopy and gas analyzers, for direct and indirect treatment modes. The nitric oxides (NO) were observed to be the predominant long lived reactive nitrogen species produced by the plasma. Three different bacteria including Staphylococcus aureus (Gram-positive), Escherichia coli (Gram-negative), and Neisseria meningitidis (Gram-negative) were suspended in an aqueous media and treated by the resistive barrier air plasma jet in direct and indirect exposure modes. The results show that a near complete bacterial inactivation was achieved within 120 s for both direct and indirect plasma treatment of S. aureus and E. coli bacteria. Conversely, a partial inactivation of N. meningitidis was observed by 120 s direct plasma exposure and insignificant inactivation was observed for the indirect plasma exposure treatment. Plasma induced shifts in N. meningitidis gene expression was analyzed using pilC gene expression as a representative gene and the results showed a reduction in the expression of the pilC gene compared to untreated samples suggesting that the observed protection against NO may be regulated by other genes.

Thiyagarajan, Magesh; Sarani, Abdollah; Gonzales, Xavier

2013-03-01

149

Plasma sprayed ceramic thermal barrier coating for NiAl-based intermetallic alloys  

NASA Technical Reports Server (NTRS)

A thermal barrier coating system consists of two layers of a zirconia-yttria ceramic. The first layer is applied by low pressure plasma spraying. The second layer is applied by conventional atmospheric pressure plasma spraying. This facilitates the attachment of a durable thermally insulating ceramic coating directly to the surface of a highly oxidation resistant NiAl-based intermetallic alloy after the alloy has been preoxidized to promote the formation of a desirable Al2O3 scale.

Miller, Robert A. (inventor); Doychak, Joseph (inventor)

1994-01-01

150

Towards durable thermal barrier coatings with novel microstructures deposited by solution-precursor plasma spray  

Microsoft Academic Search

The feasibility of a new processing methodsolution precursor plasma spray (SPPS)for the deposition of ZrO2-based thermal barrier coatings (TBCs) with novel structures has been demonstrated. These desirable structures in the new TBCs appear to be responsible for their improved thermal cycling life relative to conventional plasma-sprayed TBCs. Preliminary results from experiments aimed at understanding the SPPS deposition mechanisms suggest that

N. P. Padture; K. W. Schlichting; T. Bhatia; A. Ozturk; B. Cetegen; E. H. Jordan; M. Gell; S. Jiang; T. D. Xiao; P. R. Strutt; E Garc??a; P Miranzo; M. I Osendi

2001-01-01

151

Development of a micromechanical life prediction model for plasma sprayed thermal barrier coatings  

Microsoft Academic Search

A widely used method to produce thermal barrier coating (TBC) systems is the vacuum plasma spraying of a highly dense bondcoat layer with a defined surface roughness and the atmospheric plasma spraying (APS) of a porous (1015%) Y2O3-stabilized zirconia top coat. In thermal cycling operation these systems often fail by crack initiation and propagation close to the bondcoattop coat interface.

R. Vaen; G. Kerkhoff; D. Stver

2001-01-01

152

Origin of darkening in 8 wt% yttria-zirconia plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

This paper reports on the origins of darkening of 8 wt% YO-ZrO air plasma-sprayed (APS) and low-pressure plasma-sprayed (LPPS) thermal barrier coatings (TBC) studied using x-ray photoelectron spectroscopy. The change of valence states of zirconium, due to the reduction of ZrO to ZrO, was responsible for darkening of TBC. Quantification of Zr{sup 3+} oxide was related both to the black

Gabriel Maria Ingo

1991-01-01

153

Thermal barrier coatings on turbine blades by plasma spraying with improved cooling  

Microsoft Academic Search

Turbine blades were coated with a thermal barrier coating system consisting of an MCrAlY bond coat about 100 micron thick deposited by Low Pressure Plasma Spraying (LPPS) and a 300 micron thick ZrO2-7 wt pct Y2O3 top coat. The latter was manufactured by both Atmosphere and Temperature Controlled Spraying (ATCS) and Air Plasma Spraying using internal air cooling through the

T. Cosack; L. Pawlowski; S. Schneiderbanger; S. Sturlese

1992-01-01

154

Low-thermal-conductivity plasma-sprayed thermal barrier coatings with engineered microstructures  

Microsoft Academic Search

The solution precursor plasma spray (SPPS) process has been used to deposit ZrO27wt.% Y2O3 thermal barrier coatings (TBCs) that contain alternate layers of low and high porosities (layered-SPPS). The thermal conductivity of the layered-SPPS coating is found to be lower than those of both a SPPS coating with distributed porosity and an air-plasma-sprayed coating of the same composition, in the

Amol D. Jadhav; Nitin P. Padture; Eric H. Jordan; Maurice Gell; Pilar Miranzo; Edwin R. Fuller

2006-01-01

155

Thermal barrier coatings on turbine blades by plasma spraying with improved cooling  

Microsoft Academic Search

Turbine blades were coated with a thermal barrier coating system consisting of an MCrAlY bond coat about 100 [mu]m thick deposited by Low-Pressure Plasma Spraying (LPPS) and a 300 [mu]m thick ZrO[sub 2]-7 wt.% Y[sub 2]O[sub 3] top coat. The latter was manufactured by both Atmosphere and Temperature Controlled Spraying (ATCS) and Air Plasma Spraying (APS) using internal air cooling

T. Cosack; S. Schneiderbanger; L. Pawlowski; S. Sturlese

1994-01-01

156

Oxidation and degradation of a plasma-sprayed thermal barrier coating system  

Microsoft Academic Search

The isothermal oxidation behavior of thermal barrier coating (TBC) specimens consisting of single-crystal superalloy substrates, vacuum plasma-sprayed Ni?22Cr?10Al?1Y bond coatings and air plasma-sprayed 7.5 wt.% yttria stabilized zirconia (YSZ) top coatings was evaluated by high-mass thermogravimetric analysis at 1150C for up to 200 h. Coating durability was assessed by furnace cycling at 1150C. Coatings and reaction products were characterized by

J. Allen Haynes; E. Douglas Rigney; Mattison K. Ferber; Wallace D. Porter

1996-01-01

157

Structureproperty differences between supersonic and conventional atmospheric plasma sprayed zirconia thermal barrier coatings  

Microsoft Academic Search

Yttria-stabilized zirconia (YSZ) based thermal barrier coatings (TBCs) were deposited by high efficiency supersonic atmospheric plasma spraying (SAPS) system. The microstructure and thermal shock resistance of the SAPS-TBCs were investigated. As compared to conventional atmospheric plasma sprayed TBCs (APS-TBCs) with the same composition, the microstructure of SAPS-TBCs was much finer. It was found that the thickness of lamellar structure consisted

Y. Bai; Z. H. Han; H. Q. Li; C. Xu; Y. L. Xu; C. H. Ding; J. F. Yang

2011-01-01

158

Deposition mechanisms of thermal barrier coatings in the solution precursor plasma spray process  

Microsoft Academic Search

In an effort to understand the deposition mechanisms in the solution precursor plasma spray (SPPS)a promising method for the deposition of highly-durable thermal barrier coatingssome model spray experiments were performed. In the SPPS process, an aqueous chemical precursor feedstock, which results in a ZrO27wt.%Y2O3 ceramic solid solution coating, is injected into the plasma jet and the coating is deposited on

Liangde Xie; Xinqing Ma; Eric H. Jordan; Nitin P. Padture; Danny T. Xiao; Maurice Gell

2004-01-01

159

Dielectric barrier plasma dynamics for active control of separated flows  

SciTech Connect

The dynamics of separation mitigation with asymmetric dielectric barrier discharges is explored by considering the gas flow past a flat plate at an angle of attack. A self-consistent model utilizing motion of electrons, ions, and neutrals is employed to couple the electric force field to the momentum of the fluid. The charge separation and concomitant electric field yield a time-averaged body force which is oriented predominantly downstream, with a smaller transverse component towards the wall. This induces a wall-jet-like feature that effectively eliminates the separation bubble. The impact of several geometric and electrical operating parameters is elucidated.

Roy, Subrata; Singh, K.P.; Gaitonde, Datta V. [Computational Plasma Dynamics Laboratory, Mechanical Engineering, Kettering University, Flint, Michigan 48504 (United States); Computational Sciences Branch, Air Vehicles Directorate, Air Force Research Laboratory, Wright Patterson AFB, Ohio 45433 (United States)

2006-03-20

160

Nondestructive evaluation of plasma-sprayed thermal barrier coatings  

SciTech Connect

Acoustic emission has been used as a nondestructive evaluation technique to examine the thermal shock response of thermal barrier coatings. In this study, samples of partially stabilized zirconia powder were sprayed and acoustic emission (AE) data were taken in a series of thermal shock tests in an effort to correlate AE with a given failure mechanism. Microstructural evidence was examined using parallel beam x-ray diffraction and optical microscopy. The AE data are discussed in terms of cumulative amplitude distributions and the use of this technique to characterize fracture events.

Andrews, D.J.; Taylor, J.A.T. [Alfred Univ., NY (United States). New York State Coll. of Ceramics

1997-10-01

161

The Effect of Air Plasma on Sterilization of Escherichia coli in Dielectric Barrier Discharge  

NASA Astrophysics Data System (ADS)

In this work, a Dielectric Barrier Discharge (DBD) air plasma was used to sterilize Escherichia coli (E. coli) on the surface of medical Polyethylene Terephthalate (PET) film. The leakage of cellular DNA and protein by optical absorbance measurement at 260 nm and 280 nm, together with transmission electron microscopy (TEM) about cell morphology were performed after sterilization to analyse inactivation mechanisms. The results indicated that the DBD air plasma was very effective in E. coli sterilization. The plasma germicidal efficiency depended on the plasma treatment time, the air-gap distance, and the applied voltage. Within 5 min of plasma treatment, the germicidal efficiency against E. coli could reach 99.99%. An etching action on cell membranes by electrons, ions and radicals is the primary mechanism for DBD air plasma sterilization, which leads to the effusion of cellular contents (DNA and protein) and bacterial death.

Hu, Miao; Guo, Yun

2012-08-01

162

Sintering and Interface Strain Tolerance of Plasma-Sprayed Thermal and Environmental Barrier Coatings  

NASA Technical Reports Server (NTRS)

Ceramic thermal and environmental barrier coatings will be more aggressively designed to protect gas turbine engine hot section SiC/SiC Ceramic Matrix Composite (CMC) components in order to meet future engine higher fuel efficiency and lower emission goals. A coating system consisting of a zirconia-based oxide topcoat (thermal barrier) and a mullite/BSAS silicate inner coat (environmental barrier) is often considered a model system for the CMC applications. However, the coating sintering, and thermal expansion mismatch between the zirconia oxide layer and the silicate environmental barrier/CMC substrate will be of major concern at high temperature and under thermal cycling conditions. In this study, the sintering behavior of plasma-sprayed freestanding zirconia-yttria-based thermal barrier coatings and mullite (and/or barium-strontium-aluminosilicate, i.e., BSAS) environmental barrier coatings was determined using a dilatometer in the temperature range of 1200-1500 C. The effects of test temperature on the coating sintering kinetics were systematically investigated. The plasma-sprayed zirconia-8wt.%yttria and mullite (BSAS) two-layer composite coating systems were also prepared to quantitatively evaluate the interface strain tolerance of the coating system under thermal cycling conditions based on the dilatomentry. The cyclic response of the coating strain tolerance behavior and interface degradation as a function of cycle number will also be discussed.

Zhu, Dongming; Leissler, George W.; Miller, Robert A.

2003-01-01

163

Characterization of a Dielectric Barrier Plasma Gun Discharging at Atmospheric Pressure  

Microsoft Academic Search

We develop a plasma gun based on dielectric barrier discharge and working at atmospheric pressure. A theoretical model to predict the gun discharge voltage is built, which is in agreement with the experimental results. After investigating the characterization of discharging gun and utilizing it for polymerization, we find that the gun can be used as a source to generate a

Guang-Qiu Zhang; Yuan-Jing Ge; Yue-Fei Zhang; Guang-Liang Chen

2004-01-01

164

Dielectric barrier plasma dynamics for active control of separated flows Subrata Roya  

E-print Network

in propulsion,1 external aerodynamics about an aircraft wing where an efficient passive2 or active control3Dielectric barrier plasma dynamics for active control of separated flows Subrata Roya and K. P geometric and electrical operating parameters is elucidated. © 2006 American Institute of Physics. DOI: 10

Roy, Subrata

165

Atmospheric plasma sprayed thick thermal barrier coatings with high segmentation crack density  

Microsoft Academic Search

Atmospheric plasma sprayed thick thermal barrier coatings (TBCs), comprising of 1.5 mm thickness yttria stabilized zirconia (YSZ) coating, have been developed for increasing thermal protection of combustor applications. Different segmentation crack densities of the YSZ coating were created by controlling the deposition conditions. It was found that the substrate temperature played a dominant role in determining the segmentation crack density.

H. B. Guo; R. Vaen; D. Stver

2004-01-01

166

Thermophysical properties and thermal cycling behavior of plasma sprayed thick thermal barrier coatings  

Microsoft Academic Search

Thick yttria stabilized zirconia (YSZ) thermal barrier coatings (TBCs) of 1.5 mm thickness were produced using atmospheric plasma spraying (APS). The microstructures, thermophysical properties and failure behaviour of the coatings were studied. The coating sprayed at high substrate temperature contained a fine segmentation crack network consisting of circular segments with a diameter of 0.7 mm. This coating had a thermal

H. B. Guo; R. Vaen; D. Stver

2005-01-01

167

Measurement of the elastic modulus of a plasma-sprayed thermal barrier coating using spherical indentation  

Microsoft Academic Search

Failure in plasma-sprayed thermal barrier coatings systems mostly takes place in the ceramic topcoat or at the interface between the topcoat and the bondcoat. The failure normally occurs by spallation of the topcoat at shutdown operations from high temperatures where compressive thermal mismatch stresses are induced in the topcoat. In order to analyse the residual stresses, knowledge about the elastic

Mats Eskner; Rolf Sandstrm

2004-01-01

168

Non-destructive evaluation of plasma sprayed functionally graded thermal barrier coatings  

Microsoft Academic Search

Acoustic emission (AE) as a non-destructive evaluation technique has recently been used in a number of studies to investigate the performance and failure behavior of plasma sprayed thermal barrier coatings. The mechanism of coating failure is complex, especially when considering the composite nature of the coating. In the present paper, the thermal shock tests with in situ acoustic emission are

L Fu; K. A Khor; H. W Ng; T. N Teo

2000-01-01

169

Microstructures and Properties of Thermal Barrier Coatings Plasma-Sprayed by Nanostructured Zirconia  

Microsoft Academic Search

In gas turbine engine, the study of thermal barrier coatings (TBCs) has always been paid more attention because it can effectively reduce metal interface temperatures, reduce oxidation and extend life. In this paper, the microstructures and properties of TBCs plasma-sprayed by nanostructured zirconia were investigated. The TBCs had higher adhesive strength, better thermal shock resistance and micro-cracking resistance to compare

Tong CUI; Ji-jie WANG; Ren-guo GUAN; Li-qing Chen; Guan-ming QIU

2007-01-01

170

Low thermal conductivity thermal barrier coating deposited by the solution plasma spray process  

Microsoft Academic Search

This work seeks to develop an innovative thermal barrier coating (TBC) that will exhibit low thermal conductivity and high durability compared with that of current TBCs. To achieve this objective, a multiple component co-doped zirconia chemistry was selected for the topcoat of the TBC system, and a new process Solution Plasma Spray (SPS or SPPS) was employed to

Xinqing Ma; Fang Wu; Jeff Roth; Maurice Gell; Eric H. Jordan

2006-01-01

171

Deformation behavior of plasma-sprayed thick thermal barrier coatings  

Microsoft Academic Search

A fundamental deformation study of several candidate diesel engine coating materials, independent of a substrate, has been conducted. Both plasma-sprayed 8%Y2O3ZrO2 and CaTiO3 material specimens were subjected to various isothermal mechanical tests from room temperature to 800C to understand their basic constitutive behavior. In this work, it was found that all of the coating materials showed significant irreversible deformation behavior

Ed F. Rejda; Darrell F. Socie; Takamoto Itoh

1999-01-01

172

Emission properties of an atmospheric-pressure helium plasma jet generated by a barrier discharge  

NASA Astrophysics Data System (ADS)

The emission properties of an atmospheric-pressure helium plasma jet generated by a barrier discharge in a capillary blown with helium are studied. The spectral composition of the radiation of the studied plasma jet and the spatial-spectral distribution of its intensity are investigated in detail. It is shown that the emission spectrum of the generated plasma jet outside the capillary consists mainly of electronic-vibrational transitions of the first negative system of ionized nitrogen molecules N{2/+}( B 2?{/u +} ? X 2?{/g +}) and the second positive system of neutral nitrogen molecules N2( C 3? u ? B 3? g ).

Korbut, A. N.; Kelman, V. A.; Zhmenyak, Yu. V.; Klenovskii, M. S.

2014-06-01

173

Failure of physical vapor deposition\\/plasma-sprayed thermal barrier coatings during thermal cycling  

Microsoft Academic Search

ZrO2-7 wt.% Y2O3 plasma-sprayed (PS) coatings were applied on high-temperature Ni-based alloys precoated by physical vapor deposition with\\u000a a thin, dense, stabilized zirconia coating (PVD bond coat). The PS coatings were applied by atmospheric plasma spraying (APS)\\u000a and inert gas plasma spraying (IPS) at 2 bar for different substrate temperatures. The thermal barrier coatings (TBCs) were\\u000a tested by furnace isothermal

V. Teixeira; M. Andritschky; H. Gruhn; W. Mallner; H. P. Buchkremer; D. Stver

2000-01-01

174

Permeation barrier coating and plasma sterilization of PET bottles and foils  

NASA Astrophysics Data System (ADS)

Modern packaging materials such as polyethylene terephthalate (PET) offer various advantages over glass or metal containers. Beside this they only offer poor barrier properties against gas permeation. Therefore, the shelf-live of packaged food is reduced. Additionally, common sterilization methods like heat, hydrogen peroxide or peracetic acid may not be applicable due to reduced heat or chemical resistance of the plastic packaging material. For the plasma sterilization and permeation barrier coating of PET bottles and foils, a microwave driven low pressure plasma reactor is developed based on a modified Plasmaline antenna. The dependencies of important plasma parameters, such as gas mixture, process pressure, power and pulse conditions on oxygen permeation through packaging foil are investigated. A residual permeation as low as J = 1.0 0.3 cm^3m-2day-1bar-1 for 60 nm thick silicon oxide (SiOx) coated PET foils is achieved. To discuss this residual permeation, coating defects are visualized by capacitively coupled atomic oxygen plasma etching of coated substrate. A defect density of 3000 mm-2 is revealed responsible for permeation. For plasma sterilization, optimized plasma parameters based on fundamental research of plasma sterilization mechanisms permit short treatment times of a few seconds.

Steves, Simon; Deilmann, Michael; Bibinov, Nikita; Awakowicz, Peter

2009-10-01

175

Visualization by discharge illumination technique and modification by plasma actuator of rarefied Mach 2 airflow around a cylinder  

NASA Astrophysics Data System (ADS)

The use of plasma actuators for flow control has received considerable attention in recent years. This kind of device seems to be an appropriate means of raising abilities in flow control thanks to total electric control, no moving parts and a fast response time. The experimental work presented here shows, firstly, the non-intrusive character of the visualization of the density field of an airflow around a cylinder obtained using a plasma luminescence technique. Experiments are made in a continuous supersonic wind tunnel. The static pressure in the flow is 8 Pa, the mean free path is about 0.3 mm and the airflow velocity is 510 m s-1. Pressure measurements obtained by means of glass Pitot tube without the visualization discharge are proposed. Measured and simulated pressure profiles are in good agreement in the region near the cylinder. There is good correlation between numerical simulations of the supersonic flow field, analytical model predictions and experimental flow visualizations obtained by a plasma luminescence technique. Consequently, we show that the plasma luminescence technique is non-intrusive. Secondly, the effect of a dc discharge on a supersonic rarefied air flow around a cylinder is studied. An electrode is flush mounted on the cylinder. Stagnation pressure profiles are examined for different electrode positions on the cylinder. A shock wave modification depending on the electrode location is observed. The discharge placed at the upstream stagnation point induces an upstream shift of the bow shock, whereas a modification of the shock wave shape is observed when it is placed at 45 or 90.

Leger, L.; Sellam, M.; Barbosa, E.; Depussay, E.

2013-06-01

176

A hypersonic plasma bullet train traveling in an atmospheric dielectric-barrier discharge jet  

SciTech Connect

An experimental observation of fast-moving plasma bullets produced in an atmospheric dielectric-barrier discharge jet is reported in this paper. Nanosecond imaging suggests that the atmospheric discharge jet consists of a plasma bullet train traveling at a hypersonic speed from 7.0 km/s to 43.1 km/s. Yet on a millisecond scale, the bullet train appears as a plasma jet of several centimeters long. The plasma bullets are produced through several possible mechanisms, the most likely of which is related to the ionization wave. Time and space resolved optical emission spectroscopy show that reactive plasma species can be delivered to different spatial sites with varying quantities.

Shi Jianjun; Zhong Fangchun; Zhang Jing; Liu, D. W.; Kong, M. G. [College of Science, Donghua University, Shanghai 201620 (China); Department of Electronic and Electrical Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU (United Kingdom)

2008-01-15

177

Plasma surface treatments by using a dielectric barrier discharge for the deposition of diamond films  

NASA Astrophysics Data System (ADS)

For plasma surface treatments at atmospheric pressure, a 2 kW dielectric barrier discharge (DBD) source was developed. It was investigated via an optical emission spectroscopy (OES), an IR camera and volt-ampere meters with a computer. It was confirmed that the developed source stably generated plasmas. After the diamonds had been seeded, the plasma surface treatments were performed as pretreatment to improve the deposition of the diamond films by using the developed DBD source with argon gas. The substrate surfaces were analyzed using a contact angle analysis (CAA), an atomic force microscopy (AFM) and a 3D Nano Profiling System. The results of the plasma surface treatments showed an improvement in the surface free energies of the substrates. The plasma surface treatments for 5 minutes also resulted in a more uniform distribution of the seeding diamonds on the substrates, which improved the depositions of the diamond films.

Kang, I. J.; Ko, M. G.; Yang, J. K.; Lee, H. J.

2013-07-01

178

American Institute of Aeronautics and Astronautics Physics Based Analysis of Horseshoe Plasma Actuator for Improving  

E-print Network

1 American Institute of Aeronautics and Astronautics Physics Based Analysis of Horseshoe Plasma. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. #12;2 American

Roy, Subrata

179

Constrained sintering of an air-plasma-sprayed thermal barrier coating A.C.F. Cocks a,*, N.A. Fleck b  

E-print Network

Constrained sintering of an air-plasma-sprayed thermal barrier coating A.C.F. Cocks a,*, N.A. Fleck model is presented for the constrained sintering of an air-plasma-sprayed, thermal barrier coating upon; Micromechanical modelling; Creep 1. Introduction Air-plasma-sprayed (APS) thermal barrier coatings (TBCs

Fleck, Norman A.

180

Phase transformation and bond coat oxidation behavior of plasma-sprayed zirconia thermal barrier coating  

Microsoft Academic Search

ZrO2CeO2Y2O3 and ZrO2Y2O3 thermal barrier coatings were prepared using the air plasma spray process. Phase transformation in the ceramic top coating, bond coat oxidation and thermal barrier properties were investigated to compare ZrO2CeO2Y2O3 with ZrO2Y2O3 at 1300C under high temperature thermal cycles. In the as-sprayed condition, both coatings showed a 7?11% porosity fraction and typical lamellar structures formed by continuous

C. H. Lee; H. K. Kim; H. S. Choi; H. S. Ahn

2000-01-01

181

Inactivation of Campylobacter jejuni with dielectric barrier discharge plasma using air and nitrogen gases.  

PubMed

Air and nitrogen gas are commonly used feed gases for plasma generation and are economically useful in industrial applications. The two gases were compared in dielectric barrier discharge plasma for the inactivation of Campylobacter jejuni on an agar surface. Plasma treatment with nitrogen gas for 20 s did not yield any reduction (p>0.05) in viable cell count. However, a 0.8-log reduction (p<0.05) in colony-forming units (CFU) occurred when the nitrogen gas was supplemented with 2% (vol/vol) air. The use of air only, air supplemented with 2% (vol/vol) nitrogen, or oxygen only further decreased the viable cell counts by 0.7-1.7-log CFU (p<0.05). These results suggest that oxygen in plasma generation is critically important for the increased inactivation effect. Scanning electron microscopy analysis showed much cell debris including fragmented flagella in the sample exposed to air plasma, while no cell debris was found in the sample exposed to nitrogen plasma. In transmission electron microscopy analysis, many C. jejuni cells exposed to air plasma had truncated flagella with sharp bends, while the cells exposed to nitrogen plasma were normal, strongly suggesting that the air plasma can reduce the virulence of C. jejuni. A BacLight assay showed that air plasma damaged the cellular membrane (p<0.05), whereas nitrogen plasma did not after 5- or 20-s treatment. The damage to the membrane was consistent with the reduced viable cell count. Based on confocal microscopic analysis, the similar results were found by visualizing the fluorescent-dye-stained cells. In addition, the prolonged nitrogen plasma for 2 min also damaged many cellular membranes. This study shows that air, especially oxygen, is more effective and destructive than nitrogen and provides evidence that membrane damage may be a major mechanism for the inactivation of C. jejuni exposed to plasma. PMID:24971667

Kim, Joo-Sung; Lee, Eun-Jung; Kim, Yun-Ji

2014-08-01

182

Treatment of Candida albicans biofilms with low-temperature plasma induced by dielectric barrier discharge and atmospheric pressure plasma jet  

NASA Astrophysics Data System (ADS)

Because of some disadvantages of chemical disinfection in dental practice (especially denture cleaning), we investigated the effects of physical methods on Candida albicans biofilms. For this purpose, the antifungal efficacy of three different low-temperature plasma devices (an atmospheric pressure plasma jet and two different dielectric barrier discharges (DBDs)) on Candida albicans biofilms grown on titanium discs in vitro was investigated. As positive treatment controls, we used 0.1% chlorhexidine digluconate (CHX) and 0.6% sodium hypochlorite (NaOCl). The corresponding gas streams without plasma ignition served as negative treatment controls. The efficacy of the plasma treatment was determined evaluating the number of colony-forming units (CFU) recovered from titanium discs. The plasma treatment reduced the CFU significantly compared to chemical disinfectants. While 10 min CHX or NaOCl exposure led to a CFU log10 reduction factor of 1.5, the log10 reduction factor of DBD plasma was up to 5. In conclusion, the use of low-temperature plasma is a promising physical alternative to chemical antiseptics for dental practice.

Koban, Ina; Matthes, Rutger; Hbner, Nils-Olaf; Welk, Alexander; Meisel, Peter; Holtfreter, Birte; Sietmann, Rabea; Kindel, Eckhard; Weltmann, Klaus-Dieter; Kramer, Axel; Kocher, Thomas

2010-07-01

183

Generation of tunable plasma photonic crystals in meshed dielectric barrier discharge  

NASA Astrophysics Data System (ADS)

Tunable superlattice plasma photonic crystals are obtained in a meshed dielectric barrier discharge. These plasma photonic crystals are composed of thin artificial lattices and thick self-organized lattices, and can be tuned easily by adjusting the applied voltage. A plasma photonic crystal with self-organized hexagonal lattice coupled to artificial square lattice is first realized. The dispersion relations of the square sublattices with different radii, which are recorded by an intensified charge-coupled device camera, are calculated. The results show that the thick square sublattice has the higher band edge frequencies and wider band widths. Band gaps of superlattice plasma photonic crystals are actually temporal integrations of those of transient sublattices.

Wang, Yongjie; Dong, Lifang; Liu, Weibo; He, Yafeng; Li, Yonghui

2014-07-01

184

Detection of hydroxyl radicals during regeneration of granular activated carbon in dielectric barrier discharge plasma system  

NASA Astrophysics Data System (ADS)

To understand the reactions taking place in the dielectric barrier discharge (DBD) plasma system of activated carbon regeneration, the determination of active species is necessary. A method based on High Performance Liquid Chromatography with radical trapping by salicylic acid, has been developed to measure hydroxyl radical (OH) in the DBD plasma reactor. The effects of applied voltage, treatment time, and gas flow rate and atmosphere were investigated. Experimental results indicated that increasing voltage, treatment time and air flow rate could enhance the formation of OH. Oxygen atmosphere and a suitable GAC water content were contributed to OH generation. The results give an insight into plasma chemical processes, and can be helpful to optimize the design and application for the plasma system.

Tang, Shoufeng; Lu, Na; Shang, Kefeng; Li, Jie; Wu, Yan

2013-03-01

185

Combustion stabilization using serpentine plasma actuators Chin-Cheng Wang and Subrata Roya)  

E-print Network

to pinching and spreading effects suitable for rapid flow mixing. Here, the influence of serpentine plasma three- dimensional flow instabilities that can influence beyond the flow boundary layer. It not only has an overall effect of slowing gas-flow speed in the flame replicating a virtual bluff body

Roy, Subrata

186

A dielectric-barrier discharge enhanced plasma brush array at atmospheric pressure  

SciTech Connect

This study developed a large volume cold atmospheric plasma brush array, which was enhanced by a dielectric barrier discharge by integrating a pair of DC glow discharge in parallel. A platinum sheet electrode was placed in the middle of the discharge chamber, which effectively reduced the breakdown voltage and working voltage. Emission spectroscopy diagnosis indicated that many excited argon atoms were distributed almost symmetrically in the lateral direction of the plasma. The concentration variations of reactive species relative to the gas flow rate and discharge current were also examined.

Li Xuemei; Zhan Xuefang; Yuan Xin; Zhao Zhongjun; Yan Yanyue; Duan Yixiang [Research Center of Analytical Instrumentation, Analytical Testing Center, College of Chemistry, Sichuan University, Chengdu (China); Tang Jie [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics of CAS, Xi'an (China)

2013-07-15

187

Oxidation and degradation of a plasma-sprayed thermal barrier coating system  

SciTech Connect

The isothermal oxidation behavior of thermal barrier coating (TBC) specimens consisting of single-crystal superalloy substrates, vacuum plasma-sprayed Ni-22Cr-10Al-1Y bond coatings and air plasma-sprayed 7.5 wt.% yttria stabilized zirconia top coatings was evaluated by thermogravimetric analysis at 1150{degrees}C for up to 200 hours. Coating durability was assessed by furnace cycling at 1150{degrees}C. Coatings and reaction products were identified by x-ray diffraction, field-emission scanning electron microscopy and energy dispersive spectroscopy.

