Fluffy Layer Research Articles

High-temperature mechanical performances of SiC whisker in-situ toughened 3DN C/SiC countersunk bolts prepared by chemical vapor infiltration

High performance bolts, made of continuous fiber reinforced silicon carbide composites (C/SiC), are crucial to the design and preparation of the hot-end C/SiC components with large complex structures both in aerospace and aeronautical fields. In this work, in-situ grown SiC whiskers were uniformly introduced into the porous laminated 3DN C/SiC countersunk bolt, in order to improve the brittle nature of the 3DN C/SiC threads. Results showed that 7 % increase of tensile strength of the 3DN C/SiC countersunk bolts was achieved via in-situ grown SiC whiskers, and a fatigue life of 106 cycles was also passed. The stud fracture morphologies indicated that the SiC whiskers grew within the woven pores and toughened the layered SiC matrix, so that the load transfer between the layered SiC matrix and carbon fibers was improved under tension. Further high temperature tests showed that the tensile and the shear strengths of the in-situ toughened 3DN C/SiC countersunk bolts were degraded to 64.74 % and 28.83 % at 1000 °C in air respectively. During the thermal exposure, the carbon fibers were largely consumed by oxidation, while the SiC whiskers grew slender and formed a fluffy layer to partially reinforce the SiC matrix. The synergy effect of SiC whiskers and carbon fibers to hinder crack propagation and to toughen the SiC matrix contributes to the above mechanical properties of the bolts.

Subaqueous silt ripples measured by an echo sounder: Implications for bed roughness, bed shear stress and erosion threshold

Bedforms like ripples are widely distributed in the coastal zone. They influence the bed roughness thus the estimation of bed shear stress and associated sediment transport. An echo sounder was mounted on a bottom-supported tripod intended to measure the erosion and deposition of seabed in the subaqueous Yellow River Delta, China. However, variations in bed elevation are found to be not the net erosion or deposition at the observation site, but the migration of silt ripples which were generated by waves and pushed back and forth or flattened off by the tidal currents. Ripple heights were observed to be within 0.1–0.7 cm and were used for testing the model of Nielsen (1981). The model overestimated the height of silt ripples as it was developed for sands, but the deviation can be well addressed by incorporating a linear modification (R2 = 0.79). Alternatively, a new model specifically for silt ripple height was regressed from the field data with R2 up to 0.78. The existence of silt ripples increases the bed shear stress by 4 times due to the additional bed roughness. A “fluffy layer” overlies the consolidated seabed, therefore, net seabed erosion occurs after the “fluffy layer” is resuspended. A representative critical bed shear stress for net seabed erosion in the study area was found to be 0.8 Pa. The echo sounder can be an alternative tool for observing silt ripples in coastal regions like the Yellow River Delta where the water is too turbid for underwater videos. The proposed model infers silt-ripple features from bed grain size and flow condition and provides a quick estimate for bed roughness improving the understanding on sediment transport.

Evaluation of Corrosion Inhibition of Carbon Steel in Crude Oil by Using Different Green Corrosion Inhibitors and Various Rotation Speeds

Corrosion is a major problem in the petroleum industry, which often occurs to crude oil production equipment and to petroleum product transportation pipelines as well. In order to protect these parts from corrosion, much small quantities of inhibitors are constantly injected, which gradually formulate a fluffy layer of inhibitor over the metal surface so as to protect it from corrosion. Recently, the impact of corrosion inhibitors on the environment has been raising more attention and concern. New regulations related to environment have been designated, imposing a change in the use of toxic chemicals to the utilization of the so-called “green chemicals”. Experiments on carbon steel corrosion protection have been conducted in a medium of crude oil has an API gravity of 30.6 by using different concentrations, ranging between 100 – 400 ppm of different green inhibitors such as corn oil, sunflower oil, flaxseed oil and castor oil with a different rotation speeds, namely, 0, 500, 1250 and 2000 rpm. The weight loss outcomes have showed that the rate of carbon steel corrosion in the crude oil decreases with the rise of inhibitors’ concentration, while corresponds with the increase of the rotational speed. In addition, it was found that the maximum inhibition efficiency achieved for the inhibitors corn oil, sunflower oil, flaxseed oil and castor oil in crude oil was using a concentration of 400 ppm, a rotation speed of 0 rpm and an ambient temperature (25 °C) is 41.85%, 50.76%, 63.55% and 92.63%, respectively.

