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Sample records for gas flow sputtering

  1. Influence of argon gas flow on mechanical and electrical properties of sputtered titanium nitride thin films

    NASA Astrophysics Data System (ADS)

    Khojier, Kaykhosrow; Savaloni, Hadi; Shokrai, Ebrahim; Dehghani, Zohreh; Dehnavi, Naser Zare

    2013-07-01

    Titanium nitrides have good mechanical, tribological, electrical, biomedical, and optical properties; therefore, they are used to harden and protect cutting and sliding surfaces, as semiconductor devices, and as a nontoxic exterior for biomedical applications. The dependence of the mechanical and electrical properties of titanium nitride thin films deposited on silicon substrates by direct-current reactive magnetron sputtering technique on argon gas flow (in the range of 8 to 20 sccm) was investigated. The crystallographic structure of the films was studied by X-ray diffraction (XRD), while surface morphology was studied using atomic force microscopy (AFM). Mechanical and electrical properties of these films were investigated by nanoindentation test and a four-point probe instrument, respectively. The XRD patterns showed titanium nitride (TiN) formation with a face-centered cubic structure for all samples. It was also observed that (111) crystallographic direction was the preferred orientation for TiN thin films which became more pronounced with increasing argon gas flow. The AFM images showed a granular structure for TiN layers. The hardness, crystallite/grain size (obtained from XRD and AFM), and surface roughness increased with the flow of argon gas, while elastic modulus and dislocation density in the films decreased. The study on electrical properties showed that the dependence of voltage with current for all samples was linear, and film resistivity was increased with argon gas flow.

  2. Gas Flow Sputtered Thick Layers of Columnar Lead Zirconate Titanate on Silicon Wafers for High Frequency Ultrasound Transducers

    NASA Astrophysics Data System (ADS)

    Tiefensee, F.; Kaden, D.; Jakob, A.; Quenzer, H. J.; Jung, Th.

    The piezoelectric ceramic PZT, lead zirconate titanate, is the most spread material to generate ultrasound in medical and technical applications. Thereby frequencies between 30 MHz and 100 MHz require ceramic thicknesses between 50 μm and 20 μm. The presented gas flow sputtering process permits to deposit PZT of this thickness with a sputtering rate of 100 nm/min at temperatures between 520 °C and 550 °C. The PZT shows a typical columnar structure with a piezoelectric coefficient d33f of about 500 pm/V. An example for the fabrication ultrasound arrays with this sputtering process and lithographic structuring is given.

  3. The influence of pressure and gas flow on size and morphology of titanium oxide nanoparticles synthesized by hollow cathode sputtering

    NASA Astrophysics Data System (ADS)

    Gunnarsson, Rickard; Pilch, Iris; Boyd, Robert D.; Brenning, Nils; Helmersson, Ulf

    2016-07-01

    Titanium oxide nanoparticles have been synthesized via sputtering of a hollow cathode in an argon atmosphere. The influence of pressure and gas flow has been studied. Changing the pressure affects the nanoparticle size, increasing approximately proportional to the pressure squared. The influence of gas flow is dependent on the pressure. In the low pressure regime (107 ≤ p ≤ 143 Pa), the nanoparticle size decreases with increasing gas flow; however, at high pressure (p = 215 Pa), the trend is reversed. For low pressures and high gas flows, it was necessary to add oxygen for the particles to nucleate. There is also a morphological transition of the nanoparticle shape that is dependent on the pressure. Shapes such as faceted, cubic, and cauliflower can be obtained.

  4. On the dependence of structural and sensing properties of sputtered MoO3 thin films on argon gas flow

    NASA Astrophysics Data System (ADS)

    Khojier, K.; Savaloni, H.; Zolghadr, S.

    2014-11-01

    Nitrogen and carbon oxides (CO, NO and NO2), released from combustion facilities and automobiles, are known to be extremely harmful to the human body and also are the main cause of air pollution. Therefore, effective methods to monitor and suppress the carbon and nitrogen oxides have been highly demanded for atmospheric environmental measurements and controls. It is known that molybdenum oxide (MoO3) can be a good semiconductor material for use as a gas sensor in monitoring CO, NO and NO2. In this paper we report the structural characteristics and sensing properties of the sputtered MoO3 thin films as a function of argon gas flow. MoO3 thin films were deposited by DC reactive magnetron sputtering technique on glass substrates at different argon gas flows in the range of 5-20 sccm. X-ray diffraction (XRD) analysis was used for studying crystallographic structure. XRD results showed that all of our films were of polycrystalline structure and of α-MoO3 stable orthorhombic phase. Results also showed that crystallite size increases while compressive nano-strain in the structure of the films decreases with increasing the argon gas flow. Atomic force microscope and the field emission scanning electron microscope studies showed granular structures for all samples, which increased in size consistent with the XRD results, with argon gas flow, while the surface roughness of the films also increased with argon gas flow. Chemical composition study showed optimum reaction between oxygen and molybdenum atoms for films produced at 15 sccm flow of argon gas. The electrical response of samples was measured in the vacuum and the CO environments in the temperature range of 150-350 K. All samples showed Ohmic behavior and the electrical resistances of the films measured in the CO environment were lower than those measured in vacuum. This study showed that the sensing ability of MoO3 for CO improves with increasing the argon gas flow.

  5. Photocatalytic Properties of TiO2 Thin Films Modified with Ag and Pt Nanoparticles Deposited by Gas Flow Sputtering.

    PubMed

    Maicu, M; Glöss, D; Frach, Peter; Hecker, D; Gerlach, G; Córdoba, José M

    2015-09-01

    In this work, a gas flow sputtering (GFS) process which allows the production and deposition of metal nanoparticles (NPs) in a vacuum environment is described. Aim of the study is to prove the potential of this technology for the fabrication of new TiO2 films with enhanced photocatalytic properties. For this purpose, Ag and Pt NPs have been produced and deposited on photocatalytic float glass coated with TiO2 thin films by magnetron sputtering. The influence of the process parameters and of the metal amount on the final properties of the particles (quantity, size, size distribution, oxidation state etc.,) was widely investigated. Moreover, the effect of the NPs on the photocatalytic activity of the resulting materials was evaluated for the case of the decomposition of stearic acid (SA) during UV-A irradiation. The reduction of the water contact angle (WCA) during the irradiation period was measured in order to test the photo-induced super-hydrophilicity (PSH). PMID:26716202

  6. High rate deposition of photocatalytic TiO{sub 2} films with high activity by hollow cathode gas-flow sputtering method

    SciTech Connect

    Kubo, Yoshiyuki; Iwabuchi, Yoshinori; Yoshikawa, Masato; Sato, Yasushi; Shigesato, Yuzo

    2008-07-15

    Photocatalytic TiO{sub 2} films were deposited by a hollow cathode gas-flow sputtering method using two Ti metal targets mounted parallel to each other. The Ar and O{sub 2} flow rates were 3000 and 0-50 SCCM (SCCM denotes cubic centimeter per minute at STP), respectively, and total gas pressure during the deposition was maintained at 45 Pa. The highest deposition rate for the photocatalytic TiO{sub 2} films was 162 nm/min at 30 SCCM of O{sub 2} flow. The as-deposited films and postannealed films, annealed in air at 300 deg. C for 1 h, were used to carry out photocatalytic decomposition of acetaldehyde (CH{sub 3}CHO). In particular, the postannealed films showed extremely high photocatalytic activity compared to the photocatalytic activity of films deposited by conventional reactive sputtering.

  7. Visible-light active thin-film WO{sub 3} photocatalyst with controlled high-rate deposition by low-damage reactive-gas-flow sputtering

    SciTech Connect

    Oka, Nobuto Murata, Akiyo; Nakamura, Shin-ichi; Jia, Junjun; Shigesato, Yuzo; Iwabuchi, Yoshinori; Kotsubo, Hidefumi

    2015-10-01

    A process based on reactive gas flow sputtering (GFS) for depositing visible-light active photocatalytic WO{sub 3} films at high deposition rates and with high film quality was successfully demonstrated. The deposition rate for this process was over 10 times higher than that achieved by the conventional sputtering process and the process was highly stable. Furthermore, Pt nanoparticle-loaded WO{sub 3} films deposited by the GFS process exhibited much higher photocatalytic activity than those deposited by conventional sputtering, where the photocatalytic activity was evaluated by the extent of decomposition of CH{sub 3}CHO under visible light irradiation. The decomposition time for 60 ppm of CH{sub 3}CHO was 7.5 times more rapid on the films deposited by the GFS process than on the films deposited by the conventional process. During GFS deposition, there are no high-energy particles bombarding the growing film surface, whereas the bombardment of the surface with high-energy particles is a key feature of conventional sputtering. Hence, the WO{sub 3} films deposited by GFS should be of higher quality, with fewer structural defects, which would lead to a decrease in the number of centers for electron-hole recombination and to the efficient use of photogenerated holes for the decomposition of CH{sub 3}CHO.

  8. Visible-light active thin-film WO3 photocatalyst with controlled high-rate deposition by low-damage reactive-gas-flow sputtering

    NASA Astrophysics Data System (ADS)

    Oka, Nobuto; Murata, Akiyo; Nakamura, Shin-ichi; Jia, Junjun; Iwabuchi, Yoshinori; Kotsubo, Hidefumi; Shigesato, Yuzo

    2015-10-01

    A process based on reactive gas flow sputtering (GFS) for depositing visible-light active photocatalytic WO3 films at high deposition rates and with high film quality was successfully demonstrated. The deposition rate for this process was over 10 times higher than that achieved by the conventional sputtering process and the process was highly stable. Furthermore, Pt nanoparticle-loaded WO3 films deposited by the GFS process exhibited much higher photocatalytic activity than those deposited by conventional sputtering, where the photocatalytic activity was evaluated by the extent of decomposition of CH3CHO under visible light irradiation. The decomposition time for 60 ppm of CH3CHO was 7.5 times more rapid on the films deposited by the GFS process than on the films deposited by the conventional process. During GFS deposition, there are no high-energy particles bombarding the growing film surface, whereas the bombardment of the surface with high-energy particles is a key feature of conventional sputtering. Hence, the WO3 films deposited by GFS should be of higher quality, with fewer structural defects, which would lead to a decrease in the number of centers for electron-hole recombination and to the efficient use of photogenerated holes for the decomposition of CH3CHO.

  9. Magnetic properties of iron nitride films prepared by oblique sputtering under different nitrogen gas flow ratios (N2/N2+Ar)

    NASA Astrophysics Data System (ADS)

    Li, Xiaoyu; Du, Jinlu; Sun, Xiaojun; Wang, Jianbo; Liu, Qingfang

    2015-10-01

    Iron nitride thin films were prepared on Si (100) substrates by oblique radio-frequency reactive magnetron oblique sputtering. Structures, phases and magnetic properties were investigated as a function of nitrogen gas flow ratio FN(FN=FN2/(FN2+FAr)×100%). When FN is in the range of 2-7%, the iron nitride films show amorphous or nano-crystalline structures, which exhibit good soft magnetic properties. With 3%≤FN≤6%, films show in-plane uniaxial magnetic anisotropy. Both intrinsic damping factor αin and extrinsic damping factor αex of the iron nitride films increase with increasing FN. The film deposited under FN=6% with the resonance frequency fr=3.3 GHz and full width at half-maximum Δf=3.6 GHz has great potential for high-frequency electromagnetic shielding applications.

  10. Preparation of a heteroepitaxial LaxSryMnzO3/BiFeO3 bilayer by r.f. magnetron sputtering with various oxygen gas flow ratios

    NASA Astrophysics Data System (ADS)

    Naganuma, H.; Ichinose, T.; Begum, H. A.; Sato, S.; Han, X. F.; Miyazaki, T.; Bae, In-T.; Oogane, M.; Ando, Y.

    2014-08-01

    BiFeO3 (BFO) and LaxSryMnzO3 (LSMO) films were epitaxially grown on SrTiO3 (100) substrates by r.f. magnetron sputtering with various oxygen gas flow ratios (FO2). Compositional ratios of each atom in both of BFO and LSMO could be controlled kept to around 10 at.% by changing FO2. Adjusting the compositional ratio to La0.35Sr0.15Mn0.5O3 not only increase Tc of LSMO but also produces sufficient oxygen to form a perovskite lattice. For an LSMO/BFO heterostructure, detailed observation by cross sectional transmission electron microscopy (TEM) revealed that the lattice of rhombohedral (SG: R-3c) LSMO was shrank by a clamping effect from the SrTiO3 substrates, and then the BFO was grown in two layers: (i) an interfacial BFO layer (7 nm thick) with evenly shrunk a-axis and c-axis, and (ii) an upper BFO layer (25 nm thick) expanded along the c-axis. Neither misfit strain nor dislocations appeared at the interface between the shrunken BFO and LSMO layers, and these heterostructures did not show exchange bias. These results suggest that BFO is suitable for a tunneling barrier combine with LSMO electrode.

  11. Reactive sputtering of titanium in Ar/CH4 gas mixture: Target poisoning and film characteristics

    SciTech Connect

    Fouad, O.A.; Rumaiz, A.; Shah, S.

    2009-03-01

    Reactive sputtering of titanium target in the presence of Ar/CH{sub 4} gas mixture has been investigated. With the addition of methane gas to above 1.5% of the process gas a transition from the metallic sputtering mode to the poison mode was observed as indicated by the change in cathode current. As the methane gas flow concentration increased up to 10%, the target was gradually poisoned. The hysteresis in the cathode current could be plotted by first increasing and then subsequently decreasing the methane concentration. X-ray diffraction and X-ray photoelectron spectroscopy analyses of the deposited films confirmed the formation of carbide phases and the transition of the process from the metallic to compound sputtering mode as the methane concentration in the sputtering gas is increased. The paper discusses a sputtering model that gives a rational explanation of the target poisoning phenomenon and shows an agreement between the experimental observations and calculated results.

  12. Sputtering

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1976-01-01

    The potential of using the sputtering process as a deposition technique is reviewed; however, the manufacturing and sputter etching aspects are also discussed. The basic mechanism for dc and rf sputtering is described. Sputter deposition is presented in terms of the unique advantageous features it offers such as versatility, momentum transfer, stoichiometry, sputter etching, target geometry (coating and complex surfaces), precise controls, flexibility, ecology, and sputtering rates. Sputtered film characteristics, such as strong adherence and coherence and film morphology, are briefly evaluated in terms of varying the sputtering parameters. Also discussed are some of the specific industrial areas which are turning to sputter deposition techniques.

  13. In vitro flow measurements in ion sputtered hydrocephalus shunts

    NASA Technical Reports Server (NTRS)

    Cho, Y. I.; Back, L. H.

    1989-01-01

    This paper describes an experimental procedure for accurate measurements of the pressure-drop/flow rate relationship in hydrocephalus shunts. Using a fish-hook arrangement, small flow rates in a perforated ion-sputtered Teflon microtubule were measured in vitro in a pressured system and were correlated with pressure in the system. Results indicate that appropriate drainage rates could be obtained in the physiological range for hydrocephalus shunts.

  14. Cluster Growth Mechanism in Sputtering Gas-Aggregation Nanocluster Source

    NASA Astrophysics Data System (ADS)

    Tarsem Singh, M.; Han, H.; Sundararajan, J. A.; Qiang, Y.

    2010-03-01

    We have studied the influence of some parameters for cluster growth of core shell iron- iron oxide magnetic nanoparticles (MNPs). The nanocluster source which combines a magnetron sputtering gun with a gas aggregation chamber is used to produce MNPs. Nanoclusters of various mean sizes ranging from 1-100 nm can be synthesized by varying the aggregation distance, Ar to He gas ratio, pressure in the aggregation tube, sputter power, and temperature of the aggregation tube. Physical properties -- magnetic measurements by VSM and SQUID and size distribution by SEM and TEM were studied for different MNPs. The significance of this research is to understand the growth mechanism and physical properties as the size of particles grow from few nanometer to hundred of nanometer. Growth of the particles is theoretically explained by the homogenous and heterogeneous growth process. Based on this study, different size of MNPs fits into different category of applications from data storage to biomedical field.

  15. Using sputter coated glass to stabilize microstrip gas chambers

    DOEpatents

    Gong, Wen G.

    1997-01-01

    By sputter coating a thin-layer of low-resistive, electronically-conductive glass on various substrates (including quartz and ceramics, thin-film Pestov glass), microstrip gas chambers (MSGC) of high gain stability, low leakage current, and a high rate capability can be fabricated. This design can make the choice of substrate less important, save the cost of ion-implantation, and use less glass material.

  16. Gas flow control valve

    SciTech Connect

    Phlipot, J.R.; Pinkston, S.R.; Nurre, H.

    1988-02-09

    A compact gas flow control valve is described comprising a valve body having a first, rotor cavity-defining portion and a second cover portion covering the rotor cavity, at least one of the body portions including inlet means communicating with the rotor chamber for receiving gas under pressure for providing the gas to the rotor chamber, at least one of the body portions including outlet means for delivery of the gas by the flow control valve, a rotor within the rotor cavity, the rotor including a flat surface, a flow control plate carried by the rotor, the flow control plate covering and lying against the flat surface of the rotor, the rotor having ports opening through the rotor surface, the ports being of sufficiently large size as not to limit the flow of the gas therethrough. The flow control plate comprises a thin, flat metal disc provided with gas flow control orifices extending therethrough and spaced circumferentially around the disc and in registry with respective ones of the ports, the rotor being of substantially greater thickness than the disc, the gas flow control being of different sizes and passage means for providing communication between the outlet means and at least a selected one of the flow control plate origices, selector means for orienting the rotor to permit flow only through selected flow control plate orifices and a corresponding rotor port for delivery by the outlet means.

  17. Gas flow through rotameters

    NASA Technical Reports Server (NTRS)

    Levin, H.; Escorza, M. M.

    1983-01-01

    Using data available for small rotameters that use spherical floats in gas flow, a linear relationship is derived. It is noted that the relationship provides a good fit for variable volumetric flow, density, and viscosity at constant flow height. With low Reynolds numbers (Re being less than 1), the product of the variable volumetric flow and the viscosity becomes constant; at high Reynolds numbers (Re being greater than 2000), the product of the variable volumetric flow and the square root of the density becomes constant. It is pointed out that the equation given here can be used to obtain an indirect calibration with any gas of known density and viscosity. The constancy of the product of the variable volumetric flow and viscosity at low variable volumetric flows is seen as suggesting the development of simple, inexpensive gas viscometers using rotameter technology.

  18. Paraelectric gas flow accelerator

    NASA Technical Reports Server (NTRS)

    Sherman, Daniel M. (Inventor); Wilkinson, Stephen P. (Inventor); Roth, J. Reece (Inventor)

    2001-01-01

    A substrate is configured with first and second sets of electrodes, where the second set of electrodes is positioned asymmetrically between the first set of electrodes. When a RF voltage is applied to the electrodes sufficient to generate a discharge plasma (e.g., a one-atmosphere uniform glow discharge plasma) in the gas adjacent to the substrate, the asymmetry in the electrode configuration results in force being applied to the active species in the plasma and in turn to the neutral background gas. Depending on the relative orientation of the electrodes to the gas, the present invention can be used to accelerate or decelerate the gas. The present invention has many potential applications, including increasing or decreasing aerodynamic drag or turbulence, and controlling the flow of active and/or neutral species for such uses as flow separation, altering heat flow, plasma cleaning, sterilization, deposition, etching, or alteration in wettability, printability, and/or adhesion.

  19. Gas flow meter and method for measuring gas flow rate

    DOEpatents

    Robertson, Eric P.

    2006-08-01

    A gas flow rate meter includes an upstream line and two chambers having substantially equal, fixed volumes. An adjustable valve may direct the gas flow through the upstream line to either of the two chambers. A pressure monitoring device may be configured to prompt valve adjustments, directing the gas flow to an alternate chamber each time a pre-set pressure in the upstream line is reached. A method of measuring the gas flow rate measures the time required for the pressure in the upstream line to reach the pre-set pressure. The volume of the chamber and upstream line are known and fixed, thus the time required for the increase in pressure may be used to determine the flow rate of the gas. Another method of measuring the gas flow rate uses two pressure measurements of a fixed volume, taken at different times, to determine the flow rate of the gas.

  20. Gas Flow Detection System

    NASA Technical Reports Server (NTRS)

    Moss, Thomas; Ihlefeld, Curtis; Slack, Barry

    2010-01-01

    This system provides a portable means to detect gas flow through a thin-walled tube without breaking into the tubing system. The flow detection system was specifically designed to detect flow through two parallel branches of a manifold with only one inlet and outlet, and is a means for verifying a space shuttle program requirement that saves time and reduces the risk of flight hardware damage compared to the current means of requirement verification. The prototype Purge Vent and Drain Window Cavity Conditioning System (PVD WCCS) Flow Detection System consists of a heater and a temperature-sensing thermistor attached to a piece of Velcro to be attached to each branch of a WCCS manifold for the duration of the requirement verification test. The heaters and thermistors are connected to a shielded cable and then to an electronics enclosure, which contains the power supplies, relays, and circuit board to provide power, signal conditioning, and control. The electronics enclosure is then connected to a commercial data acquisition box to provide analog to digital conversion as well as digital control. This data acquisition box is then connected to a commercial laptop running a custom application created using National Instruments LabVIEW. The operation of the PVD WCCS Flow Detection System consists of first attaching a heater/thermistor assembly to each of the two branches of one manifold while there is no flow through the manifold. Next, the software application running on the laptop is used to turn on the heaters and to monitor the manifold branch temperatures. When the system has reached thermal equilibrium, the software application s graphical user interface (GUI) will indicate that the branch temperatures are stable. The operator can then physically open the flow control valve to initiate the test flow of gaseous nitrogen (GN2) through the manifold. Next, the software user interface will be monitored for stable temperature indications when the system is again at

  1. Tuning of magnetization dynamics in sputtered CoFeB thin film by gas pressure

    NASA Astrophysics Data System (ADS)

    Xu, Feng; Huang, Qijun; Liao, Zhiqin; Li, Shandong; Ong, C. K.

    2012-04-01

    The influences of sputtering gas pressure on the high-frequency magnetization dynamics of as-sputtered CoFeB thin films are studied with permeability spectra based on the Landau-Lifshitz-Gilbert (LLG) equation. Results show that with the pressure increasing, both the anisotropy field and resonance frequency have minimums, while the initial permeability shows a maximum. The damping factor deceases monotonously with the pressure increasing, similar as with the coercivity. The high tunability of the damping factor indicates that controlling sputtering gas pressure could be an effective method in tuning the magnetization dynamics. All these dependences on gas pressure are suggested to be related to the inner stress of these sputtered films.

  2. Effect of gas ratio on tribological properties of sputter deposited TiN coatings

    NASA Astrophysics Data System (ADS)

    Chavda, Mahesh R.; Chauhan, Kamlesh V.; Rawal, Sushant K.

    2016-05-01

    Titanium nitride (TiN) coatings were deposited on Si, corning glass, pins of mild steel (MS, ϕ3mm), aluminium (Al, ϕ4mm) and brass (ϕ6mm) substratesby DC magnetron sputtering. The argon and nitrogen (Ar:N2)gas ratio was precisely controlled by Mass Flow Controller (MFC) and was varied systematically at diffract values of 10:10,12:08, 16:04 and 18:02sccm. The structural properties of TiN coatings were characterized by X-ray diffraction (XRD) and its surface topography was studied using field emission scanning electron microscopy (FE-SEM). The tribological properties of TiN coatings were investigated using pin-on-disc tribometer.

  3. Comprehensive computer model for magnetron sputtering. I. Gas heating and rarefaction

    SciTech Connect

    Jimenez, Francisco J.; Dew, Steven K.

    2012-07-15

    The complex interaction between several variables in magnetron sputtering discharges is a challenge in developing engineering design tools for industrial applications. For instance, at high pressures, rarefaction and gas heating should no longer be neglected for determining several parameters of the process. In this article, we use a comprehensive 3D reactor-scale simulator that incorporates most phenomena of interest in a self-consistent manner to simulate the transport of sputtered particles over a wide range of pressures and powers. Calculations of aluminum deposition rates and metal vapor densities are in reasonable agreement with experiments over a wide range of pressures and powers. Of the elements investigated (Al, Ti, and Cu), copper showed the greatest rarefaction (30%) due to its higher sputtering yield. Titanium, despite a slightly lower sputtering yield than Al, shows a greater rarefaction than aluminum as more particles are reflected from the target as high energy neutrals. In this case, a more efficient energy transfer process is responsible for the higher rarefaction observed in Ti sputtering when compared to Al. The authors also observed that by sputtering at a higher pressure, the probability of electron impact ionization of sputtered particles is increased and speculate about the role of this process in contrast to penning ionization, which is believed to be the dominant ionization mechanism in magnetron sputtering.

  4. Noble gas incorporation in sputtered and ion beam assisted grown silicon films

    SciTech Connect

    van Veen, A. . Inter-Faculty Reactor Inst.); Greuter, M.J.W.; Niesen, L. . Dept. of Physics); Nielsen, B.; Lynn, K.G. )

    1991-01-01

    Gas desorption measurements have been performed on sputter deposited silicon films. The sputter gas was argon or krypton. Parameters influencing the incorporation process e.g. bias voltage, substrate temperature and arrival rate ratio of silicon and noble gas atoms have been systematically varied. The films, a-Si and c-Si, have been characterised by various techniques for composition and defect analysis. A model has been applied to describe the composition of the growing silicon layer. Underlying mechanisms like gas-gas sputtering have been studied in separate ion implantation experiments. For a-Si concentrations as high as 6% Ar and Kr have been found. An important effect is the injection of self-interstitial atoms caused by the low energy heavy ion bombardment. It causes the layer to grow without large open volume defects.

  5. Noble gas incorporation in sputtered and ion beam assisted grown silicon films

    SciTech Connect

    van Veen, A.; Greuter, M.J.W.; Niesen, L.; Nielsen, B.; Lynn, K.G.

    1991-12-31

    Gas desorption measurements have been performed on sputter deposited silicon films. The sputter gas was argon or krypton. Parameters influencing the incorporation process e.g. bias voltage, substrate temperature and arrival rate ratio of silicon and noble gas atoms have been systematically varied. The films, a-Si and c-Si, have been characterised by various techniques for composition and defect analysis. A model has been applied to describe the composition of the growing silicon layer. Underlying mechanisms like gas-gas sputtering have been studied in separate ion implantation experiments. For a-Si concentrations as high as 6% Ar and Kr have been found. An important effect is the injection of self-interstitial atoms caused by the low energy heavy ion bombardment. It causes the layer to grow without large open volume defects.

  6. Effect Of Process Gas Mixture On Reactively DC Magnetron Sputtered (Al1_xSix)OyNz Thin Films

    NASA Astrophysics Data System (ADS)

    Bjornard, Erik

    1989-02-01

    (A1 1-x Si x )0yNz films have properties which make them desirable as durable overcoats and corrosion barriers in optical thin film structures. (Al, Si )O N films were reactively DC sputtered from Al, Si targets (x = 0.0, 0.117, 0.30) in Ar/N2/O2 atmospheres. Nitride films had sputter efficiencies three times that of the oxides and ESCA analysis of the films showed that the film composition varied non-linearly with reactive gas ratio and sputter rate, incorporating more oxygen than nitrogen for a given gas flow. This behavior is correlated with the hysteresis curves for the oxide and nitride states. Optical properties of the films were also found to vary with index dropping disproportionately to the 0/(0+N) flow ratio, but linearly with the ratio of atomic percent of 0 and N in the films. Durability properties of (A1 1_x Si x)0 NZ films were tested at several compositions. It was found that with high nitrogen context the wear resistance increased with Si content and the oxides were generally less wear resistant than the nitrides. The corrosion resistance also increased with Si content, but in this case, the oxides were generally more stable. Film stress became more compressive with 0 and Si content. Analysis of ESCA binding energy data indicates that the Si forms alumino-silicate bonds in the film, which apparently contributes to the durability properties.

  7. Influence of oxygen concentration in sputtering gas on piezoelectric response of aluminum nitride thin films

    SciTech Connect

    Akiyama, Morito; Kamohara, Toshihiro; Kano, Kazuhiko; Teshigahara, Akihiko; Kawahara, Nobuaki

    2008-07-14

    The authors have investigated the influence of oxygen concentration in sputtering gas on the piezoelectric response of aluminum nitride (AlN) thin films prepared on silicon substrates. The piezoelectric response strongly depends on the oxygen concentration, and changes from +6.8 to -7.0 pC/N with increasing oxygen concentration from 0% to 1.2%. The polar direction drastically inverts from the Al polarity to N polarity. When the oxygen concentration in sputtering gas was 1.2%, the oxygen concentration in the AlN films was 7 at. %. Furthermore, the growth rate of the AlN films gradually decreases with increasing oxygen concentration in sputtering gas.

  8. High gas flow alpha detector

    DOEpatents

    Bolton, R.D.; Bounds, J.A.; Rawool-Sullivan, M.W.

    1996-05-07

    An alpha detector for application in areas of high velocity gas flows, such as smokestacks and air vents. A plurality of spaced apart signal collectors are placed inside an enclosure, which would include smokestacks and air vents, in sufficient numbers to substantially span said enclosure so that gas ions generated within the gas flow are electrostatically captured by the signal collector means. Electrometer means and a voltage source are connected to the signal collectors to generate an electrical field between adjacent signal collectors, and to indicate a current produced through collection of the gas ions by the signal collectors. 4 figs.

  9. High gas flow alpha detector

    DOEpatents

    Bolton, Richard D.; Bounds, John A.; Rawool-Sullivan, Mohini W.

    1996-01-01

    An alpha detector for application in areas of high velocity gas flows, such as smokestacks and air vents. A plurality of spaced apart signal collectors are placed inside an enclosure, which would include smokestacks and air vents, in sufficient numbers to substantially span said enclosure so that gas ions generated within the gas flow are electrostatically captured by the signal collector means. Electrometer means and a voltage source are connected to the signal collectors to generate an electrical field between adjacent signal collectors, and to indicate a current produced through collection of the gas ions by the signal collectors.

  10. Oscillatory electrohydrodynamic gas flows

    SciTech Connect

    Lai, F.C.; McKinney, P.J.; Davidson, J.H.

    1995-09-01

    Prior numerical solutions of electrohydrodynamic flows in a positive-corona, wire-plate electrostatic precipitator are extended to reveal steady-periodic electrohydrodynamic flows. Previously, only steady solutions were reported. The present study includes results for flows with Reynolds numbers from 0 to 4,800 and with dimensionless electric number ranging from 0.06 to {infinity}. Results indicate that two regimes of low frequency oscillatory flow occur. The first regime is characterized by a single recirculating vortex that oscillates in strength between one and five Hertz. The second regime is characterized by two counter-rotating vortices that oscillate in strength at a frequency near one Hertz.

