Display omitted
•We report a cheaper yet higher efficient HER electrocatalyst than Pt.•The Ru@2D-NC is synthesized though a simple organic/aqueous interfacial strategy.•It exhibits low η@10 of 31 and ...29 mV in alkaline and acidic media respectively.•Optimized ΔG(H*) and ΔGB(H2O) are obtained via interatomic charge redistribution.•The strong Ru-support interaction endows the catalyst with excellent durability.
The development of efficient and durable electrocatalysts for hydrogen evolution reaction (HER) is crucial for sustainable electrochemical water splitting and its practical application. However, the inappropriate binding with H* and sluggish reaction kinetics limit their overall HER performance, especially in alkaline electrolyte. Herein, we report a robust and high active HER electrocatalyst with optimized metal-H* interaction and low water dissociation energy barrier through interatomic d-p orbital hybridization. The Ru nanoparticles with mean size down to 1.7 nm are anchored on two-dimension nitrogen-doped carbon nanocone arrays via a facile aqueous-organic interfacial method. This unique architecture induces strong interaction between Ru and the carbon support. Electrons are transferred from Ru to the N-doped carbon, causing a shift of charge distribution and modified surface properties of Ru. Furthermore, the newly emerged Ru-N bonds endow the catalyst with high structure robustness. As a result, the catalyst exhibits superior HER performances in both alkaline and acidic electrolytes, with low overpotentials (31 and 29 mV at 10 mA cm−2 respectively), high H2 turn over frequency (2.20 s−1 at the overpotential of 25 mV) and excellent durability (10,000 cycles). The density functional theory calculations reveal that the boosted HER activity can be attributed to the downshift of the d-band center of Ru, which lowers the |ΔG(H*)| and accelerates the H-OH cleavage.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Multiple reflection has been proven to be an effective method to enhance the gas detection sensitivity of Raman spectroscopy, while Raman gas probes based on the multiple reflection principle have ...been rarely reported on. In this paper, a multi-reflection, cavity enhanced Raman spectroscopy (CERS) probe was developed and used for in situ multi-component gas detection. Owing to signal transmission through optical fibers and the miniaturization of multi-reflection cavity, the CERS probe exhibited the advantages of in situ detection and higher detection sensitivity. Compared with the conventional, backscattering Raman layout, the CERS probe showed a better performance for the detection of weak signals with a relatively lower background. According to the 3σ criteria, the detection limits of this CERS probe for methane, hydrogen, carbon dioxide and water vapor are calculated to be 44.5 ppm, 192.9 ppm, 317.5 ppm and 0.67%, respectively. The results presented the development of this CERS probe as having great potential to provide a new method for industrial, multi-component online gas detection.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In this work, we report a (Ni50.1Ti34.9Hf15)85Nb15 alloy that shows excellent cold workability and good high-temperature shape memory effect. The as-cast sample shows eutectic microstructure ...consisting of β-Nb and the NiTiHf(Nb) matrix. The homogenized (Ni50.1Ti34.9Hf15)85Nb15 alloy shows high compressive fracture strain of 40% and excellent cold-rolling reduction ratio of 80%. It is suggested that the formation of (semi-) coherent β-Nb is the main reason on improving the ductility of NiTiHf alloy. After solution treatment, the material shows a high martensitic transformation start temperature of 146 °C, and a maximum shape memory effect strain of 2.3%. This work demonstrates that (Ni50.1Ti34.9Hf15)85Nb15 alloy with good cold workability and high-temperature shape memory effect may provide new opportunities for applications.