Haynes, J.A. [Univ. of Alabama, Birmingham, AL (United States). Dept. of Materials and Mechanical Engineering; Ferber, M.K.; Porter, W.D. [Oak Ridge National Lab., TN (United States)

1996-04-01

188

Removal of formaldehyde from gas streams via packed-bed dielectric barrier discharge plasmas  

Microsoft Academic Search

Formaldehyde is a major indoor air pollutant and can cause serious health disorders in residents. This work reports the removal of formaldehyde from gas streams via alumina-pellet-filled dielectric barrier discharge plasmas at atmospheric pressure and 70 C. With a feed gas mixture of 140 ppm HCHO, 21.0% O2, 1.0% H2O in N2, ~92% of formaldehyde can be effectively destructed at

Hui-Xian Ding; Ai-Min Zhu; Xue-Feng Yang; Cui-Hong Li; Yong Xu

2005-01-01

189

Highly durable thermal barrier coatings made by the solution precursor plasma spray process  

Microsoft Academic Search

The solution precursor plasma spray (SPPS) process offers the prospect of depositing highly durable thermal barrier coatings (TBCs) of low thermal conductivity. In this study, a Taguchi design of experiments was employed to optimize the SPPS process. The spallation life of SPPS TBCs on a MCrAlY bond coated Ni-base superalloy substrate deposited under the optimized processing conditions was demonstrated to

Maurice Gell; Liangde Xie; Xinqing Ma; Eric H. Jordan; Nitin P. Padture

2004-01-01

190

Characterization of microstructural defects in plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

Thermal barrier coatings with a NiCrAlY bond coating and a 1.5 mm thick zirconia top coating were air plasma sprayed onto\\u000a a nickel-base substrate. The top coatings were deposited with the same spraying parameters except for the amount of external\\u000a cooling, which varied from no cooling to the maximum available. This resulted in four sets of samples produced with different

P. Bengtsson; T. Johannesson

1995-01-01

191

Microstructure and Thermal Properties of Plasma Sprayed Thermal Barrier Coatings from Nanostructured YSZ  

Microsoft Academic Search

Nanostructured yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) were produced by atmospheric plasma spraying.\\u000a The microstructure of the sprayed coating was characterized by transmission electron microscope (TEM) and scanning electron\\u000a microscope (SEM). The nano-coating had a higher porosity of ~25% than the conventional coating, which is mainly attributed\\u000a to the large amount of intersplat gaps in the nano-coating. The thermal

Jing Wu; Hong-Bo Guo; Le Zhou; Lu Wang; Sheng-Kai Gong

2010-01-01

192

A model for residual stress evolution in air-plasma-sprayed zirconia thermal barrier coatings  

SciTech Connect

Ruby fluorescence spectroscopy indicates that residual stress in air-plasma-sprayed zirconia thermal barrier coatings is a function of the local interface geometry. The stress profile of a simulated rough interface characterized by ``peaks'' and ``valleys'' was modeled with a finite-element approach that accounted for thermal mismatch, oxide scale growth, and top coat sintering. Dependence of the stress profile on interface geometry and microstructure was investigated, and the results were compared with measured stresses.

Nair, B. G.; Singh, J. P.; Grimsditch, M.

2000-02-28

193

Thermal properties of plasma-sprayed thermal barrier coating with bimodal structure  

Microsoft Academic Search

Nanostructured zirconia coatings have been prepared by atmospherical plasma spraying (APS) on NiCrAlY-coated superalloy substrates. The isothermal oxidation test results indicate that the oxidation kinetics of nanostructured TBC follows a parabolic law and the oxidation resistance of the nanostructured TBC is comparable to that of the conventional TBC. The nanostructured thermal barrier coatings exhibit excellent thermal cyclic resistance and low

Qinghe Yu; Abdul Rauf; Na Wang; Chungen Zhou

2011-01-01

194

Segmented thermal barrier coatings produced by atmospheric plasma spraying hollow powders  

Microsoft Academic Search

Segmented thermal barrier coatings were produced by plasma spraying hollow and solid ZrO28 wt.% Y2O3 powders. The solid powder (SP) had greater capability of producing segmentation cracks in coating compared with the hollow powder (HP). High substrate temperature (Ts) gave rise to an increased segmentation crack density (Ds). The segmentation crack network was still stable even after sintering at 1300

H. B. Guo; S. Kuroda; H. Murakami

2006-01-01

195

Toughness anisotropy and damage behavior of plasma sprayed ZrO 2 thermal barrier coatings  

Microsoft Academic Search

This paper shows how the fracture properties of thermal barrier coatings (TBCs) can be determined for different crack orientations, and demonstrates the complex interaction between these properties during coating failure. Atmospheric plasma-sprayed ZrO2 coatings removed from the substrate were broken in three-point bending using micro-bending test equipment. Linear elastic fracture mechanics was used to calculate the toughness of a macroscopic

G. Thurn; G. A. Schneider; H.-A. Bahr; F. Aldinger

2000-01-01

196

Thermal cyclic behavior of air plasma sprayed thermal barrier coatings sprayed on stainless steel substrates  

Microsoft Academic Search

Thermal barrier coatings (TBCs) were deposited by an Air Plasma Spraying (APS) technique. The coating comprised of 93wt.% ZrO2 and 7wt.% Y2O3 (YSZ); CoNiCrAlY bond coat; and AISI 316L stainless steels substrate. Thermal cyclic lives of the TBC were determined as a function of bond coat surface roughness, thickness of the coating and the final deposition temperature. Two types of

A. Nusair Khan; J. Lu

2007-01-01

197

High-temperature deformation of plasma-sprayed ZrO 2 thermal barrier coatings  

Microsoft Academic Search

The high-temperature deformation of atmospheric plasma-sprayed ZrO2 thermal barrier coatings (TBCs) was investigated. Compression creep tests were performed at temperatures between 900 and 1300C at stresses between 1.8 and 80 MPa. During 100 h creep time a secondary creep region was not achieved. The creep behavior can be described by a power law. Besides the creep deformation, a shrinkage of

Gnter Thurn; Gerold A. Schneider; Fritz Aldinger

1997-01-01

198

Modelled and measured residual stresses in plasma sprayed thermal barrier coatings  

Microsoft Academic Search

Thermal barrier coatings consisting of a NiCrAlY bond coating and a 1.4 mm thick partially stabilised zirconia top coating were air plasma sprayed onto grit blasted nickel-base substrates. Two samples were produced using different amounts of external cooling during spraying of the top coatings. The residual stress profiles in the samples were measured after each manufacturing process step with a

Per Bengtsson; Christer Persson

1997-01-01

199

Sintering and creep processes in plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

During operation at elevated temperatures, sintering processes can significantly influence the mechanical properties of thermal\\u000a barrier coatings (TBCs) by increasing Youngs modulus and reducing strain tolerance. These changes of the mechanical response\\u000a of TBCs were investigated using free-standing plasma-sprayed TBCs in a thermomechanical analysis (TMA) facility. The time-dependent\\u000a change of Youngs modulus was determined in situ in a flexure mode

M. Ahrens; R. Vaen; D. Stver; S. Lampenscherf

2004-01-01

200

Radio frequency plasma power dependence of the moisture permeation barrier characteristics of Al{sub 2}O{sub 3} films deposited by remote plasma atomic layer deposition  

SciTech Connect

In the present study, we investigated the gas and moisture permeation barrier properties of Al{sub 2}O{sub 3} films deposited on polyethersulfone films (PES) by capacitively coupled plasma (CCP) type Remote Plasma Atomic Layer Deposition (RPALD) at Radio Frequency (RF) plasma powers ranging from 100 W to 400 W in 100 W increments using Trimethylaluminum [TMA, Al(CH{sub 3}){sub 3}] as the Al source and O{sub 2} plasma as the reactant. To study the gas and moisture permeation barrier properties of 100-nm-thick Al{sub 2}O{sub 3} at various plasma powers, the Water Vapor Transmission Rate (WVTR) was measured using an electrical Ca degradation test. WVTR decreased as plasma power increased with WVTR values for 400 W and 100 W of 2.6 10{sup ?4} gm{sup ?2}day{sup ?1} and 1.2 10{sup ?3} gm{sup ?2}day{sup ?1}, respectively. The trends for life time, Al-O and O-H bond, density, and stoichiometry were similar to that of WVTR with improvement associated with increasing plasma power. Further, among plasma power ranging from 100 W to 400 W, the highest power of 400 W resulted in the best moisture permeation barrier properties. This result was attributed to differences in volume and amount of ion and radical fluxes, to join the ALD process, generated by O{sub 2} plasma as the plasma power changed during ALD process, which was determined using a plasma diagnosis technique called the Floating Harmonic Method (FHM). Plasma diagnosis by FHM revealed an increase in ion flux with increasing plasma power. With respect to the ALD process, our results indicated that higher plasma power generated increased ion and radical flux compared with lower plasma power. Thus, a higher plasma power provides the best gas and moisture permeation barrier properties.

Jung, Hyunsoo [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of) [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Samsung Display Co. Ltd., Tangjeong, Chungcheongnam-Do 336-741 (Korea, Republic of); Choi, Hagyoung; Lee, Sanghun [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)] [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Jeon, Heeyoung [Department of Nano-scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)] [Department of Nano-scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Jeon, Hyeongtag [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of) [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Department of Nano-scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)

2013-11-07

201

The cold and atmospheric-pressure air surface barrier discharge plasma for large-area sterilization applications  

SciTech Connect

This letter reports a stable air surface barrier discharge device for large-area sterilization applications at room temperature. This design may result in visually uniform plasmas with the electrode area scaled up (or down) to the required size. A comparison for the survival rates of Escherichia coli from air, N{sub 2} and O{sub 2} surface barrier discharge plasmas is presented, and the air surface plasma consisting of strong filamentary discharges can efficiently kill Escherichia coli. Optical emission measurements indicate that reactive species such as O and OH generated in the room temperature air plasmas play a significant role in the sterilization process.

Wang Dacheng [School of Science, Changchun University of Science and Technology, Changchun, Jilin 130022 (China); Department of Aeronautics, Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); Zhao Di [Department of Aeronautics, Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); School of Photoelectrical Engineering, Changchun University of Science and Technology, Changchun, Jilin 130022 (China); Feng Kecheng [School of Science, Changchun University of Science and Technology, Changchun, Jilin 130022 (China); Zhang Xianhui [Department of Aeronautics, Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); Liu Dongping [School of Science, Changchun University of Science and Technology, Changchun, Jilin 130022 (China); Department of Aeronautics, Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); School of Physics and Materials Engineering, Dalian Nationalities University, Dalian 116600 (China); Yang Size [Department of Aeronautics, Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing 100080 (China)

2011-04-18

202

Co-Doping of Air Plasma-Sprayed Yttria-and Ceria-Stabilized Zirconia for Thermal Barrier Applications  

E-print Network

to that of the baseline coatings. I. Introduction VIRTUALLY every aircraft flying today uses thermal barrier coatingsCo-Doping of Air Plasma-Sprayed Yttria- and Ceria-Stabilized Zirconia for Thermal BarrierSZ coating. As-sprayed 2Yb/ 7.6YSZ and 2Yb/12CeSZ coatings had slightly lower thermal conductivity than

Trice, Rodney W.

203

Multi-scale Phenomena and Structures Observed in Fabrication of Thermal Barrier Coatings by Using Plasma Spraying  

Microsoft Academic Search

Thermal barrier coatings (TBC) fabricated by plasma spray can exhibit a wide range of microstructures due to differences in feedstock powders and spraying conditions. Since different microstructures naturally result in different thermal and mechanical properties and service life as thermal barrier coatings, it is of great importance to understand the relationship among the feedstock characteristics, spray conditions and the coating

Seiji Kuroda; Hideyuki Murakami; Makoto Watanabe; Kaita Itoh; Kentaro Shinoda; Xiancheng Zhang

2010-01-01

204

Stress distributions in plasma-sprayed thermal barrier coatings as a function of interface roughness and oxide scale thickness  

Microsoft Academic Search

During thermal cyclic loading, plasma-sprayed thermal barrier coatings (TBCs) often show failure within the top coat close to the interface. In all cases this results from crack propagation of pre-existing cracks near the bond coat (BC)top coat interface. Stresses developing on a microscopic scale near the BCTBC interface of plasma-sprayed thermal barrier coatings govern crack growth in an initial phase

M Ahrens; R Vaen; D Stver

2002-01-01

205

Plasma channel flows: Electro-fluid dynamic jets  

NASA Astrophysics Data System (ADS)

The present work builds on the success of a dielectric barrier discharge driven plasma channel by exploring an electrode configuration that directly actuates the bulk fluid minimizing jet impingement and viscosity related losses. Influence of several electrical and physical parameters including electrode materials are experimentally investigated. Results indicate significant variation of performance with these parameters and suggest that in comparison to surface dielectric barrier plasma actuator driven flows, at least an order of magnitude improvement in efficiency is possible. The jet produced from this plasma channel configuration allows greater versatility for applications in boundary layer flow control and internal flows.

Campbell, Nicholas S.; Roy, Subrata

2014-09-01

206

Development of barrier coatings for cellulosic-based materials by cold plasma methods  

NASA Astrophysics Data System (ADS)

Cellulose-based materials are ideal candidates for future industries that need to be based on environmentally safe technologies and renewable resources. Wood represents an important raw material and its application as construction material is well established. Cellophane is one of the most important cellulosic material and it is widely used as packaging material in the food industry. Outdoor exposure of wood causes a combination of physical and chemical degradation processes due to the combined effects of sunlight, moisture, fungi, and bacteria. Cold-plasma-induced surface modifications are an attractive way for tailoring the characteristics of lignocellulosic substrates to prevent weathering degradation. Plasma-polymerized hexamethyldisiloxane (PPHMDSO) was deposited onto wood surfaces to create water repellent characteristics. The presence of a crosslinked macromolecular structure was detected. The plasma coated samples exhibited very high water contact angle values indicating the existence of hydrophobic surfaces. Reflective and electromagnetic radiation-absorbent substances were incorporated with a high-molecular-weight polydimethylsiloxane polymer in liquid phase and deposited as thin layers on wood surfaces. The macromolecular films, containing the dispersed materials, were then converted into a three dimensional solid state network by exposure to a oxygen-plasma. It was demonstrated that both UV-absorbent and reflectant components incorporated into the plasma-generated PDMSO matrix protected the wood from weathering degradation. Reduced oxidation and less degradation was observed after simulated weathering. High water contact angle values indicated a strong hydrophobic character of the oxygen plasma-treated PDMSO-coated samples. Plasma-enhanced surface modifications and coatings were employed to create water-vapor barrier layers on cellophane substrate surfaces. HMDSO was selected as a plasma gas and oxygen was used to ablate amorphous regions. Oxygen plasma treated cellophane and oxygen plasma treated and PPHMDSO coated cellophane surfaces were comparatively analyzed and the corresponding surface wettability characteristics were evaluated. The plasma generated surface topographies controlled the morphology of the PPHMDSO layers. Higher temperature HMDSO plasma-state environments lead to insoluble, crosslinked layers. Continuous and pulsed Csb2Fsb6 plasmas were also used for surface modification and excellent surface fluorination was achieved under the pulsed plasma conditions.

Denes, Agnes Reka

207

Development of a dielectric barrier discharge enhanced plasma jet in atmospheric pressure air  

SciTech Connect

A plasma jet equipped with dielectric barrier discharge (DBD) is developed to generate diffuse air plasma with fairly large gap and cross sectional area. The diffuse air plasma has two discharge modes under different gap widths from the nozzle to the ground plate electrode. For large gap width, a diffuse plume fills the whole space between the nozzle and the plate electrode after coaxial DBD is ignited when the applied voltage reaches a certain value. Rather than diffuse plasma plume, a bright plasma column bridges the nozzle and the plate electrode with further increasing the applied voltage under small gap width. By optical and electrical measurement, results show that the macroscopically diffuse discharge in air is obtained by the superimposition of radially distributed streamers that appear at different cycles of the applied voltage, and the bright plasma column belongs to atmospheric pressure glow discharge. The molecular vibrational temperature and the gas temperature are given as functions of the peak value of the applied voltage.

Li Xuechen; Chang Yuanyuan; Jia Pengying [College of Physics Science and Technology, Hebei University, Baoding 071002 (China); Xu Longfei; Fang Tongzhen; Wang Long [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2012-09-15

208

Thermal shock resistance of air plasma sprayed thermal barrier coatings N A Fleck (1), A C F Cocks (2) and S Lampenscherf (3)  

E-print Network

1 Thermal shock resistance of air plasma sprayed thermal barrier coatings N A Fleck (1), A C F life of the thermal barrier coating, and also describes a test method for the measurement, 81739 Munich, Germany Summary The spallation resistance of an air plasma sprayed (APS) thermal barrier

Fleck, Norman A.

209

Dynamics of a potential barrier formed on the tail of a moving double layer in a collisionless plasma  

Microsoft Academic Search

A negative potential barrier on the low-potential side of a moving double layer gives rise to a current limitation in a collisionless plasma terminated by a positively biased cold collector plate in a Q machine. The double layer is produced in front of the plasma source and moves toward the collector during the limitation. When the double layer arrives at

S. Iizuka; P. Michelsen; J. J. Rasmussen; R. Schrittwieser; R. Hatakeyama; K. Saeki; N. Sato

1982-01-01

210

Failure of PVD/plasma sprayed thermal barrier coatings during thermal cycling  

SciTech Connect

ZrO{sub 2}7Y{sub 2}O{sub 3} plasma sprayed coatings (PS top coating) were applied on high temperature Ni-based alloys precoated by Physical Vapor Deposition with a thin, dense, stabilized zirconia coating (PVD bond coat). The PS coatings were applied by Atmospheric Plasma Spraying (APS) and Inert gas Plasma Spraying (IPS at 2 bar) for different substrate temperatures. The thermal barrier coatings (TBCs) were tested by furnace isothermal cycling and flame thermal cycling at maximum temperatures between 1,000 C and 1,150 C. The temperature gradients within the duplex PVD/PS thermal barrier coatings during the thermal cycling process were modeled using an unsteady heat transfer program. This modeling enables the authors to calculate the transient thermal strains and stresses which contribute to a better understanding of the failure mechanisms of the TBC during thermal cycling. They have also studied experimentally the adherence and failure modes of these coating systems during this high temperature testing. The TBC failure mechanism during thermal cycling is discussed in the light of coating transient stresses and substrate oxidation.

Teixeria, V.; Andritschky, M. [Univ. of Minho, Braga (Portugal); Gruhn, H.; Mallener, W.; Buchkremer, H.; Stoever, D. [Forschungszentrum Juelich GmbH (Germany)

1995-12-31

211

High-speed sterilization technique using dielectric barrier discharge plasmas in atmospheric humid air  

NASA Astrophysics Data System (ADS)

The inactivation of Bacillus atrophaeus spores by a dielectric barrier discharge (DBD) plasma produced by an ac voltage application of 1 kHz in atmospheric humid air was investigated in order to develop low-temperature, low-cost and high-speed plasma sterilization technique. The biological indicators covered with a Tyvek sheet were set just outside the DBD plasma region, where the air temperature and humidity as a discharge gas were precisely controlled by an environmental test chamber. The results show that the inactivation of Bacillus atrophaeus spores was found to be dependent strongly on the humidity, and was completed within 15 min at a relative humidity of 90 % and a temperature of 30 C. The treatment time for sterilization is shorter than those of conventional sterilization methods using ethylene oxide gas and dry heat treatment. It is considered that reactive species such as hydroxyl radicals that are effective for the inactivation of Bacillus atrophaeus spores could be produced by the DBD plasma in the humid air. Repetitive micro-pulsed discharge plasmas in the humid air will be applied for the sterilization experiment to enhance the sterilization efficiency.

Miyamae, M.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

2010-11-01

212

Process, properties, and environmental response of plasma sprayed thermal barrier coatings  

NASA Technical Reports Server (NTRS)

Experimental results are shown which demonstrate that the properties of plasma sprayed fully stabilized zirconia are strongly influenced by the process parameters. Properties of the coatings in the as-sprayed condition are shown to be additionally influenced by environmental exposure. This behavior is dependent on raw material considerations and processing conditions as well as exposure time and temperature. Process control methodology is described which can take into consideration these complex interactions and help to produce thermal barrier coatings in a cost effective way while meeting coating technical requirements.

Novak, Richard C.

1995-01-01

213

Process, properties and environmental response of plasma sprayed thermal barrier coatings  

NASA Technical Reports Server (NTRS)

Experimental results are shown which demonstrate that the properties of plasma sprayed fully stabilized zirconia are strongly influenced by the process parameters. Properties of the coatings in the as-sprayed condition are shown to be additionally influenced by environmental exposure. This behavior is dependent on raw material considerations and processing conditions as well as exposure time and temperature. Process control methodology is described which can take into consideration these complex interactions and help to produce thermal barrier coatings in a cost effective way while meeting coating technical requirements.

Novak, R. C.

1995-01-01

214

Sintering and creep behavior of plasma-sprayed zirconia- and hafnia-based thermal barrier coatings  

Microsoft Academic Search

The sintering and creep of plasma-sprayed ceramic thermal barrier coatings under high temperature conditions are complex phenomena. Changes in thermomechanical and thermophysical properties and in the stress response of these coating systems as a result of the sintering and creep processes are detrimental to coating thermal fatigue resistance and performance. In this paper, the sintering characteristics of ZrO28wt%Y2O3, ZrO225wt%CeO22.5wt%Y2O3, ZrO26w%NiO9wt%Y2O3,

Dongming Zhu; Robert A. Miller

1998-01-01

215

Process, properties, and environmental response of plasma sprayed thermal barrier coatings  

SciTech Connect

Experimental results are shown which demonstrate that the properties of plasma sprayed fully stabilized zirconia are strongly influenced by the process parameters. Properties of the coatings in the as-sprayed condition are shown to be additionally influenced by environmental exposure. This behavior is dependent on raw material considerations and processing conditions as well as exposure time and temperature. Process control methodology is described which can take into consideration these complex interactions and help to produce thermal barrier coatings in a cost effective way while meeting coating technical requirements.

Novak, R.C.

1995-10-01

216

Antimicrobial efficacy of two surface barrier discharges with air plasma against in vitro biofilms.  

PubMed

The treatment of infected wounds is one possible therapeutic aspect of plasma medicine. Chronic wounds are often associated with microbial biofilms which limit the efficacy of antiseptics. The present study investigates two different surface barrier discharges with air plasma to compare their efficacy against microbial biofilms with chlorhexidine digluconate solution (CHX) as representative of an important antibiofilm antiseptic. Pseudomonas aeruginosa SG81 and Staphylococcus epidermidis RP62A were cultivated on polycarbonate discs. The biofilms were treated for 30, 60, 150, 300 or 600 s with plasma or for 600 s with 0.1% CHX, respectively. After treatment, biofilms were dispensed by ultrasound and the antimicrobial effects were determined as difference in the number of the colony forming units by microbial culture. A high antimicrobial efficacy on biofilms of both plasma sources in comparison to CHX treatment was shown. The efficacy differs between the used strains and plasma sources. For illustration, the biofilms were examined under a scanning electron microscope before and after treatment. Additionally, cytotoxicity was determined by the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay with L929 mouse fibroblast cell line. The cell toxicity of the used plasma limits its applicability on human tissue to maximally 150 s. The emitted UV irradiance was measured to estimate whether UV could limit the application on human tissue at the given parameters. It was found that the UV emission is negligibly low. In conclusion, the results support the assumption that air plasma could be an option for therapy of chronic wounds. PMID:23894661

Matthes, Rutger; Bender, Claudia; Schlter, Rabea; Koban, Ina; Bussiahn, Ren; Reuter, Stephan; Lademann, Jrgen; Weltmann, Klaus-Dieter; Kramer, Axel

2013-01-01

217

Nanocomposite Lanthanum Zirconate Thermal Barrier Coating Deposited by Suspension Plasma Spray Process  

NASA Astrophysics Data System (ADS)

This work seeks to develop an innovative nanocomposite thermal barrier coating (TBC) exhibiting low thermal conductivity and high durability compared with that of current TBCs. To achieve this objective, nanosized lanthanum zirconate particles were selected for the topcoat of the TBC system, and a new processsuspension plasma spraywas employed to produce desirable microstructural features: the nanocomposite lanthanum zirconate TBC contains ultrafine splats and high volume porosity, for lower thermal conductivity, and better durability. The parameters of plasma spray experiment included two main variables: (i) spray distance varying from 40 to 80 mm and (ii) the concentration of suspension 20, 25, and 30 wt.%, respectively. The microstructure of obtained coatings was characterized with scanning electron microscope and x-ray diffraction. The porosity of coatings is in the range of 6-10%, and the single phase in the as-sprayed coatings was pyrochlore lanthanum zirconate.

Wang, Chaohui; Wang, You; Wang, Liang; Hao, Guangzhao; Sun, Xiaoguang; Shan, Fan; Zou, Zhiwei

2014-10-01

218

Hybrid Plasma-Sprayed Thermal Barrier Coatings Using Powder and Solution Precursor Feedstock  

NASA Astrophysics Data System (ADS)

A novel approach of hybridizing the conventional atmospheric plasma spraying (APS) technique with the solution precursor plasma spray (SPPS) route to achieve thermal barrier coatings (TBCs) with tailored configurations is presented. Such a hybrid process can be conveniently adopted for forming composite, multi-layered and graded coatings employing simultaneous and/or sequential feeding of solution precursor as well as powder feedstock, yielding distinct TBC microstructures that bear promise to further extend coating durability. TBC specimens generated using conventional APS technique, the SPPS method and through APS-SPPS hybrid processing have been comprehensively characterized for microstructure, phase constitution, hardness and thermal cycling life, and the results were compared to demonstrate the advantages that can ensue from hybrid processing.

Joshi, S. V.; Sivakumar, G.; Raghuveer, T.; Dusane, R. O.

2014-04-01

219

Development of dielectric barrier discharge plasma processing apparatus for mass spectrometry and thin film deposition.  

PubMed

Cost effective and a very simple dielectric barrier discharge plasma processing apparatus for thin film deposition and mass spectroscopic analysis of organic gas mixture has been described. The interesting features of the apparatus are the construction of the dielectric electrodes made of aluminum oxide or alumina (Al(2)O(3)) and glass and the generation of high ignition voltage from the spark plug transformer taken from car. Metal capacitor is introduced in between ground and oscilloscope to measure the executing power during the discharge and the average electron density in the plasma region. The organic polymer films have been deposited on Si (100) substrate using several organic gas compositions. The experimental setup provides a unique drainage system from the reaction chamber controlled by a membrane pump to suck out and remove the poisonous gases or residuals (cyanogens, H-CN, CH(x)NH(2), etc.) which have been produced during the discharge of CH(4)N(2) mixture. PMID:17672789

Majumdar, Abhijit; Hippler, Rainer

2007-07-01

220

Time-resolved Schlieren imaging of electrohydrodynamic interaction induced by a dielectric barrier discharge  

NASA Astrophysics Data System (ADS)

Commercially available transparent conducting electrodes provide an inexpensive way to investigate different configurations of dielectric barrier discharges (DBD), including so called plasma actuators. Although operation of atmospheric DBDs in a diffuse mode has been reported, they ares limited to very restricted range of operational parameters including the gas flow rate. In addition to diffuse and filamentary modes, there exists a patterned mode which like the diffuse one, is also severely limited by operational constraints. In the experiment, spatial and temporal evolution of both flow and plasma fields in parallel, tilted plate and asymmetric plasma actuator geometries are analyzed by the Schlieren method, and using gated intensified CCD.

Nourgostar, Sirous; Hershkowitz, Noah

2009-11-01

221

Pellet injection into H-mode ITER plasma with the presence of internal transport barriers  

NASA Astrophysics Data System (ADS)

The impacts of pellet injection into ITER type-1 ELMy H-mode plasma with the presence of internal transport barriers (ITBs) are investigated using self-consistent core-edge simulations of 1.5D BALDUR integrated predictive modeling code. In these simulations, the plasma core transport is predicted using a combination of a semi-empirical Mixed B/gB anomalous transport model, which can self-consistently predict the formation of ITBs, and the NCLASS neoclassical model. For simplicity, it is assumed that toroidal velocity for ? E B calculation is proportional to local ion temperature. In addition, the boundary conditions are predicted using the pedestal temperature model based on magnetic and flow shear stabilization width scaling; while the density of each plasma species, including both hydrogenic and impurity species, at the boundary are assumed to be a large fraction of its line averaged density. For the pellet's behaviors in the hot plasma, the Neutral Gas Shielding (NGS) model by Milora-Foster is used. It was found that the injection of pellet could result in further improvement of fusion performance from that of the formation of ITB. However, the impact of pellet injection is quite complicated. It is also found that the pellets cannot penetrate into a deep core of the plasma. The injection of the pellet results in a formation of density peak in the region close to the plasma edge. The injection of pellet can result in an improved nuclear fusion performance depending on the properties of pellet (i.e., increase up to 5% with a speed of 1 km/s and radius of 2 mm). A sensitivity analysis is carried out to determine the impact of pellet parameters, which are: the pellet radius, the pellet velocity, and the frequency of injection. The increase in the pellet radius and frequency were found to greatly improve the performance and effectiveness of fuelling. However, changing the velocity is observed to exert small impact.

Leekhaphan, P.; Onjun, T.

2011-04-01

222

Thermal barrier coatings on turbine blades by plasma spraying with improved cooling  

SciTech Connect

Turbine blades were coated with a thermal barrier coating system consisting of an MCrAlY bond coat about 100 [mu]m thick deposited by Low-Pressure Plasma Spraying (LPPS) and a 300 [mu]m thick ZrO[sub 2]-7 wt.% Y[sub 2]O[sub 3] top coat. The latter was manufactured by both Atmosphere and Temperature Controlled Spraying (ATCS) and Air Plasma Spraying (APS) using internal air cooling through the cooling holes of the turbine blades. Coated blades were submitted to thermal cycling tests in a burner rig with hot gas temperature of 1,485 C. In the case of ATCS coated blades the number of cycles until the first spallation at the leading edge of the blade was between 350 and 2,400. The number of cycles of the thermal barrier coatings sprayed with internal cooling was between 1,200 and 1,800. Furnace cycling tests were also carried out with ATCS coated blades at temperatures of 1,100 and 1,200 C. The results of thermal cycle tests and the investigations of the microstructure are discussed.

Cosack, T.; Schneiderbanger, S. (MTU Motoren- und Turbinen-Union, Munchen (Germany)); Pawlowski, L.; Sturlese, S. (CSM Centro Sviluppo Materiali, Pergine di Valsugana (Italy))

1994-01-01

223

Physical and plasmachemical aspects of diffuse coplanar barrier discharge as a novel atmospheric-pressure plasma source  

NASA Astrophysics Data System (ADS)

Collaborating Czech and Slovakian university teams have recently developed an innovative plasma source, the so-called Diffuse Coplanar Surface Barrier Discharge (DCSBD), which has the potential to move a step closer to the industry requirement for in-line treatment of low-added-value materials using a highly-nonequlibrium ambient air plasma (Simor et al. 2002, The idea is to generate a thin (on the order of 0.1 mm) layer of highly-nonequlibrium plasma with a high power density (up to 100 W/cm^3) in the immediate vicinity of the treated surface and bring it into a close contact with the treated surface. Comparing to atmospheric-pressure glow discharge, volume dielectric barrier discharge, and plasma jet plasmas, such a diffuse plasma layer is believed to provide substantial advantages in energy consumption, exposure time, and technical simplicity. A brief outline of physical mechanism and basic properties of DCSBD will given using the results of emission spectroscopy, high-speed camera, and spatially resolved cross-correlation spectroscopy studies. The presentation will review also a current state of the art in in-line plasma treatment of low-cost materials and opportunities for the use of the so-called Diffuse Coplanar Surface Dielectric Barrier Discharge (DCSBD). The results obtained on the ambient air plasma treatments of textile, paper, wood, and glass illustrate that DCSBD offers outstanding performance with extremely low energy consumption for large area, uniform surface modifications of materials under continuous process conditions.

Cernak, M.; Kovacik, D.; Zahoranova, A.; Rahel, J.

