Increase In Sulfur Content Research Articles

Pyrolysis of cobalt and caesium doped cationic ion-exchange resin

The aim of this study is to monitor the residual content of carbon, sulphur, cobalt and caesium from a cationic ion-exchange resin, Amberlite IRN 77, under pyrolysis. Resin samples were heated at five temperatures (350, 385, 400, 450 and 550°C), under nitrogen atmosphere for 30 min. For the commercial resin (undoped resin), a high residual carbon content (96% at 400°C and 90% at 550°C) was observed, in contrast with the residual sulphur content (33% at 350°C and 23% at 550°C). In the presence of cobalt and caesium, a decreased carbon content (91% at 400°C and 65% at 550°C) and, on the other hand, an increased sulphur content (74% at 350°C and 48% at 550°C) were found. As far as doped elements are concerned, a ‘critical temperature’ of 400°C seems to be a limit beyond which it is impossible to guarantee that 100% of these two elements remain within the solid residue.

Structural and photoluminescence study of the quaternary alloys system CuIn(S xSe 1− x) 2

The full composition range CuIn(S x Se 1− x ) 2 alloy system has been studied using 40 mm length crystal cuts from 10 mm diameter ingots grown by the classical Bridgman method. X-ray diffraction diffractographs show that the CuIn(S x Se 1− x ) 2 compounds have a chalcopyrite structure for each composition x, they exhibit an expansion on the unit cell characteristics by the tetragonal distortion which depends linearly on the electronegativity of the atoms. The photoluminescence spectra is investigated as a function of various compositions, temperature and excitation intensities. Photoluminescence spectra shows a wide variation in the dominant peak location and an overall blue shift with the increase of sulphur content. Photoluminescence CuInS 2 and CuIn(S 0.72Se 0.28) 2 have been studied in detail.

Influence of sulphur on the electrical and optical properties of p-type CuIn(SxSe1−x)2 single crystals

The substitution of selenium by sulphur in thin film solar cells still is a challenging topic. The origin of the related disadvantageous electrical properties to date is not well understood. A distinction of effects caused by preparation technology and intrinsic material properties is difficult. Therefore, comparative studies on bulk single crystals should provide valuable information. We grew CuIn(SxSe1−x)2 crystals by the solution Bridgman method using CuSe as a solvent. The crystals were analysed by x-ray diffraction, photoluminescence and Hall-effect measurements and turned out to be of an excellent electrical homogeneity. The temperature dependent carrier concentrations can be well explained by assuming a two acceptor and one donor model. The activation energies of the acceptor levels clearly shift to higher values when selenium is substituted by sulphur. This is confirmed by photoluminescence measurements, which reveal an acceptor to band edge transition shifting to higher energies with increasing sulphur content.

Effects of sodium sulphate and potassium chloride fertilizers on the nutritive value of timothy grown on different soils

Third harvest samples from a pot experiment were analysed to study the effects of sodium (Na) (0, 200 and 400 mg dm-3 of soil in a single application as Na2SO4 . 10H2O) and potassium (K) application (0, 100 and 200 mg dm-3 applied at each harvest as KCl) on the nutritive value of timothy grown on three different soil types (clay, loam and organogenic soil). The effects of fertilization on concentrations of crude protein, neutral detergent fibre (NDF) and non-structural carbohydrates, although statistically significant, were relatively minor in absolute terms. Na applications increased and K applications decreased sulphur and phosphorus concentrations, the magnitude of which was dependent on soil type. The increase in sulphur concentration can be attributed to sulphate in Na-fertilizer. The effects of fertilizers on in vitro organic matter digestibility and the potential extent of dry matter (DM) and NDF digestibility were small. Digestion kinetic parameters estimated from fermentative gas production measured using a fully automated system were used in a rumen simulation model to estimate digestibility. Total gas volume and the rate of gas production from the rapidly digestible fraction were negatively correlated with timothy S and N concentrations. Na application had no effect, but K application increased true rumen DM digestibility, the effect being most profound on organogenic soil. The results suggest that Na application does not elicit substantial positive effects on the nutritive value of timothy which has often been reported for perennial ryegrass, but K application can improve the nutritive value of timothy grown on K deficient soil.;

XPS, AES and ToF-SIMS investigation of surface films and the role of inclusions on pitting corrosion in austenitic stainless steels

