The efficient precision machining of tungsten carbide has always been a challenge for many reasons, one of which is the lacking of fundamental investigations on the dynamic mechanical properties of ...WC-Co. In this article, five different types of tungsten carbides (WC-8Co, WC-12Co, WC-15Co, WC-15CoX, and WC-20CoC) were tested by the split Hopkinson pressure bar (SHPB) test, and the Johnson-Cook (JC) model parameters were obtained using least squares fitting as well as the influence of cobalt content and grain size on JC model parameters were investigated. The JC model parameters were verified to be accurate by comparing the cutting force and chip morphology of cutting simulation with DEFORM V11.0 software and of orthogonal cutting tests. The maximum deviation between experimental and simulated cutting forces in the tangential and normal directions were 15.4 % and 10.8 %, respectively. Both the simulation and experimental cutting chips were serrated, with segmentation degrees of 55.89 % and 50.31 %, respectively.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Electro‐reforming of Polyethylene‐terephthalate‐derived (PET‐derived) ethylene glycol (EG) into fine chemicals and H2 is an ideal solution to address severe plastic pollution. Here, we report the ...electrooxidation of EG to glycolic acid (GA) with a high Faraday efficiency and selectivity (>85 %) even at an industry‐level current density (600 mA cm−2 at 1.15 V vs. RHE) over a Pd−Ni(OH)2 catalyst. Notably, stable electrolysis over 200 h can be achieved, outperforming all available Pd‐based catalysts. Combined experimental and theoretical results reveal that 1) the OH* generation promoted by Ni(OH)2 plays a critical role in facilitating EG‐to‐GA oxidation and removing poisonous carbonyl species, thereby achieving high activity and stability; 2) Pd with a downshifted d‐band center and the oxophilic Ni can synergistically facilitate the rapid desorption and transfer of GA from the active Pd sites to the inactive Ni sites, avoiding over‐oxidation and thus achieving high selectivity.
Concerted and selective electro‐reforming of PET‐derived ethylene glycol into high‐value glycolic acid and H2 fuel was achieved at an industry‐level current density (600 mA cm−2 at 1.15 V vs. RHE) by a Pd−Ni(OH)2 catalyst. Notably, stable electrolysis over 200 h can be achieved in a flow electrolyzer, outperforming all available Pd‐based catalysts.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Let M be a compact orientable irreducible 3-manifold, and F be an essential connected closed surface in M which cuts M into two manifolds M1 and M2. If Mi has a minimal Heegaard splitting Mi = Vi∪Hi ...Wi with d（H1） ＋ d（H2） ≥ 2（g（M0 ＋ g（M2） - g（F）） ＋ 1, then g（M） = g（M1） ＋ g（M2） - g（F）.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We report the synthesis of two‐dimensional metal–organic frameworks (MOFs) on nickel foam (NF) by assembling nickel chloride hexahydrate and 1,1′‐ferrocenedicarboxylic acid (NiFc‐MOF/NF). The ...NiFc‐MOF/NF exhibits superior oxygen evolution reaction (OER) performance with an overpotential of 195 mV and 241 mV at 10 and 100 mA cm−2, respectively under alkaline conditions. Electrochemical results demonstrate that the superb OER performance originates from the ferrocene units that serve as efficient electron transfer intermediates. Density functional theory calculations reveal that the ferrocene units within the MOF crystalline structure enhance the overall electron transfer capacity, thereby leading to a theoretical overpotential of 0.52 eV, which is lower than that (0.81 eV) of the state‐of‐the‐art NiFe double hydroxides.
2D MOFs on nickel foam (NF) were assembled. NiFc‐MOF/NF exhibits superior OER performance (overpotential of 195 mV at 10 and 241 mV at 100 mA cm−2) under alkaline conditions. The ferrocene units within the MOF crystalline structure enhance the overall electron transfer capacity, thereby leading to a theoretical overpotential of 0.52 eV (lower than NiFe double hydroxides: 0.81 eV).
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Perfluorooctanoic acid (PFOA) and its substitute GenX are toxic chemicals that are widespread in the aquatic environment. However, there is little information about their toxicity mechanisms to ...aquatic organisms. In this study, Chlorella pyrenoidosa (C. pyrenoidosa) was treated with two concentrations (100 ng L−1 and 100 μg L−1) of PFOA or GenX for 12 days. The results showed that these two concentrations of PFOA and GenX began to inhibit the growth of algae after 6 days of treatment, and the Chlorophyll content and photosynthetic activity of C. pyrenoidosa were also negatively affected by these two chemicals. The transcriptomic results indicated that most of the genes related to the photosynthetic metabolism of C. pyrenoidosa were down-regulated (in 100 ng L−1 treatment groups) on the 12th day. Besides, GenX and PFOA showed similar effects on algae photosynthesis including physical damage and metabolic disorders. According to this study, GenX might not be an ideal substitute for PFOA, and more attention should be paid on the management of emerging perfluoroalkyl substances.
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•PFOA and its substitute GenX have effect on photosynthesis of C. pyrenoidosa.•Transcription analysis showed that they down-regulated the photosynthetic genes.•Both of them have similar toxicity and effect mechanisms on C. pyrenoidosa.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The recycling of plastic waste is one of the most urgent issues in the 21st century owing to its detrimental impact on the environment and human health. However, it is greatly challenging to develop ...more efficient, low-cost and general methods capable of selectively converting plastic waste into added-value and separable chemicals while restricting their distribution. Here, we report a general electrocatalytic strategy for the selective upcycling of various polyester plastics into added-value chemicals by a CuCo2O4/Ni foam catalyst under mild conditions. In particular, polyethylene terephthalate (PET) was upcycled into terephthalate and formate with high efficiency and selectivity (>86%) even at a high current density of 100 mA cm−2. The electrocatalytic reaction mechanism was thoroughly elucidated by electrochemical in situ FTIR, NMR and DFT calculations. This work not only develops a superior electrocatalyst for upcycling various polyester plastics, but also provides guidance for the design of new and efficient electrocatalysts.
