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Due to high absorbance of UV light and low solid loading, the stereolithography-based additive manufacturing of gray-colored and dense Si3N4 ceramic is of significant difficulty and challenge. The effects of geometric properties of ceramic powders on the curing performance were investigated by studying the absorption difference of the Si3N4 ceramic particles with different colors and particle sizes and ultraviolet light. The results show that the transmission of ultraviolet light and curing performance of the darker Si3N4 ceramic slurry are much poor. Under the same particle size, the Si3N4 ceramic slurry using lighter particles presents the smaller scattering coefficient. The scattering coefficient (∼202) of the gray powder with ∼0.8 μm average particle size is the smallest. Under the same color, the larger the particle size, the smaller the scattering coefficient. The smallest scattering coefficient of the white powder with ∼2.0 μm average particle size is ∼110.

Silicon nitride (Si3N4) ceramic slurry with high-solid loading, low-viscosity and high curing depth was prepared by using a surface modifier (silane coupling agent) directly as the dispersant. The effect of the interaction between modified Si3N4 powders and prepolymer on rheological property, kinetic stability, wettability and curing property of the slurry was investigated. The stereolithography forming mechanism of the modified Si3N4 ceramic slurry was elucidated. It is revealed that the epoxy group of KH560 can easily form an ether covalent bond with the hydroxyl group of bisphenol A epoxy acrylate (EA). This makes submicron sized Si3N4 powder well-dispersed in the premixed liquid and leads to improved rheological properties and kinetic stability of the ceramic slurry. In particular, the ether covalent bond formed between surface modified Si3N4 powder and EA reduces the surface tension of the slurry and enhances the wettability of the cured slurry layer. KH560 acts as a molecular bridge linking EA to Si3N4 powder surface and forms an EA shell structure. Therefore, the refractive index difference between the Si3N4 powder and prepolymer reduces significantly by two orders of magnitude, leading to an increase in the curing depth. These findings could be crucial for the stereolithographic fabrication of high refractive index ceramics parts with high precision and complex geometries.

Photocurable gray-colored Si3N4 ceramic slurry with high solid loading, suitable viscosity and high curing depth is critical to fabricate dense ceramic parts with complex shape and high surface precision by stereolithography technology. In the present study, Si3N4 ceramic slurry with suitable viscosity, high solid loading (45 vol %) and curing depth of 50 μm was prepared successfully when surface modifier KH560 (1 wt%) and dispersant Darvan (1 wt%) were used. The slurry exhibits the shear thinning behavior. Based on the Beer-Lambert formula, Dp (the attenuation length) and Ec (the critical energy dose) of Si3N4 ceramic slurry with solid loading of 45 vol % were derived as 0.032 mm and 0.177 mJ/mm2, respectively. Si3N4 ceramic green parts with complex shape and high surface precision were successfully fabricated by stereolithography technology. After optimizing the debinding and sintering process for green parts, dense Si3N4 ceramics with 3.28 g/cm3 sintering density were fabricated. The microhardness and fracture toughness of as-sintered Si3N4 ceramics are ~14.63 GPa and ~5.82 MPa m1/2, respectively, which are comparable to those of the samples by traditional dry-pressed and pressureless sintering technology. These results show that ceramic stereolithography technology could be promising to fabricate high performance ceramics, especially for gray-colored monolithic Si3N4 ceramics.

Microplastics become one of the serious persistent pollutants in terrestrial environments, and thus may represent a threat to the quality of soil and inhabiting organisms. It is imperative to understand occurrence and distribution of microplastics in soils. In this study, a large-scale field survey encompassing 85 locations along the lower reaches of Yangtze River and estuary was performed to investigate the microplastics abundance in agricultural soils. Microplastics were isolated from all the samples and all depths (0–80 cm). The microplastics abundance in soils ranged from 4.94 items/kg to 252.70 items/kg, with an average of 37.32 items/kg. The most common microplastic type detected was Polypropylene (PP) occurring as white fragments with sizes ranging from 0.1 mm to 0.5 mm. Abiotic parameters such as soil pH and texture were the general factors being associated with microplastic abundance. Meantime, traffic was indicated as one important factor to affect the microplastic abundance. Overall, the road input seems to be the main source of microplastic pollution in agricultural areas along the Yangtze River and estuary. Further studies should elucidate the original of the plastic fragments in order to establish a baseline for regulative initiatives securing environmental protection.

