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The properties of modified conventional wrought aluminum alloys cannot be significantly enhanced by normal post-heat treatment in that the fine-grained strengthening, arising from high cooling rate in SLM, is underutilized. In this work, compared with the normal T6 heat treatment, a novel simple direct aging regime was proposed to maintain the grain-boundary strengthening and to utilize the precipitation strengthening of secondary Al3Zr. It was found that a heterogeneous grain structure, which consisted of ultrafine equiaxed (∼0.82 μm) and columnar (∼1.80 μm) grains at the bottom and top of molten pool, respectively, was formed in the SLM processed sample. After direct aging (DA), the ultrafine grains were maintained and a mass of spherical coherent L12-Al3Zr particles with a mean radius of approximately 1.15 nm was precipitated. In contrast, after solution treatment and aging (STA), a significant grain coarsening occurred in the equiaxed grain region. Meanwhile, the coarsening L12-Al3Zr particles, nano-sized S′ phases and GPB zones were detected in the STA sample. This subsequently induced that the yield strength of the DA sample (∼435 MPa) was higher than that of the STA sample (∼402 MPa) owing to the grain boundary strengthening and precipitation strengthening. Both the STA and DA samples exhibited a higher strength than that of the other SLMed Al-Cu-Mg series alloys; this was comparable to that of the wrought AA2024-T6 alloy (∼393 MPa). Both the STA and DA samples exhibited a higher strength than that of the other SLMed Al-Cu-Mg series alloys; this was comparable to that of the wrought AA2024-T6 alloy (∼393 MPa).

The synergistic effect of Mo and Zr additions on microstructure evolution, room-temperature fracture toughness and microhardness of Nb-22Ti-15Si-xMo-yZr (x = 4,8, y = 3,6) alloys manufactured by laser directed energy deposited (L-DED) have been investigated. The major phases in as-deposited 4Mo-3Zr alloy are Nb solid solution (Nbss), Nb3Si and γ-Nb5Si3. The Nb3Si phases disappear with increasing Mo content to 8 at.% or increasing Zr content to 6%. γ-Nb5Si3 precipitates formed in the Nbss of as-deposited xMo-yZr alloys due to the cyclic re-heating, and the γ-Nb5Si3 precipitates and Nbss matrix exhibits orientation relationship (OR) of [001]Nbss//[ 1 ¯ 112]γ and (110)Nbss//(01 1 ¯ 0)γ in as-deposited 4Mo-6Zr alloy. The microstructure of xMo-yZr alloys became relative homogeneity and the Nbss matrix showed the better continuity after the heat treatment (1400 °C/30 h). The Nb3Si phase has transformed into Nbss and α-Nb5Si3 with the OR have been determined as {100}Nbss//{100}α and{111}Nbss//{111}α in the heat-treated 4Mo-3Zr alloy. When Mo content increase to 8at.%, a part of γ-Nb5Si3 phase also transformed into the α-Nb5Si3 phase with the OR have been determined as {11 2 ¯ 0}γ//{110}α and {10 1 ¯ 0}γ//{111}α after heat treatment. Among the as-deposited alloys, the 4Mo-6Zr alloy has the highest fracture toughness KQ with the lowest hardness. The average KQ of 4Mo-6Zr and 8Mo-6Zr alloys increased by 28% and 30% after the heat treatment, and reached 13.61 and 11.43 MPa•m1/2, respectively. The hardness of Nb-22Ti-15Si-xMo-yZr alloys is significantly decreased after the heat treatment.

Laser solid forming (LSF) technology can be used to rapidly manufacture and repair high-strength steel parts with superior performance, but the value of the heat input during operation is difficult to quantify, which has a substantial impact on the microstructure and mechanical properties of the parts. A promising method to improve the forming efficiency and quality of LSFed parts is to accurately control the heat input and explore its relationship with the microstructure and mechanical properties. To remove the interference of other variables from the experiment, the dimensionless heat input Q* was introduced. The Q* values were designed in advance to calculate the experimental parameters used to perform the LSF experiment. The microstructure was observed at different regions of the sample, and its mechanical properties were analyzed. From the results, the following conclusions were drawn. The Q* value was directly related to the cooling rate and heat accumulation in the top structure, leading to the formation of different microstructures; it also modified the original structure at the bottom, affecting the subsequent thermal cycle and indirectly changing the tempered martensite morphology. The heat input also affected the mechanical properties of the sample. The hardness of the stable zone decreased with increasing Q* value, and the lowest value was 190 HV. Similarly, the tensile strength and yield strength of the LSFed samples decreased considerably with increasing Q* value, and the lowest values were 735 and 604 MPa, respectively. Only the elongation and reduction in the area increased after a slight decrease. The Q* value had a significant effect on heat treatment. When Q* = 2.9, the increase in tensile strength and yield strength after heat treatment was the largest (29% and 44%, respectively).

