Similar Carbon Content Research Articles

Microstructural Analysis of the Special Steels Produced by Continuous Casting Process

The objective of the present work is to obtain empirical equations allowing the correlation between secondary dendrite arm spacing (SDAS) (λ2) and cooling rates () of the special steels, produced by continuous casting process. For that, samples were extracted from ingots with three different sections, i.e., 150 × 150 mm, 180 × 180 mm, and 240 × 240 mm, choosing steels with nine different chemical compositions (equivalent carbon contents). Metallographic techniques to reveal the structures, acquisition data system, and image analysis were employed to determine the SDAS in function of its position from surface to center of the ingots. Computer simulations generated by the continuous casting process software (InALC + Artificial Intelligence in the Continuous Casting), developed by the research group, were performed to obtain the relations between the solidification conditions and the cooling rates in operational conditions (chemical composition, ingot section, casting speed, and casting temperature). In the obtained equations for λ2 in function of the position, it was observed in the steels with similar chemical composition that the 150 mm section samples presented lower values when compared with 180 mm and 240 mm sections samples. In the comparison among the steels with similar equivalent carbon contents, the values of λ2 presented an increment in function of the increasing of the sections. In the comparison of steels with same section and different chemical compositions, the equations for λ2 in function of the simulated cooling rates presented an increasing of the λ2 with the increasing of the equivalent carbon contents.

A novel sintering technique for fabrication of functionally gradient WC–Co cemented carbides

Functionally graded or functionally gradient WC–Co cemented carbides with Co and/or hardness gradients can potentially have great practical importance. In this article is described a novel sintering technique for fabrication of functionally gradient WC–Co cemented carbides. This technique includes (1) employing green carbide bodies with low (or high) carbon contents within the two-phase region of the W–Co–C phase diagram; (2) their pre-sintering in the solid state to obtain a certain green density and consequently gas permeability; (3) selective carburisation (or decarburisation) of their surface layer in a carburising (or decarburising) gas atmosphere; and (4) final liquid-phase sintering at tailored sintering conditions to obtain a Co drift (also known as ‘Co migration’) either from the surface towards the core or from the core towards the surface. The kinetics of Co drift between couples of model alloys with very similar WC mean grain sizes but different carbon contents were examined. The microstructure, hardness, Co contents, residual stresses and wear-resistance of the gradient cemented carbides with low-Co surface layers obtained by the selective surface carburisation of carbide green bodies with the original low carbon content were examined. Their surface layers were found to contain significantly less Co than the core resulting in a higher hardness of the surface layer. The surface layer is also characterised by high residual compressive stresses in both the carbide phase and binder phase, which results in an improved combination of hardness and fracture toughness. The microstructure, hardness and Co contents of gradient cemented carbide comprising high-Co surface layers obtained by selective surface decarburisation of carbide bodies with the original high carbon content were also examined. The surface layer of the gradient cemented carbide contains noticeably more Co than the core which is beneficial when using this functionally gradient carbide as a substrate for polycrystalline diamond coatings.

Gradient WC-Co hardmetals: Theory and practice

The production of functionally graded or functionally gradient WC-Co hardmetals having a near-surface layer with a low Co content and high hardness, and not comprising the η-phase has been the objective of intensive research in the last several years. The present work is devoted to the fabrication and examination of such gradient hardmetals and consists of two parts. In the first part, the kinetics of Co drift between couples of model alloys with very similar WC mean grain sizes but different carbon contents was examined. These model alloys include (1) WC+Co+free carbon, (2) WC+Co+very little η-phase and (3) WC+Co with very low carbon content but free of η-phase. The Co drift in the model alloys consisting of the alloy 1 on the one hand and the alloys 2 and 3 on the other hand was found to be similar. Therefore, a significant Co gradient was expected can be obtained in functionally gradient hardmetals not comprising the η-phase. In the second part, the microstructure, hardness, Co contents, residual stresses and wear-resistance of functionally gradient hardmetals obtained by the selective carburisation of the near-surface layer before liquid phase sintering were examined. A significant Co gradient of up to 7wt.% and a noticeable hardness gradient of up 250 Vickers units was found to be achieved in such hardmetals. Their near-surface layer is characterised by high residual compression stresses in both the carbide phase and binder phase, which allows an exceptionally high combination of hardness and fracture toughness to be obtained. Wear-resistance of such gradient hardmetals in percussive drilling of quartzite and cutting of abrasive concrete was found to be higher compared to corresponding conventional hardmetals with uniform Co distribution by roughly 2 to 4 times.