Identification and quantification of the distribution, ecological risk, and sources of heavy metals in soils are essential for regional pollution control and management. In this study, spatial analysis (SA), GeogDetector model (GDM), and positive matrix factorization (PMF) model were combined to evaluate the status, ecological risk, and sources of heavy metals in soils from a typical coastal economic development area in Southeastern China. The mean contents of Cd, Pb, Cr, Cu, and Zn in the surface soils (0–20 cm) were 0.45, 41.72, 90.50, 47.86, and 145.33 mg/kg, respectively. In accordance, the mean contents of Cd exceeded the risk screening value for contamination of agricultural soil in China. Our results revealed that industrial and residential soils had higher enrichment of heavy metals than agricultural and fallow soils. Industrial production was the major driving factors influencing the spatial distribution of heavy metals. Soil OM and pH were found to be the most important factors affecting the potential ecological risk of heavy metals, followed by distance from the industrial enterprises and roads. Heavy metals in the study area were mainly originated from industrial emissions/atmospheric deposition, agricultural sources, and followed by natural sources. Therefore, regular monitoring and source control for heavy metals, especially for Cd, along with the integrated soil environmental management in the study area are crucial to ensure soil health and ecosystem security.

In this work, the anion in situ doped nickel hydroxide nanoparticles were electrochemically synthesized by different nickel salt solution. NO3−, Cl− and SO42− can be in situ intercalated into the cathodically deposited Ni(OH)2 sample (α-phase), while CH3COO− cannot be in situ intercalated into the cathodically deposited Ni(OH)2 sample (β-phase). The doping effect on the electrochemical performances of the synthesized sample is related with both of the size and the structure characteristic of the doped anions. On one side, the enlargement of lattice spacing is beneficial to H+/OH− transfer, and on the other side, the steric hindrance effect is restrictive to H+/OH− transfer. However, the NO3− intercalated Ni(OH)2 sample has the largest lattice spacing and the highest electrochemical performances due to its special planar structure characteristic and the effect on the dissociation energy of O-H bond in the charge-discharge process of Ni(OH)2.

Herein, we prepared a novel nickel iron-layered double hydroxide/reduced graphene oxide/nickel foam (NiFe-LDH/RGO/NF) electrodes by two step electrodeposition processes for oxygen evolution reaction (OER). The modification of NF by RGO increased the interface conductivity and electrochemical active surface areas (ECSA) of the electrode. The NiFe-LDH/RGO/NF electrode has shown higher catalytic activity with a lower overpotential of 150 mV at the current density of 10 mA cm −2 . The NiFe-LDH/RGO/NF electrode has also shown a small Tafel slope of 35 mV per decade due to the synergy effect between the larger ECSA and the conductive RGO interface. Furthermore, the electrodes exhibits almost 10 h stability under a general current density of 10 mA cm −2 .

The Yellow Sea Large Marine Ecosystem (YSLME) is an important socioeconomic zone in Asia, but has been deteriorated by various environmental pollutants over the last half century. However, comprehensive coastal pollution assessments, particularly for heavy metals (HMs), have been limited from an international perspective. Here, we first evaluate coastal HM pollution in sediment and water from 119 riverine, estuarine, and marine locations along the BS and Yellow Sea to perform a comparative assessment between the two countries of China and South Korea. The occurrence, distribution, sources, multimedia fate, interactions, associated environmental factors, and potential ecological risks relating to the HM pollution are widely addressed. Eight typical HMs (As, Hg, Zn, Cu, Pb, Cd, Cr, and Ni) were targeted in both sediments and water, and in situ water properties (pH, dissolved oxygen, salinity, and temperature) and sediment properties (pH and organic matter (OM) content) were analyzed. The results indicated that As, Cd, Cr, Cu, Ni, and Pb concentrations in water were higher in the estuarine area than those in riverine and marine areas and that particularly severe HM pollution was evidenced in the BS. The dominant elements in pollution hot spots varied greatly among the countries and regions. According to the geo-accumulation index (Igeo) and pollution load index (PLI) values, the sediments exhibited high Hg and Pb pollution in the BS; high As, Hg, and Pb pollution in the Yellow Sea of China; and high Cd and Hg pollution in the Yellow Sea of South Korea. In general, the sediments were moderately contaminated by HMs based on the high PLI (>1.0) and risk index (RI) values (>160). Ni and Cr in the sediment mainly originated from geogenic sources, while the other elements (Zn, As, Cd, Cu, Hg, and Pb) were primarily linked to anthropogenic sources. Based on the partial redundancy analysis, we found that environmental factors, especially OM, contributed significantly to the concentrations of HMs in both the sediments and water. The sediment HMs significantly contributed to the waterborne HMs due to their release from the sediments to the water column. An overall assessment of the contamination status, spatial distribution, and potential sources of HMs suggested that the water-sediment interaction of HMs and the influence by environmental factors should be subsequently considered for a better understanding of the multimedia fate of HMs in the given dynamic YSLME system or similar environments elsewhere. Keywords: Coastal ecosystem, Multimedia fate, Heavy metals, Ecological risk assessment, Influencing factors, Transnational survey

