Effect Of Gaseous Environment Research Articles

Sulfur in kukersite shale oil: its distribution in shale oil fractions and the effect of gaseous environment

Sulfur in kukersite shale oil: its distribution in shale oil fractions and the effect of gaseous environment

Effects of gaseous environments on physicochemical properties of thermally exfoliated graphene oxides for hydrogen storage: a comparative study

The present study compared the effect of different gaseous environments on physicochemical properties and subsequent hydrogen storage ability of thermally exfoliated graphene oxide (EGO). The reducing, inert or oxidizing environments were generated using hydrogen, argon or air as the carrier gas, respectively. The structure of thermally exfoliated graphene oxide depended on the type of gaseous environment. The EGO prepared in presence of Air showed the fluffiest layered structure having highest surface area. The surface area order was EGO(Air) (268 m2/g) > EGO(H2) (248 m2/g) > EGO(Ar) (155 m2/g). The average pore sizes of EGO(Air) and EGO(H2) were 2.9 and 2.8 nm, with pore volumes of 1.2 and 1.6 cm3/g, respectively. The average pore size for EGO(Ar) was highest at 4.1 nm, associated with presence of larger void space and lowest total pore volume of 1.0 cm3/g. Thus, presence of oxidative or reducing atmosphere seemed to be more conducive to exfoliation of layers by gradual removal of functional groups. The inert atmosphere of argon caused severe thermal separation of layers and functional groups, adversely affecting the layered structure as observed. The EGO(Air) also showed highest O/C ratio suggesting presence of significant amount of oxygen–containing functional groups on the surface. The hydrogen uptake order at 77 K and 30 bar was: EGO (Air) 3.34 wt.% > EGO (H2) 3.12 wt.% > EGO (Ar) 2.2 wt.%. The highest uptake of EGO(Air) might have resulted from highest surface area, highest O/C ratio and presence of considerable pore volume.

Thermally Treated Anodically Formed Titanium Oxide Nanotubes Producing Desirable Electrocatalytic Properties

Highly ordered anodically formed titanium oxide nanotubes possess high surface area, biocompatibility and chemical inertness. These properties make them potentially useful for many applications, but these nanotubes are insulative and possess a high band gap limiting their usefulness. Hence, these NTs cannot be directly used for electrocatalysis. Synthesis of titanium oxide nanotubes with good electrocatalytic properties has been a challenge. This study reports on the synthesis of anodically formed NTs with desirable electrocatalytic properties through annealing treatment in 2% hydrogen with a nitrogen balance (H2N2). The changes in the flat band potential, donor density, double layer capacitance and diameter of double layer was investigated using the Mott Schottky plots. The results from the electrochemical testing, scanning electron microscopy (SEM), UV-visible spectroscopy (UV-Vis) for oxygen (O2) annealed NTs and H2N2 annealed NTs were compared to establish a relationship between the effect of gaseous environment on the structure of the NTs and the change in electrocatalytic properties encountered.

Condensed-Phase and Oxidation Reaction Behavior of Ti/2B Foils in Varied Gaseous Environments

The effect of gaseous environment on self-propagating reactions in Ti/2B multilayer foils was studied. Multilayers with reactant layer periodicities from 50 to 3000 nm and a nominal stoichiometry of 1:2 Ti:B were grown using magnetron sputtering. Analysis through scanning transmission electron microscopy, differential scanning calorimetry, and X-ray diffraction revealed the as-deposited multilayers consisted of well-ordered layers of crystalline Ti and amorphous B with the amount of intermixed material negligibly affecting the exothermicity. Propagation rate testing was performed at varied vacuum pressures and studied by high-speed imaging. Propagation rates for foils with bilayer thicknesses 666 nm or thinner did not exhibit a pressure dependency, while foils with bilayer thicknesses 857 nm and larger did. The latter, thick-bilayer foils would not propagate below a characteristic pressure. After reaction, Auger electron spectroscopy revealed O penetration in the thicker bilayer designs and incomplete mixing of Ti and B, while the thinner bilayer foils were uniformly converted to single-phase, hexagonal TiB2. Increased air pressure was found to promote the propagating reaction of the thicker bilayer designs, likely due to increased heat release from oxidation that promotes intermixing and reaction between Ti and B.

