Carbon-rich Particles Research Articles

Efficient separation of coal gasification fine slag from Texaco gasifier and microstructures and elemental characteristics of separated components

ABSTRACT Coal gasification fine slag (CGFS) is one of the by-products of coal gasification process, which is mainly composed of inorganic minerals and residual carbon. The key to realize the high-value utilization of CGFS is separating the residual carbon and mineral in CGS effectively. Owing to irregular distribution of carbon in different size of CGFS, which could not be enriched by simple grinding and screening for component enrichment. In this paper, the enrichment of CGFS was carried out by the float-sink method, which is low-cost and does not result in the loss of raw materials. The carbon-rich particles (CRP, ash: 27.89%) and mineral-rich particles (MRP, ash: 78.01%) were obtained, where CRP contains a large amount of amorphous carbon with rich porous structure, while MRP is a heterogeneous material containing not only inorganic minerals but also organic carbon with low porosity. The mineral particles exist as aluminosilicates with a high degree of polymerization. The results of this paper will provide theoretical and technical support for the high-value utilization of CGFS.

Mangrove ecosystems’ role in climate change mitigation

Mangrove forests are crucial to ecosystems for their benefits, and role in climate change mitigation. Across marine and terrestrial boundaries, they shield coastal areas from tidal waves and storms, with dense roots that dissipate wave energy effectively. These roots also trap carbon-rich particles from the water, storing them in sediments and fostering sediment accretion and carbon burial. Mangrove ecosystems have declined over the past five decades, largely due to aquaculture. This decline reduces coastal resilience, exacerbating risks from storms, sea-level rise, and erosion, while releasing stored carbon as CO2 emissions. Mangrove degradation is crucial for climate mitigation. Mitigation strategies should prioritize conserving ecosystems with high carbon sequestration rates, reducing anthropogenic CO2 emissions, and rehabilitating mangrove habitats converted for aquaculture. We must expand our knowledge and understanding of the significance of mangroves in delivering coastal protection, how mangrove ecosystems serve as carbon sinks, how future changes could impact them, and how anthropogenic activities and climate change can impact their carbon storage.

Personal measurements and sampling of particulate matter in a subway – Identification of hot-spots, spatio-temporal variability and sources of pollutants

A mobile measurement system for complex characterization of particulate matter (PM) was developed together with the proposed methodology and applied in the subway system of Munich, Germany. The main objectives were to observe the spatio-temporal variability of PM, personal exposure, identify hot-spots and pollution sources. Particle mass (PMx) and number (PNC) concentrations, and equivalent black carbon (eBC) were measured at 0.1–1 Hz. On the U5 subway line, PM10, PM2.5 and PM1 concentrations at platforms ranged from 59 to 220, 27–80, and 9–21 μg m−3, respectively. During rides towards downtown, average PM10, PM2.5 and PM1 levels gradually increased from 8 to 220, 2 to 71 and 2–20 μg m−3, respectively, with a similar dynamic of decrease on the return journey. Spatial variability of PM was generally more important than temporal, and significant differences were observed between platforms. During the rides, air exchange between train and tunnel was high in both air-conditioned and old passively ventilated trains. Peak PM concentrations on platforms were associated with arriving/departing trains. Subway PNC were not significantly elevated, but a few cases of intake of traffic-related particles from outside were observed, otherwise air exchange was considered low. Generally, most of the aerosol mass was composed of iron corrosion products from rails and wheels (Fe up to 66 μg m−3 in PM2.5). The effective density of PM2.5 was 2.1 g cm−3. Particles were classified as 75.4% iron oxides, 5.35% metallic Fe, 1.23% aluminosilicates and 17% carbon and oxygen rich particles. The iron oxide particles consisted predominantly of Fe (63.4 ± 8.7 wt%) and O (36.2 ± 8.2 wt%). To effectively monitor subway PM and reduce overall PM exposure, we propose to identify hot-spots using our methodology and focus on improving their ventilation, as well as installing filters in air-conditioned wagons.