Near-equiaxed β grain was achieved in the near-α Ti60 (Ti-5.7Al-4.0Sn-3.5Zr-0.4Mo-0.4Si-0.4Nb-1.0Ta-0.05C) titanium alloy via laser directed energy deposition (LDED). The microstructural evolution along the building direction and the room-temperature tensile properties along the horizontal and vertical directions (building direction) were systematically studied through SEM and OM. EBSD and XRD were utilized to accurately demonstrate the texture of the α and β phases. The results showed that the α phase presented a low texture intensity, which was ascribed to the weak textured β grain with near-equiaxed morphology, since there are Burgers orientation relationships during the β→α transition. In addition, numerical simulation, combined with the CET curve of Ti60 alloy considering the effect of multi-composition, was utilized to elucidate the formation mechanism of the near-equiaxed β grains. Furthermore, according to the solidification theory, we proposed that the solidification temperature range Δ T f was more accurate than the growth restriction factor Q in predicting the formation tendency of equiaxed β grain in different titanium alloys. Tensile results showed that the horizontal and vertical samples had similar strength, while the former exhibited larger elongation than the latter. The effect of the near-equiaxed β grain and the internal α phase on mechanical properties were revealed at last.

At present, polymer PM6 is most widely used donor, many researches focus on the improvement of PM6 performance. Most commonly used strategy of modifying polymer PM6 is to achieve ternary random copolymer by incorporating a third component. However, mostly reported modified PM6 terpolymers are with strictly equal D unit and A unit, while the third component has the disadvantage of high cost and complex synthesis. Herein, we develop four novel D-A-D-D1-type copolymer donors (PM6-T5, PM6-T10, PM6-T15 and PM6-T20 with D1 unit molar ratios of 5%, 10%, 15% and 20%, respectively) by introducing a component (BDT-T) with low synthetic complexity into the backbone of PM6 with unequal D and A unit (D/A unit ratio>1). Compared with alternate D-A copolymer PM6, four D-A-D-D1-type copolymers show the up-shifted lowest unoccupied molecular orbital (LUMO), down-shifted highest occupied molecular orbital (HOMO), higher degree of self-assembly. As a result, owing to the suitable level energy, crystallinity, better absorption, higher hole mobility and prolonger the exciton life, the PM6-T15:Y6-based OSCs achieved high power conversion efficiency (PCE) of 16.61% with a remarkably enhanced short-circuit current density (JSC) of 27.02 mA/cm2 and higher fill factor (FF) simultaneously, which performed better than the reference PM6:Y6-based OSCs (PCE:14.51%).

Laser powder bed fusion (L-PBF) of Sc/Zr-modified Al-based alloys has recently become a promising method for developing a new generation of high-performance Al alloys. To clarify the modification roles of Sc/Zr elements, an Al–4.66Mg–0.48Mn–0.72Sc–0.33Zr (wt.%) alloy was processed using L-PBF. The effect of the local solidification condition of the molten pool on the precipitation behavior of primary Al3(Sc,Zr) was analyzed based on time-dependent nucleation theory. It was found that primary Al3(Sc,Zr) inevitably precipitated at the fusion boundary, while its precipitation could be effectively suppressed in the inner region of the molten pool. This subsequently induced the formation of a heterogeneous α-Al matrix. After direct aging, the heredity of solidification microstructure introduced heterogeneous secondary Al3(Sc,Zr) precipitates within α-Al matrix. Owing to the inverse relationship between grain boundary strengthening and precipitation strengthening, the direct-aged sample with dual heterogeneous structures exhibited reduced mechanical heterogeneity, resulting in lowered hetero-deformation-induced hardening. The low strain-hardening capability in the direct-aged sample promoted necking instability while inducing a large Luders elongation, which effectively improved the tensile ductility.

Although a variety of processing routes were developed to in-situ manipulate microstructure for fabricating high-performance Ti–6Al–4V alloy by directed energy deposition (DED), the in-situ microstructural control ability has been limited and lead to a narrowed mechanical property control range. This work proved the microstructural correlation between β-grains and α-laths resulting from the unique thermal characteristics of DED for the first time and solved such a dilemma through synchronous induction heating assisted laser deposition (SILD) technology. The results confirmed that the laser energy and inductive energy have a different effect on the solidification and solid phase transformation conditions. By adjusting the laser-induction parameters, the microstructural correlation can be tuned; the β-grains and α-laths can be controlled relatively separately, thereby significantly enhancing the ductility of as-deposited sample (elongation from 14.2% to 20.1%). Furthermore, the mechanical properties of the tuned microstructures are even comparable to that of DED Ti–6Al–4V with post heat treatment, which indicates that the potential of SILD to be a one-step manufacturing process to fabricate high performance components without post heat treatment. Furthermore, the tensile testing results of the tuned microstructures indicate that α-lath size is more influential on the mechanical properties than the β-grain size due to its stronger hindering effect on the slipping of dislocations. This work promotes the understanding of the microstructural formation mechanism in DED titanium alloy and proves that the combination of synchronous induction and laser can expand the ability to control the microstructure and properties of multi-layer deposition.

Al–Mg–Sc–Zr alloys manufactured using selective laser melting (SLM) possess outstanding static mechanical properties and thus have great potential application in the aerospace industry. However, their fatigue performance has not been clearly investigated and understood. In this work, the high cycle fatigue properties of an Al–Mg–Sc–Zr alloy manufactured via SLM with optimised process parameters (relative density over 99%) was studied with focus on the defects, whose size, shape and distribution were determined through X-ray tomography. Microstructure analysis results show that the Al–Mg–Sc–Zr alloy produced using SLM presents a periodic, inhomogeneous structure consisting of equiaxed grains at the boundary and columnar grains at the centre of one molten pool, which causes a significant difference in deformational mismatch under the fabrication conditions. Furthermore, X ray-CT results show that the defects, mainly porosity, are randomly distributed with the critical flaw size to initiate fatigue crack, thereby reducing fatigue life. When the stress ratio (R) is 0.1, the annealed sample presents good fatigue strength (σf) reaching 100.5 MPa, which is close to that of high-strength wrought 7075Al. Finally, a fatigue crack propagation mode connected with defect microstructure characteristics was established for prediction of fatigue properties.