  11. Optical-emission studies on the interaction between halogenated carbon species and noble gas during fluoropolymer sputtering

    NASA Astrophysics Data System (ADS)

    Sugimoto, Iwao; Miyake, Shojiro

    1989-06-01

    Using optical-emission spectroscopy, the interaction between metastable-excited noble gas and fluorocarbon species is investigated for poly-chloro-tri-fluoro-ethylene (PCTFE) sputtering under a mixture of noble gas and CF3Cl gas flow conditions. Among a variety of noble gases, He and Ne in an excited state were quenched through energy transfer which induced the ionization and self-decomposition of the halogenated carbon species. Such an inactivation was not observed in the Ar, Kr, and Xe cases, in accordance with the ionization energy in CF3Cl derived from photoelectron spectroscopy. Instability in a radio-frequency (rf) plasma was observed in the pure Xe case. However, the plasma was stabilized in the case of a mixture with CF3Cl. The CF2 band which is characteristic of PCTFE sputtering was not detected in the Xe case. In addition, it was confirmed that the oxygen introduced into the rf plasma was more likely to react with CF2(3B1) than with CF2(1B1) or CF3(1B1).

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  13. Gas flow through rough microchannels in the transition flow regime.

    PubMed

    Deng, Zilong; Chen, Yongping; Shao, Chenxi

    2016-01-01

    A multiple-relaxation-time lattice Boltzmann model of Couette flow is developed to investigate the rarified gas flow through microchannels with roughness characterized by fractal geometry, especially to elucidate the coupled effects of roughness and rarefaction on microscale gas flow in the transition flow regime. The results indicate that the surface roughness effect on gas flow behavior becomes more significant in rarefied gas flow with the increase of Knudsen number. We find the gas flow behavior in the transition flow regime is more sensitive to roughness height than that in the slip flow regime. In particular, the influence of fractal dimension on rarefied gas flow behavior is less significant than roughness height. PMID:26871175

  14. Argon inclusion in sputtered films and the effect of the gas on molybdenum field emitter arrays

    NASA Astrophysics Data System (ADS)

    Chalamala, Babu R.; Reuss, Robert H.

    2001-04-01

    Residual gas analysis of a number of field emission displays showed that argon desorbed from molybdenum metal lines was the dominant gas in sealed vacuum packages. We present experimental results on the emission characteristics of molybdenum field emitter arrays in argon ambient. In argon, the emission current dropped rapidly similar to that in oxygenic gas ambients. Existing degradation models do not provide an adequate explanation for this behavior. Rather, we suggest a model based on shallow implantation of argon into the field emitter tips that increases the effective width of the tunneling barrier. Experimental support for this model comes from the following observations: emission current degraded only when the device was turned on; after gas exposure, significant current recovery which followed diffusion type behavior was noted; degradation and recovery rates were functions of partial pressure; and no detectable effects associated with sputtering were observed. This mechanism is also consistent with ion pumping known to occur in field emission displays.

  15. Gas flow in barred potentials

    NASA Astrophysics Data System (ADS)

    Sormani, Mattia C.; Binney, James; Magorrian, John

    2015-05-01

    We use a Cartesian grid to simulate the flow of gas in a barred Galactic potential and investigate the effects of varying the sound speed in the gas and the resolution of the grid. For all sound speeds and resolutions, streamlines closely follow closed orbits at large and small radii. At intermediate radii shocks arise and the streamlines shift between two families of closed orbits. The point at which the shocks appear and the streamlines shift between orbit families depends strongly on sound speed and resolution. For sufficiently large values of these two parameters, the transfer happens at the cusped orbit as hypothesized by Binney et al. over two decades ago. For sufficiently high resolutions, the flow downstream of the shocks becomes unsteady. If this unsteadiness is physical, as appears to be the case, it provides a promising explanation for the asymmetry in the observed distribution of CO.

  16. Laser cross-flow gas system

    DOEpatents

    Duncan, David B.

    1992-01-01

    A method and laser apparatus are disclosed which provide for a cross-flow of gas near one end of a laser discharge tube. The cross-flow of gas causes a concentration gradient which affects diffusion of contaminants in the discharge tube towards the cross-flow of the gas, which contaminants are then withdrawn from the discharge tube.

  17. Preparation and characteristics of vanadium oxide thin films by controlling the sputtering voltage

    NASA Astrophysics Data System (ADS)

    Wei, Xiongbang; Li, Shibin; Gou, Jun; Dong, Xiang; Yang, Xiaohui; Li, Weizhi; Wang, Tao; Wu, Zhiming; Jiang, Yadong; Chen, Zhi

    2014-06-01

    Influence of sputtering voltage on the deposition process and characteristics of vanadium oxide thin films prepared by reactive DC magnetron sputtering is investigated. The target surface cleaning is controlled by adjusting the sputtering voltage. During the sputtering process, the sputtering voltage increases faster with larger O2 gas flow rate. The sputtering voltage is easy to be stable with larger sputtering voltage. The measured sputtering voltage is correlated to the ion induced secondary electron emission (ISEE) coefficient of the target material. The ISEE coefficient of the oxidized vanadium target surface is lower than the ISEE coefficient of the vanadium metal. The semiconductor to metal (S-M) phase transition temperature decreases with the sputtering voltage, leading to the lower the corresponding temperature of the maximum temperature coefficient of resistance (TCR). By this way, O/V ratio, R, and TCR of VOx films can be controlled by adjusting the sputtering voltage.

  18. Natural gas flow through critical nozzles

    NASA Technical Reports Server (NTRS)

    Johnson, R. C.

    1969-01-01

    Empirical method for calculating both the mass flow rate and upstream volume flow rate through critical flow nozzles is determined. Method requires knowledge of the composition of natural gas, and of the upstream pressure and temperature.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  1. Net sputtering rate due to hot ions in a Ne-Xe discharge gas bombarding an MgO layer

    SciTech Connect

    Ho, S.; Tamakoshi, T.; Ikeda, M.; Mikami, Y.; Suzuki, K.

    2011-04-15

    An analytical method is developed for determining net sputtering rate for an MgO layer under hot ions with low energy (<100 eV) in a neon-xenon discharge gas at near-atmospheric pressure. The primary sputtering rate is analyzed according to spatial and energy distributions of the hot ions with average energy, E{sup h}{sub i}, above a threshold energy of sputtering, E{sub th,i}, multiplied by a yield coefficient. The threshold energy of sputtering is determined from dissociation energy required to remove an atom from MgO surface multiplied by an energy-transfer coefficient. The re-deposition rate of the sputtered atoms is calculated by a diffusion simulation using a hybridized probabilistic and analytical method. These calculation methods are combined to analyze the net sputtering rate. Maximum net sputtering rate due to the hot neon ions increases above the partial pressure of 4% xenon as E{sup h}{sub Ne} becomes higher and decreases near the partial pressure of 20% xenon as ion flux of neon decreases. The dependence due to the hot neon ions on partial pressure and applied voltage agrees well with experimental results, but the dependence due to the hot xenon ions deviates considerably. This result shows that the net sputtering rate is dominated by the hot neon ions. Maximum E{sup h}{sub Ne} (E{sup h}{sub Ne,max} = 5.3 - 10.3 eV) is lower than E{sub th,Ne} (19.5 eV) for the MgO layer; therefore, weak sputtering due to the hot neon ions takes place. One hot neon ion sputters each magnesium and each oxygen atom on the surface and distorts around a vacancy. The ratio of the maximum net sputtering rate is approximately determined by number of the ions at E{sup h}{sub i,max} multiplied by an exponential factor of -E{sub th,i}/E{sup h}{sub i,max}.

  2. HVOF gas flow field characteristics

    SciTech Connect

    Swank, W.D.; Fincke, J.R.; Haggard, D.C.; Irons, G.

    1994-12-31

    The effects of combustion chamber pressure and fuel/oxygen mixture ratio on the characteristics of a high pressure, supersonic HVOF gun are examined experimentally and theoretically. The measured temperature, velocity and entrained air fraction are obtained from an enthalpy probe/mass spectrometer system. Predictions of combustion chamber flame temperature and composition are calculated with an equilibrium combustion model. Nozzle and barrel exit conditions are calculated using a one-dimensional rocket performance model. The calculations are bounded by the assumption of frozen and equilibrium compositions. Comparisons between measurements and the predictions indicate that the flow field is far from chemical equilibrium. The aerodynamic force available for accelerating a particle is primarily controlled by the chamber pressure while the composition and temperature of the gas surrounding the particles is controlled by the mixture ratio.

  3. Spark gap switch with spiral gas flow

    DOEpatents

    Brucker, John P.

    1989-01-01

    A spark gap switch having a contaminate removal system using an injected gas. An annular plate concentric with an electrode of the switch defines flow paths for the injected gas which form a strong spiral flow of the gas in the housing which is effective to remove contaminates from the switch surfaces. The gas along with the contaminates is exhausted from the housing through one of the ends of the switch.

  4. Swirling flow of a dissociated gas

    NASA Technical Reports Server (NTRS)

    Wolfram, W. R., Jr.; Walker, W. F.

    1975-01-01

    Most physical applications of the swirling flow, defined as a vortex superimposed on an axial flow in the nozzle, involve high temperatures and the possibility of real gas effects. The generalized one-dimensional swirling flow in a converging-diverging nozzle is analyzed for equilibrium and frozen dissociation using the ideal dissociating gas model. Numerical results are provided to illustrate the major effects and to compare with results obtained for a perfect gas with constant ratio of specific heats. It is found that, even in the case of real gases, perfect gas calculations can give a good estimate of the reduction in mass flow due to swirl.

  5. Advances in gas-liquid flows 1990

    SciTech Connect

    Kim, J.M. . Nuclear Reactor Lab.); Rohatgi, U.S. ); Hashemi, A. )

    1990-01-01

    Gas-liquid two-phase flows commonly occur in nature and industrial applications. Rain, clouds, geysers, and waterfalls are examples of natural gas-liquid flow phenomena, whereas industrial applications can be found in nuclear reactors, steam generators, boilers, condensers, evaporators, fuel atomization, heat pipes, electronic equipment cooling, petroleum engineering, chemical process engineering, and many others. The household-variety phenomena such as garden sprinklers, shower, whirlpool bath, dripping faucet, boiling tea pot, and bubbling beer provide daily experience of gas-liquid flows. The papers presented in this volume reflect the variety and richness of gas-liquid two-phase flow and the increasing role it plays in modern technology. This volume contains papers dealing with some recent development in gas-liquid flow science and technology, covering basic gas-liquid flows, measurements and instrumentation, cavitation and flashing flows, countercurrent flow and flooding, flow in various components and geometries liquid metals and thermocapillary effects, heat transfer, nonlinear phenomena, instability, and other special and general topics related to gas-liquid flows.

  6. Apparatus for focusing flowing gas streams

    DOEpatents

    Nogar, N.S.; Keller, R.A.

    1985-05-20

    Apparatus for focusing gas streams. The principle of hydrodynamic focusing is applied to flowing gas streams in order to provide sample concentration for improved photon and sample utilization in resonance ionization mass spectrometric analysis. In a concentric nozzle system, gas samples introduced from the inner nozzle into the converging section of the outer nozzle are focused to streams 50-250-..mu..m in diameter. In some cases diameters of approximately 100-..mu..m are maintained over distances of several centimeters downstream from the exit orifice of the outer nozzle. The sheath gas employed has been observed to further provide a protective covering around the flowing gas sample, thereby isolating the flowing gas sample from possible unwanted reactions with nearby surfaces. A single nozzle variation of the apparatus for achieving hydrodynamic focusing of gas samples is also described.

  7. Epitaxy of Pb(Zr, Ti)O3 films on Ir/YSZ/Si under conditions of cathode sputtering: The effect of reactive gas composition

    NASA Astrophysics Data System (ADS)

    Beshenkov, V. G.; Burlakov, A. A.; Znamenskii, A. G.; Marchenko, V. A.

    2014-08-01

    The peculiarities of the growth of PZT films on heteroepitaxial Ir/YSZ/Si structures under conditions of cathode radio-frequency sputtering of a ceramic target in argon-oxygen mixtures have been studied. It is shown that sputtering in a gas mixture with a high partial pressure of oxygen results in crystallization of the PZT films in a metastable pyrochlore structure, while sputtering in argon or the use of argon in the initial phase of the sputtering yields PZT films with an equilibrium perovskite structure.

  8. Flow rate measuring devices for gas flows

    NASA Astrophysics Data System (ADS)

    Bonfig, K. W.

    1985-07-01

    Flowrate measuring devices are described: volume meter with fixed or mobile walls; turbine meter; throttling procedure; ultrasonic and Doppler methods; vortex method; rotary flowmeter; and swinging body flow measuring procedure. Flowrate can also be measured from the force exerted on bodies immersed in a fluid or based on thermodynamical principles. The characteristics and operating envelope of each device/method are given.

  9. Liquid/Gas Flow Mixers

    NASA Technical Reports Server (NTRS)

    Fabris, Gracio

    1994-01-01

    Improved devices mix gases and liquids into bubbly or foamy flows. Generates flowing, homogeneous foams or homogeneous dispersions of small, noncoalescing bubbles entrained in flowing liquids. Mixers useful in liquid-metal magnetohydrodynamic electric-power generator, froth flotation in mining industry, wastewater treatment, aerobic digestion, and stripping hydrocarbon contaminants from ground water.

  10. Slip length measurement of gas flow.

    PubMed

    Maali, Abdelhamid; Colin, Stéphane; Bhushan, Bharat

    2016-09-16

    In this paper, we present a review of the most important techniques used to measure the slip length of gas flow on isothermal surfaces. First, we present the famous Millikan experiment and then the rotating cylinder and spinning rotor gauge methods. Then, we describe the gas flow rate experiment, which is the most widely used technique to probe a confined gas and measure the slip. Finally, we present a promising technique using an atomic force microscope introduced recently to study the behavior of nanoscale confined gas. PMID:27505860

  11. Slip length measurement of gas flow

    NASA Astrophysics Data System (ADS)

    Maali, Abdelhamid; Colin, Stéphane; Bhushan, Bharat

    2016-09-01

    In this paper, we present a review of the most important techniques used to measure the slip length of gas flow on isothermal surfaces. First, we present the famous Millikan experiment and then the rotating cylinder and spinning rotor gauge methods. Then, we describe the gas flow rate experiment, which is the most widely used technique to probe a confined gas and measure the slip. Finally, we present a promising technique using an atomic force microscope introduced recently to study the behavior of nanoscale confined gas.

  12. Laser-induced fluorescence monitoring of the gas phase in a glow discharge during reactive sputtering of vanadium

    NASA Astrophysics Data System (ADS)

    Khvostikov, V. A.; Grazhulene, S. S.; Burmii, Zh. P.; Marchenko, V. A.

    2011-11-01

    Processes in the gas phase of a glow discharge during diode and magnetron reactive sputtering of vanadium in an Ar-O2 atmosphere have been investigated by laser-induced fluorescence (LIF) as a function of the parameters of the glow discharge and the composition of the atmosphere. The intensity of the fluorescence spectra increased by 1.5-2.0 orders of magnitude in the magnetron sputtering process compared with that of diode sputtering. Under continuous sputtering conditions, the dependences of the intensities and relative compositions of the fluorescence spectra on the discharge parameters (discharge voltage and current) have been investigated. In pulsed mode of the glow discharge, the dynamics of changes in the spectra have been studied versus variations in the discharge duration and the lag time for recording the fluorescence signal. The dependence of the spectral line intensities on the partial pressure of oxygen has been found for vanadium and its oxide. The cathode surface at pressures of 0.03-0.04 Pa was shown to convert to the oxidized state.

  13. Mechanism of Hydrogenated Microcrystalline Si Film Deposition by Magnetron Sputtering Employing a Si Target and H2/Ar Gas Mixture

    NASA Astrophysics Data System (ADS)

    Fukaya, Kota; Tabata, Akimori; Sasaki, Koichi

    2009-03-01

    The mechanism of hydrogenated microcrystalline silicon (µc-Si:H) film deposition by magnetron sputtering employing a Si target and H2/Ar gas mixture has been investigated by measuring Si and H atom densities in the gas phase by laser-induced fluorescence spectroscopy. The crystalline volume fraction of the film correlated positively with H atom density. The variation in Si atom density indicated the increase in sputtering yield from the Si target in the H2/Ar discharge. The surface of the Si target immersed in the H2/Ar discharge was hydrogenated. Therefore, it is reasonable to expect the production of SiHx molecules (typically SiH4) from the hydrogenated Si target via reactive ion etching. Since SiHx molecules produced from the target may function as a deposition precursor, the mechanism of µc-Si:H film deposition is considered to be similar to that of plasma-enhanced chemical vapor deposition (PECVD) employing a SiH4/H2 gas mixture. The advantage of magnetron sputtering deposition over PECVD is the production of SiHx molecules without using toxic, explosive SiH4.

  14. Formation Mechanism of Fe Nanocubes by Magnetron Sputtering Inert Gas Condensation.

    PubMed

    Zhao, Junlei; Baibuz, Ekaterina; Vernieres, Jerome; Grammatikopoulos, Panagiotis; Jansson, Ville; Nagel, Morten; Steinhauer, Stephan; Sowwan, Mukhles; Kuronen, Antti; Nordlund, Kai; Djurabekova, Flyura

    2016-04-26

    In this work, we study the formation mechanisms of iron nanoparticles (Fe NPs) grown by magnetron sputtering inert gas condensation and emphasize the decisive kinetics effects that give rise specifically to cubic morphologies. Our experimental results, as well as computer simulations carried out by two different methods, indicate that the cubic shape of Fe NPs is explained by basic differences in the kinetic growth modes of {100} and {110} surfaces rather than surface formation energetics. Both our experimental and theoretical investigations show that the final shape is defined by the combination of the condensation temperature and the rate of atomic deposition onto the growing nanocluster. We, thus, construct a comprehensive deposition rate-temperature diagram of Fe NP shapes and develop an analytical model that predicts the temporal evolution of these properties. Combining the shape diagram and the analytical model, morphological control of Fe NPs during formation is feasible; as such, our method proposes a roadmap for experimentalists to engineer NPs of desired shapes for targeted applications. PMID:26962973

  15. Cleanouts boost Devonian shale gas flow

    SciTech Connect

    Not Available

    1991-02-04

    Cleaning shale debris from the well bores is an effective way to boost flow rates from old open hole Devonian shale gas wells, research on six West Virginia wells begun in 1985 has shown. Officials involved with the study say the Appalachian basin could see 20 year recoverable gas reserves hiked by 315 bcf if the process is used on a wide scale.

  16. A method of determining combustion gas flow

    NASA Technical Reports Server (NTRS)

    Bon Tempi, P. J.

    1968-01-01

    Zirconium oxide coating enables the determination of hot gas flow patterns on liquid rocket injector face and baffle surfaces to indicate modifications that will increase performance and improve combustion stability. The coating withstands combustion temperatures and due to the coarse surface and coloring of the coating, shows the hot gas patterns.

  17. Fluorescent particles enable visualization of gas flow

    NASA Technical Reports Server (NTRS)

    Wilson, A. J.

    1968-01-01

    Fluorescent particles enable visualization of the flow patterns of gases at slow velocities. Through a transparent section in the gas line, a camera views the visible light emitted by the particles carried by the gas stream. Fine definition of the particle tracks are obtained at slow camera shutter speeds.

  18. Water and methanol in low-mass protostellar outflows: gas-phase synthesis, ice sputtering and destruction

    NASA Astrophysics Data System (ADS)

    Suutarinen, A. N.; Kristensen, L. E.; Mottram, J. C.; Fraser, H. J.; van Dishoeck, E. F.

    2014-05-01

    Water in outflows from protostars originates either as a result of gas-phase synthesis from atomic oxygen at T ≳ 200 K, or from sputtered ice mantles containing water ice. We aim to quantify the contribution of the two mechanisms that lead to water in outflows, by comparing observations of gas-phase water to methanol (a grain surface product) towards three low-mass protostars in NGC 1333. In doing so, we also quantify the amount of methanol destroyed in outflows. To do this, we make use of James Clerk Maxwell Telescope and Herschel-Heterodyne Instrument for the Far-Infrared data of H2O, CH3OH and CO emission lines and compare them to RADEX non-local thermodynamic equilibrium excitation simulations. We find up to one order of magnitude decrease in the column density ratio of CH3OH over H2O as the velocity increases in the line wings up to ˜15 km s-1. An independent decrease in X(CH3OH) with respect to CO of up to one order of magnitude is also found in these objects. We conclude that gas-phase formation of H2O must be active at high velocities (above 10 km s-1 relative to the source velocity) to re-form the water destroyed during sputtering. In addition, the transition from sputtered water at low velocities to form water at high velocities must be gradual. We place an upper limit of two orders of magnitude on the destruction of methanol by sputtering effects.

  19. Heavy Gas Dispersion Incompressible Flow

    Energy Science and Technology Software Center (ESTSC)

    1992-01-27

    FEM3 is a numerical model developed primarily to simulate heavy gas dispersion in the atmosphere, such as the gravitational spread and vapor dispersion that result from an accidental spill of liquefied natural gas (LNG). FEM3 solves both two and three-dimensional problems and, in addition to the generalized anelastic formulation, includes options to use either the Boussinesq approximation or an isothermal assumption, when appropriate. The FEM3 model is composed of three parts: a preprocessor PREFEM3, themore » main code FEM3, and two postprocessors TESSERA and THPLOTX.« less

  20. Sputtering Yields for Mixtures of Organic Materials Using Argon Gas Cluster Ions.

    PubMed

    Seah, M P; Havelund, R; Shard, A G; Gilmore, I S

    2015-10-22

    The sputtering yield volumes of binary mixtures of Irganox 1010 with either Irganox 1098 or Fmoc-pentafluoro-L-phenylalanine (FMOC) have been measured for 5 keV Ar2000(+) ions incident at 45° to the surface normal. The sputtering yields are determined from the doses to sputter through various compositions of 100 nm thick, intimately mixed, layers. Because of matrix effects, the profiles for secondary ions are distorted, and profile shifts in depth of 15 nm are observed leading to errors above 20% in the deduced sputtering yield. Secondary ions are selected to avoid this. The sputtering yield volumes for the mixtures are shown to be lower than those deduced from a linear interpolation from the pure materials. This is shown to be consistent with a simple model involving the changing energy absorbed for the sputtering of intimate mixtures. Evidence to support this comes from the secondary ion data for pairs of the different molecules. Both binary mixtures behave similarly, but matrix effects are stronger for the Irganox 1010/FMOC system. PMID:26421437

  1. Heavy Gas Dispersion Incompressible Flow

    Energy Science and Technology Software Center (ESTSC)

    1992-02-03

    FEM3 is a numerical model developed primarily to simulate heavy gas dispersion in the atmosphere, such as the gravitational spread and vapor dispersion that result from an accidental spill of liquefied natural gas (LNG). FEM3 solves both two and three-dimensional problems and, in addition to the generalized anelastic formulation, includes options to use either the Boussinesq approximation or an isothermal assumption, when appropriate. The FEM3 model is composed of three parts: a preprocessor PREFEM3, themore » main code FEM3, and two postprocessors TESSERA and THPLOTX. The DEC VAX11 version contains an auxiliary program, POLYREAD, which reads the polyplot file created by FEM3.« less

  2. The digital control of anaesthetic gas flow.

    PubMed

    Boaden, R W; Hutton, P

    1986-04-01

    The theory and construction of a prototype digital gas flow controller are described. Using eight preset needle valves, it has the ability to deliver any flow from 50 to 12750 ml/minute in steps of 50 ml/minute. Under given conditions, the accuracy of this device is very high and its variation in performance with pipeline supply pressures is quantified. The required flow is requested from a BBC 'B' microcomputer which is interfaced with the equipment via a program written in Basic and the 1MHz bus port. The possible uses and potential of a microcomputer-controlled flow regulator in anaesthesia and intensive care are discussed. PMID:2939766

  3. Gas barrier properties of titanium oxynitride films deposited on polyethylene terephthalate substrates by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Lin, M.-C.; Chang, L.-S.; Lin, H. C.

    2008-03-01

    Titanium oxynitride (TiN xO y) films were deposited on polyethylene terephthalate (PET) substrates by means of a reactive radio frequency (RF) magnetron sputtering system in which the power density and substrate bias were the varied parameters. Experimental results show that the deposited TiN xO y films exhibited an amorphous or a columnar structure with fine crystalline dependent on power density. The deposition rate increases significantly in conjunction as the power density increases from 2 W/cm 2 to 7 W/cm 2. The maximum deposition rate occurs, as the substrate bias is -40 V at a certain power densities chosen in this study. The film's roughness slightly decreases with increasing substrate bias. The TiN xO y films deposited at power densities above 4 W/cm 2 show a steady Ti:N:O ratio of about 1:1:0.8. The water vapor and oxygen transmission rates of the TiN xO y films reach values as low as 0.98 g/m 2-day-atm and 0.60 cm 3/m 2-day-atm which are about 6 and 47 times lower than those of the uncoated PET substrate, respectively. These transmission rates are comparable to those of DLC, carbon-based and Al 2O 3 barrier films. Therefore, TiN xO y films are potential candidates to be used as a gas permeation barrier for PET substrate.

  4. The effects of the pressure and the oxygen content of the sputtering gas on the structure and the properties of zinc oxy-nitride thin films deposited by reactive sputtering of zinc

    NASA Astrophysics Data System (ADS)

    Jiang, Nanke; Georgiev, Daniel G.; Jayatissa, Ahalapitiya H.

    2013-02-01

    Zinc nitride and oxy-nitride thin films were prepared by reactive magnetron rf sputtering of zinc in either nitrogen-argon or nitrogen-argon-oxygen ambient. The effects of varying the total sputtering pressure and the oxygen fraction in the total sputtering gas mixture on the microstructure, electrical and optical properties were investigated. With increasing the sputtering pressure, the dominant phase comprising the film material changes from the crystalline zinc nitride phase to crystalline zinc oxide. The characteristic pressure, at which this change in the dominant phase is observed, decreases with the increase of the oxygen fraction in the total sputtering gas mixture. The increase of the oxygen content in the films (from 5 at.% to a maximum of 40 at.%) and the downward shift in the optical absorption edge (from 920 to 400 nm), combined with the x-ray diffraction data, support these observations, indicating the controllable fabrication of an oxy-nitride film material. Correlations between the films’ fabrication conditions, including post-deposition annealing, their structure and composition, and their electrical properties are examined as well.

  5. Flowmeter for gas-entrained solids flow

    DOEpatents

    Porges, Karl G.

    1990-01-01

    An apparatus and method for the measurement of solids feedrate in a gas-entrained solids flow conveyance system. The apparatus and method of the present invention include a vertical duct connecting a source of solids to the gas-entrained flow conveyance system, a control valve positioned in the vertical duct, and a capacitive densitometer positioned along the duct at a location a known distance below the control valved so that the solid feedrate, Q, of the gas entrained flow can be determined by Q=S.rho..phi.V.sub.S where S is the cross sectional area of the duct, .rho. is the density of the solid, .phi. is the solid volume fraction determined by the capacitive densitometer, and v.sub.S is the local solid velocity which can be inferred from the konown distance of the capacitive densitometer below the control valve.

  6. Controlling Gas-Flow Mass Ratios

    NASA Technical Reports Server (NTRS)

    Morris, Brian G.

    1990-01-01

    Proposed system automatically controls proportions of gases flowing in supply lines. Conceived for control of oxidizer-to-fuel ratio in new gaseous-propellant rocket engines. Gas-flow control system measures temperatures and pressures at various points. From data, calculates control voltages for electronic pressure regulators for oxygen and hydrogen. System includes commercially available components. Applicable to control of mass ratios in such gaseous industrial processes as chemical-vapor depostion of semiconductor materials and in automotive engines operating on compressed natural gas.

  7. Optimization of solver for gas flow modeling

    NASA Astrophysics Data System (ADS)

    Savichkin, D.; Dodulad, O.; Kloss, Yu

    2014-05-01

    The main purpose of the work is optimization of the solver for rarefied gas flow modeling based on the Boltzmann equation. Optimization method is based on SIMD extensions for ×86 processors. Computational code is profiled and manually optimized with SSE instructions. Heat flow, shock waves and Knudsen pump are modeled with optimized solver. Dependencies of computational time from mesh sizes and CPU capabilities are provided.

  8. Effect of Sputtering Gas environments on the Properties of Aluminum-doped Zinc Oxide Thin Films for Photovoltaic Application

    SciTech Connect

    Chauhan, Ram Narayan; Kumar, Jitendra; Singh, C.; Anand, R. S.

    2011-10-20

    Aluminum-doped zinc oxide thin films have been deposited on glass substrates by R.F. sputtering using ZnO(98%)-Al{sub 2}O{sub 3}(2%) target in different sputtering gaseous environments, viz., Ar, Ar/O{sub 2} and Ar/N{sub 2}+H{sub 2} at 80 deg. C. These films have been studied with regard to phase, microstructure, optical absorption and sheet resistance for application in photovoltaic devices as transparent conducting electrodes. The properties of the films are shown to strongly depend on the sputtering gas(es). The films exhibit a wurtzite-type hexagonal structure with the (00.2) preferred orientation, the c-axis perpendicular to the substrate. The intensity of 00.2 diffraction peak and the average crystallite size remain almost the same when the films are prepared under pure Ar or Ar/O{sub 2} environment. However the average crystallite size increases while electrical resistance decreases with introduction of nitrogen and hydrogen in comparison to oxygen in argon. Nevertheless, the optimum value of optical transmittance and sheet resistance of the films deposited in pure argon are found to be 85-96% in the wavelength range 400-800 nm and 65 {Omega}/{open_square}, respectively.

  9. Rarefied gas flow through nanoscale tungsten channels.

    PubMed

    Ozhgibesov, M S; Leu, T S; Cheng, C H

    2013-05-01

    The aim of this work is to investigate argon flow behaviors through the channels with three types of boundary conditions. Current work deals with numerical simulations of rarefied gas flow through nano-channels using the Molecular Dynamics method. Taking into account that this method is very time consuming, we implemented all the simulations using CUDA capable graphic cards. We found that the well-known and relatively simple Maxwell model of boundary conditions is able to reproduce gas flow through a tungsten channel with irregularities and roughness, while it results in a significant error in the case of a smooth metal surface. We further found that the flow rate through a relatively short channel correlates nonlinearly with the channel's length. This finding is in contrast with the results available in extant literature. Our results are important for both numerical and theoretical analyses of rarefied gas flow in micro- and nano-systems where the choice of boundary conditions significantly influences flow. PMID:23528809

  10. Ion beam sputter etching

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; Rutledge, Sharon K.

    1986-01-01

    An ion beam etching process which forms extremely high aspect ratio surface microstructures using thin sputter masks is utilized in the fabrication of integrated circuits. A carbon rich sputter mask together with unmasked portions of a substrate is bombarded with inert gas ions while simultaneous carbon deposition occurs. The arrival of the carbon deposit is adjusted to enable the sputter mask to have a near zero or even slightly positive increase in thickness with time while the unmasked portions have a high net sputter etch rate.