Investigation of Presence of Carbon-Rich Particles on Cobalt-Based Cardiovascular Implants and Their Influence on the Corrosion Resistance and Biocompatibility

Investigation of Presence of Carbon-Rich Particles on Cobalt-Based Cardiovascular Implants and Their Influence on the Corrosion Resistance and Biocompatibility

Development of an Additional Selective Layer to Mitigate Crossover in Vanadium Redox Flow Batteries: Influence of Composition on Efficiency and Capacity Decay

Vanadium redox flow battery (VRFB) is a promising technology for energy storage because of its independent energy to power ratio and long cycle life. However, VRFB commercialization is still hindered by some technological issues, among which the capacity loss induced by the undesired transport of ions across the ion-exchange membrane. Depending on the nominal operating condition, the choice of a suitable membrane for VRFB application results from the trade-off between low vanadium ions permeability and high proton conductivity. Usually, in order to reduce undesired ion fluxes between the two half-cell electrolytes, the membrane thickness is relatively high, implying increased ohmic losses (i.e., reduced energy efficiency) and system capital cost. In fact, state of the art membranes can represent up to 50% of stack capital cost [1]. Nafion® is widely used due to its high conductivity, but it is not ideally selective towards vanadium ions, leading to the adoption of thicker membrane to limit capacity loss. Alternative cation exchange membranes like SPEEK or SPI are promising because of their reduced permeability, but the low conductivity limits system power density. Instead, anion exchange membranes are still limited by the poor chemical stability and low conductivity [2].In a recent work [3], the authors demonstrated the proof of concept of an additional selective layer to mitigate vanadium crossover. The selective layer, termed as barrier, is a porous component in which pores size, tortuous path, thickness and composition are designed to improve ion/proton selectivity. The proof of concept was manufactured with reactive spray deposition technology (RSDT), which is a flame-based synthesis process unique to Dr. Radenka Maric’s research group. For the fabrication of the proof of concept, carbon-rich particles ∼4-10 nm in diameter were formed in the RSDT flame and were deposited directly onto Nafion® 212 (50 μm thick) simultaneously with a mixture of 1100EW Nafion® and Vulcan® XC-72R (∼40 nm diameter) that was sprayed from air-assisted secondary nozzles. The presence of the barrier layer significantly reduced battery self-discharge, as reported in [3].In this work, different compositions and morphologies of the barrier layers were analysed in order to improve ion/proton selectivity. In particular, the influence of ionomer to carbon ratio (I/C), the amount of carbon-rich particles and the introduction of silica were investigated. Moreover, the effect of Nafion® 211 (25 μm thick) as a support for barrier deposition was also evaluated. The barrier layers were characterized in a 25 cm2 cell [4] equipped with reference electrodes at both positive and negative electrode in order to monitor the corresponding electrolyte potential and get an insight into battery state of charge (SoC). In addition to electrochemical testing, the structure of the barrier layer was characterized using TEM and SEM.The most suitable I/C ratio was found to be included between 1 and 2, while the presence of carbon-rich particles significantly contributed to crossover reduction, with a minor impact on proton conductivity. Also the introduction of silica nanoparticles from primary nozzle was effective for vanadium ion selectivity, in particular when the amount of carbon from the secondary nozzle is reduced. In fact, the most promising barrier layer resulted the one composed by only silica and ionomer. This layer was also deposited on Nafion® 211 (Figure 1), exhibiting an excellent trade-off between ion selectivity and proton conductivity. This barrier was proved to be stable over 1,000 cycles, presenting a stable coulombic efficiency of 99.5%, with an average capacity decay of 0.08%/cycle at 100 mA cm-2. Figure 1 – SEM image of only Silica barrier deposited on Nafion® 211.

PM2.5 exceedances and source appointment as inputs for an early warning system

Between June 2018 and April 2019, a sampling campaign was carried out to collect PM2.5, monitoring meteorological parameters and anthropogenic events in the Sartenejas Valley, Venezuela. We develop a logistic model for PM2.5 exceedances (≥ 12.5 µg m−3). Source appointment was done using elemental composition and morphology of PM by scanning electron microscopy coupled with energy dispersive spectroscopy (SEM–EDS). A proposal of an early warning system (EWS) for PM pollution episodes is presented. The logistic model has a holistic success rate of 94%, with forest fires and motor vehicle flows as significant variables. Source appointment analysis by occurrence of events showed that samples with higher concentrations of PM had carbon-rich particles and traces of K associated with biomass burning, as well as aluminosilicates and metallic elements associated with resuspension of soil dust by motor-vehicles. Quantitative source appointment analysis showed that soil dust, garbage burning/marine aerosols and wildfires are three majority sources of PM. An EWS for PM pollution episodes around the Sartenejas Valley is proposed considering the variables and elements mentioned.