Chemical inhomogeneities (inclusions) present in the alloy are known to affect the stability of the passive film on stainless steels in the presence of chloride ions. In this work, three surface analytical techniques— XPS, AES and time-of-flight SIMS (ToF-SIMS)— have been used to characterize the surface films formed on stainless steels following mechanical polishing and immersion in an aggressive 6% FeCl3 solution, which is utilized for testing the pitting corrosion resistance of stainless steels. Two 18Cr8Ni stainless steels were investigated: one with a low sulphur content, DIN 1.4301 (0.003% S), and one with a high sulphur content, DIN 1.4305 (0.29% S). The XPS results show that the surface films on both steels are composed of mixed iron–chromium oxyhydroxides with a higher chromium content compared to the bulk composition. The average passive film composition and the film thickness remained unchanged despite increasing sulphur content in the steel after mechanical polishing. Angle-resolved XPS results suggest the presence of hydroxides in the outer layer of the passive film, which is confirmed by ToF-SIMS its high surface sensitivity. Auger and ToF-SIMS imaging with high lateral resolution allow the inclusions to be characterized: sulphur and manganese maps show the power of imaging SIMS for studying the distribution of elements that are present in very low concentrations. It is shown that on the MnS part of the inclusions no (protective) oxide or hydroxide film is formed after mechanical polishing. This might be the reason for the well-documented role of these inclusions as pit initiation sites. Copyright © 2000 John Wiley & Sons, Ltd.

Phase equilibria in the system Fe-Ni-S at 500.DEG.C. and 400.DEG.C..

Phase equilibria in the system Fe-Ni-S were investigated by dry synthesis at 500°C and 400°C using three elements (Fe, Ni and S) and two synthetic sulfides (FeS and NiS). Phase diagrams of this ternary system at these two temperatures were obtained. The extent of the monosulfide solid solution (mss) is complete at 500°C and 400°C. The d(102)-values of the mss are increasing with the increasing Fe/(Fe+Ni) ratio and are decreasing with the increasing sulfur content of the mss. Pentlandite has the solid solution areas ranging from (Fe0.66Ni0.34)9.02S8.00 to (Fe0.30Ni0.70)9.35S8.00 at 500°C and from (Fe0.70Ni0.30)9.39S8.00 to (Fe0.41Ni0.59)9.24S8.00 at 400°C. Violarite has the solid solution area ranging from (Fe0.16Ni0.84)3.02S4.00 to (Fe0.34Ni0.66)3.00S4.00 at 400°C and does not exist at 500°C. Godlevskite is stable at 400°C and it transforms to α-Ni7S6 phase at 500°C run. Tie lines of pentlandite to godlevskite at 400°C and pentlandite to α-Ni7S6 phase at 500°C are stable. On the Fe-Ni join, two kinds of Fe-Ni alloys (α-iron and γ-phase) and pure nickel are stable. Alfa-iron has a body-centered cubic structure and pure nickel has a face-centered cubic structure. Gamma-phase has a primitive tetragonal structure and the FeNi3 phase is included in the γ-phase solid solution.

Optical properties of the quaternary alloy system Culn(SxSe1−x)2 investigated by spectroscopic ellipsometry

Experimental results for the pseudodielectric function 〈ε〉 of CuIn(SxSe1−x)2 alloy system are reported. The investigation has been performed on the full composition range using crystals cut from ingots of 10 mm diameter and 40 mm length. The ingots were grown using the classical Bridgman method. Ellipsometric measurements were performed at room temperature in the range 1.5–5.5 eV. The energies of critical points have been determined from the imaginary part of the dielectric function. The transition energies (E1, E2, E3, and E4) are found to shift linearly to higher energies as the sulfur content increases. The copper d level is found to be dominant in the ranges 2.5–3.5 eV for CuInSe2 and 2.8–4 eV for CuInS2.

