Surface Plasmon Polaritons of Two-Dimensional Three-Order Dendritic Structures

We study surface plasmon polaritons excited on two-dimensional three-order dendritic structures. Previous studies show that split ring resonators （SRRs） can be used to obtain magnetic resonance, thus sustairdng surface waves behaving like surface plasmon polaritons （SPPs）. In this paper, we obtain detailed results on surface plasmon polaritons of several different grating structures and theoretically prove that this kind of structures can sustain SPPs. Besides, since dendritic structures can be fabricated by double template-assisted electrochemical deposition, it is worth noting that fabrication of SPP-based materials might be much easier.

INFLUENCE OF ELECTROMAGNETIC STIRRING ON DENDRITIC STRUCTURE AND MECHANICAL PROPERTIES OF LOW SULPHUR STEEL

The melt flow induced by the electromagnetic stirring in the molten low sulphur steel may re- fine the original austenite grains,but widen the secondary denritic arm spacings.As a result, the ultimate tensile strength of the steel will be improved and the reduction of area will be re- markably decreased.The microalloying by an addition of Ce may retard the unfavourable ef- fect of the electromagnetic stirring.

A dendritic Cu/Cu_(2)O structure with high curvature enables rapid and efficient reduction of carbon dioxide to C_(2) in an H-cell

Electrocatalytic reduction of CO_(2)(CO_(2)RR)to multicarbon products is an efficient approach for ad-dressing the energy crisis and achieving carbon neutrality.In H-cells,achieving high-current C_(2)products is challenging because of the inefficient mass transfer of the catalyst and the presence of the hydrogen evolution reaction(HER).In this study,dendritic Cu/Cu_(2)O with abundant Cu^(0)/Cu^(+)interfaces and numerous dendritic curves was synthesized in a CO_(2)atmosphere,resulting in the high selectivity and current density of the C_(2)products.Dendritic Cu/Cu_(2)O achieved a C_(2)Faradaic efficiency of 69.8%and a C_(2)partial current density of 129.5 mA cm^(-2)in an H-cell.Finite element simulations showed that a dendritic structure with a high curvature generates a strong electric field,leading to a localized CO_(2)concentration.Additionally,DRT analysis showed that a dendritic struc-ture with a high curvature actively adsorbed the surrounding high concentration of CO_(2),enhancing the mass transfer rate and achieving a high current density.During the experiment,the impact of the electronic structure on the performance of the catalyst was investigated by varying the atomic ratio of Cu^(0)/Cu^(+) on the catalyst surface,which resulted in improved ethylene selectivity.Under the optimal atomic ratio of Cu^(0)/Cu^(+),the charge transfer resistance was minimized,and the desorption rate of the intermediates was low,favoring C_(2) generation.Density functional theory calculations indicated that the Cu^(0)/Cu^(+) interfaces exhibited a lower Gibbs free energy for the rate-determining step,enhancing C_(2)H_(4) formation.The Cu/Cu_(2)O catalyst also exhibited a low Cu d-band center,which enhanced the adsorption stability of *CO on the surface and facilitated C_(2)formation.This observa-tion explained the higher yield of C_(2) products at the Cu^(0)/Cu^(+) interface than that of H_(2) under rapid mass transfer.The results of the net present value model showed that the H-cell holds promising industrial prospects,contingent upon it being a catalyst with both high selectivity and high current density.This approach of integrating the structure and composition provides new insights for ad-vancing the CO_(2)RR towards high-current C_(2) products.

Facile Synthesis of Micro/Nano Binary Dendritic Gold Structures for SERS and Superhydrophobic Applications

Via a galvanic displacement reaction, well-defined micro/nano binary dendritic gold structures were prepared on silicon wafers in fluoride acid solution containing HAuCI4 at 50 ℃. The gold deposits were characterized with scanning electron microscopy （SEM）, energy-dispersive X-ray （EDX） spectrum and X-ray diffraction （XRD）. The investigation of the surface-enhanced Raman scattering （SERS） reveals that the film of gold dendrites was an excellent substrate with significant enhancement effect. Also, the gold dendritic structured surface exhibited a remarkable superhydrophobic property with a contact angle of approximately 165° and low contact angle hysteresis after further simple surface modification with n-dodecanethiol.