First Report of Brown Spot of Dekopon Fruit Caused by Cladosporium tenuissimum in China.

Dekopon citrus (Citrus reticulata Shiranui) is a three-way hybrid (Citrus unshiu Marcov. × C. sinensis Osbeck × C. reticulata Blanco) developed in Japan in 1972. This citrus is popular in China due to its sweet and tender taste (Lim 2012). In November of 2021, a brown spot disease on Dekopon fruits with about 20% disease incidence was observed in an orchard of the Institute of Citrus Research in Ganzhou, Jiangxi Province, China. Initially, the symptoms appeared as slightly sunken deep red to purple spots on the fruit surface, with the disease progression, lesions became brown to brown-black large necrotic regions covered with a fluffy layer of gray spores. Infected fruits were surface sterilized with 70% ethanol for 30 sec and rinsed three times with sterile distilled water. Diseased tissues from the edge of lesions were cut into small segments, placed onto potato dextrose agar and incubated at 25℃ for 7 days. Ten single-spore isolates were obtained in total. Fungal colonies were olive green to dark green, velvet-like in texture and sporulated abundantly, surrounded by grayish-white hyphae. Conidiophores were subcylindrical, straight, septate, solitary or in clusters of two to three, and ranged in size from 65 to 550 × 3.8 to 6.3 µm (x ̅= 261.7 ± 60.5 × 5.2 ± 0.4 µm, n=50). Ramoconidia were cylindrical，aseptate, and 10 to 22 × 2.8 to 4.5 µm (x ̅= 15.5 ± 1.4 × 4.0 ± 0.9 µm, n=50). Conidia were lemon-shaped to oval-shaped, smooth-walled, and 1.8 to 5.0 × 1.4 to 2.5 µm (x ̅= 3.9 ± 0.4 × 2.2 ± 0.2 µm, n=50). The morphological characteristics of the pathogen were consistent with those of Cladosporium tenuissimum Cooke (Li et al. 2021). For further identification, DNA was extracted from two representative isolates. The internal transcribed spacer (ITS) region, translation elongation factor (EF1-α), and actin (ACT) were amplified by using primers ITS1/ITS4, EF1-728F/EF1-986R, and ACT-512F/ACT-783R (Bensch et al. 2012), respectively. ITS (OM232067, OM232068), EF1-α (OM256525, OM256526) and ACT (OM256529, OM256530) sequences were deposited in GenBank. Multi-gene (combined data set of ITS, EF1-α and ACT) phylogenetic analysis was conducted using the Maximum Likelihood method (Nguyen et al. 2015). Based on the morphological characteristics and the molecular data, two fungal isolates were identified as C. tenuissimum. To evaluate pathogenicity, fifteen fruits were surface sterilized with 1% NaClO solution for 30 sec, rinsed twice with sterile distilled water and dried. Dekopon fruits (n=10) were wounded with a sterile needle and inoculated with a 10 µL drop of conidial suspension (1 × 106 conidia/mL) of isolate GZCJ-1, followed by incubation at 25℃ and 80% relative humidity. The controls (n=5) were treated with sterile water and maintained under the same conditions. Five days after inoculation, small brown sunken spots were observed on the wounded and inoculated fruits. After 7 days, lesions were coated by a layer of brown conidia that were similar to those described above, whereas control remained symptomless. Pathogenicity test was repeated twice. Cladosporium tenuissimum was consistently re-isolated from inoculated fruits and confirmed by morphological and molecular data, fulfilling the Koch's postulates. To our knowledge, this is the first report of C. tenuissimum causing the brown spot of dekopon fruit in China and perhaps the world. The disease may become the potential risk for fruit production, making fruits unfit for marketing purposes, and the appropriate management actions will be necessary.