Mechanical properties of PVC/SBR blends compatibilized by acrylonitrile‐butadiene rubber and covulcanization

AbstractThe mechanical properties of poly(vinyl chloride) (PVC)/styrene‐butadiene rubber (SBR) blends compatibilized by acrylonitrile‐butadiene rubber (NBR) were studied. A sulfur curing system was employed to crosslink the rubber of the blends. In the case of the blends without any curing agents, an increase in NBR content did not improve the tensile strength and elongation‐at‐break. However, a significant improvement in the mechanical properties was observed when NBR was added as a compatibilizer and the blend was vulcanized. In the PVC/NBR/SBR (50/10/40) blends, the tensile strength and elongation‐at‐break increased with an increase in sulfur concentration. This improvement was attributed to covulcanization between NBR and SBR. The fracture toughness of PVC/NBR/SBR (50/10/40) blends was characterized by the critical strain energy release rate, Gc. In the case of the PVC/NBR‐29/SBR (50/10/40) blends, an increase in sulfur concentration resulted in a dramatic increase in Gc. However, the Gc value of PVC/NBR‐40/SBR (50/10/40) blends decreased with an increase in sulfur concentration owing to the brittle behavior of one of the blend components—the PVC/NBR‐40 (50/10) phase.

Dynamic vulcanisation of poly(vinyl chloride)–epoxidised natural rubber thermoplastic elastomers

Plasticised poly(vinyl chloride)–epoxidised natural rubber (PVC–ENR) thermoplastic elastomers (TPEs) were prepared by melt mixing in a Brabender Plasticorder at 150°C and a rotor speed of 50 rev min-1. Curative concen tration was progressively increased from 0 to 1 phr in order to study the effect of dynamic curing on the plasticised blend. The mechanical properties investigated include tensile strength, elongation at break, modulus at 100%; elongation, tear strength, hardness, and compression set. The effect of thermo- oxidative aging on the mechanical properties was investigated by exposing the PVC–ENR TPEs in an air oven at 80°C for 168 h. It was found that all physical and mechanical properties increased continuously with increasing sulphur concentration. A steady reduction in swelling index with increasing concentration of curatives is excellent evidence for a significant increase in crosslink density. The thermo-oxidative aging process resulted in a significant enhancement in mechanical properties with the exception of elongation at break. This observation seems to indicate that some microstructural changes, such as the formation of new crosslinks, have taken place in the thermo- oxidatively aged TPEs. This trend is supported by a further reduction in the swelling index of aged TPEs. Qualitative evidence from FTIR was used to support the trend observed in the mechanical and physical properties.

Influence of sulphur on the solubility of graphite in iron melts: a Monte Carlo simulation study

We report a Monte Carlo simulation study of the effect of sulphur on the solubility of graphite in iron melts in the temperature range 1400–1600°C. The atoms in the ternary Fe–C–S system were arranged on a graphitic hexagonal lattice and pairwise interactions between them were assumed to be short ranged. The simulations were carried out using a combination of canonical and grand canonical ensembles for a range of interaction strengths, carbon and sulphur concentrations and temperature. In all simulations, graphite solubility exhibited a linear decrease with increasing sulphur concentration with slopes ranging from −0.4 to −0.6. The experimental values of this slope range from −0.4 to −0.48. The strong bond between Fe and S, which is capable of distorting electron distribution around Fe atoms and affect other bonds made by it, appears to be one of the most important parameters in this model. With no distortion around an Fe atom, there is a general increase in slope values with increasing sulphur interaction strengths (S–S, S–C and S–Fe). However, with a medium or strong distortion around Fe atoms due to the Fe–S bond, the slopes no longer depend on the magnitude of various sulphur interactions and show a rather flat range. The simulated slopes also increase slightly with temperature. The effect of various carbon interactions is also discussed.

The effects of grain-refining precipitates on the development of toughness in 4340 steel

Grain-refining precipitates have been identified as microstructural features that adversely affect the toughness of grain-refined, high-strength steels. For the case of an air-melt, aluminum-killed 4340 steel processed in a conventional manner, the presence of coarse A1N and TiN precipitates is shown to have a deleterious effect on both room-temperature impact toughness and fracture toughness. Coarse A1N precipitates, which evolve during the primary and secondary breakdown of the steel, are largely responsible for the development of quasicleavage fracture at ambient temperatures and the formation of fine-scale microvoids at upper-shelf temperatures. The refinement of grain-refining precipitates provides substantial increases in both lower-shelf and upper-shelf toughness for conditions associated with a critical damage mechanism of fracture. Improvements in upper-shelf toughness specifically result from a change in the species of grain-refining precipitate that nucleates secondary microvoids during the latter stages of fracture, viz. a refinement-induced transition from A1N to smaller TiN precipitates in the microstructure. This refinement-based mechanism of toughening is operative over a broad range of strength, although improvements in the transverse toughness of 4340 steel diminish with increases in sulfur content above 0.01 wt pct.

