Initial Carbon Content Research Articles

Influence of coke formation on the aromatization of isophorone

The effect of coke formation on the aromatization of isophorone to 3, 5-xylenol is studied on alumina and two carbon-covered aluminas of 12 wt.-% and 18 wt.-% carbon, acting as catalysts in the reaction temperature range 673–808 K. Coke formation, which is amorphous in nature, is found to have a beneficial role in improving the selectivity for aromatization and also in decreasing the decomposition of isophorone. The decomposition decreased with the decrease in surface acidity. Selectivity for 3, 5-xylenol improved with the initial carbon content and is observed to be higher on the 18 wt.-% carbon-covered alumina catalysts.

Evaluation of Carburization and Decarburization Behavior of Fe-9Cr-Mo Ferritic Steels in Sodium Environment

Carburization and decarburization behavior in sodium have been examined for Fe-9Cr-Mo ferritic steels exposure to flowing sodium with containing 0.0049, 0.016 and 0.16 wppm carbon at temperatures between 723 and 873 K. The Fe-9Cr-Mo ferritic steels were more resistant to carbon transfer than 2 ¼ Cr-lMo steel. The carbon transfer and its gradient in Fe-9Cr-Mo ferritic steels was closely related with carbon concentration in sodium, and carburization and decarburization behavior depended on the sodium conditions. In the case of the application of Mod. 9Cr-lMo steel to heat transfer tubes of steam generator of LMFBR, carburization behavior was observed on the conditions that sodium inlet temperature was 778 K and carbon concentration in sodium was 0.01~0.10 wppm. The mean carbon contents of heat transfer tubes after the operation of the steam generator for 200,000 h were estimated to be about 0.103~0.148 wt% comparing with initial carbon contents of 0.10 wt%. Consequently it is expected that high-temperature ...

Evaluation of Carburization and Decarburization Behavior of Fe-9Cr-Mo Ferritic Steels in Sodium Environment.

Carburization and decarburization behavior in sodium have been examined for Fe-9Cr-Mo ferritic steels exposure to flowing sodium with containing 0.0049, 0.016 and 0.16 wppm carbon at temperatures between 723 and 873 K. The Fe-9Cr-Mo ferritic steels were more resistant to carbon transfer than 2 ¼ Cr-lMo steel. The carbon transfer and its gradient in Fe-9Cr-Mo ferritic steels was closely related with carbon concentration in sodium, and carburization and decarburization behavior depended on the sodium conditions. In the case of the application of Mod. 9Cr-lMo steel to heat transfer tubes of steam generator of LMFBR, carburization behavior was observed on the conditions that sodium inlet temperature was 778 K and carbon concentration in sodium was 0.01~0.10 wppm. The mean carbon contents of heat transfer tubes after the operation of the steam generator for 200,000 h were estimated to be about 0.103~0.148 wt% comparing with initial carbon contents of 0.10 wt%. Consequently it is expected that high-temperature strength of Mod. 9Cr-lMo steel would retain sufficient strength and ductility for such operating conditions.

Flow Reactor Studies of Carbon Monoxide/Hydrogen/ Oxygen Kinetics

Abstract New data on the kinetics of CO/H2O/O2 and H2/O2 mixtures in the temperature range of 852—1138 K and at I atmosphere pressure are reported. The data were obtained from adiabatic. constant pressure flow reactor experiments for variations in the initial carbon, hydrogen, and oxygen contents of the mixture and also for variations in the initial temperature. In particular, the results define explosion limit temperatures for near stoichiometric mixtures of CO/H2O/O2 and H2/O2 systems at atmospheric pressure without the presence of surfaces and also demonstrate the complex relationship between water vapor concentration and the carbon monoxide oxidation rate.