2008-07-01

224

QUIESCENT DOUBLE BARRIER H-MODE PLASMAS IN THE DIII-D TOKAMAK  

SciTech Connect

High confinement (H-mode) operation is the choice for next-step tokamak devices based either on conventional or advanced tokamak physics. This choice, however, comes at a significant cost for both the conventional and advanced tokamaks because of the effects of edge localized modes (ELMs). ELMs can produce significant erosion in the divertor and can affect the beta limit and reduced core transport regions needed for advanced tokamak operation. Experimental results from DIII-D [J.L. Luxon, et al., Plasma Phys. and Contr. Nucl. Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987) Vol. I, p. 159] this year have demonstrated a new operating regime, the quiescent H-mode regime, which solves these problems. We have achieved quiescent H-mode operation which is ELM-free and yet has good density and impurity control. In addition, we have demonstrated that an internal transport barrier can be produced and maintained inside the H-mode edge barrier for long periods of time (>3.5 seconds or >25 energy confinement times {tau}{sub E}), yielding a quiescent double barrier regime. By slowly ramping the input power, we have achieved {beta}{sub N} H{sub 89} = 7 for up to 5 times the {tau}{sub E} of 150 ms. The {beta}{sub N} H{sub 89} values of 7 substantially exceed the value of 4 routinely achieved in standard ELMing H-mode. The key factors in creating the quiescent H-mode operation are neutral beam injection in the direction opposite to the plasma current (counter injection) plus cryopumping to reduce the density. Density and impurity control in the quiescent H-mode is possible because of the presence of an edge magnetic hydrodynamic (MHD) oscillation, the edge harmonic oscillation, which enhances the edge particle transport while leaving the energy transport unaffected.

K.H. BURRELL; M.E. AUSTIN; D.P. BRENNAN; J.C. DeBOO; E.J. DOYLE; C. FENZI; C. FUCHS; P. GOHIL; R.J. GROEBNER; L.L. LAO; T.C. LUCE; M.A. MAKOWSKI; G.R. McKEE; R.A. MOYER; C.C. PETTY; M. PORKOLAB; C.L.RETTIG; T.L. RHODES; J.C. ROST; B.W. STALLARD; E.J. STRAIT; E.J. SYNAKOWSKI; M.R. WADE; J.G. WATKINS; W.P. WEST

2000-11-01

225

Columnar-Structured Mg-Al-Spinel Thermal Barrier Coatings (TBCs) by Suspension Plasma Spraying (SPS)  

NASA Astrophysics Data System (ADS)

The suspension plasma spraying (SPS) process has been developed to permit the feeding of sub-micrometer-sized powder into the plasma plume. In contrast to electron beam-physical vapor deposition and plasma spray-physical vapor deposition, SPS enables the cost-efficient deposition of columnar-structured coatings. Due to their strain tolerance, these coatings play an important role in the field of thermal barrier coatings (TBCs). In addition to the cost-efficient process, attention was turned to the TBC material. Nowadays, yttria partially stabilized zirconia (YSZ) is used as standard TBC material. However, its long-term application at temperatures higher than 1200 C is problematic. At these high temperatures, phase transitions and sintering effects lead to the degradation of the TBC system. To overcome those deficits of YSZ, Mg-Al-spinel was chosen as TBC material. Even though it has a lower melting point (~2135 C) and a higher thermal conductivity (~2.5 W/m/K) than YSZ, Mg-Al-spinel provides phase stability at high temperatures in contrast to YSZ. The Mg-Al-spinel deposition by SPS resulted in columnar-structured coatings, which have been tested for their thermal cycling lifetime. Furthermore, the influence of substrate cooling during the spraying process on thermal cycling behavior, phase composition, and stoichiometry of the Mg-Al-spinel has been investigated.

Schlegel, N.; Ebert, S.; Mauer, G.; Vaen, R.

2014-08-01

226

Odor Removal Characteristics of Barrier-Type Packed-Bed Nonthermal Plasma Reactor  

NASA Astrophysics Data System (ADS)

Odor control has gained importance for ensuring a comfortable living environment. In this paper, the authors report the experimental results of a study of the detailed characteristics of a barrier-type packed-bed nonthermal plasma reactor used for odor control. This plasma reactor has been widely used for volatile organic compound (VOC) decomposition and NOx reduction. The reactor is energized by a low-cost 60 Hz AC power supply. Removal efficiency and the concentrations of byproducts are studied under various experimental conditions. The complete decomposition of the main odor component, namely, NH3, is obtained with minimal reaction byproduct formation (maximum N2O concentration, 10 ppm) in a dry environment. The decomposition is deteriorated by the addition of moisture. The minimum residence time is determined for the complete removal of NH3 in the case of the packed-bed plasma reactor. The pellet diameter has little effect on the removal tendency, and the reactor performed better than a silent corona. Mixing another odor component such as CH3CHO into the gas stream has little effect on the NH3 removal efficiency.

Okubo, Masaaki; Kametaka, Hidetaka; Yoshida, Keiichiro; Yamamoto, Toshiaki

2007-08-01

227

Spectroscopic diagnostics of barrier-discharge plasma in mixtures of cadmium diiodide vapor with gases  

NASA Astrophysics Data System (ADS)

The spectral characteristics of the emission of atmospheric-pressure gas-discharge plasma in mixtures of cadmium diiodide vapor with gases (Ne, Ar, Kr, Xe, and N2) were investigated along with the time characteristics of the voltage and current. The gas-discharge plasma was produced and excited by a barrier discharge at a repetition rate of sine voltage pulses of up to 140 kHz. The discharge emission was analyzed in the spectral range 200 900 nm with a high resolution (0.05 nm). Radiation from exciplex CdI(B-X) molecules and excimer I2* molecules was revealed, as well as the atomic lines of cadmium, iodine, and inert gases. In a mixture with xenon, radiation from exciplex molecules XeI(B-X, B-A) was also found. This radiation prevailed in the spectra at mixture temperatures up to 150C. The further increase of the temperature leads to the prevalence of the CdI(B-X) radiation. It was found that the most intense CdI(B-X) radiation is observed in mixtures CdI2/Xe(N2)/Ne. Regularities in the spectral characteristics of the emission of the gas-discharge plasma are discussed.

Guivan, M. M.; Malinin, A. N.

2007-02-01

228

Efficient barrier for charge injection in polyethylene by silver nanoparticles/plasma polymer stack  

NASA Astrophysics Data System (ADS)

Charge injection from a metal/insulator contact is a process promoting the formation of space charge in polymeric insulation largely used in thick layers in high voltage equipment. The internal charge perturbs the field distribution and can lead to catastrophic failure either through its electrostatic effects or through energetic processes initiated under charge recombination and/or hot electrons effects. Injection is still ill-described in polymeric insulation due to the complexity of the contact between the polymer chains and the electrodes. Barrier heights derived from the metal work function and the polymer electronic affinity do not provide a good description of the measurements [Taleb et al., IEEE Trans. Dielectr. Electr. Insul. 20, 311-320 (2013)]. Considering the difficulty to describe the contact properties and the need to prevent charge injection in polymers for high voltage applications, we developed an alternative approach by tailoring the interface properties by the silver nanoparticles (AgNPs)/plasma polymer stack, deposited on the polymer film. Due to their small size, the AgNPs, covered by a very thin film of plasma polymer, act as deep traps for the injected charges thereby stabilizing the interface from the point of view of charge injection. After a quick description of the method for elaborating the nanostructured layer near the contact, it is demonstrated how the AgNPs/plasma polymer stack effectively prevents, in a spectacular way, the formation of bulk space charge.

Milliere, L.; Makasheva, K.; Laurent, C.; Despax, B.; Teyssedre, G.

2014-09-01

229

Improving Atmospheric Plasma Spraying of Zirconate Thermal Barrier Coatings Based on Particle Diagnostics  

NASA Astrophysics Data System (ADS)

Lanthanum zirconate (La2Zr2O7) has been proposed as a promising material for thermal barrier coatings. During atmospheric plasma spraying (APS) of La2Zr2O7 a considerable amount of La2O3 can evaporate in the plasma flame, resulting in a non-stoichiometric coating. As indicated in the phase diagram of the La2O3-ZrO2 system, in the composition range of pyrochlore structure, the stoichiometric La2Zr2O7 has the highest melting point and other compositions are eutectic. APS experiments were performed with a TriplexPro-200 plasma torch at different power levels to achieve different degrees of evaporation and thus stoichiometry. For comparison, some investigations on gadolinium zirconate (Gd2Zr2O7) were included, which is less prone to evaporation and formation of non-stoichiometry. Particle temperature distributions were measured by the DPV-2000 diagnostic system. In these distributions, characteristic peaks were detected at specific torch input powers indicating evaporation and solidification processes. Based on this, process parameters can be defined to provide stoichiometric coatings that show good thermal cycling performance.

Mauer, Georg; Sebold, Doris; Vaen, Robert; Stver, Detlev

2012-06-01

230

Synthesis of Polystyrene Thin Films by Means of an Atmospheric-Pressure Plasma Torch and a Dielectric Barrier Discharge  

Microsoft Academic Search

In this paper, the deposition and characterization of plasma-polymerized polystyrene (pp-PS) using PECVD under atmospheric pressure on a variety of substrates was investigated. An atmospheric RF plasma torch and an HF dielectric-barrier-discharge (DBD) system were used to deposit thin pp-PS coatings on PTFE, HDPE, stainless steel, glass, and silicon wafer. The styrene vapor was carried by Ar or He. The

Delphine Merche; Claude Poleunis; Patrick Bertrand; Michele Sferrazza; Franois Reniers

2009-01-01

231

Mechanical Properties of Plasma-Sprayed ZrO2-8 wt% Y2O3 Thermal Barrier Coatings  

NASA Technical Reports Server (NTRS)

Mechanical behavior of free standing, plasma-sprayed ZrO2-8 wt% Y2O3 thermal barrier coatings, including strength, fracture toughness, fatigue, constitutive relation, elastic modulus, and directionality, has been determined under various loading-specimen configurations. This report presents and describes a summary of mechanical properties of the plasma-sprayed coating material to provide them as a design database.

Choi, Sung R.; Zhu, Dongming; Miller, Robert A.

2004-01-01

232

Characterization and Application of a Planar Radio - Inductively-Coupled Plasma Source for the Production of Barrier Coatings  

Microsoft Academic Search

A planar radio-frequency (rf) inductively-coupled plasma (ICP) source is used to produce fluorocarbon discharges (CF_4\\/Ar) to fluorinate the surface of high-density polyethylene (HDPE). Using this system, concurrent studies of discharge characteristics, permeation properties of treated polymers and polymer surface characteristics are conducted to advance the use of plasma-fluorinated polymer surfaces as a barrier layer for automotive applications. Langmuir probes are

Leonard Joseph Mahoney

1994-01-01

233

Improvement of EB-PVD thermal barrier coatings by treatments of a vacuum plasma-sprayed bond coat  

Microsoft Academic Search

The lifetime of electron beam physical vapor deposited (EB-PVD) thermal barrier coating (TBC) systems with conventional 7 YSZ ceramic top layers was investigated in 1h thermal-cyclic testing at 1100C. The single crystal alloy CMSX-4 and the polycrystalline IN 100 alloy that had been coated with a vacuum plasma-sprayed MCrAlY bond coat were chosen as substrate materials. A fully plasma-sprayed TBC

U. Schulz; O. Bernardi; A. Ebach-Stahl; R. Vassen; D. Sebold

2008-01-01

234

Processing-structure-property relationships of thermal barrier coatings deposited using the solution precursor plasma spray process  

Microsoft Academic Search

This research is intended to develop a novel process, solution-precursor plasma-spray (SPPS), for the deposition of highly durable thermal barrier coatings (TBCs). In the SPPS process a solution precursor feedstock, that results in ZrO2-7 wt% Y2O3 ceramic, is injected into the plasma jet and the coating is deposited on a metal substrate. The formed coating has the following novel microstructural

Liangde Xie

2003-01-01

235

Low hydrogen content in trimethylsilane-based dielectric barriers deposited by inductively coupled plasma  

NASA Astrophysics Data System (ADS)

Dielectric barriers of trimethylsilane-based hydrogenated amorphous silicon carbide (a-SiCx):H for damascene metalization were synthesized by inductively coupled plasma (ICP) chemical vapor deposition methods. The high ionization efficiency from ICP, resulting in a-SiCx:H films that contain only a little hydrogen, is explored as a major mechanism that yields such a film not only with a high breakdown field of 3.7 MV/cm and a low leakage current <6.0 x10-10 A/cm2 (at 1.0 MV/cm), but also with a low stress (-5 MPa) and high hardness (11 GPa). Additionally, the dielectric constant of the a-SiCx:H films is maintained below 4.2.

Shieh, Jia-Min; Tsai, Kou-Chiang; Dai, Bau-Tong

2002-08-01

236

Pattern formation and dynamics of plasma filaments in dielectric barrier discharges  

NASA Astrophysics Data System (ADS)

Dielectric barrier discharges (DBDs) operating in a transient glow discharge regime offer a large variety of self-organized filamentary static or dynamical structures and constitute an excellent physical system for the study of nonlinear dynamics and pattern formation. The plasma filaments of DBDs can exhibit particle-like behavior, with motion, generation, annihilation, and scattering as well as collective effects leading to self-organized structures (hexagons, stripes, concentric rings, spirals, etc) that are typical of reaction–diffusion systems. The purpose of this paper is to analyze the detailed physics of pattern formation in DBDs on the basis of numerical fluid simulations and experiments in order to provide a deeper understanding of the nonlinear mechanisms responsible for the self-organization and dynamics of filaments.

Callegari, T.; Bernecker, B.; Boeuf, J. P.

2014-10-01

237

Effect of Thermal Exposure on Mechanical Properties of a Plasma-Sprayed Nanostructured Thermal Barrier Coating  

NASA Astrophysics Data System (ADS)

A nanostructured thermal barrier coating (TBC) was deposited by air plasma spraying. The effect of microstructural evolution on nano-hardness and Young's modulus has been investigated by nanoindentation technique after exposure at 1200 C in air for different times. The results showed that the sintering process of nanostructured TBC at 1200 C was divided into two stages. TBC completely kept the nanostructure with the grain size <100 nm at the first stage of 10 h thermal exposure. The nanostructure was lost gradually at the second stage from 10 to 200 h thermal exposure. During the first stage, nano-hardness and Young's modulus increased rapidly for TBC densification, and Weibull bimodal distribution of both Young's modulus and nano-hardness disappeared as grain grew and most microcracks were healed. The structure of TBC did not change basically, and nano-hardness and Young's modulus increased slightly at the second stage.

Wu, Zilong; Ni, Liyong; Yu, Qinghe; Zhou, Chungen

2012-01-01

238

Some observations on plasma-assisted combustion enhancement using dielectric barrier discharges  

NASA Astrophysics Data System (ADS)

We explore an effective way to promote propane combustion by applying a plasma discharge for efficiency enhancement. A coaxial-cylinder, dielectric barrier discharge is used to activate propane and air before they are mixed with each other and ignited for combustion. The characteristics of the combustion flame are well studied and evaluated by varying various operational parameters. It is found that the combustion process can be enhanced by applying a plasma on either the propane or air stream, and the combustion stability is found to be somewhat sensitive to the lean burning conditions and confined to a relatively narrow operating window. The temperature and spectrum of the flame in the main combustion zone are investigated with a 4 W plasma in the on or off state. The main components are identified, and the possible physical and chemical reaction mechanisms are discussed. A comparative analysis of these spectra and temperatures obtained in the main flame suggests that the energy generated from the 4 W plasma is partially used to heat the reaction gases in the flame, and another part of the energy is used to increase the luminosity, especially for activation of air. We also observe that combustion of high flow rate propane and/or air requires more discharge energy density under certain conditions. A comparison of combustion enhancement through different activation methods in flame blowout tests shows that reactive species derived from activation of air play a more critical role in the blowout limit of propane combustion flame than those generated by activation of propane at low equivalence ratio and propane flow.

Tang, Jie; Zhao, Wei; Duan, Yixiang

2011-08-01

239

A multiscale constitutive model for the sintering of an air-plasma sprayed thermal barrier coating, and its response under hot isostatic pressing  

E-print Network

-plasma-sprayed, thermal barrier coating, and is used to make predictions of microstructure evolution under free sintering for experimental validation of the micromechanical model. Keywords: sintering, thermal barrier coatings coatings (TBCs) are used extensively as protective thermal barriers of creep resistant stationary parts

Fleck, Norman A.

240

Quiescent Double Barrier H-Mode Plasmas in the DIII-D Tokamak  

SciTech Connect

High confinement (H-mode) operation is the choice for next-step tokamak devices based either on conventional or advanced tokamak physics. This choice, however, comes at a significant cost for both the conventional and advanced tokamaks because of the effects of edge localized modes (ELMs). ELMs can produce significant erosion in the divertor and can affect the beta limit and reduced core transport regions needed for advanced tokamak operation. Experimental results from DIII-D this year have demonstrated a new operating regime, the quiescent H-mode regime, which solves these problems. We have achieved quiescent H-mode operation which is ELM-free and yet has good density and impurity control. In addition, we have demonstrated that an internal transport barrier can be produced and maintained inside the H-mode edge barrier for long periods of time (>3.5 seconds or >25 energy confinement times {tau}{sub E}), yielding a quiescent double barrier regime. By slowly ramping the input power, we have achieved {beta}{sub N} H89 = 7 for up to 5 times the {tau}{sub E} of 150 ms. The {beta}{sub N} H89 values of 7 substantially exceed the value of 4 routinely achieved in standard ELMing H-mode. The key factors in creating the quiescent H-mode operation are neutral beam injection in the direction opposite to the plasma current (counter injection) plus cryopumping to reduce the density. Density and impurity control in the quiescent H-mode is possible because of the presence of an edge magnetic hydrodynamic (MHD) oscillation, the edge harmonic oscillation, which enhances the edge particle transport while leaving the energy transport unaffected.

Burrell, K H; Austin, M E; Brennan, D P; DeBoo, J C; Doyle, E J; Fenzi, C; Fuchs, C; Gohil, P; Greenfield, C M; Groebner, R J; Lao, L L; Luce, T C; Makowski, M A; McKee, G R; Moyer, R A; Petty, C C; Porkolab, M; Rettig, C L; Rhodes, T L; Rost, J C; Stallard, B W; Strait, E J; Synakowski, E J; Wade, M R; Watkins, J G; West, W P

2000-11-01

241

Effect of Sintering on Mechanical and Physical Properties of Plasma-Sprayed Thermal Barrier Coatings  

NASA Technical Reports Server (NTRS)

The effect of sintering on mechanical and physical properties of free-standing plasma-sprayed ZrO2-8 wt% Y2O3 thermal barrier coatings (TBCs) was determined by annealing them at 1316 C in air. Mechanical and physical properties of the TBCs, including strength, modes I and II fracture toughness, elastic modulus, Poisson s response, density, microhardness, fractography, and phase stability, were determined at ambient temperature as a function of annealing time ranging from 0 to 500 h. All mechanical and physical properties, except for the amount of monoclinic phase, increased significantly in 5 to 100 h and then reached a plateau above 100 h. Annealing resulted in healing of microcracks and pores and in grain growth, accompanying densification of the TBC s body due to the sintering effect. However, an inevitable adverse effect also occurred such that the desired lower thermal conductivity and good expansivity, which makes the TBCs unique in thermal barrier applications, were degraded upon annealing. A model was proposed to assess and quantify all the property variables in response to annealing in a normalized scheme. Directionality of as-sprayed TBCs appeared to have an insignificant effect on their properties, as determined via fracture toughness, microhardness, and elastic modulus measurements.

Choi, Sung R.; Zhu, Dong-Ming; Miller, Robert A.

2004-01-01

242

Pellet injection into H-mode ITER plasma with the presence of internal transport barriers  

SciTech Connect

The impacts of pellet injection into ITER type-1 ELMy H-mode plasma with the presence of internal transport barriers (ITBs) are investigated using self-consistent core-edge simulations of 1.5D BALDUR integrated predictive modeling code. In these simulations, the plasma core transport is predicted using a combination of a semi-empirical Mixed B/gB anomalous transport model, which can self-consistently predict the formation of ITBs, and the NCLASS neoclassical model. For simplicity, it is assumed that toroidal velocity for {omega}{sub E Multiplication-Sign B} calculation is proportional to local ion temperature. In addition, the boundary conditions are predicted using the pedestal temperature model based on magnetic and flow shear stabilization width scaling; while the density of each plasma species, including both hydrogenic and impurity species, at the boundary are assumed to be a large fraction of its line averaged density. For the pellet's behaviors in the hot plasma, the Neutral Gas Shielding (NGS) model by Milora-Foster is used. It was found that the injection of pellet could result in further improvement of fusion performance from that of the formation of ITB. However, the impact of pellet injection is quite complicated. It is also found that the pellets cannot penetrate into a deep core of the plasma. The injection of the pellet results in a formation of density peak in the region close to the plasma edge. The injection of pellet can result in an improved nuclear fusion performance depending on the properties of pellet (i.e., increase up to 5% with a speed of 1 km/s and radius of 2 mm). A sensitivity analysis is carried out to determine the impact of pellet parameters, which are: the pellet radius, the pellet velocity, and the frequency of injection. The increase in the pellet radius and frequency were found to greatly improve the performance and effectiveness of fuelling. However, changing the velocity is observed to exert small impact.

Leekhaphan, P. [Thammasat University, School of Bio-Chemical Engineering and Technology, Sirindhorn International Institute of Technology (Thailand); Onjun, T. [Thammasat University, School of Manufacturing Systems and Mechanical Engineering, Sirindhorn International Institute of Technology (Thailand)

2011-04-15

243

The effect of thermal aging on the thermal conductivity of plasma sprayed and EB-PVD thermal barrier coatings  

Microsoft Academic Search

Thermal barrier coatings (TBCs) applied to the hot gas components of turbine engines lead to enhanced fuel efficiency and component reliability. Understanding the mechanisms which control the thermal transport behavior of the TBCs is of primary importance. Electron beam-physical vapor deposition (EV-PVD) and air plasma spraying (APS) are the two most commonly used coating techniques. These techniques produce coatings with

R. B. Dinwiddie; S. C. Beecher; W. D. Porter; B. A. Nagaraj

1996-01-01

244

Development of dielectric barrier discharge plasma processing apparatus for mass spectrometry and thin film deposition  

SciTech Connect

Cost effective and a very simple dielectric barrier discharge plasma processing apparatus for thin film deposition and mass spectroscopic analysis of organic gas mixture has been described. The interesting features of the apparatus are the construction of the dielectric electrodes made of aluminum oxide or alumina (Al{sub 2}O{sub 3}) and glass and the generation of high ignition voltage from the spark plug transformer taken from car. Metal capacitor is introduced in between ground and oscilloscope to measure the executing power during the discharge and the average electron density in the plasma region. The organic polymer films have been deposited on Si (100) substrate using several organic gas compositions. The experimental setup provides a unique drainage system from the reaction chamber controlled by a membrane pump to suck out and remove the poisonous gases or residuals (cyanogens, H-CN, CH{sub x}NH{sub 2}, etc.) which have been produced during the discharge of CH{sub 4}/N{sub 2} mixture.

Majumdar, Abhijit; Hippler, Rainer [Institut fuer Physik, Ernst-Moritz-Arndt-Universitaet Greifswald, Felix-Hausdorff-Strasse 6, 17489 Greifswald (Germany)

2007-07-15

245

Isothermal Oxidation Behavior of Supersonic Atmospheric Plasma-Sprayed Thermal Barrier Coating System  

NASA Astrophysics Data System (ADS)

In this work, Y2O3 stabilized zirconia-based thermal barrier coatings (TBCs) were deposited by conventional atmospheric plasma spraying (APS) and high efficiency supersonic atmospheric plasma spraying (SAPS), respectively. The effect of Al2O3 layer stability on the isothermal growth behavior of thermally grown oxides (TGOs) was studied. The results revealed that the Al2O3 layer experienced a three-stage change process, i.e., (1) instantaneous growth stage, (2) steady-state growth stage, and (3) depletion stage. The thickness of Al2O3 scale was proved to be an important factor for the growth rate of TGOs. The SAPS-TBCs exhibited a higher Al2O3 stability and better oxidation resistance as compared with the APS-TBCs. Additionally, it was found that inner oxides, especially nucleated on the top of the crest, continually grew and swallowed the previously formed Al2O3 layer, leading to the granulation and disappearance of continuous Al2O3 scale, which was finally replaced by the mixed oxides and spinel.

Bai, Yu; Ding, Chunhua; Li, Hongqiang; Han, Zhihai; Ding, Bingjun; Wang, Tiejun; Yu, Lie

2013-10-01

246

Neutron and X-ray diffraction of plasma-sprayed zirconia-yttria thermal barrier coatings  

NASA Technical Reports Server (NTRS)

ZrO2-7.8mol. pct. YO1.5, a fused powder, and ZrO2-8.7mol. pct. YO1.5, a prereacted powder, were plasma-sprayed onto steel substrates. Neutron diffraction and X-ray diffraction of the as-received powder, the powder plasma sprayed into water, as-sprayed coatings, and coatings heat-treated for 10 and 100 h were carried out to study phase transformations and ordering of the oxygen ions on the oxygen sublattice. The as-received fused powder has a much lower monoclinic percentage than does the pre-reacted powder, this resulting in a much lower monoclinic percentage in the coating. Heat treatment increases the percentages of the cubic and monoclinic phases, while decreasing the tetragonal content. An ordered tetragonal phase is detected by the presence of extra neutron diffraction peaks. These phase transformations and ordering will result in volume changes. The implications of these transformations on the performance of partially stabilized zirconia thermal barrier coatings is discussed.

Shankar, N. R.; Herman, H.; Singhal, S. P.; Berndt, C. C.

1984-01-01

247

Thermal cycling behavior of plasma-sprayed thermal barrier coatings with various MCrAlX bond coats  

Microsoft Academic Search

The influence of bond coat composition on the spallation resistance of plasma-sprayed thermal barrier coatings (TBCs) on single-crystal\\u000a Ren N5 substrates was assessed by furnace thermal cycle testing of TBCs with various vacuum plasma spray (VPS) or air plasma-spray\\u000a (APS) MCrAlX (M=Ni and\\/or Co; and X=Y, Hf, and\\/or Si) bond coats. The TBC specimens with VPS bond coats were fabricated

J. A. Haynes; M. K. Ferber; W. D. Porter

2000-01-01

248

Moisture barrier properties of thin organic-inorganic multilayers prepared by plasma-enhanced ALD and CVD in one reactor.  

PubMed

A widely used application of the atomic layer deposition (ALD) and chemical vapour deposition (CVD) methods is the preparation of permeation barrier layers against water vapour. Especially in the field of organic electronics, these films are highly demanded as such devices are very sensitive to moisture and oxygen. In this work, multilayers of aluminium oxide (AlO x ) and plasma polymer (PP) were coated on polyethylene naphthalate substrates by plasma-enhanced ALD and plasma-enhanced CVD at 80" in the same reactor, respectively. As precursor, trimethylaluminium was used together with oxygen radicals in order to prepare AlO x , and benzene served as precursor to deposit the PP. This hybrid structure allows the decoupling of defects between the single AlO x layers and extends the permeation path for water molecules towards the entire barrier film. Furthermore, the combination of two plasma techniques in a single reactor system enables short process times without vacuum breaks. Single aluminium oxide films by plasma-enhanced ALD were compared to thermally grown layers and showed a significantly better barrier performance. The water vapour transmission rate (WVTR) was determined by means of electrical calcium tests. For a multilayer with 3.5 dyads of 25-nm AlO x and 125-nm PP, a WVTR of 1.2 10 (-3) gm (-2) d (-1) at 60" and 90% relative humidity could be observed. PMID:24936155

Blow, Tim; Gargouri, Hassan; Siebert, Mirko; Rudolph, Rolf; Johannes, Hans-Hermann; Kowalsky, Wolfgang

2014-01-01

249

Moisture barrier properties of thin organic-inorganic multilayers prepared by plasma-enhanced ALD and CVD in one reactor  

PubMed Central

A widely used application of the atomic layer deposition (ALD) and chemical vapour deposition (CVD) methods is the preparation of permeation barrier layers against water vapour. Especially in the field of organic electronics, these films are highly demanded as such devices are very sensitive to moisture and oxygen. In this work, multilayers of aluminium oxide (AlO x ) and plasma polymer (PP) were coated on polyethylene naphthalate substrates by plasma-enhanced ALD and plasma-enhanced CVD at 80℃ in the same reactor, respectively. As precursor, trimethylaluminium was used together with oxygen radicals in order to prepare AlO x , and benzene served as precursor to deposit the PP. This hybrid structure allows the decoupling of defects between the single AlO x layers and extends the permeation path for water molecules towards the entire barrier film. Furthermore, the combination of two plasma techniques in a single reactor system enables short process times without vacuum breaks. Single aluminium oxide films by plasma-enhanced ALD were compared to thermally grown layers and showed a significantly better barrier performance. The water vapour transmission rate (WVTR) was determined by means of electrical calcium tests. For a multilayer with 3.5 dyads of 25-nm AlO x and 125-nm PP, a WVTR of 1.2 10 ?3 gm?2d?1 at 60℃ and 90% relative humidity could be observed. PMID:24936155

2014-01-01

250

A diffuse plasma generated by bipolar nanosecond pulsed dielectric barrier discharge in nitrogen  

NASA Astrophysics Data System (ADS)

In this study, a bipolar high-voltage pulse with 20 ns rising time is employed to generate diffuse dielectric barrier discharge plasma using wire-plate electrode configuration in nitrogen at atmospheric pressure. The gas temperature of the plasma is determined by comparing the experimental and the best fitted optical emission spectra of the second positive bands of N2(C3?u ? B3 ?g, 0-2) and the first negative bands of N2+ (B2 ?u+ ? X2 ?g+, 0-0). The effects of the concentration of argon and oxygen on the emission intensities of N2 (C3?u ? B3?g, 0-0, 337.1 nm), OH (A 2? ? X2?, 0-0) and N2+ (B2 ?u+ ? X2 ?g+, 0-0, 391.4 nm) are investigated. It is shown that the plasma gas temperature keeps almost constant with the pulse repetition rate and pulse peak voltage increasing. The emission intensities of N2 (C3?u ? B3?g, 0-0, 337.1 nm), OH(A2? ? X2?, 0-0) and N2+ (B2 ?u+ ? X2 ?g+, 0-0, 391.4 nm) rise with increasing the concentration of argon, but decrease with increasing the concentration of oxygen, and the influences of oxygen concentration on the emission intensities of N2(C3?u ? B3?g, 0-0, 337.1 nm) and OH (A2? ? X2?, 0-0) are more greater than that on the emission intensity of N2+ (B2 ?u+ ? X2 ?g+, 0-0, 391.4 nm).

Jia, Li; Yang, De-Zheng; Shi, Heng-Chao; Wang, Wen-Chun; Wang, Sen

2014-05-01

251

Diamond-like carbon produced by plasma source ion implantation as a corrosion barrier  

SciTech Connect

There currently exists a broad range of applications for which the ability to produce an adherent, hard, wear and, corrosion-resistant coating plays a vital role. These applications include engine components, orthopedic devices, textile manufacturing components, hard disk media, optical coatings, and cutting and machining tools (e.g., punches, taps, scoring dies, and extrusion dies). Ion beam processing can play an important role in all of these technologies. Plasma source ion implantation (PSII) is an emerging technology which has the potential to overcome the limitations of conventional ion implantation by: (1) reducing the time and expense for implanting onto complex shapes and large areas and (2) extending the thickness of the modification zone through ion beam enhanced plasma growth of surface coatings. In PSII, targets are placed directly in a plasma source and then pulse biased to produce a non-line-of-sight process for complex-shaped targets without complex fixturing. If the pulse bias is a relatively high negative potential (20 to 100 kV) ion implantation will result. If however, a low voltage (50--1,200 eV) high duty cycle pulse bias is applied, film deposition from the chamber gas will result, thereby increasing the extent of the surface modification into the 1--10 micron regime. To evaluate the potential for DLC to be used as a corrosion barrier, Electrochemical Impedance Spectroscopy (EIS) and traditional electrochemistry techniques were used to investigate the breakdown mechanism in chloride and nonchloride containing environments. The effect of surface preparation on coating breakdown was also evaluated.

