B4c/c(graphite) composites were produced using Hot-pressing. However, the composites exhibited low surface hardness, low wear resistance as well as low oxidation resistance. The hot-pressed B4c/c(graphite) composites ...
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B4c/c(graphite) composites were produced using Hot-pressing. However, the composites exhibited low surface hardness, low wear resistance as well as low oxidation resistance. The hot-pressed B4c/c(graphite) composites were processed via silicon infiltration procedure at 1550 degrees c for 2 h in the vacuum condition to refine the wear resistance, surface hardness, and oxidation resistance of the B4c/c(graphite) composites. The silicon infiltration process resulted in the fabrication of a surface layer based on silicon carbide and silicon upon the B4c/c (graphite) composites surface. The surface layer of the silicon infiltrated B4c/c(graphite) composites, primarily comprising silicon carbide and silicon, was examined for its phase composition and microstructure. The oxidation resistance, wear resistance, and surface hardness of B4c/c(graphite) composites subjected to silicon infiltration was additionally examined. The XRD results confirmed that silicon carbide and silicon-based layer existed on the surface of B4c/c(graphite) composites, which was produced as a result of the silicon infiltration process. The surface of silicon infiltrated B4c/c(graphite) composites exhibited a 300-400 mu m thick covering of silicon carbide and silicon. The deposited layer also exhibited a dense and compact microstructure. When compared to hot-pressed B4c/c(graphite) composites, the surface hardness and wear resistance of the composites resulting after silicon infiltration were significantly enhanced. Silicon infiltrated B4c/c(graphite) composites possess a surface hardness of 16-17 GPa. The oxidation resistance of the silicon infiltrated B4c/c(graphite) composites was considerably enhanced as compared to the hot-pressed B4c/c(graphite) composites. So the silicon infiltrated B4c/c(graphite) composites exhibited high surface hardness, excellent wear resistance and excellent oxidation resistance in comparison with the hot-pressed B4c/c(graphite) composites.
Every day, a large amount of food waste (FW) is generated that causes serious environmental problems such as the production of greenhouse gases and leachate. A possible treatment for this waste is anaerobic digestion ...
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Every day, a large amount of food waste (FW) is generated that causes serious environmental problems such as the production of greenhouse gases and leachate. A possible treatment for this waste is anaerobic digestion (AD), but there are several problems associated with the accumulation of volatile fatty acids (VFA), foaming, or low buffer capacity. In order to resolve or mitigate this problem, FW was mixed with cabbage and cauliflower (ccF) leaves and stalks at different carbon/nitrogen ratios (c/N) to add value to this agricultural waste and benefit from the advantages of co-digestion. Under the study conditions, promising results were obtained during the co-digestion of FW and agricultural wastes at c/N = 45. These include a high biodegradability (98%), a methane yield of 475 mL(STP) cH4/g VS, and an organic loading rate (OLR) of 0.06 kg of VS/m(3) h for the ccF and FW mixture (ccF + FW). Anaerobicco-digestion of ccF + FW might be an interesting option for the simultaneous treatment of these types of organic waste, with the consequent social and environmental benefits.
The carbon layer acting as a conductive medium is beneficial to overcoming the comparatively inferior electronicconductivity of Na3V2(PO4)(3). Based on this, Na3V2(PO4)(3)/ccomposites with diverse ratios of citric a...
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The carbon layer acting as a conductive medium is beneficial to overcoming the comparatively inferior electronicconductivity of Na3V2(PO4)(3). Based on this, Na3V2(PO4)(3)/ccomposites with diverse ratios of citric acid are synthetized via rheological phase reaction way in this work. The consequences display that the Na3V2(PO4)(3)/c-1.5 composite brings a higher initial discharge capacity of 113.2 mAh g(-1) at a current rate of 1 c with coulombic efficiency above 99% during all cycles. The discharge capacity retains at 117.6 mAh g(-1) at the 100th cycle. Even at the high current densities of 5 c and 10 c, the composite also shows superior cycling performance with negligible capacity fading. Its discharge capacities decline from 97 to 92.6 mAh g(-1) at 5 c and from 85.3 to 83.7 mAh g(-1) at 10 c. These remarkable outcomes arise from its preferable morphology with suitable carbon coating because both excess and skimpy carbon seriously affect the microstructure and electrochemical properties of Na3V2(PO4)(3)/ccomposites.