Investigations on the effect of gaseous environment during synthesis on the magnetic properties of Mn-doped ZnO

The bulk polycrystalline samples of Mn-doped ZnO were synthesized with the nominal compositions Zn 1− x Mn x O ( x = 0.02, 0.05, 0.10, 0.15, 0.20 and 0.25) via the standard solid state reaction route by sintering at 800 °C in air and argon atmospheres. The X-ray diffraction (XRD) studies of the as synthesized samples exhibit the presence of mainly wurtzite (hexagonal) crystal structure similar to the parent compound (ZnO) in all the samples. In addition to this, XRD results also indicate the presence of secondary phases like ZnMn 2O 4 and Mn 3O 4 in minority. The M– H plots, recorded at room temperature, of the samples sintered in air reveals the presence of mainly paramagnetic behavior along with signature of weak ferromagnetic interactions. On the other hand, the M– H curves of all the samples sintered in argon atmosphere shows clear hysteresis loop indicating the presence of room temperature ferromagnetism (RTFM) in the samples. The value of magnetization at a particular field increases as content of Mn in the samples increases. The annealing of the samples in the hydrogenated argon further enhances the magnetization and ferromagnetism, whereas the same deteriorates on annealing in oxygen atmosphere. The possible mechanisms of the observed room temperature ferromagnetism have been discussed.

Shear strength measurements of parallel MoS x thin films

The effect of Hertzian contact pressure on the friction coefficient of parallel MoS x films was investigated by sliding sapphire and AISI 52100 steel against parallel MoS x -coated AISI 440C steel under a wide range of contact loads. Mean initial Hertzian contact pressures in the range 0.493–1.258 GPa were created between balls and parallel MoS x -coated 440C disks by varying the applied load and the elastic moduli of the balls. The friction coefficient decreased with the increasing load. Using the Hertzian contact model, we estimated that the shear strength of parallel MoS x films was approximately 40 MPa. This value is higher than that obtained with the usual lamellar MoS 2 films. An explanation in terms of an increasing reactivity of basal surfaces in parallel films is given. The effect of gaseous environment on friction measurement was also studied by varying the atmosphere conditions. For this purpose, friction tests were performed in open air and in dry Argon (Ar). The friction coefficient was shown to increase in the presence of water vapour. The shear strength increased with humidity from 40 MPa up to about 80 MPa. An explanation, taking into account the deformation microstructures that have been developed during sliding, is proposed.

Effect of gaseous environment on the corrosion of β-sialon materials

This paper reports the effects of different gaseous environments on the corrosion behaviour of β-sialon materials. Six β-sialon materials with z-values of 0.2, 0.5, 1.0, 1.5, 2.0 and 3.0 were prepared by pressureless sintering. Corrosion results obtained at 1350 °C in environments comprising (i) Laboratory air; (ii) Argon — 20% oxygen — 2% chlorine; (iii) hydrogen — 10% hydrogen sulphide — 2% water vapour and (iv) nitrogen — 15% carbon dioxide — 4% oxygen — 0.2% sulphur dioxide showed that for each of the four environments the z = 3.0 material exhibited the best corrosion resistance. The mechanism of corrosion at 1350 °C in each of the four environments involves the formation of large volumes of low viscosity liquid phases. These large volumes of liquid enable the solution of β-sialon grains to occur and it is this process which is responsible for corrosion.

The effect of gaseous environment on electronic properties of inorganic linear-chain compound

The preliminary results upon the action of gaseous environment on electronic properties of CDW-bearing system are presented and discussed. The room temperature conduction of NbS 3 have been found to change remarkably under influence of ammonia-argon mixtures (1÷ 90% NH 3), growing at low ammonia concentration with a subsequent drop at NH 3 concentration exceeding 30 %. The resistance changes seems to be fully reversible under present experimental conditions. On the time scale two distinctly different processes are observed: a rapid process associated with a surface adsorption and a slow one, which may be tentatively interpreted as an intercalation of NH 3 into NbS 3 lattice. An unusual behavior of NbS 3 conduction in ammonia environment implies that a CDW system is likely involved into a process.