  11. Decentralized, continuous-flow gas anchor

    SciTech Connect

    Podio, A.L.; McCoy, J.N.; Woods, M.D.

    1995-12-31

    A novel gas separator design has been developed and successfully tested in several beam pumped wells which were subject to severe gas interference. This paper presents a detailed description of various designs to cover various ranges of fluid production for the most common sizes of completions (4-1/2 to 7 inch casing) and rates from 120 to 825 barrels of liquid per day. The new design is based on two innovations: decentralization of the gas separator in the casing, insures that a minimum amount of gas enters the separator; and the presence of two ports located on the narrow side of the annulus and placed a significant distance apart allow continuous flow of fluids into and out of the separator during both the upstroke and downstroke of the pump. These innovations have resulted in a gas separator efficiency much greater than that of conventional designs.

  12. Sputter-ion plating of coatings for protection of gas-turbine blades against high-temperature oxidation and corrosion

    NASA Technical Reports Server (NTRS)

    Coad, J. P.; Restall, J. E.

    1982-01-01

    Considerable effort is being devoted to the development of overlay coatings for protecting critical components such as turbine blades against high-temperature oxidation, corrosion, and erosion damage in service. The most commercially advanced methods for depositing coatings are electron-beam evaporation and plasma spraying. Sputter-ion plating (SIP) offers a potentially cheaper and simpler alternative method for depositing overlays. Experimental work on SIP of Co-Cr-Al-Y and Ni-Cr-Al-Ti alloy coatings is described. Results are presented of metallographic assessment of these coatings, and of the results obtained from high-velocity testing using a gas-turbine simulator rig.

  13. Effects of Ti addiction in WO 3 thin film ammonia gas sensor prepared by dc reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Hu, Ming; Yong, Cholyun; Feng, Youcai; Lv, Yuqiang; Han, Lei; Liang, Jiran; Wang, Haopeng

    2006-11-01

    WO 3 sensing films (1500 Å) were deposited using dc reactive magnetron sputtering method on alumina substrate on which patterned interdigital Pt electrodes were previously formed. The additive Ti was sputtered with different thickness (100-500 Å) onto WO 3 thin films and then the films as-deposited were annealed at 400°C in air for 3h. The crystal structure and chemical composition of the films were characterized by XRD and XPS analysis. The effect of Ti addition on sensitive properties of WO 3 thin film to the NH 3 gas was then discussed. WO 3 thin films added Ti revealed excellent sensitivity and response characteristics in the presence of low concentration of NH 3 (5-400 ppm) gas in air at 200°C operating temperature. Especially,in case 300 Å thickness of additive Ti, WO 3 thin films have a promotional effect on the response speed to NH 3 and selectivity enhanced with respect to other gases (CO, C IIH 5OH, CH 4). The influence of different substrates, including alumina, silicon and glass, on sensitivity to NH 3 gas has also been investigated.

  14. Continuous-Flow Gas-Phase Bioreactors

    NASA Technical Reports Server (NTRS)

    Wise, Donald L.; Trantolo, Debra J.

    1994-01-01

    Continuous-flow gas-phase bioreactors proposed for biochemical, food-processing, and related industries. Reactor contains one or more selected enzymes dehydrated or otherwise immobilized on solid carrier. Selected reactant gases fed into reactor, wherein chemical reactions catalyzed by enzyme(s) yield product biochemicals. Concept based on discovery that enzymes not necessarily placed in traditional aqueous environments to function as biocatalysts.

  15. 21 CFR 868.2885 - Gas flow transducer.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Gas flow transducer. 868.2885 Section 868.2885...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Monitoring Devices § 868.2885 Gas flow transducer. (a) Identification. A gas flow transducer is a device intended for medical purposes that is used to convert gas...

  16. 21 CFR 868.2885 - Gas flow transducer.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Gas flow transducer. 868.2885 Section 868.2885...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Monitoring Devices § 868.2885 Gas flow transducer. (a) Identification. A gas flow transducer is a device intended for medical purposes that is used to convert gas...

  17. 21 CFR 868.2885 - Gas flow transducer.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Gas flow transducer. 868.2885 Section 868.2885...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Monitoring Devices § 868.2885 Gas flow transducer. (a) Identification. A gas flow transducer is a device intended for medical purposes that is used to convert gas...

  18. 21 CFR 868.2885 - Gas flow transducer.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Gas flow transducer. 868.2885 Section 868.2885...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Monitoring Devices § 868.2885 Gas flow transducer. (a) Identification. A gas flow transducer is a device intended for medical purposes that is used to convert gas...

  19. Gas-solid flow in vertical tubes

    SciTech Connect

    Pita, J.A.; Sundaresan, S. )

    1991-07-01

    This paper reports on a computational study of fully-developed flow of gas-particle suspensions in vertical pipes which was carried out, using the model proposed recently by Sinclair and Jackson, to understand the predicted scale-up characteristics. It was shown that the model can capture the existence of steady-state multiplicity wherein different pressure gradients can be obtained for the same gas and solids fluxes. A pronounced and nonmonotonic variation of the pressure gradient required to achieve desired fluxes of solid and gas with tube diameter was predicted by the model, and this is explained on a physical basis. The computed results were compared with the experimental data. The model manifests an unsatisfactory degree of sensitivity to the inelasticity of the particle-particle collisions and the damping of particle-phase fluctuating motion by the gas.

  20. The influence of sputtering power and O{sub 2}/Ar flow ratio on the performance and stability of Hf-In-Zn-O thin film transistors under illumination

    SciTech Connect

    Kim, Hyun-Suk; Park, Kyung-Bae; Son, Kyoung Seok; Park, Joon Seok; Maeng, Wan-Joo; Kim, Tae Sang; Lee, Kwang-Hee; Kim, Eok Su; Lee, Jiyoul; Suh, Joonki; Seon, Jong-Baek; Ryu, Myung Kwan; Lee, Sang Yoon; Lee, Kimoon; Im, Seongil

    2010-09-06

    The performance and stability of amorphous HfInZnO thin film transistors under visible light illumination were studied. The extent of device degradation upon negative bias stress with the presence of visible light is found to be strongly sensitive to the extent of photoelectric effect in the oxide semiconductor. Highly stable devices were fabricated by optimizing the deposition conditions of HfInZnO films, where the combination of high sputtering power and high O{sub 2}/Ar gas flow ratio was found to result in the highest stability under bias stress experiments.

  1. Bilinear and biquadratic interlayer exchange coupling in sputtered Co/Cu multilayers damaged with residual gas impurities

    NASA Astrophysics Data System (ADS)

    Marrows, C. H.; Hickey, B. J.

    1999-01-01

    The oscillatory indirect exchange coupling exhibited by magnetic/nonmagnetic metal multilayers is known to be highly sensitive to structural defects. We have measured the effects on coupling of residual gas atoms in sputtered Co/Cu multilayers. We have used a simple technique to selectively probe particular parts of the multilayer stack. A large reduction in the giant magnetoresistance has been observed when gas impurity atoms are introduced into the middle of the Cu spacer layers, with a corresponding increase in the remanence of the sample. These changes are shown to be consistent with overwhelmingly strong biquadratic coupling between the Co layers. This leads to the moments in adjacent layers being no longer collinear in zero applied field, which we have confirmed by other measurements. We discuss the applicability of the various theoretical models of biquadratic coupling to our observations.

  2. SSME hot gas manifold flow comparison test

    NASA Technical Reports Server (NTRS)

    Cox, G. B., Jr.; Dill, C. C.

    1988-01-01

    An account is given of the High Pressure Fuel Turbopump (HPFT) component of NASA's Alternate Turbopump Development effort, which is aimed at the proper aerodynamic integration of the current Phase II three-duct SSME Hot Gas Manifold (HGM) and the future 'Phase II-plus' two-duct HGM. Half-scale water flow tests of both HGM geometries were conducted to provide initial design data for the HPFT. The results reveal flowfield results and furnish insight into the performance differences between the two HGM flowpaths. Proper design of the HPFT can potentially secure significant flow improvements in either HGM configuration.

  3. Lateral variation of target poisoning during reactive magnetron sputtering

    SciTech Connect

    Guettler, D.; Groetzschel, R.; Moeller, W.

    2007-06-25

    The reactive gas incorporation into a Ti sputter target has been investigated using laterally resolving ion beam analysis during dc magnetron deposition of TiN in an Ar/N{sub 2} atmosphere. At sufficiently low reactive gas flow, the nitrogen incorporation exhibits a pronounced lateral variation, with a lower areal density in the target racetrack compared to the target center and edge. The findings are reproduced by model calculations. In the racetrack, the balance of reactive gas injection and sputter erosion is shifted toward erosion. The injection of nitrogen is dominated by combined molecular adsorption and recoil implantation versus direct ion implantation.

  4. Lateral variation of target poisoning during reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Güttler, D.; Grötzschel, R.; Möller, W.

    2007-06-01

    The reactive gas incorporation into a Ti sputter target has been investigated using laterally resolving ion beam analysis during dc magnetron deposition of TiN in an Ar /N2 atmosphere. At sufficiently low reactive gas flow, the nitrogen incorporation exhibits a pronounced lateral variation, with a lower areal density in the target racetrack compared to the target center and edge. The findings are reproduced by model calculations. In the racetrack, the balance of reactive gas injection and sputter erosion is shifted toward erosion. The injection of nitrogen is dominated by combined molecular adsorption and recoil implantation versus direct ion implantation.

  5. Effect of gas flow swirling on coating deposition by the cold gas-dynamic spray method

    NASA Astrophysics Data System (ADS)

    Kiselev, S. P.; Kiselev, V. P.; Zaikovskii, V. N.

    2012-03-01

    The effect of gas flow swirling on the process of coating deposition onto a target by the cold gas-dynamic spray method is studied experimentally and numerically. Flow swirling is found to change the gas flow field and to reduce the gas flow rate under typical conditions of cold gas-dynamic spray. In a non-swirled flow, the shape of the deposited spot is similar to a sharp cone. In contrast, the deposited spot in a swirled flow is shaped as a crater without particles at the center of this crater. It is found that this effect is caused by centrifugal forces acting on particles in a swirled gas flow.

  6. A Comparative High-Resolution Electron Microscope Study of Ag Clusters Produced by a Sputter-Gas Aggregation and Ion Cluster Beam Technique

    NASA Astrophysics Data System (ADS)

    Hohl, Georg-Friedrich; Hihara, Takehiko; Sakurai, Masaki; Oishi, Takashi; Wakoh, Kimio; Sumiyama, Kenji; Suzuki, Kenji

    1994-03-01

    Ag clusters were formed by a sputter-gas-aggregation process [H. Haberland et al..: J. Vac. Sci. Technol. A 10 (1992) 3266] and the ionized cluster beam (ICB) [T. Takagi: Ionized-Cluster Beam Deposition and Epitaxy (Noyes, Park Ridge, 1988)] technique. The Ag clusters deposited on collodion-coated microgrids were investigated by high-resolution transmission electron microscopy. The diameter of those clusters, d, ranges from 1 nm up to about 10 nm for specimens produced by the sputter-gas aggregation technique, depending on the sputter condition and the deposition time. Comparable times of the ICB deposition lead to a broader distribution up to d≈20 nm, suggesting the formation of islands with extremely flat shapes. High percentages of crystalline particles obtained by both techniques are either single crystals or multiple twins with clear lattice images.

  7. Gas-Liquid Flow in Pipelines

    SciTech Connect

    Thomas J. Hanratty

    2005-02-25

    A research program was carried out at the University of Illinois in which develops a scientific approach to gas-liquid flows that explains their macroscopic behavior in terms of small scale interactions. For simplicity, fully-developed flows in horizontal and near-horizontal pipes. The difficulty in dealing with these flows is that the phases can assume a variety of configurations. The specific goal was to develop a scientific understanding of transitions from one flow regime to another and a quantitative understanding of how the phases distribute for a give regime. These basic understandings are used to predict macroscopic quantities of interest, such as frictional pressure drop, liquid hold-up, entrainment in annular flow and frequency of slugging in slug flows. A number of scientific issues are addressed. Examples are the rate of atomization of a liquid film, the rate of deposition of drops, the behavior of particles in a turbulent field, the generation and growth of interfacial waves. The use of drag-reducing polymers that change macroscopic behavior by changing small scale interactions was explored.

  8. Inspiratory flow and intrapulmonary gas distribution

    SciTech Connect

    Rehder, K.; Knopp, T.J.; Brusasco, V.; Didier, E.P.

    1981-01-01

    The effect of flow of inspired gas on intrapulmonary gas distribution was examined by analysis of regional pulmonary /sup 133/Xe clearances and of total pulmonary /sup 133/Xe clearance measured at the mouth after equilibration of the lungs with /sup 133/Xe. Five awake healthy volunteers (24 to 40 yr of age) and another 5 healthy, anesthetized-paralyzed volunteers (26 to 28 yr of age) were studied while they were in the right lateral decubitus position. The awake subjects were studied at 3 inspiratory flows (0.4, 0.7, and 1.0 L/s) and the anesthetized-paralyzed subjects at 4 inspiratory flows (0.2, 0.5, 1.1, and 1.6 L/s). Interregional differences in /sup 133/Xe clearances along the vertical axis were significantly less during anesthesia-paralysis and mechanical ventilation than during spontaneous breathing in the awake state. No differences in the regional or total pulmonary /sup 133/Xe clearances were detected at these different flows in either of the two states, i.e., the difference between the awake and anesthetized-paralyzed states persisted.

  9. Permeable Gas Flow Influences Magma Fragmentation Speed.

    NASA Astrophysics Data System (ADS)

    Richard, D.; Scheu, B.; Spieler, O.; Dingwell, D.

    2008-12-01

    Highly viscous magmas undergo fragmentation in order to produce the pyroclastic deposits that we observe, but the mechanisms involved remain unclear. The overpressure required to initiate fragmentation depends on a number of physical parameters, such as the magma's vesicularity, permeability, tensile strength and textural properties. It is clear that these same parameters control also the speed at which a fragmentation front travels through magma when fragmentation occurs. Recent mathematical models of fragmentation processes consider most of these factors, but permeable gas flow has not yet been included in these models. However, it has been shown that permeable gas flow through a porous rock during a sudden decompression event increases the fragmentation threshold. Fragmentation experiments on natural samples from Bezymianny (Russia), Colima (Mexico), Krakatau (Indonesia) and Augustine (USA) volcanoes confirm these results and suggest in addition that high permeable flow rates may increase the speed of fragmentation. Permeability from the investigated samples ranges from as low as 5 x 10-14 to higher than 9 x 10- 12 m2 and open porosity ranges from 16 % to 48 %. Experiments were performed for each sample series at applied pressures up to 35 MPa. Our results indicate that the rate of increase of fragmentation speed is higher when the permeability is above 10-12 m2. We confirm that it is necessary to include the influence of permeable flow on fragmentation dynamics.

  10. 21 CFR 868.2885 - Gas flow transducer.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Gas flow transducer. 868.2885 Section 868.2885 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Monitoring Devices § 868.2885 Gas flow transducer. (a) Identification. A gas flow transducer is a device intended...

  11. Depth resolution at organic interfaces sputtered by argon gas cluster ions: the effect of energy, angle and cluster size.

    PubMed

    Seah, M P; Spencer, S J; Havelund, R; Gilmore, I S; Shard, A G

    2015-10-01

    An analysis is presented of the effect of experimental parameters such as energy, angle and cluster size on the depth resolution in depth profiling organic materials using Ar gas cluster ions. The first results are presented of the incident ion angle dependence of the depth resolution, obtained at the Irganox 1010 to silicon interface, from profiles by X-ray photoelectron spectrometry (XPS). By analysis of all relevant published depth profile data, it is shown that such data, from delta layers in secondary ion mass spectrometry (SIMS), correlate with the XPS data from interfaces if it is assumed that the monolayers of the Irganox 1010 adjacent to the wafer substrate surface have an enhanced sputtering rate. SIMS data confirm this enhancement. These results show that the traditional relation for the depth resolution, FWHM = 2.1Y(1/3) or slightly better, FWHM = P(X)Y(1/3)/n(0.2), where n is the argon gas cluster size, and P(X) is a parameter for each material are valid both at the 45° incidence angle of the argon gas cluster sputtering ions used in most studies and at all angles from 0° to 80°. This implies that, for optimal depth profile resolution, 0° or >75° incidence may be significantly better than the 45° traditionally used, especially for the low energy per atom settings required for the best resolved profiles in organic materials. A detailed analysis, however, shows that the FWHM requires a constant contribution added in quadrature to the above such that there are minimal improvements at 0° or greater than 75°. A critical test at 75° confirms the presence of this constant contribution. PMID:26325511

  12. Synthesis, characterization, and hydrogen gas sensing properties of AuNs-catalyzed ZnO sputtered thin films

    NASA Astrophysics Data System (ADS)

    Drmosh, Q. A.; Yamani, Z. H.

    2016-07-01

    Hydrogen present in concentration up to 4 vol.% forms an explosive mixture with air. Its propensity to escape in the event of leak, could lead to quick build-up and formation of an explosive mixture with air in confined spaces, such as an automobile. This necessitates its detection at very low concentration. Zinc oxide (ZnO) is a well-known wide band gap (∼3.37 eV) semiconducting oxide that has been widely used for gas sensing applications. This work reports on the fabrication, characterization and gas sensing performance of nanogold decorated ZnO thin films made by DC reactive sputtering. The sensor films were fabricated by depositing a very thin layer of gold on the sputtered ZnO thin film. The as deposited Au@ZnO films were converted into highly crystalline ZnO film covered with gold nanostructures (AuNs@ZnO) by mild heat treatment. The structural and morphological as well as the compositional homogeneity of the as-deposited and heat-treated ZnO, Au@ZnO and AuNs@ZnO thin films were ascertained. The gas sensing behavior of the AuNs@ZnO thin films towards hydrogen as a function of temperature at different H2 concentrations was investigated and compared with that of pure and heat-treated ZnO films. The effect of the presence of gold nanoparticles on imparting improvement (in terms of higher response signal, high reproducibility and complete reversibility) was established; the optimal operating temperature was about 400 °C. A plausible mechanism for the observed enhancement in the sensing behavior of AuNs@ZnO films towards H2 is proposed.

  13. Structural analysis of the outermost hair surface using TOF-SIMS with gas cluster ion beam sputtering.

    PubMed

    Lshikawa, Kazutaka; Okamoto, Masayuki; Aoyagi, Satoka

    2016-06-01

    A hair cuticle, which consists of flat overlapping scales that surround the hair fiber, protects inner tissues against external stimuli. The outermost surface of the cuticle is covered with a thin membrane containing proteins and lipids called the epicuticle. In a previous study, the authors conducted a depth profile analysis of a hair cuticle's amino acid composition to characterize its multilayer structure. Time-of-flight secondary ion mass spectrometry with a bismuth primary ion source was used in combination with the C60 sputtering technique for the analysis. It was confirmed that the lipids and cysteine-rich layer exist on the outermost cuticle surface, which is considered to be the epicuticle, though the detailed structure of the epicuticle has not been clarified. In this study, depth profile analysis of the cuticle surface was conducted using the argon gas cluster ion beam (Ar-GCIB) sputtering technique, in order to characterize the structure of the epicuticle. The shallow depth profile of the cuticle surface was investigated using an Ar-GCIB impact energy of 5 keV. Compared to the other amino acid peaks rich in the epicuticle, the decay of 18-methyleicosanic acid (18-MEA) thiolate peak was the fastest. This result suggests that the outermost surface of the hair is rich in 18-MEA. In conclusion, our results indicate that the outermost surfaces of cuticles have a multilayer (lipid and protein layers), which is consistent with the previously proposed structure. PMID:26822506

  14. Gas-flow experiments in the transition region

    SciTech Connect

    Santeler, D.J. )

    1994-07-01

    A special gas-flow facility was designed and constructed for the purpose of accurately measuring UF[sub 6] gas flow through a variety of gas-flow restrictions. The facility was used to measure the gas flow through 15 different orifices and 20 short tubes over a nominal pressure range from 0.002 to 100 Torr. The intent of the experiments was to confirm a new theoretical approach to gas flow through short tubes in the transition range between laminar viscous flow and molecular flow. The theoretical approach previously discussed [Santeler, J. Vac. Sci. Technol. A [bold 4], 338, 348 (1986)] (1986) became a part of the basis for several computer programs used for calculating gas flow in vacuum systems. A number of interesting results in turbulent flow were observed during the experiments and are discussed in the paper. The results of the experiments confirmed the proposed model and were used to evaluate specific parameters of the proposed equations.

  15. Hypervelocity atmospheric flight: Real gas flow fields

    NASA Technical Reports Server (NTRS)

    Howe, John T.

    1990-01-01

    Flight in the atmosphere is examined from the viewpoint of including real gas phenomena in the flow field about a vehicle flying at hypervelocity. That is to say, the flow field is subject not only to compressible phenomena, but is dominated by energetic phenomena. There are several significant features of such a flow field. Spatially, its composition can vary by both chemical and elemental species. The equations which describe the flow field include equations of state and mass, species, elemental, and electric charge continuity; momentum; and energy equations. These are nonlinear, coupled, partial differential equations that were reduced to a relatively compact set of equations of a self-consistent manner (which allows mass addition at the surface at a rate comparable to the free-stream mass flux). The equations and their inputs allow for transport of these quantities relative to the mass-averaged behavior of the flow field. Thus transport of mass by chemical, thermal, pressure, and forced diffusion; transport of momentum by viscosity; and transport of energy by conduction, chemical considerations, viscosity, and radiative transfer are included. The last of these complicate the set of equations by making the energy equation a partial integrodifferential equation. Each phenomenon is considered and represented mathematically by one or more developments. The coefficients which pertain are both thermodynamically and chemically dependent. Solutions of the equations are presented and discussed in considerable detail, with emphasis on severe energetic flow fields. For hypervelocity flight in low-density environments where gaseous reactions proceed at finite rates, chemical nonequilibrium is considered and some illustrations are presented. Finally, flight where the flow field may be out of equilibrium, both chemically and thermodynamically, is presented briefly.

  16. Hypervelocity atmospheric flight: Real gas flow fields

    NASA Technical Reports Server (NTRS)

    Howe, John T.

    1989-01-01

    Flight in the atmosphere is examined from the viewpoint of including real gas phenomena in the flow field about a vehicle flying at hypervelocity. That is to say, the flow field is subject not only to compressible phenomena, but is dominated by energetic phenomena. There are several significant features of such a flow field. Spatially, its composition can vary by both chemical and elemental species. The equations which describe the flow field include equations of state and mass, species, elemental, and electric charge continuity; momentum; and energy equations. These are nonlinear, coupled, partial differential equations that have been reduced to a relatively compact set of equations in a self-consistent manner (which allows mass addition at the surface at a rate comparable to the free-stream mass flux). The equations and their inputs allow for transport of these quantities relative to the mass-average behavior of the flow field. Thus transport of mass by chemical, thermal, pressure, and forced diffusion; transport of momentum by viscosity; and transport of energy by conduction, chemical considerations, viscosity, and radiative transfer are included. The last of these complicate the set of equations by making the energy equations a partial integrodifferential equation. Each phenomenon is considered and represented mathematically by one or more developments. The coefficients which pertain are both thermodynamically and chemically dependent. Solutions of the equations are presented and discussed in considerable detail, with emphasis on severe energetic flow fields. Hypervelocity flight in low-density environments where gaseous reactions proceed at finite rates chemical nonequilibrium is considered, and some illustrations are presented. Finally, flight where the flow field may be out of equilibrium, both chemically and thermodynamically, is presented briefly.

  17. Modeling of heavy-gas effects on airfoil flows

    NASA Technical Reports Server (NTRS)

    Drela, Mark

    1992-01-01

    Thermodynamic models were constructed for a calorically imperfect gas and for a non-ideal gas. These were incorporated into a quasi one dimensional flow solver to develop an understanding of the differences in flow behavior between the new models and the perfect gas model. The models were also incorporated into a two dimensional flow solver to investigate their effects on transonic airfoil flows. Specifically, the calculations simulated airfoil testing in a proposed high Reynolds number heavy gas test facility. The results indicate that the non-idealities caused significant differences in the flow field, but that matching of an appropriate non-dimensional parameter led to flows similar to those in air.

  18. Flows of gas through a protoplanetary gap.

    PubMed

    Casassus, Simon; van der Plas, Gerrit; Sebastian Perez, M; Dent, William R F; Fomalont, Ed; Hagelberg, Janis; Hales, Antonio; Jordán, Andrés; Mawet, Dimitri; Ménard, Francois; Wootten, Al; Wilner, David; Hughes, A Meredith; Schreiber, Matthias R; Girard, Julien H; Ercolano, Barbara; Canovas, Hector; Román, Pablo E; Salinas, Vachail

    2013-01-10

    The formation of gaseous giant planets is thought to occur in the first few million years after stellar birth. Models predict that the process produces a deep gap in the dust component (shallower in the gas). Infrared observations of the disk around the young star HD 142527 (at a distance of about 140 parsecs from Earth) found an inner disk about 10 astronomical units (AU) in radius (1 AU is the Earth-Sun distance), surrounded by a particularly large gap and a disrupted outer disk beyond 140 AU. This disruption is indicative of a perturbing planetary-mass body at about 90 AU. Radio observations indicate that the bulk mass is molecular and lies in the outer disk, whose continuum emission has a horseshoe morphology. The high stellar accretion rate would deplete the inner disk in less than one year, and to sustain the observed accretion matter must therefore flow from the outer disk and cross the gap. In dynamical models, the putative protoplanets channel outer-disk material into gap-crossing bridges that feed stellar accretion through the inner disk. Here we report observations of diffuse CO gas inside the gap, with denser HCO(+) gas along gap-crossing filaments. The estimated flow rate of the gas is in the range of 7 × 10(-9) to 2 × 10(-7) solar masses per year, which is sufficient to maintain accretion onto the star at the present rate. PMID:23283173

  19. Ethylene Trace-gas Techniques for High-speed Flows

    NASA Technical Reports Server (NTRS)

    Davis, David O.; Reichert, Bruce A.

    1994-01-01

    Three applications of the ethylene trace-gas technique to high-speed flows are described: flow-field tracking, air-to-air mixing, and bleed mass-flow measurement. The technique involves injecting a non-reacting gas (ethylene) into the flow field and measuring the concentration distribution in a downstream plane. From the distributions, information about flow development, mixing, and mass-flow rates can be dtermined. The trace-gas apparatus and special considerations for use in high-speed flow are discussed. A description of each application, including uncertainty estimates is followed by a demonstrative example.

  20. Auger electron nanoscale mapping and x-ray photoelectron spectroscopy combined with gas cluster ion beam sputtering to study an organic bulk heterojunction

    SciTech Connect

    Heon Kim, Seong; Heo, Sung; Ihn, Soo-Ghang; Yun, Sungyoung; Hwan Park, Jong; Chung, Yeonji; Lee, Eunha; Park, Gyeongsu; Yun, Dong-Jin

    2014-06-16

    The lateral and vertical distributions of organic p/n bulk heterojunctions for an organic solar cell device are, respectively, investigated using nanometer-scale Auger electron mapping and using X-ray photoelectron spectroscopy (XPS) with Ar gas cluster ion beam (GCIB) sputtering. The concentration of sulfur, present only in the p-type material, is traced to verify the distribution of p-type (donor) and n-type (acceptor) materials in the blended structure. In the vertical direction, a considerable change in atomic sulfur concentration is observed using XPS depth profiling with Ar GCIB sputtering. In addition, Auger electron mapping of sulfur reveals the lateral 2-dimensional distribution of p- and n-type materials. The combination of Auger electron mapping with Ar GCIB sputtering should thereby allow the construction of 3-dimensional distributions of p- and n-type materials in organic photovoltaic cells.

  1. Contamination removal by ion sputtering

    NASA Astrophysics Data System (ADS)

    Shaw, Christopher G.

    1990-11-01

    Experimental investigations are described for ion-beam sputtering and RF-plasma sputtering to determine the effectiveness of the methods for removing contaminants from an optical surface. The effects of ion-beam sputtering are tested with an ion gun and measured by mounting a 5-MHz quartz-crystal microbalance on a sample holder and simulating spacecraft contamination. RF-plasma sputtering involves the application of an alternating electric field to opposing electrodes immersed in a low density gas, and is tested with the same setup. The energy dependence of the sputtering yields is measured to determine whether the different contaminants are removed and whether the mirror surface is affected. Ion-beam sputtering removes all contaminants tested, but also affects the mirror surface at high energies. When the correct DC bias is applied, RF sputtering can remove the contaminants without removing the metal-mirror surface.

  2. Gas flow characteristics of a time modulated APPJ: the effect of gas heating on flow dynamics

    NASA Astrophysics Data System (ADS)

    Zhang, S.; Sobota, A.; van Veldhuizen, E. M.; Bruggeman, P. J.

    2015-01-01

    This work investigates the flow dynamics of a radio-frequency (RF) non-equilibrium argon atmospheric pressure plasma jet. The RF power is at a frequency of 50 Hz or 20 kHz. Combined flow pattern visualizations (obtained by shadowgraphy) and gas temperature distributions (obtained by Rayleigh scattering) are used to study the formation of transient vortex structures in initial flow field shortly after the plasma is switched on and off in the case of 50 Hz modulation. The transient vortex structures correlate well with observed temperature differences. Experimental results of the fast modulated (20 kHz) plasma jet that does not induce changes of the gas temperature are also presented. The latter result suggests that momentum transfer by ions does not have dominant effect on the flow pattern close to the tube. It is argued that the increased gas temperature and corresponding gas velocity increase at the tube exit due to the plasma heating increases the admixing of surrounding air and reduces the effective potential core length. With increasing plasma power a reduction of the effective potential core length is observed with a minimum length for 5.6 W after which the length extends again. Possible mechanisms related to viscosity effects and ionic momentum transfer are discussed.

  3. Influence of nitrogen flow rate on microstructural and nanomechanical properties of Zr-N thin films prepared by pulsed DC magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Singh, Akash; Kuppusami, P.; Khan, Shabana; Sudha, C.; Thirumurugesan, R.; Ramaseshan, R.; Divakar, R.; Mohandas, E.; Dash, S.

    2013-09-01

    Zr-N thin films were deposited on Si (1 0 0) substrate by reactive sputtering using a pulsed DC magnetron sputtering technique. It was found that films deposited at 773 K and 1 sccm of nitrogen flow rate show a single phase with face centred cubic-ZrN. Raman analysis also confirmed the formation of ZrN phase in the films. The films deposited at nitrogen flow rate greater than 1 sccm show ZrN along with orthorhombic-Zr3N4. The chemical bonding characteristics of the films were analyzed by X-ray photoelectron spectroscopy. High resolution transmission electron microscopy also gave evidence for fcc-ZrN and o-Zr3N4 phase and revealed equiaxed grains in these films. In addition, hardness and Young's modulus of the films measured as a function of nitrogen flow rate is discussed qualitatively in relation to resistance to plastic deformation offered by these films.