Impact of biomass induced black carbon particles in cascading COVID-19

We explore the association of biomass-induced black carbon aerosolized virus with COVID-19 in one of the top-ranked polluted hot spot regions of the world, Delhi, at the time when other confounding factors were almost stable and the pandemic wave was on the declining stage. Delhi was worst affected by COVID-19. However, when it was fast returning back to normal after about 6 months with minimum fatalities, it suddenly encountered a reversal with a 10 fold increase in infection counts, coinciding with the onset of the stubble burning period in neighbouring states. We hereby report that the crop residue burning induced lethal aged Black carbon-rich particles which engulfs Delhi during the post-monsoon months of October–November are strongly associated with COVID-19 and largely responsible for the sudden surge. It is found that the virus efficacy is not necessarily related to any particulates but it is more of source-based toxicity of its component where the virus is piggybacking. We conclude that the aged biomass BC particles tend to aggregate and react with other compounds to grow in size, providing temporary habitat to viruses leading to the rapid increase in COVID-19 cases which declined after the crop burning stopped.

Sweet spheres: succession and CAZyme expression of marine bacterial communities colonizing a mix of alginate and pectin particles.

Polysaccharide particles are important substrates and microhabitats for marine bacteria. However, substrate-specific bacterial dynamics in mixtures of particle types with different polysaccharide composition, as likely occurring in natural habitats, are undescribed. Here, we studied the composition, functional diversity and gene expression of marine bacterial communities colonizing a mix of alginate and pectin particles. Amplicon, metagenome and metatranscriptome sequencing revealed that communities on alginate and pectin particles significantly differed from their free-living counterparts. Unexpectedly, microbial dynamics on alginate and pectin particles were similar, with predominance of amplicon sequence variants (ASVs) from Tenacibaculum, Colwellia, Psychrobium and Psychromonas. Corresponding metagenome-assembled genomes (MAGs) expressed diverse alginate lyases, several colocalized in polysaccharide utilization loci. Only a single, low-abundant MAG showed elevated transcript abundances of pectin-degrading enzymes. One specific Glaciecola ASV dominated the free-living fraction, possibly persisting on particle-derived oligomers through different glycoside hydrolases. Elevated ammonium uptake and metabolism signified nitrogen as an important factor for degrading carbon-rich particles, whereas elevated methylcitrate and glyoxylate cycles suggested nutrient limitation in surrounding waters. The bacterial preference for alginate, whereas pectin primarily served as colonization scaffold, illuminates substrate-driven dynamics within mixed polysaccharide pools. These insights expand our understanding of bacterial niche specialization and the biological carbon pump in macroalgae-rich habitats.

Gasification of chars from tetralin liquefaction of < 1.5 g cm−3 carbon-rich residues derived from waste coal fines in South Africa

The float–sink density separation method was used to produce a < 1.5 g cm−3 coal density fraction. The sample was subjected to tetralin liquefaction experiments and pyrolysed to produce char samples. The < 1.5 g cm−3 coal density fraction and its liquefaction carbon-rich residue chars formed from the pyrolysis experiments were evaluated using the CO2 gasification tests. The chars were characterized using a thermogravimetric analyzer by heating the samples at isothermal temperatures between 880 and 940 °C under a CO2 atmosphere. The results obtained from the gasification experiments revealed that the gasification reactivity values (Ri, Rs, Rtf, Rt/0.5) of the liquefaction carbon-rich residue chars were higher than those of the < 1.5 g cm−3 coal density fraction chars. Some inherent mineral matter in the residues may play a catalytic role during gasification of South African lighter density waste coal density fractions and their liquefaction residue chars. The initial reactivity of the liquefaction residue chars was observed to be approximately double than those of the < 1.5 g cm−3 coal density fraction chars. Significant increases in a number of pores were associated with the liquefaction experiments of these carbon-rich particles, which aid in the acceleration of the gasification reactions. These increases in the number of pores assisted the reduction of the gasification activation energy values. The RPM was shown to fit the experimental data the best and used to determine kinetic parameters. The gasification activation energy of the < 1.5 g cm−3 coal density fraction chars was shown to be 190.5 kJ mol−1 and 236.7 kJ mol−1 for Highveld float (HF) and Waterberg float (WF) chars, respectively. The values of the apparent activation energy for the liquefaction carbon-rich residues from the same two < 1.5 g cm−3 coal density fraction residue samples were 145.3 kJ mol−1 for the Highveld coal sample and 196.0 kJ mol−1 for the Waterberg coal sample. The gasification results obtained in this study indicate that the possibility of utilizing the waste coal floats and their liquefaction carbon-rich residues in the thermochemical processes (pyrolysis and gasification) is high.

