Small Percentage Of Oxygen Research Articles

(Invited) Electrochemical Approaches for Generating Oxygen on the Moon

The development of efficient in-situ resource utilizsation (ISRU) processes to generate oxygen on the Moon will be essential for enabling human exploration of the Moon and the wider solar system. In this talk, we will look at electrochemical studies on two different approaches to this goal. The first approach involves the electro-deoxidation of powdered lunar regolith by a Metalysis-FFC-Cambridge approach to produce oxygen and metal alloys (Planet. Space Sci. 2020, 180, 104748; Planet. Space Sci. 2022, 211, 105408). The resulting metallic powder was found to contain only a very small percentage of oxygen (a portion of which was due to post electrolysis surface re-oxidation) and to consist primarily of Al/Fe(-Si), Fe/Si(-Ti/Al), and Ca/Si/Al(-Mg) alloys. In the second half of the talk, we will examine the efficiency of water electrolysis (and specifically of the oxygen evolving half-reaction) under reduced gravity levels, including lunar gravity, and we will discuss the prospects that these results present for performing electrolysis of water to generate oxygen on the Moon (Nat. Commun. 2022, 13, 583). Figure 1

Atmospheric plasma jet for surface treatment of biomaterials

A direct current (DC) powered low-temperature atmospheric pressure plasma (LTAPP) jet device was built and used to sterilize Escherichia coli (E. coli) bacteria. The plasma jet’s general properties, such as length and temperature, were first tested and found to be strongly related to the plasma jet’s operational flow mode (laminar or turbulent flow). The optical emission spectra of various gas mixtures were measured to confirm the presence of active radicals, which is critical for sterilization success. Pure helium gas or a combination of helium with a small percentage of oxygen (6.25%) was found to have the highest intensities of bactericidal species such as atomic oxygen (O) and hydroxide (OH). These mixtures were then used to treat E. coli bacteria previously grown in a Petri dish. Sterilization was accomplished by repeatedly treating the bacteria for 10 s for 5–10 rounds for short periods. The best results were obtained when the bacteria had enough time to rest between rounds.

Reactive fluxes delivered by plasma jets to conductive dielectric surfaces during multiple reflections of ionization waves

In this paper, we report results from the computational study of the intersection of the atmospheric pressure plasma jet with a dielectric surface having high conductivity and high dielectric constant. In this case, multiple reflections of the ionization wave (IW) between the jet tube and the surface are observed. We consider the mixture of helium with a small percentage of oxygen (He/O2 = 99.8/0.2), which flows through the jet tube into the ambient humid room air (N2/O2/H2O = 79.5/20/0.5). We evaluate the production and delivery of main ions and reactive oxygen and nitrogen species, which are important for applications in biomedicine. The fluxes and fluences of these species to the dielectric surface are recorded during a single plasma jet pulse of negative polarity. We show that the electron density behind the IW front increases with each passage of the IW between the tube and the surface. With the forward, reflected, and secondary forward IW, there is an essential increase of ions and radicals behind the IW front. The highest increase of radicals and their fluxes is observed after the secondary forward wave bridges the gap and touches the surface.

Proving the Viability of an Electrochemical Process for the Simultaneous Extraction of Oxygen and Production of Metal Alloys from Lunar Regolith

The development of an efficient process to simultaneously extract oxygen and metals from lunar regolith by way of in-situ resource utilisation (ISRU) has the potential to enable sustainable exploration beyond Earth. The Metalysis (FFC Cambridge) process can electrochemically reduce a wide range of metal oxides to produce metals and alloys for powdered metallurgy and additive manufacturing, with the co-generation of oxygen at the anode. In this talk, we will demonstrate proof-of-concept for the electro-deoxidation of powdered lunar regolith by a Metalysis-FFC approach to produce oxygen and metal alloys. The resulting metallic powder was found to contain only a very small percentage of oxygen (a portion of which was due to post electrolysis surface re-oxidation) and to consist primarily of Al/Fe(-Si), Fe/Si(-Ti/Al), and Ca/Si/Al(-Mg) alloys. The challenges and opportunities for the Metalysis-FFC process for lunar ISRU will be discussed in light of the results presented in this talk.

