Showing papers on "Atmospheric pressure published in 2013"
TL;DR: In this paper, the role of different active components of the argon plasma is evaluated based on either measurements, as mentioned above, or estimations based on published data of measurements of those components.
Abstract: A radio-frequency atmospheric pressure argon plasma jet is used for the inactivation of bacteria (Pseudomonas aeruginosa) in solutions. The source is characterized by measurements of power dissipation, gas temperature, absolute UV irradiance as well as mass spectrometry measurements of emitted ions. The plasma-induced liquid chemistry is studied by performing liquid ion chromatography and hydrogen peroxide concentration measurements on treated distilled water samples. Additionally, a quantitative estimation of an extensive liquid chemistry induced by the plasma is made by solution kinetics calculations. The role of the different active components of the plasma is evaluated based on either measurements, as mentioned above, or estimations based on published data of measurements of those components. For the experimental conditions being considered in this work, it is shown that the bactericidal effect can be solely ascribed to plasma-induced liquid chemistry, leading to the production of stable and transient chemical species. It is shown that HNO2, ONOO − and H2O2 are present in the liquid phase in similar quantities to concentrations which are reported in the literature to cause bacterial inactivation. The importance of plasma-induced chemistry at the gas‐liquid interface is illustrated and discussed in detail. (Some figures may appear in colour only in the online journal)
289 citations
TL;DR: In this paper, a zero-dimensional, semi-empirical model is used to describe the plasma chemistry in an argon plasma jet flowing into humid air, mimicking the experimental conditions of a setup from the Eindhoven University of Technology.
Abstract: A zero-dimensional, semi-empirical model is used to describe the plasma chemistry in an argon plasma jet flowing into humid air, mimicking the experimental conditions of a setup from the Eindhoven University of Technology. The model provides species density profiles as a function of the position in the plasma jet device and effluent. A reaction chemistry set for an argon/humid air mixture is developed, which considers 84 different species and 1880 reactions. Additionally, we present a reduced chemistry set, useful for higher level computational models. Calculated species density profiles along the plasma jet are shown and the chemical pathways are explained in detail. It is demonstrated that chemically reactive H, N, O and OH radicals are formed in large quantities after the nozzle exit and H2, O2(1Δg), O3, H2O2, NO2, N2O, HNO2 and HNO3 are predominantly formed as ‘long living’ species. The simulations show that water clustering of positive ions is very important under these conditions. The influence of vibrational excitation on the calculated electron temperature is studied. Finally, the effect of varying gas temperature, flow speed, power density and air humidity on the chemistry is investigated.
249 citations
TL;DR: In this article, a detailed experimental investigation of the mechanism of ultrafast heating and oxygen dissociation produced by nanosecond repetitively pulsed discharges in atmospheric pressure air preheated at 1000 K is presented.
Abstract: A detailed experimental investigation of the mechanism of ultrafast heating and oxygen dissociation produced by nanosecond repetitively pulsed discharges in atmospheric pressure air preheated at 1000 K is presented. The ultrafast mechanism creates excited electronic states of nitrogen, which then dissociate molecular oxygen through quenching reactions, with the remaining energy dissipated as heat. Optical and electrical diagnostic techniques have been applied to provide a self-consistent set of experimental data for a reference test-case with well-defined discharge and gas conditions. The pulses have a duration of 10 ns, an amplitude of 5.7 kV, a repetition frequency of 10 kHz and the pin-to-pin electrodes are separated by 4 mm. We present measurements of the gas temperature during and after the discharge using optical emission spectroscopy of the second positive system of nitrogen, spatially resolved profiles of the absolute densities of excited electronic states, determined using Abel-inverted spectra of the first and second positive systems of nitrogen, as well as the temporal evolution of the absolute densities of N2(A), N2(B), N2(C), electrons and atomic oxygen. These measurements are synchronized with electrical measurements of pulse current, voltage, and energy. The discharge is found to dissociate about 50% of molecular oxygen and to produce a temperature increase of about 900 K within 20 ns, corresponding to an ultrafast heating rate of about 5 × 1010 K s−1. Comparisons with numerical simulations show good agreement with the measurements and validate the ultrafast mechanism. About 35% of the electric energy deposited into the gas goes into O2 dissociation, and about 21% into gas heating. Finally, the dissociative quenching rates of N2(B) and N2(C) with O2 at 2200 K were measured and found to be 2.8(±0.6) × 10−10 cm3 s−1 and 5.8(±0.9) × 10−10 cm3 s−1, respectively. Combining these measurements with the literature values at 300 K, we propose a functional temperature dependence in the range 300–2200 K of 3.0 × 10−10(T/300)0.3 cm3 s−1 for the C state, and a constant value of 3.0 × 10−10 cm3 s−1 for the B state.