The morphology and chemical composition of the urban PM10 near a steel plant in Apulia determined by scanning electron microscopy. Source Apportionment

PM10 samples were collected in a site of Apulia region (South-East Italy) near a steel plant when the winds were blowing from the NW and the SE to exclude and include, respectively, the contribution of the industrial source in order to study the aerosol particles in detail and attribute them to the most appropriate emission sources. Size, morphology and chemical composition of 6500 individual particles, with an equivalent spherical diameter (ESD) between 0.4 ˗ 1 μm, 1 ˗ 2.5 μm and 2.5 ˗ 10 μm, were analysed by scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM - EDX). These particles were classified in the thirteen groups: aluminosilicates, silicates, iron oxides, metal oxides, iron mixtures, aluminosilicates with sulphur, calcium sulphates, silicate-sulphate mixed particles, carbonates, carbonates-silicates, soot, biological particles and carbon rich particles. Source apportionment analyses were carried out separately for the three dimensional ranges considered and for the two wind directions from North-West and South-East and nine main sources were distinguished. The soil and the soot components are higher when the wind blow from the NW than the SE, while the anthropogenic sources are evident with the wind from the SE due to the presence of iron and carbonaceous particles characterized by typical spherical shapes and chemical elements as Ca, Na and K which could to be indicative of industrial activity. The single particle analysis let better identify the emission sources that persist on the territory, attributing to them the particles characterized by peculiar morphology and chemical composition.

Design and Development of an Innovative Barrier Layer to Mitigate Crossover in Vanadium Redox Flow Batteries

Capacity loss induced by the undesired transport of vanadium ions across the ion-exchange membrane (i.e. crossover) is one of the most critical issues associated with vanadium redox flow batteries. This work reports on the manufacturing and testing of an innovative barrier layer to mitigate crossover. The barrier layer conceptual design is described in detail in the patent application WO 2019/197917. The barrier was deposited directly onto Nafion® 212 using the Reactive Spray Deposition Technology, in which carbon-rich particles (∼4–10 nm in diameter) formed in the flame were deposited simultaneously with a mixture of 1100EW Nafion® and Vulcan® XC-72R (∼40 nm diameter) that was sprayed from air-assisted secondary nozzles. During cycles at fixed capacity, the presence of the barrier layer significantly reduced battery self-discharge; the average variation of battery state of charge compared to a reference cell with Nafion® 115 was reduced from 21% to 7%. Moreover, battery energy efficiency was increased by nearly 5%, indicating that the barrier layer does not significantly hinder proton transport. During cycles at 50 mA cm−2 with fixed cut-off voltages, the barrier layer exhibited stable operation, maintaining a coulombic efficiency around 99.4%. Additionally, the use of the barrier layer projects to a 30% reduction of stack-specific cost.

Influence of graphene on the magnetic properties of nickel ferrite nanoparticles

Nickel ferrite nanoparticles were subjected to mechanochemical activation for ball milling times ranging from 0 to 12 h. The milling was performed with and without the addition of equimolar concentrations of graphene nanoparticles. Characterization of resulting nano-powders was undertaken by Mӧssbauer spectroscopy and magnetic measurements. The hyperfine magnetic field was studied as function of milling time for octahedral and tetrahedral sites. An additional quadrupole split doublet represented the occurrence of superparamagnetic particles in the as-obtained and milled specimens. A new phase was obtained in the graphene-milled set of samples, which could be assigned to carbon-rich particles. The degree of inversion and canting angle were derived from the Mӧssbauer measurements and studied as function of ball milling time. The degree of inversion was found to decrease with milling time, especially for the set without graphene and evidenced a transition from inverse to normal spinels. The canting angle decreased with time for the graphene milled nanoparticles. The recoilless fraction was determined as function of milling time and was consistent with the observation – for the first time in literature – of a distribution of recoilless fractions in the studied specimens. The saturation magnetization, remanence magnetization and coercive field were derived from the hysteresis loops, recorded at 5 K and 5 T. The zero-field-cooling-field-cooling measurements were obtained in a magnetic field of 200 Oe and the blocking temperature was determined. Our results show new features of the behavior of nickel ferrite nanoparticles under mechanochemical activation with and without graphene.