Dynamic mechanical relaxation of lightly cross-linked natural rubber

The isochronal mechanical relaxation spectra of lightly cross-linked natural rubbers were measured at frequency 1 Hz. The results were analysed using the empirical Havriliak–Negami (HN) equation. The HN equation fitted the relaxation spectra very well. The fitting parameters, α and β, obtained from the data fitting were used to interpret the relation between molecular motions and structure of polymers based on the model proposed by Schönhals and Schlosser. In the high-frequency region of relaxation spectra, the values of αβ were increased with increasing sulphur content. According to the model proposed by Schönhals and Schlosser, it means that the molecular motions are related to the local intramolecular interactions and are mainly influenced by the formation of heterocyclic groups along the chain. However, in the low-frequency region of relaxation spectra, the values of α were not affected by increasing sulphur content. According to the model proposed by Schönhals and Schlosser, the molecular motions in this region are related to the intermolecular interactions. They are not influenced by the level of cross-linking due to the very low level of cross-link.

Kinetics of decarburisation of levitating liquid iron drops by carbon dioxide

Decarburisation experiments were carried out by levitating liquid iron droplets in a flowing gas stream containing carbon dioxide at 1723K. Decarburisation of liquid iron droplets by carbon dioxide can be adequately described by the mixed control of gas phase mass transport and dissociative chemisorption of carbon dioxide. Carbon monoxide in the gas phase does not have any significant effect on the rate of decarburisation. The rate of decarburisation decreases significantly with increase in sulphur content in the melt and this effect can be quantitatively explained using the Langmuir isotherm. Adsorption coefficient of sulphur is found to be 200. Influence of phosphorus and chromium in the melt on the rate of decarburisation is negligibly small.

Polariton reflectance spectra from thin ZnSxSe1−x layers

A study of reflectance spectra from thin ZnSxSe1−x solid-solution layers in the region of excitonic resonances is reported. It has been found that an increase in sulfur concentration in the layers increases the inhomogeneous broadening of the quantized polariton lines. It has been established that the inhomogeneous line broadening in a reflectance spectrum depends on the magnitude of exciton-photon mixing; it is small in the long-wavelength region where the photon component of the polariton is large, and large at short wavelengths where the mechanical component dominates.

Effects of Fuel Properties on Exhaust Emission from DI Diesel Engine.

Exhaust emissions (HC, CO, NO x , PM, and PAH (polycyclic aromatic hydrocarbons in PM)) from a commercial DI diesel engine were measured for petroleum-derived fuels with a wide range of fuel properties. Fuel properties such as cetane number, aromatic content and type, and distillation temperature were adjusted to be independent from each other. The test results showed that total aromatic content was the controlling factor for NO x emission, and PM emission mainly depended on polycyclic aromatic content in the fuel. The increases in PM emission with increase in aromatics was mainly caused by the increase in SOF emission. Both of NO x and PM emissions were seldom affected by cetane number and 90% distillation temperature. Therefore, chemical characteristics of fuel are the controlling factor for NO x and PM emission, not the physical properties. The amount of sulfate in PM proportionally increased with increase in sulfur content of fuel. PAH emission was evaluated by analyzing SOF using a high performance liquid chromatography with a chemiluminesence detector. Also, the PAH highly depended on aromatic content, and the emission characteristics caused by aromatics was quite similar to PM emission.

Decarburization Kinetics of Fe-C-S Droplets with H2O.

Decarburization of liquid Fe-C-S droplets with HO vapour was investigated using the electromagnetic levitation technique. The results indicated that the decarburization of liquid iron droplets by HO vapour can be adequately described by the mixed control of the gas phase mass transport and the dissociative chemisorption of HO at the melt surface. The Steinberger-Treybal correlation equation was found to correctly represent the gas phase mass transfer in the present system geometry and experimental conditions. The rate of decarburization decreased significantly with increase in sulphur content in the melt, and this effect was quantitatively represented by the mixed control model. There exists a residual rate of decarburization at high sulphur contents in the melt. The extent of the residual rate observed can be interpreted as implying that, even at the melt surface of apparent saturation with sulphur, 8-9% of the surface sites are still available for HO molecules to react with carbon. The activation energy of dissociative chemisorption of HO was 95 kJ mol-1.