•Microstructure comprises (semi-) coherent β-Nb and NiTiHf(Nb) matrix is obtained.•Coherent β-Nb acts as nucleation and promotes martensitic transformation.•Compressive fracture strain 40% and cold-rolling reduction ratio 80% are obtained.•Martensitic transformation start temperature of 146 °C is obtained.•A maximum shape memory effect strain of 2.3% is achieved.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Chemical polishing is an effective method to remove a subsurface damage layer with the advantages of no mechanical stress and no new subsurface damage. In this paper, we report a target polishing ...method that employs an anhydrous organic acid-ionic liquid-in-oil (OA-IL/O) microemulsion as the etching solution for chemical polishing of KDP crystals. OA-IL/O microemulsions were prepared with 1-butyl-3-methyl imidazolium bis (trifluoromethyl) sulfonyl imide (BmimTF2N) and bis (trifluoromethane sulfonimide) (TF2NH) as the internal phase, castor oil as the external phase, TX-100 as the surfactant, and n-butanol as the co-surfactant. TF2NH irreversibly reacts with KDP when microemulsion micelles driven by Brownian motion collide with the KDP surface. The organic salt products are removed by the ionic liquid in the microemulsion, resulting in the effective elimination of KDP. Moreover, the organic acid-ionic liquid solution will preferentially diffuse to the high points of the KDP surface and react with the KDP to achieve the target polishing. As a new type of water-free surface polishing technology, OA-IL/O microemulsion not only has the advantages of traditional CMP, but also avoids the recrystallization that can occur with water-in-oil microemulsions and achieves target polishing of the KDP crystal.
Display omitted
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Fe–Mn damping alloy, which can decrease the vibrating and noise effectively, will be widely applied to household appliances, automobiles, industrial facilities, etc. In this paper, the internal ...friction mechanism of Fe–19Mn alloy at low strain amplitude (10−5 range) and high strain amplitude (10−4 range) was investigated. The internal friction was measured using multifunction internal friction equipment and reversal torsion pendulum. The microstructure was observed using scanning electron microscopy. The phase transformation temperatures were determined using differential scanning calorimetry. The results indicated that the internal friction of Fe–19Mn alloy after solution treating was related to strain amplitude. The internal friction mechanism was believed to the movements of four damping sources (ε-martensite variant boundaries, stacking fault boundaries in ε-martensite and γ-austenite, γ/ε interfaces), which could be explained using the interactive movements of Shockley partial dislocations and point defects. At low strain amplitude (10−5 range), the bowing out movements of Shockley partial dislocations are the main moving mode of generating internal friction. At high strain amplitude (10−4 range), however, the breaking away movements of Shockley partial dislocations are the high internal friction mechanism of Fe–19Mn alloy.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Ni47Ti44Nb9 alloys were successfully fabricated by laser powder bed fusion (LPBF) technique with different laser powers. The phase transformation behavior, tensile properties and shape memory ...response before and after heat treating were also investigated. The Ni47Ti44Nb9 LPBF alloys have good shaping properties, though a few defects were discovered. Phase transformation peaks did not appear in the as-built samples, but were observed in the heat-treated samples. The phase transformation temperatures of the heat-treated samples increase with the increase in laser power. The tension test at room temperature indicates that the LPBF samples exhibit poor tensile ductility, which may be related to the existence of pores and Ti2Ni or Ti4Ni2Ox phase during the LPBF process. However, the LPBF samples after heat treating still possess good shape memory effect (with recovery strain about 7.82–8%) and relatively high reverse transformation temperature (about 36–52.6 °C) when deformed to 8%.
To improve the shape memory effect (SME) of 304 austenitic steel effectively and efficiently, thermomechanical cycling, comprising deformation at room temperature and annealing, was applied. The ...influences of cycle number and annealing temperature on the SME and microstructures in 304 austenitic steel were investigated by light microscope (LM), X-ray diffraction (XRD), and transmission electron microscope (TEM). The shape recovery ratio was remarkably improved from 16% to 40% after two thermomechanical cycles. The optimum annealing temperature was 833 K in the process of thermomechanical cycling. The improved SME by thermomechanical cycling was mainly related to stress-induced ε martensite rather than stress-induced α’ martensite. The reason is that thermomechanical cycling can not only promote the occurrence of the stress-induced γ→ε martensitic transformation, but also suppress the subsequently stress-induced ε→α′ transformation.