Meltwater chemistry and characteristics of particulate matter deposited in snow as indicators of anthropogenic influences in an urban area.

A geochemical study of snow from the industrial town of Maribor (Slovenia) was performed. Concentrations of 61 elements in meltwater were determined, and a detailed semi-quantitative and qualitative analysis of individual PTE-bearing particles deposited in snow was performed with SEM/EDS. The physico-chemical characteristics of meltwater reflect the influence of winter road maintenance (high electrical conductivity and high Ca and Na concentrations close to the main roads) and industrial activities. Particulate matter deposited in snow consists mainly of carbonates and silicates, followed by carbon-rich particles and PTE-bearing particles. A higher abundance of PTE-bearing particles is typical for the industrial zones. The size, morphology and chemical composition of 4415 PTE-bearing particles were studied. They were organised into nine groups based on their characteristics. The majority were assigned to the group of Fe-oxides, which includes mostly angular particles of unidentified origin. Several groups of particles of anthropogenic origin were determined, mainly from industrial metal-processing activities. These particles include spherical Fe-oxides, Fe-alloys, other metal alloys and spherical Si-particles. Spherical Fe-oxides are typical for the Tezno industrial zone, while Fe-alloys, namely Fe-Cr (Cu, Mn, Ni) shavings and other metal alloys (Cu-Zn (Cl, Fe) shavings) are typical for the Melje industrial zone. The presence of naturally occurring mineral particles (e.g. zircon, ilmenite, monazite) reflects the influence of natural/geogenic sources on the composition of particulate matter deposited in snow. The presented study confirmed that snow is a very promising medium for the geochemical study of urban environments, especially for the identification of anthropogenic sources of particulate matter.

Chemical characteristics of particulate matters and their emission sources over Varanasi during winter season

The chemical composition of particulate matter impacts both human health and climate. In this study, the chemical characteristics of particulate matter was measured for four months (November 2016–February 2017) at Varanasi, which is located in the middle of the Indo-Gangetic Basin (IGB). The daily observed mean values of PM10 and PM2.5 are 134 ± 48 and 213 ± 80 μg/m3, respectively, which exceeds both national and international standards. The average value of PM2.5/PM10 ratio is 0.64 ± 0.16 which indicates a relatively higher fraction of fine particles that are attributed to anthropogenic emission sources (biomass/post-harvest burning) as corroborated by MODIS fire counts and back trajectory analysis. Ion chromatographic measurements showed that SO42−, Cl−, K+, NO3−, Na+, Ca2+, Mg2+ are the major ionic species present in the aerosol. Scanning Electron Microscopy with Energy Dispersive X-Ray (SEM–EDX) analysis shows the prevalence of carbon-rich particles at Varanasi which is likely due to biomass burning and other anthropogenic sources.

Real-time physiochemistry of urban aerosols during a regional haze episode by a single-particle aerosol mass spectrometer: Mixing state, size distribution and source apportionment

Regional haze pollution can normally be divided into four stages comprising pre-accumulation, explosion, duration and dissipation, under which the physiochemical characteristics of aerosols were clearly distinct. In this study, the chemical compositions and mixing state of aerosols and their source apportionments during a regional haze pollution process in the North China Plain (NCP) were comparably discussed for the different haze evolution stages. Six main particle groups were identified, including carbon-rich particles (53.17%), K-rich particles (27.41%), heavy-metal particles (10.9%), sodium particles (5.61%), dust particles (1.62%) and ammonium particles (1.29%). Subsequently, the chemical components and size distributions of aerosols were found to vary during the different haze stages. Contrary to the OCEC, K–CN, Cu and Pb particles, the EC-nitrate, EC-secondary and Fe particle groups had increasing proportions with the development of the haze events. The fraction of K particles was higher during the pre-accumulation stage and descended rapidly during the subsequent haze stages. In contrast to the OCEC particles, the EC-nitrate and EC-secondary particles from 0.6 to 1.2 μm increased significantly with haze deterioration, implying the enhancement (decline) of aged (primary) carbonaceous particles during the haze episode. The source contributions of PM2.5 changed with the evolution of the haze events, with the largest percentage up to 52.23% from residual and industry emissions during the explosion stage. In contrast to industry and direct combustion emissions, the aging process and traffic emission contributed increasingly with the aggravation of the haze episodes, with higher fractions of 33.17% and 15.57%, respectively, throughout the duration stage.