Dendritic tip selection during solidification of alloys:Insights from phase-field simulations

The effect of undercooling DT and the interface energy anisotropy parameter e4 on the shape of the equiaxed dendritic tip has been investigated by using a quantitative phase-field model for solidification of binary alloys.It was found that the tip radius r increases and the tip shape amplitude coefficient A4 decreases with the increase of the fitting range for all cases.The dendrite tip shape selection parameter sdecreases and then stabilizes with the increase of the fitting range,and sincreases with the increase of e4.The relationship between sand e4 follows a power-law function sµea 4,and a is independent of DT but dependent on the fitting range.Numerical results demonstrate that the predicted sis consistent with the curve of microscopic solvability theory(MST)for e4<0.02,and sobtained from our phase-field simulations is sensitive to the undercooling when e4 is fixed.

Eutectic reaction and cored dendritic morphology in yttrium doped Zr-based amorphous alloys

The microalloying effect of yttrium on the crystallization behaviors of （Zr0.525Al0.10Ti0.05Cu0.179Ni0.146）100-xYx, and （Zr0.55Al0.15- Ni0.10Cu0.20）100-xYx （x=0, 0.4, and 1, thus the two alloy systems were denoted as Zr52.5, Zr52.5Y0.4, Zr52.5Y1, and Zr55, Zr55Y0.4, Zr55Y1, respectively） was studied. Transmission electron microscopy （TEM） results suggested that the crystalline phases were different in the two Zr-based alloys and with different yttrium contents. ZrNi-phase and Al3Zr5 phase precipitations can be well explained by the mechanisms of nucleation and growth. Al3Zr5 phase is mainly formed by a peritectic-like reaction, while ZrNi-phase by a eutectic reaction. The contents of elements Y, A1, and Ti may dominate the reaction types. The orientation relationship between Y203 particles and A13Zr5 phase is also discussed.

Highly soluble dendritic fullerene derivatives as electron transport material for perovskite solar cells

A series of shape-persistent polyphenylene dendritic C_(60)derivatives as the electron transport materials were designed and synthesized via a catalyst-free Diels-Alder[4+2]cycloaddition reaction.These increasing hyperbranched scaffolds could effectively enhance the solubility;notably,both first and second generation dendrimers,C_(60)-G1 and C_(60)-G2,demonstrated more than 5 times higher solubilities than pristine C_(60).Furthermore,both simulated and experimental data proved their promising solution-processabilities as electron-transporting layers(ETLs)for perovskite solar cells.As a result,the planar p-i-n structural perovskite solar cell could achieve a maximum power conversion efficiency of 14.7%with C_(60)-G2.

Model of Primary Austenite Dendrite Structure in Hypoeutectic Cast Iron

The solidification of primary austenite in hypocutcctic gray cast iron was studied by stepped grinding and quantitative metallography.The dendrite structure of primary austenite can be described by three models:typical dendrite crystal model,metamorphic dendrite crystal model and network dendrite crystal model.The dendrite crystals formed according to 3rd model is much more than those formed according to other models in this experiment.The primary austenites are connected each other,and the primary stems of austenite could be regarded as secondary arms and vice versa.

Hippocampal insulin resistance and the Sirtuin 1 signaling pathway in diabetes-induced cognitive dysfunction