233 citations
TL;DR: In this paper, the effect of background pressure and synthesis temperature on the graphene crystal sizes in chemical vapor deposition (CVD) on copper catalyst was quantitatively demonstrated and provided the activation energy for graphene nucleation in atmospheric pressure CVD (9 eV).
Abstract: In this paper we discuss the effect of background pressure and synthesis temperature on the graphene crystal sizes in chemical vapor deposition (CVD) on copper catalyst. For the first time, we quantitatively demonstrate a fundamental role of the background pressure and provide the activation energy for graphene nucleation in atmospheric pressure CVD (9 eV), which is substantially higher than for the low pressure CVD (4 eV). We attribute the difference to a greater importance of copper sublimation in the low pressure CVD, where severe copper evaporation likely dictates the desorption rate of active carbon from the surface. At atmospheric pressure, where copper evaporation is suppressed, the activation energy is assigned to the desorption energy of carbon clusters instead. The highest possible temperature, close to the melting point of copper, should be used for large single crystal graphene synthesis. Using these conditions, we have synthesized graphene single crystals with sizes over 0.5 mm. Single crysta...
205 citations
TL;DR: The line of density maxima of water at negative pressure is found to reach 922:8 kgm3 at around 300 K, which further constrains its contested phase diagram as discussed by the authors.
Abstract: Liquid water at atmospheric pressure can be supercooled to 41 C (ref. 1) and superheated to C302 C (ref. 2). Experiments involving fluid inclusions of water in quartz suggest that water is capable of sustaining pressures as low as 140 MPa before it breaks by cavitation3. Other techniques, for which cavitation occurs consistently at around 30MPa (ref. 4), produce results that cast doubt on this claim. Here we reproduce the fluid-inclusion experiment, performing repeated measurements on a single sample--a method used in meteorology5, bioprotection6 and protein crystallization7, but not yet in liquid water under large mechanical tension. The resulting cavitation statistics are characteristic of a thermally activated process, and both the free energy and the volume of the critical bubble are well described by classical nucleation theory when the surface tension is reduced by less than 10%, consistent with homogeneous cavitation. The line of density maxima of water at negative pressure is found to reach 922:8 kgm3 at around 300 K, which further constrains its contested phase diagram.
184 citations
TL;DR: In this article, an atmospheric pressure direct current (DC) plasma jet is investigated in N2 and dry air in terms of plasma properties and generation of active species in the active zone and the afterglow.
Abstract: An atmospheric pressure direct current (DC) plasma jet is investigated in N2 and dry air in terms of plasma properties and generation of active species in the active zone and the afterglow. The influence of working gases and the discharge current on plasma parameters and afterglow properties are studied. The electrical diagnostics show that discharge can be sustained in two different operating modes, depending on the current range: a self-pulsing regime at low current and a glow regime at high current. The gas temperature and the N2 vibrational temperature in the active zone of the jet and in the afterglow are determined by means of emission spectroscopy, based on fitting spectra of N2 second positive system (C3Π-B3Π) and the Boltzmann plot method, respectively. The spectra and temperature differences between the N2 and the air plasma jet are presented and analyzed. Space-resolved ozone and nitric oxide density measurements are carried out in the afterglow of the jet. The density of ozone, which is formed in the afterglow of nitrogen plasma jet, is quantitatively detected by an ozone monitor. The density of nitric oxide, which is generated only in the air plasma jet, is determined by means of mass-spectroscopy techniques.
132 citations
01 Jan 2013
TL;DR: The mechanism developed herein to describe 2MF combustion should also function as a sub-mechanism to describe the oxidation of 2,5-dimethyl furan whilst also providing key insights into the oxide of this similar biofuel candidate.