Lillard, R.S.; Butt, D.P.; Taylor, T.N.; Walter, K.C.; Nastasi, M.

1998-03-01

252

Effects of electrode geometry on the performance of dielectric barrier/packed-bed discharge plasmas in benzene degradation.  

PubMed

In this study, the effects of electrode geometry on benzene degradation in a dielectric barrier/packed-bed discharge plasma reactor with different electrodes were systematically investigated. Three electrodes were employed in the experiments, these were coil, bolt, and rod geometries. The reactor using the coil electrode showed better performance in reducing the dielectric loss in the barrier compared to that using the bolt or rod electrodes. In the case of the coil electrode, both the benzene degradation efficiency and energy yield were higher than those for the other electrodes, which can be attributed to the increased role of surface mediated reactions. Irrespective of the electrode geometry, the packed-bed discharge plasma was superior to the dielectric barrier discharge plasma in benzene degradation at any specific applied voltage. The main gaseous products of benzene degradation were CO, CO2, H2O, and formic acid. Discharge products such as O3, N2O, N2O5, and HNO3 were also detected in the outlet gas. Moreover, the presence of benzene inhibited the formation of ozone because of the competing reaction of oxygen atoms with benzene. This study is expected to offer an optimized approach combining dielectric barrier discharge and packed-bed discharge to improve the degradation of gaseous pollutants. PMID:24061216

Jiang, Nan; Lu, Na; Shang, Kefeng; Li, Jie; Wu, Yan

2013-11-15

253

Thermally Actuated Hydraulic Pumps  

NASA Technical Reports Server (NTRS)

Thermally actuated hydraulic pumps have been proposed for diverse applications in which direct electrical or mechanical actuation is undesirable and the relative slowness of thermal actuation can be tolerated. The proposed pumps would not contain any sliding (wearing) parts in their compressors and, hence, could have long operational lifetimes. The basic principle of a pump according to the proposal is to utilize the thermal expansion and contraction of a wax or other phase-change material in contact with a hydraulic fluid in a rigid chamber. Heating the chamber and its contents from below to above the melting temperature of the phase-change material would cause the material to expand significantly, thus causing a substantial increase in hydraulic pressure and/or a substantial displacement of hydraulic fluid out of the chamber. Similarly, cooling the chamber and its contents from above to below the melting temperature of the phase-change material would cause the material to contract significantly, thus causing a substantial decrease in hydraulic pressure and/or a substantial displacement of hydraulic fluid into the chamber. The displacement of the hydraulic fluid could be used to drive a piston. The figure illustrates a simple example of a hydraulic jack driven by a thermally actuated hydraulic pump. The pump chamber would be a cylinder containing encapsulated wax pellets and containing radial fins to facilitate transfer of heat to and from the wax. The plastic encapsulation would serve as an oil/wax barrier and the remaining interior space could be filled with hydraulic oil. A filter would retain the encapsulated wax particles in the pump chamber while allowing the hydraulic oil to flow into and out of the chamber. In one important class of potential applications, thermally actuated hydraulic pumps, exploiting vertical ocean temperature gradients for heating and cooling as needed, would be used to vary hydraulic pressures to control buoyancy in undersea research vessels. Heretofore, electrically actuated hydraulic pumps have been used for this purpose. By eliminating the demand for electrical energy for pumping, the use of the thermally actuated hydraulic pumps could prolong the intervals between battery charges, thus making it possible to greatly increase the durations of undersea exploratory missions.

Jones, Jack; Ross, Ronald; Chao, Yi

2008-01-01

254

Quasistatic vs. Dynamic Modulus Measurements Of Plasma-Sprayed Thermal Barrier Coatings  

NASA Technical Reports Server (NTRS)

Plasma-sprayed 8wt% yttria-stabilized zirconia (8YSZ) thermal barrier coatings (TBCs) have been demonstrated to exhibit nonlinear hysteretic elastic behavior by quasistatic cyclic compression and cylindrical punch indentation measurements. In particular, the instantaneous (tangential) elastic modulus increases with applied stress and exhibits significant hysteresis during cycling. Sound velocity (dynamic) measurements also show an increase in TBC modulus with applied compressive stress, but in contrast show no significant hysteresis for the modulus during cycling. The nonlinear elastic behavior of the TBCs evidenced by these tests is attributed to coating compaction and internal sliding. The differences between the quasistatic and dynamic measurements are explained by the relative absence of the effect of internal sliding in the dynamic modulus measurements. By incorporating short load reversals into the larger loading cycle and measuring the instantaneous modulus at the start of each load reversal, the effects of internal sliding can be substantially reduced in the quasistatic measurements, and the resulting modulus values show good agreement with the modulus values determined by dynamic sound velocity measurements.

Eldridge, J. I.; Morscher, G. N.; Choi, S. R.

2002-01-01

255

Optimization of Air Plasma Sprayed Thermal Barrier Coating Parameters in Diesel Engine Applications  

NASA Astrophysics Data System (ADS)

In the present paper, an optimization of thermal barrier coating parameters is performed for diesel engine applications. The substrate is A356.0-T7, a cast aluminum alloy which has a vast application in diesel engines, and the alloy is coated by plasma sprayed ZrO2-8 wt.% Y2O3. Parameters including the feed rate of coating powders, the nozzle distance to specimen surfaces, and the coating thickness are optimized by thermal shock fatigue tests and bending tests. Optimum values of the feed rate and the nozzle distance are 30 g/min and 80 mm, respectively, when the objective is considered as maximizing the bending strength. Thermal shock tests demonstrate that lower thickness of coating layers has a better lifetime. By increasing the coating thickness, the thermal fatigue lifetime decreases. The reason is due to higher order of stresses near the interface of the substrate and the bond coat layer, calculated by a finite element simulation. One suggestion to improve the lifetime is to use multiple layers of coatings.

Azadi, M.; Farrahi, G. H.; Moridi, A.

2013-11-01

256

Optical emission characteristics of surface nanosecond pulsed dielectric barrier discharge plasma  

SciTech Connect

This paper reports an experimental study of the optical emission characteristics of the surface dielectric barrier discharge plasma excited by nanosecond pulsed voltage. N{sub 2}(C{sup 3}{Pi}{sub u}) rotational and vibrational temperatures are almost the same with upper electrode powered with positive polarity and lower electrode grounded or upper electrode grounded and lower electrode powered with positive polarity. While the electron temperature is 12% higher with upper electrode powered with positive polarity and lower electrode grounded. When the frequency is below 2000 Hz, there is almost no influence of applied voltage amplitude and frequency on N{sub 2}(C{sup 3}{Pi}{sub u}) rotational, vibrational temperature and electron temperature. As the pressure decreases from 760 Torr to 5 Torr, N{sub 2}(C{sup 3}{Pi}{sub u}) rotational temperature remains almost unchanged, while its vibrational temperature decreases initially and then increases. The discharge mode changes from a filamentary type to a glow type around 80 Torr. In the filamentary mode, the electron temperature remains almost unchanged. In the glow mode, the electron temperature increases while the pressure decreases.

Wu Yun; Li Yinghong; Jia Min; Song Huimin; Liang Hua [Science and Technology on Plasma Dynamics Lab, Aeronautics and Astronautics Engineering College, Air Force Engineering University, Xi'an 710038 (China)

2013-01-21

257

The surface cracking behavior in air plasma sprayed thermal barrier coating system incorporating interface roughness effect  

NASA Astrophysics Data System (ADS)

The objective of this work is to understand the effect of interface roughness on the strain energy release rate and surface cracking behavior in air plasma sprayed thermal barrier coating system. This is achieved by a parameter investigation of the interfacial shapes, in which the extended finite element method (XFEM) and periodic boundary condition are used. Predictions for the stress field and driving force of multiple surface cracks in the film/substrate system are presented. It is seen that the interface roughness has significant effects on the strain energy release rate, the interfacial stress distribution, and the crack propagation patterns. One can see the completely different distributions of stress and strain energy release rate in the regions of convex and concave asperities of the substrate. Variation of the interface asperity is responsible for the oscillatory characteristics of strain energy release rate, which can cause the local arrest of surface cracks. It is concluded that artificially created rough interface can enhance the durability of film/substrate system with multiple cracks.

Zhang, W. X.; Fan, X. L.; Wang, T. J.

2011-11-01

258

Actuated atomizer  

NASA Technical Reports Server (NTRS)

An actuated atomizer is adapted for spray cooling or other applications wherein a well-developed, homogeneous and generally conical spray mist is required. The actuated atomizer includes an outer shell formed by an inner ring; an outer ring; an actuator insert and a cap. A nozzle framework is positioned within the actuator insert. A base of the nozzle framework defines swirl inlets, a swirl chamber and a swirl chamber. A nozzle insert defines a center inlet and feed ports. A spool is positioned within the coil housing, and carries the coil windings having a number of turns calculated to result in a magnetic field of sufficient strength to overcome the bias of the spring. A plunger moves in response to the magnetic field of the windings. A stop prevents the pintle from being withdrawn excessively. A pintle, positioned by the plunger, moves between first and second positions. In the first position, the head of the pintle blocks the discharge passage of the nozzle framework, thereby preventing the atomizer from discharging fluid. In the second position, the pintle is withdrawn from the swirl chamber, allowing the atomizer to release atomized fluid. A spring biases the pintle to block the discharge passage. The strength of the spring is overcome, however, by the magnetic field created by the windings positioned on the spool, which withdraws the plunger into the spool and further compresses the spring.

Tilton, Charles (Inventor); Weiler, Jeff (Inventor); Palmer, Randall (Inventor); Appel, Philip (Inventor)

2008-01-01

259

Pneumatic Actuators  

NSDL National Science Digital Library

This learning object covers cylinders and motor pneumatic actuators. It is hosted by the University of Wisconsin-Madison and consists of cylinders operations such as: single, duel acting, factors for cylinder speed. The program require Macromedia Flash player, and presents a very nice overall presentation format.

2008-11-14

260

SiO-like film deposition by dielectric barrier discharge plasma gun at ambient temperature under an atmospheric pressure  

Microsoft Academic Search

A medium-frequency dielectric barrier discharge (DBD) plasma gun was used to deposit SiO-like films at ambient temperature under atmospheric pressure. SiO-like films were deposited on Si and stainless-steel surfaces by flowing Ar gas containing hexamethyldisiloxane (HMDSO) monomer through the gun. The authors found that the chemical structure of the deposited SiO-like film strongly depended on the HMDSO monomer ratio in

Chen Qiang; Zhang Yuefei; Han Erli; Ge Yuanjing

2006-01-01

261

Effect of Thermal Treatment on the Grain Growth of Nanostructured YSZ Thermal Barrier Coating Prepared by Air Plasma Spraying  

Microsoft Academic Search

A nanostructured thermal barrier coating is prepared by air plasma spraying using the 8wt% Y2O3 partially stabilized zirconia nano-powder with an average grain size of 40 nm. The microstructure and phase composition of feedstock nano-powder and coating are investigated using SEM, TEM and XRD. It is found that the as-sprayed zirconia coating has an average grain size of 67 nm

Zhen-bo WANG; Chun-gen ZHOU; Hui-bin XU; Sheng-kai GONG

2004-01-01

262

Fracture toughness measurements of plasma-sprayed thermal barrier coatings using a modified four-point bending method  

Microsoft Academic Search

In this study, the adhesion strength of thermal barrier coatings 8YSZ (ZrO2+8wt.% Y2O3) deposited on NiCrAlY bond coats by atmospheric plasma spraying is investigated experimentally. A modified four-point bending specimen that can generate a single interface crack to facilitate the control of crack growth was adopted for testing. The fracture surfaces were examined using a scanning electron microscope. Images show

P. F. Zhao; C. A. Sun; X. Y. Zhu; F. L. Shang; C. J. Li

2010-01-01

263

High performance nanostructured ZrO 2 based thermal barrier coatings deposited by high efficiency supersonic plasma spraying  

Microsoft Academic Search

In this paper, the nanostructured zirconia (ZrO2) based thermal barrier coatings (TBCs) deposited by high efficiency supersonic atmospheric plasma spraying (SAPS), were described. The phase composition, microstructure, thermal conductivity and thermal shock resistance of as-sprayed coating were studied. The results revealed that the as-sprayed coating was composed of tetragonal zirconia and consisted of some unmelted nanoparticles (3050nm) and nanograins (60110nm),

Y. Bai; Z. H. Han; H. Q. Li; C. Xu; Y. L. Xu; Z. Wang; C. H. Ding; J. F. Yang

2011-01-01

264

Application of Cr 3+ photoluminescence piezo-spectroscopy to plasma-sprayed thermal barrier coatings for residual stress measurement  

Microsoft Academic Search

Cr3+ photoluminescence piezo-spectroscopy (CPLPS) is being developed as a non-destructive inspection technique for the measurement of residual stresses within the thermally grown oxide (TGO; consisting of ?-Al2O3 with Cr3+ solute) layer buried under Y2O3-stabilized ZrO2 (YSZ) thermal barrier coatings (TBCs). In this study, CPLPS experiments were performed to measure residual stresses in TGOs buried under four different types of plasma-sprayed

K. W Schlichting; K Vaidyanathan; Y. H Sohn; E. H Jordan; M Gell; N. P Padture

2000-01-01

265

A mechanistic study of oxidation-induced degradation in a plasma-sprayed thermal barrier coating system  

Microsoft Academic Search

The effect of the oxidation induced degradation of a typical plasma-sprayed thermal barrier coating (PS-TBC) system on the local ceramicmetal interfacial stresses responsible for the nucleation of mesoscopic cracks is investigated. A coupled oxidation-constitutive approach is proposed to describe the effect of the phase transformations caused by local internal and external oxidation processes on the constitutive behaviour of the metallic

E. P. Busso; J. Lin; S. Sakurai; M. Nakayama

2001-01-01

266

Axial plasma density propagation of barrier discharge non-thermal plasma bullets in an atmospheric pressure argon gas stream  

NASA Astrophysics Data System (ADS)

The characteristics of volume-averaged plasma density on axial propagation for atmospheric argon (Ar) plasma bullets are experimentally investigated. The non-thermal plasma bullets are ejected through a glass tube into the surrounding ambient air. Taking into consideration the time and space profile of the plasma movement, the plasma propagation is measured using a Rogowski coil. The plasma density is evaluated from the propagation velocity and the current magnitude. The plasma density profiles are presented as functions of the applied voltage and the length of growth. The plasma density is in the order of 1016 m-3 and the propagation velocity is in the order of 105 m s-1. These values are similar to those of weakly ionized non-thermal plasma jets.

Ohyama, R.; Sakamoto, M.; Nagai, A.

2009-05-01

267

Electrorepulsive actuator  

NASA Technical Reports Server (NTRS)

The invention is a linear actuator that operates under the principle that like charges repel and opposite charges attract. The linear actuator consists of first and second pairs of spaced opposed conductors where one member of each pair of conductors is attached to a fixed member, and where the other member of each pair of conductors is attached to a movable member such as an elongated rod. The two pairs of spaced conductors may be provided in the form of two spacedly interwound helical vanes where the conductors are located on the opposite sides of the two helical vanes. One helical vane extends inwardly from a housing and the other helical vane extends outwardly from an elongated rod. The elongated rod may be caused to move linearly with respect to the housing by applying appropriate charges of like or opposite polarity to the electrical conductors on the helical vanes.

Collins, Earl R., Jr. (inventor); Curry, Kenneth C. (inventor)

1992-01-01

268

Sintering and Fracture Behavior of Plasma-sprayed Thermal Barrier Coatings  

NASA Technical Reports Server (NTRS)

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. There is a need to characterize the fundamental sintering and fracture behavior of the current ZrO2-(7 to 8)wt%Y2O3 coating, in order to fully take advantage of the coating capability. In addition, a thorough evaluation of the coating behavior and temperature limits will be useful for more accurately assessing the benefit gained from future advanced coating systems. In this study, the sintering behavior of plasma-sprayed ZrO2-8wt%Y2O3 coatings was systematically investigated as a function of temperature and time using a dilatometer in the temperature range of 1200-1500 C. The coating sintering kinetics obtained by dilatometry were compared with the coating thermal conductivity increase kinetics, determined by a steady-state laser heat-flux testing approach, under high temperature and thermal gradient sintering conditions. The mode I, mode II, and mixed mode I-mode II fracture behavior of as-processed and sintering-annealed coatings was determined in asymmetric flexure loading at ambient and elevated temperatures in order to evaluate the coating sintering effects on the fracture envelope of K(sub I) versus K(sub II). The coating thermal conductivity cyclic response associated with the interface delamination of the coating systems under simulated engine heat-flux conditions will be discussed in conjunction with the sintering and fracture testing results.

Zhu, Dongming; Choi, Sung R.; Miller, Robert A.

2004-01-01

269

Improved Electrohydraulic Linear Actuators  

NASA Technical Reports Server (NTRS)

A product line of improved electrohydraulic linear actuators has been developed. These actuators are designed especially for use in actuating valves in rocket-engine test facilities. They are also adaptable to similar industrial uses. Advantageous features of the electrohydraulic linear actuators with respect to shortcomings of prior electrohydraulic linear actuators are described.

Hamtil, James

2002-01-01

270

Permanent hydrophilization of outer and inner surfaces of polytetrafluoroethylene tubes using ambient air plasma generated by surface dielectric barrier discharges  

NASA Astrophysics Data System (ADS)

We present an atmospheric pressure ambient air plasma technique developed for technically simple treatment of inner and/or outer surfaces of plastic tubes and other hollow dielectric bodies. It is based on surface dielectric barrier discharge generating visually diffuse plasma layers along the treated dielectric surfaces using water-solution electrodes. The observed visual uniformity and measured plasma rotational and vibrational temperatures of 333 K and 2350 K indicate that the discharge can be readily applied to material surface treatment without significant thermal effect. This is exemplified by the obtained permanent surface hydrophilization of polytetrafluoroethylene tubes related to the replacement of a high fraction (more than 80%) of the surface fluorine determined by X-ray photoelectron spectroscopy. A tentative explanation of the discharge mechanism based on high-speed camera observations and the discharge current and voltage of measurements is outlined.

Pavlik, D.; Galmiz, O.; Zemnek, M.; Brablec, A.; ?ech, J.; ?ernk, M.

2014-10-01

271

Thermal cycling life and thermal diffusivity of a plasma-sprayed nanostructured thermal barrier coating  

Microsoft Academic Search

The nanostructured thermal barrier coatings exhibited excellent thermal cyclic resistance and low thermal diffusivity. The thermal cyclic life of the coating is about 600 h for 1-h cycles at 1050 C. The thermal diffusivity of the coating is 90% of that of conventional thermal barrier coatings.

Chungen Zhou; Na Wang; Zhenbo Wang; Shengkai Gong; Huibin Xu

2004-01-01

272

Memory metal actuator  

NASA Technical Reports Server (NTRS)

A mechanical actuator can be constructed by employing a plurality of memory metal actuator elements in parallel to control the amount of actuating force. In order to facilitate direct control by digital control signals provided by a computer or the like, the actuating elements may vary in stiffness according to a binary relationship. The cooling or reset time of the actuator elements can be reduced by employing Peltier junction cooling assemblies in the actuator.

Ruoff, C. F. (inventor)

1985-01-01

273

Fast ion stabilization of the ion temperature gradient driven modes in the Joint European Torus hybrid-scenario plasmas: a trigger mechanism for internal transport barrier formation  

Microsoft Academic Search

Understanding and modelling turbulent transport in thermonuclear fusion plasmas are crucial for designing and optimizing the operational scenarios of future fusion reactors. In this context, plasmas exhibiting state transitions, such as the formation of an internal transport barrier (ITB), are particularly interesting since they can shed light on transport physics and offer the opportunity to test different turbulence suppression models.

M. Romanelli; A. Zocco; F. Crisanti; JET-EFDA Contributors

2010-01-01

274

Plasma-assisted atomic layer deposition of Al{sub 2}O{sub 3} moisture permeation barriers on polymers  

SciTech Connect

Thin Al{sub 2}O{sub 3} films of different thicknesses (10-40 nm) were deposited by plasma-assisted atomic layer deposition on substrates of poly(2,6-ethylenenaphthalate) (PEN), and the water vapor transmission rate (WVTR) values were measured by means of the calcium test. The permeation barrier properties improved with decreasing substrate temperature and a good WVTR of 5x10{sup -3} g m{sup -2} day{sup -1} (WVTR{sub PEN}=0.5 g m{sup -2} day{sup -1}) was measured for a 20 nm thick Al{sub 2}O{sub 3} film deposited at room temperature using short purging times. Such ultrathin, low-temperature deposited, high-quality moisture permeation barriers are an essential requirement for the implementation of polymeric substrates in flexible electronic and display applications.

Langereis, E.; Creatore, M.; Heil, S. B. S.; Sanden, M. C. M. van de; Kessels, W. M. M. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)

2006-08-21

275

Combined Mode I and Mode II Fracture of Plasma-Sprayed Thermal Barrier Coatings at Ambient and Elevated Temperatures  

NASA Technical Reports Server (NTRS)

The mode I, mode II, and combined mode I-mode II fracture behavior of ZrO2- 8wt%Y2O3 thermal barrier coatings was determined in asymmetric flexure loading at both ambient and elevated temperatures. Precracks were introduced in test specimens using the single-edge-v-notched beam (SEVNB) method incorporated with final diamond polishing to achieve sharp crack tips. A fracture envelope of KI versus KII was determined for the coating material at ambient and elevated temperatures. Propagation angles of fracture as a function of K(sub I)/K(sub II) were also determined. The mixed-mode fracture behaviors of the coating material were compared with those of monolithic advanced ceramics determined previously. The mixed-mode fracture behavior of the plasma-sprayed thermal barrier coating material was predicted in terms of fracture envelope and propagation angle using mixed-mode fracture theories.

Choi, Sung R.; Zhu, Dongming; Miller, Robert A.

2003-01-01

276

Combined Mode I and Mode II Fracture of Plasma-Sprayed Thermal Barrier Coatings at Ambient and Elevated Temperatures  

NASA Technical Reports Server (NTRS)

The mode I, mode II, and combined mode I-mode II fracture behavior of ZrO2 - 8wt%Y2O3 thermal barrier coatings was determined in asymmetric flexure loading at both ambient and elevated temperatures. Precracks were introduced in test specimens using the single-edge-v-notched beam (SEVNB) method incorporated with final diamond polishing to achieve sharp crack tips. A fracture envelope of KI versus KII was determined for the coating material at ambient and elevated temperatures. Propagation angles of fracture as a function of KI/KII were also determined. The mixed-mode fracture behaviors of the coating material were compared with those of monolithic advanced ceramics determined previously. The mixed-mode fracture behavior of the plasma- sprayed thermal barrier coating material was predicted in terms of fracture envelope and propagation angle using mixed-mode fracture theories.

Choi, Sung R.; Zhu, Dongming; Miller, Robert A.

2003-01-01

277

Measurement of Turbulence Decorrelation during Transport Barrier Evolution in a High Temperature Fusion Plasma  

SciTech Connect

A low power polychromatic beam of microwaves is used to diagnose the behavior of turbulent fluctuations in the core of the JT-60U tokamak during the evolution of the internal transport barrier. A continuous reduction in the size of turbulent structures is observed concomitant with the reduction of the density scale length during the evolution of the internal transport barrier. The density correlation length decreases to the order of the ion gyroradius, in contrast to the much longer scale lengths observed earlier in the discharge, while the density fluctuation level remain similar to the level before transport barrier formation.

R. Nazikian; K. Shinohara; G.J. Kramer; E. Valeo; K. Hill; T.S. Hahm; G. Rewoldt; S. Ide; Y. Koide; Y. Oyama; H. Shirai; W. Tang

2005-03-29

278

Attenuation of single-tone ultrasound by an atmospheric glow discharge plasma barrier  

E-print Network

obtained in and around the plasma using laser-induced Rayleigh scattering technique. Results show­15 It is caused by the interactions between the external electric field and the plasma constituents i, the plasma effect manifests itself via interactions between the neutral gas components and the charged

?tügen, Volkan

279

Temperature dependence of interface barrier height change and field emission studies of plasma-treated graphene films  

NASA Astrophysics Data System (ADS)

The field emission properties of plasma-treated graphene films (PTGFs) have been investigated from 300 to 50 K. It is found that the turn-on field increases from 4 to 6.2 V/m, and the current density decreases with decreasing temperature. On the basis of the semiconductor thermionic emission theory, the changes in field emission properties at low temperature can be successfully explained. The increase in interface barrier height at low temperature results in the changes in the field emission properties of PTGFs.

Wu, Shuxian; Xue, Shaolin; Zeng, Yijie; Zhou, Weikang; Han, Junwei

2014-09-01

280

Assessment of a dielectric barrier discharge plasma reactor at atmospheric pressure for the removal of bisphenol A and tributyltin.  

PubMed

The ability of a laboratory-scale dielectric barrier discharge (DBD) nonthermal plasma reactor at atmospheric pressure was assessed for the removal of bisphenol A (1 mg L(-1)) and tributyltin (10 mg L(-1)) from aqueous solutions. The elimination of both the compounds followed an exponential decay equation, and a first-order degradation kinetics was proposed for them (k = 0.662 min(-1) for bisphenol A and k = 0.800 min(-1) for tributyltin), reaching in both cases about 96% removal after 5-min treatment. Accordingly, plasma DBD reactors could be used as alternative advanced oxidation technologies for the removal of some persistent and toxic pollutants from water and wastewater, although further research should be performed to evaluate the effluent toxicity. PMID:24701940

Hijosa-Valsero, Maria; Molina, Ricardo; Bayona, Josep M

2014-01-01

281

Silicon oxide barrier films deposited on PET foils in pulsed plasmas: influence of substrate bias on deposition process and film properties  

NASA Astrophysics Data System (ADS)

A widely used plastic for packaging, polyethylene terephtalate (PET) offers limited barrier properties against gas permeation. For many applications of PET (from food packaging to micro electronics) improved barrier properties are essential. A silicon oxide barrier coating of PET foils is applied by means of a pulsed microwave driven low-pressure plasma. While the adjustment of the microwave power allows for a control of the ion production during the plasma pulse, a substrate bias controls the energy of ions impinging on the substrate. Detailed analysis of deposited films applying oxygen permeation measurements, x-ray photoelectron spectroscopy and atomic force microscopy are correlated with results from plasma diagnostics describing the deposition process. The influence of a change in process parameters such as gas mixture and substrate bias on the gas temperature, electron density, mean electron energy, ion energy and the atomic oxygen density is studied. An additional substrate bias results in an increase in atomic oxygen density up to a factor of 6, although plasma parameter such as electron density of ne = 3.8 0.8 1017 m-3 and electron temperature of kBTe = 1.7 0.1 eV are unmodified. It is shown that atomic oxygen densities measured during deposition process higher than nO = 1.8 1021 m-3 yield in barrier films with a barrier improvement factor up to 150. Good barrier films are highly cross-linked and show a smooth morphology.

Steves, S.; Ozkaya, B.; Liu, C.-N.; Ozcan, O.; Bibinov, N.; Grundmeier, G.; Awakowicz, P.

2013-02-01

282

Robust TaN{sub x} diffusion barrier for Cu-interconnect technology with subnanometer thickness by metal-organic plasma-enhanced atomic layer deposition  

SciTech Connect

TaN{sub x} diffusion barriers with good barrier properties at subnanometer thickness were deposited by plasma-enhanced atomic layer deposition (PE-ALD) from pentakis(dimethylamino)Ta. Hydrogen and/or nitrogen plasma was used as reactants to produce TaN{sub x} thin films with a different nitrogen content. The film properties including the carbon and oxygen impurity content were affected by the nitrogen flow during the process. The deposited film has nanocrystalline grains with hydrogen-only plasma, while the amorphous structure was obtained for nitrogen plasma. The diffusion barrier properties of deposited TaN films for Cu interconnects have been studied by thermal stress test based on synchrotron x-ray diffraction. The results indicate that the PE-ALD TaN films are good diffusion barriers even at a small thickness as 0.6 nm. Better diffusion barrier properties were obtained for higher nitrogen content. Based on a diffusion kinetics analysis, the nanocrystalline microstructure of the films was responsible for the better diffusion barrier properties compared to polycrystalline PE-ALD TaN films deposited from TaCl{sub 5}.

Kim, H.; Detavenier, C.; Straten, O. van der; Rossnagel, S.M.; Kellock, A.J.; Park, D.-G. [Department of Materials Science and Technology, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); International Business Machines Corporation (IBM) T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States); International Business Machines Corporation (IBM) Almaden Research Center, San Jose, California 95120 (United States); International Business Machines Corporation (IBM) Microelectronics Division Hopewell Junction, New York 12533 (United States)

2005-07-01

283

Thermal Barrier Coatings Made by the Solution Precursor Plasma Spray Process  

Microsoft Academic Search

The solution precursor plasma spray (SPPS) process is a relatively new and flexible thermal spray process that can produce\\u000a a wide variety of novel materials, including some with superior properties. The SPPS process involves injecting atomized droplets\\u000a of a precursor solution into the plasma. The properties of resultant deposits depend on the time-temperature history of the\\u000a droplets in the plasma,

Maurice Gell; Eric H. Jordan; Matthew Teicholz; Baki M. Cetegen; Nitin P. Padture; Liangde Xie; Dianying Chen; Xinqing Ma; Jeffrey Roth

2008-01-01

284

Nonthermal Dielectric Barrier Discharge (DBD) Plasma Suppresses Herpes Simplex Virus Type 1 (HSV-1) Replication in Corneal Epithelium  

PubMed Central

Purpose Herpes keratitis (HK) is the leading cause of cornea-derived and infection-associated blindness in the developed world. Despite the availability of effective antivirals, some patients develop refractory disease, drug-resistant infection, and topical toxicity. A nonpharmaceutical treatment modality may offer a unique advantage in the management of such cases. This study investigated the antiviral effect of nonthermal dielectric barrier discharge (DBD) plasma, a partially ionized gas that can be applied to organic substances to produce various biological effects. Methods Human corneal epithelial cells and explanted corneas were infected with herpes simplex virus type 1 (HSV-1) and exposed to culture medium treated with nonthermal DBD plasma. The extent of infection was measured by plaque assay, quantitative PCR, and Western blot. Corneal toxicity assessment was performed with fluorescein staining, histologic examination, and 8-OHdG detection. Results Application of DBD plasmatreated medium to human corneal epithelial cells and explanted corneas produced a dose-dependent reduction of the cytopathic effect, viral genome replication, and the overall production of infectious viral progeny. Toxicity studies showed lack of detrimental effects in explanted human corneas. Conclusions Nonthermal DBD plasma substantially suppresses corneal HSV-1 infection in vitro and ex vivo without causing pronounced toxicity. Translational Relevance Nonthermal plasma is a versatile tool that holds great biomedical potential for ophthalmology, where it is being investigated for wound healing and sterilization and is already in use for ocular microsurgery. The anti-HSV-1 activity of DBD plasma demonstrated here could be directly translated to the clinic for use against drug-resistant herpes keratitis. PMID:24757592

Alekseev, Oleg; Donovan, Kelly; Limonnik, Vladimir; Azizkhan-Clifford, Jane

2014-01-01

285

Collective Phenomena In Volume And Surface Barrier Discharges  

NASA Astrophysics Data System (ADS)

Barrier discharges are increasingly used as a cost-effective means to produce non-equilibrium plasmas at atmospheric pressure. This way, copious amounts of electrons, ions, free radicals and excited species can be generated without appreciable gas heating. In most applications the barrier is made of dielectric material. In laboratory experiments also the use of resistive, ferroelectric and semiconducting materials has been investigated, also porous ceramic layers and dielectric barriers with controlled surface conductivity. Major applications utilizing mainly dielectric barriers include ozone generation, surface cleaning and modification, polymer and textile treatment, sterilization, pollution control, CO2 lasers, excimer lamps, plasma display panels (flat TV screens). More recent research efforts are also devoted to biomedical applications and to plasma actuators for flow control. Sinu- soidal feeding voltages at various frequencies as well as pulsed excitation schemes are used. Volume as well as surface barrier discharges can exist in the form of filamentary, regularly patterned or laterally homogeneous discharges. Reviews of the subject and the older literature on barrier discharges were published by Kogelschatz (2002, 2003), by Wagner et al. (2003) and by Fridman et al. (2005). A detailed discussion of various properties of barrier discharges can also be found in the recent book "Non-Equilibrium Air Plasmas at Atmospheric Pressure" by Becker et al. (2005). The physical effects leading to collective phenomena in volume and surface barrier discharges will be discussed in detail. Special attention will be given to self-organization of current filaments. Main similarities and differences of the two types of barrier discharges will be elaborated.