Microstructural, compositional, topological and optical properties of plasma polymerized cyclohexane amorphous thin films

Synthesis of plasma polymerized cyclohexane (PPCHex) thin films on to glass substrates has been done using a capacitively coupled parallel plate low-pressure glow discharge technique from cyclohexane at room temperature. From scanning electron microscopy, smooth and homogeneous surface of PPCHex thin films is observed and atomic force microscopic micrographs show the roughness of 0.815 to 0.364 nm which also confirm the smooth, homogenous, pinhole free and uniform surface of the PPCHex thin films. The presence of 73.1 and 74.7 percentage of carbon in PPCHex thin films of thicknesses 220 and 350 nm with a small percentage of oxygen is confirmed by the energy dispersive x-ray analysis. The PPCHex thin film is thermally stable up to about 510 K. The structure of PPCHex thin films is observed to vary with film’s thickness by forming new chemical bonds such as O-H stretching, C=C stretching, C≡C stretching, C-O stretching compared to that of the monomer. Allowed direct band gaps of PPCHex thin films are found between 2.97 and 3.61 eV for different thicknesses and allowed indirect band gaps are found to be 1.83 to 2.31 eV. Therefore, the PPCHex could be used in different type of optoelectronic devices.

Reactive Species Production In Argon And Helium Plasma Jets: Reactivity Transfer From Plasma To Liquid Layers

Atmospheric pressure plasma jets are often used in plasma medicine as sources of reactive species in biomedical applications including the treatment of wounds and cancerous tumors. A rare gas or a mixture of a rare gas with a small percentage of oxygen are often used as a plasma-forming gases [1]. The biological responses are attributed to the production of reactive oxygen and nitrogen species. The reactive species generated by the plasma diffuse through a thin layer of a biological liquid which usually covers the treated sample. In this work, we discuss results from computational investigations of properties of a single jet and jets array operated in He and Ar. We quantify densities and fluxes of reactive species produced by jets in the bulk plasma (Figure 1). We then investigate the reactivity transfer from the plasma into the liquid. As this process typically occurs on a large dynamic ranges of timescales, the plasma–liquid interactions and liquid phase chemistry are considered on a short (ns) and long (ms) time scales. This investigation is conducted using the 2D modeling platform nonPDPSIM, which solves transport equations for charged and neutral species, Poisson’s equation for the electric potential, the electron energy conservation equation for the electron temperature and Navier–Stokes equations for the neutral gas flow. The model is essentially the same as used in [2]. The reaction mechanism includes plasma and neutral chemistry for He/humid air and Ar/humid air as well as liquid phase chemistry. Download : Download high-res image (388KB) Download : Download full-size image Figure 1. (a) and (c): Flow patterns for helium and argon jet into ambient air. Numbers at the lines show helium and argon mole fraction. (b) and (d): OH radicals production during a short plasma time scale for helium and argon jet, respectively.

A comparison between micro hollow cathode discharges and atmospheric pressure plasma jets in Ar/O2 gas mixtures

Using global models, micro hollow cathode discharges (MHCDs) are compared to radiofrequency atmospheric pressure plasma jets (APPJs) in terms of reactive oxygen species (ROS) production. Ar/O2 gas mixtures are investigated, typically with a small percentage of oxygen in argon. The same chemical reaction set, involving 17 species and 128 chemical reactions in the gas phase, is used for both devices, operated in the typical geometries previously published; the APPJ is driven by a radiofrequency voltage across a 1 mm gap, at atmospheric pressure, while the MHCD is driven by a DC voltage source, at 100 Torr and in a 400 μm hole. The MHCD may be operated either in the self-pulsing or in the normal (stationary) regime, depending on the driving voltage. The comparison shows that in both regimes, the MHCD produces larger amounts of , while the APPJ produces predominantly reactive oxygen ground state species, and . These large differences in ROS composition are mostly due to the higher plasma density produced in the MHCD. The difference in operating pressure is a second order effect.

Optimization of a Gas Switching Combustion process through advanced heat management strategies

Gas Switching Combustion (GSC) is a promising new process concept for energy efficient power production with integrated CO2 capture. In comparison to conventional Chemical Looping Combustion (CLC) carried out in interconnected fluidized beds, the GSC concept will be substantially easier to design and scale up, especially for pressurized conditions. One potential drawback of the GSC concept is the gradual temperature variation over the transient process cycle, which leads to a drop in electric efficiency of the plant. This article investigates heat management strategies to mitigate this issue both through simulations and experiments. Simulation studies of the GSC concept integrated into an IGCC power plant show that heat management using a nitrogen recycle stream can increase plant efficiency by 3 percentage points to 41.6% while maintaining CO2 capture ratios close to 90%. Reactive multiphase flow simulations of the GSC reactor also showed that heat management can eliminate fuel slip problems. In addition, the GSC concept offers the potential to remove the need for a nitrogen recycle stream by implementing a concentrated air injection that extracts heat while only a small percentage of oxygen reacts. Experiments have shown that, similar to nitrogen recycle, this strategy reduces transient temperature variations across the cycle and therefore merits further investigation.