Abstract: An experimental ignition delay time study for the promising biofuel 2-methyl furan (2MF) was performed at equivalence ratios of 0.5, 1.0 and 2.0 for mixtures of 1% fuel in argon in the temperature range 1200-1800 K at atmospheric pressure. Laminar burning velocities were determined using the heat-flux method for mixtures of 2MF in air at equivalence ratios of 0.55-1.65, initial temperatures of 298-398 K and atmospheric pressure. A detailed chemical kinetic mechanism consisting of 2059 reactions and 391 species has been constructed to describe the oxidation of 2MF and is used to simulate experiment. Accurate reproduction of the experimental data has been obtained over all conditions with the developed mechanism. Rate of production and sensitivity analyses have been carried out to identify important consumption pathways of the fuel and key kinetic parameters under these conditions. The reactions of hydrogen atom with the fuel are highlighted as important under all experimental conditions studied, with abstraction by the hydrogen atom promoting reactivity and hydrogen atom addition to the furan ring inhibiting reactivity. This work, to the authors knowledge, is the first to combine theoretical and experimental work to describe the oxidation of any of the alkylated furans. The mechanism developed herein to describe 2MF combustion should also function as a sub-mechanism to describe the oxidation of 2,5-dimethyl furan whilst also providing key insights into the oxidation of this similar biofuel candidate.
131 citations
TL;DR: In this paper, the interaction mechanisms between nonthermal atmospheric pressure plasmas are studied for biomedical applications, but very little fundamental information on the interaction mechanism between the plasma s...
Abstract: Nonthermal atmospheric pressure plasmas are gaining increasing attention for biomedical applications. However, very little fundamental information on the interaction mechanisms between the plasma s...
123 citations
TL;DR: In this article, the authors examined and advanced a theory as to how condensation influences atmospheric pressure through the mass re- moval of water from the gas phase with a simultaneous ac- count of the latent heat release.
Abstract: Phase transitions of atmospheric water play a ubiquitous role in the Earth's climate system, but their direct impact on atmospheric dynamics has escaped wide attention. Here we examine and advance a theory as to how conden- sation influences atmospheric pressure through the mass re- moval of water from the gas phase with a simultaneous ac- count of the latent heat release. Building from fundamental physical principles we show that condensation is associated with a decline in air pressure in the lower atmosphere. This decline occurs up to a certain height, which ranges from 3 to 4 km for surface temperatures from 10 to 30 C. We then estimate the horizontal pressure differences associated with water vapor condensation and find that these are comparable in magnitude with the pressure differences driving observed circulation patterns. The water vapor delivered to the atmo- sphere via evaporation represents a store of potential energy available to accelerate air and thus drive winds. Our estimates suggest that the global mean power at which this potential energy is released by condensation is around one per cent of the global solar power - this is similar to the known station- ary dissipative power of general atmospheric circulation. We conclude that condensation and evaporation merit attention as major, if previously overlooked, factors in driving atmo- spheric dynamics.
122 citations
TL;DR: Results from experiments mimicking pressure changes experienced by particle-associated prokaryotes during their descent through the water column show that rates of degradation of organic matter by surface-originating microorganisms decrease with sinking.
Abstract: Effects of hydrostatic pressure on pure cultures of prokaryotes have been studied extensively but impacts at the community level in the ocean are less well defined. Here we consider hydrostatic pressure effects on natural communities containing both unadapted (piezosensitive) prokaryotes originating from surface water and adapted (including piezophilic) prokaryotes from the deep sea. Results from experiments mimicking pressure changes experienced by particle-associated prokaryotes during their descent through the water column show that rates of degradation of organic matter (OM) by surface-originating microorganisms decrease with sinking. Analysis of a much larger data set shows that, under stratified conditions, deep-sea communities adapt to in situ conditions of high pressure, low temperature and low OM. Measurements made using decompressed samples and atmospheric pressure thus underestimate in situ activity. Exceptions leading to overestimates can be attributed to deep mixing events, large influxes of surface particles, or provision of excessive OM during experimentation. The sediment-water interface, where sinking particles accumulate, will be populated by a mixture of piezosensitive, piezotolerant and piezophilic prokaryotes, with piezophilic activity prevailing deeper within sediment. A schematic representation of how pressure shapes prokaryotic communities in the ocean is provided, allowing a reasonably accurate interpretation of the available activity measurements.