Kogelschatz, U.

2010-07-01

286

Microprocessor controlled force actuator  

NASA Technical Reports Server (NTRS)

The mechanical and electrical design of a prototype force actuator for vibration control of large space structures (LSS) is described. The force actuator is an electromagnetic system that produces a force by reacting against a proof-mass. The actuator has two colocated sensors, a digital microcontroller, and a power amplifier. The total weight of actuator is .998 kg. The actuator has a steady state force output of approximately 2.75 N from approximately 2 Hz to well beyond 1000 Hz.

Zimmerman, D. C.; Inman, D. J.; Horner, G. C.

1986-01-01

287

Failure mechanisms associated with the thermally grown oxide in plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

The microstructure and durability of a thermal barrier coating (TBC) produced by the thermal spray method have been characterized. Upon exposure, the bond coat chemistry and microstructure change by inter-diffusion with the substrate and upon thickening of the thermally grown oxide (TGO). A wedge impression test, in conjunction with observations by scanning electron microscopy, has been used to probe the

A Rabiei; A. G Evans

2000-01-01

288

Mechanical properties and oxidation resistance of plasma-sprayed multilayered Al 2O 3\\/ZrO 2 thermal barrier coatings  

Microsoft Academic Search

Coupled with functionally graded materials (FGM) concept, Al2O3 was proposed as a potential candidate as an interlayer to improve the oxidation resistance of thermal barrier coating (TBC) system due to its low oxygen diffusivity. Plasma spray process was utilized to produce Al2O3\\/ZrO2 functionally graded thermal barrier coating (FG-TBC). This article discusses physical and mechanical properties, thermal behavior, and high-temperature oxidation

Andi M. Limarga; Sujanto Widjaja; Tick Hon Yip

2005-01-01

289

Effects of Environmental Humidity and Temperature on Sterilization Efficiency of Dielectric Barrier Discharge Plasmas in Atmospheric Pressure Air  

NASA Astrophysics Data System (ADS)

The inactivation of Bacillus atrophaeus spores by a dielectric barrier discharge (DBD) plasma in atmospheric humid air was investigated in order to develop a low-temperature, low-cost, and high-speed plasma sterilization technique. The biological indicators covered with a Tyvek sheet were set just outside the DBD plasma region, where air temperature and humidity as a discharge gas were precisely controlled by an environmental test chamber. The results show that the inactivation of B. atrophaeus spores was found to be dependent strongly on humidity, and was completed within 15 min at a relative humidity of 90% and a temperature of 30 C. The treatment time for sterilization is shorter than those of conventional sterilization methods using ethylene oxide gas and dry heat treatment. The inactivation rates depend on not only relative humidity but also temperature, so that water content in air could determine the generation of reactive species such as hydroxyl radicals that are effective for the inactivation of B. atrophaeus spores.

Kikuchi, Yusuke; Miyamae, Masanori; Nagata, Masayoshi; Fukumoto, Naoyuki

2011-01-01

290

Single-chamber plasma enhanced chemical vapor deposition of transparent organic/inorganic multilayer barrier coating at low temperature  

SciTech Connect

Deposition of organic/inorganic multilayers is usually carried out by two different process steps by two different deposition methods. A single-chamber process for the deposition of multilayer stacks can make the process and deposition system simpler. In this work, SiOCH and plasma-polymerized methylcyclohexane (pp-MCH) films and their multilayer stacks for application to transparent diffusion barrier coatings were deposited in a single low-temperature plasma enhanced chemical vapor deposition reactor using hexamethyldisilazane/N{sub 2}O/O{sub 2}/Ar and methylcyclohexane/Ar mixtures for SiOCH and pp-MCH layers, respectively. The deposition rates of the SiOCH and pp-MCH layers were increased with increasing the N{sub 2}O:O{sub 2} gas flow ratio and rf plasma power, respectively. Oxygen concentration in the SiOCH films was decreased and carbon and hydrogen incorporation was increased when increasing the N{sub 2}O:O{sub 2} gas flow ratio from 0:1 to 3:1. In this work, the water vapor transmission rate of polyester sulfone substrate could be reduced from a level of 50 (bare substrate) to 0.8 g/m{sup 2} day after deposition of a pp-MCH/SiOCH/pp-MCH multilayer coating.

Park, S. M.; Kim, D. J.; Kim, S. I.; Lee, N.-E. [School of Advanced Materials Science and Engineering, Center for Advanced Plasma Surface Technology, Sungkyunkwan University, Suwon, Kyunggi-do 440-746 (Korea, Republic of)

2008-07-15

291

Removal of ammonia from gas streams with dielectric barrier discharge plasmas  

Microsoft Academic Search

We reported on the experimental study of gas-phase removal of ammonia (NH3) via dielectric barrier discharge (DBD) at atmospheric pressure, in which we mainly concentrated on three aspectsinfluence of initial NH3 concentration, peak voltage, and gas residence time on NH3 removal efficiency. Effectiveness, e.g. the removal efficiency, specific energy density, absolute removal amount and energy yield, of the self-made DBD

Lanyan Xia; Li Huang; Xiaohong Shu; Renxi Zhang; Wenbo Dong; Huiqi Hou

2008-01-01

292

Lanthanum hexaaluminatea new material for atmospheric plasma spraying of advanced thermal barrier coatings  

Microsoft Academic Search

One of the main application fields of the thermal spraying process is thermal barrier coatings (TBCs). Today, partially stabilized\\u000a zirconia (YSZ or MSZ) is mainly used as a TBC material. At temperatures above 1000 ?C, zirconia layers age distinctively,\\u000a including phenomena shrinkage and microcrack formation. Therefore, there is a considerable interest in TBCs for higher temperature\\u000a applications. In this paper,

C. Friedrich; R. Gadow; T. Schirmer

2001-01-01

293

Barrier Metal Properties of Amorphous Tantalum Nitride Thin Films between Platinum and Silicon deposited using Remote Plasma Metal Organic Chemical Vapor Method  

Microsoft Academic Search

Amorphous TaN thin films have been prepared by remote plasma-assisted metal organic chemical vapor deposition using pentakis-dimethyl-amino-tantalum (PDMATa) in hydrogen plasma. The dependence of film properties such as resistivity, impurity contents, and microstructures on deposition conditions is reported. All obtained films have been tested as diffusion barriers between platinum and silicon in a stacked-capacitor type memory cell for future, high-density

Chang-Hee Han; Kwang-Nam Cho; Jae-Eung Oh; Su-Hyoun Paek; Chang-Soo Park; Sang-In Lee; Moon Yong Lee; Jong Gil Lee

1998-01-01

294

High performance nanostructured ZrO 2 based thermal barrier coatings deposited by high efficiency supersonic plasma spraying  

NASA Astrophysics Data System (ADS)

In this paper, the nanostructured zirconia (ZrO 2) based thermal barrier coatings (TBCs) deposited by high efficiency supersonic atmospheric plasma spraying (SAPS), were described. The phase composition, microstructure, thermal conductivity and thermal shock resistance of as-sprayed coating were studied. The results revealed that the as-sprayed coating was composed of tetragonal zirconia and consisted of some unmelted nanoparticles (30-50 nm) and nanograins (60-110 nm), and the latter was the main microstructure of the coating. The nanograins and homogeneously distributed micro-cracks of coating resulted in not only low thermal conductivity, but also high thermal cycling lives. Besides, the failure process of coating during thermal cycles was also investigated in the present work.

Bai, Y.; Han, Z. H.; Li, H. Q.; Xu, C.; Xu, Y. L.; Wang, Z.; Ding, C. H.; Yang, J. F.

2011-06-01

295

Optimizing Compliance and Thermal Conductivity of Plasma Sprayed Thermal Barrier Coatings via Controlled Powders and Processing Strategies  

NASA Astrophysics Data System (ADS)

The properties and performance of plasma-sprayed thermal barrier coatings (TBCs) are strongly dependent on the microstructural defects, which are affected by starting powder morphology and processing conditions. Of particular interest is the use of hollow powders which not only allow for efficient melting of zirconia ceramics but also produce lower conductivity and more compliant coatings. Typical industrial hollow spray powders have an assortment of densities resulting in masking potential advantages of the hollow morphology. In this study, we have conducted process mapping strategies using a novel uniform shell thickness hollow powder to control the defect microstructure and properties. Correlations among coating properties, microstructure, and processing reveal feasibility to produce highly compliant and low conductivity TBC through a combination of optimized feedstock and processing conditions. The results are presented through the framework of process maps establishing correlations among process, microstructure, and properties and providing opportunities for optimization of TBCs.

Tan, Yang; Srinivasan, Vasudevan; Nakamura, Toshio; Sampath, Sanjay; Bertrand, Pierre; Bertrand, Ghislaine

2012-09-01

296

Formation of Selective High Barrier Region by Inductively Coupled Plasma Treatment on GaN-Based Light-Emitting Diodes  

NASA Astrophysics Data System (ADS)

By inductively coupled plasma (ICP) etching, a selective high barrier region (SHBR) was fabricated below the p-pad metal electrode for modifying the injection current distribution on p-type GaN of GaN-based light-emitting diodes (LEDs). Through the analysis of current noise power spectra, the samples with ICP etching treatment have excess nitrogen vacancies at the selectively etched surface of p-type GaN; thus, they have a lower hole concentration than the as-grown sample, resulting in a larger barrier height for carrier transport. With this SHBR, the light-output power for the LED chip measured at 20 mA was significantly increased by 12% as compared with that for the conventional LED chip. The light-output power increase could be attributed to a relative reduction in optical power absorption under the p-pad electrode and a higher density of current effectively injected into the active layer of the LED by the SHBR structure.

Kuo, Ting-Wei; Lin, Shi-Xiong; Hung, Pin-Kun; Chong, Kwok-Keung; Hung, Chen-I.; Houng, Mau-Phon

2010-11-01

297

Mixed Mode Fracture of Plasma Sprayed Thermal Barrier Coatings: Effects of Anisotropy and Heterogeneity  

NASA Technical Reports Server (NTRS)

The combined mode I-mode II fracture behavior of anisotropic ZrO2-8wt%Y2O3 thermal barrier coatings was determined in asymmetric flexure loading at both ambient and elevated temperatures. A fracture envelope of KI versus KII was determined for the coating material at ambient and elevated temperatures. Propagation angles of fracture as a function of KI/KII were also determined. The mixed-mode fracture behavior of the microsplat coating material was modeled using Finite Element approach to account for anisotropy and micro cracked structures, and predicted in terms of fracture envelope and propagation angle using mixed-mode fracture theories.

Zhu, Dongming; Choi, Sung R.; Ghosn, Louis L.

2008-01-01

298

Hot-corrosion behavior of graded thermal barrier coatings formed by plasma-spraying process  

Microsoft Academic Search

The hot-corrosion behavior of thermal barrier coatings (TBCs) has been studied by comparing double-layer coatings and graded\\u000a coatings. Two types of oxide ceramics, 2CaOSiO2-15mass%CaOZrO2 (C2S-15CZ) and 8 mass% Y2O3ZrO2 (8YSZ), with a bond coating of NiCrAlY, were applied to metallic substrates in this study. After hot-corrosion testing with\\u000a V2O5-Na2SO4 corrosive ash for 3 h at 1273 K, the TBCs were

N. Mifune; Y. Harada; T. Doi; R. Yamasaki

2004-01-01

299

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

Microsoft Academic Search

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

WITOLD K. SUBCZYNSKI; LARRY E. HOPWOOD; JAMES S. HYDE

1992-01-01

300

Interaction between soot particles and NOx during dielectric barrier discharge plasma remediation of simulated diesel exhaust  

E-print Network

of simulated diesel exhaust Rajesh Doraia) University of Illinois, Department of Chemical Engineering, 1406 from combustion effluent and from diesel exhausts in particular. Soot particles are inevitably present, a computational investigation of the effect of soot on the plasma chemistry of NOx removal in a simulated diesel

Kushner, Mark

301

Oxygen transport by gas permeation through the zirconia layer in plasma sprayed thermal barrier coatings  

Microsoft Academic Search

The specific permeability of oxygen in plasma sprayed zirconia has been measured to be approximately 10?16 m2, with some dependence on microstructure, and hence on spraying conditions. Permeability rises with increasing temperature, as expected, and differences of a factor of approximately 4 were observed between room temperature and 600 C. Maximum oxygen fluxes through the top coat via gas permeation,

A. C. Fox; T. W. Clyne

2004-01-01

302

Plasma Separation Process: Betacell (BCELL) code: User's manual. [Bipolar barrier junction  

Microsoft Academic Search

The emergence of clearly defined applications for (small or large) amounts of long-life and reliable power sources has given the design and production of betavoltaic systems a new life. Moreover, because of the availability of the plasma separation program, (PSP) at TRW, it is now possible to separate the most desirable radioisotopes for betacell power generating devices. A computer code,

Taherzadeh

1987-01-01

303

Series Elastic Actuators  

E-print Network

This thesis presents the design, construction, control and evaluation of a novel force controlled actuator. Traditional force controlled actuators are designed from the premise that "Stiffer is better''. This approach ...

Williamson, Matthew M.

1995-09-07

304

Micromachined electrostatic vertical actuator  

SciTech Connect

A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion, micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.

Lee, A.P.; Sommargren, G.E.; McConaghy, C.F.; Krulevitch, P.A.

1999-10-19

305

Micromachined electrostatic vertical actuator  

DOEpatents

A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion` micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.

Lee, Abraham P. (Walnut Creek, CA); Sommargren, Gary E. (Santa Cruz, CA); McConaghy, Charles F. (Livermore, CA); Krulevitch, Peter A. (Pleasanton, CA)

1999-10-19

306

Damage Accumulation and Failure of Plasma-Sprayed Thermal Barrier Coatings under Thermal Gradient Cyclic Conditions  

NASA Technical Reports Server (NTRS)

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. A fundamental understanding of the sintering and thermal cycling induced delamination of thermal barrier coating systems under engine-like heat flux conditions will potentially help to improve the coating temperature capability. In this study, a test approach is established to emphasize the real-time monitoring and assessment of the coating thermal conductivity, which can initially increase under the steady-state high temperature thermal gradient test due to coating sintering, and later decrease under the thermal gradient cyclic test due to coating cracking and delamination. Thermal conductivity prediction models have been established for a ZrO2-(7- 8wt%)Y2O3 model coating system in terms of heat flux, time, and testing temperatures. The coating delamination accumulation is then assessed based on the observed thermal conductivity response under the combined steady-state and cyclic thermal gradient tests. The coating thermal gradient cycling associated delaminations and failure mechanisms under simulated engine heat-flux conditions will be discussed in conjunction with the coating sintering and fracture testing results.

Zhu, Dongming; Choi, Sung R.; Ghosn, Louis J.; Miller, rober A.

2005-01-01

307

Characterization and Application of a Planar Radio - Inductively-Coupled Plasma Source for the Production of Barrier Coatings.  

NASA Astrophysics Data System (ADS)

A planar radio-frequency (rf) inductively-coupled plasma (ICP) source is used to produce fluorocarbon discharges (CF_4/Ar) to fluorinate the surface of high-density polyethylene (HDPE). Using this system, concurrent studies of discharge characteristics, permeation properties of treated polymers and polymer surface characteristics are conducted to advance the use of plasma-fluorinated polymer surfaces as a barrier layer for automotive applications. Langmuir probes are used to determine spatial distribution of charged-particle and space-potential characteristics in Ar and CF_4/Ar discharges and to show the influence of the spatial distribution of the heating regions and the reactor boundaries on the discharge uniformity. Langmuir probes are also used to identify rf anisotropic drift motion of electrons in the heating regions of the source and transient high-energy electron features in pulsed discharges. These latter features allow pulsed ICP sources to be operated at low time-averaged powers that are necessary to treat thermally sensitive polymers. Fourier Transform Infrared (FITR) spectroscopy is used to measure the dissociation of fluorocarbon gases and to explore differences between pulsed- and continuous -power operation. Dissociation levels of CF_4 (50-85%) using pulsed-power operation are as high as that for continuous operation, even though the net time -averaged power is far less with pulsed operation. The result suggests that pulsed fluorocarbon discharges possess high concentrations of chemically-active species needed for rapid surface fluorination. A gravimetric permeation cup method is used to measure the permeation rate of test fuels through HDPE membranes, and electron spectroscopy for chemical analysis (ESCA) studies are performed to determine the stoichiometry and thickness of the barrier layer. From these studies we find that a 50-70 A thick, polar, fluoro-hydrocarbon over layer reduces the permeation of isooctane/toluene/methanol mixtures by a factor of 4. To increase the permeation resistance for automotive applications, this result points towards the deposition of a 1000 A thick fluoro-hydrocarbon barrier coating with stoichiometry and bond structures similar to the CF_4/Ar treated HDPE.

Mahoney, Leonard Joseph

308

Electromagnetic rotational actuation.  

SciTech Connect

There are many applications that need a meso-scale rotational actuator. These applications have been left by the wayside because of the lack of actuation at this scale. Sandia National Laboratories has many unique fabrication technologies that could be used to create an electromagnetic actuator at this scale. There are also many designs to be explored. In this internship exploration of the designs and fabrications technologies to find an inexpensive design that can be used for prototyping the electromagnetic rotational actuator.

Hogan, Alexander Lee

2010-08-01

309

COMPARISON OF THERMAL PROPERTIES OF THERMAL BARRIER COATING DEPOSITED ON IN738 USING STANDARD AIR PLASMA SPRAY WITH 100HE PLASMA SPRAY SYSTEM  

SciTech Connect

A typical blade material is made of Nickel super alloy and can bear temperatures up to 950C. But the operating temperature of a gas turbine is above the melting point of super alloy nearly at 1500C. This could lead to hot corrosions, high temperature oxidation, creep, thermal fatigue may takes place on the blade material. Though the turbine has an internal cooling system, the cooling is not adequate to reduce the temperature of the blade substrate. Therefore to protect the blade material as well as increase the efficiency of the turbine, thermal barrier coatings (TBCs) must be used. A TBC coating of 250 ?m thick can reduce the temperature by up to 200 C. Air Plasma Spray Process (APS) and High Enthalpy Plasma Spray Process (100HE) were the processes used for coating the blades with the TBCs. Because thermal conductivity increases with increase in temperature, it is desired that these processes yield very low thermal conductivities at high temperatures in order not to damage the blade. An experiment was carried out using Flash line 5000 apparatus to compare the thermal conductivity of both processes.The apparatus could also be used to determine the thermal diffusivity and specific heat of the TBCs. 75 to 2800 K was the temperature range used in the experimentation. It was found out that though 100HE has high deposition efficiency, the thermal conductivity increases with increase in temperatures whiles APS yielded low thermal conductivities.

Uppu, N.; Mensah, P.F.; Ofori, D.

2006-07-01

310

Microstructure and thermal conductivity of thermal barrier coatings processed by plasma spray and physical vapor deposition techniques  

SciTech Connect

Improvements in the efficiency of gas turbine require the highest operating temperatures possible. Because the Ni-base superalloys used as turbine materials rapidly lose strength and oxidize above 1,000 C, a reduction in service temperature is often accomplished by the use of thermal barrier coatings. The temperature dependence of the thermal conductivity of multilayer coatings made by a plasma spray technique as well as some coatings made by physical vapor deposition (PVD) was investigated. The multilayer coatings consisted of a varying number of layers of Al{sub 2}O{sub 3} and ZrO{sub 2} stabilized by 8% Y{sub 2}O{sub 3}. Plasma sprayed coatings exhibited a large reduction in thermal conductivity at all temperatures when compared to the bulk monolithic materials. This reduction was found to be due to porosity as well as thermal resistance brought about by interfaces in the coatings. A comparable reduction in thermal conductivity was achieved in monolithic ZrO{sub 2} as well as in a composite coating deposited by the PVD technique. Microstructural factors that may be responsible for this reduction are discussed.

Ravichandran, K.S.; An, K. [Univ. of Utah, Salt Lake City, UT (United States). Dept. of Metallurgical Engineering; Dutton, R.E.; Semiatin, S.L. [Wright Lab., Wright Patterson AFB, OH (United States). Materials Directorate

1996-12-31

311

Electrical Servo Actuator Bracket.  

National Technical Information Service (NTIS)

A bracket for an electrical servo actuator is disclosed which was developed particularly for jet engine fuel control values. Said servo actuator is mounted on a support arm which is allowed to pivot on a bolt through a fixed mounting bracket. The actuator...

R. V. Sawyer

1980-01-01

312

Folded dielectric elastomer actuators  

Microsoft Academic Search

Polymer-based linear actuators with contractile ability are currently demanded for several types of applications. Within the class of dielectric elastomer actuators, two basic configurations are available today for such a purpose: the multi-layer stack and the helical structure. The first consists of several layers of elementary planar actuators stacked in series mechanically and parallel electrically. The second configuration relies on

Federico Carpi; Claudio Salaris; Danilo DeRossi

2007-01-01

313

Dual drive actuators  

NASA Technical Reports Server (NTRS)

A new class of electromechanical actuators is described. These dual drive actuators were developed for the NASA-JPL Galileo Spacecraft. The dual drive actuators are fully redundant and therefore have high inherent reliability. They can be used for a variety of tasks, and they can be fabricated quickly and economically.

Packard, D. T.

1982-01-01

314

Effect of heat treatment on the thermal conductivity of plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

The effect of heat treatment on the thermal conductivity of plasma-sprayed Y2O3 stabilized ZrO2 (YSZ) and Al2O3 coatings was investigated. A heat treatment of 1300 C in flowing argon for 50 h was found to significantly increase the\\u000a thermal conductivity of the coatings when compared to measurements in the assprayed condition. Transmission electron microscopy\\u000a (TEM) examination of the microstructures of

Rollie Dutton; Robert Wheeler; K. S. Ravichandran; K. An

2000-01-01

315

Gas barrier properties of silicon oxide films prepared by plasma-enhanced CVD using tetramethoxysilane  

Microsoft Academic Search

Silicon oxide films were deposited by means of capacitively coupled RF plasma-enhanced CVD using a mixture of tetramethoxysilane and oxygen as source. Chemical compositions and bonding states of the deposited films were analyzed by FTIR and XPS. The absorption bands due to SiCH3, SiH and SiOH in the FTIR spectra became markedly smaller when the RF power and the fraction

K Teshima; Y Inoue; H Sugimura; O Takai

2002-01-01

316

An analytical model for simulation of heat flow in plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

Numerical (finite difference) and analytical models have been developed for the simulation of heat flow through plasma-sprayed\\u000a coatings, allowing the effective thermal conductivity to be predicted as a function of microstructural parameters. The structure\\u000a is assumed to be composed of lamellar material (splats), separated by (thin) pores, within which there are areas of contact\\u000a (bridges). The analytical model is based

I. O. Golosnoy; S. A. Tsipas; T. W. Clyne

2005-01-01

317

High Temperature Damping Behavior of Plasma-Sprayed Thermal Barrier and Protective Coatings  

NASA Technical Reports Server (NTRS)

A high temperature damping test apparatus has been developed using a high heat flux CO 2 laser rig in conjunction with a TIRA S540 25 kHz Shaker and Polytec OFV 5000 Vibrometer system. The test rig has been successfully used to determine the damping performance of metallic and ceramic protective coating systems at high temperature for turbine engine applications. The initial work has been primarily focused on the microstructure and processing effects on the coating temperature-dependence damping behavior. Advanced ceramic coatings, including multicomponent tetragonal and cubic phase thermal barrier coatings, along with composite bond coats, have also been investigated. The coating high temperature damping mechanisms will also be discussed.

Zhu, Dongming; Miller, Robert A.; Duffy, Kirsten P.; Ghosn, Louis J.

2010-01-01

318

Finite Element Modeling of the Different Failure Mechanisms of a Plasma Sprayed Thermal Barrier Coatings System  

NASA Astrophysics Data System (ADS)

A new finite element model is used to investigate catastrophic failures of a thermal barrier coatings system due to crack propagation along the interfaces between the ceramic top-coat, thermally grown oxide, and bond-coat layers, as well as between the lamellas structure of the ceramic layer. The thermo-mechanical model is designed to take into account a non-homogenous temperature distribution and the effects of the residual stresses generated during the coating process. Crack propagation is simulated using the contact tool "Debond" present in the ABAQUS finite element code. Simulations are performed with a geometry corresponding to similar or dissimilar amplitudes of asperity, and for different thicknesses of the oxide layer. The numerical results have shown that crack evolution depends crucially on the ratio of the loading rate caused by growth and swelling of the oxide layer and also on the interface roughness obtained during the spraying of coatings.

Ranjbar-Far, M.; Absi, J.; Mariaux, G.

2012-12-01

319

Electron and Ion Channel Transport Barriers: Initiation and Dynamical Co-evolution and their implications for burning plasmas  

NASA Astrophysics Data System (ADS)

Simple dynamical models have been able to capture much of the dynamics of the transport barriers found in many devices, however an open question has been the often disconnected nature of the electron thermal transport channel sometimes observed in the presence of a standard (``ion channel'') barrier. By adding to a simple barrier model an evolution equation for electron fluctuations we can investigate the interaction between the formation of the standard ion channel barrier and the somewhat less common electron channel barrier. Barrier formation in the electron channel is even more sensitive to the alignment of the various gradients making up the sheared radial electric field then the ion barrier is. Electron channel heat transport is found to significantly increase after the formation of the ion channel barrier but before the electron channel barrier is formed. This increased transport is important in the barrier evolution. Parameters relevant to ITER like devices will be investigated.

Newman, D. E.; Terry, P. W.; Sanchez, R.

2012-10-01

320

Considerations for Contractile Electroactive Materials and Actuators  

SciTech Connect

Ras Labs produces contractile electroactive polymer (EAP) based materials and actuators that bend, swell, ripple, and contract (new development) with low electric input. In addition, Ras Labs produces EAP materials that quickly contract and expand, repeatedly, by reversing the polarity of the electric input, which can be cycled. This phenomenon was explored using molecular modeling, followed by experimentation. Applied voltage step functions were also investigated. High voltage steps followed by low voltage steps produced a larger contraction followed by a smaller contraction. Actuator control by simply adjusting the electric input is extremely useful for biomimetic applications. Muscles are able to partially contract. If muscles could only completely contract, nobody could hold an egg, for example, without breaking it. A combination of high and low voltage step functions could produce gross motor function and fine manipulation within the same actuator unit. Plasma treated electrodes with various geometries were investigated as a means of providing for more durable actuation.

Lenore Rasmussen, David Schramm, Paul Rasmussen, Kevin Mullaly, Ras Labs, LLC, Intelligent Materials for Prosthetics & Automation, Lewis D. Meixler, Daniel Pearlman and Alice Kirk

2011-05-23

321

Bimorphic polymeric photomechanical actuator  

NASA Technical Reports Server (NTRS)

A bimorphic polymeric photomechanical actuator, in one embodiment using polyvinylidene fluoride (PVDF) as a photosensitive body, transmitting light over fiber optic cables, and controlling the shape and pulse duration of the light pulse to control movement of the actuator. Multiple light beams are utilized to generate different ranges of motion for the actuator from a single photomechanical body and alternative designs use multiple light beams and multiple photomechanical bodies to provide controlled movement. Actuator movement using one or more ranges of motion is utilized to control motion to position an actuating element in three dimensional space.

Sarkisov, Sergey S. (Inventor); Curley, Michael J. (Inventor); Adamovsky, Grigory (Inventor); Sarkisov, Jr., Sergey S. (Inventor); Fields, Aisha B. (Inventor)

2006-01-01

322

Omnidirectional Actuator Handle  

NASA Technical Reports Server (NTRS)

Proposed actuator handle comprises two normally concentric rings, cables, and pulleys arranged such that relative displacement of rings from concentricity results in pulling of cable and consequent actuation of associated mechanism. Unlike conventional actuator handles like levers on farm implements, actuated from one or two directions only, proposed handle reached from almost any direction and actuated by pulling or pushing inner ring in any direction with respect to outer ring. Flanges installed on inner ring to cover gap between inner ring and housing to prevent clothing from being caught.

Moetteli, John B.

1995-01-01

323

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

PubMed Central

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 reliably predicted from measurement of partition coefficients. PMID:1324973

1992-01-01

324

Improved Electrohydraulic Linear Actuators  

NASA Technical Reports Server (NTRS)

A product line of improved electrohydraulic linear actuators has been developed. These actuators are designed especially for use in actuating valves in rocket-engine test facilities. They are also adaptable to similar industrial uses. The advantageous features of the improved electrohydraulic linear actuators are best described with respect to shortcomings of prior electrohydraulic linear actuators that the improved ones are intended to supplant. The shortcomings are the following: They perform unreliably and inconsistently as positioning devices. Their capabilities for end-of-stroke buffering (that is, deceleration to gentle stops at designated stopping positions) range from unsatisfactory to nonexistent, with consequent potential for inducing catastrophic failures. It takes long times to modify standard actuators to meet specifications, and the costs of such modifications are high. In the cases of actuators equipped with fail-safe shutdown systems, the stroking times of these systems cannot be adjusted in the field.

Hamtil, James; Selinsky, T.

2002-01-01

325

FLUIDS, PLASMAS AND ELECTRIC DISCHARGES: The influence of the structures and compounds of DLC coatings on the barrier properties of PET bottles  

NASA Astrophysics Data System (ADS)

To reduce the oxygen transmission rate through a polyethylene terephthalate (PET) bottle (an organic plastic) diamond-like carbon (DLC) coatings on the inner surface of the PET bottle were deposited by radio frequency plasma-enhanced chemical vapour deposition (RF-PECVD) technology with C2H2 as the source of carbon and Ar as the diluted gas. As the barrier layer to humidity and gas permeation, this paper analyses the DLC film structure, composition, morphology and barrier properties by Fourier transform infrared, atomic force microscopy, scanning electron microscopy and oxygen transmission rate in detail. From the spectrum, it is found that the DLC film mainly consists of sp3 bonds. The barrier property of the films is significantly relevant to the sp3 bond concentration in the coating, the film thickness and morphology. Additionally, it is found that DLC film deposited in an inductively coupled plasma enhanced capacitively coupled plasma source shows a compact, homogeneous and crack-free surface, which is beneficial for a good gas barrier property in PET bottles.