Soil lipids from accelerated solvent extraction: Influence of temperature and solvent on extract composition

Soil lipids are frequently extracted using accelerated solvent extraction as it is reliable and effective. However, comparisons of extraction efficiency with different soil types or different solvents or temperatures are scarce. We extracted lipids from two soil types (vertisol and cambisol) with similar organic matter content and using four solvents or solvent mixtures of different polarity, at different temperatures, to evaluate the influence of these parameters. We compared the quantity of lipid extracted and characterised the extracts from the cambisol by way of gas chromatography–mass spectrometry (GC–MS) to determine the type of components extracted. Each component was quantified and principal component analysis was used to highlight the influence of solvent and temperature.Despite similar organic carbon content, the extracts varied significantly and were dependent on solvent and temperature. The lipid yield was affected differently by the solvent or temperature depending on the soil. GC–MS revealed differences in the composition of the extracts. The principal component analysis showed unambiguously that extraction with a high concentration of MeOH led to extraction of carbohydrates. In addition, temperature might have altered the n-alcohols and sterols, whereas the n-carboxylic acids were more efficiently extracted at higher temperature.

Characterization of the size-fractionated biomacromolecules: Tracking their role and fate in a membrane bioreactor

This article presents a study aimed at the fractionation and characterization of what is thought to be one of the most complex organic mixtures produced by activated sludge: biomacromolecules (BMM). Photometric quantification combined with excitation–emission matrix (EEM) fluorescence spectroscopy and nuclear magnetic resonance (NMR) measurements were used to characterize BMM in a membrane bioreactor (MBR) from a chemical perspective. Overall, the BMM in sludge supernatant were mainly present in three fractions: colloidal BMM (BMMc, >0.45 μm), biopolymeric BMM (BMMb, 0.45 μm–100 kDa) and low molecular weight (MW) fraction (<5 kDa). The analysis of fluorescence regional integration (FRI) showed that the organics in membrane permeate and those in the low-MW fraction of sludge supernatant were of similar chemical composition. The characterization by NMR suggested that the BMMc fraction had similar carbon content of proteins and polysaccharides. In contrast, the BMMb and the low-MW BMM were proved to be carbonaceous and aromatics, respectively. Moreover, because of the high MW and gelling property, polysaccharides were found to have a high potential to accumulate on the membranes. In addition, the lipids present in the BMMb of the sludge supernatant were demonstrated to be another important foulant due to their large size. Our results also indicated that aromatic proteins had a higher fouling propensity than tryptophan proteins though they were of similar size nature. This work could be useful for better understanding of the chemical nature of BMMs in MBRs.

Impacts of added dissolved organic carbon on boreal freshwater pelagic metabolism and food webs in mesocosm experiments

We studied the response of pelagic community metabolism, bacterial community structure and the origin of crustacean zooplankton carbon following additions of two different sources of dissolved organic carbon (DOC), natural humic water and cane sugar, in two mesocosm experiments lasting 15-18 days. Experimental water with the natural plankton community originated from two boreal lakes in southern Finland having similar total organic carbon (ca. 11 mg L -1 ) and total phosphorus (ca. 13 μg L -1 ) content, but differing in total nitrogen content (ca. 1450 and 440 mg L -1 ). The experiments demonstrated limitation of bacterial activity mainly by biodegradable DOC in the high nitrogen lake water, and by nitrogen in the low nitrogen lake water, which was also reflected in total pelagic energy metabolism and zooplankton productivity. DOC additions caused changes in the bacterial community structure, shown by length heterogeneity analysis of the PCR amplified 16S rRNA gene (LH-PCR). Cane sugar, differing in stable carbon isotope value (δ 13 C ca.-11‰) from that of humic matter of boreal terrestrial vegetation (δ 13 C ca.-28‰), proved to be a good tracer of DOC via bacteria to metazooplankton, especially in the nitrogen-limited conditions. Utilization of detrital particulate terrestrial organic matter by zooplankton was also evident, but it appeared to be a poor quality food. Our results show that an increased loading of allochthonous DOC to boreal lakes as predicted under future climate scenarios will not necessarily stimulate bacterial production and hence carbon transfer up the food web. Whether this happens will be strongly dependent on the stoichiometry (C: N:P ratios) of the available resources.