p-Benzoquinone (BQ) is a promising candidate for next-generation sodium-ion batteries (SIBs) because of its high theoretical specific capacity, good reaction reversibility, and high resource availability. However, practical application of BQ faces many challenges, such as a low discharge plateau (∼2.7 V) as cathode material or a high discharge plateau as anode material compared with inorganic materials for SIBs and high solubility in organic electrolytes, resulting in low power and energy densities. Here, tetrahydroxybenzoquinone tetrasodium salt (Na4C6O6) is synthesized through a simple neutralization reaction at low temperatures. The four −ONa electron-donating groups introduced on the structure of BQ greatly lower the discharge plateau by over 1.4 V from ∼2.70 V to ∼1.26 V, which can change BQ from cathode to anode material for SIBs. At the same time, the addition of four −ONa hydrophilic groups inhibits the dissolution of BQ in the organic electrolyte to a certain extent. As a result, Na4C6O6 as the anode displays a moderate discharge capacity and cycling performance at an average work voltage of ∼1.26 V versus Na/Na+. When evaluated as a Na-ion full cell (NIFC), a Na3V2(PO4)3 ‖ Na4C6O6 NIFC reveals a moderate discharge capacity and an average discharge plateau of ∼1.4 V. This research offers a new molecular structure design strategy for reducing the discharge plateau and simultaneously restraining the dissolution of organic electrode materials.

The building finish layer is a comprehensive structural system including the building exterior insulation system and building exterior finish. Combining with buildings has the advantage of reducing wall heat loss and building deformation caused by large temperature differences. Since the building finish layer is prone to cracking, hollowing, and peeling, during the application process, its safety needs to be studied and certified. This study prepares 20 groups of specimens, 15 anchor bolts in each group. The anchor bolt pull-out strength test is carried out. Anchoring damage evolution law and failure mode of anchor bolts are investigated. And the influence of anchoring methods on the pull-out bearing capacity is analyzed. In addition, ABAQUS finite element data simulation is carried out. The stress state of finish in thermomechanical coupling condition and without the effect of temperature are compared and analyzed. The influence factors of anchor bolt pull-out strength and the influence of temperature load on the long-term performance of building finish layer are obtained. The durability of the building finish layer is analyzed. The results show that the anchoring strength of the anchor bolt is positively correlated with the anchoring depth. The anchoring strength is influenced significantly by anchoring construction sequence and temperature. The stress under the coupled effect of temperature and load is greater than that of the single effect of load, and the stress distribution changes significantly. Due to thermal expansion and contraction, the anchor bolt would loosen, which is more prone to damage the building finish layer in a low temperature environment. The weight relationship of each influencing factor of the building finish layer is proposed. A systematic evaluation index system is established. The results of this study provide a basis for subsequent related research work and engineering applications.

A new model for predicting elastic flexural wave band gaps in periodic composite plate structures containing interconnected, star-shaped, transversely isotropic, magneto-electro-elastic (MEE) inclusions is developed using a microstructure-dependent Mindlin plate model. The Floquet–Bloch theorem and the plane wave expansion method for periodic media are employed to solve the non-classical wave equations and to determine the band gaps incorporating the microstructure effect. The current non-classical model recovers its classical elasticity-based counterpart as a special case if the microstructure effect is suppressed. A parametric study is performed to demonstrate the newly developed model. The numerical results of the study show that the microstructure effect on band gaps is large when the plate is very thin. In addition, the unit cell edge length, inclusion geometry and MEE coupling have significant effects on band gap sizes, and large band gaps can be generated by tailoring the controlling parameters.

Electrochemical CO2 reduction provides a promising strategy to product value-added fuels and chemical feedstocks. However, it remains a grand challenge to further reduce the overpotentials and increase current density for large-scale applications. Here, spontaneously Sn doped Bi/BiOx nanowires (denoted as Bi/Bi(Sn)Ox NWs) with a core-shell structure were synthesized by an electrochemical dealloying strategy. The Bi/Bi(Sn)Ox NWs exhibit impressive formate selectivity over 92% from -0.5 to -0.9 V versus reversible hydrogen electrode (RHE) and achieve a current density of 301.4 mA cm-2 at -1.0 V vs RHE. In-situ Raman spectroscopy and theoretical calculations reveal that the introduction of Sn atoms into BiOx species can promote the stabilization of the *OCHO intermediate on the Bi(Sn)Ox surface and suppress the competitive H2/CO production. This work provides effective in situ construction of the metal/metal oxide hybrid composites with heteroatom doping and new insights in promoting electrochemical CO2 conversion into formate for practical applications.

Synchronous induction-assisted laser deposition (SILD) is a widely used powder feeding-based additive manufacturing technology developed from directed energy deposition (DED). In SILD, the powder feed behavior is a decisive factor for the geometrical features and microstructure of the deposition. Therefore, the study about the influence mechanism of processing parameters on the powder flow feed behavior in an electromagnetic field is important for the application of SILD. In this research, the distribution of 30CrMnSiA steel powders injected in SILD was obtained via experimental observation, and the influence of the parameters on the powder flow characteristics was elucidated using electromagnetic field simulation and theoretical analysis. It was confirmed that the moving particles undergo an acceleration caused by the Lorentz force related to the distribution of the electromagnetic field, magnetic flux density, and the injection speed of the powder. The Lorentz force accelerated the particles and inclines, which diverged the powder flow. The maximum powder concentration decreases with increasing input current; first increasing and then decreasing with the increase of the carrier gas flow rate. The powder feed rate remains an indistinctive factor of the powder flow characteristics in a manner similar to traditional laser manufacturing.