Studies on Bacillus thuringiensis H-14 strains isolated in egypt?IV. characterization of fermentation conditions for ?-endotoxin production

Fermentation media formulated from inexpensive locally available ingredients, namely soya meal, Proflo (a partially defatted cooked cottonseed fiour) and molasses, were assessed for growth, sporulation and δ-endotoxin production, by a mosquito-toxic strain of Bacillus thuringlensis H-14 locally isolated in Egypt, using an 8 I working volume fermenter. The insecticidal activity was assayed against Culex piplens. Good growth and sporulation were obtained with all the tested medium combinations, but a medium composed of 3% (w/v) soya meal and 1% (w/v) molasses was the best for δ-endotoxin production. The optimal batch cultivation conditions with respect to aeration (0.37 to 0.62 vol/vol min(-1)), agitation (200 rev/min), pH (6.5 to 7.5), temperature (30°C) and initial concentration of carbon (1% w/v) and nitrogen (3% w/v) sources are also presented. This investigation shows that these locally available ingredients could be used for the production of low-priced mosquito larvicide in Egypt and other developing countries where these ingredients are avallable.

Transport restriction effect for gaseous components on the carbon content of LEC GaAs

Gas convection above B 2O 3 was restricted using a quartz cap over the crucible to examine the gas transport effect on the carbon content of LEC GaAs crystals. It has been found that the carbon content of crystals grown with a cap closing the crucible is much larger than that of crystals grown without a cap. Also, a BN cylinder was introduced in a puller to reduce the interface area between GaAs melt and B 2O 3, and between B 2O 3 and the ambient gas. Estimates of carbon extraction rate from the melt were made by gas analysis in the puller which was operated in a hypothetical pulling process with different cylinder diameters. In addition, the dependence of the carbon concentration in polycrystalline GaAs remaining in the crucible on the pass time from the start of heating was investigated. The results suggest not only that the rate of carbon extraction is faster than incorporation, but also that the initial carbon content of the starting charge affects the carbon content of the grown crystal. It has been concluded that the extraction rate of carbon from the melt as well as the initial carbon content of the starting charge are significant factors in estimating the actual distribution of carbon concentration along the growth direction of LEC GaAs.

Genesis of sediment-hosted copper mineralization in south-central Kansas; sulfur/carbon and sulfur isotope systematics

Copper sulfide mineralization occurs within reduced sedimentary rocks of the Permianage Wellington Formation and Ninnescah Shale in south-central Kansas. There are two distinct sulfide assemblages. Pyrite-digenite is found in gray-green shale units within red beds of the Ninnescah Shale. Chalcopyrite, bornite, and chalcocite occur in carbonate units within the upper Wellington Formation to lower Ninnescah Shale transition. Digenite occurs as a replacement of pyrite whereas copper sulfides in carbonate units occur in vugs and small fractures. Chalcocite and barite fill vugs in carbonates occurring within red bed-dominated stratigraphy, whereas the assemblage calcite-chalcopyrite-bornite is prevalent in veinlets within carbonate units situated near a major stratigraphic color change from underlying gray units to red beds.Sulfide sulfur and organic carbon concentrations are generally low (<0.2 wt % for both) in Cu sulfide-bearing rocks. It is possible that initial organic carbon and sulfide sulfur contents were low prior to copper mineralization or that there was interaction between an oxidized, Cu-bearing fluid and reduced, organic carbon-bearing sediments. The delta 34 S values for pyrite range from -40 to -26 per mil. Digenite replacing pyrite is characterized by a similar range in delta 34 S values, whereas chalcopyrite, bornite, and chalcocite in carbonate hosts are significantly heavier, with a range in delta 34 S values of -19 to -7 per mil. Textures of mineralized rocks, S/C relationships, and delta 34 S values probably reflect digenite-pyrite mineralization involving sulfur-conserving replacement reactions, whereas sulfide deposition in carbonates followed partial reduction of sulfate (delta 34 S value near 11ppm) contained in the Cu-bearing fluid. Sulfide mineral distribution and copper contents of reduced and oxidized sedimentary rocks suggest that large-scale fluid infiltration was minimal and that mineralization resulted from small-scale fluid migration within the sedimentary column.