Elemental Composition of Particulate Matter in the Euphotic and Benthic Boundary Layers of the Barents and Norwegian Seas

The increasing influence of Atlantic inflows in the Arctic Ocean in recent decades has had a potential impact on regional biogeochemical cycles of major and trace elements. The warm and salty Atlantic water, entering the Eurasian Basin through the Norwegian Sea margin and the Barents Sea, affects particle transport, sink, phyto-, and zooplankton community structure and could have far-reaching consequences for the marine ecosystems. This study discusses the elemental composition of suspended particulate matter and fluffy-layer suspended matter derived from samples collected in the Barents Sea and northern Norwegian Sea in August 2017. The mosaic distribution of SPM elemental composition is mainly determined by two factors: (i) The essential spatial variability of biological processes (primary production, abundance, and phytoplankton composition) and (ii) differences in the input of terrigenous sedimentary matter to the sea area from drainage sources (weak river runoff, melting of archipelago glaciers, etc.). The distribution of lithogenic, bioessential, and redox-sensitive groups of elements in the particulate matter was studied at full-depth profiles. Marine cycling of strontium in the Barents Sea is shown to be significantly affected by increasing coccolithophorid bloom, which is associated with Atlantic water. Mn, Cu, Cd, and Ba significantly enrich the suspended particulate matter of the benthic nepheloid layer relative to the fluffy layer particulate matter within the benthic boundary layer.

Near-IR photometry of the small Uranian satellites with Keck at phase angles 0–2°

We present photometric measurements of the seven brightest small inner moons of Uranus (Puck, Belinda, Rosalind, Portia, Juliet, Desdemona and Cressida) obtained with the Keck II telescope at 1.6 and 2.2μm at phase angles of 0.026∘ and 0.36∘ in October–November 2019. We also applied our new calibration technique to the August 2015 data at 2.02∘ from Paradis et al. (2019). We show that the phase curves in the near-infrared are very similar to those at visible wavelengths, which suggests that the opposition surge at near-infrared wavelengths is also caused by both shadow hiding and coherent backscatter.All moons are either neutral in color or slightly reddish; Puck and Portia show a roughly 20% increase in their 2.2μm reflectivity compared to that at 1.6μm. This suggests that these moons are not icy bodies like the large classical moons; they are likely covered by a fluffy (∼80% void space) layer of carbonaceous material.

In situ observations of hydro-sediment dynamics on the abandoned Diaokou lobe of the Yellow River Delta: Erosion mechanism and rate

In situ observations of suspended sediment concentrations (SSCs), bed elevations, and concurrent hydrodynamics were conducted with an instrumented tripod on an abandoned lobe of the Yellow River Delta in the winter of 2014–2015. Four typical winter storms were recorded, but no significant local seabed erosion was observed at the observation site. Nevertheless, the sediment dynamic processes in this area were inferred from the data. The bottom sediment is eroded by the waves induced by strong northerly winds, and the erosion source area is located northwest of the observation point. Therefore, during strong wind and wave conditions, the observation point forms a horizontal SSC gradient, which generally decreases from west of to east of the observation point. The gradient mainly passes the observation site through diurnal tidal horizontal advection and is intermittently influenced by advection by the residual current driven by sea‒land wind and semidiurnal tides. Additionally, local resuspension of a “fluffy layer” on the seabed by the semidiurnal tide occurs. Flood tides transport the SSC gradient southeasterly, while ebb tides push the gradient back periodically. An asymmetry in the suspended sediment transport rate exists and is estimated to be 1.77 kg m−2 s−1 to the southeast. A new parameter, the net loss rate of suspended sediment, is defined and is estimated to be 0.0109 g L−1 h−1. These findings provide a better understanding of the erosion mechanism of the Diaokou lobe and some new ideas/methods for analysing hydrodynamics and sediment dynamics with a single-point measured dataset.