Once fires occur in a coalfield, large quantities of coal in the coalfield will be baked at high temperatures. The changes and differences in the microscopic and spontaneous combustion properties o...

Large temperature gradient and local hot spot in solar receiver seriously impact the operation safety and thermal performance. To improve the temperature uniformity of porous foam absorber in a volumetric solar receiver, this work presents a receiver with an annular inner window to reshape the fluid field in the receiver. To examine the improvement effect of the proposed receiver, one numerical model is developed to analyze the coupled heat transfer in the receiver. The model takes the propagation of concentrated solar irradiation and thermal radiation in the consideration by using the Monte-Carlo ray tracing method. The effects of the inner window on the fluid flow and temperature distribution of the absorber as well as the efficiency of the receiver are analyzed. The results show that the standard difference of temperature in absorber of the proposed receiver is 35–158.6 K lower than that of the single windowed one, and the thermal efficiency is increased by 2.86%–7.18%, within the inner radius of the annular window range of 15–45 mm and flow rate of 4–7 g/s. It is demonstrated that installing an annular window is an effective approach to improve the uniformity of absorber temperature while increasing the thermal performance.

MoS2 nano-films have attracted extensive interest from scientists owing to its unique material properties with adjustable bandgap structure and broad application prospects in electronic and optoelectronic devices. Herein, we report a chemical vapor deposition method based on adjusting the relative position of the molybdenum source and SiO2/Si substrates to control MoO3 concentration adsorbed on the surface of substrate to achieve the controlled growth of monolayer single crystal MoS2 with spatial uniformity and low nucleation density. Moreover, optical microscopy, Raman, photoluminescence, atomic force microscopy and transmission electron microscope were employed to characterize the uniformity and crystal quality of the grown monolayer MoS2. The measurement results show that the triangle side length of a single MoS2 film can reach 110 μm. And the I-V switching ratio of the back-gate field effect transistors based on growing MoS2 is 6.3 × 108, which is equivalent or slightly higher than that of other CVD-grown samples. Besides, growth mechanism of MoS2 was further investigated, combining the substrate position with concentration of MoO3 deposited on the surface of substrate. This work is of great benefit to the controlled growth of other two-dimensional materials and uniform performance of multiple electronic array devices.

Peritectic solidification has attracted increasing attention as a lot of important binary alloys, such as Fe–Ni, Zn–Cu, Fe–C and Ti–Al, exhibit peritectic reaction during solidification. In order to investigate the solidification behavior of Zn-rich Zn–Cu peritectic alloy containing nominally up to 7.8 wt.% Cu, a series of laser surface remelting experiments were performed. With the increase in growth velocity, Zn–Cu alloys with Cu content below 3.0wt.% showed an evolutional sequence from low-velocity η planar interface → lamellar structures → η shallow cells and finally to high-velocity η planar interface. The Zn-4.0 wt.%Cu alloy showed a similar transitional sequence except that irregular η cells appeared when low-velocity planar interface became unstable. In contrast, e cell/dendrite was the typical microstructure of the Zn-7.8 wt.% Cu alloy within the whole scanning velocity range. Based on the maximum interface temperature criterion, a eutectic growth model under rapid solidification conditions (TMK model) and a self-consistent numerical model for the cellular and dendrite growth were applied to establish a phase and microstructure pattern selection map, which drew a clear whole picture of the relationship between phase/microstructure and solidification conditions of this series of alloys. Regarding the microstructure feature, our investigation revealed the range of the solidification velocity and chemical composition of lamellar structures as dominant microstructure and their lamellar spacing displayed a considerable range of the average value as a function of growth velocity. The relationship between the lamellar spacing and the growth velocity was further analyzed by using the TMK eutectic model, and the results showed the same overall trend as the experimental results. A phase and microstructure pattern selection map of Zn-rich Zn–Cu peritectic alloys. Regression analysis of the average spacing of lamellar structures.

Electronic doping of organic semiconductors is essential for their usage in highly efficient optoelectronic devices. Although molecular and metal complex-based dopants have already enabled significant progress of devices based on organic semiconductors, there remains a need for clean, efficient and low-cost dopants if a widespread transition towards larger-area organic electronic devices is to occur. Here we report dimethyl sulfoxide adducts as p-dopants that fulfil these conditions for a range of organic semiconductors. These adduct-based dopants are compatible with both solution and vapour-phase processing. We explore the doping mechanism and use the knowledge we gain to 'decouple' the dopants from the choice of counterion. We demonstrate that asymmetric p-doping is possible using solution processing routes, and demonstrate its use in metal halide perovskite solar cells, organic thin-film transistors and organic light-emitting diodes, which showcases the versatility of this doping approach.