Yang, Li; Wang, Zhen-Duo; Zhang, Shou-Ye; Yang, Li-Zhen; Chen, Qiang

2009-12-01

326

Blood-nerve barrier: distribution of anionic sites on the endothelial plasma membrane and basal lamina.  

PubMed

The distribution of anionic sites on the cell membranes and basal laminae of vascular endothelial cells in the rat sciatic nerve was investigated using cationic ferritin (CF) and cationic colloidal gold (CCG). Nerves fixed by perfusion followed by immersion were chopped into 400 microns thick slices and incubated in CF or embedded in LR White resin for staining with CCG. Using electron microscopy, the distribution of these tracers was investigated. The results indicated that microdomains of various charge densities exist. Diaphragms of caveolae and transendothelial channels, and luminal endothelial processes are highly anionic, the basal laminae of endothelial cells and pericytes and luminal membranes are medium and abluminal membranes least anionic. Inter-endothelial tight junctions were unlabelled and not penetrated by CF. These structures are thought to represent charge and size filters that control permeability of the vasa nervorum. The distribution of these charge-size filters is discussed in terms of the blood-nerve barrier, a physiological property present in the endo- but absent in the peri- and epineurial vessels. PMID:1705854

Bush, M S; Allt, G

1990-12-10

327

Impact of temperature increments on tunneling barrier height and effective electron mass for plasma nitrided thin SiO{sub 2} layer on a large wafer area  

SciTech Connect

Thermally grown SiO{sub 2} layers were treated by a plasma nitridation process realized in a vertical furnace. The combination of a pulsed-low frequency plasma and a microwave remote plasma with N{sub 2}/NH{sub 3}/He feed gas mixture was used to nitride the thermally grown SiO{sub 2} gate dielectrics of MIS structures. Temperature dependency of effective masses and the barrier heights for electrons in pure thermally grown SiO{sub 2} as well as plasma nitrided SiO{sub 2} in high electric field by means of Fowler-Nordheim regime was determined. It is frequently seen from the literature that either effective electron mass or barrier height (generally effective electron mass) is assumed to be a constant and, as a result, the second parameter is calculated under the chosen assumption. However, in contrast to general attitude of previous studies, this work does not make any such assumptions for the calculation of neither of these two important parameters of an oxide at temperature ranges from 23 to 110 deg. C for SiO{sub 2}, and 23 to 130 deg. C for nitrided oxide. It is also shown here that both parameters are affected from the temperature changes; respectively, the barrier height decreases while the effective mass increases as a result of elevated temperature in both pure SiO{sub 2} and plasma nitrided SiO{sub 2}. Therefore, one parameter could be miscalculated if the other parameter, i.e., effective mass of electron, was assumed to be a constant with respect to variable physical conditions like changing temperature. Additionally, the barrier heights were calculated just by taking constant effective masses for both types of oxides to be able to compare our results to common literature values.

Aygun, G. [Fraunhofer IISB, Schottkystrasse 10, 91058 Erlangen (Germany); Department of Physics, Izmir Institute of Technology, TR-35430 Urla, Izmir (Turkey); Roeder, G.; Erlbacher, T.; Wolf, M.; Schellenberger, M.; Pfitzner, L. [Fraunhofer IISB, Schottkystrasse 10, 91058 Erlangen (Germany)

2010-10-15

328

New Formation Technology of Plasma Display Panel Barrier-Rib Structure Using Silicone Rubber Mold Transferred from SU-8 Master Structure  

NASA Astrophysics Data System (ADS)

A new formation technology for a plasma display panel (PDP) barrier-rib structure is presented to realize a barrier rib with a high aspect ratio and reduce the manufacturing cost. In this study, we used an SU-8 50 photoresist, which is sensitive to UV irradiation, instead of polymethylmethacrylate (PMMA) which is sensitive to X-ray irradiation, so that the silicone rubber mold could be applicable to a large-area PDP. The first step is to produce an SU-8 master structure using amorphous silicon as an adhesion layer between a glass substrate and SU-8 photoresist. Second, a precise soft mold is manufactured for mass replication of the PDP barrier-rib construction, by molding liquid silicone rubber onto the glass substrate with lithographically defined SU-8 master structures. Third, a PDP barrier-rib structure is formed using the pattern-transferring process with a reusable silicone rubber mold. This is a very simple and inexpensive process consisting with printing of barrier-rib paste, drying, pattern-transferring, and sintering. The pattern-transferring process with a soft mold also demonstrates that the disadvantages of the conventional mold pressing process with a hard mold can be overcome. Consequently, by using the pattern-transferring process with the silicone rubber mold transferred from the SU-8 master structure, the desired barrier-rib shapes can be realized with a high aspect ratio and various dimensions.

Son, Seung-Hyun; Park, Yong-Suk; Choi, Sie-Young

2002-06-01

329

Multi-scale modelling of pulsed nanosecond dielectric barrier plasma discharges in plane-to-plane geometry  

NASA Astrophysics Data System (ADS)

An integrated theoretical and numerical framework is developed to study the dynamics of energy coupling, gas heating and generation of active species by repetitively pulsed nanosecond dielectric barrier discharges (NS DBDs) in air. The work represents one of the first attempts to simulate, in a self-consistent manner, multiple (more than 100) nanosecond pulses. Detailed information is obtained about the electric-field transients during each voltage pulse, and accumulation of plasma generated species and gas heating over ms timescales. The plasma is modelled using a two-temperature, detailed chemistry scheme, with ions and neutral species in thermal equilibrium at the gas temperature, and electrons in thermal nonequilibrium. The analysis is conducted with pressures and pulsing frequency in the range 40-100 Torr and 1-105 Hz, respectively. The input electrical energy is directly proportional to the number density, and remains fairly constant on a per molecule basis from pulse to pulse. Repetitive pulsing results in uniform production of atomic oxygen in the discharge volume via electron-impact dissociation during voltage pulses, and through quenching of excited nitrogen molecules in the afterglow. The ion Joule effect causes rapid gas heating of 40 K/pulse in the cathode sheath and generates weak acoustic waves. Conductive heat loss to the walls during the time interval between voltage pulses prevents overheating of the cathode layer and development of ionization instabilities. A uniform hat-shaped temperature profile develops in the discharge volume after multiple pulses, due to chemical heat release from quenching of excited species. This finding may explain experimentally observed volumetric ignition (as opposed to hot-spot ignition) in fuel-air mixtures subject to NS DBD.

Nagaraja, Sharath; Yang, Vigor; Adamovich, Igor

2013-04-01

330

Effects of driving voltage frequency on the discharge characteristics of atmospheric dielectric-barrier-discharge plasma jet  

NASA Astrophysics Data System (ADS)

We present here the analysis of the discharge characteristics of a He dielectric-barrier-discharge (DBD) plasma jet operated in the frequency range of 0.6 to 30 kHz under an open-air condition. Discharge strength is sensitive to driving voltage frequency, and an increasing driving frequency induces a weak pulse discharge with a small plume length. We also performed time-resolved optical emission measurements in a transient pulse discharge driven by various voltage frequencies. A strong optical emission from O atoms is observed near the quartz-tube outlet at a low driving voltage frequency of about 5 kHz, where more than 90% of the total O emission intensity is detected in the after-discharge period. The observations indicate that low-frequency discharge operation can generate a large number of reactive excited O atoms near the quartz-tube outlet, and this is ascribed to the chemical reactions in the after-discharge period.

Uchida, Giichiro; Takenaka, Kosuke; Kawabata, Kazufumi; Miyazaki, Atsushi; Setsuhara, Yuichi

2014-11-01

331

Analysis of Plasma-Sprayed Thermal Barrier Coatings With Homogeneous and Heterogeneous Bond Coats Under Spatially Uniform Cyclic Thermal Loading  

NASA Technical Reports Server (NTRS)

This report summarizes the results of a numerical investigation into the spallation mechanism in plasma-sprayed thermal barrier coatings observed under spatially-uniform cyclic thermal loading. The analysis focuses on the evolution of local stress and inelastic strain fields in the vicinity of the rough top/bond coat interface during thermal cycling, and how these fields are influenced by the presence of an oxide film and spatially uniform and graded distributions of alumina particles in the metallic bond coat aimed at reducing the top/bond coat thermal expansion mismatch. The impact of these factors on the potential growth of a local horizontal delamination at the rough interface's crest is included. The analysis is conducted using the Higher-Order Theory for Functionally Graded Materials with creep/relaxation constituent modeling capabilities. For two-phase bond coat microstructures, both the actual and homogenized properties are employed in the analysis. The results reveal the important contributions of both the normal and shear stress components to the delamination growth potential in the presence of an oxide film, and suggest mixed-mode crack propagation. The use of bond coats with uniform or graded microstructures is shown to increase the potential for delamination growth by increasing the magnitude of the crack-tip shear stress component.

Arnold, Steven M.; Pindera, Marek-Jerzy; Aboudi, Jacob

2003-01-01

332

Thermal Shock Behavior of Air Plasma Sprayed CoNiCrAlY/YSZ Thermal Barrier Coatings  

NASA Astrophysics Data System (ADS)

The structural changes and failure mechanism of thermal barrier coatings (TBCs) during thermal shock cycling were investigated. TBCs consisting of CoNiCrAlY bond coat and partially yttria-stabilized zirconia (YSZ) top coat were deposited by atmospheric plasma spraying (APS) on a nickel-based alloy substrate and its thermal shock resistance performance was evaluated. TBCs were heated at 1100C for 15 min followed by cold water quenching to ambient temperature. Microstructural evaluation and elemental analysis of TBCs were performed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), respectively. The crack features of YSZ coatings in TBCs during thermal shock cycling, including those of horizontal (parallel to the substrate) and vertical cracks (perpendicular to the substrate), were particularly investigated by means of SEM and image analysis. Results show that horizontal and vertical cracks have different influences on the thermal shock resistance of the coatings. Horizontal cracks that occur at the interface of YSZ and thermally growth oxidation (TGO) cause partial or large-area spalling of coatings. When vertical and horizontal cracks encounter, network segments are formed which lead to partial spalling of the coatings.

Liu, Zi Wei; Wu, Wei; Hua, Jia Jie; Lin, Chu Cheng; Zheng, Xue Bin; Zeng, Yi

2014-07-01

333

New formation technology for a plasma display panel barrier-rib structure using a precise metal mold fabricated by the UV-LIGA process  

NASA Astrophysics Data System (ADS)

We present a new formation technology for a plasma display panel (PDP) barrier-rib structure by which we can obtain a barrier-rib with a high aspect ratio and reduce the manufacturing cost. Firstly, a precise metal mould is manufactured for massively replicating the PDP barrier-rib construction using the UV-LIGA process with a thick negative photoresist (SU-8 50: Microchem Corp). The proposed sequence includes several processes: amorphous silicon as an adhesion layer; dipping into xylene and n-butyl acetate after the development of SU-8; two step removal of the SU-8 layer; rip-off process, etc. The proposed processes produce a copper mould with a high aspect ratio, good surface roughness and a uniform thickness. Secondly, a PDP barrier-rib structure is formed using the roll-pressing method with a reusable metal mould fabricated by the proposed UV-LIGA process. This is a very simple and inexpensive method consisting of printing the barrier-rib paste, drying, roll-pressing and firing. Consequently, by combining the UV-LIGA and roll-pressing processes, the desired barrier-rib shapes can be made with a high aspect ratio and various dimensions. The combination of the UV-LIGA and roll-pressing processes also demonstrates the possibility of achieving two major goals in the barrier-rib processes; i.e., developing a barrier-rib structure with a high aspect ratio that can be applied to high-definition televisions, and reducing the manufacturing cost.

Son, Seung-Hyun; Park, Yong-Suk; Choi, Sie-Young

2002-01-01

334

MEMS fluidic actuator  

SciTech Connect

The present invention comprises a novel, lightweight, massively parallel device comprising microelectromechanical (MEMS) fluidic actuators, to reconfigure the profile, of a surface. Each microfluidic actuator comprises an independent bladder that can act as both a sensor and an actuator. A MEMS sensor, and a MEMS valve within each microfluidic actuator, operate cooperatively to monitor the fluid within each bladder, and regulate the flow of the fluid entering and exiting each bladder. When adjacently spaced in a array, microfluidic actuators can create arbitrary surface profiles in response to a change in the operating environment of the surface. In an embodiment of the invention, the profile of an airfoil is controlled by independent extension and contraction of a plurality of actuators, that operate to displace a compliant cover.

Kholwadwala, Deepesh K. (Albuquerque, NM); Johnston, Gabriel A. (Trophy Club, TX); Rohrer, Brandon R. (Albuquerque, NM); Galambos, Paul C. (Albuquerque, NM); Okandan, Murat (Albuquerque, NM)

2007-07-24

335

Atmospheric pressure plasma produced inside a closed package by a dielectric barrier discharge in Ar/CO2 for bacterial inactivation of biological samples  

NASA Astrophysics Data System (ADS)

The generation and evaluation of a dielectric barrier discharge produced inside a closed package made of a commercially available packaging film and filled with gas mixtures of Ar/CO2 at atmospheric pressure is reported. The discharge parameters were analysed by electrical measurements and optical emission spectroscopy in two modes of operation: trapped gas atmosphere and flowing gas atmosphere. Gas temperature was estimated using the OH(A-X) emission spectrum and the rotational temperature reached a saturation level after a few minutes of plasma running. The rotational temperature was almost three times higher in the Ar/CO2 plasma compared with an Ar plasma. The efficiency of the produced plasma for the inactivation of bacteria on food inside the closed package was investigated.

Chiper, A. S.; Chen, W.; Mejlholm, O.; Dalgaard, P.; Stamate, E.

2011-04-01

336

Sensors and Actuators  

NSDL National Science Digital Library

Sensors and Actuators A (SAAA) disseminates "...information on all aspects of research and development of solid-state devices for transducing physical signals." Sensors and Actuators B (SAAB) "...is an interdisciplinary journal dedicated to covering research and development in the field of chemical sensors, actuators and microsystems." Issues of SAAA available range from September 1999 to the present; issues of SAAB cover January 2000-present.

2001-01-01

337

Modeling piezoelectric actuators  

Microsoft Academic Search

The piezoelectric actuator (PEA) is a well-known device for managing extremely small displacements in the range from 10 pm to 100 ?m. When developing a control system for a piezo-actuated positioning mechanism, the actuator dynamics have to be taken into account. An electromechanical piezo model, based on physical principles, is presented in this paper. In this model, a first-order differential

H. J. M. T. S. Adriaens; W. L. De Koning; R. Banning

2000-01-01

338

Improved Electrohydraulic Linear Actuators  

NASA Technical Reports Server (NTRS)

A product line of improved electrohydraulic linear actuators has been developed. These actuators are designed especially for use in actuating valves in rocket-engine test facilities. They are also adaptable to many industrial uses, such as steam turbines, process control valves, dampers, motion control, etc. The advantageous features of the improved electrohydraulic linear actuators are best described with respect to shortcomings of prior electrohydraulic linear actuators that the improved ones are intended to supplant. The flow of hydraulic fluid to the two ports of the actuator cylinder is controlled by a servo valve that is controlled by a signal from a servo amplifier that, in turn, receives an analog position-command signal (a current having a value between 4 and 20 mA) from a supervisory control system of the facility. As the position command changes, the servo valve shifts, causing a greater flow of hydraulic fluid to one side of the cylinder and thereby causing the actuator piston to move to extend or retract a piston rod from the actuator body. A linear variable differential transformer (LVDT) directly linked to the piston provides a position-feedback signal, which is compared with the position-command signal in the servo amplifier. When the position-feedback and position-command signals match, the servo valve moves to its null position, in which it holds the actuator piston at a steady position.

Hamtil, James

2004-01-01

339

Microstructures and Properties of Laser-Glazed Plasma-Sprayed ZrO 2 YO 1.5 \\/Ni22Cr10AI1Y Thermal Barrier Coatings  

Microsoft Academic Search

Thermal barrier coatings (TBCs) consisting of two layers with various yttria contents (ZrO\\u000a 2- YO1.5\\/Ni-22Cr-10Al- lY) were plasma sprayed, and parts of the various specimens were glazed by using a pulsed CO2 laser. All the specimens were then subjected to furnace thermal cycling tests at 1100 C; the effect of laser glazing on\\u000a the durability and failure mechanism of the

H. L. Tsai; P. C Tsai

1995-01-01

340

The modeling of coating thickness, heat transfer, and fluid flow and its correlation with the thermal barrier coating microstructure for a plasma sprayed gas turbine application  

Microsoft Academic Search

The plasma sprya deposition of a zirconia thermal barrier coating (TBC) on a gas turbine component was examined using analytical\\u000a and experimental techniques. The coating thickness was simulated by the use of commercial off-line software. The impinging\\u000a jet was modeled by means of a finite difference elliptic code using a simplified turbulence model. Powder particle velocity,\\u000a temperature history, and trajectory

P. Nyln; J. Wigren; L. Pejryd; M.-O. Hansson

1999-01-01

341

Microstructures and properties of laser-glazed plasma-sprayed ZrO-YO{sub 1.5}\\/Ni22Cr10Al1Y thermal barrier coatings  

Microsoft Academic Search

Thermal barrier coatings (TBCs) consisting of two layers with various yttria contents (ZrO-YO{sub 1.5}\\/Ni-22Cr-10Al-1Y) were plasma sprayed, and parts of the various specimens were glazed by using a pulsed CO laser. All the specimens were then subjected to furnace thermal cycling tests at 1,100 C; the effect of laser glazing on the durability and failure mechanism of the TBCs was

H. L. Tsai; P. C. Tsai

1995-01-01

342

Microstructures and Properties of Laser-Glazed Plasma-Sprayed ZrO2YO1.5\\/Ni22Cr10AI1Y Thermal Barrier Coatings  

Microsoft Academic Search

Thermal barrier coatings (TBCs) consisting of two layers with various yttria contents (ZrO 2- YO1.5\\/Ni-22Cr-10Al- lY) were plasma sprayed, and parts of the various specimens were glazed by using a pulsed CO2 laser. All the specimens were then subjected to furnace thermal cycling tests at 1100 C; the effect of laser glazing on the durability and failure mechanism of the

H. L. Tsai; P. C. Tsai

1995-01-01

343

Thermal fatigue behavior of thermal barrier coatings with the MCrAlY bond coats by cold spraying and low-pressure plasma spraying  

Microsoft Academic Search

The thermal fatigue behavior of thermal barrier coatings (TBCs) with the NiCoCrAlTaY bond coats deposited by cold spraying and low-pressure plasma spraying (LPPS) was examined through thermal cyclic test. The TBCs were subjected to the pre-oxidation before the test in an Ar atmosphere. The results show that a more uniform TGO in both thickness and composition forms on the cold-sprayed

Yong Li; Chang-Jiu Li; Guan-Jun Yang; Lu-Kuo Xing

2010-01-01

344

Effect of Coating Process Condition on High-Temperature Oxidation and Mechanical Failure Behavior for Plasma Sprayed Thermal Barrier Coating Systems  

Microsoft Academic Search

In order to clarify the thermal and\\/or mechanical failure behavior of the plasma sprayed thermal barrier coating (TBC) system in connection with their coating characteristics depending on the coating process condition, two kinds of the failure analytical tests were conducted for TBC systems processed under different conditions. One was the high-temperature oxidation test, which was conducted at 1100C under both

Satoru Takahashi; Masayuki Yoshiba; Yoshio Harada

2008-01-01

345

Smart Material-Actuated Rotor Technology SMART  

Microsoft Academic Search

Vibration, noise, and aerodynamic design compromises are primary barriers to further improvements in effectiveness of the helicopter. The MD900 light utility helicopter main rotor system is modified to include in-blade smart material actuation for active control. A piezoelectric (PE)-driven trailing edge flap is used for vibration, noise, and aerodynamic performance improvements. A shape memory alloy (SMA)-driven trailing edge trim tab

Friedrich K. Straub; Dennis K. Kennedy; David B. Domzalski; Ahmed A. Hassan; Hieu Ngo; V. Anand; Terry Birchette

2004-01-01

346

Treatment surfaces with atomic oxygen excited in dielectric barrier discharge plasma of O{sub 2} admixed to N{sub 2}  

SciTech Connect

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.

Shun'ko, E. V.; Belkin, V. S. [WINTEK Electro-Optics Corporation, 1665 Highland Dr., Ann Arbor, Michigan 48108 (United States)

2012-06-15

347

Design of infection-resistant antibiotic-releasing polymers. II. Controlled release of antibiotics through a plasma-deposited thin film barrier.  

PubMed

In the first paper in this series, we described the methods to synthesize an antibacterial polyurethane (PU) incorporating ciprofloxacin as the releasable antibiotic and poly(ethylene glycol) as the pore-forming agent. Here, we report that a thin, RF-plasma-deposited, n-butyl methacrylate (BMA) overlayer on this drug-loaded PU can act as a rate-limiting barrier to achieve a constant, sustained release of ciprofloxacin. Deposition power and deposition time during the coating process were optimized to give an appropriate crosslinked coating barrier that yielded desirable release rates, above the minimum required killing rate, N(kill). Electron spectroscopy for chemical analysis (ESCA), also known as X-ray photoelectron spectroscopy (XPS), was used to characterize the coating, and its crosslinking degree was indirectly related to the C/O ratio. Increasing either deposition power (10-60 W) or duration (5-25 min) resulted in increased C/O ratios and decreased ciprofloxacin release rates. The correlation between increased C/O ratios and reduced release rates is believed to be due to the increased crosslinking, increased hydrophobicity and increased thickness of the coating. The optimal plasma conditions to attain an appropriate crosslinked plasma-deposited film (PDF) required argon etching, pre-treatment of the matrices with an 80W-BMA plasma for 1 min, followed by immediate BMA plasma deposition at 40 W and 150 mT for 20 min. By using these plasma deposition protocols, we eliminated the initial burst effect, significantly reduced the release rates, and closely approached the zero order release kinetics for at least five days. In this study, we also showed that ESCA could be used as a powerful tool to explain the release behavior of molecules through the plasma-deposited films (PDFs). PMID:10528068

Kwok, C S; Horbett, T A; Ratner, B D

1999-12-01

348

Helical dielectric elastomer actuators  

Microsoft Academic Search

This paper presents a new type of contractile polymer-based electromechanical linear actuator. The device belongs to the class of dielectric elastomer actuators, which are typically capable of undergoing large deformations induced by an applied electric field. It is based on a novel helical configuration, suitable for the generation of electrically driven axial contractions and radial expansions. The architecture, the principle

Federico Carpi; Antonio Migliore; Giorgio Serra; Danilo DeRossi

2005-01-01

349

Carbon Nanotube Actuators  

NASA Astrophysics Data System (ADS)

We have demonstrated a new type of electromechanical actuator, which is based on both a new type of actuator material (single-wall carbon nanotubes) and a new type of actuation mechanism (double-layer charge injection). Like natural muscles, the macroscopic actuators are assemblies of billions of individual nanoscale actuators. Higher stress generation capabilities than natural muscles and higher strains than high modulus ceramics were obtained in investigations of both all-solid-state and liquid-electrolyte-based devices. Evidence of giant charge injection is provided by in-situ measurements of electrochemical voltametry and Raman, UV-visible, and impedance spectroscopies. The results of ab initio quantum chemical calculations show that actuation arises from bond length changes that principally originate from quantum chemical effects, rather than electrostatic effects. Based on analysis of measurements, we conclude that nanotube actuators will eventually provide much higher specific work capacities and stress generation capabilities than alternative technologies, while operating at an order of magnitude lower voltages than ferroelectrics. We have demonstrated device operation to above 650 K, and conclude (based on observations of redox stability) that actuator operation to above 1300 K will eventually be feasible.

Baughman, Ray H.

2000-03-01

350

Self-actuated device  

DOEpatents

A self-actuated device, of particular use as a valve or an orifice for nuclear reactor fuel and blanket assemblies, in which a gas produced by a neutron induced nuclear reaction gradually accumulates as a function of neutron fluence. The gas pressure increase occasioned by such accumulation of gas is used to actuate the device.

Hecht, Samuel L. (Richland, WA)

1984-01-01

351

Determination of Scattering and Absorption Coefficients for Plasma-Sprayed Yttria-Stabilized Zirconia Thermal Barrier Coatings at Elevated Temperatures  

NASA Technical Reports Server (NTRS)

The temperature dependence of the scattering and absorption coefficients for a set of freestanding plasma-sprayed 8 wt% yttria-stabilized zirconia (8YSZ) thermal barrier coatings (TBCs) was determined at temperatures up to 1360 C in a wavelength range from 1.2 micrometers up to the 8YSZ absorption edge. The scattering and absorption coefficients were determined by fitting the directional-hemispherical reflectance and transmittance values calculated by a four-flux Kubelka Munk method to the experimentally measured hemispherical-directional reflectance and transmittance values obtained for five 8YSZ thicknesses. The scattering coefficient exhibited a continuous decrease with increasing wavelength and showed no significant temperature dependence. The scattering is primarily attributed to the relatively temperature-insensitive refractive index mismatch between the 8YSZ and its internal voids. The absorption coefficient was very low (less than 1 per centimeter) at wavelengths between 2 micrometers and the absorption edge and showed a definite temperature dependence that consisted of a shift of the absorption edge to shorter wavelengths and an increase in the weak absorption below the absorption edge with increasing temperature. The shift in the absorption edge with temperature is attributed to strongly temperature-dependent multiphonon absorption. While TBC hemispherical transmittance beyond the absorption edge can be predicted by a simple exponential decrease with thickness, below the absorption edge, typical TBC thicknesses are well below the thickness range where a simple exponential decrease in hemispherical transmittance with TBC thickness is expected. [Correction added after online publication August 11, 2009: "edge to a shorter wavelengths" has been updated as edge to shorter wavelengths."

Eldridge, Jeffrey I.; Spuckler, Charles M.; Markham, James R.

2009-01-01

352

Focal adhesion kinase controls pH-dependent epidermal barrier homeostasis by regulating actin-directed Na+/H+ exchanger 1 plasma membrane localization.  

PubMed

Ubiquitously expressed focal adhesion kinase (FAK), linked to multiple intracellular signaling pathways, has previously been shown to control cell motility, invasion, proliferation, and survival. Using mice with a keratinocyte-restricted deletion of fak (FAK(K5 KO)), we report here a novel role for FAK: maintenance of adult epidermal permeability barrier homeostasis. Abundant lacunae of unprocessed lipids in stratum corneum (SC) of FAK(K5 KO) mice and delayed barrier recovery pointed to malfunction of pH-dependent enzymes active in extracellular space of SC. Measuring the SC pH gradient showed significantly more neutral pH values in FAK(K5 KO) mice, suggesting the importance of FAK for acidification. Moreover, normal functions were restored when FAK(K5 KO) mice were exposed to a surface pH typical of mouse SC (pH = 5.5). Baseline levels and response to barrier disruption of secretory phospholipase A2 isoforms, enzymes that mediate generation of free fatty acids in epidermis, appeared similar in both FAK(K5 KO) and control littermates. We found that the critical SC acidification regulator Na(+)/H(+) exchanger 1 failed to localize to the plasma membrane in FAK-deficient keratinocytes both in vivo and in vitro. Thus, for plasma membrane localization in terminally differentiated keratinocytes, Na(+)/H(+) exchanger 1 requires an intact actin cytoskeleton, which is impaired in FAK-deficient cells. PMID:17525272

Ilic, Dusko; Mao-Qiang, Man; Crumrine, Debra; Dolganov, Gregory; Larocque, Nicholas; Xu, Pu; Demerjian, Marianne; Brown, Barbara E; Lim, Ssang-Taek; Ossovskaya, Valeria; Schlaepfer, David D; Fisher, Susan J; Feingold, Kenneth R; Elias, Peter M; Mauro, Theodora M

2007-06-01

353

Cryogenic Piezoelectric Actuator  

NASA Technical Reports Server (NTRS)

In this paper, PMN-PT single crystal piezoelectric stack actuators and flextensional actuators were designed, prototyped and characterized for space optics applications. Single crystal stack actuators with footprint of 10 mm x10 mm and the height of 50 mm were assembled using 10 mm x10mm x0.15mm PMN-PT plates. These actuators showed stroke > 65 - 85 microns at 150 V at room temperature, and > 30 microns stroke at 77 K. Flextensional actuators with dimension of 10mm x 5 mm x 7.6 mm showed stroke of >50 microns at room temperature at driving voltage of 150 V. A flextensional stack actuator with dimension of 10 mm x 5 mm x 47 mm showed stroke of approx. 285 microns at 150 V at room temperature and > 100 microns at 77K under driving of 150 V should be expected. The large cryogenic stroke and high precision of these actuators are promising for cryogenic optics applications.

Jiang, Xiaoning; Cook, William B.; Hackenberger, Wesley S.

2009-01-01

354

Standing Microcoil Actuator Array  

NASA Astrophysics Data System (ADS)

A standing microcoil actuator array fabricated for driving three-dimensional out-of-plane structures is proposed. Since the microcoil structures have a magnetic thin-film layer, they can be erected on the substrate when a vertical magnetic field is applied to them. Additionally they can be actuated when a current is applied to the coil structure. In this paper, we have demonstrated the driving of a microslit on the standing microcoil actuator array. It could achieve parallel motion to the substrate at the frequency from DC to 1 kHz.

Takeuchi, Shoji; Shimoyama, Isao

2003-06-01

355

Considerations for Contractile Electroactive Materials and Actuators  

SciTech Connect

Ras Labs produces electroactive polymer (EAP) based materials and actuators that bend, swell, ripple and now contract (new development) with low electric input. This is an important attribute because of the ability of contraction to produce life-like motion. The mechanism of contraction is not well understood. Radionuclide-labeled experiments were conducted to follow the movement of electrolytes and water in these EAPs when activated. Extreme temperature experiments were performed on the contractile EAPs with very favorable results. One of the biggest challenges in developing these actuators, however, is the electrode-EAP interface because of the pronounced movement of the EAP. Plasma treatments of metallic electrodes were investigated in order to improve the attachment of the embedded electrodes to the EAP material. Surface analysis, adhesive testing, and mechanical testing were conducted to test metal surfaces and metal-polymer interfaces. The nitrogen plasma treatment of titanium produced a strong metal-polymer interface; however, oxygen plasma treatment of both stainless steel and titanium produced even stronger metal-polymer interfaces. Plasma treatment of the electrodes allows for the embedded electrodes and the EAP material of the actuator to work and move as a unit, with no detachment, by significantly improving the metal-polymer interface.

Lenore Rasmussen, Carl J. Erickson, Lewis D. Meixler, George Ascione, Charles A. Gentile, Carl Tilson, Stephen L. Bernasek, and Esta Abelev

2010-02-19

356

The interaction between plasma filaments in dielectric barrier discharges and liquid covered wounds: electric fields delivered to model platelets and cells  

NASA Astrophysics Data System (ADS)

The treatment of wounds by atmospheric pressure plasmas in the context of plasma medicine typically proceeds through a liquid layer covering exposed cells. The wounds and their liquid covering often have irregular shapes with electrical properties (i.e. conductivity and permittivities) that may differ not only from wound-to-wound but also for a single wound as healing proceeds. The differing shapes and electrical properties extend into the liquid within the wound that typically contains cellular materials such as blood platelets. The plasma, wound, liquid and intra-liquid cellular components represent an interacting system of mutual dependence. In this paper, we discuss the results from a computational investigation of the treatment of small, liquid-covered wounds by filamentary dielectric barrier discharges. The sizes of the wounds are of the order of the plasma filaments and the liquid within the wound, an approximation of blood serum, contains idealized blood platelets. We find that the electrical properties of a wound can have significant effects on the spreading of the plasma on its surface by virtue of the deformation of the vacuum electric fields due to the shape, the effective capacitance of the wound and the discontinuities in electrical permittivity. This in turn effects the penetration of the electric field to cells under the liquid. The orientation and permittivity of the platelets relative to the liquid determines the electric fields that may stimulate the platelets.