High-Resolution Reconstruction of Dissolved Oxygen Levels in the Baltic Sea With Bivalves – a Multi-Species Comparison (Arctica islandica, Astarte borealis, Astarte elliptica)

An increasing area of shallow-marine benthic habitats, specifically in the Baltic Sea, is affected by seasonal oxygen depletion. To place the current spread of oxygen deficiency into context and quantify the contribution of anthropogenic ecosystem perturbation to this development, high-resolution archives for the pre-instrumental era are needed. As recently demonstrated, shells of the bivalve mollusk, Arctica islandica fulfil this task with molar Mn/Cashell ratios as proxies for dissolved oxygen (DO) levels in the water column. Since the ocean quahog is inhomogeneously distributed in the Baltic Sea and may not be present in museum collections or found throughout sedimentary sequences, the present study evaluated whether two other common bivalves, Astarte elliptica and Astarte borealis can be used interchangeably or alternatively as proxy DO recorders. Once mathematically resampled and corrected for shell growth rate-related kinetic effects and (some) vital effects, Mn/Cashell data of all three species (age ten onward in A. islandica) were statistically significantly (p < 0.0001) linearly and inversely correlated to DO concentration in the free water column above seafloor (r = –0.66 to –0.75, corresponding to 43 to 56% explained variability). A. elliptica may provide slightly more precise DO data (1σ error of ±1.5 mL/L) than A. islandica or A. borealis ( ± 1.6 mL/L), but has a shorter lifespan. Both Astarte species show a stronger correlation with DO than A. islandica, because their biomineralization seems to be less severely hampered by oxygen and salinity stress. In turn, A. islandica grows faster resulting in less time-averaged data. During youth, the ocean quahog typically incorporates a disproportionately large amount of manganese into its shell, possibly because food intake occurs directly at the sediment-water interface where Mn-rich porewater diffuses out of the sediment. With increasing age, however, A. islandica seems to generate a gradually stronger inhaling water current and takes in a larger proportion of water farther away from the fluffy layer. As demonstrated here, all three studied species can be used as DO archives, though species-specific limitations should be kept in mind.

Multiscale Superposition and Decomposition of Field‐Measured Suspended Sediment Concentrations: Implications for Extending 1DV Models to Coastal Oceans With Advected Fine Sediments

AbstractOne‐dimensional vertical (1DV) diffusion‐settling models are practical tools for sediment transport analysis of sands, which is mostly a local process. However, for fine sediments, the observed concentrations C(t) can be mixed via horizontal advection (HA) due to the lower settling velocity, which makes the C(t) not necessarily a local process, thus making 1DV models invalid. It is important to determine the qualitative significance of HA or quantitatively separate HA signals when applying 1DV models to environments with advected fine sediments. Here, novel methods are combined to (1) qualitatively identify the physical mechanisms underlying C(t) variations and determine whether HA is significant via multiscale frequency superposition and (2) quantitatively decompose C(t) components according to their physical mechanisms via spectral filter decomposition. In situ observational data of C(t) and concurrent hydrodynamics in the subaqueous Yellow River Delta is employed to analyze the methods' performance. The decomposed signals are reasonable because they can be interpreted in light of other observed physical processes. The results indicated that M2 tidal advection contributed 8.30% by carrying sediments from 1.6 km upstream of the flood tides, M4 and M6 + M8 tidal resuspension contributed 4.16% and 3.96%, respectively, by periodically resuspending a “fluffy layer.” Waves resuspended sediments from an erosion center 5 km upstream of the flood tides and contributed to 76.49% of the elevated C(t). The proposed methods can exclude HA signals from the measured C(t) to increase the applicability of 1DV models to environments with advected fines when C(t) and hydrodynamics are measured.

Stainless steel cloth modified by carbon nanoparticles of Chinese ink as scalable and high-performance anode in microbial fuel cell

Microbial fuel cells (MFCs) have various potential applications. However, anode is a main bottleneck that limits electricity production performance of MFCs. Herein, we developed a novel anode based on a stainless steel cloth (SC) modified with carbon nanoparticles of Chinese ink (CI) using polypyrrole (PPy) as a building block (PPy/CI/SC). After modification, PPy/CI/SC showed a 30% shorten in start-up time (36.4 ± 3.3 h vs. 52.3 ± 1.8 h), 33% increase in the maximum current (12.4 ± 1.4 mA vs. 9.3 ± 0.95 mA), and 2.3 times higher in the maximum power density of MFC (61.9 mW/m2vs. 27.3 mW/m2), compared to Ppy/SC. Experimental results revealed that carbon nanoparticles were able to cover SC uniformly, owing to excellent dispersibility of carbon nanoparticles in CI. The attachment of carbon nanoparticles formed a fluffy layer on SC increased the electrochemically-active surface area by 1.9 times to 44.5 cm2. This enhanced electron transfer between the electrode and bacteria. Further, embedding carbon nanoparticles into the PPy layer significantly improved biocompatibility as well as changed functional group contents, which were beneficial to bacteria adhesion on electrodes. Taking advantage of high mechanical strength and good conductivity, a large-size PPy/CI/SC was successfully prepared (50 × 60 cm2) demonstrating a promising potential in practical applications. This simple fabrication strategy offers a new idea of developing low cost and scalable electrode materials for high-performance energy harvesting in MFCs.