In the peripheral nervous system,the activation of Sirtuin 1 can improve insulin resistance;however,the role played by Sirtuin 1 in the central nervous system remains unknown.In this study,rat models of diabetes mellitus were generated by a single injection of streptozotocin.At 8 weeks after streptozotocin injection,the Morris water maze test and western blot assays confirmed that the diabetic model rats had learning and memory deficits,insulin resistance,and Sirtuin 1 expression could be detected in the hippocampus.Insulin and the insulin receptor inhibitor S961 were intranasally administered to investigate the regulatory effects of insulin signaling on Sirtuin 1.The results showed that insulin administration improved the impaired cognitive function of diabetic model rats and increased the expression levels of phosphorylated insulin receptor,phosphorylated insulin receptor substrate 1,and Sirtuin 1 in the hippocampus.Conversely,S961 administration resulted in more severe cognitive dysfunction and reduced the expression levels of phosphorylated insulin receptor,phosphorylated insulin receptor substrate 1,and Sirtuin 1.The Sirtuin 1 activator SRT2104 and the inhibitor Sirtinol were injected into the lateral ventricle,which revealed that the activation of Sirtuin 1 increased the expression levels of target of rapamycin complex 1,phosphorylated cAMP-response elementbinding protein,and brain-derived neurotrophic factor.Hippocampal dendritic length and spine density also increased in response to Sirtuin 1 activation.In contrast,Sirtinol decreased the expression levels of target of rapamycin complex 1,phosphorylated cAMP-response elementbinding protein,and brain-derived neurotrophic factor and damaged the dendritic structure.These findings suggest that the Sirtuin 1 signaling pathway plays an important role in the development of insulin resistance-related cognitive deficits in diabetic rats.This study was approved by the Animal Ethics Welfare Committee of the First Affiliated Hospital of Hunan University of Chinese Medicine(approval No.ZYFY201811207)in November 2018.

Lightweight broadband microwave absorbing metamaterial with CB-ABS composites fabricated by 3D printing

The self-similarity,high geometric symmetry and spatial utilization properties of fractal structures provide new methods for the development of absorbing metamaterials.In this paper,the microwave absorption properties of the gradient dendritic fractal metamaterial structure(GDFMs)based on carbon black and acrylonitrile-butadiene-styrene composites were investigated.The optimal metamaterial structure has an effective absorption in the frequency range of 4.5-40 GHz.The rotational-symmetry GDFMs leads to the polarization independence,and the GDFMs exhibits a wide-angle absorption performance for both TE and TM waves.It is expected that the proposed GDFMs has good application prospects in electromagnetic wave absorption.

Prediction of mechanical properties of Al alloys with change of cooling rate

The solidification process significantly affects the mechanical properties and there are lots of factors that affect the solidification process.Much progress has been made in the research on the effect of solidification on mechanical properties.Among them,the PF(Phase Field) model and CA(Cellular Automata) model are widely used as simulation methods which can predict nucleation and its growth,and the size and morphology of the grains during solidification.Although they can give accurate calculation results,it needs too much computational memory and calculation time.So it is difficult to apply the simulation to the real production process.In this study,a more practical simulation approach which can predict the mechanical properties of real aluminum alloys is proposed,by identifying through experiment the relationship between cooling rate and SDAS(Secondary Dendrite Arm Spacing) and mechanical properties.The experimentally measured values and the values predicted by simulation have relatively small differences and the mechanical properties of a variety of Al alloys are expected to be predicted before casting through use of the simulation.

Effect of Carbon on Grain Boundary Segregation of Phosphorus and Phosphorus-Induced Intergranular Fracture in High Purity Iron with Phosphorus

The solidification of primary austenite in hypoeutectic gray cast iron was studied by stepped grinding and quantitative metallography. The dendrite structure of primary austenite can be described by three models: typical dendrite crystal model, metamorphic dendrite crystal model and network dendrite crystal model. The dendrite crystals formed according to 3rd model is much more than those formed according to other models in this experiment. The primary austenites are connected each other, and the primary stems of austenite could be regarded as secondary arms and vice versa.

Inconsistent creep between dendrite core and interdendritic region under different degrees of elemental inhomogeneity in nickel-based single crystal superalloys

The creep inconsistency between dendrite core and interdendritic region is investigated in a nickel-based single crystal superalloy under 1373 K and 137 MPa.Two specimens with higher and lower degree of elemental inhomogeneity on dendritic structures are compared.For specimen with higher inhomogeneity,stronger segregation of refractory elements reinforces the local strength in dendrite core,but damages the strength in interdendritic region.Creep strain is accumulated faster in interdendritic region giving rise to promoted dislocation shearing inγphase,faster degradation of dislocation networks and facilitated topological inversion of rated structures.Although the segregation of refractory elements produces a high density of topologically close-packed(TCP)phase in dendrite core,faster accumulation of creep strain forms microcracks prior in interdendritic region that gives rise to final rupture of the specimen.In another specimen,increased solid solution time gives rise to overall reduced inhomogeneity.Creep inconsistency is relieved to show more uniform evolution of dislocation substructures and rafting between dendrite core and interdendritic region.The second specimen is ruptured by formation and extension of microcracks along TCP phase although the precipitation of TCP phase is relatively restricted under reduced inhomogeneity.Importantly,the balance of local strength between dendrite core and interdendritic region results in over 40%increase of creep rupture life of the second specimen.