Manganese oxide (MnO) is prospective as anode material for lithium-ion batteries (LIBs) due to its low insertion voltage and high reversible capacity. Here, urchin-like MnO microspheres with carbon coating (u-MnO/c) a...
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Manganese oxide (MnO) is prospective as anode material for lithium-ion batteries (LIBs) due to its low insertion voltage and high reversible capacity. Here, urchin-like MnO microspheres with carbon coating (u-MnO/c) are synthesized through hydrothermal method, and its lithium storage performance is investigated. The unique urchin-like structures of u-MnO/c endow it high surface area which provides sufficient contact with electrolyte. The carbon coating can effectively suffer volume change of u-MnO during charge/discharge process. Meanwhile, the carbon coating can effectively improve the conductivity of u-MnO-based anode. Due to the above features, u-MnO/c delivers high initial capacity of 845 mAh g(-1), and an obvious activation process is observed at the beginning of the cycles thanks to the abundant invasion of the electrolyte into u-MnO/c. The large capacity of 723 mAh g(-1) can still be achieved after 80 cycles. This work provides a promising guide for designing high-performance LIBs electrode materials.
As major waste materials in the rice milling industry, rice husks (RHs) have potential industrial applications. In this work, acid solutions were used to extract high-value-added polysaccharide components (hemicellulo...
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As major waste materials in the rice milling industry, rice husks (RHs) have potential industrial applications. In this work, acid solutions were used to extract high-value-added polysaccharide components (hemicellulose and cellulose) from RHs to obtain sugar residues (SRs) for comprehensive utilization. The SRs were converted into c/SiO2 composites after carbonization and ball-milling. The c/SiO2 composites with crystalline cellulose content in the precursor possessed desirable electrochemical properties when tested as an anode material for lithium-ion batteries (LIBs), including cycle performance, initial coulombic efficiency (IcE) and electrical impedance. Meanwhile, a high reversible specificcapacity of 553 mAh g(-1) was maintained after 100 cycles at a current density of 0.1 A g(-1). This method can be used to turn biomass into a potentially valuable anode material with desirable electrochemical properties for LIBs.
Developing high-efficiency and low-cost electrocatalysts for oxygen reduction reaction (ORR) is one of the key objectives for fuel cells. In this work, S-modified co3O4@S-g-c3N4/ccatalyst was prepared by combining py...
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Developing high-efficiency and low-cost electrocatalysts for oxygen reduction reaction (ORR) is one of the key objectives for fuel cells. In this work, S-modified co3O4@S-g-c3N4/ccatalyst was prepared by combining pyrolysis with ultrasonic method. Transmission electron microscopy analysis indicated that the obtained catalyst had a core-shell structure, which used co3O4 as its core and 1.5-nm-thick S-interspersed g-c3N4 encapsulated co3O4 as shell. When the ratio of S to g-c3N4 was 1:3, the as-prepared catalyst co3O4@ S-g-c3N4/c exhibited positive onset potential and higher limiting diffusion current density of 4.00 mA cm(-2) @0.8V, which was 10 and 37% higher than that of co3O4@g-c3N4/c and co3O4/c, respectively. After 2000 cV cycles, the catalyst also showed good durability.
This paper discusses different aspects of an active flexible filament propulsion in a liquid medium. The immersed boundary method is used to model a flexible filament immersed in Newtonian fluid at low Reynolds number...
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This paper discusses different aspects of an active flexible filament propulsion in a liquid medium. The immersed boundary method is used to model a flexible filament immersed in Newtonian fluid at low Reynolds numbers. The flexible filament motion emulates that of a c. elegans. We varied some parameters of the filament motion, such as the interpolation points of the function related to the curvature of the filament and the upstroke and downstroke period, and analyzed the kinematic response in the body displacement and fluid flow. A methodology based on signal analysis is proposed for correct modeling of the movement of these filaments. The swimming velocity and distance are analyzed using wavelet transform, in which the notion of time-frequency localization is made precise. This methodology allows defining which parameters lead to the best efficiency, e.g., greater swim distance for the same number of strokes, making it very valuable for passive control of the filament.