Transition-metal carbides (TMCs) are important materials for a variety of applications and industrial processes, in part because of their variable crystal structures and surfaces. However, the ...synthesis of TMCs often proceeds through metastable phases during particle growth, the appearance of which cannot be described by traditional phase diagrams. Here, we use density functional theory calculations and thermodynamic analyses to construct particle size-dependent phase diagrams for Mo and W carbides and reveal the relationships between phase stability and TMC nanoparticle size. We compute size-dependent phase diagrams for a wide range of Mo carbide and W carbide phases, determine predicted crystallization pathways during synthesis, and compare model results with experimental data. We provide insights for the influence of nanoparticle size on TMC nucleation and growth during synthesis and provide a computationally guided road map for navigating the synthesis of target TMC surfaces and phases.
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IJS, KILJ, NUK, PNG, UL, UM
Tungsten carbide is known as an essential material for manufacturing industrial molds and tools owing to its excellent mechanical properties. However, the high-efficiency finishing of tungsten ...carbide is yet a challenge for it is extremely difficult to cut. This study investigates the influence of feed per tooth, radial cutting depth, and cutting speed on the wear of the PCD tool and the surface quality in dry milling of WC-15Co tungsten carbide. Experimental results showed that the PCD tool presented the longest tool life when the feed per tooth and radial cutting depth were below 9 µm/z and 0.6 mm, respectively, with the milling speed controlled at around 300 m/min. The flank wear-width
VB
was within 20 µm, and the surface roughness
S
a
was below 1.5 µm after 360 mm
3
of the workpiece was removed. The effect of cutting parameters on the tool wear and surface roughness follows the order: feed per tooth > radial cutting depth > milling speed. The main forms of tool wear were found to be diffusion wear, wear caused by hard particles (two-body wear and three-body wear), and obvious adhered layer due to Co binder adhering and stacking on the tool rake face. Micro-chipping on the tool edge is considered one of the major causes of the increase in surface roughness. The defects on the machined surface largely originated from the clustering and spalling of WC particles, and the grooves formed by hard cluster rolling and plowing during WC-15Co milling.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Electrocatalytic nitrate reduction reaction (NO3RR) is a promising approach for converting nitrate into environmentally benign or even value‐added products such as ammonia (NH3) using renewable ...electricity. However, the poor understanding of the catalytic mechanism on metal‐based surface catalysts hinders the development of high‐performance NO3RR catalysts. In this study, the NO3RR mechanism of single‐atom catalysts (SACs) is systematically explored by constructing single transition metal atoms supported on MXene with oxygen vacancies (Ov‐MXene) using density functional theory (DFT) calculations. The results indicate that Ag/Ov‐MXene (for precious metal) and Cu/Ov‐MXene (for non‐precious metal) are highly efficient SACs for NO3RR toward NH3, with low limiting potentials of −0.24 and −0.34 V, respectively. Furthermore, these catalysts show excellent selectivity toward ammonia due to the high energy barriers associated to the formation of byproducts such as NO2, NO, N2O, and N2 on Ag/Ov‐MXene and Cu/Ov‐MXene, effectively suppressing the competitive hydrogen evolution reaction (HER). The findings not only offer new strategies for promoting NH3 production by MXene‐based SACs electrocatalysts under ambient conditions but also provide insights for the development of next‐generation NO3RR electrocatalysts.
Single‐atom catalysts (SACs) consisting of 3d, 4d, and 5d transition metals on defective MXenes with oxygen vacancies (Ov) are explored computationally for their NO3− reduction performance with Ag and Cu found to be exceptionally active and selective for NH3 production, thereby revealing the underlying descriptors for efficient nitrate‐to‐ammonia upcycling.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The purpose of this study was to investigate the influence of substrates (quartz sand and coke) on the removal of pollutants (COD, NH4+-N and TP), electrochemical characteristics and microbial ...communities of vertical flow constructed wetlands (VFCW) under high pollutant loads. During operation, the removal rates of COD, NH4+-N and TP by VFCW-C (coke as substrate) were higher than that of VFCW-Q (quartz sand as substrate) by 9.73–19.41%, 5.03%–13.15% and 8.83%–14.58%, respectively. And the resistances of the VFCW-Q and VFCW-C were increased by 1228.9 Ω and 38.3 Ω, while their potentials were dropped from 182.4 mV to 377.9 mV–85.6 mV and 222.0 mV, respectively. The dominant bacteria at the bottoms of VFCW-Q and VFCW-C were individually aerobic denitrifying bacteria (ADNB; 14.98%)/ammonia oxidizing bacteria (AOB; 5.73%) and organics aerobic degrading bacteria (OADB; 12.48%)/ammonia oxidizing bacteria (AOB; 7.24%), while the predominant bacteria at their tops were separately ADNB (11.36%)/OADB (10.52%)/AOB (4.69%) and ADNB (15.09%)/AOB (8.86%) and OADB (3.20%) The removal of pollutants by VFCW-Q and VFCW-C may be mainly attributed to substrate adsorption and microbial degradation.
•The removals of VFCW-C on COD, NH4+-N and TP were better than that of VFCW-Q.•The resistance rise of VFCW-Q and the potential drop of VFCW-C were greater.•The dominant bacteria of VFCW-Q and VFCW-C were very different.•The pollutants removal depended on substrate adsorption and microbial degradation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