Phosphorus, nitrogen, and carbon contents of macrophytes in lakes lateral to a tropical river (Paranapanema River, São Paulo, Brazil)

AIM: The aim of this paper was to determine the phosphorus, nitrogen, and carbon contents of aquatic macrophyte species during two periods of the year in the land-water transition zone of three lakes lateral to the Paranapanema River (São Paulo); METHODS: Plants, water, and sediment were collected during two distinct periods (August 1998 and February 1999) in three transects perpendicular to littoral zones of the sampled sites. For the determination of the phosphorus, nitrogen and carbon contents of aquatic macrophyte species, aerial and submerged plant structures (leaves, roots, and stems) were used; RESULTS: In Camargo Lake, which has a poor connection with the river during the dry period (August 1998), the highest nitrogen content was obtained for Salvinia auriculata Aublet, while the highest phosphorus contest was observed for Eichhornia azurea (Swartz) Kunth. During the rainy season (February 1999), Echinochloa polystachya (H.B.K.) Hitch was the species with the highest phosphorus, nitrogen, and carbon contents. In Coqueiral Lake (a lake with great connectivity to the river), the highest phosphorus and nitrogen concentrations during the dry period were observed for Cyperus esculentus L. Similar carbon contents were found for both C. esculentus and Eichhornia azurea. During the rainy season, the species with the highest phosphorus and nitrogen concentrations were E. polystachya, Ludwigia octovalvis (Jacq.) P.H.Raven, and Polygonum spectabile Mart. Considering the plants recorded during the dry period in Cavalos Lake, which is isolated from the river, Myriophyllum aquaticum (Vellozo) Verdcourt was the species with the highest phosphorus and nitrogen concentrations. During the rainy period, C. esculentus and E. azurea had the highest nitrogen concentration. All the aquatic macrophyte species presented similar carbon contents. The highest phosphorus concentration was that of C. esculentus; CONCLUSIONS: The bottom of Camargo and Coqueiral Lakes (both with permanent connection with the river) and some sites of Cavalos (an isolated lake) can be considered similar. They were characterized by sediment with more phosphorus, organic matter, silt, and clay than other sites, which can affect the macro-nutrient content of macrophytes. In the isolated lake, the degradation of submerged plants at the land-water interface contributed to the nutrient pool of aquatic macrophytes after rainfall.

Chemical functionalities of high and low sulfur Australian coals: A case study using micro attenuated total reflectance–Fourier transform infrared (ATR–FTIR) spectrometry

The macerals in bituminous coals with varying organic sulfur content from the Early Permian Greta Coal Measures at three locations (Southland Colliery, Drayton Colliery and the Cranky Corner Basin), in and around the Sydney Basin (Australia), have been studied using light-element electron microprobe (EMP) analysis and micro-ATR–FTIR. Electron microprobe analysis of individual macerals reveals that the vitrinite in both the Cranky Corner Basin and Drayton Colliery (Puxtrees seam) samples have similar carbon contents (ca. 78% C in telocollinite), suggesting that they are of equivalent rank. However, the Cranky Corner coals have anomalously low vitrinite reflectance (down to 0.45%) vs. the Drayton materials (ca. 0.7%). They also have very high organic S content (3–6.5%) and lower O content (ca. 10%) than the equivalent macerals in the Drayton sample (0.7% S and 15.6% O). A study was carried out to investigate the impacts of the high organic S on the functional groups of the macerals in these two otherwise iso-rank, stratigraphically-equivalent seams. An iso-rank low-S coal from the overlying Wittingham Coal Measures near Muswellbrook and coals of slightly higher rank from the Greta Coal Measures at Southland Colliery near Cessnock were also evaluated using the same techniques to extend the data set. Although the telocollinite in the Drayton and Cranky Corner coals have very similar carbon content (ca.78% C), the ATR–FTIR spectra of the vitrinite and inertinite macerals in these respectively low S and high S coals show some distinct differences in IR absorbance from various aliphatic and aromatic functional groups. The differences in absorbance of the aliphatic stretching bands (2800–3000 cm −1) and the aromatic carbon (C C) peak at 1606 cm −1 are very obvious. Compared to that of the Drayton sample (0.7% S and 15% O), the telocollinite of the Cranky Corner coal (6% S and 10% O) clearly shows: (i) less absorbance from OH groups, represented by a broad region around 3553 cm −1, (ii) much stronger aliphatic C–H absorbance (stretching modes around 3000–2800 cm −1 and bending modes around 1442 cm −1) and (iii) less absorbance from aromatic carbon functional groups (peaking at 1606 cm −1). Evaluation of the iso-rank Drayton and Cranky Corner coals shows that: (i) the aliphatic C–H absorbances decrease with increasing oxygen content but increase with increasing organic S content and (ii) the aromatic H to aliphatic H ratio (Har/Hali) for the telocollinite increases with (organic) O%, but decreases progressively with increasing organic S. The high organic S content in the maceral appears to be accompanied by a greater proportion of aliphatic functional groups, possibly as a result of some of the O within maceral ring structures in the high S coal samples being replaced.