Reduced graphene oxide (rGO)-modified copper foil composite material was prepared by electrocoagulation of graphene oxide (GO) and a subsequent chemical reduction process. The effects of deposition voltages and the reduction time on the morphology, structure and electrochemical performances of the sample are investigated. The uniform surface morphology of GO/Cu sample obtained at a deposition voltage of 2.5 V. However, the appropriate chemical reduction not only improves the electrical conductivity of GO/Cu, but also enhances anticorrosion performance. At the optimized deposition voltages (2.5 V) and reduction time (20 min), the rGO/Cu shows the highest anticorrosive property and good conductivity. The protective efficiency of rGO/Cu is up to 98% (vs bare copper) as compared with 60% of GO/Cu according to Tafel analyses. The conductivity of rGO/Cu is close to bare copper according to the electrochemical impedance spectroscopy (EIS) results of Ni(OH)2/rGO/Cu and measurement of surface resistivity. We consider that rGO/Cu is a suitable material for realizing the copper foil manufacture with high corrosion resistance without sacrificing conductivity.

In this study, α-Ni(OH)2 with controllable pristine crystal size is directly electrodeposited on a substrate of Ti wire mesh to fabricate the integrated electrode. The nanoscale effects on morphology, microstructure and electrochemical performance of the cathodic deposited α-Ni(OH)2 are studied. The results show that the morphology of α-Ni(OH)2 varies from irregular honeycomb-like nanopieces, ball-shaped particles to oval nanoplates as the cathodic deposition current density increases. The nanostructure diversity of the cathodic deposited α-Ni(OH)2 is due to the different nanosize which directly depends on the cathodic deposition current density. The electrochemical performances of the cathodic deposited α-Ni(OH)2 increase with the decrease of the pristine crystal size of α-Ni(OH)2. The oval α-Ni(OH)2 nanoplates consisting of nanosheets with a pristine crystal size of 3 ∼ 5 nm × 5 ∼ 7 nm show the ultrahigh specific capacities of ∼348 mAh g−1 and ∼312.5 mAh g−1 at charge/discharge current density of 5 A g−1 and 100 A g−1, respectively, and over 70% specific capacity still remains after 1000 cycles, while the irregular honeycomb-like α-Ni(OH)2 consisting of nanosheet with a pristine crystal size of 10 ∼ 15 nm × 15 ∼ 20 nm shows only ∼260 mAh g−1 specific capacity at 5 A g−1 and ∼150 mAh g−1 at 100 A g−1. The ultrahigh electrochemical performances are attributed to the nanoscale and the defective nanostructure of the cathodic deposited α-Ni(OH)2.

Controlled synthesis of efficient core-shell non-precious metal catalysts for oxygen reduction reaction (ORR) is undoubtedly crucial but challenging for the extensive application of fuel cells and metal-air batteries. Herein, we prepared a core-shell structured Fe/FeCx nanoparticles and porous carbon composited catalyst (Fe/FeCx@NC) via a facile two-step heat treatment strategy. The Fe/FeCx@NC-800−0.5 prepared with secondary anneal at 800 °C for 0.5 h exhibits superior ORR performance to the commercial Pt/C in terms of comparable onset potential, higher half-wave potential, and outstanding long-term durability in alkaline media. Through combining the physical and electrochemical characterizations of Fe/FeCx@NC-T−t with different anneal temperature and precursors, the outstanding ORR performance of Fe/FeCx@NC-800−0.5 is caused by the synergistic effect between Fe/FeCx core and enriched pyridinic N- and graphitic N-doped carbon shell as well as porous carbon with large specific surface area. The structure-activity relationship of core-shell structured Fe–N–C catalysts for ORR provides directions for the development of advanced nonprecious metals catalysts.

Si/C materials are considered as the most promising anodes for the next generation lithium ion batteries. However, the Si/C anodes with high Coulombic efficiency are still a challenge. Here, pomegranate-like Si@C microspheres are successfully prepared with inexpensive AlSi alloy by surface modification, coating with resin, carbonization and acid etching processes. As high as 84.98% initial Coulombic efficiency (ICE) and 100% Coulombic efficiency are obtained for the sample (Si40@C3), and the specific capacity still maintained over 620 mAh g−1 with capacity retention of 70.4% over 250 cycles. The excellent electrochemical performance could be attributed to the distinctive pomegranate-like Si@C structure, which either stabilizes the porous structure of Si particle by inhibiting the volume expansion and pulverization or improves the electrochemical property by the appropriate carbon coating layer. This would provide a helpful guide to synthesize the Si/C anode with high ICE and Coulombic efficiency and stable cycling.