115 citations
01 Jan 2013
TL;DR: In this article, the authors discuss the geodetic and atmospheric background of microwave signals and the effects of ionospheric effects on microwave signals in the neutral atmosphere and gravity space missions.
Abstract: Foreword - Preface - Acknowledgements - Geodetic and atmospheric background - Ionospheric effects on microwave signals - Path delays in the neutral atmosphere - Atmospheric pressure loading - Atmospheric effects on gravity space missions - Atmospheric effects on Earth rotation
TL;DR: In this paper, a time modulated radio frequency (RF) plasma jet operated with an Ar mixture is investigated by measuring the electron density and electron temperature using Thomson scattering, and the influence of the plasma on the air entrainment into the effluent is studied using Raman scattering.
Abstract: A time modulated radio frequency (RF) plasma jet operated with an Ar mixture is investigated by measuring the electron density and electron temperature using Thomson scattering. The measurements have been performed spatially resolved for two different electrode configurations and as a function of the plasma dissipated power and air concentration admixed to the Ar. Time resolved measurements of electron densities and temperatures during the RF cycle and after plasma power switch-off are presented. Furthermore, the influence of the plasma on the air entrainment into the effluent is studied using Raman scattering.
TL;DR: In this article, a radio-frequency-driven Ar-H2O atmospheric-pressure plasma jet by laser-induced fluorescence (LIF), calibrated by Rayleigh scattering and by UV broadband absorption, was measured in ambient air and the effect of air entrainment into the Ar jet by analyzing the time-resolved fluorescence signals.
Abstract: Absolute OH densities are obtained in a radio-frequency-driven Ar–H2O atmospheric-pressure plasma jet by laser-induced fluorescence (LIF), calibrated by Rayleigh scattering and by UV broadband absorption. The measurements are carried out in ambient air and the effect of air entrainment into the Ar jet is measured by analyzing the time-resolved fluorescence signals. The OH densities are obtained for different water vapor concentrations admixed to the Ar and as a function of the axial distance from the nozzle. A sensitivity analysis to deduce the accuracy of the model-calculated OH density from the LIF measurement is reported. It is found that the UV absorption and the LIF results correspond within experimental accuracy close to the nozzle and deviate in the far effluent. The possible reasons are discussed. The OH densities found in the plasma jet are in the range (0.1–2.5) × 1021 m−3 depending on the water concentration and plasma conditions.
TL;DR: In this paper, a time modulated RF atmospheric pressure plasma jet, operated in ambient air with a flow of argon with a few per cent of air, N2 or O2, was characterized by measuring the gas temperature with Rayleigh scattering, the absolute NO density with laser-induced fluorescence, and the emission of NO A and N2 C with time resolved optical emission spectroscopy.
Abstract: A time modulated RF atmospheric pressure plasma jet, operated in ambient air with a flow of argon with a few per cent of air, N2 or O2, was characterized by measuring the gas temperature with Rayleigh scattering, the absolute NO density with laser-induced fluorescence, and the emission of NO A and N2 C with time resolved optical emission spectroscopy. The gas temperature, NO density and the emission measurements are carried out both time and spatially resolved. The atmospheric pressure plasma jet has the advantage that the plasma dissipated power can be measured, and it was found that the gas temperature depends on the power, rather than the gas mixture. The NO density increases with increasing plasma power, and was found to have a maximum around 1.5 × 1021 m−3 at an air admixture of 2%. The N2 C emission is modulated by the 13.9 MHz RF frequency, while the NO A emission front increases with much slower velocity during the 20 kHz duty cycle, which gives an insight into the excitation mechanisms in the plasma. Through the addition of either N2 or O2 to the plasma it was experimentally confirmed that the production of atomic N radicals are of key importance for the NO production in this atmospheric pressure plasma jet.
01 Jan 2013
TL;DR: In this article, a detailed thermochemical reaction model for a stoichiometric argon-diluted hydrogen-oxygen mixture at low pressures and a hydrogen-air mixture at atmospheric pressure was performed.