INFOCARB: A regional scale forest carbon inventory (Provincia Autonoma di Trento, Southern Italian Alps)

The aim of this inventory (acronym: INFOCARB) was to measure the organic carbon stored in the forest ecosystems of the Trento region (Provincia Autonoma di Trento, Northern Italy) in both above- and belowground pools, according to the Kyoto protocol and IPCC requirements. A total of 150 forest sampling points were selected on the entire regional area (6206 km 2) with a statistical sampling approach, based on the timber volume as a proxy variable for a stratified sampling. Each sampling point was located with a GPS receiver and a 600 m 2 circular plot was delimited around each point. Inside the plots, the biomass of trees, shrubs and herbaceous vegetation was measured, while litter was collected in systematically placed subplots. Topsoil (down to 30 cm depth) was sampled with the excavation method on three systematically located pits, to determine the organic carbon content, the bulk density and the volume occupied by stones and roots. The inventory estimated the regional total carbon content of the forests as 71.9 ± 5.2 Tg C, with an average carbon density of 207.01 ± 14.5 Mg C ha −1. The aboveground biomass and the soil had a similar carbon content, 43.2% and 44.6% of the total ecosystem carbon, respectively, whereas the root systems and the litter accounted for 9.6% and 2.6%, respectively. Due to the high inter-site variability, only weak statistical relationships were found between the soil carbon content and main ecosystem and climatic variables. However, when dividing the plots into different species-dominated forests, the beech sites differed significantly from the conifer sites in the carbon stock and the C/N ratio in the soil organic layers.

Phosphorus, nitrogen, and carbon contents of macrophytes in lakes lateral to a tropical river (Paranapanema River, São Paulo, Brazil)

AIM: The aim of this paper was to determine the phosphorus, nitrogen, and carbon contents of aquatic macrophyte species during two periods of the year in the land-water transition zone of three lakes lateral to the Paranapanema River (Sao Paulo); METHODS: Plants, water, and sediment were collected during two distinct periods (August 1998 and February 1999) in three transects perpendicular to littoral zones of the sampled sites. For the determination of the phosphorus, nitrogen and carbon contents of aquatic macrophyte species, aerial and submerged plant structures (leaves, roots, and stems) were used; RESULTS: In Camargo Lake, which has a poor connection with the river during the dry period (August 1998), the highest nitrogen content was obtained for Salvinia auriculata Aublet, while the highest phosphorus contest was observed for Eichhornia azurea (Swartz) Kunth. During the rainy season (February 1999), Echinochloa polystachya (H.B.K.) Hitch was the species with the highest phosphorus, nitrogen, and carbon contents. In Coqueiral Lake (a lake with great connectivity to the river), the highest phosphorus and nitrogen concentrations during the dry period were observed for Cyperus esculentus L. Similar carbon contents were found for both C. esculentus and Eichhornia azurea. During the rainy season, the species with the highest phosphorus and nitrogen concentrations were E. polystachya, Ludwigia octovalvis (Jacq.) P.H.Raven, and Polygonum spectabile Mart. Considering the plants recorded during the dry period in Cavalos Lake, which is isolated from the river, Myriophyllum aquaticum (Vellozo) Verdcourt was the species with the highest phosphorus and nitrogen concentrations. During the rainy period, C. esculentus and E. azurea had the highest nitrogen concentration. All the aquatic macrophyte species presented similar carbon contents. The highest phosphorus concentration was that of C. esculentus; CONCLUSIONS: The bottom of Camargo and Coqueiral Lakes (both with permanent connection with the river) and some sites of Cavalos (an isolated lake) can be considered similar. They were characterized by sediment with more phosphorus, organic matter, silt, and clay than other sites, which can affect the macro-nutrient content of macrophytes. In the isolated lake, the degradation of submerged plants at the land-water interface contributed to the nutrient pool of aquatic macrophytes after rainfall.