Effect of rare earth on primary carbides in H13 die steel and their addition method:a review

Larger-sized primary carbides lead to stress concentration during the application of H13 hot-work die steel,resulting in microcracks and fatigue failure.Rare earth was usually added to modify the carbides and inclusions.The existing literature is reviewed on the effect of rare earth on primary carbides in H13 steel.A comprehensive review on the effect of rare earth on the characteristics of primary carbides,i.e.,number,size,morphology,and thermal stability in H13 steel,was done.The precipitation mechanism and nucleation of primary carbides with rare earth were summarized.The position and form of rare earth in steel and their effects on alloying elements segregation were reviewed.The addition techniques of rare earth in H13 steel were compared,and the prospects for other uncommon rare earth and emerging technology were present.Based on the current references,it can be known that adding rare earth facilitated refined and dispersed primary carbides.The size of primary carbides would be reduced,and their morphology would be improved because the rare earth inclusions formed in H13 steel can act as nucleation cores forγ-Fe orδ-Fe,refining the dendritic structure.Besides,the number of primary carbides at grain boundaries would be significantly reduced.However,rare earth had little impact on thermal stability.The nucleation of primary carbides tended to be inhibited due to the modification of inclusions by rare earth which were likely to be nucleation cores for primary carbides.Rare earth had been reported to affect the mechanism and process of primary carbide precipitation.Additionally,the addition of rare earth can inhibit the segregation of alloying elements and carbon diffusion by calculation.Thus,laboratory experiments and theoretical calcu-lations need to be conducted to study the states and evolution of rare earth steels.

Solidification crack characteristics and sensitivity of peritectic steel

The characteristics and sensitivity of solidification cracks in peritectic steels were investigated using directional solidifi-cation technology.Interdendritic cracks were observed in both hypoperitectic steels(12CrlMoV,15CrMo)and hyper-peritectic steel(20CrMo)during solidification at growth velocities of 15,50,and 80 pm/s.At the dendritic boundaries,sulphide precipitates were found,promoting crack formation.Based on the statistical analysis of interdendritic cracks in peritectic steels,the area ratio(RA)of interdendritic cracks in a directional solidification structure was proposed to evaluate the crack sensitivity of peritectic steels.Furthermore,the crack sensitivities of peritectic steels(12CrlMoV,15CrMo,and 20CrMo)were tested,evaluated,and compared with the surface crack rates of three types of steels produced from a steel plant.The results demonstrated that RA was in good agreement with that of the steel plant,and the crack sensitivity of 12CrlMoV steel was the strongest,followed by that of 15CrMo and 20CrMo steels.Thus,RA can be used to evaluate the crack sensitivity of peritectic steel.

A second-order nonlinear optical dendronized hyperbranched polymer containing isolation chromophores： achieving good optical nonlinearity and stability simultaneously

Large nonlinear optical(NLO) coefficient and good stability, two essential factors to evaluate second-order NLO materials, are difficult to be achieved in one molecule simultaneously. Herein, by utilizing the concept of "isolation chromophore", "isolation group" and dendritic structure, a dendritic molecule D-NS and a dendronized hyperbranched polymer DHP-NS are prepared to investigate their structure-property relationship. For the small dendritic molecule D-NS, it exhibits a high d33 value of 140 pm/V.But this value can be easily dropped when the temperature is higher than 50 °C, which extremely limits its real application. After introducing D-NS into a dendronized hyperbranched polymer chains, the obtained DHP-NS also shows a high d33 value of101 pm/V, but much better stability than D-NS. Even when its thin film was heated to 120 °C, no obvious decay can be observed in the d33 value of DHP-NS. This work demonstrates an effective strategy to realize both large NLO effect and good stability simultaneously.