Recent aging studies for the ATLAS transition radiation tracker

The transition radiation tracker (TRT) is one of the three subsystems of the inner detector of the ATLAS experiment. It is designed to operate for 10 yr at the LHC, with integrated charges of /spl sim/10 C/cm of wire and radiation doses of about 10 Mrad and 2/spl times/10/sup 14/ neutrons/cm/sup 2/. These doses translate into unprecedented ionization currents and integrated charges for a large-scale gaseous detector. This paper describes studies leading to the adoption of a new ionization gas regime for the ATLAS TRT. In this new regime, the primary gas mixture is 70%Xe-27%CO/sub 2/-3%O/sub 2/. It is planned to occasionally flush and operate the TRT detector with an Ar-based ternary mixture, containing a small percentage of CF/sub 4/, to remove, if needed, silicon pollution from the anode wires. This procedure has been validated in realistic conditions and would require a few days of dedicated operation. This paper covers both performance and aging studies with the new TRT gas mixture.

Effect Of Capping Layer During Annealing of Low-Dose Lowenergy Simox Materials

Abstract Ultra-thin Silicon-On-Insulator (SOI) materials are becoming increasingly attractive for fabrication of ultra-large scale integrated (ULSI) devices due to their performance, speed, and power reduction advantages [1]. In SIMOX (Separation by IMplanted OXygen) materials, extensive damage can be repaired by high-temperature annealing in an argon ambient. A small percentage of oxygen is added to give a sufficient oxygen partial pressure to prevent formation of silicon monoxide lumps and subsequent pits [2]. Capping the sample surface to prevent external thermal oxidation during annealing is important to preserve the thickness of the top silicon layer. This is particularly critical for the ultra-thin SIMOX produced by the low-dose low-energy process. However, the surface capping also affects the formation of the buried oxide (BOX). To study this effect, two sets of samples implanted at the same doses of 1.5, 2.0, 2.5, and 3.0x 1017O+ /cm2 at 65keV were annealed with or without protective cap on the sample surface.

Coherent anti-Stokes Raman spectroscopy study of collisional broadening in the O2–H2O Q branch

The fundamental isotropic Raman Q branch of oxygen perturbed by collisions with water vapor has been studied at pressures up to 1.5 atm and for temperatures between 446 and 990 K. The spectra have been recorded by using coherent anti-Stokes Raman spectroscopy (CARS) which has been preferred to stimulated Raman spectroscopy (SRS) in order to obtain more signal and higher sensitivity as the mixture has a small percentage of oxygen. The high resolution CARS spectrometer uses a seeded Nd:YAG laser actively stabilized on an external Fabry–Perot interferometer to prevent any frequency drift during the course of the experiment. The line broadening coefficients have been determined for several rotational quantum numbers (up to N=31 at 990 K). The effect of the splitting into triplets at lower pressure and the effect of interferences between neighboring lines at higher pressure have been taken into account. The influence of Dicke narrowing has also been considered and special care has been taken to avoid Stark broadening. The line broadening coefficients have been calculated according to a semiclassical model. The rotational quantum number and temperature dependencies of the experimental line broadening coefficients have also been studied with another approach based on fitting and scaling laws. Among several laws, the modified exponential energy gap law (MEG), the statistical power-exponential gap law (SPEG), and the energy corrected sudden law with basis rate constants taken as a hybrid exponential-power law (ECS-EP) have given good results. We have used the fitting and scaling laws to extrapolate in temperature the linewidths at 2000 K.

Fatigue Failure of GR-S Tread Stocks

Abstract The fundamental nature of fatigue failure in rubber during flexing has been widely studied and is known to be complex. Among the more important factors involved (aside from variations in compounding) are state of cure, temperature of test, and oxidation. The object of this paper is to review and extend these studies as they apply to GR-S. Several investigators have studied the effect of time of cure on the flex cracking resistance of rubber. Busse found that, as the degree of cure was advanced, the flex resistance reached a maximum and then decreased. Similar studies on GR-S show that undercures flex better than either normal cures or overcures. Prettyman, using a different type of machine, showed a maximum near the optimum cure. Cadwell, Merrill, Sloman and Yost and Rainier and Gerke report that the rate of cracking of rubber increased with the temperature of flexing. Similar results have been demonstrated with GR-S by Breckley and by Carlton and Reinbold. Neal and Northam flexed rubber in air, oxygen, and nitrogen on a du Pont type flexing machine. They report no difference between the flexing behavior in air and oxygen. In nitrogen, however, an uninhibited stock flexed five times longer than in air before any failure was evident. The presence of an antioxidant did not change the behavior in nitrogen, but doubled the normal flex-life in air. These workers concluded that the failure of rubber on flexing is due to oxidation rather than to mechanical fatigue. No comparable work on GR-S has yet been reported. The present authors previously showed that oxygen plays an important part in the hardening of GR-S vulcanizates during accelerated aging tests in the 100° C air oven. Since high temperatures are developed during flexing, which might well result in a similar hardening by oxidation, it seemed desirable to determine whether oxygen plays a part in the flex-cracking of GR-S. For this purpose a typical tread stock was selected and flexed in air and in nitrogen which contained various small percentages of oxygen. The effect of state of cure and testing temperatures on the resistance of GR-S to flex-cracking was included in the study.