High-temperature Interactions of Alumina–Carbon Refractories with Molten Iron

The interfacial behaviour of alumina/carbon refractories with liquid iron was investigated at 1550°C, with emphasis on the chemical interactions occurring both in the interfacial region as well as in the bulk of the refractory. The sessile drop technique was used to determine the interfacial wetting behaviour and the phase transformations during the chemical reactions were determined using SEM and EDS. Alumina–carbon refractories were prepared using two types of carbonaceous materials–synthetic graphite and natural graphite. From the experimental results, it was clearly observed that molten iron had penetrated to varying extents into all refractory substrates. The highest penetration was observed for alumina–carbon refractory substrates containing 10% synthetic graphite, while all alumina–natural graphite substrates showed much lower levels of metal penetration. Contact angles for synthetic graphite and natural graphite containing refractories showed an initial drop in the first 5 min of the experiment before increasing and stabilising at different values depending on the composition of the refractories. The initial drop in the contact angles was in direct correspondence with increasing carbon pickup values for these samples. Natural graphite samples generally showed lower carbon pickup as compared to synthetic graphite samples of similar carbon content. The differences in metal penetration and interfacial wetting behaviour were found to depend on the carbon pickup and the ash content of the refractory substrates, with the ash helping in the formation of an interfacial layer which limited reactions with the metal, and in filling the pores within the refractory.

Artemia replacement in co-feeding regimes for mysis and postlarval stages of Litopenaeus vannamei: Nutritional contribution of inert diets to tissue growth as indicated by natural carbon stable isotopes

The nutritional contribution from co-fed Artemia nauplii and inert diets to growth in mysis and early postlarval shrimp Litopenaeus vannamei was assessed by analyzing the carbon stable isotope ratios ( δ 13C) in diets and shrimp tissue. Artemia nauplii and inert diets showed significantly different δ 13C values but similar carbon contents and were supplied as single diets and also in three co-feeding regimes in which 25, 50 and 75% of the Artemia was replaced by inert diet on a dry weight basis, so that all feeding regimes provided similar amounts of dietary carbon. Shrimp δ 13C values were significantly influenced by the different feeding regimes and reached isotopic equilibrium with their respective diets as soon as 5 days. Survival was significantly higher in co-fed animals than in those fed either Artemia or inert diet alone. There was no significant difference in growth between shrimp fed on Artemia only and those co-fed Artemia with inert diet, although the variability was high. Growth and survival were very low in shrimp fed only inert diet. Results from an isotope mixing model suggest that observed nutrient contributions from Artemia nauplii were significantly higher than expected contributions indicated by proportions established in the co-feeding regimes. From mysis 3 to postlarvae 5, nutrient contributions to growth in the dietary regime providing equal carbon amounts of each diet type ranged from 73 to 87% for Artemia and from 13 to 27% for inert diet. Shrimp fed the 25% Artemia replacement regime exhibited a significantly higher retention of dietary carbon from the inert diet than those fed inert diet alone. This may have resulted from greater ingestion and/or assimilation of the inert diet in the presence of Artemia, combined with the higher growth rate supported by co-feeding. The results demonstrate the effectiveness of up to 50% replacement of Artemia with inert diet for L. vannamei mysis and early postlarval stages, indicating also that the inert diet may provide specific nutrients that promote higher survival, while digestibility may limit its contribution to tissue growth. The isotopic influence of maternal nutrients and dietary sources on earlier larval stages was also described.