Design and Development of an Innovative Barrier Layer in Vanadium Redox Flow Batteries

Vanadium Redox Flow Battery (VRFB) is an electrochemical energy storage technology that exploits red-ox reactions of vanadium ions dissolved in acidic solutions to convert electrical energy into and from chemical energy. VRFB is an interesting and promising technology because of its high efficiency, independent energy to power ratio, high flexibility and long cycle life [1]. However, VRFB commercialization is still hindered by some technological issues, among which is the capacity loss induced by the undesired transport of vanadium ions across the ion-exchange membrane. Depending on the nominal operating condition, the choice of suitable membrane for VRFB application results from the trade-off between low vanadium permeability and high proton conductivity.Nafion® is widely used in VRFB: it presents high conductivity and good mechanical and chemical stability, but it is not ideally selective towards vanadium ions. This implies the adoption of thicker membrane to limit capacity loss, leading to increased ohmic loss and system costs [2]. Alternative cation exchange membranes (CEMs) are SPEEK or SPI that are promising because of their reduced permeability, but the low conductivity and stability hinder their competitiveness with respect to Nafion®. Anion exchange membranes (AEMs) are interesting alternatives, but the poor chemical stability and low conductivity limit their application in VRFB. Amphoteric ion exchange membranes (AIEM) combine the functional groups of both CEM and AEM, obtaining both low permeability and good conductivity. However, the complex preparation results in high costs [3].In this work, an additional selective layer, described in the patent WO 2019/197917, was deposited on a commercial cation exchange membrane. The selective layer, termed as barrier, is a porous component in which pores size, tortuous path, thickness and the composition are designed to improve layer selectivity towards vanadium ions. The barrier was manufactured with reactive spray deposition technology (RSDT), which is a flame-based synthesis process unique to Dr. Radenka Maric’s research group. Fabrication of the barrier layer by RSDT is a one-step process in which carbon-rich particles are synthesized in the flame and a mixture of commercial carbon black particles and ionomer is sprayed directly onto the membrane. In this work different barrier morphologies have been designed, manufactured and tested.The barrier layer was tested in a 25 cm2 cell during cycles at constant capacity in both charge and discharge [4]. After each charge and discharge step the cell was kept in OCV for 90 seconds in order to acquire cell OCV and get an insight into battery state of charge (SoC). Figure 1 reports the evolution of SoC after each step of charge: it is worth noting that the VRFB with barrier presents a significant reduction of SoC decay (i.e., capacity loss) compared to a reference VRFB employing Nafion® 115. Moreover, the VRFB with barrier exhibits a slightly higher efficiency and a good stability in time.In addition to electrochemical testing, the structure of the barrier layer was characterized using TEM, SEM and nitrogen adsorption. TEM and nitrogen adsorption provide information on pore structure and pore-size distribution, which can be related to the performance of the barrier layer during cell testing, while SEM shows that the coating is uniform in thickness and consistent from sample to sample.

Oxygen content control in metal injection molding of 316L austenitic stainless steel using water atomized powder

316 L stainless steel samples are fabricated using metal injection molding in which water atomized 316 L powder containing 4200 ppm oxygen is used as the raw material. Oxygen not only hampers the sintering process but also proves to be detrimental to the ductility and corrosion resistance of the sintered sample. It is found that when the 316 L powder is doped with small amount of graphite (0, 500, 1000, 1500 and 2000 ppm), its oxygen content can be effectively reduced via the carbon-oxygen reaction during sintering. As the carbon dosage increases from 0 to 1500 ppm, the sintered density, elongation and pitting potential of the sintered samples are effectively improved due to the decreased oxygen contents in them. However, when 2000 ppm graphite is added, the sample becomes overdosed with carbon. The excessive carbon remains in the material and forms carbon-rich particles during sintering, which has significant adverse effects on the sintering process as well as the ductility and corrosion resistance of the sintered sample.