Babaeva, Natalia Yu; Tian, Wei; Kushner, Mark J.

2014-06-01

357

Muscle Motion Solenoid Actuator  

NASA Astrophysics Data System (ADS)

It is one of our dreams to mechanically recover the lost body for damaged humans. Realistic humanoid robots composed of such machines require muscle motion actuators controlled by all pulling actions. Particularly, antagonistic pairs of bi-articular muscles are very important in animal's motions. A system of actuators is proposed using the electromagnetic force of the solenoids with the abilities of the stroke length over 10 cm and the strength about 20 N, which are needed to move the real human arm. The devised actuators are based on developments of recent modern electro-magnetic materials, where old time materials can not give such possibility. Composite actuators are controlled by a high ability computer and software making genuine motions.

Obata, Shuji

358

Rotary series elastic actuator  

NASA Technical Reports Server (NTRS)

A rotary actuator assembly is provided for actuation of an upper arm assembly for a dexterous humanoid robot. The upper arm assembly for the humanoid robot includes a plurality of arm support frames each defining an axis. A plurality of rotary actuator assemblies are each mounted to one of the plurality of arm support frames about the respective axes. Each rotary actuator assembly includes a motor mounted about the respective axis, a gear drive rotatably connected to the motor, and a torsion spring. The torsion spring has a spring input that is rotatably connected to an output of the gear drive and a spring output that is connected to an output for the joint.

Ihrke, Chris A. (Inventor); Mehling, Joshua S. (Inventor); Parsons, Adam H. (Inventor); Griffith, Bryan Kristian (Inventor); Radford, Nicolaus A. (Inventor); Permenter, Frank Noble (Inventor); Davis, Donald R. (Inventor); Ambrose, Robert O. (Inventor); Junkin, Lucien Q. (Inventor)

2012-01-01

359

Mechanical sensors and actuators  

Microsoft Academic Search

A review on mechanical sensing techniques based on magnetic methods is presented, with special focus on strain sensing in civil engineering. Some examples and features of magnetic actuation with giant magnetostrictive and magnetic shape memory alloys will be shown.

M. Pasquale

2003-01-01

360

Linear Proof Mass Actuator  

NASA Technical Reports Server (NTRS)

This paper describes the mechanical design, analysis, fabrication, testing, and lessons learned by developing a uniquely designed spaceflight-like actuator. The Linear Proof Mass Actuator (LPMA) was designed to attach to both a large space structure and a ground test model without modification. Previous designs lacked the power to perform in a terrestrial environment while other designs failed to produce the desired accelerations or frequency range for spaceflight applications. Thus, the design for a unique actuator was conceived and developed at NASA Langley Research Center. The basic design consists of four large mechanical parts (Mass, Upper Housing, Lower Housing, and Center Support) and numerous smaller supporting components including an accelerometer, encoder, and four drive motors. Fabrication personnel were included early in the design phase of the LPMA as part of an integrated manufacturing process to alleviate potential difficulties in machining an already challenging design. Operational testing of the LPMA demonstrated that the actuator is capable of various types of load functions.

Holloway, S. E., III

1995-01-01

361

Linear Proof Mass Actuator  

NASA Technical Reports Server (NTRS)

This paper describes the mechanical design, analysis, fabrication, testing, and lessons learned by developing a uniquely designed spaceflight-like actuator. The linear proof mass actuator (LPMA) was designed to attach to both a large space structure and a ground test model without modification. Previous designs lacked the power to perform in a terrestrial environment while other designs failed to produce the desired accelerations or frequency range for spaceflight applications. Thus, the design for a unique actuator was conceived and developed at NASA Langley Research Center. The basic design consists of four large mechanical parts (mass, upper housing, lower housing, and center support) and numerous smaller supporting components including an accelerometer, encoder, and four drive motors. Fabrication personnel were included early in the design phase of the LPMA as part of an integrated manufacturing process to alleviate potential difficulties in machining an already challenging design. Operating testing of the LPMA demonstrated that the actuator is capable of various types of load functions.

Holloway, Sidney E., III

1994-01-01

362

Magnetically Actuated Seal  

NASA Technical Reports Server (NTRS)

This invention is a magnetically actuated seal in which either a single electromagnet, or multiple electromagnets, are used to control the seal's position. This system can either be an open/ close type of system or an actively controlled system.

Pinera, Alex

2013-01-01

363

The effect of sintering and CMAS on the stability of plasma-sprayed zirconia thermal barrier coatings  

E-print Network

State of the art thermal barrier coatings (TBCs) for gas turbine applications comprise (7 wt.%) yttria partially stabilized zirconia (7YSZ). 7YSZ offers a range of attractive functional properties low thermal conductivity, high thermal expansion...

Shinozaki, Maya

2013-07-09

364

Combustion powered linear actuator  

DOEpatents

The present invention provides robotic vehicles having wheeled and hopping mobilities that are capable of traversing (e.g. by hopping over) obstacles that are large in size relative to the robot and, are capable of operation in unpredictable terrain over long range. The present invention further provides combustion powered linear actuators, which can include latching mechanisms to facilitate pressurized fueling of the actuators, as can be used to provide wheeled vehicles with a hopping mobility.

Fischer, Gary J. (Albuquerque, NM)

2007-09-04

365

Laser Initiated Actuator study  

SciTech Connect

The program task was to design and study a laser initiated actuator. The design of the actuator is described, it being comprised of the fiber and body subassemblies. The energy source for all experiments was a Spectra Diode 2200-H2 laser diode. The diode is directly coupled to a 100 micron core, 0.3 numerical aperture fiber optic terminated with an SMA connector. The successful testing results are described and recommendations are made.

Watson, B.

1991-06-27

366

Columnar-Structured Thermal Barrier Coatings (TBCs) by Thin Film Low-Pressure Plasma Spraying (LPPS-TF)  

Microsoft Academic Search

The very low-pressure plasma Spray (VLPPS) process has been developed with the aim of depositing uniform and thin coatings\\u000a with coverage of a large area by plasma spraying. At typical pressures of 100-200Pa, the characteristics of the plasma jet\\u000a change compared to conventional low-pressure plasma-spraying processes (LPPS) operating at 5-20kPa. The combination of plasma\\u000a spraying at low pressures with enhanced

Andreas Hospach; Georg Mauer; Robert Vaen; Detlev Stver

2011-01-01

367

Corrosion resistance of plasma sprayed NiCrAl+(ZrO 2 +Y 2 O 3 ) thermal barrier coating on 18-8 steel surface  

Microsoft Academic Search

The corrosion resistance of NiCrAl+(ZrO2+Y2O3) thermal barrier coating, formed with the plasma spraying technique, on the 18 - 8 steel surface was investigated. The phase\\u000a structure and morphology of the coating were analyzed by means of X-ray diffraction (XRD) and scanning electron microscopy\\u000a (SEM). The electrochemical corrosion behavior of the coating in 1.0 mol\\/L H2SO4 solution was studied by using

Fei Chen; Tao L; Hua-dong Ding; Hai Zhou; Kai Liu

2005-01-01

368

Emission characteristics of pulse-periodic barrier-discharge plasma in a mixture of krypton with argon and liquid freon vapor  

NASA Astrophysics Data System (ADS)

Radiation of a nanosecond barrier discharge in a mixture of krypton, argon, and carbon-tetrachloride vapor is studied in the spectral range of 150-300 nm. The plasma radiation spectra and the dependences of the intensities of the 258 nm Cl2( D' ? A'), 222 nm KrCl( B ? X), and 175 nm ArCl( B ? X) bands on the partial pressure of liquid freon vapor, argon, and krypton, as well as on the discharge excitation conditions, are studied. The optimal compositions of gas mixtures for creating a broadband UV-VUV emitter based on the band system of argon chloride, krypton chloride, and chlorine molecule are determined.

Shuaibov, A. K.; Minya, A. I.; Gritsak, R. V.; Gomoki, Z. T.

2014-02-01

369

Oxidation and crack nucleation\\/growth in an air-plasma-sprayed thermal barrier coating with NiCrAlY bond coat  

Microsoft Academic Search

The oxidation behavior of an air-plasma-sprayed thermal barrier coating (APS-TBC) system was investigated in both air and low-pressure oxygen environments. It was found that mixed oxides, in the form of (Cr,Al)2O3Ni(Cr,Al)2O4NiO, formed heterogeneously at a very early stage during oxidation in air, and in the meantime, a layer of predominantly Al2O3 grew rather uniformly along the rest of the ceramic\\/bond

W. R. Chen; X. Wu; B. R. Marple; P. C. Patnaik

2005-01-01

370

Phase stability, sintering, and thermal conductivity of plasma-sprayed ZrO 2Gd 2O 3 compositions for potential thermal barrier coating applications  

Microsoft Academic Search

Structural changes resulting from sintering and phase transformation limit the high-temperature durability of ZrO2-based thermal barrier coatings (TBCs). The objective of this study was to investigate the use of Gd2O3 as a stabilizer for ZrO2-based TBC compositions. The influence of Gd2O3 concentration (420mol.%) on the sintering and phase stability of plasma-sprayed ZrO2 powders was investigated and the data were compared

Mohamed N. Rahaman; Jacob R. Gross; Rollie E. Dutton; Hsin Wang

2006-01-01

371

Thermal cycling behavior of La 2Ce 2O 7\\/8YSZ double-ceramic-layer thermal barrier coatings prepared by atmospheric plasma spraying  

Microsoft Academic Search

The La2Ce2O7\\/8YSZ double-ceramic-layer thermal barrier coatings (TBCs) system, which is prepared by atmospheric plasma spraying (APS), is found to have a much longer lifetime compared with the single layer La2Ce2O7 system under the burner rig test. The double-ceramic-layer coating structure design can effectively alleviate the thermal expansion mismatch between the La2Ce2O7 coating and the bondcoat. The failure mechanism of the

Wen Ma; Hongying Dong; Hongbo Guo; Shengkai Gong; Xuebin Zheng

2010-01-01

372

Multiple current peaks in room-temperature atmospheric pressure homogenous dielectric barrier discharge plasma excited by high-voltage tunable nanosecond pulse in air  

SciTech Connect

Room temperature homogenous dielectric barrier discharge plasma with high instantaneous energy efficiency is acquired by using nanosecond pulse voltage with 20-200 ns tunable pulse width. Increasing the voltage pulse width can lead to the generation of regular and stable multiple current peaks in each discharge sequence. When the voltage pulse width is 200 ns, more than 5 organized current peaks can be observed under 26 kV peak voltage. Investigation also shows that the organized multiple current peaks only appear in homogenous discharge mode. When the discharge is filament mode, organized multiple current peaks are replaced by chaotic filament current peaks.

Yang, De-Zheng; Wang, Wen-Chun; Zhang, Shuai; Tang, Kai; Liu, Zhi-jie; Wang, Sen [Key Lab of Materials Modification, Dalian University of Technology, Ministry of Education, Dalian 116024 (China)] [Key Lab of Materials Modification, Dalian University of Technology, Ministry of Education, Dalian 116024 (China)

2013-05-13

373

Backed Bending Actuator  

NASA Technical Reports Server (NTRS)

Bending actuators of a proposed type would partly resemble ordinary bending actuators, but would include simple additional components that would render them capable of exerting large forces at small displacements. Like an ordinary bending actuator, an actuator according to the proposal would include a thin rectangular strip that would comprise two bonded layers (possibly made of electroactive polymers with surface electrodes) and would be clamped at one end in the manner of a cantilever beam. Unlike an ordinary bending actuator, the proposed device would include a rigid flat backplate that would support part of the bending strip against backward displacement; because of this feature, the proposed device is called a backed bending actuator. When an ordinary bending actuator is inactive, the strip typically lies flat, the tip displacement is zero, and the force exerted by the tip is zero. During activation, the tip exerts a transverse force and undergoes a bending displacement that results from the expansion or contraction of one or more of the bonded layers. The tip force of an ordinary bending actuator is inversely proportional to its length; hence, a long actuator tends to be weak. The figure depicts an ordinary bending actuator and the corresponding backed bending actuator. The bending, the tip displacement (d(sub t)), and the tip force (F) exerted by the ordinary bending actuator are well approximated by the conventional equations for the loading and deflection of a cantilever beam subject to a bending moment which, in this case, is applied by the differential expansion or contraction of the bonded layers. The bending, displacement, and tip force of the backed bending actuator are calculated similarly, except that it is necessary to account for the fact that the force F(sub b) that resists the displacement of the tip could be sufficient to push part of the strip against the backplate; in such a condition, the cantilever beam would be effectively shortened (length L*) and thereby stiffened and, hence, made capable of exerting a greater tip force for a given degree of differential expansion or contraction of the bonded layers. Taking all of these effects into account, the cantilever-beam equations show that F(sub b) would be approximately inversely proportional to d(sup 1/2) for d less than a calculable amount, denoted the transition displacement (dt). For d less than d(sub t), part of the strip would be pressed against the backplate. Therefore, the force F(sub b) would be very large for d at or near zero and would decrease as d increases toward d(sub t). At d greater than d(sub t), none of the strip would be pressed against the backplate and F(sub b) would equal the tip force F of the corresponding ordinary bending actuator. The advantage of the proposal is that a backed bending actuator could be made long to obtain large displacement when it encountered little resistance but it could also exert a large zero-displacement force, so that it could more easily start the movement of a large mass, throw a mechanical switch, or release a stuck mechanism.

Costen, Robert C.; Su, Ji

2004-01-01

374

Development of ionic polymer actuator arrays  

NASA Astrophysics Data System (ADS)

Ionic polymer metal composites (IPMC) are bending type actuators which are soft, and show large deformation at low voltage. This work explored the creation of IPMC actuator arrays to take advantage of the unique features of IPMCs, in applications such as pump and valve arrays for micro-fluidic devices, microwave switch arrays etc. In the design of the arrays, the concept of integration is key, to make the actuator array reliable, compact and scalable. The arrays are created as a single physical part, by electrode patterning on the ionic polymer and material engineering. Gold chemical plating was used to create the flexible electrodes with large capacitance on Flemion and Nafion. Patterning was done with masks created in various ways. Nafion, because of its high flexibility, can be made into diaphragm actuators with very good dynamic properties. Flemion in cantilever mode was found to generate large forces without relaxation, a key feature for the design of IPMC switches and valves. A new electrode fabrication technique was developed based on plasma polymerization on an amine monomer on the membrane and subsequent self assembly of Au colloids. A 14-micron thick Flemion sample with 10 layers of 13nm diameter Au colloids showed actuation at +/-1.5V. The demonstration of actuation of IPMC with self-assembled electrodes is a milestone for the future application of IPMC to MEMS. Finally the actuation mechanisms of Nafion and Flemion were modeled. Two dominant contributions in the actuation of IPMC were considered: electro-osmosis, and equilibrium volume which can change upon cation redistribution. A large volume transition upon pH change was observed for Flemion, whereas Nafion proved indifferent to pH. It is proposed that Flemion is generally weakly ionized and has many ionic groups in acid form. Upon cation redistribution, this structure is perturbed and the ionization increases at the cathode side because of the increase in sodium concentration, leading to an increase in equilibrium volume at the cathode and permanent bending. Nafion is always fully ionized and therefore does not show such transition. Its actuation is believed to be dominated by electro-osmosis through its highly swollen network of ionic clusters and channels.

Le Guilly, Marie

375

Yttria-Stabilized Zirconia Thermal Barriers Sprayed Using N2-H2 and Ar-H2 Plasmas: Influence of Processing and Heat Treatment on Coating Properties  

NASA Astrophysics Data System (ADS)

Thermal barrier coatings were produced using both Ar and N2 as the primary plasma gas. Various aspects of the process and the coatings were investigated. It was found that higher in-flight particle temperatures could be produced using N2, but particle velocities were lower. Deposition efficiencies could be increased by a factor of two by using N2 as compared to Ar. Coatings having similar values of porosity, hardness, Youngs modulus, and thermal diffusivity could be produced using the two primary gases. The coatings exhibited similar changes (increased hardness, stiffness, and thermal diffusivity) when heat-treated at 1400 C. However, the N2-processed coatings tended to have lower values of Youngs modulus and thermal diffusivity following such treatment. The results point to the potential advantage, in terms of reduced powder consumption and increased production rate, of using N2 as compared to Ar as the primary plasma gas for TBC deposition.

Marple, B. R.; Lima, R. S.; Moreau, C.; Kruger, S. E.; Xie, L.; Dorfman, M. R.

2007-12-01

376

Non-collinear valve actuator  

NASA Technical Reports Server (NTRS)

A non-collinear valve actuator includes a primary actuating system and a return spring system with each applying forces to a linkage system in order to regulate the flow of a quarter-turn valve. The primary actuating system and return spring system are positioned non-collinearly, which simply means the primary actuating system and return spring system are not in line with each other. By positioning the primary actuating system and return spring system in this manner, the primary actuating system can undergo a larger stroke while the return spring system experiences significantly less displacement. This allows the length of the return spring to be reduced due to the minimization of displacement thereby reducing the weight of the return spring system. By allowing the primary actuating system to undergo longer strokes, the weight of the primary actuating system may also be reduced. Accordingly, the weight of the non-collinear valve actuator is reduced.

Richard, James A. (Inventor)

2012-01-01

377

Generation of large-scale, barrier-free diffuse plasmas in air at atmospheric pressure using array wire electrodes and nanosecond high-voltage pulses  

NASA Astrophysics Data System (ADS)

This paper introduces a method to generate large-scale diffuse plasmas by using a repetition nanosecond pulse generator and a parallel array wire-electrode configuration. We investigated barrier-free diffuse plasmas produced in the open air in parallel and cross-parallel array line-line electrode configurations. We found that, when the distance between the wire-electrode pair is small, the discharges were almost extinguished. Also, glow-like diffuse plasmas with little discharge weakening were obtained in an appropriate range of line-line distances and with a cathode-grounding cross-electrode configuration. As an example, we produced a large-scale, stable diffuse plasma with volumes as large as 18 15 15 cm3, and this discharge region can be further expanded. Additionally, using optical and electrical measurements, we showed that the electron temperature was higher than the gas temperature, which was almost the same as room temperature. Also, an array of electrode configuration with more wire electrodes had helped to prevent the transition from diffuse discharge to arc discharge. Comparing the current waveforms of configurations with 1 cell and 9 cells, we found that adding cells significantly increased the conduction current and the electrical energy delivered in the electrode gaps.

Teng, Yun; Li, Lee; Liu, Yun-Long; Liu, Lun; Liu, Minghai

2014-10-01

378

Furnace Cyclic Behavior of Plasma-Sprayed Zirconia-Yttria and Multi-Component Rare Earth Oxide Doped Thermal Barrier Coatings  

NASA Technical Reports Server (NTRS)

Ceramic thermal barrier coatings will play an increasingly important role in advanced gas turbine engines because of their ability to enable further increases in engine temperatures. However, the coating performance and durability become a major concern under the increasingly harsh thermal cycling conditions. Advanced zirconia- and hafnia-based cluster oxide thermal barrier coatings with lower thermal conductivity and improved thermal stability are being developed using a high-heat-flux laser-rig based test approach. Although the new composition coatings were not yet optimized for cyclic durability, an initial durability screening of numerous candidate coating materials was carried out using conventional furnace cyclic tests. In this paper, furnace thermal cyclic behavior of the advanced plasma-sprayed zirconia-yttria-based thermal barrier coatings that were co-doped with multi-component rare earth oxides was investigated at 1163 C using 45 min hot cycles. The ceramic coating failure mechanisms were studied by using scanning electron microscopy combined with X-ray diffraction phase analysis after the furnace tests. The coating cyclic lifetime will be discussed in relation to coating phase structures, total dopant concentrations, and other properties.

Zhu, Dongming; Nesbitt, James A.; McCue, Terry R.; Barrett, Charles A.; Miller, Robert A.

2002-01-01

379

The actuated Workbench : 2D actuation in tabletop tangible interfaces  

E-print Network

The Actuated Workbench is a new actuation mechanism that uses magnetic forces to control the two-dimensional movement of physical objects on flat surfaces. This mechanism is intended for use with existing tabletop Tangible ...

Pangaro, Gian Antonio, 1976-

2003-01-01

380

Parallel Coupled Micro-Macro Actuators  

E-print Network

This thesis presents a new actuator system consisting of a micro-actuator and a macro-actuator coupled in parallel via a compliant transmission. The system is called the Parallel Coupled Micro-Macro Actuator, or PaCMMA. ...

Morrell, John Bryant

1996-01-01

381

Microrobot actuated by soft actuators based on dielectric elastomer  

Microsoft Academic Search

In this paper a microrobot, mimicking annelid animals like the earthworm, is presented. The robot is composed of several ring-like segments. Each segment is able to generate three degree-of-freedom motions such as pan\\/tilt\\/up-down respectively, and it is actuated by three soft actuators located equidistantly along the circumferential direction. The soft actuator, called antagonistically-driven linear actuator (ANTLA), is based on polymer

H. R. Choi; S. M. Ryew; K. M. Jung; H. M. Kim; J. W. Jeon; J. D. Nam; R. Maeda; K. Tanie

2002-01-01

382

Control of Unsteady Plasma Flows over Conical Forebody  

NASA Astrophysics Data System (ADS)

An experimental study of the active control of vortices over slender forebodies is performed on a 20 circular-cone-cylinder model using a pair of Single-Dielectric-Barrier-Discharge (SDBD) plasma actuators combined with duty-cycle technique. The tests are carried out in a low-turbulence 3.0 m 1.6 m low-speed wind tunnel at an angle of attack of 45. The Reynolds number based on the cone base diameter is 50 000. The results consist of measurements of circumferential pressure distributions over eight stations along the cone forebody, including one station using unsteady pressure tappings, under three different modes of controls: plasma-off, plasma port-on or starboard-on, and plasma duty-cycle actuation. The cross-sectional side forces over the cone are calculated from the measured pressures. The ensemble and phase-locked averaged loads at various duty cycles are investigated. The test results indicate that the variation of the phase-locked-averaged side force in a period of the duty cycle is a smooth-wave curve rather than the square-wave curve. The linearity of the controlled lateral forces and moments with respect to the duty cycle is improved over previous studies because of the improved design of the actuators.

Meng, X. S.; Cai, J. S.; Luo, S. J.; Liu, F.

2011-09-01

383

Conducting polymer actuators : temperature effects  

E-print Network

In order to utilize conducting polymer actuators as a viable engineering solution, it is necessary to produce usable levels of force with a reasonable bandwidth. Polypyrrole actuated at temperatures as high as 100 C ...

Del Zio, Michael R. (Michael Robert), 1982-

2006-01-01

384

A reactionless precision pointing actuator  

NASA Technical Reports Server (NTRS)

The applications, design, control and testing of an actuator that provides the precise motion control of a gimbal platform without torquing against the basebody to which it is attached are described. The reactionless actuator described was given the name reactuator.

Wiktor, Peter

1987-01-01

385

Electrolytic phase transformation actuators  

NASA Astrophysics Data System (ADS)

The emerging field of materials-based actuation continues to be the focus of considerable research due to its inherent scalability and its promise to drive devices in ways that cannot be realized with conventional mechanical actuator strategies. Current approaches include electrochemically responsive conducting polymers, capacitance-driven carbon nanotubes actuators, pH responsive hydrogels, ionic polymer metal composites, electric field responsive elastomers, and field-driven electrostrictive polymers. However, simple electrochemical processes that lead to phase transformations, particularly from liquid to gas, have been virtually ignored. Although a few specialized applications have been proposed, the nature of the reactions and their implication for design, performance, and widespread applicability have not been addressed. Herein we report an electrolytic phase transformation (EPT) actuator, a device capable of producing strains surpassing 136,000% and stresses beyond 200 MPa. These performance characteristics are several orders of magnitude greater than those reported for other materials and could potentially compete with existing commercial hydraulic systems. Furthermore, unlike other materials-based systems that rely on bimorph structures to translate infinitesimally small volume changes into observable deflections, this device can direct all of its output towards linear motion. We show here that an unoptimized actuator prototype can produce volume and pressure changes close to the theoretically predicted values, with maximum stress (70 kPa) limited only by the mechanical strength of the apparatus. Expansion is very rapid and scales with applied current density. Retraction depends on the catalytic nature of the electrode, and state-of-the-art commercial fuel cell electrodes should allow rates surpassing 0.9 mL's-1.cm-2 and 370 kPa's-1.cm-2. We anticipate that this approach will provide a new direction for producing scalable, low-weight, high performance actuators that will be useful in a broad range of applications.

Cameron, Colin G.; Freund, Michael S.

2003-07-01

386

A nonequilibrium argon-oxygen planar plasma jet using a half-confined dielectric barrier duct in ambient air  

NASA Astrophysics Data System (ADS)

A nonequilibrium argon plasma jet with oxygen addition, generated in a planar dielectric duct and issuing into ambient air with one edge stuck on a dielectric plane, is reported for the first time. This argon-oxygen plasma jet can be operated at low applied voltage as a filamentary discharge at atmospheric pressure. The addition of a small amount of oxygen results in the increase of produced ozone concentration and continuous emissions of centering at about 185 nm, 205 nm, 230 nm, and 253 nm. The synergistic generation of short wavelength ultraviolet emissions and active species is significantly important for plasma applications.

Li, Qing; Takana, Hidemasa; Pu, Yi-Kang; Nishiyama, Hideya

2012-03-01

387

Thermally oscillating actuators  

NASA Technical Reports Server (NTRS)

The actuator was redesigned to accommodate the new thermal motor for the Helios flipper. This design retained the basic configuration and dimensions of the original actuator. Changes were made primarily to the cradle and motor assembly. Because of the increased dimensions of the thermal motor, it was necessary to increase the diameter of the pellet case and associated parts including the back off spring and the piston return spring. The new springs were designed to yield the same spring rate differential as the originals. The design effort resulted in a new top assembly and approximately twenty sub-assembly and detail drawings. A list of drawings generated by EMR is attached.

1973-01-01

388

Pneumatic Actuator Systems  

NSDL National Science Digital Library

In this interactive activity adapted from MATEC, learn about pneumatic actuator systems, which use compressed air to transmit motion. Animations illustrate the components of a typical pneumatic actuator system: the computer, communication module, programmable logic controller, input/output module, solenoid valve, and pneumatic device. Observe how the system functions as a whole, and learn more about some common pneumatic devices.The interactive is accompanied by a background essay, standards alignment, and discussion questions. Users who sign up for a free account can save the resource and download it as well.

2012-06-04

389

Tetherless thermobiochemically actuated microgrippers  

PubMed Central

We demonstrate mass-producible, tetherless microgrippers that can be remotely triggered by temperature and chemicals under biologically relevant conditions. The microgrippers use a self-contained actuation response, obviating the need for external tethers in operation. The grippers can be actuated en masse, even while spatially separated. We used the microgrippers to perform diverse functions, such as picking up a bead on a substrate and the removal of cells from tissue embedded at the end of a capillary (an in vitro biopsy). PMID:19139411

Leong, Timothy G.; Randall, Christina L.; Benson, Bryan R.; Bassik, Noy; Stern, George M.; Gracias, David H.

2009-01-01

390

Discrete Actuator Deformable Mirror  

NASA Astrophysics Data System (ADS)

A discrete actuator deformable surface device, which provides as much as 12 pm of surface deformation using +/-1 kV, has been developed at Itek. The discrete actuator device, made from bonded layers of piezoelectric discs, has been continuously exercised for a period of several hundred hours. No change in surface figure was observed even using a dilatation level of 6 microns. By employing both optical and electrical techniques, the fundamental mechanical resonance has been measured and found to depend upon the boundary condition in a complicated manner.

Everson, J. H.; Aldrich, R. E.; Albertinetti, N. P.

1981-04-01

391

Cold vapor generation of Zn based on dielectric barrier discharge induced plasma chemical process for the determination of water samples by atomic fluorescence spectrometry.  

PubMed

A new plasma chemical vapor generation (plasma-CVG) method for Zn was developed by dielectric barrier discharge (DBD). The dissolved Zn ions was readily converted to volatile species by DBD plasma in the presence of hydrogen and then, the generated Zn vapor, Zn(0), was detected by cold vapor atomic fluorescence spectrometry (AFS). It eliminated the use of unstable tetrahydroborate-reducing reagent and high-purity acids. The operating conditions for the DBD plasma-CVG system were optimized for the efficient vapor generation of Zn. In addition, possible interferences from coexisting ions on the plasma-CVG of Zn were also examined. No appreciable matrix interference was found from most of the examined ions at concentration of 1mgL(-1). However, severe depression of the Zn vapor generation efficiency was observed in the presence of ions at 10mgL(-1). Under the optimal conditions, the limit of detection (LOD) was calculated to be 0.2?gL(-1); good repeatability (relative standard deviation (RSD)?=?2.6%, n?=?11) was obtained for a 20 Zn?gL(-1) standard. The accuracy of the proposed method was validated though analysis of Zn in reference material of simulated natural water sample GSB07-1184-2000 and the determined result was in good agreement with the reference value. The proposed method has also been successfully applied to the determination of Zn in Changjiang River water, Wuhan East Lake water, and Wuhan tap water samples. It provides an alternative green vapor generation method for Zn. PMID:24871865

Zhu, Zhenli; Liu, Lu; Li, Yixiao; Peng, Huan; Liu, Zhifu; Guo, Wei; Hu, Shenghong

2014-11-01

392

Dyeing mechanism and optimization of polyamide 6,6 functionalized with double barrier discharge (DBD) plasma in air  

NASA Astrophysics Data System (ADS)

The physico-chemical improvements occasioned by DBD plasma discharge in dyeing process of polyamide 6,6 (PA66) fibers were investigated. The SEM, fluorescence microscopy, UV-vis spectroscopy, surface energy, FTIR, XPS and pH of aqueous extracts confirm the high polar functionalization of PA66 fibers due to plasma incorporation of oxygen atoms from atmospheric air. DBD plasma-generated reactive species preferentially break the CN bonds, and not the aliphatic C-C chain of PA66. Formation of low-molecular weight acidic molecules that act as dye "carrier" and creation of micro-channels onto PA66 surface seems to favor dye diffusion into the fiber cores. Plasma treatment allows high level of direct dye diffusion and fixation in PA66 fibers at lower temperatures and shorter dyeing times than traditional dyeing methods.