The control of grain morphology is important in laser additive manufacturing (LAM), as grain morphology further affects the hot cracking resistance, anisotropy, and strength–ductility synergy of materials. To develop a solidification-control solution and achieve columnar-to-equiaxed transition (CET) in Al-based alloys during LAM, Sc-and-Zr-modified Al-Mg alloys were processed via directed energy deposition (DED). CET was achieved by introducing high potent primary Al3(Sc,Zr) nucleation sites ahead of the solidification interface. Furthermore, the relationship between the solidification control parameters and precipitation behavior of primary Al3(Sc,Zr) nucleation sites was established using the time-dependent nucleation theory. Then, the CET was studied according to the Hunt criterion. The results indicated that coarse columnar grain structure was still obtained at the inner region of the molten pool at low Sc/Zr contents owing to the effective suppression of the precipitation of the primary Al3(Sc,Zr) nucleation sites via rapid solidification during DED. In addition, the relatively low melt temperature at the fusion boundary unavoidably promoted the precipitation of primary Al3(Sc,Zr) nucleation sites, which resulted in a fine equiaxed grains band at the edge of the molten pool. As the Sc/Zr content increased, the solidification cooling rate was not sufficient to suppress the precipitation of the primary Al3(Sc,Zr) nucleation sites, and a fully equiaxed grain structure was obtained. Furthermore, the effect of the layer-by-layer manufacturing process on the subsequent precipitation strengthening of secondary Al3(Sc,Zr) precipitates was discussed. Both the remelting and subsequent aging during thermal cycling should be considered to achieve greater precipitation strengthening.

A series of single track clads of Inconel 625 alloy were fabricated by laser solid forming. To achieve the high dimensional accuracy and excellent mechanical properties, the effect of processing parameters on the geometry, the formation of Laves phase and the residual stress was investigated. The results show that laser power and scanning speed had a dramatical influence on the width and height of single-track clads. According to the columnar to equiaxed transition curve of Inconel 625, the grain morphology can be predicted during the LSF process. With the increasing laser power and the decreasing scanning speed, the segregation degree of Si, Nb, Mo, the volume fraction and size of Laves phase increased. Vickers indentation was used to demonstrate that optimizing processing parameter can achieve the minimum residual tensile stress.

The establishment of highly permanent porosity in hydrogen-bonded organic frameworks (HOFs) is a long-standing challenge due to the fragile nature of hydrogen bonds, which delimits their broad appl...

A non-classical model for circular cylindrical thin shells is developed by using a modified couple stress theory and a surface elasticity theory. The equations of motion and boundary conditions are simultaneously obtained by a variational formulation based on Hamilton’s principle, which provides a unified treatment of the microstructure and surface energy effects. The new non-classical shell model contains one material length scale parameter to capture the microstructure effect and three surface elastic constants to describe the surface energy effect. The current model includes the shell models considering the microstructure effect only or the surface energy effect alone as special cases. Also, the newly developed shell model reduces to the classical circular cylindrical Love–Kirchhoff thin shell model when both the microstructure and surface energy effects are suppressed. In addition, it recovers the non-classical model for Kirchhoff plates incorporating the microstructure and surface energy effects when the shell radius tends to infinity. To illustrate the new model, the static bending and free vibration problems of a simply supported closed circular cylindrical shell and of an open circular cylindrical shell with free edge boundary conditions are analytically solved by directly applying the model. For the static bending problem in each case, the numerical results show that the shell deflection predicted by the current model is smaller than that predicted by the classical model, and the difference is significant when the shell is very thin but diminishes as the shell thickness increases. For the free vibration problem in each case, it is found that the natural frequency predicted by the new model is higher than that predicted by its classical counterpart, and the difference is large only for very thin shells.

In this study, the development of surface features of Inconel 718 samples fabricated by selective laser melting under different laser powers and scanning speeds has been studied and correlated with the powder melting behaviors through both experimental and modeling approaches. The interaction between laser beam and powder particles was studied by a three-dimensional model using the height function-lattice Boltzmann method. Different process parameters were introduced to perform the simulations, revealing the underlying physics of the surface morphology. Through the calculation of the surface forces, some new insights were given about the powder melting behaviors and the resultant surface features. It was found that the surface tension rather than recoil pressure pulled the melted powder into the molten pool during the SLM process. As for low energy input, the powder tended to fuse together with the neighboring particles before entering the molten pool, which was found to be the main cause of the formation of surface fluctuations and the subsequent surface pores. To some extent, the existence of recoil pressure was favorable for a relatively stable flow and a flat surface morphology. The simulation results of the top surface morphology were compared with experimental results, and they were in good agreement.

In this study, non-toxic in-situ β phases of reinforced Ti/Zr-based bulk metallic glass matrix composites (BMGCs) of (Ti0.65Zr0.35)100-xCux (x = 5, 10, 15 at.%) are fabricated via selective laser melting. The effect of Cu content on phase formation, microstructure, and mechanical properties is investigated. The average volume fraction and width of the β phase decreases with increasing Cu content, while a more amorphous phase and the (Ti, Zr)2Cu phase forms. In the center zone of the molten pool, the β phase grows in the direction of the temperature gradient, and the amorphous phase distributes among the β phases. This occurs using: sphere morphology (for x = 5), a more continuous elongated sphere and network morphology (for x = 10), and network morphology (for x = 15), respectively. In the edge zone of the molten pool, due to the smaller cooling rate and the existence of a partially molten zone, the β phase becomes coarser, and an amorphous phase forms for more continuous networks. Furthermore, the hardness improves significantly with increasing Cu content. No crack is found for x = 5. Although the average volume fraction of the β phase for x = 5 is about 90 %, the compression yield strength is 1386 ± 64 MPa, reaching to an average level of conventionally fabricated counterparts, due to finer microstructure, and twinning and martensitic transformation of the β phase.