High temperature properties of several chromium-containing Co-based alloys reinforced by different types of MC carbides (M = Ta, Nb, Hf and/or Zr)

Five cast cobalt alloys based on Co–8Ni–30Cr–0.4/0.45C and containing Ta, Nb, Hf and/or Zr were studied by metallography in the as-cast condition and after treatments at 1300 °C. The obtained MC carbides were all interdendritic with a eutectic script-like morphology. For similar carbon contents, the HfC carbides are the most developed in the as-cast microstructure and the most stable at 1300 °C. As-cast, the TaC carbides are less developed than the former and they tend to become more fractioned and less present in microstructure at 1300 °C. The NbC carbides, which have initially the same morphology and the same fraction as TaC, rapidly dissolve at 1300 °C. The cobalt alloys containing HfC or TaC are chromia – forming at 1300 °C. The NbC-containing alloy catastrophically oxides after only few hours at 1300 °C. The average hardness is the highest for the HfC-containing alloy and the lowest for the NbC-containing alloy.

Structural characterization of vitrinite-rich and inertinite-rich Permian-aged South African bituminous coals

Two South African coals of the same rank and age, but different in maceral composition were subjected to extensive structural analyses. Inertinite-rich Highveld coal (dominated by semifusinite) and vitrinite-rich Waterberg coal were studied to determine structural differences and similarities. The two coals had similar carbon content (∼ 84%, dmmf) and vitrinite reflectance (mean-maximum 0.71% for vitrinite-rich vs. 0.75% for inertinite-rich), but differed in hydrogen content (6.23% for vitrinite-rich and 4.53% for inertinite-rich). The inertinite-rich coal was more aromatic (86% for inertinite-rich and 76% for vitrinite-rich) and more polycondensed (indicated by a higher bridgehead carbon content). The inertinite-rich coal was structurally more ordered, with a higher degree of crystalline stacking. Both coals had similar average aromatic cluster sizes (16 carbons for vitrinite-rich and 18 carbons for inertinite-rich) and number of cluster attachments (6 attachments for vitrinite-rich and 5 attachments for inertinite-rich). Mass spectrometry showed that both coals consist of similar molecular weight distributions; ranging to approximately 1700 m/z with a maximum abundance of ∼ 450 m/z for the vitrinite-rich coal and ∼ 550 m/z for the inertinite-rich coal. Compared to the Argonne Premium coals the South African vitrinite-rich Waterberg coal was comparable to the coals in the high-volatile bituminous range and inertinite-rich Highveld was closer to the medium- to low-volatile bituminous range. Both coals were surprisingly similar in bulk characterization, although inertinite-rich Highveld coal was structurally more ordered, hydrogen deficient, and more aromatic.

Bioaccumulation, sublethal toxicity, and biotransformation of sediment-associated pentachlorophenol in Lumbriculus variegatus (Oligochaeta)

The xenobiotics accumulated in sediments represent a hazard to organisms. In order to study the toxic effects of xenobiotics in organisms, body residue has been proposed as a more relevant dose-metric than the environmental concentration of the chemical. In this study, the benthic oligochaetes Lumbriculus variegatus were exposed to sediment-spiked pentachlorophenol (PCP) in a chronic study at different exposure concentrations. The aim was to examine sublethal toxic effects in sediment-dwelling and sediment-ingesting organisms, and to link the effects with chemical body residues. Growth, reproduction, and egestion rate were used as sublethal endpoints. Bioaccumulation, sublethal toxic effects, and biotransformation of PCP were investigated by exposing organisms to both artificial and natural sediments with similar organic carbon content. Sediment characteristics were assumed to have an effect on toxicity since PCP retarded both growth and reproduction in L. variegatus in the artificial sediment. In natural sediment, growth, and reproduction was also reduced in control treatments, probably indicating poor nutritional quality. Most of the extracted chemicals in L. variegatus tissues were water-soluble metabolites, indicating that L. variegatus was capable of biotransforming PCP. The extractable parent PCP body residues (CBR 50) for L. variegatus growth and reproduction were in agreement with the values estimated for respiratory uncouplers in the literature.