Observations on the feeding of Euphausia lucens on natural phytoplankton suspensions in the southern Benguela upwelling region

Grazing rates by Euphausia lucens on natural phytoplankton assemblages from four stations in the southern Benguela region were measured by three different techniques: disappearance of Chl a, particle size and volume distributions and inverted microscope counts of the various phytoplankton taxa. All three methods yielded comparable results for overall clearance rates, with the Coulter Counter giving the lowest and the inverted microscope the highest rates (range 1.13–3.04 ml mg dry wt −1 h −1). The Coulter Counter data indicated that particles 50 μm were filtered at significantly greater rates than the other size classes, whereas inverted microscope counts showed that cells 10–20 μm (maximum dimensions) as well as 50 μm were filtered at significantly greater rates than the other cells. Clearance rates were calculated for each of the phytoplankton species categories and compared by means of ANOVA. Dinoflagellates and pennate diatoms were found to be filtered at significantly higher rates than the other cells. It was also noted that the mean number of cells per Chaetoceros chain did not differ in experimental and control bottles. This implies that entire chains were consumed and that they were not fragmented into smaller chains through the grazing activity of the euphausiids. Ingestion rates, in terms of carbon, were calculated for each of the algal species groups. It was found that in all four experiments, the amount of carbon ingested in the form of dinoflagellates was proportionally greater than one would expect from initial carbon concentrations alone. This was attributed to the high clearance rates on these cells, their greater dimensions and higher carbon content per unit cell volume. It was concluded that dinoflagellates play an important role in the Benguela upwelling region, despite the fact that it is a diatom-dominated system.

Sorption of the Pesticide Aldicarb by Soil: Its Mobility Through a Saturated Medium in the Presence of Dissolved Organic Matter

Abstract Adsorption characteristics of the radiolabeled pesticide aldicarb (2-methyl-2-(methyl-14C-thio)-propionaldehyde-O-methycarbamoyO-oxime) on loamy sand and its mobility through a water-saturated soil column were studied. This study emphasizes the effect of soil organic carbon content and of dissolved humic materials on the sorption characteristics of aldicarb. Dissolved humic substances at 25 mg/L present a very small binding affinity for aldicarb (“association constant” ≈ 20 [nmol/g carbon]/[nmol/g water]) and do not significantly affect the sorption rate for this pesticide. Freundlich isotherms were determined for aldicarb sorption on the original soil (% o.c. = 2.2) and on soil samples treated to reduce the initial soil organic carbon content (% o.c. = 0.8). If linear isotherms are assumed, the adsorption coefficient KD is nearly three-fold higher for the original soil than for the treated soil samples. The ratios of the KD values obtained for adsorption in the presence and in the absence of dissolved humic substances (25 mg/L) were 1.3 and 1.4, respectively, for the original and for the treated soil samples: this indicates that humic substances could modify only slightly aldicarb transport in soil. Effluent concentration profiles for the movement of the radiolabeled pesticide through a 30-cm long saturated soil column indicate a retardation factor R = 1.4. This R value is related to hydrolysis product of aldicarb, since no detectable parent compound was found in the column effluent. Results showed 45% loss of the initial radioactivity applied on the soil column: this could be attributed to irreversible adsorption and to biodegradation of the pesticide compounds.

The kinetics of decarburization of iron melts by argon-hydrogen plasma jets.

A plasma-torch and refractory-lined furnace with a 20kg capacity were used to study the kinetics of decarburization of iron melts. Molten iron with an initial carbon content of either 1.1 or 2.6wt% was decarburized using an argon-hydrogen plasma jet. The rate of decarburization was found to be limited by mass transfer in the melt; a mass transfer coefficient of 2.76×10-3cm/s was obtained. Additionally, it was determined that the decarburization reaction occurred only in the region of plasma jet impingement.

Detonation-induced coal gasification

A preliminary experimental and theorotical investigation of the feasibility of detonation-induced pulverized coal gasification is described. The concept envisions a closed annular detonation duct through which a hydrogen/oxygen gasphase detonation propagates continuously. Coal particles injected into the violent and rapidly changing atmosphere produced by the detonation would undergo gasification reactions and be subsequently expelled from the duct. These events would occur in a time period compatible with one revolution of the detonation. A one-dimensional analysis of the response of a single coal particle within the expansion-wave region behind the detonation front is presented. Independent variables include particle diameter, initial H2/O2 stoichiometry and expansion wavelength (at the time the particle is overtaken by the detonation front). The most significant result of this analysis is the prediction of relative gas/particle velocities ranging between 125 and 1500m/s, which are sustained throughout particle residence times of 1–15 ms corresponding to 10–1000 μm diameter particles. An experimental facility comprising a 47 m ‘single-shot’ detonation duct that was built for this study is discussed. The duct was 2.54 cm square and was terminated at each end by a 0.36 m diameter × 2.44 m long cylindrical tank which contained helium gas during a test. Sized coal particles were placed at a point within the first 3.7 m length of the duct, and thin brass diaphragms initially separated the duct from the two helium-filled tanks. Detonation was initiated at the duct, end closest to these particles. The diaphragm at that end burst, allowing combustion and gasification products to exhaust into the adjoining tank where they were quenched and decelerated. When the detonation reached the far end of the duct the second diaphragm burst, minimizing wave reflections which would otherwise return to the ‘test section’ end and interfere with the flow field there. After a test the contents of both tanks and the duct were circulated and mixed. A gas sample was then drawn and analysed for yield. Results from preliminary experiments using this facility are presented. Although too few tests were conducted for conclusive observations to be reported, in two experiments yields of CO + CH4 representing 40 per cent of the total initial carbon content in the coal samples were obtained.