Electrochemical CO2 reduction is a promising technology for solving the CO2 emission problems and producing value-added products. Here, we report a hierarchically porous Cu1Au single-atom alloy (SAA) as an efficient electrocatalyst for CO2 reduction. Benefiting from the hierarchically porous architectures with abundant vacancies as well as three-dimensional accessible active sites, the as-prepared nanoporous Cu1Au SAA catalyst shows remarkable CO2 reduction performance with nearly 100% CO Faraday efficiency in a wide potential range (−0.4 to −0.9 V vs . reversible hydrogen electrode. The in-situ X-ray absorption spectroscopy studies and density functional theory calculations reveal that the Cu-Au interface sites serve as the intrinsic active centers, which can facilitate the activated adsorption of CO2 and stabilize the *COOH intermediate.

A new microstructure-dependent non-classical model for Kirchhoff plates is developed by using a reformulated strain gradient elasticity theory that incorporates both the strain gradient and couple ...

Unlike silicon carbide ceramic, the alumina ceramic and zirconia ceramic are by its very nature weakly absorbing in visible and near infrared wavebands. Therefore, open-cell foams made of such ceramics are rarely used in applications requiring strong absorption of radiation energy, such as solar absorbers. In order to improve the potential of such foams, open-cell foams with dual-scale pores were digitally designed in the limit of geometric optics. The first-order pores are obtained by Voronoi tessellation technique and then the second-order pores are realized by the design of 'porous strut'. A Monte Carlo Ray-tracing method is applied in the dual-scale foam structure for radiative transfer calculation. The parameterized study is conducted on the radiation absorption of alumina foam sheets and zirconia foam sheets. The results show that for the present cases, the designed dual-scale alumina foams with strut porosity p s = 0.3 can increase the normal absorptance within the wavebands from 0.4 μm to 7.0 μm by 62.7% than the foams with single-scale pores. For the zirconia foams, this increase is 115.9% within the wavebands from 1.2 μm to 7.6 μm. The findings can provide strong confidence on dual-scale foams to enhance the absorption of radiation energy in potential applications.

We herein successfully realized the first example of using a stable HOF (ZJU-HOF-1) for highly efficient removal of both trace (1%) and bulk (50%) CO2 from CO2/CO mixtures under dry and humid conditions.

The microstructure evolution and tensile properties of laser directed energy deposition (LDED) 300 M steel with isothermal heat treatment at 320 ℃ for different holding time were investigated in this paper. The results showed that the microstructure of the as-deposited LDED 300 M steel consisted of martensite and bainite. After heat treatment, the microstructure of the LDED 300 M steel is still the mixture of martensite, bainite and retained austenite, while the size of the lower bainite significantly decreased. As the increasing holding time, the content of martensite gradually decreased, while the content of bainite and austenite gradually increased. When the holding time of LDED 300 M steel increased from 20 min to 40 min, the number and size of austenite increased slightly. However, when the holding time was 60 min, the number and size significantly increased. As holding time continuously increase, it contributes little to the number and size of austenite. With regard to the hardness of the LDED 300 M steel, it was 464 HV when the holding time was 20 min. With the increment of holding time, the hardness gradually decreased until 428 HV when the holding time was 80 min. While holding time had less effect on the tensile strength and yield strength. To be specific, the tensile strength decreased from 1348 MPa to 1332 MPa, and yield strength decreased from 853 MPa to 759 MPa. The elongation gradually increased, and it increases to 33 % when the holding time was 80 min, which was higher than that of the forged 300 M steel standard (15 %). Effect of various factors, like microstructure, dislocation density and e-carbides precipitated in the bainite on the ductility of the LDED 300 M steel with isothermal heat treatment was also studied.

The inkjet 3D printing has been one of the most studied and applied additive manufacturing (AM) processes in electronic industry. In this AM process, the forming quality is greatly influenced by the micro-droplet deposition and substrate temperature. While most studies focus on the formation mechanism of droplets, there are few studies on the quantitative evaluation of the droplet surface profile and its qualitative correlation with temperature changes. In this study, the characteristics of droplet profile in three-dimensional inkjet printing were studied from two aspects, the modeling of droplet shape and the estimation of droplet temperature. For this purpose, different types of radial basis function networks (RBFN) are applied. The validity of the regularized RBFN model is developed and verified by experiments. The results show that the droplet shape can be accurately modeled and the drying temperature can be accurately estimated given the model.

In order to achieve the microstructure homogeneity at a lower temperature and improve the mechanical properties, a novel post heat treatment was introduced to Inconel 718 fabricated by laser direct energy deposition (LDED), by means of δ aging treatment + solution treatment. The microstructure analysis shows that the fully precipitation of δ phase in LDED Inconel 718 superalloy can “cut” the long strip Laves phase into small pieces. According with the δ phase solution treated at 1020 °C for 30 min, only tiny particle Laves phase was remained. The equilibrium volume fraction of Laves phase after δ phase solution treatment is about 1%, which is much lower than that of the as-deposited sample or the sample only solution treated at 1020 °C. Due to the solution strengthening and precipitation of γ″ phase during aging treatment, the tensile strength of δ aging + δ solution + double aging treated samples was 10.27% higher than that of directed solution + double aging treated samples, as well as a 31.38% and 52.71% increases in elongation and the reduction of area during tensile tests.