Physical properties of shungite

Abstract This paper presents the results of physical parameters such as bulk porosity, true density, optical reflectance, dynamic elastic moduli, X-ray diffractograms and EPR spectra, determined for shungite. All shungite samples studied are considerably denser materials than anthracite — high rank coal with similar carbon content. Bright shungites were porous with the very dense matrix, while the dull shungite is compact, almost non-porous material. Elastic moduli of the dull shungite are generally higher than those of bright shungites and anthracite. All shungites studied (including anthracite) exhibit the directional dependence of elasticity. The maximum reflectance values of bright shungites are higher than those for dull shungite and anthracite. That corresponds with the denser matrix of these samples and suggests the greatest ordering of graphene layers in the case of bright shungites and also suggests some similarity to meta-anthracite from Paleozoic basins. Reflectance anisotropy of shungites studied are generally lower than that of anthracite. Ordering of graphene layers in bright shungite, as a high rank coal variety, is obvious, but lower anisotropy than that of anthracite is a surprise. X-ray studies confirm a high density of bright shungite. Interplanar distances dhkl of the shungite (d002 = 3.48 A) are closer to those of anthracite (d002 = 3.52 A) than to those of graphite (d002 = 3.35 A). All results described here show the differences in molecular structure and degree of graphitisation of carbonaceous matter in bright, semi-bright and dull varieties of shungite. Our data could play a key role in production of materials composed of carbon nanoparticles.

Variations in elemental composition of macerals with vitrinite reflectance and organic sulphur in the Greta Coal Measures, New South Wales, Australia

Abstract The elemental composition of the individual macerals in the Early Permian Greta Coal Measures of the northern Sydney Basin and adjoining Cranky Corner Basin, New South Wales, including some seams with high to very high organic sulphur contents, have been analysed in polished sections using light-element electron microprobe techniques, and the results evaluated in the light of vitrinite reflectance and other characteristics of the coals concerned. As with other Australian coals, the vitrinite macerals in each sample have the lowest proportions of carbon and highest proportions of oxygen, and the inertodetrinite and fusinite macerals the highest C and lowest O contents. Semifusinite and the liptinite macerals have intermediate C and O percentages. Organic sulphur and organic nitrogen are also highest in the vitrinite macerals of the individual samples, and lowest in the fusinite and inertodetrinite components. The vitrinite macerals in the Puxtrees seam of the Greta Coal Measures on the Muswellbrook Anticline, in the upper Hunter Valley, have similar elemental compositions (78% C) and similar reflectance values (Rv max around 0.7%) to vitrinites in the Late Permian bituminous coals in other parts of the Sydney-Bowen Basin. The vitrinites in the seams of the Cranky Corner Basin also have similar carbon contents to the Puxtrees seam material, suggesting a similar rank level, but have much lower vitrinite reflectance values (Rv max = 0.4–0.5%), probably due to marine influence associated with the depositional system. The vitrinites in the Greta seam on the Lochinvar Anticline, in the Lower Hunter region, have higher carbon contents (83%) than the Puxtrees material, suggesting a higher rank level, but similar to lower vitrinite reflectance values (Rv max = 0.6–0.7%). Vitrinite carbon is also constant through the seam profile, despite upwardly decreasing reflectance values in the seam due to progressive increases in marine influence. The vitrinites in the upper Greta seam and the Cranky Corner Basin coals have high to very high organic sulphur contents, again probably due to marine influence on the depositional process. The vitrinites in the Cranky Corner Basin coals, which have particularly high organic sulphur contents, also have somewhat lower oxygen contents in relation to their carbon percentages than those of other Australian seams, suggesting that the additional organic sulphur has replaced oxygen in the macerals' molecular structure. The macerals, especially the vitrinites, in the coals with high organic sulphur and anomalously low vitrinite reflectance also have up to 0.5% Al and 1% Ca intimately associated with the organic matter. Similar organically associated inorganic elements are commonly found in lower-rank (e.g. sub-bituminous) coals, but are usually lost from the organic matter at higher rank levels. The coals of the Greta Coal Measures therefore have vitrinite carbon contents consistent with a high volatile bituminous rank, but those seams or parts of seams with high organic sulphur due to substantial marine influence appear to have preserved the vitrinite reflectance values and organically associated inorganic elements more typical of lower-rank, sub-bituminous materials.