  4. Mechanical properties of Ta-Al-N thin films deposited by cylindrical DC magnetron sputtering: Influence of N2% in the gas mixture

    NASA Astrophysics Data System (ADS)

    Darabi, Elham; Moghaddasi, Naghmeh; Reza Hantehzadeh, Mohammad

    2016-06-01

    Ta-Al-N thin films were deposited by cylindrical DC magnetron sputtering on a stainless steel substrate under varying nitrogen flow ratios ( N2 with respect to N2 + Ar in the range of 1.5%-9%. The effect of the N2 content in the reactive gas mixture on crystalline structure, surface morphology, and mechanical properties of Ta-Al-N thin films was investigated. The amount of Al and Ta in deposited films was obtained by energy dispersive X-ray spectroscopy (EDX) analysis and films thickness was measured by surface step profilometer. X-ray diffraction analysis (XRD) revealed that the crystalline structure of the Ta-Al-N polycrystalline thin film is a mixture of TaAl, TaN, and AlN crystalline phases. Surface morphology, roughness, and grain size were investigated by atomic force microscopy (AFM). The nano hardness of Ta-Al-N thin films, measured by the nanoindentation method, was about 9GPa maximum for samples prepared under 3% N2 , and the friction coefficient, obtained by nanoscratch analysis, was approximately 0.2 for all Ta-Al-N thin films. Other results were found to be affected considerably by increasing the N2 amount.

  5. Laboratory measurement and interpretation of nonlinear gas flow in shale

    NASA Astrophysics Data System (ADS)

    Kang, Yili; Chen, Mingjun; Li, Xiangchen; You, Lijun; Yang, Bin

    2015-11-01

    Gas flow mechanisms in shale are urgent to clarify due to the complicated pore structure and low permeability. Core flow experiments were conducted under reservoir net confining stress with samples from the Longmaxi Shale to investigate the characteristics of nonlinear gas flow. Meanwhile, microstructure analyses and gas adsorption experiments are implemented. Experimental results indicate that non-Darcy flow in shale is remarkable and it has a close relationship with pore pressure. It is found that type of gas has a significant influence on permeability measurement and methane is chosen in this work to study the shale gas flow. Gas slippage effect and minimum threshold pressure gradient weaken with the increasing backpressure. It is demonstrated that gas flow regime would be either slip flow or transition flow with certain pore pressure and permeability. Experimental data computations and microstructure analyses confirm that hydraulic radius of flow tubes in shale are mostly less than 100 nm, indicating that there is no micron scale pore or throat which mainly contributes to flow. The results are significant for the study of gas flow in shale, and are beneficial for laboratory investigation of shale permeability.

  6. Modeling metallic nanoparticle synthesis in a magnetron-based nanocluster source by gas condensation of a sputtered vapor

    NASA Astrophysics Data System (ADS)

    Quesnel, E.; Pauliac-Vaujour, E.; Muffato, V.

    2010-03-01

    Copper nanoparticles (NPs) were synthesized by inert-gas condensation of a sputtered metallic vapor using a dedicated commercial reactor. By controlling the time of residence of NPs in the carrier gas phase via the tuning of the collision path length, Cu NPs were produced. They exhibit various and well controlled diameters (3-10 nm) and a relatively narrow size dispersion. On the basis of these experimental results, a detailed modeling of NP nucleation and growth based on the classical nucleation theory was developed. It takes into account the peculiar geometry and thermal profile of the NP reactor. The simulated curves, calculated by a MATLAB® program developed for that purpose, exhibit a good qualitative agreement with experiment. Moreover, they highlight the role of process parameters and the strong influence of the reactor temperature profile on the NP size distribution. In the future, such calculations could be used for the optimization of the NP source design in order to increase its efficiency and reproducibility.

  7. Vehicle Exhaust Gas Clearance by Low Temperature Plasma-Driven Nano-Titanium Dioxide Film Prepared by Radiofrequency Magnetron Sputtering

    PubMed Central

    Yu, Shuang; Liang, Yongdong; Sun, Shujun; Zhang, Kai; Zhang, Jue; Fang, Jing

    2013-01-01

    A novel plasma-driven catalysis (PDC) reactor with special structure was proposed to remove vehicle exhaust gas. The PDC reactor which consisted of three quartz tubes and two copper electrodes was a coaxial dielectric barrier discharge (DBD) reactor. The inner and outer electrodes firmly surrounded the outer surface of the corresponding dielectric barrier layer in a spiral way, respectively. Nano-titanium dioxide (TiO2) film prepared by radiofrequency (RF) magnetron sputtering was coated on the outer wall of the middle quartz tube, separating the catalyst from the high voltage electrode. The spiral electrodes were designed to avoid overheating of microdischarges inside the PDC reactor. Continuous operation tests indicated that stable performance without deterioration of catalytic activity could last for more than 25 h. To verify the effectiveness of the PDC reactor, a non-thermal plasma(NTP) reactor was employed, which has the same structure as the PDC reactor but without the catalyst. The real vehicle exhaust gas was introduced into the PDC reactor and NTP reactor, respectively. After the treatment, compared with the result from NTP, the concentration of HC in the vehicle exhaust gas treated by PDC reactor reduced far more obviously while that of NO decreased only a little. Moreover, this result was explained through optical emission spectrum. The O emission lines can be observed between 870 nm and 960 nm for wavelength in PDC reactor. Together with previous studies, it could be hypothesized that O derived from catalytically O3 destruction by catalyst might make a significant contribution to the much higher HC removal efficiency by PDC reactor. A series of complex chemical reactions caused by the multi-components mixture in real vehicle exhaust reduced NO removal efficiency. A controllable system with a real-time feedback module for the PDC reactor was proposed to further improve the ability of removing real vehicle exhaust gas. PMID:23560062

  8. Vehicle exhaust gas clearance by low temperature plasma-driven nano-titanium dioxide film prepared by radiofrequency magnetron sputtering.

    PubMed

    Yu, Shuang; Liang, Yongdong; Sun, Shujun; Zhang, Kai; Zhang, Jue; Fang, Jing

    2013-01-01

    A novel plasma-driven catalysis (PDC) reactor with special structure was proposed to remove vehicle exhaust gas. The PDC reactor which consisted of three quartz tubes and two copper electrodes was a coaxial dielectric barrier discharge (DBD) reactor. The inner and outer electrodes firmly surrounded the outer surface of the corresponding dielectric barrier layer in a spiral way, respectively. Nano-titanium dioxide (TiO2) film prepared by radiofrequency (RF) magnetron sputtering was coated on the outer wall of the middle quartz tube, separating the catalyst from the high voltage electrode. The spiral electrodes were designed to avoid overheating of microdischarges inside the PDC reactor. Continuous operation tests indicated that stable performance without deterioration of catalytic activity could last for more than 25 h. To verify the effectiveness of the PDC reactor, a non-thermal plasma(NTP) reactor was employed, which has the same structure as the PDC reactor but without the catalyst. The real vehicle exhaust gas was introduced into the PDC reactor and NTP reactor, respectively. After the treatment, compared with the result from NTP, the concentration of HC in the vehicle exhaust gas treated by PDC reactor reduced far more obviously while that of NO decreased only a little. Moreover, this result was explained through optical emission spectrum. The O emission lines can be observed between 870 nm and 960 nm for wavelength in PDC reactor. Together with previous studies, it could be hypothesized that O derived from catalytically O3 destruction by catalyst might make a significant contribution to the much higher HC removal efficiency by PDC reactor. A series of complex chemical reactions caused by the multi-components mixture in real vehicle exhaust reduced NO removal efficiency. A controllable system with a real-time feedback module for the PDC reactor was proposed to further improve the ability of removing real vehicle exhaust gas. PMID:23560062

  9. Reducing the impurity incorporation from residual gas by ion bombardment during high vacuum magnetron sputtering

    SciTech Connect

    Rosen, Johanna; Widenkvist, Erika; Larsson, Karin; Kreissig, Ulrich; Mraz, Stanislav; Martinez, Carlos; Music, Denis; Schneider, J. M.

    2006-05-08

    The influence of ion energy on the hydrogen incorporation has been investigated for alumina thin films, deposited by reactive magnetron sputtering in an Ar/O{sub 2}/H{sub 2}O environment. Ar{sup +} with an average kinetic energy of {approx}5 eV was determined to be the dominating species in the plasma. The films were analyzed with x-ray diffraction, x-ray photoelectron spectroscopy, and elastic recoil detection analysis, demonstrating evidence for amorphous films with stoichiometric O/Al ratio. As the substrate bias potential was increased from -15 V (floating potential) to -100 V, the hydrogen content decreased by {approx}70%, from 9.1 to 2.8 at. %. Based on ab initio calculations, these results may be understood by thermodynamic principles, where a supply of energy enables surface diffusion, H{sub 2} formation, and desorption [Rosen et al., J. Phys.: Condens. Matter 17, L137 (2005)]. These findings are of importance for the understanding of the correlation between ion energy and film composition and also show a pathway to reduce impurity incorporation during film growth in a high vacuum ambient.

  10. Co-sputtered metal and polymer nanocomposite films and their electrical responses for gas sensing application

    NASA Astrophysics Data System (ADS)

    Rujisamphan, Nopporn; Murray, Roy E.; Deng, Fei; Supasai, Thidarat

    2016-04-01

    Titanium and polytetrafluoroethylene (Ti-PTFE) nanocomposite thin films were successfully fabricated on glass substrates using a combination of dc and rf magnetron sputtering. When the Ti-PTFE composites were prepared at below the percolation threshold i.e. 27% metal volume filling (F), Ti clusters with the average sizes of 7 ± 2 nm were found. As the Ti content was increased above the percolation threshold (F = 62%), the connecting regions of Ti were formed within the polymer matrix and the electrical property changed rapidly from insulator-like to metal-like properties. The Ti-PTFE composites prepared near the percolation threshold showed the electrical response to different volatile organic compounds (VOCs). The sensitivity significantly depended upon the VOCs concentrations. These composites devices showed the presence of distinct chemical bonds of Csbnd C, Csbnd CF, Csbnd F and CF2 and TiF in TiO2 on the surface as investigated by X-ray photoelectron spectroscopy (XPS) while the surface morphology, characterized by atomic force microscopy (AFM) presented the root mean square (RMS) surface roughness of 13.3 nm. Cross-section transmission electron microscopy (TEM) images of the device revealed Ti clusters dispersed in PTFE matrix with particle sizes varied between 10 nm and 30 nm.

  11. Computer program for natural gas flow through nozzles

    NASA Technical Reports Server (NTRS)

    Johnson, R. C.

    1972-01-01

    Subroutines, FORTRAN 4 type, were developed for calculating isentropic natural gas mass flow rate through nozzle. Thermodynamic functions covering compressibility, entropy, enthalpy, and specific heat are included.

  12. A Gas-Kinetic Scheme for Reactive Flows

    NASA Technical Reports Server (NTRS)

    Lian,Youg-Sheng; Xu, Kun

    1998-01-01

    In this paper, the gas-kinetic BGK scheme for the compressible flow equations is extended to chemical reactive flow. The mass fraction of the unburnt gas is implemented into the gas kinetic equation by assigning a new internal degree of freedom to the particle distribution function. The new variable can be also used to describe fluid trajectory for the nonreactive flows. Due to the gas-kinetic BGK model, the current scheme basically solves the Navier-Stokes chemical reactive flow equations. Numerical tests validate the accuracy and robustness of the current kinetic method.

  13. Gas flow means for improving efficiency of exhaust hoods

    DOEpatents

    Gadgil, A.J.

    1994-01-11

    Apparatus is described for inhibiting the flow of contaminants in an exhaust enclosure toward an individual located adjacent an opening into the exhaust enclosure by providing a gas flow toward a source of contaminants from a position in front of an individual to urge said contaminants away from the individual toward a gas exit port. The apparatus comprises a gas manifold which may be worn by a person as a vest. The manifold has a series of gas outlets on a front face thereof facing away from the individual and toward the contaminants to thereby provide a flow of gas from the front of the individual toward the contaminants. 15 figures.

  14. Gas flow means for improving efficiency of exhaust hoods

    DOEpatents

    Gadgil, Ashok J.

    1994-01-01

    Apparatus for inhibiting the flow of contaminants in an exhaust enclosure toward an individual located adjacent an opening into the exhaust enclosure by providing a gas flow toward a source of contaminants from a position in front of an individual to urge said contaminants away from the individual toward a gas exit port. The apparatus comprises a gas mani-fold which may be worn by a person as a vest. The manifold has a series of gas outlets on a front face thereof facing away from the individual and toward the contaminants to thereby provide a flow of gas from the front of the individual toward the contaminants.

  15. Simulation of gas particle flow in a HVOF torch

    SciTech Connect

    Chang, C.H.; Moore, R.L.

    1995-12-31

    A transient two-dimensional numerical simulation of Inconel spraying in an HVOF torch barrel has been performed. The gas flow is treated as a continuum multicomponent chemically reacting flow, while particles are modeled using a stochastic particle spray model, fully coupled to the gas flow. The calculated results agree well with experimental data, and show important statistical aspects of particle flow in the torch.

  16. Compressible flow computer program for gas film seals

    NASA Technical Reports Server (NTRS)

    Zuk, J.; Smith, P. J.

    1975-01-01

    Computer program, AREAX, calculates properties of compressible fluid flow with friction and area change. Program carries out quasi-one-dimensional flow analysis which is valid for laminar and turbulent flows under both subsonic and choked flow conditions. Program was written to be applied to gas film seals.

  17. Characterization of helium/argon working gas systems in a radiofrequency glow discharge atomic emission source. Part I: Optical emission, sputtering and electrical characteristics

    NASA Astrophysics Data System (ADS)

    Christopher, Steven J.; Hartenstein, Matthew L.; Marcus, R. Kenneth; Belkin, Mikhail; Caruso, Joseph A.

    1998-08-01

    Studies are performed to determine the influence of discharge gas composition (helium/argon working gas mixtures) on the analyte emission signal intensities, sputtering rates, and DC-bias characteristics of an analytical radiofrequency glow discharge atomic emission spectroscopy (RF-GD-AES) source. As the partial pressure of He is increased from 0 to 15 torr, increased emission intensity is observed for a range of bulk and trace elements in NIST 1250 SRM (low alloy steel), regardless of the base pressure of Ar in the source (5 and 9 torr). In contrast to increases in analyte emission intensity of up to 300%, counterindicative decreases in the sputtering rates on the order of about 30-50% are observed. The magnitude of these effects depends on both the partial pressure of helium introduced to the source and the total pressure of the He and Ar gases. Use of relative emission yield (REY) to normalize changes in emission intensity to sputtering rates indicates that excitation efficiencies increase under these conditions. Increases in average electron energy and temperature appear to control this response. Decreases in both analyte emission intensities and sputter rates occur with increasing He partial pressure when the total pressure in the cell remains fixed (11 torr in these studies). Emission yields for the fixed pressure, mixed gas plasmas decrease as the partial pressure of He (He/Ar ratio) in the RF-GD source increases. In this case, decreases in electron number densities appear to dictate the lower REYs. Measurement of DC-bias values at the sample surface provide understanding with respect to the observed changes in sputtering rates as well as suggest the origins of changes in plasma electron energetics. Use of a diamond stylus profilometer provides both the quantitative sputter rate information as well as qualitative insights into the use of mixed gas plasmas for enhanced depth profiling capabilities. The analyte emission characteristics of these mixed gas

  18. Compatibility of gas and flow sensor technology fabrication

    NASA Astrophysics Data System (ADS)

    Sabate, Neus; Gracia, Isabel; Cane, Carles; Puigcorbe, Jordi; Cerda, Judith; Morante, Joan Ramon; Berganzo, Javier

    2003-04-01

    The requirements of flow measurement and control in the home-appliances field lead to the need of a measurement system able to monitor the flow and the quality of gas. The integration of a set of sensors with different functionalities on a single chip arises as an advantageous solution. In this paper, the description of the structures and technologies required for the gas, flow and temperature sensor devices is presented prior to the complete description of the process flow for the full on-chip compatibilization. In this sense, semiconductor gas sensors and thermal flow sensors have arisen as the best candidates to address the compatibilization.

  19. Device accurately measures and records low gas-flow rates

    NASA Technical Reports Server (NTRS)

    Branum, L. W.

    1966-01-01

    Free-floating piston in a vertical column accurately measures and records low gas-flow rates. The system may be calibrated, using an adjustable flow-rate gas supply, a low pressure gage, and a sequence recorder. From the calibration rates, a nomograph may be made for easy reduction. Temperature correction may be added for further accuracy.

  20. Oxford Miniature Vaporiser output with reversed gas flows.

    PubMed

    Donovan, A; Perndt, H

    2007-06-01

    This study was undertaken to investigate and calibrate the isoflurane output of an Oxford Miniature Vaporiser (OMV) draw-over vaporiser with reversed gas flows. Plenum or Boyles type machines have gas flowing left to right through the apparatus. Draw over anaesthesia systems, in contrast, traditionally have the carrier gas, air plus oxygen, flowing right to left through the vaporiser. There are a number of variations in the external design of the OMV vaporiser: 1) a back bar mounted draw-over vaporiser with 23-mm taper and left to right gas flow, 2) the Tri-Service with 22-mm taper and left to right gas flow, and 3) the traditional draw-over OMV with right to left gas flow with a variety of tapers. Non-uniformity leads to a variety of possible connections. The predictable output of the OMV vaporiser assumes the correct direction of gas flows for the device. There are many second hand right to left OMV vaporisers for sale to developing countries where the nuances of vaporiser orientation add unnecessarily to the desired simplicity of anaesthesia. A simple calibration scale for reversed gas flows through the OMV vaporiser would be useful. PMID:17506742

  1. Gas/liquid flow measurement using coriolis-based flow meters

    SciTech Connect

    Liu, K.T.; Nguyen, T.V.

    1991-07-09

    This patent describes a method of determining total mass flow rate and phase distribution of individual components in a flowing gas/liquid stream. It comprises flowing at least a first gas/liquid stream through a Coriolis-based flow meter, the first gas/liquid stream having a first known total mass flow rate and component phase distribution; obtaining a first apparent total mass flow rate output and a first apparent density output from the Coriolis- based mass flow meter; correlating the first known total mass flow rate and phase distribution with the first apparent mass flow rate output and the first apparent density output obtained from the Coriolis-based mass flow meter to determine a set of correlation equations; flowing a second gas/liquid stream through the Coriolis-based mass flow meter; obtaining a second apparent mass flow rate output and a second apparent density output from the Coriolis-based mass flow meter; calculating a total mass flow rate and a component phase distribution of the second gas/liquid stream based on the correlation equations and the second apparent mass flow rate output and the second apparent density output.

  2. Equations for Adiabatic but Rotational Steady Gas Flows without Friction

    NASA Technical Reports Server (NTRS)

    Schaefer, Manfred

    1947-01-01

    This paper makes the following assumptions: 1) The flowing gases are assumed to have uniform energy distribution. ("Isoenergetic gas flows," that is valid with the same constants for the the energy equation entire flow.) This is correct, for example, for gas flows issuing from a region of constant pressure, density, temperature, end velocity. This property is not destroyed by compression shocks because of the universal validity of the energy law. 2) The gas behaves adiabatically, not during the compression shock itself but both before and after the shock. However, the adiabatic equation (p/rho(sup kappa) = C) is not valid for the entire gas flow with the same constant C but rather with an appropriate individual constant for each portion of the gas. For steady flows, this means that the constant C of the adiabatic equation is a function of the stream function. Consequently, a gas that has been flowing "isentropically",that is, with the same constant C of the adiabatic equation throughout (for example, in origination from a region of constant density, temperature, and velocity) no longer remains isentropic after a compression shock if the compression shock is not extremely simple (wedge shaped in a two-dimensional flow or cone shaped in a rotationally symmetrical flow). The solution of nonisentropic flows is therefore an urgent necessity.

  3. Real-Time Measurement of Vehicle Exhaust Gas Flow

    SciTech Connect

    Hardy, J.E.; Hylton, J.O.; Joy, R.D.; McKnight, T.E.

    1999-06-28

    A flow measurement system was developed to measure, in real-time, the exhaust gas flow from vehicies. This new system was based on the vortex shedding principle using ultrasonic detectors for sensing the shed vortices. The flow meter was designed to measure flow over a range of 1 to 366 Ips with an inaccuracy of ~1o/0 of reading. Additionally, the meter was engineered to cause minimal pressure drop (less than 125mm of water), to function in a high temperature environment (up to 650oC) with thermal transients of 15 oC/s, and to have a response time of 0.1 seconds for a 10% to 90!40 step change. The flow meter was also configured to measure hi-directional flow. Several flow meter prototypes were fabricated, tested, and calibrated in air, simulated exhaust gas, and actual exhaust gas. Testing included gas temperatures to 600oC, step response experiments, and flow rates from O to 360 lps in air and exhaust gas. Two prototypes have been tested extensively at NIST and two additional meters have been installed in exhaust gas flow lines for over one year. This new flow meter design has shown to be accurate, durabIe, fast responding, and to have a wide rangeabi~ity.

  4. Thermoacoustic compression based on alternating to direct gas flow conversion

    NASA Astrophysics Data System (ADS)

    Sun, D. M.; Wang, K.; Xu, Y.; Shen, Q.; Zhang, X. J.; Qiu, L. M.

    2012-05-01

    We present a remarkable thermoacoustically driven compression effect based on the conversion of gas flow from an alternating state to a direct state. The alternating gas flow is generated by the thermoacoustic effect in thermoacoustic engines, whereas direct gas flow is achieved by means of the flow rectification effect of check valves. A demonstrative thermoacoustic compressor consisting of two standing-wave thermoacoustic engines, two reservoirs, and three check valves is constructed for experimental investigation. With nitrogen as a working gas and an initial pressure of 2.4 MPa in all components, a usable pressure difference of 0.4 MPa is achieved, with the average gas pumping rate reaching 2.85 Nm3/h during the first 3 s of the compression process. The simple mechanical structure and thermally driven nature of the compressor show potential in gas compression, power generation, and refrigeration applications.

  5. Magnetron-Sputtered Amorphous Metallic Coatings

    NASA Technical Reports Server (NTRS)

    Thakoor, A. P.; Mehra, M.; Khanna, S. K.

    1985-01-01

    Amorphous coatings of refractory metal/metalloid-based alloys deposited by magnetron sputtering provide extraordinary hardness and wear resistance. Sputtering target fabricated by thoroughly mixing powders of tungsten, rhenium, and boron in stated proportions and pressing at 1,200 degrees C and 3,000 lb/in. to second power (21 MPa). Substrate lightly etched by sputtering before deposition, then maintained at bias of - 500 V during initial stages of film growth while target material sputtered onto it. Argon gas at pressure used as carrier gas for sputter deposition. Coatings dense, pinhole-free, extremely smooth, and significantly resistant to chemical corrosion in acidic and neutral aqueous environments.

  6. Effects of N2/O2 flow rate on the surface properties and biocompatibility of nano-structured TiOxNy thin films prepared by high vacuum magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Saleem, Sehrish; Ahmad, R.; Ikhlaq, Uzma; Ayub, R.; Wei, Hong Jin; Rui Zhen, Xu; Peng, Hui Li; Abbas, Khizra; Chu, Paul K.

    2015-07-01

    NiTi shape memory alloys (SMA) have many biomedical applications due to their excellent mechanical and biocompatible properties. However, nickel in the alloy may cause allergic and toxic reactions, which limit some applications. In this work, titanium oxynitride films were deposited on NiTi samples by high vacuum magnetron sputtering for various nitrogen and oxygen gas flow rates. The x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) results reveal the presence of different phases in the titanium oxynitride thin films. Energy dispersive spectroscopy (EDS) elemental mapping of samples after immersion in simulated body fluids (SBF) shows that Ni is depleted from the surface and cell cultures corroborate the enhanced biocompatibility in vitro. Project supported by the Higher Education Commission, Hong Kong Research Grants Council (RGC) General Research Funds (GRF), China (Grant No. 112212) and the City University of Hong Kong Applied Research Grant (ARG), China (Grant No. 9667066).

  7. Breakup of Droplets in an Accelerating Gas Flow

    NASA Technical Reports Server (NTRS)

    Dickerson, R. A.; Coultas, T. A.

    1966-01-01

    A study of droplet breakup phenomena by an accelerating gas flow is described. The phenomena are similar to what propellant droplets experience when exposed to accelerating combustion gas flow in a rocket engine combustion zone. Groups of several dozen droplets in the 100-10 750-micron-diameter range were injected into a flowing inert gas in a transparent rectangular nozzle. Motion photography of the behavior of the droplets at various locations in the accelerating gas flow has supplied quantitative and qualitative data on the breakup phenomena which occur under conditions similar to those found in large rocket engine combustors. A blowgun injection device, used to inject very small amounts of liquid at velocities of several hundred feet per second into a moving gas stream, is described. The injection device was used to inject small amounts of liquid RP-1 and water into the gas stream at a velocity essentially equal to the gas velocity where the group of droplets was allowed to stabilize its formation in a constant area section before entering the convergent section of the transparent nozzle. Favorable comparison with the work of previous investigators who have used nonaccelerating gas flow is found with the data obtained from this study with accelerating gas flow. The criterion for the conditions of minimum severity required to produce shear-type droplet breakup in an accelerating gas flow is found to agree well with the criterion previously established at Rocketdyne for breakup in nonaccelerating flow. An extension of the theory of capillary surface wave effects during droplet breakup is also presented. Capillary surface waves propagating in the surface of the droplet, according to classical hydrodynamical laws, are considered. The waves propagate tangentially over the surface of the droplet from the forward stagnation point to the major diameter. Consideration of the effects of relative gas velocity on the amplitude growth of these waves allows conclusions to be

  8. Sputter etching of hemispherical bearings

    NASA Technical Reports Server (NTRS)

    Schiesser, R. J.

    1972-01-01

    Technique was developed for fabricating three dimensional pumping grooves on gas bearings by sputter etching. Method eliminates problems such as groove nonuniformity, profile, and finish, which are associated with normal grooving methods.

  9. Gulf Coast, Arkoma gas increasing flow through Lebanon hub

    SciTech Connect

    True, W.R.

    1992-03-09

    Construction projects will hit stride this year for moving more U.S.-produced gas into the Northeast. Combined with projects recently completed, under way, or planned for Canadian gas at least 3 bcfd more gas will flow into New York, New Jersey, and the New England states within the next 3 years. This article looks at two major clusters of projectors to move U.S. Gulf Coast and Arkoma gas through the expanding Lebanon, Ohio, hub.

  10. Velocity Inversion In Cylindrical Couette Gas Flows

    NASA Astrophysics Data System (ADS)

    Dongari, Nishanth; Barber, Robert W.; Emerson, David R.; Zhang, Yonghao; Reese, Jason M.

    2012-05-01

    We investigate a power-law probability distribution function to describe the mean free path of rarefied gas molecules in non-planar geometries. A new curvature-dependent model is derived by taking into account the boundary-limiting effects on the molecular mean free path for surfaces with both convex and concave curvatures. In comparison to a planar wall, we find that the mean free path for a convex surface is higher at the wall and exhibits a sharper gradient within the Knudsen layer. In contrast, a concave wall exhibits a lower mean free path near the surface and the gradients in the Knudsen layer are shallower. The Navier-Stokes constitutive relations and velocity-slip boundary conditions are modified based on a power-law scaling to describe the mean free path, in accordance with the kinetic theory of gases, i.e. transport properties can be described in terms of the mean free path. Velocity profiles for isothermal cylindrical Couette flow are obtained using the power-law model. We demonstrate that our model is more accurate than the classical slip solution, especially in the transition regime, and we are able to capture important non-linear trends associated with the non-equilibrium physics of the Knudsen layer. In addition, we establish a new criterion for the critical accommodation coefficient that leads to the non-intuitive phenomena of velocity-inversion. Our results are compared with conventional hydrodynamic models and direct simulation Monte Carlo data. The power-law model predicts that the critical accommodation coefficient is significantly lower than that calculated using the classical slip solution and is in good agreement with available DSMC data. Our proposed constitutive scaling for non-planar surfaces is based on simple physical arguments and can be readily implemented in conventional fluid dynamics codes for arbitrary geometric configurations.

  11. Gas flow driven by thermal creep in dusty plasma

    SciTech Connect

    Flanagan, T. M.; Goree, J.

    2009-10-15

    Thermal creep flow (TCF) is a flow of gas driven by a temperature gradient along a solid boundary. Here, TCF is demonstrated experimentally in a dusty plasma. Stripes on a glass box are heated by laser beam absorption, leading to both TCF and a thermophoretic force. The design of the experiment allows isolating the effect of TCF. A stirring motion of the dust particle suspension is observed. By eliminating all other explanations for this motion, we conclude that TCF at the boundary couples by drag to the bulk gas, causing the bulk gas to flow, thereby stirring the suspension of dust particles. This result provides an experimental verification, for the field of fluid mechanics, that TCF in the slip-flow regime causes steady-state gas flow in a confined volume.

  12. Influence of working gas pressure on structure and properties of WO3 films reactively deposited by rf magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Takahashi, T.; Tanabe, J.; Yamada, N.; Nakabayashi, H.

    2003-07-01

    Tungsten trioxide (WO3) films with thickness of 0.9-6.7 μm have been deposited on glass-slide substrates, using rf magnetron sputtering in an atmosphere of mixture 80% Ar and 20% O2. The as-deposited films had a dark metallic color, like the W target, at a working gas pressure PW of 1 mTorr. Yellow films resulted at a PW of 3 mTorr. With a further increase of PW, the film color changed to pale yellow. From the x-ray diffraction patterns, the as-deposited films were polycrystalline crystallizing in the monoclinic crystal structure with high c-axis orientation perpendicular to the film plane. The optical transmittance of the films deposited at a PW of 1 mTorr is nearly zero. However, the transmittance of the films deposited at other PW are larger than 70% in the wavelength, λ, ranging from 500 to 900 nm. With decreasing λ to 400 nm, the transmittance decreases steeply to zero. The λ at this absorption edge is longer than that in TiO2 and comes in the visible region. The surface morphology of the films depends on PW. This different morphology may be attributed to the effect of the substrate heating by plasma emission because of the high plasma density at higher PW. The morphology of the films may also depend on the crystallinity of the WO3 films. As PW increased, the surfaces of the films became rougher but the grain sizes of the films did not always become larger. The WO3 films deposited in this study may be used for the underlayer of TiO2 photocatalyst.