To solve the problem of yield calculation in complex investment scenarios, a time-cost double-weighted rate of return calculation method based on SEA grid is proposed, and its effectiveness is ...verified by comparing with traditional methods and researching the quantitative evaluation and analysis method of user investment based on structured data. To solve the above problems, a data-heterogeneous federated learning method based on user investment analysis FedPSG is proposed, which changes the data form transmitted from the client to the server from model parameters to model scores, and only a small number of clients need to upload model parameters to the server in each round of training, thereby reducing communication costs. At the same time, a model retraining strategy is proposed, which uses server data to train the global model for second iteration, and further improves the model performance by alleviating the impact of data heterogeneity on federated learning. The method of event dimension analysis of user investment is designed, and a credibility index is proposed to evaluate the analysis results. Experiments show that by combining event data, it can effectively provide users with event factors in the fluctuation of investment profit and loss, and help users better analyze their own investments.
In the present work, three NiTiNb alloys with nominal compositions of Ni50–x/2Ti50–x/2Nbx (x = 18, 20 and 22, at.%) were prepared. The microstructure, thermal-induced phase transformation, and phase ...components of NiTiNb hypoeutectic, eutectic, and hypereutectic alloys were investigated by scanning electron microscopy coupled with energy dispersive spectrometer (SEM/EDS), differential scanning calorimetry (DSC), and X-ray diffraction (XRD), respectively. Two peaks occurred in the DSC curves of Ni41Ti41Nb18 solution at 750 and 850 °C. The different microstructures of NiTiNb hypoeutectic, eutectic and hypereutectic alloys, the occurrence of two peaks in the DSC curves, and the characteristic of martensite transformation temperature were analyzed and discussed. The results show that different Nb content leads to different microstructures of Ni50–x/2Ti50–x/2-Nbx alloys. Moreover, the difference of Ni/Ti ratio between the primary NiTi matrix and NiTi in eutectic structure strongly influenced the phase transformation behavior that the DSC curves of Ni41Ti41Nb18 alloy show two peaks. Furthermore, under the same solution treatment, the Ni40Ti40Nb20 alloy has a lower Ms than the other two alloys. The Ms has a tendency to decrease with an increase in solution temperature.
A high strength Al-5024 alloy containing Sc and Zr with a bi-modal microstructure consisting of fine equiaxed and coarse columnar grains was successfully fabricated by laser powder bed fusion (LPBF) ...additive manufacturing. The formation of the bi-modal microstructure was mainly due to both the formation of primary Al3Sc precipitates that act as nucleation sites and the steep temperature gradient during LPBF. By simulating the thermal field of a single melt pool, the formation mechanism of the bi-modal microstructure was explained. It was found by simulation that a solidification interface velocity less than 110 mm/s was beneficial to the nucleation of Al3Sc precipitates and, hence, facilitated the formation of a fine grain microstructure. Applying different heat treatments revealed a trade-off trend between yield strength and ductility as a function of the heat treatment time, and a correlation in fatigue life and yield strength was observed, both of which were closely related to the status of the secondary Al3Sc precipitates. The highest ultimate tensile strength of 450 MPa and corresponding 107 cycle fatigue strength of 105 MPa were achieved after hot isostatic pressing for 4 h at 325 °C with 100 MPa pressure. Dynamic strain aging was found to occur in both as-built and some heat treated samples, which was related to magnesium (Mg) solute atom clustering attributed to: (i) the formation of a diffuse “Mg wall” due to the repetitive melting and rapid cooling in LPBF, and (ii) the growth of intragranular (Al3Sc) and intergranular precipitates (Fe-, Mn-rich) during subsequent heat treatment, thereby leading to an increasing number of misfit dislocations that promote the formation of Mg atom clusters.
Display omitted
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
PDF