Communication—Platinum and Tin Oxide Dispersed in a Fluffy TiO2 Nanolayer for Electrocatalytic Reduction of Oxygen

Pt catalysts perform well in the oxygen reduction reaction (ORR), but they suffer weak bonding with carbon supports, leading to catalyst degradation. We introduce a fluffy titanium dioxide (TiO2) nanolayer with a very high specific surface area as support, made possible with a new condensed layer deposition technique. When Pt and SnO2 were incorporated in it as co-catalyst, a remarkable improvement in ORR onset potential was achieved at 930 mV vs RHE in sulfuric acids. The mass activity was 2.66 times that of Pt/C at 900 mV. The fluffy layer stabilized SnO2 and together, they enabled a pronounced ligand effect.

Fluffy Polyfluoroalkoxy Layer Produced by Air Plasma Spraying Based on “Grapeshot” Effect

Fluoropolymers with low surface energies are widely used in friction reduction, anti-corrosion, and anti-ice coatings. The fabrication of hierarchical micro- and nanostructures with fluoropolymers is beneficial for industrial application. In this study, a superhydrophobic composite coating was prepared by an improved air plasma spraying technique using feedstocks of Cr and polyfluoroalkoxy (PFA). A fluffy structure was found on the surface of the coating. A similar structure could not be found on the surface when the Fe and PFA powders were used as the feedstocks under the same condition. The characterization results suggest that the fluffy layer was derived from PFA. The formation of such a fluffy structure was attributed to the evaporation of Cr during spraying and their interaction with PFA droplets. This spraying method provides a new route for preparing hierarchical polymers, which have potential applicability in functional coatings.

Variability of bottom friction velocity along the inflow water pathway in the Baltic Sea

Abstract Using a regional circulation model of the Baltic Sea with the horizontal resolution of 0.5 nautical miles and with an open western boundary, time series of bottom friction velocity and bottom salinity were simulated for the period of April 2010–July 2016 and analysed at specific points of interest along the inflow water pathway. The model reproduces reasonably well observations of the bottom currents and salinity at monitoring stations in the Bornholm and Gotland deeps. The bottom friction velocity at chemical warfare dumpsites in the Bornholm and Gotland basins was found to be permanently below the resuspension thresholds for the suspended particulate matter and fine sand, and even the Major inflows could not violate the balance. Occasionally the bottom friction velocity may exceed the resuspension threshold for the fine biogenic material (fluffy layer and cysts) almost everywhere in the deep Baltic basins, though additional studies are necessary to assess the likelihood of potential transport and dispersion of the chemical warfare by-products due to high sorption ability of the fine biogenic material.

A new disease of strawberry, fruit rot, caused by Geotrichum candidum in China.