Abstract: Time-dependent, multidimensional simulations of unstable propagating detonations were performed using a detailed thermochemical reaction model for a stoichiometric argon-diluted hydrogen–oxygen mixture at low pressures and a hydrogen–air mixture at atmospheric pressure. Detonation cells computed for the low-pressure, dilute H 2 –O 2 –Ar systems were regular in shape, and their sizes compared reasonably well with experimental observations. The computed H 2 –air cells at atmospheric conditions were qualitatively different from those observed in experiments, and their widths range from less than 1 mm to nearly 5 mm with multilevel hierarchal structures. The effective activation energy of the H 2 –air mixture, based on constant-volume ignition delay times computed using the detailed thermochemical model, varies between 5 and 40 over the range of post-shock temperatures and pressures in the simulations and is, on average, significantly larger than expected based on the regularity of experimental cellular patterns. Analysis of the simulations suggests that vibrational relaxation of the gas molecules, a process which is ignored when calibrating detailed chemical reaction models, occurs on time scales similar to the ignition delay times for the detonations and may be a source of discrepancy between numerical and experimental results.
TL;DR: In this paper, a detailed kinetic mechanism of aromatic growth, particulate formation, and oxidation is presented and tested in non-premixed laminar flames of methane and ethylene at atmospheric pressure.
Abstract: A detailed kinetic mechanism of aromatic growth, particulate formation, and oxidation is presented and is tested in nonpremixed laminar flames of methane and ethylene at atmospheric pressure. Model...
TL;DR: In this article, the axial electric field distribution in the plasma jet was inferred from the optical emission spectroscopic data and from the probe measurement, and the correlation between the jet velocities, jet length with the pulse duration was established.
Abstract: In this paper He-discharge (plasma jet/bullet) in atmospheric pressure air and its progression phenomenon has been studied experimentally using ICCD camera, optical emission spectroscopy (OES) and calibrated dielectric probe measurements. The repetitive nanosecond pulse has applied to a plasma pencil to generate discharge in the helium gas channel. The discharge propagation speed was measured from the ICCD images. The axial electric field distribution in the plasma jet is inferred from the optical emission spectroscopic data and from the probe measurement. The correlation between the jet velocities, jet length with the pulse duration is established. It shows that the plasma jet is not isolated from the input voltage along its propagation path. The discharge propagation speed, the electron density and the local and average electric field distribution along the plasma jet axis predicted from the experimental results are in good agreement with the data predicted by numerical simulation of the streamer propagation presented in different literatures. The ionization phenomenon of the discharge predicts the key ionization parameters, such as speed, peak electric field in the front, and electron density. The maximum local electric field measured by OES is 95 kV/cm at 1.3 cm of the jet axis, and average EF measured by probe is 24 kV/cm at the same place of the jet. The average and local electron density estimated are in the order of 1011 cm-3 and it reaches to the maximum of 1012 cm-3.
TL;DR: In this paper, the effect of ambient air transport into the effluent of an atmospheric-pressure plasma argon jet on the on-axis densities of nitrogen, oxygen and argon was investigated by means of absolutely calibrated molecular beam mass spectrometry (MBMS).
Abstract: Ambient air species, which are transported into the active effluent of an atmospheric-pressure plasma jet result in highly reactive oxygen and nitrogen species (RONS). Especially for the envisaged application field of plasma medicine, these RONS are responsible for strong biological responses. In this work, the effect of ambient air transport into the effluent of an atmospheric-pressure plasma argon jet on the on-axis densities of nitrogen, oxygen and argon was investigated by means of absolutely calibrated molecular beam mass spectrometry (MBMS). According to biomedical experiments a (bottomless) Petri dish was installed in front of the MBMS. In the following, the near flow field is referring to the region close to the nozzle exit and the far flow field is referring to the region beyond that. The absolute on-axis densities were obtained by three different methods, for the near flow field with VUV-absorption technique, for the far flow field with the MBMS and the total flow field was calculated with a computational fluid dynamics (CFD) simulation. The results of the ambient air particle densities of all independent methods were compared and showed an excellent agreement. Therefore the transport processes of ambient air species can be measured for the whole effluent of an atmospheric-pressure plasma jet. Additionally, with the validation of the simulation it is possible in future to calculate the ambient species transport for various gas fluxes in the same turbulent flow regime. Comparing the on-axis densities obtained with an ignited and with a non-ignited plasma jet shows that for the investigated parameters, the main influence on the ambient air species transport is due to the increased temperature in the case when the jet is switched on. Moreover, the presence of positive ions (e.g. ) formed due to the interaction of plasma-produced particles and ambient air species, which are transported into the effluent, is shown.