Electrolytic water splitting, consists of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), still has many challenges because of the high cost and scarity of the indispensable noble metal catalysts. Herein, the costless and effective NiFe layered double hydroxide (NiFe-LDH), supported on the Ti3C2Tx modified 3D nickel foam (NF), is used instead of noble metal to intensify the transfer ability of the charges as well as ions in the OER catalysis process. The prepared NiFe-LDH/Ti3C2Tx/NF electrode has a lower overpotential (240 ​mV ​at 50 ​mA ​cm−2) and Tafel slope (82 ​mV dec−1) as compared with that of IrO2/Ti3C2Tx/NF(400 ​mV, 252 ​mV dec−1). Meanwhile, it has a good endurance and stability with a negligible voltage changing after 15 ​h of testing. The work provides reference for the synthetic of catalyst with high catalytic kinetics and activity in the field of electrolytic water splitting.

Iron and nitrogen co-doped carbon (Fe-N/C) materials were fabricated by one-step pyrolysis of the mixture of FeCl3 and the low-cost biomass soybeans in N2 atmosphere at different temperatures. The physical properties of the prepared Fe-N/C catalysts were evaluated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) et al., the catalytic activity and stability of the Fe-N/C catalysts toward the oxygen reduction reaction (ORR) in alkaline solution were investigated by the electrochemical techniques. The results show that Fe is mainly in the form of Fe3O4 with the particle size of about 10 nm and encapsulated by thin graphite layers, and the content of Fe decreases from 1.19 to 0.24 wt.% with the increase of pyrolysis temperature from 600 to 900 °C. The ORR activity on the sample prepared at 700 °C (Fe-N/C-700) is preferable among the series of Fe-N/C catalysts, with the half-wave potential of the ORR shifting negatively only about 0.020 V as compared to that on the commercial Pt/C (40 wt.%, JM). The superior electro-catalytic performance of the Fe-N/C-700 catalyst would be due to the higher degree of the graphitization, the higher total contents of the pyridinic-N, quaternary-N/graphitic-N, as well as the relatively higher Fe3O4 content and surface area. The electron transfer number of the ORR on the Fe-N/C-700 catalyst approaches four indicating the 4-electron transfer pathway. Besides, the methanol tolerance and durability are superior to those on the Pt/C.

The concept of aqueous solution Al-ion battery inspires much enthusiasm in developing a novel chemical power source. In this work, the electrochemical behavior of TiO2-NTAs electrode in Al3+aqueous solution with different acidity is evaluated. Electrochemical studies showed that both of H+ and Al3+ in aqueous solution are electrochemical active to TiO2-NTAs, however, H+ is preferential to hydroxylate on the TiO2-NTAs surface rather than to intercalate in the TiO2-NTAs lattice as compared with Al3+under the assistance of Cl−. The surface hydroxylation of TiO2-NTAs can retard Al3+ diffusion in the TiO2-NTAs lattice as evidenced by the increase of faradic resistance RF (by EIS) at initial cathodic polarization process, however, the subsequent decrease of RF is due to the conductance improvement of TiO2-NTAs with the Al3+ intercalation. Here it can be concluded that for Al3+ aqueous solution battery with TiO2-NTAs as electrode, the suitable acidity (pH≈3) is required to minimizing the effect of H+.

In this work, we successfully synthesized Ni(OH)2 thin film electrode in situ doped with CNTs/rGO by cathodic electrodeposition on titanium mesh. The doping effects of CNTs and/or rGO, and the technical conditions, are investigated. The doping of CNTs/rGO can greatly improve the electrochemical performance by forming the porous structure and the conductive network in the Ni(OH)2 thin film. The highest capacity, 429.5 mAh/g at a current density of 5 A/g, is achieved for the electrode with 0.24 mg/cm2 Ni(OH)2 and codoped with CNTs and rGO, as compared with only 323.9 mAh/g for undoped electrode. Even at 100 A/g, the specific capacity can still remain 347.5 mAh/g (vs. 221.5 mAh/g for the undoped electrode), and after 1000 cycles, the retention rate of the specific capacity is 74.9% as compared with only 42.7% for the undoped electrode. Even with higher loading amounts of 1.92 mg/cm2 Ni(OH)2, the specific capacity retention rate of the codoped electrode is still much higher than that of the undoped electrode. The high electrochemical performance can be attributed to the better ion/electron transfer ability of the codoped electrode. In conclusion, by the cathodic electrodeposition and in situ doping of CNTs/rGO, the porous structure and the conductive network in Ni(OH)2 film can be constructed, which can improve the ion/electron transfer ability, therefore, the high performance film electrode with higher loading amount of Ni(OH)2 can be prepared.