  13. New technology directly measures mass flow of gas

    SciTech Connect

    Hahn, D.T.

    1995-12-31

    According to recent industry surveys and solicitations by organizations such as the Gas Research Institute and Small Business Innovation Research, a need exists for a gas flowmeter with {plus_minus}0.5% or better accuracy, that does not need to be calibrated for specific gas properties, and requires no periodic maintenance. Over the past 18 years, Coriolis mass flowmeters have provided these features for liquid flow applications, and have won a significant share of the liquid flow measurement market. Coriolis meters continue to be the fastest growing technology in the world market for flow measurement. Coriolis mass flowmeters have not, however, had much success in penetrating the gas flow measurement market due to some limitations involved with measuring the low density fluids associated with low pressure gas flow measurement. A new type of Coriolis mass flowmeter has been developed which utilizes a unique new method of creating and measuring the requisite Coriolis forces. This new technology; radial mode Coriolis mass flow measurement, has several inherent features that make it perfectly suited to measuring the mass flow of gas.

  14. Gas flow analysis in melting furnaces

    SciTech Connect

    Kiss, L.I.; Bui, R.T.; Charette, A.; Bourgeois, T.

    1998-12-01

    The flow structure inside round furnaces with various numbers of burners, burner arrangement, and exit conditions has been studied experimentally with the purpose of improving the flow conditions and the resulting heat transfer. Small-scale transparent models were built according to the laws of geometric and dynamic similarity. Various visualization and experimental techniques were applied. The flow pattern in the near-surface regions was visualized by the fluorescent minituft and popcorn techniques; the flow structure in the bulk was analyzed by smoke injection and laser sheet illumination. For the study of the transient effects, high-speed video photography was applied. The effects of the various flow patterns, like axisymmetric and rotational flow, on the magnitude and uniformity of the residence time, as well as on the formation of stagnation zones, were discussed. Conclusions were drawn and have since been applied for the improvement of furnace performance.

  15. Gas/oil/water flow measurement by electrical capacitance tomography

    NASA Astrophysics Data System (ADS)

    Li, Yi; Yang, Wuqiang; Xie, Cheng-gang; Huang, Songming; Wu, Zhipeng; Tsamakis, Dimitrios; Lenn, Chris

    2013-07-01

    In the oil industry, it is important to measure gas/oil/water flows produced from oil wells. To determine oil production, it is necessary to measure the water-in-liquid ratio (WLR), liquid fraction and some other parameters, which are related to multiphase flow rates. A research team from the University of Manchester and Schlumberger Gould Research have developed an experimental apparatus for gas/oil/water flow measurement based on a flow-conditioning device and electrical capacitance tomography (ECT) and microwave sensors. This paper presents the ECT part of the developed apparatus, including the re-engineering of an ECT sensor and a model-based image reconstruction algorithm, which is used to derive the WLR and the thickness of the liquid layer in oil-continuous annular flows formed by the flow-conditioning device. The ECT sensor was tested both at Schlumberger and on TUV-NEL's Multiphase Flow Facility. The experimental results are promising.

  16. Sputter target

    DOEpatents

    Gates, Willard G.; Hale, Gerald J.

    1980-01-01

    The disclosure relates to an improved sputter target for use in the deposition of hard coatings. An exemplary target is given wherein titanium diboride is brazed to a tantalum backing plate using a gold-palladium-nickel braze alloy.

  17. Phase-locked measurements of gas-liquid horizontal flows

    NASA Astrophysics Data System (ADS)

    Zadrazil, Ivan; Matar, Omar; Markides, Christos

    2014-11-01

    A flow of gas and liquid in a horizontal pipe can be described in terms of various flow regimes, e.g. wavy stratified, annular or slug flow. These flow regimes appear at characteristic gas and liquid Reynolds numbers and feature unique wave phenomena. Wavy stratified flow is populated by low amplitude waves whereas annular flow contains high amplitude and long lived waves, so called disturbance waves, that play a key role in a liquid entrainment into the gas phase (droplets). In a slug flow regime, liquid-continuous regions travel at high speeds through a pipe separated by regions of stratified flow. We use a refractive index matched dynamic shadowgraphy technique using a high-speed camera mounted on a moving robotic linear rail to track the formation and development of features characteristic for the aforementioned flow regimes. We show that the wave dynamics become progressively more complex with increasing liquid and gas Reynolds numbers. Based on the shadowgraphy measurements we present, over a range of conditions: (i) phenomenological observations of the formation, and (ii) statistical data on the downstream velocity distribution of different classes of waves. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.

  18. Heat flow anomalies in oil- and gas-bearing structures

    SciTech Connect

    Sergiyenko, S.I.

    1988-02-01

    The main features of the distribution of heat flow values in oil, gas and gas-condensate fields on the continents have been discussed by Makarenko and Sergiyenko. The method of analysis used made it possible to establish that the presence of hydrocarbons in formations leads to high heat-flow, regardless of the age of folding of the potentially oil- and gas-bearing zones. Only in regions adjacent to marginal Cenozoic folded mountain structures and in zones of Cenozoic volcanism is the world average higher, by 2.5 to 10%, than in the oil- and gas-bearing structures in those regions. The earlier analysis of the distribution of heat flow values in oil and gas structures was based on 403 measurements. The author now has nearly doubled the sample population, enabling him substantially to revise the ideas on the distribution of heat flow values and the development of the thermal regime of local oil and gas structures. He notes that the method previously used, comparing heat flow values on young continental platforms with values in local oil and gas structures, makes it possible to estimate the thermal effect of the presence of oil and gas. This conclusion stems from the fact that the overwhelming majority of heat flow measurements were made on various kinds of positive structural forms, and distortions of the thermal field caused by thermal anisotropy phenomena are equally characteristic of both productive and nonproductive structures. As a result, for the first time a continuous time series of heat flow measurements over oil and gas structures in various tectonic regions, with ages of consolidation ranging from the Precambrian to the Cenozoic, was established. 26 references.

  19. Influence of the composition of gas mixture on the stoichiometry of sputter-deposited compound films: The case of zirconium nitrides

    SciTech Connect

    Wautelet, M.; Dauchot, J.P.; Debal, F.; Edart, S.; Hecq, M.

    1996-04-01

    By means of DC-reactive sputtering, it is possible to vary the stoichiometry of deposited zirconium nitrides, by varying the molar fraction of N{sub 2} in an Ar{endash}N{sub 2} gas mixture. In order to understand the origin of this effect, a theoretical model of reactive sputtering is devised. It is based on the study of reaction kinetics taking place at the surfaces of the cathode and the chamber walls. In fitting the model with experimental data, it turns out that one has to introduce the roles of Ar, N{sub 2}, and N species. For reactive sputtering of ZrN{sub {ital z}} films, a good fit is obtained when it is assumed that the molar fraction of N is constant when the molar fraction of N{sub 2} increases up to about 75{percent} (under our experimental conditions). Above this concentration of N{sub 2}, the concentration of N has to increase. By the analysis of the theoretical model, general scaling laws between experimental parameters (current, pressure, areas of the cathode and the chamber walls) are easily obtained. {copyright} {ital 1996 Materials Research Society.}

  20. Flowing gas, non-nuclear experiments on the gas core reactor

    NASA Technical Reports Server (NTRS)

    Kunze, J. F.; Cooper, C. G.; Macbeth, P. J.

    1973-01-01

    Variations in cavity wall and injection configurations of the gas core reactor were aimed at establishing flow patterns that give a maximum of the nuclear criticality eigenvalue. Correlation with the nuclear effect was made using multigroup diffusion theory normalized by previous benchmark critical experiments. Air was used to simulate the hydrogen propellant in the flow tests, and smoked air, argon, or Freon to simulate the central nuclear fuel gas. Tests were run both in the down-firing and upfiring directions. Results showed that acceptable flow patterns with volume fraction for the simulated nuclear fuel gas and high flow rate ratios of propellant to fuel can be obtained. Using a point injector for the fuel, good flow patterns are obtained by directing the outer gas at high velocity long the cavity wall, using louvered injection schemes. Recirculation patterns were needed to stabilize the heavy central gas when different gases are used.

  1. Gas flow dependence of atmospheric pressure plasma needle discharge characteristics

    NASA Astrophysics Data System (ADS)

    Qian, Muyang; Yang, Congying; Liu, Sanqiu; Chen, Xiaochang; Ni, Gengsong; Wang, Dezhen

    2016-04-01

    In this paper, a two-dimensional coupled model of neutral gas flow and plasma dynamics is presented to explain the gas flow dependence of discharge characteristics in helium plasma needle at atmospherics pressure. The diffusional mixing layer between the helium jet core and the ambient air has a moderate effect on the streamer propagation. The obtained simulation results present that the streamer shows the ring-shaped emission profile at a moderate gas flow rate. The key chemical reactions which drive the streamer propagation are electron-impact ionization of helium neutral, nitrogen and oxygen molecules. At a moderate gas flow rate of 0.5 slm, a significant increase in propagation velocity of the streamer is observed due to appropriate quantity of impurities air diffuse into the helium. Besides, when the gas flow rate is below 0.35 slm, the radial density of ground-state atomic oxygen peaks along the axis of symmetry. However, when the gas flow rate is above 0.5 slm, a ring-shaped density distribution appears. The peak density is on the order of 1020 m-3 at 10 ns in our work.

  2. On mechanisms of choked gas flows in microchannels

    NASA Astrophysics Data System (ADS)

    Shan, Xiaodong; Wang, Moran

    2015-10-01

    Choked gas flows in microchannels have been reported before based solely on experimental measurements, but the underlining physical mechanism has yet to be clarified. In this work, we are to explore the process via numerical modeling of choked gas flows through a straight microchannel that connects two gas reservoirs. The major theoretical consideration lies in that, since the gas in microchannels may not be necessarily rarefied even at a high Knudsen number, a generalized Monte Carlo method based on the Enskog theory, GEMC, was thus used instead of direct simulation Monte Carlo (DSMC). Our results indicate that the choked gas flows in microchannels can be divided into two types: sonic choking and subsonic choking, because the sonic point does not always exist even though the gas flows appear choked, depending on the inlet-outlet pressure ratio and the length-height ratio of the channel. Even if the gas flow does not reach a sonic point at the outlet region, the effective pressure ratio (pi /po) acting on the channel becomes asymptotically changeless when the pressure ratio on the buffer regions (pi‧/po‧) is higher than a certain value. The subsonic choking may caused by the expansion wave or the strong non-equilibrium effect at the outlet.

  3. 10. Photograph of a line drawing. 'PROCESS FLOW SCHEMATIC, GAS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. Photograph of a line drawing. 'PROCESS FLOW SCHEMATIC, GAS PRODUCER PROCESS, BUILDING 10A.' Holston Army Ammunition Plant, Holston Defense Corporation. August 29, 1974. Delineator: G. A. Horne. Drawing # SK-1942. - Holston Army Ammunition Plant, Producer Gas Plant, Kingsport, Sullivan County, TN

  4. Flammable gas interlock spoolpiece flow response test plan and procedure

    SciTech Connect

    Schneider, T.C., Fluor Daniel Hanford

    1997-02-13

    The purpose of this test plan and procedure is to test the Whittaker electrochemical cell and the Sierra Monitor Corp. flammable gas monitors in a simulated field flow configuration. The sensors are used on the Rotary Mode Core Sampling (RMCS) Flammable Gas Interlock (FGI), to detect flammable gases, including hydrogen and teminate the core sampling activity at a predetermined concentration level.

  5. Sub-surface gas flow in porous bodies

    NASA Astrophysics Data System (ADS)

    Teiser, Jens; Schywek, Mathias; de Beule, Caroline; Wurm, Gerhard

    2015-11-01

    Gas flow within porous media is of importance for various bodies in the Solar System. It occurs within the Martian soil, might be significant in the porous interiors of comets and also within dusty planetesimals in the Solar Nebula. In regimes of low atmospheric pressure, thermal creep leads to an efficient gas flux if temperature gradients are present, e.g. by solar insolation. This flow can lead to erosion or supports the exchange of volatiles within a porous body. Experiments showed that this gas flux dominates over diffusive gas transport under Martian conditions with gas velocities on the order of cm/s. Results from the Rosetta spacecraft suggest that eolian processes occur on comets which might be related to thermal creep gas flow. Here, we present new results of microgravity experiments on a thermally induced gas flow. Gas velocities and their dependence on the atmospheric pressure for different gases (Helium and air) are studied as well as the influence of the geometry of the pores.

  6. System for controlling the flow of gas into and out of a gas laser

    DOEpatents

    Alger, Terry; Uhlich, Dennis M.; Benett, William J.; Ault, Earl R.

    1994-01-01

    A modularized system for controlling the gas pressure within a copper vapor or like laser is described herein. This system includes a gas input assembly which serves to direct gas into the laser in a controlled manner in response to the pressure therein for maintaining the laser pressure at a particular value, for example 40 torr. The system also includes a gas output assembly including a vacuum pump and a capillary tube arrangement which operates within both a viscous flow region and a molecular flow region for drawing gas out of the laser in a controlled manner.

  7. Lagrangian solution of supersonic real gas flows

    SciTech Connect

    Loh, Chingyuen; Liou, Mengsing )

    1993-01-01

    This paper details the procedure of the real gas Riemann solution in the Lagrangian approach originally proposed by Loh and Hui for perfect gases. The extension to real gases is nontrivial and requires substantial development of an exact real-gas Riemann solver for the Lagrangian form of conservation laws. The first-order Gudonov scheme is enhanced for accuracy by adding limited anti-diffusive terms according to Sweby. Extensive calculations were made to test the accuracy and robustness of the present real gas Lagrangian approach, including complex wave interactions of different types. The accuracy for capturing 2D oblique waves and slip line is clearly demonstrated. In addition, we also show the real gas effect in a generic engine nozzle.

  8. Coupling compositional liquid gas Darcy and free gas flows at porous and free-flow domains interface

    NASA Astrophysics Data System (ADS)

    Masson, R.; Trenty, L.; Zhang, Y.

    2016-09-01

    This paper proposes an efficient splitting algorithm to solve coupled liquid gas Darcy and free gas flows at the interface between a porous medium and a free-flow domain. This model is compared to the reduced model introduced in [6] using a 1D approximation of the gas free flow. For that purpose, the gas molar fraction diffusive flux at the interface in the free-flow domain is approximated by a two point flux approximation based on a low-frequency diagonal approximation of a Steklov-Poincaré type operator. The splitting algorithm and the reduced model are applied in particular to the modelling of the mass exchanges at the interface between the storage and the ventilation galleries in radioactive waste deposits.

  9. Driver gas flow with fluctuations. [shock tube turbulent bursts

    NASA Technical Reports Server (NTRS)

    Johnson, J. A., III; Jones, W. R.; Santiago, J.

    1980-01-01

    A shock tube's driver gas can apparently provide flow with turbulent bursts. The fluctuations are interpreted using a boundary layer model of contact surface flow and results form a kinetic theory of turbulence. With this, a lower limit of 4 on the ratio of maximum to minimum turbulent intensities in contact surface instabilities has been estimated.

  10. P-type semiconducting gas sensing behavior of nanoporous rf sputtered CaCu{sub 3}Ti{sub 4}O{sub 12} thin films

    SciTech Connect

    Joanni, E.; Savu, R.; Bueno, P. R.; Longo, E.; Varela, J. A.

    2008-03-31

    The fabrication of nanoporous sputtered CaCu{sub 3}Ti{sub 4}O{sub 12} thin films with high gas sensitivity is reported in this work. The porous microstructure and the nanocrystalline nature of the material promoted the diffusion of the atmosphere into the film, shortening the response time of the samples. Behaving as p-type semiconductor, the material presents enhanced sensitivity even at low working temperatures. Impedance spectroscopy measurements were performed in order to investigate the mechanisms responsible for the performance of the devices.

  11. Deposition and characterization of zirconium nitride (ZrN) thin films by reactive magnetron sputtering with linear gas ion source and bias voltage

    SciTech Connect

    Kavitha, A.; Kannan, R.; Subramanian, N. Sankara; Loganathan, S.

    2014-04-24

    Zirconium nitride thin films have been prepared on stainless steel substrate (304L grade) by reactive cylindrical magnetron sputtering method with Gas Ion Source (GIS) and bias voltage using optimized coating parameters. The structure and surface morphologies of the ZrN films were characterized using X-ray diffraction, atomic microscopy and scanning electron microscopy. The adhesion property of ZrN thin film has been increased due to the GIS. The coating exhibits better adhesion strength up to 10 N whereas the ZrN thin film with bias voltage exhibits adhesion up to 500 mN.

  12. Characterization of thin MoO3 films formed by RF and DC-magnetron reactive sputtering for gas sensor applications

    NASA Astrophysics Data System (ADS)

    Yordanov, R.; Boyadjiev, S.; Georgieva, V.; Vergov, L.

    2014-05-01

    The present work discusses a technology for deposition and characterization of thin molybdenum oxide (MoOx, MoO3) films studied for gas sensor applications. The samples were produced by reactive radio-frequency (RF) and direct current (DC) magnetron sputtering. The composition and microstructure of the films were studied by XPS, XRD and Raman spectroscopy, the morphology, using high resolution SEM. The research was focused on the sensing properties of the sputtered thin MoO3 films. Highly sensitive gas sensors were implemented by depositing films of various thicknesses on quartz resonators. Making use of the quartz crystal microbalance (QCM) method, these sensors were capable of detecting changes in the molecular range. Prototype QCM structures with thin MoO3 films were tested for sensitivity to NH3 and NO2. Even in as-deposited state and without heating the substrates, these films showed good sensitivity. Moreover, no additional thermal treatment is necessary, which makes the production of such QCM gas sensors simple and cost-effective, as it is fully compatible with the technology for producing the initial resonator. The films are sensitive at room temperature and can register concentrations as low as 50 ppm. The sorption is fully reversible, the films are stable and capable of long-term measurements.

  13. Progress in Creating Stabilized Gas Layers in Flowing Liquid Mercury

    SciTech Connect

    Wendel, Mark W; Felde, David K; Riemer, Bernie; Abdou, Ashraf A; D'Urso, Brian R; West, David L

    2009-01-01

    The Spallation Neutron Source (SNS) facility in Oak Ridge, Tennessee uses a liquid mercury target that is bombarded with protons to produce a pulsed neutron beam for materials research and development. In order to mitigate expected cavitation damage erosion (CDE) of the containment vessel, a two-phase flow arrangement of the target has been proposed and was earlier proven to be effective in significantly reducing CDE in non-prototypical target bodies. This arrangement involves covering the beam "window", through which the high-energy proton beam passes, with a protective layer of gas. The difficulty lies in establishing a stable gas/liquid interface that is oriented vertically with the window and holds up to the strong buoyancy force and the turbulent mercury flow field. Three approaches to establishing the gas wall have been investigated in isothermal mercury/gas testing on a prototypical geometry and flow: (1) free gas layer approach, (2) porous wall approach, and (3) surface-modified approach. The latter two of these approaches show success in that a stabilized gas layer is produced. Both of these successful approaches capitalize on the high surface energy of liquid mercury by increasing the surface area of the solid wall, thus increasing gas hold up at the wall. In this paper, a summary of these experiments and findings is presented as well as a description of the path forward toward incorporating the stabilized gas layer approach into a feasible gas/mercury SNS target design.

  14. Sputter deposition of nanocrystalline beta-SiC films and molecular dynamics simulations of the sputter process.

    PubMed

    Ziebert, Carlos; Ye, Jian; Ulrich, Sven; Prskalo, Alen-Pilip; Schmauder, Siegfried

    2010-02-01

    Thin nanocrystalline films of silicon carbide (SiC) have been deposited on Si substrates by rf magnetron sputtering in pure Ar atmosphere. Simultaneously classical molecular dynamics (MD) simulations of sputtering of beta-SiC by Ar atoms were performed using IMD and Materials Explorer software with a combination of the Tersoff and the Ziegler-Biersack-Littmark (ZBL) potential in order to get more insight into the sputter process. In experiments the bias voltage (0 to -40 V) has been varied at constant substrate temperature of 900 degrees C to investigate the influence on the composition, the constitution and the mechanical properties of crystalline beta-SiC films. At second the substrate temperature has been varied between 900 degrees C and 100 degrees C to find the minimum substrate temperature that is needed to get nanocrystalline beta-SiC under the applied sputter conditions (ceramic SiC target, 300 W rf power, 18 cm target-substrate distance, 50 sccm Ar gas flow, 0.26 Pa total gas pressure). The films have been characterized by electron probe micro-analysis (EPMA), X-ray diffraction (XRD), Raman spectroscopy and atomic force microscopy (AFM). Hardness and residual stress have been investigated by nanoindentation and wafer bending. In the MD simulations the sputter yield was determined as a function of the energy of the incident Ar atoms (in the interesting range for sputter deposition, i.e., 50-1000 eV). To our knowledge this is the first time that the sputter yield of a SiC target was determined as a function of the energy of the incident Ar atoms in the low energy range by using MD simulations and compared with experimental results. PMID:20352766

  15. Cylindrical Couette flows of a rarefied gas with evaporation and condensation: Reversal and bifurcation of flows

    NASA Astrophysics Data System (ADS)

    Sone, Yoshio; Sugimoto, Hiroshi; Aoki, Kazuo

    1999-02-01

    A rarefied gas between two coaxial circular cylinders made of the condensed phase of the gas is considered, where each cylinder is kept at a uniform temperature and is rotating at a constant angular velocity around its axis (cylindrical Couette flows of a rarefied gas with evaporation or condensation on the cylinders). The steady behavior of the gas, with special interest in bifurcation of a flow, is studied on the basis of kinetic theory from the continuum to the Knudsen limit. The solution shows profound variety: reversal of direction of evaporation-condensation with variation of the speed of rotation of the cylinders; contrary to the conventional cylindrical Couette flow without evaporation and condensation, bifurcation of a flow in a simple case where the state of the gas is circumferentially and axially uniform.

  16. Internal flows of relevance to gas-turbines

    NASA Astrophysics Data System (ADS)

    McGuirk, J. J.; Whitelaw, J. H.

    An attempt is made to formulate the best combination of equations, numerical discretization, and turbulence modeling assumptions for internal aerodynamic flows relevant to gas turbines. Typical of the problems treated are the solution of the three-dimensional, time-averaged Navier-Stokes equations for laminar and turbulent flow in 90-deg bends, and the relative advantages obtainable from parabolized forms in bends, in S-type intake ducts, in turbine blade passages, and in forced mixers. In the present discussion of the influence of numerical assumptions on the calculation of isothermal flow in gas turbine combustors, emphasis is given to the assessment and removal of numerical errors.

  17. DYNAMIC MODELING STRATEGY FOR FLOW REGIME TRANSITION IN GAS-LIQUID TWO-PHASE FLOWS

    SciTech Connect

    X. Wang; X. Sun; H. Zhao

    2011-09-01

    In modeling gas-liquid two-phase flows, the concept of flow regime has been used to characterize the global interfacial structure of the flows. Nearly all constitutive relations that provide closures to the interfacial transfers in two-phase flow models, such as the two-fluid model, are often flow regime dependent. Currently, the determination of the flow regimes is primarily based on flow regime maps or transition criteria, which are developed for steady-state, fully-developed flows and widely applied in nuclear reactor system safety analysis codes, such as RELAP5. As two-phase flows are observed to be dynamic in nature (fully-developed two-phase flows generally do not exist in real applications), it is of importance to model the flow regime transition dynamically for more accurate predictions of two-phase flows. The present work aims to develop a dynamic modeling strategy for determining flow regimes in gas-liquid two-phase flows through the introduction of interfacial area transport equations (IATEs) within the framework of a two-fluid model. The IATE is a transport equation that models the interfacial area concentration by considering the creation and destruction of the interfacial area, such as the fluid particle (bubble or liquid droplet) disintegration, boiling and evaporation; and fluid particle coalescence and condensation, respectively. For the flow regimes beyond bubbly flows, a two-group IATE has been proposed, in which bubbles are divided into two groups based on their size and shape (which are correlated), namely small bubbles and large bubbles. A preliminary approach to dynamically identifying the flow regimes is provided, in which discriminators are based on the predicted information, such as the void fraction and interfacial area concentration of small bubble and large bubble groups. This method is expected to be applied to computer codes to improve their predictive capabilities of gas-liquid two-phase flows, in particular for the applications in

  18. Equations and simulations for multiphase compressible gas-dust flows

    NASA Astrophysics Data System (ADS)

    Oran, Elaine; Houim, Ryan

    2014-11-01

    Dust-gas multiphase flows are important in physical scenarios such as dust explosions in coal mines, asteroid impact disturbing lunar regolith, and soft aircraft landings dispersing desert or beach sand. In these cases, the gas flow regime can range from highly subsonic and nearly incompressible to supersonic and shock-laden flow, the grain packing can range from fully packed to completely dispersed, and both the gas and the dust can range from chemically inert to highly exothermic. To cover the necessary parameter range in a single model, we solve coupled sets of Navier-Stokes equations describing the background gas and the dust. As an example, a reactive-dust explosion that results in a type of shock-flame complex is described and discussed. Sponsored by the University of Maryland through Minta Martin Endowment Funds in the Department of Aerospace Engineering, and through the Glenn L. Martin Institute Chaired Professorship at the A. James Clark School of Engineering.

  19. Vacuum rated flow controllers for inert gas ion engines

    NASA Technical Reports Server (NTRS)

    Pless, L. C.

    1987-01-01

    Electrical propulsion systems which use a gas as a propellant require a gas flowmeter/controller which is capable of operating in a vacuum environment. The presently available instruments in the required flow ranges are designed and calibrated for use at ambient pressure. These instruments operate by heating a small diameter tube through which the gas is flowing and then sensing the change in temperature along the length of the tube. This temperature change is a function of the flow rate and the gas heat capacity. When installed in a vacuum, the change in the external thermal characteristics cause the tube to overheat and the temperature sensors are then operating outside their calibrated range. In addition, the variation in heat capacity with temperature limit the accuracy obtainable. These problems and the work in progress to solve them are discussed.

  20. Gas-Particle Interactions in a Microgravity Flow Cell

    NASA Technical Reports Server (NTRS)

    Louge, Michel; Jenkins, James

    1999-01-01

    We are developing a microgravity flow cell in which to study the interaction of a flowing gas with relatively massive particles that collide with each other and with the moving boundaries of the cell. The absence of gravity makes possible the independent control of the relative motion of the boundaries and the flow of the gas. The cell will permit gas-particle interactions to be studied over the entire range of flow conditions over which the mixture is not turbulent. Within this range, we shall characterize the viscous dissipation of the energy of the particle fluctuations, measure the influence of particle-phase viscosity on the pressure drop along the cell, and observe the development of localized inhomogeneities that are likely to be associated with the onset of clusters. These measurements and observations should contribute to an understanding of the essential physics of pneumatic transport.

  1. Real life experience with multipath ultrasonic gas flow meters

    SciTech Connect

    Sakariassen, R.

    1996-12-31

    Multipath ultrasonic gas flow meters are to be considered as newcomers among flow meters for large, high pressure gas flows. Although the advantages of this type of meters are many and obvious, the metering community is still hesitating to go for it mainly because of lack of experience. The objective of this paper is to present the experience of Statoil after more than six years experience with multipath ultrasonic gas flow meters. Their experience includes laboratory testing and operation in the field for a variety of designs and dimensions. This paper presents the accuracy achieved by such meters including comparison between ultrasonic meters and orifice metering systems in operation, the unique possibilities that this type of meter offers for on-line verification of performance and installation effects. Of particular interest should be noted that in the vicinity of low-noise control valves, such meters could stop functioning completely if no precautions are taken.

  2. Lagrangian solution of supersonic real gas flows

    NASA Technical Reports Server (NTRS)

    Loh, Ching-Yuen; Liou, Meng-Sing

    1993-01-01

    The present extention of a Lagrangian approach of the Riemann solution procedure, which was originally proposed for perfect gases, to real gases, is nontrivial and requires the development of an exact real-gas Riemann solver for the Lagrangian form of the conservation laws. Calculations including complex wave interactions of various types were conducted to test the accuracy and robustness of the approach. Attention is given to the case of 2D oblique waves' capture, where a slip line is clearly in evidence; the real gas effect is demonstrated in the case of a generic engine nozzle.

  3. Reactive sputter deposition of boron nitride

    SciTech Connect

    Jankowski, A.F.; Hayes, J.P.; McKernan, M.A.; Makowiecki, D.M.

    1995-10-01

    The preparation of fully dense, boron targets for use in planar magnetron sources has lead to the synthesis of Boron Nitride (BN) films by reactive rf sputtering. The deposition parameters of gas pressure, flow and composition are varied along with substrate temperature and applied bias. The films are characterized for composition using Auger electron spectroscopy, for chemical bonding using Raman spectroscopy and for crystalline structure using transmission electron microscopy. The deposition conditions are established which lead to the growth of crystalline BN phases. In particular, the growth of an adherent cubic BN coating requires 400--500 C substrate heating and an applied {minus}300 V dc bias.

  4. Intercooler flow path for gas turbines: CFD design and experiments

    SciTech Connect

    Agrawal, A.K.; Gollahalli, S.R.; Carter, F.L.

    1995-10-01

    The Advanced Turbine Systems (ATS) program was created by the U.S. Department of Energy to develop ultra-high efficiency, environmentally superior, and cost competitive gas turbine systems for generating electricity. Intercooling or cooling of air between compressor stages is a feature under consideration in advanced cycles for the ATS. Intercooling entails cooling of air between the low pressure (LP) and high pressure (BP) compressor sections of the gas turbine. Lower air temperature entering the HP compressor decreases the air volume flow rate and hence, the compression work. Intercooling also lowers temperature at the HP discharge, thus allowing for more effective use of cooling air in the hot gas flow path. The thermodynamic analyses of gas turbine cycles with modifications such as intercooling, recuperating, and reheating have shown that intercooling is important to achieving high efficiency gas turbines. The gas turbine industry has considerable interest in adopting intercooling to advanced gas turbines of different capacities. This observation is reinforced by the US Navys Intercooled-Recuperative (ICR) gas turbine development program to power the surface ships. In an intercooler system, the air exiting the LP compressor must be decelerated to provide the necessary residence time in the heat exchanger. The cooler air must subsequently be accelerated towards the inlet of the HP compressor. The circumferential flow nonuniformities inevitably introduced by the heat exchanger, if not isolated, could lead to rotating stall in the compressors, and reduce the overall system performance and efficiency. Also, the pressure losses in the intercooler flow path adversely affect the system efficiency and hence, must be minimized. Thus, implementing intercooling requires fluid dynamically efficient flow path with minimum flow nonuniformities and consequent pressure losses.