TL;DR: In this article, Wang et al. reported new experimental findings at a reduced atmospheric pressure (at high altitude in Tibet) for turbulent buoyant jet diffusion flames and global correlations for both normal and lower atmospheric pressure.
TL;DR: In this paper, the authors studied sea level in the Mediterranean Sea over the period 1993-2011 and found that the increase in sea level does not take place linearly but over two 2-3 year periods, each contributing 2 −3 cm of sea level.
Abstract: [1] Sea level in the Mediterranean Sea over the period 1993–2011 is studied on the basis of altimetry, temperature, and salinity data and gravity measurements from Gravity Recovery and Climate Experiment (GRACE) (2002–2010). An observed increase in sea level corresponds to a linear sea level trend of 3.0 ± 0.5 mm/yr dominated by the increase in the oceanic mass in the basin. The increase in sea level does not, however, take place linearly but over two 2–3 year periods, each contributing 2–3 cm of sea level. Variability in the basin sea level and its mass component is dominated by the winter North Atlantic Oscillation (NAO). The NAO influence on sea level is primarily linked with atmospheric pressure changes and local wind field changes. However, neither the inverse barometer correction nor a barotropic sea level model forced by atmospheric pressure and wind can remove fully the NAO influence on the basin sea level. Thus, a third contributing mechanism linked with the NAO is suggested. During winter 2010, a low NAO index caused a basin sea level increase of 12 cm which was almost wholly due to mass changes and is evidenced by GRACE. About 8 cm of the observed sea level change can be accounted for as due to atmospheric pressure and wind changes. The residual 4 cm of sea level change is caused by the newly identified contribution. The physical mechanisms that may be responsible for this additional contribution are discussed.
TL;DR: In this article, the absolute density of atomic oxygen (O) in a coaxial microwave jet in ambient air at atmospheric pressure, operated with a mixture of He and a few per cent of air, is measured spatially resolved, and as a function of admixed air to the He, and microwave power.
Abstract: Two-photon absorption laser-induced fluorescence (TALIF) is used to measure the absolute density of atomic oxygen (O) in a coaxial microwave jet in ambient air at atmospheric pressure, operated with a mixture of He and a few per cent of air. The TALIF signal is calibrated using a gas mixture containing Xe. A novel method to perform calibration in situ, at atmospheric pressure, is introduced. The branching ratios of several Xe mixtures are reported, to enable us to perform the Xe calibration without the need for a vacuum vessel. The O densities are measured spatially resolved, and as a function of admixed air to the He, and microwave power. The electron density and temperatures are measured using Thomson scattering, and the N2 and O2 densities are measured using Raman scattering. O densities are found to have a maximum of (4?6)???1022?m?3, which indicate that O2 is close to fully dissociated in the plasma. This is confirmed by the Raman scattering measurements. O is found to recombine mainly into species other than O2 in the afterglow, which is suggested to consist of O3 and oxidized components of NO.
TL;DR: In this article, a NiO/Al2O3 catalyst was used in a H2/Ar dielectric barrier discharge at atmospheric pressure and low temperature (<300°C) to get a better understanding of the reduction mechanisms involved in the plasma process.
TL;DR: In this article, the authors implemented a one-dimensional energy balance model (EBM), the simplest seasonal model of planetary climate, with new prescriptions for most physical quantities, to investigate the surface habitability of planets with an Earth-like atmospheric composition but different levels of surface pressure.