Microbial diversity in three floodplain soils at the Elbe River (Germany)

Microbial communities in floodplain soils are exposed to periodical flooding. A long-term submerged Eutric Gleysol (GLe), an intermediate flooded Eutric Fluvisol (FLe), and a short-time flooded Mollic Fluvisol (FLm) at the Elbe River (Germany) with similar organic carbon contents (C org) between 8.1% and 8.9% were selected to test the quality of phospholipid fatty acids (PLFA), soil microbial carbon (C mic), basal respiration (BR), metabolic quotient (qCO 2), and C mic/C org ratio to characterize and discriminate these soils with microbial parameters. The three floodplain soils can be differentiated by C mic and by total PLFA-biomass. Due to the different flooding durations and the time since the soils were last flooded C mic and PLFA-biomass increase in the order GLe<FLe<FLm. Both parameters correlate significantly ( r = 0.999 ; p < 0.05 ) . The C mic/C org ratios are low in comparison to terrestrial soils and revealed the same ranking over the three soils like C mic. Contrary, qCO 2 and BR are highest in GLe and lowest in FLm according to inundation regime. The diminished C mic, high BR, and high qCO 2 values in GLe seem to be an unspecific response of aerobic soil microorganisms on the long flooding period and the resulting short time for developing after last flooding as well as the low pH value. Different plant communities and their residues may influence the microbial diversity additionally. The PLFA profiles were dominated by the group of saturated fatty acids that together constituted almost 62–72% of the total fatty acids identified in the soils. In GLe all groups of PLFA, inclusive monounsaturated fatty acids, are lowest and in FLm highest, while in FLe the PLFA fractions show an intermediary amount of the three soils. The FLm had most of the time aerobic conditions and revealed therefore the highest C mic, PLFA-biomass, especially monounsaturated fatty acids, C mic/C org ratio as well as relatively low BR and qCO 2 value. These indicate that microorganisms in FLm are more efficiently in using carbon sources than those in GLe and FLe. All 26 identified PLFA were found in FLe and FLm, while the polyunsaturated fungi biomarker 18:2 ω6,9c could not be detected in GLe. In this long-time submerged soil the environmental conditions which microorganisms are exposed might be disadvantageous for fungi.

Changes in surface water quality after inundation of acid sulfate soils of different vegetation cover

Surface soils from an acid sulfate soil (ASS) backswamp were inundated in a temperature controlled environment and surface-water chemistry changes monitored. The soils had contrasting in situ vegetative cover [i.e. 2 grass species, Cynodon dactylon and Pennisetum clandestinum (Poaceae), and litter from Melaleuca quinquenervia (Myrtaceae)]. The different vegetation types had similar biomass and carbon content; however, there were large differences in the quality and lability of that carbon, which strongly influenced decay/redox processes and the chemical composition of surface waters. The grass species had more labile carbon. Their surface waters displayed rapid sustained O2 depletion and sustained low Eh (~0 mV), high dissolved organic carbon (DOC), and moderate pH (5–6). Their soil acidity was partially neutralised, sulfides were re-formed, and reductive dissolution of Fe(III) led to the generation of stored acidity in the water column as Fe2+(aq). In contrast, M. quinquenervia litter was high in decay-resistant compounds. Its surface waters had lower DOC and low pH (&lt;4) and only underwent a short period of low O2/Eh. Soluble Al caused M. quinquenervia surface waters to have higher titratable acidity and soil pH remained consistently low (~3.8–4.0). Concentrations of Cl– and Al in surface waters were strongly correlated to initial soil contents, whereas the behaviour of Fe and SO42– varied according to pH and redox status. This study demonstrates that changes in vegetation communities in ASS backswamps that substantially alter either (a) the pool of labile vegetative organic carbon or (b) the concentration of acidic solutes in surface soil can have profound implications for the chemical characteristics of backswamp surface waters.

High temperature oxidation mechanism of a 3%Ni cast stainless steel

In this work, the high temperature oxidation mechanism of a high chromium (28 wt-%) cast stainless steel containing 3%Ni, and with an austenitic–ferritic microstructure, has been studied and compared to that of a ferritic stainless steel with similar chromium and carbon contents but without any nickel additions. Two different oxidation temperatures (800 and 970°C) were selected for both the as cast and annealed (600°C for 2200 h) conditions. The oxidation mechanism of the Ni-containing duplex alloy has been found to involve the formation of four successive layers:(i) the external scale exhibiting the crystalline structure of Cr2O3(ii) a single phase metal layer in contact with the oxide and consisting of austenite(iii) a decarburised zone exhibiting a two phase structure of ferrite and austenite(iv) the initial alloy microstructure consisting of ferrite, austenite and alloy carbides.The oxidation resistance of the austenitic–ferritic alloy is in all cases 50–100% higher than that of the ferritic alloy, while that of the annealed samples (all other experimental conditions remaining constant) is ten times higher than that of the as cast samples.