  5. Cascading Tesla Oscillating Flow Diode for Stirling Engine Gas Bearings

    NASA Technical Reports Server (NTRS)

    Dyson, Rodger

    2012-01-01

    Replacing the mechanical check-valve in a Stirling engine with a micromachined, non-moving-part flow diode eliminates moving parts and reduces the risk of microparticle clogging. At very small scales, helium gas has sufficient mass momentum that it can act as a flow controller in a similar way as a transistor can redirect electrical signals with a smaller bias signal. The innovation here forces helium gas to flow in predominantly one direction by offering a clear, straight-path microchannel in one direction of flow, but then through a sophisticated geometry, the reversed flow is forced through a tortuous path. This redirection is achieved by using microfluid channel flow to force the much larger main flow into this tortuous path. While microdiodes have been developed in the past, this innovation cascades Tesla diodes to create a much higher pressure in the gas bearing supply plenum. In addition, the special shape of the leaves captures loose particles that would otherwise clog the microchannel of the gas bearing pads.

  6. Gas-Liquid Flows and Phase Separation

    NASA Technical Reports Server (NTRS)

    McQuillen, John

    2004-01-01

    Common issues for space system designers include:Ability to Verify Performance in Normal Gravity prior to Deployment; System Stability; Phase Accumulation & Shedding; Phase Separation; Flow Distribution through Tees & Manifolds Boiling Crisis; Heat Transfer Coefficient; and Pressure Drop.The report concludes:Guidance similar to "A design that operates in a single phase is less complex than a design that has two-phase flow" is not always true considering the amount of effort spent on pressurizing, subcooling and phase separators to ensure single phase operation. While there is still much to learn about two-phase flow in reduced gravity, we have a good start. Focus now needs to be directed more towards system level problems .

  7. Droplet breakup in accelerating gas flows. Part 1: Primary atomization

    NASA Technical Reports Server (NTRS)

    Zajac, L. J.

    1973-01-01

    An experimental study of the effects of an accelerating gas flow on the atomization characteristics of liquid sprays was conducted. The sprays were produced by impinging two liquid jets. The liquid was molten wax, while the gas was nitrogen. The use of molten wax allowed for a quantitative measure of the resulting dropsize distribution. The effects of the accelerating gas flow on the formation of the spray were examined. The results of this study indicate that the parameters that most affect the resulting dropsize are the injector parameters of orifice diameter and injection velocity, the maximum gas velocity, and the distance from the injector face at which the maximum gas velocity is attained. Empirical correlations for both the mass median dropsize and the dropsize distribution are presented. These correlations can be readily incorporated into existing computer codes for the purpose of calculating rocket engine combustion performance.

  8. Flow field thermal gradient gas chromatography.

    PubMed

    Boeker, Peter; Leppert, Jan

    2015-09-01

    Negative temperature gradients along the gas chromatographic separation column can maximize the separation capabilities for gas chromatography by peak focusing and also lead to lower elution temperatures. Unfortunately, so far a smooth thermal gradient over a several meters long separation column could only be realized by costly and complicated manual setups. Here we describe a simple, yet flexible method for the generation of negative thermal gradients using standard and easily exchangeable separation columns. The measurements made with a first prototype reveal promising new properties of the optimized separation process. The negative thermal gradient and the superposition of temperature programming result in a quasi-parallel separation of components each moving simultaneously near their lowered specific equilibrium temperatures through the column. Therefore, this gradient separation process is better suited for thermally labile molecules such as explosives and natural or aroma components. High-temperature GC methods also benefit from reduced elution temperatures. Even for short columns very high peak capacities can be obtained. In addition, the gradient separation is particularly beneficial for very fast separations below 1 min overall retention time. Very fast measurements of explosives prove the benefits of using negative thermal gradients. The new concept can greatly reduce the cycle time of high-resolution gas chromatography and can be integrated into hyphenated or comprehensive gas chromatography setups. PMID:26235451

  9. Modeling target erosion during reactive sputtering

    NASA Astrophysics Data System (ADS)

    Strijckmans, K.; Depla, D.

    2015-03-01

    The influence of the reactive sputter conditions on the racetrack and the sputter profile for an Al/O2 DC reactive sputter system is studied by modeling. The role of redeposition, i.e. the deposition of sputtered material back on the target, is therefore taken into account. The used model RSD2013 is capable of simulating the effect of redeposition on the target condition in a spatial resolved way. Comparison between including and excluding redeposition in the RSD2013 model shows that the in-depth oxidation profile of the target differs. Modeling shows that it is important to distinguish between the formed racetrack, i.e. the erosion depth profile, and the sputter profile. The latter defines the distribution of the sputtered atoms in the vacuum chamber. As the target condition defines the sputter yield, it does determine the racetrack and the sputter profile of the planar circular target. Both the shape of the racetrack and the sputter profile change as function of the redeposition fraction as well as function of the oxygen flow change. Clear asymmetries and narrowing are observed for the racetrack shape. Similar effects are noticed for the sputter profile but to a different extent. Based on this study, the often heard misconception that the racetrack shape defines the distribution of the sputtered atoms during reactive sputtering is proven to be wrong.

  10. Gas-Dynamic Transients Flow Networks

    Energy Science and Technology Software Center (ESTSC)

    1987-09-01

    TVENT1P predicts flows and pressures in a ventilation system or other air pathway caused by pressure transients, such as a tornado. For an analytical model to simulate an actual system, it must have (1) the same arrangement of components in a network of flow paths; (2) the same friction characteristics; (3) the same boundary pressures; (4) the same capacitance; and (5) the same forces that drive the air. A specific set of components used formore » constructing the analytical model includes filters, dampers, ducts, blowers, rooms, or volume connected at nodal points to form networks. The effects of a number of similar components can be lumped into a single one. TVENT1P contains a material transport algorithm and features for turning blowers off and on, changing blower speeds, changing the resistance of dampers and filters, and providing a filter model to handle very high flows. These features make it possible to depict a sequence of events during a single run. Component properties are varied using time functions. The filter model is not used by the code unless it is specified by the user. The basic results of a TVENT1P solution are flows in branches and pressures at nodes. A postprocessor program, PLTTEX, is included to produce the plots specified in the TVENT1P input. PLTTEX uses the proprietary CA-DISSPLA graphics software.« less

  11. About the statistical description of gas-liquid flows

    SciTech Connect

    Sanz, D.; Guido-Lavalle, G.; Carrica, P.

    1995-09-01

    Elements of the probabilistic geometry are used to derive the bubble coalescence term of the statistical description of gas liquid flows. It is shown that the Boltzmann`s hypothesis, that leads to the kinetic theory of dilute gases, is not appropriate for this kind of flows. The resulting integro-differential transport equation is numerically integrated to study the flow development in slender bubble columns. The solution remarkably predicts the transition from bubbly to slug flow pattern. Moreover, a bubbly bimodal size distribution is predicted, which has already been observed experimentally.

  12. Gas mass transfer for stratified flows

    SciTech Connect

    Duffey, R.B.; Hughes, E.D.

    1995-07-01

    We analyzed gas absorption and release in water bodies using existing surface renewal theory. We show a new relation between turbulent momentum and mass transfer from gas to water, including the effects of waves and wave roughness, by evaluating the equilibrum integral turbulent dissipation due to energy transfer to the water from the wind. Using Kolmogoroff turbulence arguments the gas transfer velocity, or mass transfer coefficient, is then naturally and straightforwardly obtained as a non-linear function of the wind speed drag coefficient and the square root of the molecular diffusion coefficient. In dimensionless form, the theory predicts the turbulent Sherwood number to be Sh{sub t} = (2/{radical}{pi}) Sc{sup 1/2}, where Sh{sub t} is based on an integral dissipation length scale in the air. The theory confirms the observed nonlinear variation of the mass transfer coefficient as a function of the wind speed; gives the correct transition with turbulence-centered models for smooth surfaces at low speeds; and predicts experimental data from both laboratory and environmental measurements within the data scatter. The differences between the available laboratory and field data measurements are due to the large differences in the drag coefficient between wind tunnels and oceans. The results also imply that the effect of direct aeration due to bubble entrainment at wave breaking is no more than a 20% increase in the mass transfer for the highest speeds. The theory has importance to mass transfer in both the geophysical and chemical engineering literature.

  13. Gas mass transfer for stratified flows

    SciTech Connect

    Duffey, R.B.; Hughes, E.D.

    1995-06-01

    We analyzed gas absorption and release in water bodies using existing surface renewal theory. We show a new relation between turbulent momentum and mass transfer from gas to water, including the effects of waves and wave roughness, by evaluating the equilibrium integral turbulent dissipation due to energy transfer to the water from the wind. Using Kolmogoroff turbulence arguments the gas transfer velocity, or mass transfer coefficient, is then naturally and straightforwardly obtained as a non-linear function of the wind speed drag coefficient and the square root of the molecular diffusion coefficient. In dimensionless form, the theory predicts the turbulent Sherwood number to be Sh{sub t} = (2/{radical}{pi})Sc{sup 1/2}, where Sh{sub t} is based on an integral dissipation length scale in the air. The theory confirms the observed nonlinear variation of the mass transfer coefficient as a function of the wind speed; gives the correct transition with turbulence-centered models for smooth surfaces at low speeds; and predicts experimental data from both laboratory and environmental measurements within the data scatter. The differences between the available laboratory and field data measurements are due to the large differences in the drag coefficient between wind tunnels and oceans. The results also imply that the effect of direct aeration due to bubble entrainment at wave breaking is no more than a 20% increase in the mass transfer for the highest speeds. The theory has importance to mass transfer in both the geo-physical and chemical engineering literature.

  14. Two parametric flow measurement in gas-liquid two-phase flow

    NASA Astrophysics Data System (ADS)

    Chen, Z.; Chen, C.; Xu, Y.; Zhao, Z.

    The importance and current development of two parametric measurement during two-phase flow are briefly reviewed in this paper. Gas-liquid two-phase two parametric metering experiments were conducted by using an oval gear meter and a sharp edged orifice mounted in series in a horizontal pipe. Compressed air and water were used as gas and liquid phases respectively. The correlations, which can be used to predict the total flow rate and volumetric quality of two-phase flow or volumetric flow rate of each phase, have also been proposed in this paper. Comparison of the calculated values of flow rate of each phase from the correlations with the test data showed that the root mean square fractional deviation for gas flow rate is 2.9 percent and for liquid flow rate 4.4 percent. The method proposed in this paper can be used to measure the gas and liquid flow rate in two-phase flow region without having to separate the phases.

  15. Axial flow positive displacement worm gas generator

    NASA Technical Reports Server (NTRS)

    Murrow, Kurt David (Inventor); Giffin, Rollin George (Inventor); Fakunle, Oladapo (Inventor)

    2010-01-01

    An axial flow positive displacement engine has an inlet axially spaced apart and upstream from an outlet. Inner and outer bodies have offset inner and outer axes extend from the inlet to the outlet through first, second, and third sections of a core assembly in serial downstream flow relationship. At least one of the bodies is rotatable about its axis. The inner and outer bodies have intermeshed inner and outer helical blades wound about the inner and outer axes respectively. The inner and outer helical blades extend radially outwardly and inwardly respectively. The helical blades have first, second, and third twist slopes in the first, second, and third sections respectively. The first twist slopes are less than the second twist slopes and the third twist slopes are less than the second twist slopes. A combustor section extends axially downstream through at least a portion of the second section.

  16. Influence of oxygen flow rate on the structural, optical and electrical properties of ZnO films grown by DC magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Gobbiner, Chaya Ravi; Ali Avanee Veedu, Muhammed; Kekuda, Dhananjaya

    2016-04-01

    Zinc oxide thin films were deposited on glass substrates at different oxygen flow rates by DC reactive magnetron sputtering. The oxygen flow rate was found to be one of the crucial parameters which influence structural, optical and electrical properties of grown films. The structural and optical characterization of the deposited films was carried out using X-ray diffraction and UV-visible spectroscopy, respectively. Swanepoel envelope and Drude-Lorentz (DL) models were applied to extract the optoelectronic parameters such as refractive index, dispersion energy and plasma frequency. Structurally, grain size was found to decrease with increase in oxygen flow rate during deposition. Moreover, all the films exhibited preferred (002) orientation confirming c-axis orientation of the films perpendicular to the substrate. For a particular range of oxygen flow rates, columnar growth was achieved. Marginal increase in the optical band gap from 3.14 to 3.22 eV was observed as the oxygen flow rate increased from 3 to 10 sccm. Calculated plasma frequency from the DL model was found to be in the infrared region. It has decreased as oxygen flow rate increased with the value from 1.625 × 1014 rad/s (862 cm-1) to 1.072 × 1014 rad/s (568 cm-1).

  17. Turbine exhaust diffuser with region of reduced flow area and outer boundary gas flow

    DOEpatents

    Orosa, John

    2014-03-11

    An exhaust diffuser system and method for a turbine engine. The outer boundary may include a region in which the outer boundary extends radially inwardly toward the hub structure and may direct at least a portion of an exhaust flow in the diffuser toward the hub structure. At least one gas jet is provided including a jet exit located on the outer boundary. The jet exit may discharge a flow of gas downstream substantially parallel to an inner surface of the outer boundary to direct a portion of the exhaust flow in the diffuser toward the outer boundary to effect a radially outward flow of at least a portion of the exhaust gas flow toward the outer boundary to balance an aerodynamic load between the outer and inner boundaries.

  18. Do tropical wetland plants possess convective gas flow mechanisms?

    PubMed

    Konnerup, Dennis; Sorrell, Brian K; Brix, Hans

    2011-04-01

    • Internal pressurization and convective gas flow, which can aerate wetland plants more efficiently than diffusion, are common in temperate species. Here, we present the first survey of convective flow in a range of tropical plants. • The occurrence of pressurization and convective flow was determined in 20 common wetland plants from the Mekong Delta in Vietnam. The diel variation in pressurization in culms and the convective flow and gas composition from stubbles were examined for Eleocharis dulcis, Phragmites vallatoria and Hymenachne acutigluma, and related to light, humidity and air temperature. • Nine of the 20 species studied were able to build up a static pressure of > 50 Pa, and eight species had convective flow rates higher than 1 ml min(-1). There was a clear diel variation, with higher pressures and flows during the day than during the night, when pressures and flows were close to zero. • It is concluded that convective flow through shoots and rhizomes is a common mechanism for below-ground aeration of tropical wetland plants and that plants with convective flow might have a competitive advantage for growth in deep water. PMID:21175639

  19. Interaction of a surface glow discharge with a gas flow

    SciTech Connect

    Aleksandrov, A. L. Schweigert, I. V.

    2010-05-15

    A surface glow discharge in a gas flow is of particular interest as a possible tool for controlling the flow past hypersonic aircrafts. Using a hydrodynamic model of glow discharge, two-dimensional calculations for a kilovolt surface discharge in nitrogen at a pressure of 0.5 Torr are carried out in a stationary gas, as well as in a flow with a velocity of 1000 m/s. The discharge structure and plasma parameters are investigated near a charged electrode. It is shown that the electron energy in a cathode layer reaches 250-300 eV. Discharge is sustained by secondary electron emission. The influence of a high-speed gas flow on the discharge is considered. It is shown that the cathode layer configuration is flow-resistant. The distributions of the electric field and electron energy, as well as the ionization rate profile in the cathode layer, do not change qualitatively under the action of the flow. The basic effect of the flow's influence is a sharp decrease in the region of the quasineutral plasma surrounding the cathode layer due to fast convective transport of ions.

  20. Hybrid continuum-molecular modelling of multiscale internal gas flows

    NASA Astrophysics Data System (ADS)

    Patronis, Alexander; Lockerby, Duncan A.; Borg, Matthew K.; Reese, Jason M.

    2013-12-01

    We develop and apply an efficient multiscale method for simulating a large class of low-speed internal rarefied gas flows. The method is an extension of the hybrid atomistic-continuum approach proposed by Borg et al. (2013) [28] for the simulation of micro/nano flows of high-aspect ratio. The major new extensions are: (1) incorporation of fluid compressibility; (2) implementation using the direct simulation Monte Carlo (DSMC) method for dilute rarefied gas flows, and (3) application to a broader range of geometries, including periodic, non-periodic, pressure-driven, gravity-driven and shear-driven internal flows. The multiscale method is applied to micro-scale gas flows through a periodic converging-diverging channel (driven by an external acceleration) and a non-periodic channel with a bend (driven by a pressure difference), as well as the flow between two eccentric cylinders (with the inner rotating relative to the outer). In all these cases there exists a wide variation of Knudsen number within the geometries, as well as substantial compressibility despite the Mach number being very low. For validation purposes, our multiscale simulation results are compared to those obtained from full-scale DSMC simulations: very close agreement is obtained in all cases for all flow variables considered. Our multiscale simulation is an order of magnitude more computationally efficient than the full-scale DSMC for the first and second test cases, and two orders of magnitude more efficient for the third case.

  1. Hybrid continuum–molecular modelling of multiscale internal gas flows

    SciTech Connect

    Patronis, Alexander; Lockerby, Duncan A.; Borg, Matthew K.; Reese, Jason M.

    2013-12-15

    We develop and apply an efficient multiscale method for simulating a large class of low-speed internal rarefied gas flows. The method is an extension of the hybrid atomistic–continuum approach proposed by Borg et al. (2013) [28] for the simulation of micro/nano flows of high-aspect ratio. The major new extensions are: (1) incorporation of fluid compressibility; (2) implementation using the direct simulation Monte Carlo (DSMC) method for dilute rarefied gas flows, and (3) application to a broader range of geometries, including periodic, non-periodic, pressure-driven, gravity-driven and shear-driven internal flows. The multiscale method is applied to micro-scale gas flows through a periodic converging–diverging channel (driven by an external acceleration) and a non-periodic channel with a bend (driven by a pressure difference), as well as the flow between two eccentric cylinders (with the inner rotating relative to the outer). In all these cases there exists a wide variation of Knudsen number within the geometries, as well as substantial compressibility despite the Mach number being very low. For validation purposes, our multiscale simulation results are compared to those obtained from full-scale DSMC simulations: very close agreement is obtained in all cases for all flow variables considered. Our multiscale simulation is an order of magnitude more computationally efficient than the full-scale DSMC for the first and second test cases, and two orders of magnitude more efficient for the third case.

  2. Computation of layers in Eulerian gas flow

    NASA Astrophysics Data System (ADS)

    Hemker, P. W.

    A mixed defect-correction iteration process (MDCP) is applied for the implicit numerical solution of steady Euler flows. Without stability problems, MDCP can be applied with a straightforward 2nd order scheme such as central differences. A nearly monotonous representation of the thin layers is obtained by application of a 2nd order scheme with a proper flux-limiter. When combined with nonlinear multigrid (FAS) cycles, a few FAS-MDCP iteration steps are sufficient to determine the two solutions up to truncation-error accuracy.

  3. Gas, liquids flow rates hefty at Galveston Bay discovery

    SciTech Connect

    Petzet, G.A.

    1998-01-19

    Extended flow tests indicate a large Vicksburg (Oligocene) gas, condensate, and oil field is about to be developed in western Galveston Bay. Internal estimates indicates that ultimate recovery from the fault block in which the discovery well was drilled could exceed 1 tcf of gas equivalent of proved, possible, and probable reserves. The paper discusses the test program for this field and other prospects in the Galveston Bay area.

  4. Time-Resolved Rayleigh Scattering Measurements in Hot Gas Flows

    NASA Technical Reports Server (NTRS)

    Mielke, Amy F.; Elam, Kristie A.; Sung, Chih-Jen

    2008-01-01

    A molecular Rayleigh scattering technique is developed to measure time-resolved gas velocity, temperature, and density in unseeded gas flows at sampling rates up to 32 kHz. A high power continuous-wave laser beam is focused at a point in an air flow field and Rayleigh scattered light is collected and fiber-optically transmitted to the spectral analysis and detection equipment. The spectrum of the light, which contains information about the temperature and velocity of the flow, is analyzed using a Fabry-Perot interferometer. Photomultipler tubes operated in the photon counting mode allow high frequency sampling of the circular interference pattern to provide time-resolved flow property measurements. Mean and rms velocity and temperature fluctuation measurements in both an electrically-heated jet facility with a 10-mm diameter nozzle and also in a hydrogen-combustor heated jet facility with a 50.8-mm diameter nozzle at NASA Glenn Research Center are presented.

  5. Prediction of strongly-heated internal gas flows

    SciTech Connect

    McEligot, D.M. ||; Shehata, A.M.; Kunugi, Tomoaki |

    1997-12-31

    The purposes of the present article are to remind practitioners why the usual textbook approaches may not be appropriate for treating gas flows heated from the surface with large heat fluxes and to review the successes of some recent applications of turbulence models to this case. Simulations from various turbulence models have been assessed by comparison to the measurements of internal mean velocity and temperature distributions by Shehata for turbulent, laminarizing and intermediate flows with significant gas property variation. Of about fifteen models considered, five were judged to provide adequate predictions.

  6. Dynamic Modeling Strategy for Flow Regime Transition in Gas-Liquid Two-Phase Flows

    SciTech Connect

    Xia Wang; Xiaodong Sun; Benjamin Doup; Haihua Zhao

    2012-12-01

    In modeling gas-liquid two-phase flows, the concept of flow regimes has been widely used to characterize the global interfacial structure of the flows. Nearly all constitutive relations that provide closures to the interfacial transfers in two-phase flow models, such as the two-fluid model, are flow regime dependent. Current nuclear reactor safety analysis codes, such as RELAP5, classify flow regimes using flow regime maps or transition criteria that were developed for steady-state, fully-developed flows. As twophase flows are dynamic in nature, it is important to model the flow regime transitions dynamically to more accurately predict the two-phase flows. The present work aims to develop a dynamic modeling strategy to determine flow regimes in gas-liquid two-phase flows through introduction of interfacial area transport equations (IATEs) within the framework of a two-fluid model. The IATE is a transport equation that models the interfacial area concentration by considering the creation of the interfacial area, fluid particle (bubble or liquid droplet) disintegration, boiling and evaporation, and the destruction of the interfacial area, fluid particle coalescence and condensation. For flow regimes beyond bubbly flows, a two-group IATE has been proposed, in which bubbles are divided into two groups based on their size and shapes, namely group-1 and group-2 bubbles. A preliminary approach to dynamically identify the flow regimes is discussed, in which discriminator s are based on the predicted information, such as the void fraction and interfacial area concentration. The flow regime predicted with this method shows good agreement with the experimental observations.

  7. Correlations predict gas-condensate flow through chokes

    SciTech Connect

    Osman, M.E.; Dokla, M.E. )

    1992-03-16

    Empirical correlations have developed to describe the behavior of gas-condensate flow through surface chokes. The field data were obtained from a Middle East gas-condensate reservoir and cover a wide range of flow rates and choke sizes. Correlations for gas-condensate systems have not been previously available. These new correlations will help the production engineer to size chokes for controlling production of gas-condensate wells and predicting the performance of flowing wells under various conditions. Four forms of the correlation were developed and checked against data. One form correlates choke upstream pressure with liquid production rate, gas/liquid ratio, and choke size. The second form uses gas production rate instead of the liquid rate. The other two forms use the pressure drop across the choke instead of upstream pressure. All four of the correlations are presented in this paper as nomograms. Accuracy of the different forms was checked with five error parameters: root-mean-square error, mean-absolute error, simple-mean error, mean-percent-age-absolute error, and mean-percentage error. The correlation was found to be the most accurate when pressure-drop data are used instead of choke upstream pressure.

  8. Structural support bracket for gas flow path

    DOEpatents

    None

    2016-08-02

    A structural support system is provided in a can annular gas turbine engine having an arrangement including a plurality of integrated exit pieces (IEPs) forming an annular chamber for delivering gases from a plurality of combustors to a first row of turbine blades. A bracket structure is connected between an IEP and an inner support structure on the engine. The bracket structure includes an axial bracket member attached to an IEP and extending axially in a forward direction. A transverse bracket member has an end attached to the inner support structure and extends circumferentially to a connection with a forward end of the axial bracket member. The transverse bracket member provides a fixed radial position for the forward end of the axial bracket member and is flexible in the axial direction to permit axial movement of the axial bracket member.

  9. Effect of O{sub 2} flow ratio on the microstructure and stress of room temperature reactively sputtered RuO{sub x} thin films

    SciTech Connect

    Shi Junxia; Huang Feng; Weaver, Mark L.; Klein, Tonya M.

    2005-05-01

    RuO{sub x} thin films were deposited at room temperature by reactive radio frequency magnetron-sputtering using Ar/O{sub 2} discharges of varying O{sub 2} flow ratio (f{sub O{sub 2}}) over the range 10%-50% and were characterized using x-ray diffraction, x-ray reflectivity, x-ray photoelectron spectroscopy, resistivity, and stress-temperature measurements. With the increase of f{sub O{sub 2}}, the film texture changed from (110) to (101). Films deposited with f{sub O{sub 2}}>25% were determined stoichiometric. The residual stresses in as-deposited films were all compressive and increased with addition of O{sub 2}, except for the film sputtered at f{sub O{sub 2}}=20% which was in biaxial tension. The film deposited at f{sub O{sub 2}}=30% had a low resistivity value of 68 {mu}{omega} cm and near zero stress (<50 MPa tensile) after a thermal cycle in air up to 500 deg. C which is promising for use in microdevices.

  10. Influence of flowing helium gas on plasma plume formation in atmospheric pressure plasma

    SciTech Connect

    Yambe, Kiyoyuki; Konda, Kohmei; Ogura, Kazuo

    2015-05-15

    We have studied atmospheric pressure plasma generated using a quartz tube, helium gas, and a foil electrode by applying RF high voltage. The atmospheric pressure plasma in the form of a bullet is released as a plume into the atmosphere. The helium gas flowing out of quartz tube mixes with air, and the flow channel is composed of the regions of flowing helium gas and air. The plasma plume length is equivalent to the reachable distance of flowing helium gas. Although the amount of helium gas on the flow channel increases by increasing the inner diameter of quartz tube at the same gas flow velocity, the plasma plume length peaks at around 8 m/s of gas flow velocity, which is the result that a flow of helium gas is balanced with the amount of gas. The plasma plume is formed at the boundary region where the flow of helium gas is kept to the wall of the air.

  11. Laser absorption phenomena in flowing gas devices

    NASA Technical Reports Server (NTRS)

    Chapman, P. K.; Otis, J. H.

    1976-01-01

    A theoretical and experimental investigation is presented of inverse Bremsstrahlung absorption of CW CO2 laser radiation in flowing gases seeded with alkali metals. In order to motivate this development, some simple models are described of several space missions which could use laser powered rocket vehicles. Design considerations are given for a test call to be used with a welding laser, using a diamond window for admission of laser radiation at power levels in excess of 10 kW. A detailed analysis of absorption conditions in the test cell is included. The experimental apparatus and test setup are described and the results of experiments presented. Injection of alkali seedant and steady state absorption of the laser radiation were successfully demonstrated, but problems with the durability of the diamond windows at higher powers prevented operation of the test cell as an effective laser powered thruster.

  12. Influence of Oxygen Gas Ratio on the Properties of Aluminum-Doped Zinc Oxide Films Prepared by Radio Frequency Magnetron Sputtering.

    PubMed

    Kim, Minha; Jang, Yong-Jun; Jung, Ho-Sung; Song, Woochang; Kang, Hyunil; Kim, Eung Kwon; Kim, Donguk; Yi, Junsin; Lee, Jaehyeong

    2016-05-01

    Aluminum-doped zinc oxide (AZO) thin films were deposited on glass and polyimide substrates using radio frequency magnetron sputtering. We investigated the effects of the oxygen gas ratio on the properties of the AZO films for Cu(In,Ga)Se2 thin-film solar cell applications. The structural and optical properties of the AZO thin films were measured using X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and UV-Visible-NIR spectrophotometry. The oxygen gas ratio played a crucial role in controlling the optical as well as electrical properties of the films. When oxygen gas was added into the film, the surface AZO thin films became smoother and the grains were enlarged while the preferred orientation changed from (0 0 2) to (1 0 0) plane direction of the hexagonal phase. An improvement in the transmittance of the AZO thin films was achieved with the addition of 2.5-% oxygen gas. The electrical resistivity was highly increased even for a small amount of the oxygen gas addition. PMID:27483888

  13. Using the Multipole Resonance Probe to Stabilize the Electron Density During a Reactive Sputter Process

    NASA Astrophysics Data System (ADS)

    Oberberg, Moritz; Styrnoll, Tim; Ries, Stefan; Bienholz, Stefan; Awakowicz, Peter

    2015-09-01

    Reactive sputter processes are used for the deposition of hard, wear-resistant and non-corrosive ceramic layers such as aluminum oxide (Al2O3) . A well known problem is target poisoning at high reactive gas flows, which results from the reaction of the reactive gas with the metal target. Consequently, the sputter rate decreases and secondary electron emission increases. Both parameters show a non-linear hysteresis behavior as a function of the reactive gas flow and this leads to process instabilities. This work presents a new control method of Al2O3 deposition in a multiple frequency CCP (MFCCP) based on plasma parameters. Until today, process controls use parameters such as spectral line intensities of sputtered metal as an indicator for the sputter rate. A coupling between plasma and substrate is not considered. The control system in this work uses a new plasma diagnostic method: The multipole resonance probe (MRP) measures plasma parameters such as electron density by analyzing a typical resonance frequency of the system response. This concept combines target processes and plasma effects and directly controls the sputter source instead of the resulting target parameters.

  14. Characteristics of Al doped zinc oxide (ZAO) thin films deposited by RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Kobayakawa, Satoshi; Tanaka, Yoshikazu; Ide-Ektessabi, Ari

    2006-08-01

    ZAO and ITO thin films were prepared by RF magnetron sputtering. In this study, three of the sputtering parameters, that is, substrate temperature, oxygen flow rate and RF discharge power were varied separately to fabricate samples. The range of variation of substrate temperature was from room temperature to 623 K. The relative concentration of O2 in the ambient gas in the chamber was 0% or 25%. The sputtering rate was changed by controlling the discharge power. The minimum surface resistivity of ZAO was 2.53 × 102 Ω/cm2 for samples sputtered at a substrate temperature of 373 K and that of ITO was 2.37 × 101 Ω/cm2 sputtered under standard conditions. Visible light transmittances of these samples were 89.9% and 90.2%, respectively. From these results, it is suggested that when sputtered with optimum sputtering parameters, ZAO is a potential material for practical use for transparent conducting electrodes (TCO) for PDPs.

  15. Flow mechanism of Forchheimer's cubic equation in high-velocity radial gas flow through porous media

    SciTech Connect

    Ezeudembah, A.S.; Dranchuk, P.M.