Abstract: As a contribution to the study of the habitability of extrasolar planets, we implemented a one-dimensional energy balance model (EBM), the simplest seasonal model of planetary climate, with new prescriptions for most physical quantities. Here we apply our EBM to investigate the surface habitability of planets with an Earth-like atmospheric composition but different levels of surface pressure. The habitability, defined as the mean fraction of the planet's surface on which liquid water could exist, is estimated from the pressure-dependent liquid water temperature range, taking into account seasonal and latitudinal variations of surface temperature. By running several thousands of EBM simulations we generated a map of the habitable zone (HZ) in the plane of the orbital semi-major axis, a, and surface pressure, p, for planets in circular orbits around a Sun-like star. As pressure increases, the HZ becomes broader, with an increase of 0.25 AU in its radial extent from p = 1/3 to 3 bar. At low pressure, the habitability is low and varies with a; at high pressure, the habitability is high and relatively constant inside the HZ. We interpret these results in terms of the pressure dependence of the greenhouse effect, the efficiency of horizontal heat transport, and the extent of the liquid water temperature range. Within the limits discussed in the paper, the results can be extended to planets in eccentric orbits around non-solar-type stars. The main characteristics of the pressure-dependent HZ are modestly affected by variations of planetary properties, particularly at high pressure.
TL;DR: It is demonstrated that, using a conventional thermionic TEM, 2 Å atomic fringes can be resolved with the presence of 1 bar O2 gases in an environmental cell and real-time observation of the Kirkendall effect during oxidation of cobalt nanocatalysts is shown.
Abstract: The understanding of solid-gas interactions has been greatly advanced over the past decade on account of the availability of high-resolution transmission electron microscopes (TEMs) equipped with differentially pumped environmental cells. The operational pressures in these differentially pumped environmental TEM (DP-ETEM) instruments are generally limited up to 20 mbar. Yet, many industrial catalytic reactions are operated at pressures equal or higher than 1 bar-50 times higher than that in the DP-ETEM. This poses limitations for in situ study of gas reactions through ETEM and advances are needed to extend in situ TEM study of gas reactions to the higher pressure range. Here, we present a first series of experiments using a gas flow membrane cell TEM holder that allows a pressure up to 4 bar. The built-in membrane heaters enable reactions at a temperature of 95-400°C with flowing reactive gases. We demonstrate that, using a conventional thermionic TEM, 2 A atomic fringes can be resolved with the presence of 1 bar O2 gases in an environmental cell and we show real-time observation of the Kirkendall effect during oxidation of cobalt nanocatalysts.
TL;DR: It was found that the presence of both heavy surfactants results in a significant increase in the net intensity of analytical lines of metals and a notable reduction of the intensity of bands of diatomic molecules and the background.
TL;DR: In this article, the authors investigated the thermodynamic effects associated with the growth and collapse of a single cavitation bubble by an experimental approach, focusing on the temperature variations in the liquid surrounding the bubble.
Abstract: The thermodynamic effects associated with the growth and collapse of a single cavitation bubble are investigated in the present paper by an experimental approach The study focuses on the temperature variations in the liquid surrounding the bubble Experiments are conducted in a cylinder partially filled with water at an ambient temperature and atmospheric pressure The bubble growth results from the expansion of an initial air bubble, due to the pressure wave generated by a so-called ‘tube-arrest’ method Several locations of the bubble, at different distances from the bottom wall of the cylinder, are considered The bottom wall is made of sapphire, which is transparent to both the visible and infrared light spectra which enables temperature measurements by a high-speed thermovision camera at a wavelength of 3– Water is opaque to the infrared light spectrum, hence only temperatures in the boundary layer and on the liquid vapour interface could be determined A temperature decrease of K was recorded during the bubble growth while an increase up to 4 K was detected during the collapse Experimental results are compared to the predictions of the ‘thermal delay’ model based on the assumption that the bubble growth and collapse are due to phase changes only In this approach, the temperature variations are related to the latent heat exchanges during the vapourization and condensation processes On the basis of these results, the respective effects of phase change and air dilatation/compression in the bubble dynamics are discussed
TL;DR: In this article, the synthesis of nanoparticles by means of electrical discharges between two electrodes in an inert gas at atmospheric pressure, as driven by a constant current ranging from a few milliamps to tens of amps, is investigated.