Sulphur-radical control on petroleum formation rates

Most petroleum is formed through the partial decomposition of kerogen (an insoluble sedimentary organic material) in response to thermal stress during subsurface burial in a sedimentary basin1,2. Knowing the mechanisms and kinetics of this process allows the determination of the extent and timing of petroleum formation, which, in turn, are critical for evaluating the potential for petroleum occurrences within a sedimentary basin. Kinetic models of petroleum generation are derived mainly from pyrolysis experiments1,2, in which it is usually assumed that formation rates are controlled by the strength of the bonds within the precursor compounds: this agrees with the observation that petroleum formation rates increase with increasing sulphur content of thermally immature kerogen2,3,4, C–S bonds being weaker than C–C bonds. However, this explanation fails to account for the overall composition of petroleum. Here I argue, on the basis of pyrolysis experiments, that it is the presence of sulphur radicals, rather than the relative weakness of C–S bonds, that controls petroleum formation rates. My findings suggest that the rate of petroleum formation depends critically on the concentration of sulphur radicals generated during the initial stages of thermal maturation. The proposed mechanism appears to provide a realistic explanation for both the overall composition of petroleum and the observed variation in formation rates.

Electrical and photoelectrical characterization of GaAs xS y polycrystalline thin films

Thin GaAs x S y films are deposited on Mo substrates by reactive radio-frequency sputtering of a polycrystalline GaAs target by adding H 2S to the discharge gas (Ar). We used optical emission spectroscopy and mass spectrometry to study the As-S exchange reaction activity during sputter deposition as a function of different sputtering parameters. The analysis of electrical and photoelectrical properties of the Schottky junctions realised, Mo/GaAsS/Au, shows that with an increase in sulfur concentration there is: • an improvement of the gold/semiconductor interface (decreasing interface index and increasing barrier height); • a significant lowering of grain boundary electrical activities. We have thus prepared a ternary polycrystalline compound GaAs x S y which presents promising electrical and photoelectrical properties, even for films as thin as a few microns with grains of about one micron.

Telencephalin induces spreading of microglia

The synergy effect of naphthenic acid corrosion and sulfur corrosion at high temperature in crude oil distillation unit was studied using Q235 carbon-manganese steel and 316 stainless steel. The corrosion of Q235 and 316 in corrosion media containing sulfur and/or naphthenic acid at 280 °C was investigated by weight loss, scanning electron microscope (SEM), EDS and X-ray diffractometer (XRD) analysis. The results showed that in corrosion media containing only sulfur, the corrosion rate of Q235 and 316 first increased and then decreased with the increase of sulfur content. In corrosion media containing naphthenic acid and sulfur, with the variations of acid value or sulfur content, the synergy effect of naphthenic acid corrosion and sulfur corrosion has a great influence on the corrosion rate of Q235 and 316. It was indicated that the sulfur accelerated naphthenic acid corrosion below a certain sulfur content but prevented naphthenic acid corrosion above that. The corrosion products on two steels after exposure to corrosion media were investigated. The stable Cr5S8 phases detected in the corrosion products film of 316 were considered as the reason why 316 has greater corrosion resistance to that of Q235.

Fabrication and characterization of CuIn(S xSe 1− x) 2 thin films deposited by r.f. sputtering

Thin films of CuIn(S x Se 1− x ) 2 were prepared by r.f. sputtering from powder targets which were previously mixed from powdered binary compounds. X-ray diffraction analyses showed the films had the single phase chalcopyrite structure, and the lattice parameters ( a and c) varied linearly with the increase in sulphur content x from x=0 (CuInSe 2) to x=1 (CuInS 2). The orientation to the (112) plane of the CuIn(S x Se 1− x ) 2 thin films increases as the sulphur content x increases. From scanning electron microscope images, the grain sizes in the films were found to decrease with the decrease in sulphur content. Optical transmittance measurements showed that bowing behaviour is not, observed in the films.