A shear-lag model is developed for discontinuous fiber-reinforced composites with a membrane-type imperfect interface, across which the displacement vector is continuous but the traction vector suffers a jump that is governed by the generalized Young–Laplace equation. Closed-form expressions are obtained for the stress fields in both the fiber-reinforced region and the pure matrix regions and for the shear stress on the interface from both the fiber and matrix sides. To illustrate the newly developed analytical model, a numerical analysis is provided by directly using the general formulas derived. The numerical results reveal that the fiber aspect ratio and the interface parameter can both have significant effects on the stress distributions in the composite.

The essence of the mathematical model of disconnectors' multiple reignition arc is the repeated breakdowns of SF6. In this study, the kinetic properties of microparticles are studies based on the streamer discharge theory, and a fluid arc mathematical model applied in centimetre clearance is established. Ultra-High Voltage (UHV) disconnector manufactured by Pingao Electric Co. Ltd of Henan Province is selected as the object and the resistance change process of contact clearance multiple reignition arc is simulated by finite difference method-finite element method-flux corrected transport self-programming in MATLAB based on the chamber structure and operating characteristics. UHV gas-insulated switchgear very fast transient overvoltage (VFTO) test platform is built to gain the characteristics of VFTO waveforms generated by the disconnector's operation. Compared with simulation results, the test data shows that the fluid arc mathematical model can scientifically explain the dynamic development process of microparticles in the contact clearance and the calculation results are consistent with the test data. In addition, the arc fluid mathematical model combines the structure and operating characteristics of the switch with the development process of microparticles, which can better guide the design of the switch, and provide a theoretical basis for the suppression of VFTO with the disconnector itself.

In this work, one three-dimensional periodic composite structure consisting of alumina frame and inscribed nickel spheres is proposed for designing the micron composite porous structure. The finite...

Roma Plastilina (RP) # 1 clay has been used as a backing material in ballistic testing of body armor. Column-drop tests are conducted to assess the suitability of RP # 1 clay for ballistic tests. I...

Porous ceramic material is widely used in a great deal of fields. In this work, porous alumina ceramics with micron open cells are modeled by applying the inverse opal structure. The considered porous alumina ceramics are periodic with different size parameters. The diameters of spherical pores are 200, 400, 600, and 800 nm, while the ratios of height to diameter range from 0.1 to 0.9. The absorptivity, transmissivity, and reflectivity for the wavelength range from 0.2 to 2 μm are calculated using the finite difference time domain (FDTD) method. Then the effects of size parameters and incident angle on the optical properties are discussed. The results show that the absorptivity is usually very small. For the transmissivity, a wide dip in the transmission spectrum appears when the diameter and height exceed the critical values, and a red shift of the transmission spectrum's wide dip with increasing height is observed. When the incident wavelength is longer than the critical wavelength, the spectral transmissivities of porous ceramics with a certain diameter reach a stable domain. Moreover, the red shift of the wide dip, the critical incident wavelength, and the critical ratio of height to diameter are visibly affected by the size parameters and the incident angle.

Precise tuning of photoinduced charge separation and transport has been an enduringly central issue in photocatalysis but has met with limited success. In particular, the controllable, accurate and simultaneous modulation on the charge (electrons/holes) transfer pathway in photocatalytic selective organic transformations has not yet been achieved. Herein, as a proof-of-principle demonstration, we report the fine tuning of charge separation/migration by smartly constructing spatially separated charge transport channels over diverse metal/transition metal chalcogenide [(M/TMC), M = Au, Ag, Pd, TMCs = ZnIn2S4, CdIn2S4, In2S3, and CdS] heterostructure photosystems, which were elaborately crafted by an efficient surface ligand-triggered electrostatic self-assembly. Accordingly, tailor-made positively charged branched poly(ethylene imine) (bPEI)-capped metal nanocrystals (NCs) were controllably and uniformly anchored on the two-dimensional (2D) TMC nanosheet (NS) framework, resulting in well-defined metal/TMC heterostructures. We found that electrons photoexcited over TMC NSs could be spontaneously, smoothly and unidirectionally migrated to closely integrated metal@bPEI NCs, wherein the metal core acts as a Schottky-type electron-trapping reservoir and bPEI ligand as a hole transfer mediator, synergistically affording spatially separated charge transfer channels and expediting the charge separation/transfer efficiency. Benefiting from these merits, the self-assembled M/TMC heterostructures exhibited conspicuously boosted photoactivities in the visible light-driven selective organic transformation toward the anaerobic reduction of aromatic nitro compounds to amino derivatives, which are superior to pristine TMCs and M/TMCs without ligand encapsulation. More significantly, the self-assembly strategy and charge modulation concept are universal for diverse metal NCs and TMCs. Thus, our study provides a general and effective protocol to construct a host of metal/TMC heterostructures and stimulates new inspiration for modulating tunable charge separation/migration for substantial solar energy conversion.

In this study, a precision bandgap reference with a v-curve correction (VCC) circuit is presented. The proposed VCC circuit generates a correction voltage to reduce the temperature drift of the reference voltage and achieves a low temperature coefficient (TC) in a wide temperature range. The proposed bandgap reference was designed and fabricated using a standard TSMC 0.18-$\mu \text{m}$ 1P6M CMOS technology with an active area of 0.0139 mm2. The measured results show that the proposed bandgap reference achieves a TC of 1.9-5.28 ppm/°C over a temperature range of -40°C to 140 °C at a supply voltage of 1.8 V. In addition, the circuit demonstrated a line regulation of 0.033 %/V for supply voltages of 1.2 - 1.8 V at room temperature.