Oliveira, Fernando Ribeiro; Zille, Andrea; Souto, Antonio Pedro

2014-02-01

393

Materials for dielectric elastomer actuators  

Microsoft Academic Search

Dielectric elastomer actuators consist of an elastomer film sandwiched between compliant electrodes. They work as electrostatic actuators: when a large electric field is applied over the electrodes, the rubber is compressed and the elastomer film elongates in the film plane. The performance of dielectric elastomer actuators (DEA), when a constant potential is applied, is expressed in a universal equation where

Peter Sommer-Larsen; Anne L. Larsen

2004-01-01

394

On designing dielectric elastomer actuators  

Microsoft Academic Search

Subject to a voltage, a dielectric elastomer can deform substantially, making it a desirable material for actuators. Designing such an actuator, however, has been challenging due to nonlinear equations of state, as well as multiple modes of failure, parameters of design, and measures of performance. This paper explores these issues, using a spring-roll actuator as an example. We formulate the

Mickael Moscardo; Xuanhe Zhao; Zhigang Suo; Yuri Lapusta

2008-01-01

395

Response of dielectric elastomer actuators  

Microsoft Academic Search

Elastomer films sandwiched between compliant electrodes work as electrostatic actuators when a large electric field is applied over the electrodes. We have analyzed the mechanical and electrical response of actuators to a sinusoidal varying driving voltage. The actuator acts as a capacitor in the electric circuit, but due to very high strains, the capacitance changes during a work cycle. The

Peter Sommer-Larsen; Jacob C. Hooker; Guggi Kofod; Keld West; Mohammed Benslimane; Peter Gravesen

2001-01-01

396

High torque miniature rotary actuator  

Microsoft Academic Search

This paper summarizes the design and the development of a miniature rotary actuator (36 mm diameter by 100 mm length) used in spacecraft mechanisms requiring high torques and\\/or ultra-fine step resolution. This actuator lends itself to applications requiring high torque but with strict volume limitations which challenge the use of conventional rotary actuators. The design challenge was to develop a

Ruben Nalbandian

2005-01-01

397

Angular-Momentum-Compensating Actuator  

NASA Technical Reports Server (NTRS)

Reactionless actuator developed for instrument-pointing platforms on flexible spacecraft; by eliminating reactions, actuator changes aiming angle of platform without inducing vibrations in spacecraft, eliminateing vibrations in point angle of instrument platform. Actuator used on Earth in such systems as helicopter platforms for television cameras in law enforcement and news telecasts.

Wiktor, Peter J.

1988-01-01

398

Barrier properties to surrogates of hydrogenated carbon nano-films deposited on PET by plasma-enhanced chemical vapour deposition.  

PubMed

Poly(ethylene terephthalate) resin was contaminated with a series of surrogates using a US Food and Drug Administration protocol. The contaminated samples were coated with two different kinds of hydrogenated amorphous carbon thin films (a-C:H): one with diamond-like hydrogenated amorphous carbon and another with polymer-like hydrogenated carbon (PLCH) phases. To evaluate the barrier properties of the a-C:H films, migration assays were performed using food simulants. After the tests, analysis by gas chromatography with different detectors was carried out. The appearance of the films before and after the migration experiments was studied by field emission scanning electron microscopy. The results showed that a-C:H films have good barrier properties for most of the evaluated compounds, mainly when they are deposited as PLCH phase. PMID:25254307

Oliveira, Eder C; Echegoyen, Yolanda; Nerin, Cristina; Cruz, Sandra A

2014-11-01

399

Modeling of residual stresses in a plasma-sprayed zirconia\\/alumina functionally graded-thermal barrier coating  

Microsoft Academic Search

Thermal barrier coating (TBC) structures composed of Al2O3 and ZrO2 with different chemical compositions on the NiCoCrAlY bondcoat are proposed to improve the oxidation resistance of TBC systems. The concept of functionally graded materials is applied to manage residual stresses due to sharp interface between dissimilar materials that can lead to a premature failure of TBC system. A numerical study

Sujanto Widjaja; Andi M. Limarga; Tick Hon Yip

2003-01-01

400

Modeling and Simulation of Microstructure Formation for Porosity Prediction in Thermal Barrier Coatings Under Air Plasma Spraying Condition  

Microsoft Academic Search

Effective physical and mechanical properties of thermal barrier coatings are strongly dependent on the coating microstructure.\\u000a The main objective of this study is the coating porosity prediction during the coating formation by simulation. For this purpose,\\u000a two simulation approaches are presented. The first model takes into account physical impact, deformation, and overlying of\\u000a powder particles on the solid substrate. Therefore,

K. Bobzin; N. Bagcivan; D. Parkot; M. Schfer; I. Petkovi?

2009-01-01

401

Evaluation of laser-glazed plasma-sprayed thermal barrier coatings under high temperature exposure to molten salts  

Microsoft Academic Search

Thermal Barrier Coating (TBC) systems are frequently used in gas turbine engines to provide thermal insulation to the hot-section metallic components and also to protect them from oxidation, hot corrosion and erosion. Surface sealing treatments, namely laser-glazing, have been showing a high potential for extending in-service lifetimes of these systems by improving chemical and thermo-mechanical resistance. In this investigation, both

C. Batista; A. Portinha; R. M. Ribeiro; V. Teixeira; C. R. Oliveira

2006-01-01

402

The static actuation of dielectric elastomer actuators: how does pre-stretch improve actuation?  

Microsoft Academic Search

It has previously been shown that providing dielectric elastomer actuators with a level of pre-stretch can improve properties such as breakdown strength, actuation strain and efficiency. The actuation in such actuators depends on an interplay between the highly nonlinear hyperelastic stress-strain behaviour with the electrostatic Maxwell's stress; however, the direct effects of pre-stretch on the electromechanical coupling have still not

Guggi Kofod

2008-01-01

403

Characterization of the ionic wind produced by a DBD actuator designed to control the laminar-to-turbulent transition  

Microsoft Academic Search

Non thermal plasma actuators have provided a novel means of studying active flow control in aerodynamic research. The ionic wind induced by such devices has the ability to couple momentum into boundary layers resulting in control of flow separation or delay of laminar-to-turbulent transition. Significant results would probably be obtained at higher Reynolds numbers if the plasma actuators were systematically

Vincent Boucinha; Romain Joussot; Pierre Magnier; Rgine Weber

404

Bistable microelectromechanical actuator  

DOEpatents

A bistable microelectromechanical (MEM) actuator is formed on a substrate and includes a stressed membrane of generally rectangular shape that upon release assumes a curvilinear cross-sectional shape due to attachment at a midpoint to a resilient member and at opposing edges to a pair of elongate supports. The stressed membrane can be electrostatically switched between a pair of mechanical states having mirror-image symmetry, with the MEM actuator remaining in a quiescent state after a programming voltage is removed. The bistable MEM actuator according to various embodiments of the present invention can be used to form a nonvolatile memory element, an optical modulator (with a pair of mirrors supported above the membrane and moving in synchronism as the membrane is switched), a switchable mirror (with a single mirror supported above the membrane at the midpoint thereof) and a latching relay (with a pair of contacts that open and close as the membrane is switched). Arrays of bistable MEM actuators can be formed for applications including nonvolatile memories, optical displays and optical computing.

Fleming, James G. (Albuquerque, NM)

1999-01-01

405

Bistable microelectromechanical actuator  

DOEpatents

A bistable microelectromechanical (MEM) actuator is formed on a substrate and includes a stressed membrane of generally rectangular shape that upon release assumes a curvilinear cross-sectional shape due to attachment at a midpoint to a resilient member and at opposing edges to a pair of elongate supports. The stressed membrane can be electrostatically switched between a pair of mechanical states having mirror-image symmetry, with the MEM actuator remaining in a quiescent state after a programming voltage is removed. The bistable MEM actuator according to various embodiments of the present invention can be used to form a nonvolatile memory element, an optical modulator (with a pair of mirrors supported above the membrane and moving in synchronism as the membrane is switched), a switchable mirror (with a single mirror supported above the membrane at the midpoint thereof) and a latching relay (with a pair of contacts that open and close as the membrane is switched). Arrays of bistable MEM actuators can be formed for applications including nonvolatile memories, optical displays and optical computing. 49 figs.

Fleming, J.G.

1999-02-02

406

"Mighty Worm" Piezoelectric Actuator  

NASA Technical Reports Server (NTRS)

"Mighty Worm" piezoelectric actuator used as adjustable-length structural member, active vibrator or vibration suppressor, and acts as simple (fixed-length) structural member when inactive. Load force not applied to piezoelectric element in simple-structural-member mode. Piezoelectric element removed from load path when not in use.

Bamford, Robert M.; Wada, Ben K.; Moore, Donald M.

1994-01-01

407

Piezoelectric linear actuator  

NASA Technical Reports Server (NTRS)

Actuator exerts linear force that is controllable and reproducible to microinch tolerance. It is constructed for extremely accurate control of a valve but can also be used as a variable venturi meter, micropositioner, microthruster, and in fluidics and reaction-control systems.

Lehrer, S.

1969-01-01

408

Electroactive polymer actuator devices (EAPAD)  

NASA Astrophysics Data System (ADS)

Designing and building devices that utilize electroactive polymer actuators brings into sharp focus the performance required of these materials. Using the example of a "rehabilitation glove", it is shown that the performance of polypyrrole actuators fall short of that required. In particular, the need to simultaneously produce 5% actuator strain at a 5 MPa isotonic stress cannot be achieved with the actuators investigated in our laboratories to date. However, significant improvements in the performance under load have been achieved with the use of ionic liquid electrolytes. The use of new materials such as composites of conducting polymers and carbon nanotubes offers the possibility of further improvements in actuator performance. Finally, redesigning the glove actuator offers a compromise solution that allows existing actuators to be used in a prototype device.

Spinks, Geoffrey M.; Wallace, Gordon G.; Ding, Jie; Zhou, Dezhi; Xi, Binbin; Scott, Timothy R.; Truong, Van-Tan

2003-07-01

409

Dependency of temperature on polarization in CH{sub 4}/N{sub 2} dielectric barrier discharge plasma: A crude assumption  

SciTech Connect

We have investigated the variations of polarization (P) and the temperature ({Delta}T) at the electrode surfaces during the deposition of C-N layer in CH{sub 4}/N{sub 2} (1:2) dielectric barrier discharge plasma. The reactive deposition process influences the surface temperature, polarization, and the value of the in situ dielectric constant. We have developed a crude model that correlates the surface temperature and surface polarization with thin film properties. We assume that during the thin film deposition process, the atomic mean kinetic energy is equal to the electrostatic energy stored in the electrode surface area. Theoretically estimated temperature is found to agree well with the experimental results. However, the linear model thus developed cannot be used to explain the phenomena in the interfacial polarization stage that requires a nonlinear theory.

Majumdar, Abhijit; Hippler, Rainer [Institut of Physics, University of Greifswald, Felix Hausdorff Strasse 6, 17489 Greifswald (Germany); Ghosh, Basudev [Jadavpur University, Kolkata 700032, West Bengal (India)

2010-11-15

410

Responses of OH (X2?) and OH (A2?+) to high-energy electrons of dielectric barrier discharge in plasma-assisted burner flame  

NASA Astrophysics Data System (ADS)

We examined the responses of OH(X2?) and OH(A2?+) in a premixed CH4 flame to high-energy electrons produced by a dielectric barrier discharge. The density of OH(X2?) did not respond to the pulsed production of high-energy electrons; however, we observed a pulsed increase in the density of chemically produced OH(A2?+). In addition, we observed that OH(A2?+) produced at the same time as high-energy electrons had a lower rotational temperature. We discussed possible key reactions in plasma-assisted combustion on the basis of the experimental observation showing the production of cold OH(A2?+).

Zaima, Kazunori; Sasaki, Koichi

2014-11-01

411

Nanolayer biofilm coated on magnetic nanoparticles by using a dielectric barrier discharge glow plasma fluidized bed for immobilizing an antimicrobial peptide.  

PubMed

Using the monomer of acrylic acid and the novel technique of using a dielectric barrier discharge glow plasma fluidized bed (GPFB), a nanolayer biofilm of polyacrylic acid (PAA) was uniformly coated on the surface of magnetic nickel nanoparticles (NPs). Transmission electron microscopy, Fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopy, etc, were used to characterize the modified NPs. The thickness of the biofilm was about 2 nm when the NPs were treated using the GPFB once, and the discharging conditions affected the density of the carboxyl group obviously. The PAA acting as an adhesion layer was used to immobilize the antimicrobial peptide LL-37, to kill the bacteria of Escherichia coli (E. coli), and the results indicated that the modified nickel NPs immobilizing a certain concentration of LL-37 could kill the bacteria effectively. PMID:19847021

Chen, Guangliang; Zhou, Mingyan; Chen, Shihua; Lv, Guohua; Yao, Juming

2009-11-18

412

Effect of Bond Coats on Thermal Shock Resistance of Thermal Barrier Coatings Deposited Onto Polymer Matrix Composites Via Air Plasma Spray Process  

NASA Astrophysics Data System (ADS)

Thermal barrier coating systems with different bond coats were fabricated on polymer matrix composites via the air plasma spray process. During a thermal shock test at 400 C, Zn and Al interlayers were helpful in improving the thermal shock resistance of coatings due to the low melting point. The coating system consisted of a soft zinc layer as a bond coat, and YSZ as a top coat exhibited the best thermal shock resistance, attributed to the lower residual stress and lower thermal stress in the Zn interlayer. The failure mechanism of the coating system was mainly ascribable to the residual stress derived from the deposition process, thermal stress, and further damage of the substrate.

Huang, Wenzhi; Zhao, Yu; Fan, Xizhi; Meng, Xiangsheng; Wang, Ying; Cai, Xiaolong; Cao, Xueqiang; Wang, Zhen

2013-08-01

413

Considerations For Contractile Electroactive Materials and Actuators  

SciTech Connect

Electroactive polymers (EAPs) that bend, swell, ripple (first generation materials), and now contract with low electric input (new development) have been produced. The mechanism of contraction is not well understood. Radionuclide-labeled experiments, molecular modeling, electrolyte experiments, pH experiments, and an ionic concentration experiment were used to determine the chain of events that occur during contraction and, reciprocally, expansion when the polarity is reversed, in these ionic EAPs. Plasma treatment of the electrodes, along with other strategies, allows for the embedded electrodes and the EAP material of the actuator to work and move as a unit, with no detachment, by significantly improving the metal-polymer interface, analogous to nerves and tendons moving with muscles during movement. Challenges involved with prototyping actuation using contractile EAPs are also discussed.

Lenore Rasmussen, Lewis D. Meixler and Charles A. Gentile

2012-02-29

414

Dielectric barrier discharge plasma in Ar/O2 promoting apoptosis behavior in A549 cancer cells  

NASA Astrophysics Data System (ADS)

The Ar/O2 plasma needle in the induction of A549 cancer cells apoptosis process is studied by means of real-time observation. The entire process of programmed cell death is observed. The typical morphological changes of A549 apoptosis are detected by 4', 6-diamidino-2-phenylindole staining, for example, chromatin condensation and nuclear fragmentation. Cell viability is determined and quantified by neutral red uptake assay, and the survival rate of A549 from Ar/O2 plasmas is presented. Further spectral analysis indicates the reactive species, including O and OH play crucial roles in the cell inactivation.

Huang, Jun; Li, Hui; Chen, Wei; Lv, Guo-Hua; Wang, Xing-Quan; Zhang, Guo-Ping; Ostrikov, Kostya; Wang, Peng-Ye; Yang, Si-Ze

2011-12-01

415

The Cortical Acto-Myosin Network: From Diffusion Barrier to Functional Gateway in the Transport of Neurosecretory Vesicles to the Plasma Membrane  

PubMed Central

Dysregulation of regulated exocytosis is linked to an array of pathological conditions, including neurodegenerative disorders, asthma, and diabetes. Understanding the molecular mechanisms underpinning neuroexocytosis including the processes that allow neurosecretory vesicles to access and fuse with the plasma membrane and to recycle post-fusion, is therefore critical to the design of future therapeutic drugs that will efficiently tackle these diseases. Despite considerable efforts to determine the principles of vesicular fusion, the mechanisms controlling the approach of vesicles to the plasma membrane in order to undergo tethering, docking, priming, and fusion remain poorly understood. All these steps involve the cortical actin network, a dense mesh of actin filaments localized beneath the plasma membrane. Recent work overturned the long-held belief that the cortical actin network only plays a passive constraining role in neuroexocytosis functioning as a physical barrier that partly breaks down upon entry of Ca2+ to allow secretory vesicles to reach the plasma membrane. A multitude of new roles for the cortical actin network in regulated exocytosis have now emerged and point to highly dynamic novel functions of key myosin molecular motors. Myosins are not only believed to help bring about dynamic changes in the actin cytoskeleton, tethering and guiding vesicles to their fusion sites, but they also regulate the size and duration of the fusion pore, thereby directly contributing to the release of neurotransmitters and hormones. Here we discuss the functions of the cortical actin network, myosins, and their effectors in controlling the processes that lead to tethering, directed transport, docking, and fusion of exocytotic vesicles in regulated exocytosis. PMID:24155741

Papadopulos, Andreas; Tomatis, Vanesa M.; Kasula, Ravikiran; Meunier, Frederic A.

2013-01-01

416

Dielectric Actuation of Polymers  

NASA Astrophysics Data System (ADS)

Dielectric polymers are widely used in a plurality of applications, such as electrical insulation, dielectric capacitors, and electromechanical actuators. Dielectric polymers with large strain deformations under an electric field are named dielectric elastomers (DE), because of their relative low modulus, high elongation at break, and outstanding resilience. Dielectric elastomer actuators (DEA) are superior to traditional transducers as a muscle-like technology: large strains, high energy densities, high coupling efficiency, quiet operation, and light weight. One focus of this dissertation is on the design of DE materials with high performance and easy processing. UV radiation curing of reactive species is studied as a generic synthesis methodology to provide a platform for material scientists to customize their own DE materials. Oligomers/monomers, crosslinkers, and other additives are mixed and cured at appropriate ratios to control the stress-strain response, suppress electromechanical instability of the resulting polymers, and provide stable actuation strains larger than 100% and energy densities higher than 1 J/g. The processing is largely simplified in the new material system by removal of the prestretching step. Multilayer stack actuators with 11% linear strain are demonstrated in a procedure fully compatible with industrial production. A multifunctional DE derivative material, bistable electroactive polymer (BSEP), is invented enabling repeatable rigid-to-rigid deformation without bulky external structures. Bistable actuation allows the polymer actuator to have two distinct states that can support external load without device failure. Plasticizers are used to lower the glass transition temperature to 45 C. Interpenetrating polymer network structure is established inside the BSEP to suppress electromechanical instability, providing a breakdown field of 194 MV/m and a stable bistable strain as large as 228% with a 97% strain fixity. The application of BSEP in tactile display is investigated by the prototyping of a large scale refreshable Braille display device. Braille is a critical way for the vision impaired community to learn literacy and improve life quality. Current piezoelectrics-based refreshable Braille display technologies are limited to up to 1 line of Braille text, due to the bulky size of bimorph actuators. Based on the unique actuation feature of BSEP, refreshable Braille display devices up to smartphone-size have been demonstrated by polymer sheet laminates. Dots in the devices can be individually controlled via incorporated field-driven BSEP actuators and Joule heater units. A composite material consisting of silver nanowires (AgNW) embedded in a polymer substrate is brought up as a compliant electrode candidate for BSEP application. The AgNW composite is highly conductive (Rs: 10 ?/sq) and remains conductive at strains as high as 140% (Rs: <10 3 ?/sq). The baseline conductivity has only small changes up to 90% strain, which makes it low enough for both field driving and stretchable Joule heating. An out-of-plane bistable area strain up to 68% under Joule heating is achieved.

Niu, Xiaofan

417

Microstructural analysis of YSZ and YSZ\\/Al 2O 3 plasma sprayed thermal barrier coatings after high temperature oxidation  

Microsoft Academic Search

Air plasma sprayed TBCs usually include lamellar structure with high interconnected porosities which transfer oxygen from YSZ layer towards bond coat and cause TGO growth and internal oxidation of bond coat.The growth of thermally grown oxide (TGO) at the interface of bond coat and ceramic layer and internal oxidation of bond coat are considered as the main destructive factors in

Mohsen Saremi; Abbas Afrasiabi; Akira Kobayashi

2008-01-01

418

Ultrasonically Actuated Tools for Abrading Rock Surfaces  

NASA Technical Reports Server (NTRS)

An ultrasonic rock-abrasion tool (URAT) was developed using the same principle of ultrasonic/sonic actuation as that of the tools described in two prior NASA Tech Briefs articles: Ultrasonic/ Sonic Drill/Corers With Integrated Sensors (NPO-20856), Vol. 25, No. 1 (January 2001), page 38 and Ultrasonic/ Sonic Mechanisms for Drilling and Coring (NPO-30291), Vol. 27, No. 9 (September 2003), page 65. Hence, like those tools, the URAT offers the same advantages of low power demand, mechanical simplicity, compactness, and ability to function with very small axial loading (very small contact force between tool and rock). Like a tool described in the second of the cited previous articles, a URAT includes (1) a drive mechanism that comprises a piezoelectric ultrasonic actuator, an amplification horn, and a mass that is free to move axially over a limited range and (2) an abrasion tool bit. A URAT tool bit is a disk that has been machined or otherwise formed to have a large number of teeth and an overall shape chosen to impart the desired shape (which could be flat or curved) to the rock surface to be abraded. In operation, the disk and thus the teeth are vibrated in contact with the rock surface. The concentrated stresses at the tips of the impinging teeth repeatedly induce microfractures and thereby abrade the rock. The motion of the tool induces an ultrasonic transport effect that displaces the cuttings from the abraded area. The figure shows a prototype URAT. A piezoelectric-stack/horn actuator is housed in a cylindrical container. The movement of the actuator and bit with respect to the housing is aided by use of mechanical sliders. A set of springs accommodates the motion of the actuator and bit into or out of the housing through an axial range between 5 and 7 mm. The springs impose an approximately constant force of contact between the tool bit and the rock to be abraded. A dust shield surrounds the bit, serving as a barrier to reduce the migration of rock debris to sensitive instrumentation or mechanisms in the vicinity. A bushing at the tool-bit end of the housing reduces the flow of dust into the actuator and retains the bit when no axial load is applied.

Dolgin, Benjamin; Sherrit, Stewart; Bar-Cohen, Yoseph; Rainen, Richard; Askin, Steve; Bickler, Donald; Lewis, Donald; Carson, John; Dawson, Stephen; Bao, Xiaoqi; Chang, Zensheu; Peterson, Thomas

2006-01-01

419

Cylindrical Piezoelectric Fiber Composite Actuators  

NASA Technical Reports Server (NTRS)

The use of piezoelectric devices has become widespread since Pierre and Jacques Curie discovered the piezoelectric effect in 1880. Examples of current applications of piezoelectric devices include ultrasonic transducers, micro-positioning devices, buzzers, strain sensors, and clocks. The invention of such lightweight, relatively inexpensive piezoceramic-fiber-composite actuators as macro fiber composite (MFC) actuators has made it possible to obtain strains and displacements greater than those that could be generated by prior actuators based on monolithic piezoceramic sheet materials. MFC actuators are flat, flexible actuators designed for bonding to structures to apply or detect strains. Bonding multiple layers of MFC actuators together could increase force capability, but not strain or displacement capability. Cylindrical piezoelectric fiber composite (CPFC) actuators have been invented as alternatives to MFC actuators for applications in which greater forces and/or strains or displacements may be required. In essence, a CPFC actuator is an MFC or other piezoceramic fiber composite actuator fabricated in a cylindrical instead of its conventional flat shape. Cylindrical is used here in the general sense, encompassing shapes that can have circular, elliptical, rectangular or other cross-sectional shapes in the planes perpendicular to their longitudinal axes.

Allison, Sidney G.; Shams, Qamar A.; Fox, Robert L.

2008-01-01

420

Electrical Actuation Technology Bridging  

NASA Astrophysics Data System (ADS)

This document contains the proceedings of the NASA Electrical Actuation Technology Bridging (ELA-TB) Workshop held in Huntsville, Alabama, September 29-October 1, 1992. The workshop was sponsored by the NASA Office of Space Systems Development and Marshall Space Flight Center (MSFC). The workshop addressed key technologies bridging the entire field of electrical actuation including systems methodology, control electronics, power source systems, reliability, maintainability, and vehicle health management with special emphasis on thrust vector control (TVC) applications on NASA launch vehicles. Speakers were drawn primarily from industry with participation from universities and government. In addition, prototype hardware demonstrations were held at the MSFC Propulsion Laboratory each afternoon. Splinter sessions held on the final day afforded the opportunity to discuss key issues and to provide overall recommendations. Presentations are included in this document.

Hammond, Monica; Sharkey, John

1993-05-01

421

Thermally actuated thermionic switch  

SciTech Connect

A thermally actuated thermionic switch which responds to an increase of temperature by changing from a high impedance to a low impedance at a predictable temperature set point. The switch has a bistable operation mode switching only on temperature increases. The thermionic material may be a metal which is liquid at the desired operation temperature and held in matrix in a graphite block reservoir, and which changes state (ionizes, for example) so as to be electrically conductive at a desired temperature.

Barrus, Donald M. (San Jose, CA); Shires, Charles D. (San Jose, CA)

1988-01-01

422

Shape memory alloy actuator  

DOEpatents

An actuator for cycling between first and second positions includes a first shaped memory alloy (SMA) leg, a second SMA leg. At least one heating/cooling device is thermally connected to at least one of the legs, each heating/cooling device capable of simultaneously heating one leg while cooling the other leg. The heating/cooling devices can include thermoelectric and/or thermoionic elements.

Varma, Venugopal K. (Knoxville, TN)

2001-01-01

423

Linear mass actuator  

NASA Technical Reports Server (NTRS)

A linear mass actuator includes an upper housing and a lower housing connectable to each other and having a central passageway passing axially through a mass that is linearly movable in the central passageway. Rollers mounted in the upper and lower housings in frictional engagement with the mass translate the mass linearly in the central passageway and drive motors operatively coupled to the roller means, for rotating the rollers and driving the mass axially in the central passageway.

Holloway, Sidney E., III (inventor); Crossley, Edward A., Jr. (inventor); Jones, Irby W. (inventor); Miller, James B. (inventor); Davis, C. Calvin (inventor); Behun, Vaughn D. (inventor); Goodrich, Lewis R., Sr. (inventor)

1992-01-01

424

Dissolution actuated sample container  

DOEpatents

A sample collection vial and process of using a vial is provided. The sample collection vial has an opening secured by a dissolvable plug. When dissolved, liquids may enter into the interior of the collection vial passing along one or more edges of a dissolvable blocking member. As the blocking member is dissolved, a spring actuated closure is directed towards the opening of the vial which, when engaged, secures the vial contents against loss or contamination.

Nance, Thomas A.; McCoy, Frank T.

2013-03-26

425

Detection of segmentation cracks in top coat of thermal barrier coatings during plasma spraying by non-contact acoustic emission method  

NASA Astrophysics Data System (ADS)

Numerous cracks can be observed in the top coat of thermal barrier coatings (TBCs) deposited by the atmospheric plasma spraying (APS) method. These cracks can be classified into vertical and horizontal ones and they have opposite impact on the properties of TBCs. Vertical cracks reduce the residual stress in the top coat and provide strain tolerance. On the contrary, horizontal cracks trigger delamination of the top coat. However, monitoring methods of cracks generation during APS are rare even though they are strongly desired. Therefore, an in situ, non-contact and non-destructive evaluation method for this objective was developed in this study with the laser acoustic emission (AE) technique by using laser interferometers as a sensor. More AE events could be detected by introducing an improved noise reduction filter and AE event detection procedures with multiple thresholds. Generation of vertical cracks was successfully separated from horizontal cracks by a newly introduced scanning pattern of a plasma torch. Thus, generation of vertical cracks was detected with certainty by this monitoring method because AE events were detected only during spraying and a positive correlation was observed between the development degree of vertical cracks and the total AE energy in one experiment.

Ito, Kaita; Kuriki, Hitoshi; Araki, Hiroshi; Kuroda, Seiji; Enoki, Manabu

2014-06-01

426

Lu2O3-SiO2-ZrO2 Coatings for Environmental Barrier Application by Solution Precursor Plasma Spraying and Influence of Precursor Chemistry  

NASA Astrophysics Data System (ADS)

As environmental barrier coatings are subjected to thermal stress in gas turbine engines, the introduction of a secondary phase as zircon (ZrSiO4) is likely to increase the stress resistance of Lu2Si2O7 coatings generated by induction plasma spraying using liquid precursors. In a first step, precursor chemistry effect is investigated by the synthesis of ZrO2-SiO2 nanopowders by induction plasma nanopowder synthesis technique. Tetraethyl orthosilicate (TEOS) as silicon precursor and zirconium oxynitrate and zirconium ethoxide as zirconium precursors are mixed in ethanol and produce a mixture of tetragonal zirconia and amorphous silica nanoparticles. The use of zirconium ethoxide precursor results in zirconia particles with diameter below 50 nm because of exothermic thermal decomposition of the ethoxide and its high boiling point with respect to solvent, while larger particles are formed when zirconium oxynitrate is employed. The formation temperature of zircon from zirconia and silica oxides is found at 1425 C. Second, coatings are synthesized in Lu2O3-ZrO2-SiO2 system. After heat treatment, the doping effect of lutetium on zirconia grains totally inhibits the zircon formation. Dense coatings are obtained with the use of zirconium ethoxide because denser particles with a homogeneous diameter distribution constitute the coating.

Darthout, milien; Quet, Aurlie; Braidy, Nadi; Gitzhofer, Franois

2014-02-01

427

Sterilization and Mechanism of Microorganisms on A4 Paper by Dielectric Barrier Discharges Plasma at Atmospheric Pressure  

NASA Astrophysics Data System (ADS)

This study investigated the microorganisms' sterilization and mechanism by a DBD plasma device at atmospheric pressure. The device including a transfer system and two roller-electrodes is driven by sine-wave high voltages at frequencies of 15 kHz. Normal A4 papers were used to study the effects of the sterilization on their surfaces by analyzing the number of the living bacteria cells. The state of Escherichia coil's DNA were also measured by agarose gel electrophoresis after sterilization to analyze the inactivation mechanisms. Experimental results indicated that microorganisms on the surface of A4 Papers almost were destroyed while the papers went through the device and there was no any damage of the paper during the process. The main reason engendered bacteria death was due to the double chains of the DNA broken by the plasma.

Xianghong, Jia; Jun, Wan; Jinhua, Yang; Feng, Xu; Shouguo, Wang

2009-10-01

428

Microelectromechanical (MEM) thermal actuator  

DOEpatents

Microelectromechanical (MEM) buckling beam thermal actuators are disclosed wherein the buckling direction of a beam is constrained to a desired direction of actuation, which can be in-plane or out-of-plane with respect to a support substrate. The actuators comprise as-fabricated, linear beams of uniform cross section supported above the substrate by supports which rigidly attach a beam to the substrate. The beams can be heated by methods including the passage of an electrical current through them. The buckling direction of an initially straight beam upon heating and expansion is controlled by incorporating one or more directional constraints attached to the substrate and proximal to the mid-point of the beam. In the event that the beam initially buckles in an undesired direction, deformation of the beam induced by contact with a directional constraint generates an opposing force to re-direct the buckling beam into the desired direction. The displacement and force generated by the movement of the buckling beam can be harnessed to perform useful work, such as closing contacts in an electrical switch.

Garcia, Ernest J. (Albuquerque, NM); Fulcher, Clay W. G. (Sandia Park, NM)

2012-07-31

429

Telescoping cylindrical piezoelectric fiber composite actuator assemblies  

NASA Technical Reports Server (NTRS)

A telescoping actuator assembly includes a plurality of cylindrical actuators in a concentric arrangement. Each cylindrical actuator is at least one piezoelectric fiber composite actuator having a plurality of piezoelectric fibers extending parallel to one another and to the concentric arrangement's longitudinal axis. Each cylindrical actuator is coupled to concentrically-adjacent ones of the cylindrical actuators such that the plurality of cylindrical actuators can experience telescopic movement. An electrical energy source coupled to the cylindrical actuators applies actuation energy thereto to generate the telescopic movement.

Allison, Sidney G. (Inventor); Shams, Qamar A. (Inventor); Fox, Robert L. (Inventor); Fox, legal representative, Christopher L. (Inventor); Fox Chattin, legal representative, Melanie L. (Inventor)