A new disease of strawberry (Fragaria ananassa Duch.) was discovered in the Lianqiao strawberry planting base in Shaodong County, in Hunan Province, China. In the early disease stage, leaves showed small black spots surrounded by yellow halos, while in the late stage, a white fluffy layer of mold appeared. Fruits were covered with a white layer of mold. The symptoms were observed using in vitro inoculation experiments. After the spray-inoculation of stabbed leaves, small black spots surrounded by yellow halos occurred on leaves, with no clear boundary between diseased and healthy areas. In the late stage, disease spots gradually expanded and a white fluffy layer of mold formed under humid conditions. Unstabbed leaves had almost no disease occurrence after spray-inoculation. After the spray-inoculation of stabbed fruits, by the late stage, a dense white layer of mold formed. According to Koch’s postulates, the isolated strain was verified as a pathogen. The pathogenic strain, designated SDLQ16, was isolated from diseased fruit by dilution method and tentatively identified as G. candidum based on the culture characteristics, morphologies, physio-biochemical analysis, and phylogenetic analysis of the rDNA-ITS sequence. The fungus was able to grow on different culture mediums, with a broad range of nutrition. The colonies on PDA medium were raised and pale white, with a neat edge and visible hyphae. The hyphae were friable but the spores were developing. Basal hyphae rapidly grew close to the medium to 3.2–4.2 µm in diameter, with septa and forked branches at acute angles. The solitary or beaded spores with smooth surfaces were 3.5–7.5 µm in length and 3.5–4.5 µm in width. This strain was able to gelatin liquefaction, proteolysis, grease, peptonised milk, urea, and so on. The pathogenicity on strawberry from strong to weak was: fruit > leaf > stem. A BLAST algorithm was used to query SDLQ16’s rDNA-ITS sequence (cloned and deposited as GenBank number KU373122) against the NCBI database, and it was located in the Acinetobacter sp. branch of a phylogenetic tree. SDLQ16 was most closely related to Geotrichum candidum ATCC34614 (GQ4580314.1), with a sequence similarity of 99%.

Effects of Cs2CO3 Additive in KOH Electrolyte Used in Ni/MH Batteries

The effects of Cs2CO3 addition in a KOH-based electrolyte were investigated for applications in nickel/metal hydride batteries. Both MgNi-based and Laves phase-related body-centered cubic solid solution metal hydride alloys were tested as the anode active materials, and sintered β-Ni(OH)2 was used as the cathode active material. Certain amounts of Cs2CO3 additive in the KOH-based electrolyte improved the electrochemical performances compared with a conventional pure KOH electrolyte. For example, with Laves phase-related body-centered cubic alloys, the addition of Cs2CO3 to the electrolyte improved cycle stability (for all three alloys) and discharge capacity (for the Al-containing alloys); moreover, in the 0.33 M Cs2CO3 + 6.44 M KOH electrolyte, the discharge capacity of Mg52Ni39Co3Mn6 increased to 132%, degradation decreased to 87%, and high-rate dischargeability stayed the same compared with the conventional 6.77 M KOH electrolyte. The effects of Cs2CO3 on the physical and chemical properties of Mg52Ni39Co3Mn6 were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, inductively coupled plasma, and electrochemical impedance spectroscopy. The results from these analyses concluded that Cs2CO3 addition changed both the alloy surface and bulk composition. A fluffy layer containing carbon was found covering the metal particle surface after cycling in the Cs2CO3-containing electrolyte, and was considered to be the main cause of the reduction in capacity degradation during cycling. Also, the Cs2CO3 additive promoted the formations of the C–O and C=O bonds on the alloy surface. The C–O and C=O bonds were believed to be active sites for proton transfer during the electrochemical process, with the C–O bond being the more effective of the two. Both bonds contributed to a higher surface catalytic ability. The addition of 0.33 M Cs2CO3 was deemed optimal in this study.

Opposition effect on comet 67P/Churyumov-Gerasimenko using Rosetta-OSIRIS images

We aim to explore the behavior of the opposition effect as an important tool in optical remote sensing on the nucleus of comet 67P/ Churyumov-Gerasimenko (67P), using Rosetta-OSIRIS images acquired in different filters during the approach phase, July-August 2014 and the close flyby images on 14 of February 2015, which contain the spacecraft shadow. We based our investigation on the global and local brightness from the surface of 67P with respect to the phase angle, also known as phase curve. The local phase curve corresponds to a region that is located at the Imhotep-Ash boundary of 67P. Assuming that the region at the Imhotep-Ash boundary and the entire nucleus have similar albedo, we combined the global and local phase curves to study the opposition-surge morphology and constrain the structure and properties of 67P. The model parameters were furthermore compared with other bodies in the solar system and existing laboratory study. We found that the morphological parameters of the opposition surge decrease monotonically with wavelength, whereas in the case of coherent backscattering this behavior should be the reverse. The results from comparative analysis place 67P in the same category as the two Mars satellites, Phobos and Deimos, which are notably different from all airless bodies in the solar system. The similarity between the surface phase function of 67P and a carbon soot sample at extremely small angles is identified, introducing regolith at the boundary of the Imhotep-Ash region of 67P as a very dark and fluffy layer.