Abstract: The synthesis of nanoparticles by means of electrical discharges between two electrodes in an inert gas at atmospheric pressure, as driven by a constant current ranging from a few milliamps to tens of amps, is investigated in this work. An extensive series of experiments are conducted with copper as a consumable electrode and pure nitrogen as the inert gas. Three different DC power supplies are used to drive electrical discharges for the entire operating current range. Then, three electrical discharge regimes (spark, glow, and arc) with distinct voltage–current characteristics and plasma emission spectra are recognized. For the first time, nanoparticles are synthesized by evaporation of an electrode by atmospheric pressure inert gas DC glow discharge of a few millimeters in size. The discharge regimes are characterized in terms of the mass output rate and the particle size distribution of the copper aerosols by means of online (tapered element oscillating microbalance, TEOM; and scanning mobility particle sizer, SPMS) and offline (gravimetric analysis; small and wide angle X-ray scattering, SWAXS; and transmission electron microscopy, TEM) techniques. The electrical power delivered to the electrode gap and the gas flow rate are two major parameters determining the aerosol mass output rate and the aerosol particle size distribution. The mass output rate of copper aerosols raises from 2 mg h−1 to 2 g h−1 when increasing the electrical power from 9 to 900 W. The particle mean size (SMPS d
g) varies between 20 and 100 nm depending upon the electrical power and the gas flow rate, whereas the particle size dispersion (SMPS σ
g) ranges from 1.4 to 1.7 and is only weakly dependent on the gas flow rate.
TL;DR: In this article, the densities and dynamic viscosities of binary mixtures of n-octane with ethanol, 1-propanol, 1butanol, and 1-pentanol were analyzed at atmospheric pressure from (293.15 to 3...
Abstract: We present densities and dynamic viscosities of binary mixtures of n-octane with ethanol, 1-propanol, 1-butanol, and 1-pentanol. Measurements are performed at atmospheric pressure from (293.15 to 3...
TL;DR: In this article, microwave atmospheric pressure plasmas driven by surface waves were used to synthesize graphene sheets from vaporized ethanol molecules carried through argon plasma, where external cooling/heating was applied.
Abstract: Microwave atmospheric pressure plasmas driven by surface waves were used to synthesize graphene sheets from vaporized ethanol molecules carried through argon plasma. In the plasma, ethanol decomposes creating carbon atoms that form nanostructures in the outlet plasma stream, where external cooling/heating was applied. It was found that the outlet gas stream temperature plays an important role in the nucleation processes and the structural quality of the produced nanostructures. The synthesis of few layers (from one to five) graphene has been confirmed by high-resolution transmission electron microscopy. Raman spectral studies were conducted to determine the ratio of the 2D to G peaks (>2). Disorder D-peak to G-peak intensity ratio decreases when outlet gas stream temperature decreases.
TL;DR: In this article, a two-dimensional air plasma kinetics model (16 species and 44 processes) was developed to reveal the spatial and temporal distribution of discharge characteristics of a surface dielectric barrier discharge (SDBD) actuator.
Abstract: A two-dimensional air plasma kinetics model (16 species and 44 processes) for nanosecond discharge under atmospheric pressure was developed to reveal the spatial and temporal distribution of discharge characteristics of a surface dielectric barrier discharge (SDBD) actuator. An energy transfer model, including two channels for energy release from external power source to gas, was developed to couple plasma with hydrodynamics directly in the same dimension. The governing equations included the Poisson equation for the electric potential, continuity equations for each species, electron energy equations for electrons taking part in reactions, and Navier–Stokes equations for non-isothermal fluid. The model was validated through current–voltage profile and electron temperature obtained from experiments. Calculations for discharge characteristics as well as the responses of fluid field from tens of nanoseconds to tens of seconds were performed. Results have shown that local air is heated to 1170 K within tens of nanoseconds and then decreases to 310 K at the end of a discharge period. 30% of the total power is transferred from electric field to electrons while only 20% of this energy is then released to gas through quenching processes. 9% of the total energy is released through ion collision. A micro-shock wave is formed and propagates at the speed of sound. High local density gradient and dynamic viscosity induces vortexes which whirl the heated air downstream. The combined effects of heating convection and vortexes in repetitive pulse discharges lead to the formation of a steady jet, in agreement with experimental results.