    1982-01-01

    Formal derivation of Forchheimer's cubic equation is made by considering the kinetic energy equation of mean flow and dimensional relations for one-dimensional, linear, incompressible fluid flow. By the addition of the cubic term, this equation is regarded as a modified Forchheimer's quadratic equation which accounts for the flow rates obtained beyond the laminar flow condition. The cubic equation spans a wide range of flow rates and regimes. For suitable use in gas flow studies, this equation has been adapted, modified, and corrected for the gas slippage effect. The physical basis of the cubic term has been established by using boundary layer theory to explain the high-velocity, high-pressure flow behavior through a porous path. Gamma, the main parameter in the cubic term, is related directly to a characteristic, dimensionless shape factor which is significant at higher flow rates. It is inversely related to viscosity, but has no dependence on the gas slippage coefficient in the higher flow regime. 25 references.

  16. Disturbed flow and flow accelerated corrosion in oil and gas production

    SciTech Connect

    Efird, K.D.

    1998-12-31

    The effect of fluid flow on corrosion of steel in oil and gas environments involves a complex interaction of physical and chemical parameters. The basic requirement for any corrosion to occur is the existence of liquid water contacting the pipe wall, which is primarily controlled by the flow regime. The effect of flow on corrosion, or flow accelerated corrosion, is defined by the mass transfer and wall shear stress parameters existing in the water phase that contacts the pipe wall. While existing fluid flow equations for mass transfer and wall shear stress relate to equilibrium conditions, disturbed flow introduces non-equilibrium, steady state conditions not addressed by these equations, and corrosion testing in equilibrium conditions cannot be effectively related to corrosion in disturbed flow. The problem in relating flow effects to corrosion is that steel corrosion failures in oil and gas environments are normally associated with disturbed flow conditions as a result of weld beads, preexisting pits, bends, flanges, valves, tubing connections, etc. Steady state mass transfer and wall shear stress relationships to steel corrosion and corrosion testing are required for their application to corrosion of steel under disturbed flow conditions. A procedure is described to relate the results of a corrosion test directly to corrosion in an operation system where disturbed flow conditions are expected, or must be considered.

  17. Influence of Gas Flow Rate for Formation of Aligned Nanorods in ZnO Thin Films for Solar-Driven Hydrogen Production

    SciTech Connect

    Shet, S.; Chen, L.; Tang, H.; Nuggehalli, R.; Wang, H.; Yan, Y.; Turner, J.; Al-Jassim, M.

    2012-04-01

    ZnO thin films have been deposited in mixed Ar/N{sub 2} gas ambient at substrate temperature of 500 C by radiofrequency sputtering of ZnO targets. We find that an optimum N{sub 2}-to-Ar ratio in the deposition ambient promotes the formation of well-aligned nanorods. ZnO thin films grown in ambient with 25% N{sub 2} gas flow rate promoted nanorods aligned along c-axis and exhibit significantly enhanced photoelectrochemical (PEC) response, compared with ZnO thin films grown in an ambient with different N{sub 2}-to-Ar gas flow ratios. Our results suggest that chamber ambient is critical for the formation of aligned nanostructures, which offer potential advantages for improving the efficiency of PEC water splitting for H{sub 2} production.

  18. Modeling of Liquid Flow in a Packed Bed in the Presence of Gas Flow

    NASA Astrophysics Data System (ADS)

    Singh, V.; Gupta, G. S.; Sarkar, S.

    2007-06-01

    Liquid metal and slag descend through a porous coke matrix in the lower part of an iron making blast furnace. The size of the raceway is an important factor in determining the gas penetration into the bed, which pushes the liquid toward the deadman region. This, in turn, affects the gas flow in the bed. The current study tries to explain theoretically the effect of cavity size hysteresis on gas-liquid distribution in a packed bed. The liquid flow has been modeled considering it to be discrete in nature. The turbulent nature of gas flow has been modeled using the k-ɛ model for turbulent flow. The model results have been verified on a structured package. It is observed that the liquid is pushed away further from the nozzle-side wall in the case of decreasing gas velocity than increasing gas velocity at the same inlet gas velocity. The implications of the current study to the dropping zone of a blast furnace have been discussed.

  19. Hot Gas Flows in T Tauri Stars

    NASA Astrophysics Data System (ADS)

    Ardila, David R.; Herczeg, G.; Gregory, S. G.; Ingleby, L.; France, K.; Brown, A.; Edwards, S.; Linsky, J.; Yang, H.; Valenti, J. A.; Johns-Krull, C. M.; Alexander, R.; Bergin, E. A.; Bethell, T.; Brown, J.; Calvet, N.; Espaillat, C.; Hervé, A.; Hillenbrand, L.; Hussain, G.; Roueff, E.; Schindhelm, E.; Walter, F. M.

    2013-01-01

    We describe observations of the hot gas 1e5 K) ultraviolet lines C IV and He II, in Classical and Weak T Tauri Stars (CTTSs, WTTSs). Our goal is to provide observational constraints for realistic models. Most of the data for this work comes from the Hubble proposal “The Disks, Accretion, and Outflows (DAO) of T Tau stars” (PI Herczeg). The DAO program is the largest and most sensitive high resolution spectroscopic survey of young stars in the UV ever undertaken and it provides a rich source of information for these objects. The sample of high resolution COS and STIS spectra presented here comprises 35 stars: one Herbig Ae star, 28 CTTSs, and 6 WTTSs. For CTTSs, the lines consist of two kinematic components. The relative strengths of the narrow and broad components (NC, BC) are similar in C IV but in He II the NC is stronger than the BC, and dominates the line profile. We do not find correlations between disk inclination and the velocity centroid, width, or shape of the CIV line profile. The NC of the C IV line in CTTSs increases in strength with accretion rate, and its contribution to the line increases from ˜20% to ˜80%, for the accretion rates considered here (1e-10 to 1e-7 Msun/yr). The CTTSs C IV lines are redshifted by ˜20 km/s while the CTTSs He II are redshifted by ˜10 km/s. Because the He II line and the C IV NC have the same width in CTTSs and in WTTSs, but are correlated with accretion, we suggest that they are produced in the stellar transition region. The accretion shock model predicts that the velocity of the post-shock emission should be 4x smaller than the velocity of the pre-shock emission. Identifying the post-shock emission with the NC and the pre-shock with the BC, we find that this is approximately the case in 11 out of 23 objects. The model cannot explain 11 systems in which the velocity of the NC is smaller than the velocity of the BC, or systems in which one of the velocities is negative (five CTTSs). The hot gas lines in some systems

  20. Design and Uncertainty Analysis for a PVTt Gas Flow Standard

    PubMed Central

    Wright, John D.; Johnson, Aaron N.; Moldover, Michael R.

    2003-01-01

    A new pressure, volume, temperature, and, time (PVTt) primary gas flow standard at the National Institute of Standards and Technology has an expanded uncertainty (k = 2) of between 0.02 % and 0.05 %. The standard spans the flow range of 1 L/min to 2000 L/min using two collection tanks and two diverter valve systems. The standard measures flow by collecting gas in a tank of known volume during a measured time interval. We describe the significant and novel features of the standard and analyze its uncertainty. The gas collection tanks have a small diameter and are immersed in a uniform, stable, thermostatted water bath. The collected gas achieves thermal equilibrium rapidly and the uncertainty of the average gas temperature is only 7 mK (22 × 10−6 T). A novel operating method leads to essentially zero mass change in and very low uncertainty contributions from the inventory volume. Gravimetric and volume expansion techniques were used to determine the tank and the inventory volumes. Gravimetric determinations of collection tank volume made with nitrogen and argon agree with a standard deviation of 16 × 10−6 VT. The largest source of uncertainty in the flow measurement is drift of the pressure sensor over time, which contributes relative standard uncertainty of 60 × 10−6 to the determinations of the volumes of the collection tanks and to the flow measurements. Throughout the range 3 L/min to 110 L/min, flows were measured independently using the 34 L and the 677 L collection systems, and the two systems agreed within a relative difference of 150 × 10−6. Double diversions were used to evaluate the 677 L system over a range of 300 L/min to 1600 L/min, and the relative differences between single and double diversions were less than 75 × 10−6. PMID:27413592

  1. A Two-Dimensional Compressible Gas Flow Code

    Energy Science and Technology Software Center (ESTSC)

    1995-03-17

    F2D is a general purpose, two dimensional, fully compressible thermal-fluids code that models most of the phenomena found in situations of coupled fluid flow and heat transfer. The code solves momentum, continuity, gas-energy, and structure-energy equations using a predictor-correction solution algorithm. The corrector step includes a Poisson pressure equation. The finite difference form of the equation is presented along with a description of input and output. Several example problems are included that demonstrate the applicabilitymore » of the code in problems ranging from free fluid flow, shock tubes and flow in heated porous media.« less

  2. Review of coaxial flow gas core nuclear rocket fluid mechanics

    NASA Technical Reports Server (NTRS)

    Weinstein, H.

    1976-01-01

    Almost all of the fluid mechanics research associated with the coaxial flow gas core reactor ended abruptly with the interruption of NASA's space nuclear program because of policy and budgetary considerations in 1973. An overview of program accomplishments is presented through a review of the experiments conducted and the analyses performed. Areas are indicated where additional research is required for a fuller understanding of cavity flow and of the factors which influence cold and hot flow containment. A bibliography is included with graphic material.

  3. Large-Flow-Area Flow-Selective Liquid/Gas Separator

    NASA Technical Reports Server (NTRS)

    Vasquez, Arturo; Bradley, Karla F.

    2010-01-01

    This liquid/gas separator provides the basis for a first stage of a fuel cell product water/oxygen gas phase separator. It can separate liquid and gas in bulk in multiple gravity environments. The system separates fuel cell product water entrained with circulating oxygen gas from the outlet of a fuel cell stack before allowing the gas to return to the fuel cell stack inlet. Additional makeup oxygen gas is added either before or after the separator to account for the gas consumed in the fuel cell power plant. A large volume is provided upstream of porous material in the separator to allow for the collection of water that does not exit the separator with the outgoing oxygen gas. The water then can be removed as it continues to collect, so that the accumulation of water does not impede the separating action of the device. The system is designed with a series of tubes of the porous material configured into a shell-and-tube heat exchanger configuration. The two-phase fluid stream to be separated enters the shell-side portion of the device. Gas flows to the center passages of the tubes through the porous material and is then routed to a common volume at the end of the tubes by simple pressure difference from a pumping device. Gas flows through the porous material of the tubes with greater ease as a function of the ratio of the dynamic viscosity of the water and gas. By careful selection of the dimensions of the tubes (wall thickness, porosity, diameter, length of the tubes, number of the tubes, and tube-to-tube spacing in the shell volume) a suitable design can be made to match the magnitude of water and gas flow, developed pressures from the oxygen reactant pumping device, and required residual water inventory for the shellside volume.

  4. Empirical slip and viscosity model performance for microscale gas flows.

    SciTech Connect

    Gallis, Michail A.; Boyd, Iain D.; McNenly, Matthew J.

    2004-07-01

    For the simple geometries of Couette and Poiseuille flows, the velocity profile maintains a similar shape from continuum to free molecular flow. Therefore, modifications to the fluid viscosity and slip boundary conditions can improve the continuum based Navier-Stokes solution in the non-continuum non-equilibrium regime. In this investigation, the optimal modifications are found by a linear least-squares fit of the Navier-Stokes solution to the non-equilibrium solution obtained using the direct simulation Monte Carlo (DSMC) method. Models are then constructed for the Knudsen number dependence of the viscosity correction and the slip model from a database of DSMC solutions for Couette and Poiseuille flows of argon and nitrogen gas, with Knudsen numbers ranging from 0.01 to 10. Finally, the accuracy of the models is measured for non-equilibrium cases both in and outside the DSMC database. Flows outside the database include: combined Couette and Poiseuille flow, partial wall accommodation, helium gas, and non-zero convective acceleration. The models reproduce the velocity profiles in the DSMC database within an L{sub 2} error norm of 3% for Couette flows and 7% for Poiseuille flows. However, the errors in the model predictions outside the database are up to five times larger.

  5. Long arc stabilities with various arc gas flow rates

    NASA Astrophysics Data System (ADS)

    Maruyama, K.; Takeda, K.; Sugimoto, M.; Noguchi, Y.

    2014-11-01

    A new arc torch for use in magnetically driven arc device was developed with a commercially available TIG welding arc torch. The torch has a water-cooling system to the torch nozzle and has a nozzle nut to supply a swirling-free plasma gas flow. Its endurance against arc thermal load is examined. Features of its generated arc are investigated.

  6. Back-Pressure Regulator for Large Gas Flows

    NASA Technical Reports Server (NTRS)

    Theodore, E. A.; Chin, F.

    1985-01-01

    Cost reduced, and safety enhanced. Pipe exit partially obstructed by conical throat plug. When pressure in pipe falls below (or rises above) desired back pressure, plug automatically moved in (or out). Applications of system lie in environmental testing or production facilities requiring large gas flows at low pressures.

  7. Pockels-effect cell for gas-flow simulation

    NASA Technical Reports Server (NTRS)

    Weimer, D.

    1982-01-01

    A Pockels effect cell using a 75 cu cm DK*P crystal was developed and used as a gas flow simulator. Index of refraction gradients were produced in the cell by the fringing fields of parallel plate electrodes. Calibration curves for the device were obtained for index of refraction gradients in excess of .00025 m.

  8. Turbulence modeling of gas-solid suspension flows

    NASA Technical Reports Server (NTRS)

    Chen, C. P.

    1988-01-01

    The purpose here is to discuss and review advances in two-phase turbulent modeling techniques and their applications in various gas-solid suspension flow situations. In addition to the turbulence closures, heat transfer effect, particle dispersion and wall effects are partially covered.

  9. Measuring gas flow rates in the Milky Way

    NASA Astrophysics Data System (ADS)

    Wakker, Bart

    2010-09-01

    Gas flows out of and into the Milky Way are a crucial element in its evolution. Supernovae heat gas in the disk and lift it into the halo. Tidal streams and instabilities in the hot Galactic corona result in an inflow of low-metallicity gas. These flows can be observed in the form of the high-velocity clouds {HVCs}. Their location, brightness, distances, ionization structure and metallicities can be used to determine the conditions in the gaseous disk and halo as well as the rate of mass flow corresponding to the different processes. So far, sufficient information to derive an associated mass flow rate is available for just 5 HVCs. We propose to observe 20 AGNs toward most of the other HVC complexes as well as toward a few small clouds, in order to derive a metallicity for almost every HVC complex, which will complement distance measurements that have been or will be obtained in our ongoing program. Combining all the data, we can derive {a} the rate of the circulation of gas between disk and halo, constraining the Galactic supernova rate and {b} the accretion rate of low-metallicity material that feeds star formation over 10 Gyr, which will constrain both models of galactic chemical evolution and models of the conditions in the hot galactic corona.

  10. Effects of argon gas flow rate on laser-welding.

    PubMed

    Takayama, Yasuko; Nomoto, Rie; Nakajima, Hiroyuki; Ohkubo, Chikahiro

    2012-01-01

    The purpose of this study was to evaluate the effects of the rate of argon gas flow on joint strength in the laser-welding of cast metal plates and to measure the porosity. Two cast plates (Ti and Co-Cr alloy) of the same metal were abutted and welded together. The rates of argon gas flow were 0, 5 and 10 L/min for the Co-Cr alloy, and 5 and 10 L/min for the Ti. There was a significant difference in the ratio of porosity according to the rate of argon gas flow in the welded area. Argon shielding had no significant effect on the tensile strength of Co-Cr alloy. The 5 L/min specimens showed greater tensile strength than the 10 L/min specimens for Ti. Laser welding of the Co-Cr alloy was influenced very little by argon shielding. When the rate of argon gas flow was high, joint strength decreased for Ti. PMID:22447067

  11. 40 CFR 89.416 - Raw exhaust gas flow.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... procedure has been incorporated by reference. See § 89.6.) and calculation of the exhaust gas flow as follows: GEXHW = GAIRW + GFUEL(for wet exhaust mass) or VEXHD = VAIRD + (−.767) × GFUEL(for dry exhaust volume) or VEXHW = VAIRW + .749 × GFUEL(for wet exhaust volume) (b) Exhaust mass calculation from...

  12. 40 CFR 89.416 - Raw exhaust gas flow.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... procedure has been incorporated by reference. See § 89.6.) and calculation of the exhaust gas flow as follows: GEXHW = GAIRW + GFUEL(for wet exhaust mass) or VEXHD = VAIRD + (−.767) × GFUEL(for dry exhaust volume) or VEXHW = VAIRW + .749 × GFUEL(for wet exhaust volume) (b) Exhaust mass calculation from...

  13. Composition and crystal structure of N doped TiO2 film deposited at different O2 flow rate by direct current sputtering.

    PubMed

    Ding, Wanyu; Ju, Dongying; Chai, Weiping

    2011-06-01

    N doped Ti02 films were deposited by direct current pulse magnetron sputtering system at room temperature. The influence of 02 flow rate on the crystal structure of deposited films was studied by Stylus profilometer, X-ray photoelectron spectroscopy, and X-ray diffractometer. The results indicate that the 02 flow rate strongly controls the growth behavior and crystal structure of N doped Ti02 film. It is found that N element mainly exists as substitutional doped state and the chemical stiochiometry is near to TiO1.68±0.06N0.11±0.01 for all film samples. N doped Ti02 film deposited with 2 sccm (standard-state cubic centimeter per minute) 02 flow rate is amorphous structure with high growth rate, which contains both anatase phase and rutile phase crystal nucleuses. In this case, the film displays the mix-phase of anatase and rutile after annealing treatment. While N doped Ti02 film deposited with 12 cm(3)/min 02 flow rate displays anatase phase before and after annealing treatment. And it should be noticed that no TiN phase appears for all samples before and after annealing treatment. PMID:25084571

  14. Influence of the sputtering flow regime on the structural properties and magnetic behavior of Fe-Ga thin films (Ga ˜ 30 at.%)

    NASA Astrophysics Data System (ADS)

    Muñoz-Noval, A.; Ordóñez-Fontes, A.; Ranchal, R.

    2016-06-01

    In this paper we analyze the structure of Fe-Ga layers with a Ga content of ˜30 at.% deposited by the sputtering technique under two different regimes. We also studied the correlation between the structure and magnetic behavior of the samples. Keeping the Ar pressure fixed, we modified the flow regime from ballistic to diffusive by increasing the distance between the target and the substrate. X-ray diffraction measurements have shown a lower structural quality when growing in the diffusive flow. We investigated the impact of the growth regime by means of x-ray absorption fine structure (XAFS) measurements and obtained signs of its influence on the local atomic order. Full multiple scattering and finite difference calculations based on XAFS measurements point to a more relevant presence of a disordered A 2 phase and of orthorhombic Ga clusters on the Fe-Ga alloy deposited under a diffusive regime; however, in the ballistic sample, a higher presence of D 03/B 2 phases is evidenced. Structural characteristics, from local to long range, seem to determine the magnetic behavior of the layers. Whereas a clear in-plane magnetic anisotropy is observed in the film deposited under ballistic flow, the diffusive sample is magnetically isotropic. Therefore, our experimental results provide evidence of a correlation between flow regime and structural properties and its impact on the magnetic behavior of a rather unexplored compositional region of Fe-Ga compounds.

  15. Numerical simulations of high Knudsen number gas flows and microchannel electrokinetic liquid flows

    NASA Astrophysics Data System (ADS)

    Yan, Fang

    Low pressure and microchannel gas flows are characterized by high Knudsen numbers. Liquid flows in microchannels are characterized by non-conventional driving potentials like electrokinetic forces. The main thrust of the dissertation is to investigate these two different kinds of flows in gases and liquids respectively. High Knudsen number (Kn) gas flows were characterized by 'rarified' or 'microscale' behavior. Because of significant non-continuum effect, traditional CFD techniques are often inaccurate for analyzing high Kn number gas flows. The direct simulation Monte Carlo (DSMC) method offers an alternative to traditional CFD which retains its validity in slip and transition flow regimes. To validate the DSMC code, comparisons of simulation results with theoretical analysis and experimental data are made. The DSMC method was first applied to compute low pressure, high Kn flow fields in partially heated two dimensional channels. The effects of varying pressure, inlet flow and gas transport properties (Kn, Reynolds number, Re and the Prandtl number, Pr respectively) on the wall heat transfer (Nusselt number, Nu) were examined. The DSMC method was employed to explore mixing gas flows in two dimensional microchannels. Mixing of two gas streams (H2 and O2) was considered within a microchannel. The effect of the inlet-outlet pressure difference, the pressure ratio of the incoming streams and the accommodation coefficient of the solid wall on mixing length were all examined. Parallelization of a three-dimensional DSMC code was implemented using OpenMP procedure on a shared memory multi-processor computer. The parallel code was used to simulate 3D high Kn number Couette flow and the flow characteristics are found to be very different from their continuum counterparts. A mathematical model describing electrokinetically driven mass transport phenomena in microfabricated chip devices will also be presented. The model accounts for the principal physical phenomena affecting

  16. In Situ Control of Gas Flow by Modification of Gas-Solid Interactions

    NASA Astrophysics Data System (ADS)

    Seo, Dongjin; Ducker, William A.

    2013-10-01

    The boundary condition for gas flow at the solid-gas interface can be altered by in situ control of the state of a thin film adsorbed to the solid. A monolayer of ocatadecyltrichlorosilane (OTS) reversibly undergoes a meltinglike transition. When the temperature of an OTS-coated particle and plate is moved through the range of OTS “melting” temperatures, there is a change in the lubrication force between the particle and plate in 1 atm of nitrogen gas. This change is interpreted in terms of a change in the flow of gas mediated by the slip length and tangential momentum accommodation coefficient (TMAC). There is a minimum in slip length (290 nm) at 18°C, which corresponds to a maximum in TMAC (0.44). The slip length increases to 590 nm at 40°C which corresponds to a TMAC of 0.25. We attribute the decrease in TMAC with increasing temperature to a decrease in roughness of the monolayer on melting, which allows a higher fraction of specular gas reflections, thereby conserving tangential gas momentum. The importance of this work is that it demonstrates the ability to control gas flow simply by altering the interface for fixed geometry and gas properties.

  17. A Mathematical Model of Coupled Gas Flow and Coal Deformation with Gas Diffusion and Klinkenberg Effects

    NASA Astrophysics Data System (ADS)

    Liu, Qingquan; Cheng, Yuanping; Zhou, Hongxing; Guo, Pinkun; An, Fenghua; Chen, Haidong

    2015-05-01

    The influence of gas diffusion behavior on gas flow and permeability evolution in coal seams is evaluated in this paper. Coalbed methane (CBM) reservoirs differ from conventional porous media and fractured gas reservoirs due to certain unique features, which lead to two distinct gas pressures: one in fractures and the other in the coal matrix. The latter pressure, also known as the sorption pressure, will be used in calculating sorption-based volume changes. The effective stress laws for single-porosity media is not suitable for CBM reservoirs, and the effective stress laws for multi-porosity media need to be applied. The realization of the above two points is based on the study of the two-phase state of gas migration (involving Fickian diffusion and Darcy flow) in a coal seam. Then, a general porosity and permeability model based on the P-M model is proposed to fit this phenomenon. Moreover, the Klinkenberg effect has been taken into account and set as a reference object. Finally, a coupled gas flow and coal deformation model is proposed and solved by using a finite element method. The numerical results indicate that the effects of gas diffusion behavior and Klinkenberg behavior can have a critical influence on the gas pressure, residual gas content, and permeability evolution during the entire methane degasification period, and the impacts of the two effects are of the same order of magnitude. Without considering the gas diffusion effect, the gas pressure and residual gas content will be underestimated, and the permeability will be overestimated.

  18. Fabrication of a gas flow device consisting of micro-jet pump and flow sensor

    NASA Astrophysics Data System (ADS)

    Tanaka, Katsuhiko; Dau, Van T.; Otake, Tomonori; Dinh, Thien X.; Sugiyama, Susumu

    2008-12-01

    A gas-flow device consisting of a valveless micro jet pump and flow sensor has been designed and fabricated using a Si micromachining process. The valveless micro pump is composed of a piezoelectric lead zirconate titanate (PZT) diaphragm actuator and flow channels. The design of the valvless pump focuses on a crosss junction formed by the neck of the pump chamber and one outlet and two opposite inlet channnels. The structure allows differences in the fluidic resistance and fluidic momentum inside the channels during each pump vibration cycle, which leads to the gas flow being rectified without valves. Before the Si micro-pump was developed, a prototype of it was fabricated using polymethyl methacrylate (PMMA) and a conventional machining techinique, and experiments on it confirmed the working principles underlying the pump. The Si micro-pump was designed and fabricated based on these working principles. The Si pump was composed of a Si flow channel plate and top and botom covers of PMMA. The flow channels were easily fabricated by using a silicon etching process. To investigate the effects of the step nozzle structure on the gas flow rate, two types of pumps with different channel depths (2D- and 3D-nozzle structures) were designed, and flow simulations were done using ANSYS-Fluent software. The simulations and excperimental data revealed that the 3D-nozzle structure is more advantageous than the 2D-nozzle structure. A flow rate of 4.3 ml/min was obtained for the pump with 3D-nozzle structure when the pump was driven at a resonant frequency of 7.9 kHz by a sinusoidal voltage of 40Vpp. A hot wire was fabricated as a gas-flow sensor near the outlet port on the Si wafer.

  19. Modeling of two-layer liquid-gas flow with account for evaporation

    NASA Astrophysics Data System (ADS)

    Goncharova, O. N.; Rezanova, E. V.; Lyulin, Yu. V.; Kabov, O. A.

    2015-09-01

    Two-layer gas-liquid flows and evaporation intensity at the interface were studied. The influence of gas flow rate, longitudinal gradient of temperature, the Soret effect on the nature of flow and transfer processes was demonstrated. Experimental and theoretical results were compared; they show dependence of evaporation at the interface on gas flow rates.

  20. Transport of sputtered neutral particles

    SciTech Connect

    Parker, G.J.; Hitchon, W.N.G.; Koch, D.J. ||

    1995-04-01

    The initial deposition rate of sputtered material along the walls of a trench is calculated numerically. The numerical scheme is a nonstatistical description of long-mean-free-path transport in the gas phase. Gas-phase collisions are included by using a ``transition matrix`` to describe the particle motion, which in the present work is from the source through a cylindrical chamber and into a rectangular trench. The method is much faster and somewhat more accurate than Monte Carlo methods. Initial deposition rates of sputtered material along the walls of the trench are presented for various physical and geometrical situations, and the deposition rates are compared to other computational and experimental results.

  1. Analytical and Numerical Modeling of Strongly Rotating Rarefied Gas Flows

    NASA Astrophysics Data System (ADS)

    Pradhan, Sahadev; Kumaran, Viswanathan

    2015-11-01

    Centrifugal gas separation processes effect separation by utilizing the difference in the mole fraction in a high speed rotating cylinder caused by the difference in molecular mass, and consequently the centrifugal force density. These have been widely used in isotope separation because chemical separation methods cannot be used to separate isotopes of the same chemical species. More recently, centrifugal separation has also been explored for the separation of gases such as carbon dioxide and methane. The efficiency of separation is critically dependent on the secondary flow generated due to temperature gradients at the cylinder wall or due to inserts, and it is important to formulate accurate models for this secondary flow. The widely used Onsager model for secondary flow is restricted to very long cylinders where the length is large compared to the diameter, the limit of high stratification parameter, where the gas is restricted to a thin layer near the wall of the cylinder, and it assumes that there is no mass difference in the two species while calculating the secondary flow. There are two objectives of the present analysis of the rarefied gas flow in a rotating cylinder. The first is to remove the restriction of high stratification parameter, and to generalize the solutions to low rotation speeds where the stratification parameter may be O(1), and to apply for dissimilar gases considering the difference in molecular mass of the two species. Secondly, we would like to compare the predictions with molecular simulations based on the direct simulation Monte Carlo (DSMC) method for rarefied gas flows, in order to quantify the errors resulting from the approximations at different aspect ratios, Reynolds number and stratification parameter.

  2. Indium-tin oxide thin films deposited at room temperature on glass and PET substrates: Optical and electrical properties variation with the H2-Ar sputtering gas mixture

    NASA Astrophysics Data System (ADS)

    Álvarez-Fraga, L.; Jiménez-Villacorta, F.; Sánchez-Marcos, J.; de Andrés, A.; Prieto, C.

    2015-07-01

    The optical and electrical properties of indium tin oxide (ITO) films deposited at room temperature on glass and polyethylene terephthalate (PET) substrates were investigated. A clear evolution of optical transparency and sheet resistance with the content of H2 in the gas mixture of H2 and Ar during magnetron sputtering deposition is observed. An optimized performance of the transparent conductive properties ITO films on PET was achieved for samples prepared using H2/(Ar + H2) ratio in the range of 0.3-0.6%. Moreover, flexible ITO-PET samples show a better transparent conductive figure of merit, ΦTC = T10/RS, than their glass counterparts. These results provide valuable insight into the room temperature fabrication and development of transparent conductive ITO-based flexible devices.

  3. REACTIVE SPUTTER DEPOSITION OF CHROMIUM NITRIDE COATINGS

    EPA Science Inventory

    The effect of substrate temperature and sputtering gas compositon on the structure and properties of chromium-chromium nitride films deposited on C-1040 steel using r.f. magnetron sputter deposition was investigated. X-ray diffraction analysis was used to determine the structure ...

  4. Flow modulation comprehensive two-dimensional gas chromatography-mass spectrometry using ≈4mLmin(-1) gas flows.

    PubMed

    Franchina, Flavio A; Maimone, Mariarosa; Tranchida, Peter Q; Mondello, Luigi

    2016-04-01

    The main objective of the herein described research was focused on performing satisfactory flow modulation (FM), in comprehensive two-dimensional gas chromatography-mass spectrometry (GC×GC-MS), using an MS-compatible second-dimension gas flow of approx. 4mLmin(-1). The FM model used was based on that initially proposed by Seeley et al. [3]. The use of limited gas flows was enabled through fine tuning of the FM parameters, in particular the duration of the re-injection (or flushing) process. Specifically, the application of a long re-injection period (i.e., 700ms) enabled efficient accumulation-loop flushing with gas flows of about 4mLmin(-1). It was possible to apply such extended re-injection periods by using different restrictor lengths in the connections linking the modulator to the auxiliary pressure source. FM GC×GC-MS applications were performed on a mixture containing C9-10 alkanes, and on a sample of essential oil. GC×GC-MS sensitivity was compared with that attained by using conventional GC-MS analysis, in essential oil applications. It was observed that signal intensities were, in general, considerably higher in the FM GC×GC-MS experiments. PMID:26968229

  5. Flow field simulation of gas-water two phase flow in annular channel

    NASA Astrophysics Data System (ADS)

    Ji, Pengcheng; Dong, Feng

    2014-04-01

    The gas-water two-phase flow is very common in the industrial processes. the deep understanding of the two-phase flow state is to achieve the production equipment design and safe operation. In the measurement of gas-water two-phase flow, the differential pressure sensor is widely used, and some measurement model of multiphase flow have been concluded. The differential pressure is generated when fluid flowing through the throttling components to calculate flow rate. This paper mainly focuses on two points: 1. The change rule of the parameters include velocity, pressure, phase fraction as the change of time, when the phase inlet velocity is given. 2. Analysis the distribution of the parameters above-mentioned at a certain moment under the condition of different water inlet velocity. Three-dimensional computational fluid dynamics (CFD) approach was used to simulate gas-water two-phase flow fluid in the annular channel, which is composed of horizontal pipe and long- waist cone sensor. The simulation results were obtained from FLUENT software.