Effects of gaseous environment and temperature on the storage behaviour of Listeria monocytogenes on chicken breast meat

Portions of skinless chicken breast meat (pH 5.8) were inoculated with a strain of Listeria monocytogenes and stored at 1, 6 or 15 degrees C in (1) aerobic conditions; (2) 30% CO2 + air; (3) 30% CO2 + N2; and (4) 100% CO2. When samples were held at 1 degree C the organism failed to grow under any of the test conditions, despite marked differences between treatments in spoilage rate and ultimate microflora. At 6 degrees C counts of L. monocytogenes increased ca 10-fold in aerobic conditions before spoilage of the meat, but only when the inoculum culture was incubated at 1 degree C rather than 37 degrees C. In CO2 atmospheres growth of L. monocytogenes was inhibited on meat held at 6 degrees C, especially under 100% CO2. By contrast, storage at 15 degrees C led to spoilage of the meat within 2 d, in all gaseous environments, and listeria levels increased up to 100-fold. Differences in the behaviour of L. monocytogenes on poultry and red meats are discussed.

Forming of powder DC electroluminescent displays. I. Characterisation and effects of gaseous environment

Brightness and electrical characteristics of powder DCEL displays have been systematically measured during both the forming operation and simulated life testing. Of particular interest and novelty are the effects of different gaseous environments on display behaviour. Forming in inert or reducing gases is slow and a new phenomenon of 'sticking' is reported where the forming rate reduces to extremely low values (<0.02 V h-1) with an associated decrease in quantum efficiency. A new mechanism for forming is proposed centred around a changing effective barrier height for electron injection, and it is concluded that the width of the formed layer does not change during most of the forming process, contrary to previous theories. This new mechanism also operates during pulsed DC life testing of the panels which displayed the best maintenance characteristics.

Effect of gaseous environment on the kinetics of the initial stage of sintering of single-crystalline nickel oxide

Experiments have confirmed the validity of Eq. (1) and hence the correctness of the method of investigating the sinteringkinetics of spheroidized particles based on electrical conductivity measurements. In the temperature range investigated single-crystalline nickel oxide sinters better in argon than in air, but the mechanisms of mass transfer and energies of activation in both cases are virtually identical. In both gases the kinetic dependence of the initial stage of sintering was found to be of the form x3R ∼ t.

The Effect of Gaseous Environment on the Low Cycle Fatigue Behavior of Ni-Cr-W Alloys for HTGR

Low cycle fatigue behavior of two Ni-Cr-W alloys (KSN and 113MA) was investigated at 1 273K in the simulated High Temperature Gas-cooled Reactor (HTGR) helium, He-2. Both alloys showed little cyclic hardening in fatigue tests and failed with a completely intergranular manner. Although the fatigue life (Nf) of 113MA was a little longer than that of KSN, observed intergranular fractures indicated that the fatigue properties of both alloys were severely influenced by impurities in He-2.As well as in He-2, fatigue tests of KSN and 113MA were carried out in pure He, air and vacuum. The results clearly showed that, regardless of the concentration of reactive gases, both alloys failed intergranularly with short Nfs in gas environments, as compared with the transgranular fracture with long Nf in vacuum. A minor effect of impurity contents was shown as an increase in Nf when substituting air by He-2 and then by pure He. It is considered from these behaviors that the fatigue fractures were affected by residual oxygen gas in the environments penetrating into the specimens along the grain boundaries.

Effect of oxidizing environment on the strength of H451, PGX and IG-11 graphites

The effect of gaseous environment on the compressive and tensile strengths of H451, PGX and IG-11 graphites has been examined. Oxidation was carried out in O 2-, CO 2- and H 2O-containing environments. The strength losses incurred by H451 and IG-11 graphite did not appear to be affected by the nature of the oxidizing gas. However, the strength loss incurred by PGX graphite appeared to be greater in O 2 than in CO 2 or H 2O. A mechanism consistent with the observed behavior of PGX graphite is proposed: the iron impurity, which is locally distributed in the binder, may be catalytically active during oxidation in CO 2 or H 2O, leading to formation of a few large pits, whereas oxidation in O 2 may lead to the more detrimental condition of a high density of small pits. No effect of reaction temperature on the strengths of the graphites was observed. Attempts to fit strength-burnoff data to a standard expression were only partially successful. Much improved fits were obtained when this expression was modified to account for the development of the micro/mesopore network during oxidation.