The Course of Autoöxidation Reactions in Polyisoprenes and Allied Compounds. II. Hydroperoxidic Structure and Chain Scission in Low-Molecular Polyisoprenes

Abstract One of the most astonishing phenomena connected with the chemistry of rubber is the ease with which it absorbs progressively very small percentages of oxygen, and suffers as a result drastic and progressive reduction of its molecular weight. The natural conclusion to be drawn is that the polyisoprene chains of the rubber are undergoing oxidative scission at one after another of their unsaturated centers, so that the original long hydrocarbon chains become divided into smaller and smaller fragments possessing oxygenated ends. Recent estimates of the molecular weight of rubber by viscosity and osmotic methods range from 240,000 to 360,000 for fractions of decreasing solubility in hydrocarbon solvents. If we accept these figures and assume for the moment that two atoms of oxygen are sufficient to sever the hydrocarbon chains at a double bond, then an absorption of only 0.009–0.013 per cent of oxygen (applied, of course, exclusively to scission reactions) should suffice to reduce the average molecular weight to one-half. If the observed reductions of molecular weight are to be ascribed solely to oxidative scission of the chains, then, provided oxygen-consuming side reactions are few, a fairly exact inverse proportionality may be expected to hold between the uptake of oxygen and the average molecular weight of the degraded rubber. The most striking reductions in the molecular weight per unit of oxygen absorbed must, of course, occur at the very early stages of oxidative fission, while the hydrocarbon chains are still very long, and to be able to follow effectively the quantitative relationship between these important reductions and the oxygen uptake, it is necessary to make experimental provision for the absorption, even distribution, and measurement of very minute quantities of oxygen. Minute though the overall proportion of oxygen necessary to produce a substantial reduction in molecular weight appears in practice to be, however, there is no evidence to indicate that the scission reaction ever follows the course most economical in oxygen, i.e.,

23. The course of autoxidation reactions in polyisoprenes and allied compounds. Part II. Hydroperoxidic structure and chain scission in low-molecular polyisoprenes

Abstract One of the most astonishing phenomena connected with the chemistry of rubber is the ease with which it absorbs progressively very small percentages of oxygen, and suffers as a result drastic and progressive reduction of its molecular weight. The natural conclusion to be drawn is that the polyisoprene chains of the rubber are undergoing oxidative scission at one after another of their unsaturated centers, so that the original long hydrocarbon chains become divided into smaller and smaller fragments possessing oxygenated ends. Recent estimates of the molecular weight of rubber by viscosity and osmotic methods range from 240,000 to 360,000 for fractions of decreasing solubility in hydrocarbon solvents. If we accept these figures and assume for the moment that two atoms of oxygen are sufficient to sever the hydrocarbon chains at a double bond, then an absorption of only 0.009–0.013 per cent of oxygen (applied, of course, exclusively to scission reactions) should suffice to reduce the average molecula...

TRIATOMIC HYDROGEN

A study was made of the activation of hydrogen in the alternating-current corona discharge at atmospheric pressure. The resulting test for sulphide was negative unless the gas contained a small percentage of oxygen. Oxygen promoted the activation by acting as a wall poison. Stearic acid also acted as a wall poison in a vacuum tube discharge through hydrogen at pressures from 20 to 80 mm. The hydrogen was freed from oxygen by passing gas from a compressed cylinder over platinized asbestos heated to 550 °C. A fatigue effect appeared which was found to be due to the oxygen content of the hydrogen and to the condition of the walls of the discharge tube.Quantitative determinations of the relation between concentration of the active gas and the velocity of hydrogen show that, at 42 mm. pressure, the concentration varied directly with the velocity up to an optimum flow of 2.4 litres per hour. At a higher rate the concentration varied inversely with the velocity. The per cent activation was found to vary inversely with the pressure between 30 and 80 mm. In the corona discharge the maximum per cent activation for hydrogen containing 0.1% of oxygen was 0.001.A concentration of 0.025% active hydrogen was found for the vacuum discharge in a tube the walls of which were poisoned with stearic acid, and in which the pressure and velocity were 42 mm. and 2.4 litres, respectively.