Polymerization kinetics in dental acrylics.

Abstract The polymerization kinetics of 3 dental acrylic resins (tray material, crown and bridge resin and lining material) were studied by FTIR techniques and were found to follow first order kinetics. Tray material and crown and bridge resins had lower rate constant and degree of polymerization at initial set compared with lining material. The initial intensity of the absorbance peak at 1640 cm −1 which is proportional to the initial concentration of carbon to carbon double bonds in the monomer is calculated by extrapolation of the regression line of log intensity vs time. The residual monomer in the resins was then determined. Lining material had lowest degree of polymerization (88%) at 24-h set compared with tray material and crown and bridge resins (95–96%).

CHANGES IN SOIL CARBON STORAGE AFTER CULTIVATION

Previously published data from 625 paired soil samples were used to predict carbon in cultivated soil as a function of initial carbon content. A 30-cm sampling depth provided a less variable estimate (r2 = 0.9) of changes in carbon than a 15-cm sampling depth (r2 = 0.6). Regression analyses of changes in carbon storage in relation to years of cultivation confirmed that the greatest rates of change occurred in the first 20 yr. An initial carbon effect was present in all analyses: soils very low in carbon tended to gain slight amounts of carbon after cultivation, but soils high in carbon lost at least 20% during cultivation. Carbon losses from most agricultural soils are estimated to average less than 20% of initial values or less than 1.5 kg/cm2 within the top 30 cm. These estimates should not be applied to depths greater than 30 cm and would be improved with more bulk density information and equivalent sample volumes.

Parameters Affecting the Postshock Wave Relaxation Zone in an Oxygen Carbon Particle Suspension

A parametric study was conducted regarding the effects of the initial carbon concentration, the initial carbon particle diameter, the shock wave Mach number and the preshock suspension pressure on the suspension behavior in the relaxation zone. The suspension was composed of oxygen gas seeded with small carbon particles. It was found that changing either the initial carbon concentration or the shock wave Mach number has a marked effect on the suspension behavior in the relaxation zone and on the eventually reached postshock equilibrium state. Changes in the initial carbon particle diameter (at a constant shock wave Mach number and carbon concentration) has no effect on the postshock equilibrium state, but it does affect the way in which the suspension reaches this equilibrium state. Changes in the preshock suspension pressure has only minor effects on the suspension behavior in the relaxation zone.

Role of bacteria in decomposition of faecal pellets egested by the epiphyte-grazing gastropod Gibbula umbilicaris

The significance of the microheterotrophic utilization of faecal pellets derived from Gibbula umbilicaris — one of the most important gastropod species in the Posidonia oceanica ecosystem around the Isle of Ischia (Italy) — was investigated by means of microcosm-experiments. Initial total organic carbon (TOC) content of faecal pellets was 32 μgC (mg faeces dry wt)-1 and declined continuously over a 2-month incubation period. The low values of TOC coincided with SEM observations of pellets which were found to consist mainly of diatom frustules and other slowly utilizable material. In a long-term experiment freshly egested faecal pellets were rapidly colonized by bacteria, which reached densities of up to 14x105 cells (mg faeces dry wt)-1 within 12 h. Thereafter bacterial numbers declined and fluctuated in a very narrow range between 2 and 3.5x105 cells (mg faeces dry wt)-1 during the two months of the investigation period. In short-term experiments (over 5 d) similar trends were observed. Peak densities of attached bacteria were followed by a decline of this population. Concurrently the number of free-living bacteria increased. This observation was confirmed by O2 consumption measurements of freshly egested faecal pellets over 24 h, where the highest O2 consumption rates were obtained after 12 h, followed by a rapid decline, thus supporting the view that detachment of bacteria may occur. Moreover, the respiration data indicate that about 4% of faecal TOC are remineralized within the first day.