The effects of gaseous environments on polymers

The effect of inert gases on the mechanical properties of polymers is very general. There are certain areas which have not been explored, such as fatigue and crack propagation. The pressure range above one atmosphere has not been observed. The effects of stress on the diffusion of these gases are not known. The question of how much is a surface effect and how much is subsurface plasticization is not clear. The effects of gases other than N 2, Ar, O 2, and CO 2 have not been determined.

The effects of gaseous environments on the wear of commercial purity titanium

The effect of several gaseous environments on the wear of commercial purity titanium has been investigated with the aid of the scanning electron microscope. Hydrogen, nitrogen and laboratory air have been used in both the extremely dry and the humid conditions. Changes in wear susceptibility by variations in environment change the basic mechanisms of wear asperity deterioration (particle formation). Increased wear rate in dry hydrogen is due to an accelerated surface fatigue mechanism. The three gases produce essentially the same wear characteristics when sufficient water vapor is present. This is attributed to the adsorption characteristics of the wear couple-environment system resulting in severe wear by surface deterioration due to enhanced adhesion.

A Thick Film Platinum Resistance Thermometer

A novel temperature detector, known as Matthey Thermafilm, has been developed. It consists essentially of a platinum film firmly bonded to a ceramic substrate. The film is protected from the possible corrosive effects of gaseous environments by an overglaze of impervious, electrically insulating glass, forming a device that is mechanically and thermally robust. Since the sensing unit generally does not require further protection by encapsulation in a metal or ceramic sheath, it responds very rapidly to thermal changes. The construction of the detector renders it eminently suitable for monitoring transient thermal changes in most environments.

Cryogenic crazing of crystalline, isotactic polypropylene

Stress crazing is studied in crystalline, isotactic polypropylene (PP) at liquid nitrogen temperatures, in smectic PP as well as in monoclinic PP having spherulites of diameter 50–100 μm. The crazes are quite different in these two cases. In smectic PP they are extremely long, often traversing the entire width (0.5 cm) of the sample, straight, perpendicular to the stress direction, and generally very similar to crazes in glassy, amorphous polymers. In monoclinic PP, crazing occurs not along the boundaries between spherulites but along spherulite diameters that are only roughly perpendicular to the stress direction. In general, the length of a craze equals the spherulite diameter, although there is a tendency for crazes to run from one spherulite center to the next. A dramatic effect of gaseous environment on mechanical properties and the extent of crazing is observed. Gases near their condensation temperatures act as crazing agents in the sense that they reduce the stress required to promote crazing up to twofold as compared to the crazing stress in vacuum; also they increase the plastic strain due to crazing about tenfold in smectic, and somewhat less in monoclinic PP. The action of the gas is due to two mechanisms. First, the adsorbed gas reduces the surface energy of the polymer and so eases the creation of new surface in the holes and voids of the craze. Second, the gas becomes highly absorbed at the tip of an incidental flaw or of an existing craze, since these are regions of high dilatant stress; hence the gas acts as a plasticizer easing the flow involved in the nucleation and growth of the craze.

Silicon nitride-nickel compatibility: the effects of environment

The effect of gaseous environment on the high temperature stability of nickel-coated silicon nitride whiskers has been investigated. Under vacuum conditions above 900°C, the nickel coatings broke up to form spheroidal particles, which subsequently became faceted (activation energy = 26 kcal/mol) and wetted the whiskers (activation energy=74 kcal/mol) In addition, at 1100° C, whisker disintegration occurred rapidly due to the formation of a nickel suicide reaction product. Under similar conditions in a nitrogen atmosphere the whiskers remained coherent and in an argon atmosphere the whiskers developed side growths. These results are correlated with variations in the nitrogen and oxygen partial pressures between the various conditions.

62. The effect of gaseous environment on flexural strength of graphite

62. The effect of gaseous environment on flexural strength of graphite

The effects of gaseous environments on the growth and metabolism of fungi

The effects of gaseous environments on the growth and metabolism of fungi