  6. Droplet breakup in accelerating gas flows. Part 2: Secondary atomization

    NASA Technical Reports Server (NTRS)

    Zajac, L. J.

    1973-01-01

    An experimental investigation to determine the effects of an accelerating gas flow on the atomization characteristics of liquid sprays was conducted. The sprays were produced by impinging two liquid jets. The liquid was molten wax and the gas was nitrogen. The use of molten wax allowed for a quantitative measure of the resulting dropsize distribution. The results of this study, indicate that a significant amount of droplet breakup will occur as a result of the action of the gas on the liquid droplets. Empirical correlations are presented in terms of parameters that were found to affect the mass median dropsize most significantly, the orifice diameter, the liquid injection velocity, and the maximum gas velocity. An empirical correlation for the normalized dropsize distribution is also presented. These correlations are in a form that may be incorporated readily into existing combustion model computer codes for the purpose of calculating rocket engine combustion performance.

  7. Parallel magnetic resonance imaging of gas-liquid flows

    NASA Astrophysics Data System (ADS)

    Mueller, Christoph; Penn, Alexander; Pruessmann, Klaas P.

    2015-03-01

    Gas-liquids flows are commonly encountered in nature and industry. Experimental measurements of gas-liquid flows are challenging since such systems can be visually opaque and highly dynamic. Here we report the implementation of advanced magnetic resonance imaging (MRI) strategies allowing us to probe the dynamics (voidage and velocity measurements) of gas-liquid flows with ultra-fast acquisition speeds. Specifically, parallel MRI which exploits the spatial encoding capabilities of multiple receiver coils was implemented. To this end a tailored, 16 channels MR receive array was constructed and employed in the MR acquisition. A magnetic susceptibility matched gas-liquid system was set-up and used to probe the motion, splitting and coalescence of bubbles. The temporal and spatial resolution of our acquired data was 5 ms and 3.5 mm x 3.5 mm, respectively. The total field of view was 200 mm x 200 mm. We will conclude with an outlook of further possible advances in MRI that have the potential to reduce substantially the acquisition time, providing flexible gains in temporal and spatial resolution.

  8. Incorporation of Interstitial Gas Effects on Granular Flows

    NASA Astrophysics Data System (ADS)

    Hrenya, Christine; Garzo, Vicente; Tenneti, Sudheer; Subramaniam, Shankar

    2013-11-01

    Numerous examples of granular flows exist in which the role of the interstitial gas cannot be ignored. A range of approaches have been taken to incorporate these effects into continuum descriptions. Early efforts simply added a mean drag law to the momentum balance. This ad hoc approach was followed by more rigorous treatments in which an instantaneous drag was incorporated directly into the kinetic equation. Analytical expressions for the resulting continuum description were obtained in the Stokes limit, but not possible higher Reynolds numbers. In the current effort, DNS-based simulations are used to develop a model for the instantaneous drag force that is applicable to a wide range of Reynolds number. This model, based on the Langevin equation, is incorporated into the Enskog equation in order to derive a continuum description for the gas-solid flow. In the limit of Stokes flow, the additional terms arising in the conservation equation are found to match those of previous analytical treatments. Furthermore, the impact of gas on the solid-phase constitutive relations, which was ignored in analytical treatments, is determined. The parameter space examined is consistent with that found in circulating fluidized beds. For such systems, the results indicate a non-negligible impact of the gas phase on the shear viscosity and the Dufour coefficient.

  9. Going with the flow: using gas clouds to probe the accretion flow feeding Sgr A*

    NASA Astrophysics Data System (ADS)

    McCourt, Michael; Madigan, Ann-Marie

    2016-01-01

    The massive black hole in our Galactic centre, Sgr A*, accretes only a small fraction of the gas available at its Bondi radius. The physical processes determining this accretion rate remain unknown, partly due to a lack of observational constraints on the gas at distances between ˜10 and ˜105 Schwarzschild radii (Rs) from the black hole. Recent infrared observations identify low-mass gas clouds, G1 and G2, moving on highly eccentric, nearly co-planar orbits through the accretion flow around Sgr A*. Although it is not yet clear whether these objects contain embedded stars, their extended gaseous envelopes evolve independently as gas clouds. In this paper we attempt to use these gas clouds to constrain the properties of the accretion flow at ˜103 Rs. Assuming that G1 and G2 follow the same trajectory, we model the small differences in their orbital parameters as evolution resulting from interaction with the background flow. We find evolution consistent with the G-clouds originating in the clockwise disc. Our analysis enables the first unique determination of the rotation axis of the accretion flow: we localize the rotation axis to within 20°, finding an orientation consistent with the parsec-scale jet identified in X-ray observations and with the circumnuclear disc, a massive torus of molecular gas ˜1.5 pc from Sgr A*. This suggests that the gas in the accretion flow comes predominantly from the circumnuclear disc, rather than the winds of stars in the young clockwise disc. This result will be tested by the Event-Horizon Telescope within the next year. Our model also makes testable predictions for the orbital evolution of G1 and G2, falsifiable on a 5-10 year time-scale.

  10. Heat transfer and flow characteristics on a gas turbine shroud.

    PubMed

    Obata, M; Kumada, M; Ijichi, N

    2001-05-01

    The work described in this paper is an experimental investigation of the heat transfer from the main flow to a turbine shroud surface, which may be applicable to ceramic gas turbines. Three kinds of turbine shrouds are considered with a flat surface, a taper surface and a spiral groove surface opposite to the blades in an axial flow turbine of actual turbo-charger. Heat transfer measurements were performed for the experimental conditions of a uniform heat flux or a uniform wall temperature. The effects of the inlet flow angle, rotational speed, and tip clearance on the heat transfer coefficient were clarified under on- and off-design flow conditions. The mean heat transfer coefficient was correlated to the blade Reynolds number and tip clearance, and compared with an experimental correlation and measurements of a flat surface. A comparison was also made for the measurement of static pressure distributions. PMID:11460639

  11. Flow and heat transfer for gas flowing in microchannels: a review

    NASA Astrophysics Data System (ADS)

    Rostami, A. A.; Mujumdar, A. S.; Saniei, N.

    Microchannels are currently being used in many areas and have high potential for applications in many other areas, which are considered realistic by experts. The application areas include medicine, biotechnology, avionics, consumer electronics, telecommunications, metrology, computer technology, office equipment and home appliances, safety technology, process engineering, robotics, automotive engineering and environmental protection. A number of these applications are introduced in this paper, followed by a critical review of the works on the flow and heat transfer for gas flowing in microchannels. The results show that the flow and heat transfer characteristics of a gas flowing in microchannels can not be adequately predicted by the theories and correlations developed for conventional sized channels. The results of theoretical and experimental works are discussed and summarized along with suggestions for future research directions.

  12. Effect of substrate temperature and gas flow ratio on the nanocomposite TiAlBN coating

    NASA Astrophysics Data System (ADS)

    Rosli, Z. M.; Kwan, W. L.; Juoi, J. M.

    2016-07-01

    Nanocomposite TiAlBN (nc-TiAlBN) coatings were successfully deposited via RF magnetron sputtering by varying the nitrogen-to-total gas flow ratio (RN), and substrate temperature (TS). All coatings were deposited on AISI 316 substrates using single Ti-Al-BN hot-pressed disc as a target. The grain size, phases, and chemical composition of the coatings were evaluated using glancing angle X-ray diffraction analysis (GAXRD) and X-ray photoelectron spectroscopy (XPS). Results showed that the grains size of the deposited nc-TiAlBN coatings were in the range of 3.5 to 5.7 nm and reached a nitride saturation state as early as 15 % RN. As the nitrogen concentration decreases, boron concentration increased from 9 at.% to 16.17 at.%. and thus, increase the TiB2 phase within the coatings. The TS, however, showed no significant effect either on the crystallographic structure, grain size, or in the chemical composition of the deposited nc-TiAlBN coating.

  13. Dual exposure interferometry. [gas dynamics and flow visualization

    NASA Technical Reports Server (NTRS)

    Smeets, G.; George, A.

    1982-01-01

    The application of dual exposure differential interferometry to gas dynamics and flow visualization is discussed. A differential interferometer with Wallaston prisms can produce two complementary interference fringe systems, depending on the polarization of the incident light. If these two systems are superimposed on a film, with one exposure during a phenomenon, the other before or after, the phenomenon will appear on a uniform background. By regulating the interferometer to infinite fringe distance, a resolution limit of approximately lambda/500 can be obtained in the quantitative analysis of weak phase objects. This method was successfully applied to gas dynamic investigations.

  14. Effects of oxygen gas pressure on structural, electrical, and thermoelectric properties of (ZnO){sub 3}In{sub 2}O{sub 3} thin films deposited by rf magnetron sputtering

    SciTech Connect

    Orikasa, Yuki; Hayashi, Naoaki; Muranaka, Shigetoshi

    2008-06-01

    Zinc indium oxide films were deposited by the rf magnetron sputtering method using a (ZnO){sub 3}In{sub 2}O{sub 3} target. The films were prepared at 573 K in various Ar/O{sub 2} sputtering gases (O{sub 2} content: 0%-25%). The effect of the oxygen gas content in the sputtering gas on the structural, optical, electrical, and thermoelectric properties of the films was investigated. The films had a c-axis oriented layer structure. The films deposited at 0%-3% oxygen gas contents exhibited a high electrical conductivity with a high carrier concentration, n{approx_equal}10{sup 20} cm{sup -3}, while the conductivity of the films significantly decreased above the 3% oxygen gas content, having a carrier concentration below 10{sup 18} cm{sup -3}. From the optical transmission measurement, the band gap of the films was estimated to be 3.01 eV. The films deposited at 3%-8% oxygen gas contents showed a high Seebeck coefficient, -300 {mu}V/K, while the maximum power factor, 4.78x10{sup -5} W/m K{sup 2}, was obtained at the 2% oxygen gas content. The Seebeck coefficient and the power factor were calculated on the basis of degenerate semiconductors. These results suggest that zinc indium oxide films have the possibility of being high performance thermoelectric materials.

  15. Visualization and velocity measurement of unsteady flow in a gas generator using cold-flow technique

    NASA Astrophysics Data System (ADS)

    Kuppa, Subrahmanyam

    1990-08-01

    Modeling of internal flow fields with hot, compressible fluids and sometimes combustion using cold flow techniques is discussed. The flow in a gas generator was modeled using cold air. The experimental set up was designed and fabricated to simulate the unsteady flow with different configurations of inlet tubes. Tests were run for flow visualization and measurement of axial velocity at different frequencies ranging from 5 to 12 Hz. Flow visualization showed that the incoming flow was a complex jet flow confined to a cylindrical enclosure, while the outgoing flow resembled the venting of a pressurized vessel. The pictures show a complex flow pattern due to the angling of the jet towards the wall for the bent tube configurations and straightened flows with straight tube and other configurations with straighteners. Velocity measurements were made at an inlet Re of 8.1 x 10(exp 4) based on maximum velocity and inlet diameter. Phase averaged mean velocities were observed to be well defined during charging and diminished during venting inside the cylinder. For the straight tube inlet comparison with a steady flow measurement of sudden expansion flow showed a qualitative similarity of the mean axial velocity distribution and centerline velocity decay during the charging phases. For the bent tube inlet case the contour plots showed the flow tendency towards the wall. Two cells were seen in the contours for the 8 and 12 Hz cases. The deviation of the point of occurrence of maximum velocity in a radial profile was found to be about 6.5 degrees. Entrance velocity profiles showed symmetry for the straight tube inlet but were skewed for the bent tube inlet. Contour plots of the phase averaged axial turbulence intensity for bent tube cases showed higher values in the core and near the wall in the region of impingement. Axial turbulence intensity measured for the straight tube case showed features as observed in an axisymmetric sudden expansion flow.

  16. Nonequilibrium condensation in high-speed gas flows

    SciTech Connect

    Ryzhov, Y.A.; Pirumov, U.G.; Gorbunov, V.N. )

    1989-01-01

    Nonequilibrium condensation is an important aspect of weather forecasting, aerosol formation, and the design of jet propulsion engines, steam turbines and nuclear reactors. It has recently taken on a new significance with the development of technologies such as the production of fine powders, cluster spraying, the development of laser media and isotope separation. This book discusses the general theory of condensation in high speed gas flows, and the new theoretical, experimental and numerical methods necessary for solving the partial differential equations governing the flows.

  17. Visualization of unsteady gas/vapor expansion flows

    NASA Astrophysics Data System (ADS)

    Schnerr, G. H.; Adam, S.

    1997-09-01

    High speed expansion flows of pure vapors or gas/vapor mixtures are important to many technical applications, e.g. to steam turbines, jet engines, and for safety control of pressurized power plants. The sudden cooling of the fluid flow leads to condensation and nonequilibrium two-phase flow with instabilities and periodic shock formation at mean frequencies of about 1 kHz. Modelling and control of this dynamical problem is not only important with respect to erosion, it also may cause flutter excitation and serious demolition of technical facilities. In numerical simulations, the time dependent 2-D Euler equations coupled to four equations describing the process of homogeneous nucleation and droplet growth are solved by a MUSCL-type finite volume method. The results are compared with experiments carried out in an atmospheric supersonic wind tunnel. By application of this numerical method to internal flows (nozzles) we found different modes of instabilities including bifurcations. At the stability limit a sharp frequency minimum was found for symmetric oscillations in slender nozzles. It separates oscillation modes where the oncoming subsonic flow remains unchanged from the oscillatory state where a shock monotonically moves upstream into the oncoming flow. For different nozzles we detected a new unsymmetric oscillation mode with a complex system of upstream moving oblique shocks. Here the frequency curve shows the typical structure of a bifurcation problem, which is definitely not controlled by viscous effects but by instabilities of the interaction of flow and phase transition process.

  18. PREFACE: 1st European Conference on Gas Micro Flows (GasMems 2012)

    NASA Astrophysics Data System (ADS)

    Frijns, Arjan; Valougeorgis, Dimitris; Colin, Stéphane; Baldas, Lucien

    2012-05-01

    The aim of the 1st European Conference on Gas Micro Flows is to advance research in Europe and worldwide in the field of gas micro flows as well as to improve global fundamental knowledge and to enable technological applications. Gas flows in microsystems are of great importance and touch almost every industrial field (e.g. fluidic microactuators for active control of aerodynamic flows, vacuum generators for extracting biological samples, mass flow and temperature micro-sensors, pressure gauges, micro heat-exchangers for the cooling of electronic components or for chemical applications, and micro gas analyzers or separators). The main characteristic of gas microflows is their rarefaction, which for device design often requires modelling and simulation both by continuous and molecular approaches. In such flows various non-equilibrium transport phenomena appear, while the role played by the interaction between the gas and the solid device surfaces becomes essential. The proposed models of boundary conditions often need an empirical adjustment strongly dependent on the micro manufacturing technique. The 1st European Conference on Gas Micro Flows is organized under the umbrella of the recently established GASMEMS network (www.gasmems.eu/) consisting of 13 participants and six associate members. The main objectives of the network are to structure research and train researchers in the fields of micro gas dynamics, measurement techniques for gaseous flows in micro experimental setups, microstructure design and micro manufacturing with applications in lab and industry. The conference takes place on June 6-8 2012, at the Skiathos Palace Hotel, on the beautiful island of Skiathos, Greece. The conference has received funding from the European Community's Seventh Framework Programme FP7/2007-2013 under grant agreement ITN GASMEMS no. 215504. It owes its success to many people. We would like to acknowledge the support of all members of the Scientific Committee and of all

  19. Gaseous sodium sulfate formation in flames and flowing gas environments

    NASA Technical Reports Server (NTRS)

    Stearns, C. A.; Miller, R. A.; Kohl, F. J.; Fryburg, G. C.

    1977-01-01

    Formation of Na2SO4(g) in flames and hot flowing gas systems was studied by high pressure, free-jet expansion, modulated molecular beam mass spectrometric sampling. Fuel-lean CH4-O2 flames doped with SO2, H2O and NaCl yielded the gaseous Na2SO4 molecule in residence times of less than one millisecond. Intermediate species NaSO2(g) and NaSO3(g) were also observed and measured. Composition profiles were obtained for all reaction products. Nonflame flowing gas experiments showed that Na2SO4 and NaSO3 gaseous molecules were formed at 1140 C in mixtures of O2, H2O(g), SO2 and NaCl(g). Experimental results are compared with calculated equilibrium thermodynamic predictions.

  20. Emission control valve with gas flow shut-off

    SciTech Connect

    Betterton, J.T.; Glover, A.H.; McKee, T.S.; Romanczuk, C.S.

    1990-03-06

    This patent describes, in an internal combustion engine, a crankcase gas flow control device located between the engine crankcase and the engine fuel-air induction. It comprises: a hollow housing, an apertured member supported at its outer edge by the housing. The apertured member forming an inlet and having an annular seating surface about the inlet aperture which faces the interior of the housing; a rod extending through the housing coaxially with the apertured inlet. The inlet forming member has a central boss portion engaging and supporting an end of the rod; a valve element in the housing and encircling the rod, the valve having a closed end normally seated against the seating surface to block gas flow through the inlet aperture; a coil type spring having one end axially fixed to the rod and another end engaging the valve element for yieldably urging the closed end against the seating surface.

  1. Fine-tuning control on CNT diameter distribution, length and density using thermal CVD growth at atmospheric pressure: an in-depth analysis on the role of flow rate and flow duration of acetylene (C2H2) gas

    NASA Astrophysics Data System (ADS)

    Tripathi, Nishant; Mishra, Prabhash; Harsh, Harsh; Islam, S. S.

    2015-01-01

    An optimization control has been demonstrated to obtain carbon nanotubes having specific diameter distribution, length, homogeneity, and yield during its growth by thermal chemical vapor deposition technique under atmospheric pressure. Carbon nanotubes (CNTs) were grown on silicon wafer where a predeposition of iron catalyst of 2 nm thickness was made by sputtering. The growth was conducted under two variable parameters, i.e., flow rate and flow duration. Argon and hydrogen mixture was used for pretreatment of catalyst and as etching gas, and acetylene as a carbon precursor. In-depth analysis shows that increase in flow rate from 10 to 50 sccm resulted in increase in the concentration of amorphous carbon, CNTs diameter range and decrease in length, we found best result at 20 sccm flow rate of acetylene gas. On the other hand, as we varied flow duration from 6 to 14 min, with keeping flow rate of acetylene 20 sccm constant, dense homogeneous growth of horizontal CNTs network plus an increase in length and diameter range were observed. An optimization of flow rate and flow duration is presented here to obtain a selective diameter distribution and length as expected by this growth technique. Atomic force microscopy, field emission scanning electron microscopy and Raman spectroscopy were used to investigate the samples' morphologies in support of the observations made.

  2. Flow Analysis of a Gas Turbine Low- Pressure Subsystem

    NASA Technical Reports Server (NTRS)

    Veres, Joseph P.

    1997-01-01

    The NASA Lewis Research Center is coordinating a project to numerically simulate aerodynamic flow in the complete low-pressure subsystem (LPS) of a gas turbine engine. The numerical model solves the three-dimensional Navier-Stokes flow equations through all components within the low-pressure subsystem as well as the external flow around the engine nacelle. The Advanced Ducted Propfan Analysis Code (ADPAC), which is being developed jointly by Allison Engine Company and NASA, is the Navier-Stokes flow code being used for LPS simulation. The majority of the LPS project is being done under a NASA Lewis contract with Allison. Other contributors to the project are NYMA and the University of Toledo. For this project, the Energy Efficient Engine designed by GE Aircraft Engines is being modeled. This engine includes a low-pressure system and a high-pressure system. An inlet, a fan, a booster stage, a bypass duct, a lobed mixer, a low-pressure turbine, and a jet nozzle comprise the low-pressure subsystem within this engine. The tightly coupled flow analysis evaluates aerodynamic interactions between all components of the LPS. The high-pressure core engine of this engine is simulated with a one-dimensional thermodynamic cycle code in order to provide boundary conditions to the detailed LPS model. This core engine consists of a high-pressure compressor, a combustor, and a high-pressure turbine. The three-dimensional LPS flow model is coupled to the one-dimensional core engine model to provide a "hybrid" flow model of the complete gas turbine Energy Efficient Engine. The resulting hybrid engine model evaluates the detailed interaction between the LPS components at design and off-design engine operating conditions while considering the lumped-parameter performance of the core engine.

  3. Theory of Gas Injection: Interaction of Phase Behavior and Flow

    NASA Astrophysics Data System (ADS)

    Dindoruk, B.

    2015-12-01

    The theory of gas injection processes is a central element required to understand how components move and partition in the reservoir as one fluid is displacing another (i.e., gas is displacing oil). There is significant amount of work done in the area of interaction of phase-behavior and flow in multiphase flow conditions. We would like to present how the theory of gas injection is used in the industry to understand/design reservoir processes in various ways. The tools that are developed for the theory of gas injection originates from the fractional flow theory, as the first solution proposed by Buckley-Leveret in 1940's, for water displacing oil in porous media. After 1960's more and more complex/coupled equations were solved using the initial concept(s) developed by Buckley-Leverett, and then Welge et al. and others. However, the systematic use of the fractional flow theory for coupled set of equations that involves phase relationships (EOS) and phase appearance and disappearance was mainly due to the theory developed by Helfferich in early 80's (in petroleum literature) using method of characteristics primarily for gas injection process and later on by the systematic work done by Orr and his co-researchers during the last two decades. In this talk, we will present various cases that use and extend the theory developed by Helfferich and others (Orr et al., Lake et al. etc.). The review of various injection systems reveals that displacement in porous media has commonalities that can be represented with a unified theory for a class of problems originating from the theory of gas injection (which is in a way generalized Buckley-Leverett problem). The outcome of these solutions can be used for (and are not limited to): 1) Benchmark solutions for reservoir simulators (to quantify numerical dispersion, test numerical algorithms) 2) Streamline simulators 3) Design of laboratory experiments and their use (to invert the results) 4) Conceptual learning and to investigate

  4. One-dimensional flows of an imperfect diatomic gas

    NASA Technical Reports Server (NTRS)

    1959-01-01

    With the assumptions that Berthelot's equation of state accounts for molecular size and intermolecular force effects, and that changes in the vibrational heat capacities are given by a Planck term, expressions are developed for analyzing one-dimensional flows of a diatomic gas. The special cases of flow through normal and oblique shocks in free air at sea level are investigated. It is found that up to a Mach number 10 pressure ratio across a normal shock differs by less than 6 percent from its ideal gas value; whereas at Mach numbers above 4 the temperature rise is considerable below and hence the density rise is well above that predicted assuming ideal gas behavior. It is further shown that only the caloric imperfection in air has an appreciable effect on the pressures developed in the shock process considered. The effects of gaseous imperfections on oblique shock-flows are studied from the standpoint of their influence on the life and pressure drag of a flat plate operating at Mach numbers of 10 and 20. The influence is found to be small. (author)

  5. Compression Shocks in Two-Dimensional Gas Flows

    NASA Technical Reports Server (NTRS)

    Busemann, A.

    1949-01-01

    The following are arguments on the compression shocks in gas flow start with a simplified representation of the results of the study made by Th. Meyer as published in the Forschungsheft 62 of the VDI, supplemented by several amplifications for the application.In the treatment of compression shocks, the equation of energy, the equation of continuity, the momentum equation, the equation of state of the particular gas, as well as the condition Of the second law of thermodynamics that no decrease of entropy is possible in an isolated system, must be taken into consideration. The result is that, in those cases where the sudden change of state according to the second law of thermodynamics is possible, there always occurs a compression of the gas which is uniquely determined by the other conditions.

  6. Liquid and liquid–gas flows at all speeds

    SciTech Connect

    LeMartelot, S.; Nkonga, B.; Saurel, R.

    2013-12-15

    All speed flows and in particular low Mach number flow algorithms are addressed for the numerical approximation of the Kapila et al. [1] multiphase flow model. This model is valid for fluid mixtures evolving in mechanical equilibrium but out of temperature equilibrium and is efficient for material interfaces computation separating miscible and non-miscible fluids. In this context, the interface is considered as a numerically diffused zone, captured as well as all present waves (shocks, expansion waves). The same flow model can be used to solve cavitating and boiling flows [2]. Many applications occurring with liquid–gas interfaces and cavitating flows involve a very wide range of Mach number, from 10{sup −3} to supersonic (and even hypersonic) conditions with respect to the mixture sound speed. It is thus important to address numerical methods free of restrictions regarding the Mach number. To do this, a preconditioned Riemann solver is built and embedded into the Godunov explicit scheme. It is shown that this method converges to exact solutions but needs too small time steps to be efficient. An implicit version is then derived, first in one dimension and second in the frame of 2D unstructured meshes. Two-phase flow preconditioning is then addressed in the frame of the Saurel et al. [3] algorithm. Modifications of the preconditioned Riemann solver are needed and detailed. Convergence of both single phase and two-phase numerical solutions are demonstrated with the help of single phase and two-phase steady nozzle flow solutions. Last, the method is illustrated by the computation of real cavitating flows in Venturi nozzles. Vapour pocket size and instability frequencies are reproduced by the model and method without using any adjustable parameter.

  7. Formation of cubic boron-nitride by the reactive sputter deposition of boron

    SciTech Connect

    Jankowski, A.F.; Hayes, J.P.; Makowiecki, D.W.; McKeman, M.A.

    1997-03-01

    Boron-nitride films are synthesized by RF magnetron sputtering boron targets where the deposition parameters of gas pressure, flow and composition are varied along with substrate temperature and applied bias. The films are analyzed using Auger electron spectroscopy, transmission electron microscopy, nanoindentation, Raman spectroscopy and x-ray absorption spectroscopy. These techniques provide characterization of film composition, crystalline structure, hardness and chemical bonding, respectively. Reactive, rf-sputtering process parameters are established which lead to the growth of crystalline BN phases. The deposition of stable and adherent boron nitride coatings consisting of the cubic phase requires 400 `C substrate heating and the application of a 300 V negative bias.

  8. Studies on the room temperature growth of nanoanatase phase TiO{sub 2} thin films by pulsed dc magnetron with oxygen as sputter gas

    SciTech Connect

    Karuppasamy, A.; Subrahmanyam, A.

    2007-03-15

    The anatase phase titanium dioxide (TiO{sub 2}) thin films were deposited at room temperature by pulsed dc magnetron sputtering using pure oxygen as sputter gas. The structural, optical, electrical, and electrochromic properties of the films have been studied as a function of oxygen pressure in the chamber. The x-ray diffraction results indicate that the films grown above 4.5x10{sup -2} mbar are nanocrystalline (grain size of 28-43 nm) with anatase phase. The films deposited at the chamber pressure of 7.2x10{sup -2} mbar are found to be highly crystalline with a direct optical band gap of 3.40 eV, refractive index of 2.54 (at {lambda}=400 nm), and work function of 4.77 eV (determined by the Kelvin probe measurements). From the optical emission spectra of the plasma and transport of ions in matter calculations, we find that the crystallization of TiO{sub 2} at room temperature is due to the impingement of electrons and ions on the growing films. Particularly, the negative oxygen ions reflected from the target by 'negative ion effects' and the enhanced density of TiO, TiO{sup +}, TiO{sub 2}{sup +}, and O{sup 2+} particles in the plasma are found to improve the crystallization even at a relatively low temperature. From an application point of view, the film grown at 7.2x10{sup -2} mbar was studied for its electrochromic properties by protonic intercalation. It showed good electrochromic behavior with an optical modulation of {approx}45%, coloration efficiency of 14.7 cm{sup 2} C{sup -1}, and switching time (t{sub c}) of 50 s for a 2x2 cm{sup 2} device at {lambda}=633 nm.

  9. Magnetron sputtering system for coatings deposition with activation of working gas mixture by low-energy high-current electron beam

    NASA Astrophysics Data System (ADS)

    Gavrilov, N. V.; Kamenetskikh, A. S.; Men'shakov, A. I.; Bureyev, O. A.

    2015-11-01

    For the purposes of efficient decomposition and ionization of the gaseous mixtures in a system for coatings deposition using reactive magnetron sputtering, a low-energy (100-200 eV) high-current electron beam is generated by a grid-stabilized plasma electron source. The electron source utilizes both continuous (up to 20 A) and pulse-periodic mode of discharge with a self-heated hollow cathode (10-100 A; 0.2 ms; 10-1000 Hz). The conditions for initiation and stable burning of the high-current pulse discharge are studied along with the stable generation of a low-energy electron beam within the gas pressure range of 0.01 - 1 Pa. It is shown that the use of the electron beam with controllable parameters results in reduction of the threshold values both for the pressure of gaseous mixture and for the fluxes of molecular gases. Using such a beam also provides a wide range (0.1-10) of the flux density ratios of ions and sputtered atoms over the coating surface, enables an increase in the maximum pulse density of ion current from plasma up to 0.1 A, ensures an excellent adhesion, optimizes the coating structure, and imparts improved properties to the superhard nanocomposite coatings of (Ti,Al)N/a-Si3N4 and TiC/-a-C:H. Mass-spectrometric measurements of the beam-generated plasma composition proved to demonstrate a twofold increase in the average concentration of N+ ions in the Ar-N2 plasma generated by the high-current (100 A) pulsed electron beam, as compared to the dc electron beam.

  10. Study of interfacial behavior in cocurrent gas-liquid flows

    SciTech Connect

    McCready, M.J.

    1990-01-01

    We have examined the mechanism of formation of solitary waves on gas-liquid flows and found, that these form from existing periodic waves which have sufficiently large ({approximately}1.5 to 2 depending upon fluid properties) amplitude to liquid layer-thickness ratios. The exact process for the wave shape change is not understood but it does not seem to be related to the wave steepness (amplitude/wavelength) or to separation of gas flow over the waves. The observed confinement of solitary waves to low liquid Reynolds numbers results because the necessary large precursor waves do not form if the wave speed dispersion is too large or if the wavelength of the dominant waves is too short, as occurs for higher Re{sub L}. Measurements of interface tracings and calculations of power spectra and bispectra as a function of flow distance for conditions close to neutral stability reveal that the initially, linearly unstable mode is stabilized by formation of overtones which are linearly stable and can dissipate energy. As a result, a stable wave field can occur. Mode equations, which include quadratic nonlinearities, can model this process to the extent of producing some degree of quantitative predictions for the amplitudes of the wave modes. However, a complete picture of the wave field must include sidebands as well because these are observed for some flow conditions. 34 refs., 12 figs., 2 tabs.