CaC&lt;SUB&gt;2&lt;/SUB&gt;による溶鋼の不純物除去

In order to reduce the susceptibility to embrittlement of steels such as a rotorshaft for power plant, which are to be used at high temperatures, experiments were carried out on the optimum conditions for the removal of tramp elements like Sn, Sb and As by the addition of CaC2. Industrial scale tests were also carried out, based upon the experimental results obtained. The results obtained can be summarized as follows.(1) These impurities can be removed by reduction, and the reduction was accelerated by the rapid decomposition of CaC2 at low initial carbon content and high temperatures.(2) The amount of impurities removed was found to be proportional to the increase in carbon content during reaction and the initial impurity content. The proportional constant increased in the order of Sn, P, Sb and As.(3) It was found from the industrial scale tests that the impurities could be favorably removed by using Ar stirring from the bottom of the ladle and by using CaC2 injection increasing the reaction surface area.

Thermal Cleaning of InSb Surfaces in an Ultrahigh Vacuum

In and Sb surfaces of (111) crystals were analyzed by Auger electron spectroscopy (AES) before, during, and after heating them in an ultrahigh vacuum system. Heating the samples to 450°C resulted in stoichiometric and oxygen‐free surfaces. Sulfur due to chemical precleaning is removed at 470°C. Further, if the initial carbon concentration is low enough (< 10% surface coverage), then it can be almost totally removed by thermal cleaning at 450°C.

Rate of decarburization of iron-carbon melts: Part I. experimental determination of the effect of sulfur

The kinetics of decarburization of iron-carbon melts with CO-CO2 gas mixtures were investigated at 1700 ° using the levitation technique. The influences of different experimental variables on the decarburization kinetics were determined. It was found that sulfur has a clear and reproducible retarding effect on the decarburization of iron-carbon melts; and this effect is most pronounced at sulfur concentrations in the range of 0 to 0.05 wt pct. The initial carbon concentration has no discernible effect on the decarburization kinetics. Melts containing 2.48 wt pct C and 0.92 wt pct C initially were found to decarburize at virtually identical rates until a substantial portion of the carbon was removed. The decarburization rate of a melt with a specified initial carbon content was found to remain essentially constant until the carbon content fell to a characteristic level below which the rate tended to level off. The partial pressure of CO2 of the gas mixture has a marked effect on the decarburization kinetics. The flow-rate of the gas mixture has a small but finite effect on the rate of decarburization.

Carbon and the Kinetics of Oxygen Precipitation in Silicon

ABSTRACTOxygen precipitation in Czochralski silicon has been studied as a function of anneal time, oxygen concentration and carbon concentration using FTIR. It was found that the oxygen supersaturation controls the precipitation kinetics in high oxygen content samples, whereas the carbon concentration is of prime importance in low oxygen content samples. The decrease in sustitutional carbon concentration after nucleation and its subsequent increase with extended growth anneals supports the view that carbon affects precipitate nucleation, but not precipitate growth. The measured oxygen solubility at 1000°C was found to depend on both the initial oxygen concentration and the initial carbon concentration.

The dependence of char and carbon yield on lignocellulosic precursor composition

A set of lignocellulosic precursors of widely varying composition was pyrolyzed under argon at 15°C/min to 500°C. Variation in the total mass and carbon yields among precursors was found to be due to variation in composition, i.e. distribution of the main organic components (lignin, holocellulose and extractives). Simple models for total mass and carbon yields of the precursors allowed determination by multiple regression analysis of the total mass and carbon yield of the components pyrolyzing in their native state in the lignocellulosic matrix. The component yields thus estimated were compared to results observed in studies of isolated components, such as reagent-grade cellulose. The char yield from lignin (53%) was found to be three times that of cellulose (18%) because of the higher initial carbon content in lignin (63 vs 44%) as well as the higher carbon yield (76 vs 40%).