First results on determination of chlorophill A and its derivatives in the system of trapped sedimentary material–fluffy layer–bottom sediment of the Caspian Sea

The first data were obtained on the vertical chlorin flux in the water column and its accumulation in the upper layer of sediments of the Caspian Sea. Seasonal variability of the chlorine concentration in sedimentary matter was evaluated. The tendency of decrease in the phytoplankton-synthesized (allochtonous) organic matter content was revealed over approximately the past 60 years.

Effect of Surface Passivation on Photoelectrochemical Water Splitting Performance of WO3 Vertical Plate-Like Films

WO3 vertical plate-like arrays provide a direct pathway for charge transport, and thus hold great potential as working electrodes for photoelectrochemical (PEC) water splitting. However, surface recombination due to surface defects hinders the performance improvement. In this work, WO3 vertical plate-like arrays films with HfO2 passivation layer were fabricated via a simple dip-coating method. In the images of transmission electron microscope, a fluffy layer and some small sphere particles existed on the surface of WO3 plate. X-ray photoelectron spectroscopy (XPS) showed a higher concentration of Hf element than the result of energy-dispersive X-ray spectroscopy (EDX), which means that HfO2 is rich on the surface of WO3 plates. A higher photocurrent under visible light irradiation was gained with surface passivation. Meanwhile, the results of intensity modulated photocurrent spectrum (IMPS) and incident photon to current conversion efficiency (IPCE) indicate that HfO2 passivation layer, acting as a barrier for the interfacial recombination, is responsible for the improved photoelectrochemical performance of WO3 vertical plate-like arrays film.

The distribution of heavy metals in the near-bottom particulate matter, fluffy layer, and bottom sediments over the Yenisei profile in the Kara Sea

The chemical composition and concentrations of metals (Fe, Mn, Cu, Zn, and Cr) were determined for the first time in the marine basin at the water-bottom geochemical interface, including the particulate matter, fluffy layer (0.0–0.2 cm), and the surface layer of the sediments (0–2 cm). It was found that the content of metals in the aquatic particulate matter depended on the concentration of organic matter. The fluffy layer was enriched, compared to the underlying layers, by 5–10% in organic matter including the biomass of microorganisms, and by up to 50% in metals (to the maximum of doubled values for Zn). It is supposed that this low enrichment of the fluffy layer in metals was caused by the active near-bottom currents of marine basins.

Seasonal variations in methane concentrations and diffusive fluxes in the Curonian and Vistula lagoons, Baltic Sea

Expected seasonal variations in methane concentrations and diffusive fluxes from surficial sediments into near-bottom waters were investigated in autumn 2012 and winter 2013 in the Curonian and Vistula lagoons of the Baltic Sea, expanding on earlier findings for summer 2011. Methane concentrations in bottom sediments (upper ca. 2 cm) generally ranged from ca. 1 to 1,000 μmol/dm3, and in near-bottom waters from ca. 0 to 1 μmol/l. Highest concentrations were found in the Curonian Lagoon, plausibly explained by the influence of freshwater conditions and finer-grained, organic-rich sediments. Vistula Lagoon methane concentrations and fluxes are dampened by periodic saline water inflow from the open sea, intensifying sulphate reduction. Calculated diffusive methane fluxes from the upper sediment layer (usually 0–5 cm, i.e. excluding any fluffy layer) into near-bottom waters were highest—2.48 mmol/(m2 day)—in clayey silts of the Curonian Lagoon in autumn (September) 2012, contrasting strongly with the minimum value of 0.002 mmol/(m2 day) observed there in February 2013 under ice-covered conditions. Seasonal and even weekly variations in methane dynamics can be largely explained by two main drivers, i.e. wind and temperature, operating at various spatiotemporal scales via, for example, wind wave-induced resuspension of bottom sediments, and involving regional weather patterns including autumnal low-pressure zones over the Gulf of Gdansk.