Three Mo-Ti-Si-B alloys with compositions of 50Mo-20Ti-20Si-10B, 40Mo-30Ti-20Si-10B and 30Mo-40Ti-20Si-10B (at.%) were designed and prepared by arc-melting. Microstructure evolution at 1600 degrees c and oxidation mec...
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Three Mo-Ti-Si-B alloys with compositions of 50Mo-20Ti-20Si-10B, 40Mo-30Ti-20Si-10B and 30Mo-40Ti-20Si-10B (at.%) were designed and prepared by arc-melting. Microstructure evolution at 1600 degrees c and oxidation mechanism at 800 degrees c of these alloys were analyzed. 50Mo-20Ti-20Si-10B suffered from pesting because of a large volume fraction of Mo3Si, which produced porous products with severe volume expansion. Both 40Mo-30Ti-20Si-10B and 30Mo-40Ti-20Si-10B have better oxidation resistance. It can be inferred that during long-term oxidation, interactions between constituent phases contributed to the overall oxidation resistance of the alloys.
In this study, the degradation performance of nutrients in zeolite trickling filter (ZTF) with different influent c/N ratios and aeration conditions was investigated. Microaeration was beneficial for enhancing NH4+-N ...
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In this study, the degradation performance of nutrients in zeolite trickling filter (ZTF) with different influent c/N ratios and aeration conditions was investigated. Microaeration was beneficial for enhancing NH4+-N removal performance. Due to the sufficient carbon source supply under a c/N ratio of 8, a high removal efficiency of NH4+-N and TN was simultaneously observed in ZTF. In addition, TN removal mainly occurred at the bottom, which might be explained by the sufficient nutrients available for bacteria to multiply in this zone. The abundant genera were Acinetobacter, Gemmobacter, Flavobacterium, and Pseudomonas, all of which are heterotrophic nitrification-aerobic denitrification (HNAD) bacteria. In addition, biofilm only slowed down the adsorption rate but did not significantly reduce the adsorption capacity of zeolite. Bio-zeolite had NH4+-N well adsorption capacity and bio-desorption capacity. Biological nitrogen removal performance was superior to physicochemical absorption of zeolite. The results suggested that the physicochemical of zeolite and biochemical reactions of microorganism coupling actions may be the main nitrogen transformation pathway in ZTF. Our research provides a reference for further understanding the nitrogen removal mechanism of zeolite bioreactors.
Exponential growth in the field of covalent-organic frameworks (cOFs) is emanating from the direct correlation between designing principles and desired properties. The comparison of catalytic activity between single-p...
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Exponential growth in the field of covalent-organic frameworks (cOFs) is emanating from the direct correlation between designing principles and desired properties. The comparison of catalytic activity between single-pore and dual-pore cOFs is of importance to establish structure-function relationship. Herein, the synthesis of imine-linked dual-pore [(BPyDc)](x)(%)-ETTA cOFs (x = 0%, 25%, 50%, 75%, 100%) with controllable bipyridine content is fulfilled by three-component condensation of 4,4 ',4 '',4 '''-(ethene-1,1,2,2-tetrayl)tetraaniline (ETTA), 4,4 '-biphenyldialdehyde, and 2,2 '-bipyridyl-5,5 '-dialdehyde in different stoichiometric ratio. The strong coordination of bipyridine moieties of [(BPyDc)](x)(%)-ETTA cOFs with palladium imparts efficient catalytic active sites for selective functionalization of sp(2)c-H bond to c-X (X = Br, cl) or c-O bonds in good yield. To broaden the scope of regioselective c-H functionalization, a wide range of electronically and sterically substituted substrates under optimized catalyticcondition are investigated. A comparison of the catalytic activity of palladium decorated dual-pore frameworks with single-pore imine-linked Pd(II) @ Py-2,2 '-BPyDc framework is undertaken. The finding of this work provides a sporadic example of chelation-assisted c-H functionalization and disclosed an in-depth comparison of the relationship between superior catalytic activity and core properties of rationally designed imine linked frameworks.
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