Graphene oxide nanoparticles in the interstellar medium

ABSTRACT Dust particles play a major role in the formation, evolution and chemistry of interstellar clouds, stars, and planetary systems. Commonly identified forms include amorphous and crystalline carbon-rich particles and silicates. Also present in many astrophysical environments are polycyclic aromatic hydrocarbons (PAHs), detected through their infrared emission, and which are essentially small flakes of graphene. Astronomical observations over the past four decades have revealed a widespread unassigned ‘extended red emission’ (ERE) feature which is attributed to luminescence of dust grains. Numerous potential carriers for ERE have been proposed but none has gained general acceptance. In this Letter it is shown that there is a strong similarity between laboratory optical emission spectra of graphene oxide (GO) and ERE, leading to this proposal that emission from GO nanoparticles is the origin of ERE and that these are a significant component of interstellar dust. The proposal is supported by infrared emission features detected by the Infrared Space Observatory (ISO) and the Spitzer Space Telescope.

Characteristics and mixing state of aerosol at the summit of Mount Tai (1534 m) in Central East China: First measurements with SPAMS

The size-resolved chemical composition and mixing state of single particles were observed by using single particle aerosol mass spectrometry (SPAMS) from May 12 to June 8, 2017. A total of 979,899 particles were successfully ionized to identify 6 main particle groups including carbon-rich particles (47.66%), K-rich particles (28.78%), heavy-metal particles (10.12%), sodium particles (8.86%), dust particles (3.89%), and ammonium particles (0.67%). The wind direction and speed had large impacts on the proportion of carbonaceous aerosol particles and had little influence on heavy-metal particles. The relative humidity (RH) had great impacts on the chemical components of aerosol particles. The proportion of secondary particles increased, while the primary particles diminished as RH increased. The proportion of carbon-rich particles decreased with increasing particle size. However, the size distributions varied significantly for different types of carbonaceous particles. Sodium particles and heavy-metal particles were mainly concentrated at sizes larger than 1 μm. K-rich particles had a maximum proportion at 0.5–1.0 μm. The number fraction of ammonium particles predominated chiefly at 0.6–2.0 μm. It has been found that aerosol particles, mainly from burning processes, were mixed with 36 [C3]+ to different degrees at Mt. Tai. A high proportion of ammonium particles were mixed with organics and elemental carbon (OCEC), elemental carbon-sulfate (EC-sulfate), and elemental carbon-secondary (EC-secondary) particles, while few of these particles were mixed with EC-nitrate particles, which indicated that the ammonia in the air was inclined to combine with organic species and sulfate. A higher proportion of atmospheric particles mixed with nitrate were observed compared to those mixed with sulfate.

Elemental composition of suspended particles across the southeastern continental shelf off the coast of North Florida and South Georgia: Provenance, transport, fate and implications to mid-outer shelf water column processes.

This paper reports on the chemistry of suspended particulates collected in waters of the southeastern US continental shelf off the coasts of North Florida and South Georgia. Approximately 350 suspended sediment samples were analyzed for particulate organic carbon and nitrogen (POC and PON), particulate aluminum and calcium and a suite of trace metals which included particulate alkaline earths (magnesium, strontium, barium), particulate rare earth metals (lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium and dysprosium), particulate transition metals (cobalt, copper, iron, manganese, nickel. scandium, titanium and vanadium) and others: particulate cadmium, zinc, thorium and uranium. The samples were collected in the fall of 1987 during a multidiscipline expedition (FLEX) focused on cross shelf exchange of water and materials during northward wind stress and fall Gulf Stream intrusions. Although samples were analyzed shortly after collection, archived data have not been previously presented. Results are interpreted with regard to how they relate to particle provenance, transport and fate.Results indicate that significant influence of terrestrial sources of suspended particles is limited to the inner shelf, however the concentrations of some metals, such as rare earths, appear to reflect this provenance across the entire shelf. Mid-outer shelf particles are dominated by re-suspended biogenic carbonates and biogenic organic carbon rich particles formed in response to Gulf Stream up welled nutrients. Particulate trace element concentrations and primary production in mid-outer shelf waters are interpreted as a response to not only nutrient, but also trace metal enrichment of up welled Gulf Stream water intruded onto the shelf. Based on particle chemistry, micro nutrients such as Fe in upwelled waters may be limiting in sustaining mid-outer shelf production. Other trace metals such as Sc appear to be enriched due to adsorption on organic rich particles. And the formation SrSO4 particles, originating from Acantharian spicules, appear to create an environment for the precipitation of barite in outer shelf surface waters.