Wire + arc additive manufacturing (WAAM) was preliminarily employed to fabricate the 2219 aluminum alloy. The influence of the electric arc travel speed (TS) on the macro-morphology, microstructure, and mechanical properties were investigated. The results indicated that as the electric arc TS increased, the size and the volume fraction of equiaxed grain decreased. The high arc TS during WAAM also promoted the precipitation of the θ (Al2Cu) phase. The volume fractions of θ″ and θ′ phases reached maximum values when TS is 350 and 250 mm/min, respectively. The thermal cycle facilitated the precipitation of the θ′ phase. In addition, the micro-hardness and tensile strength of the alloy were analyzed, and the results indicated that samples fabricated at TS of 350 mm/min possessed finer equiaxed grain and exhibited higher ultimate tensile strength (273.5 MPa) and yield strength (182.9 MPa) compared to those fabricated at 250 mm/min.

Modulating photo-induced charge separation/transfer constitutes a central challenge in heterogeneous photocatalysis. Despite advancements in this area, finely tuning directional electron migration without involving conventional co-catalysts [e.g., metal nanocrystals and transition metal dichalcogenides (TMDs)] for boosted photoredox catalysis has not yet been explored. Herein, we report the exquisite design of a novel and general macromolecule-modulated photoredox selective organic transformation system, wherein an ultrathin macromolecular poly(diallyldimethylammonium chloride) (PDDA) layer was integrated at the interface of wide-band-gap (WBG) and narrow-band-gap (NBG) semiconductors to construct heterostructured photocatalysts. The ultra-thin PDDA interim layer expedites interfacial unidirectional electron transfer from the NBG to WBG semiconductor, resulting in a cascade electron transfer channel. The favorable energy level alignment among the building blocks, intimate interfacial integration and multilayered nanoarchitecture endow the WBG@PDDA@NBG heterostructures with substantially enhanced and versatile photoredox performance toward the selective oxidation of aromatic alcohols to aldehydes and the anaerobic reduction of nitroaromatics to amino compounds under visible light irradiation. This can be ascribed to the crucial role of the ultrathin intermediate PDDA layer as a highly efficient metal and TMD-free charge transfer mediator, relaying the electrons from the NBG to WBG semiconductor and slowing charge recombination. Our work could open up new frontiers to exploit diverse metal and TMD-free photocatalytic systems and provide a first insight into the fine tuning of charge transport utilizing non-conductive ionic polymers for solar energy conversion.

Z-Scheme artificial photosystems, resembling the natural photosynthesis procedure, circumvent the disadvantage of a single-ingredient photosystem and hold fascinating prospects for solar energy conversion. Despite the advancements, bottom-up elaborate design of composite heterostructured Z-scheme photosystems by flexible interface engineering for photoredox organic transformation has been poorly investigated. We herein report the construction of a metal-based Z-scheme photoredox system via a progressive self-assembly strategy integrated with a facile photo-deposition. Tailor-made hierarchically branched ligand-capped Pd nanocrystals (NCs) sandwiched in-between a WO3 nanorod (NR) core and CdS shell are harnessed as the charge transport modulator to regulate the interfacial oxidation–reduction kinetics for boosted Z-scheme photocatalysis. The intermediate Pd NCs as Schottky-type electron flow mediators considerably accelerate the unidirectional Z-scheme charge motion rate, endowing multilayered WO3@Pd@CdS core–shell heterostructures with significantly boosted net efficiency of photoactivities toward anaerobic selective nitroaromatic reduction to amino derivatives and aromatic alcohol oxidation to aldehydes under visible light illumination. The predominant active species produced in the versatile photocatalytic selective organic transformation were explored and photocatalytic mechanisms were thus ascertained. Our endeavor could offer a promising route for smartly crafting diverse heterostructured Z-scheme photoredox systems for solar energy conversion.

Monte Carlo method (MCM) and finite volume method (FVM) are integrated to deal with combined conduction-radiation heat transfer problems in irregular geometries containing gray semitranspar...

It is difficult to fabricate lightweight ceramic parts with well pore control and high structural complexity. In this paper, lightweight mullite ceramics with controlled porosity and enhanced properties were prepared via selective laser sintering (SLS) using mechanical mixed FAHSs/PA12 (Fly ash hollow spheres/polyamide 12) composites. Crack-free ceramic green bodies were prepared through SLS using the optimized process parameters: 7.2 W in laser power, 1600 mm/s in scanning velocity and 0.11 mm in hatch spacing. The influence of PA12 content on porosity, size distribution of open pore, mechanical properties and thermal property were studied. The pores in ceramic foams consisted of the closed pores from sphere core-shell structures, the open pore channels in the middle of stacking spheres and the special gaps in the middle of spheres related to SLS. It was found that the total porosity of lightweight mullite ceramics increased slightly from 85.1 ± 0.3% to 85.2 ± 0.4% with PA12 content increasing from 10 to 15 wt%, and then increased obviously to 86.7 ± 0.5% with further increasing PA12 addition to 25 wt%. This porosity increase was mainly attributed to the open pores resulted from the PA12 addition. The PA12 were firstly filled into the interspaces between stacking spheres and when the stacking volume reached the maximum, the interspaces expanded to form the special gaps between spheres with further PA12 addition. Thus, the size distribution of open pore in lightweight FAHS ceramics increased from 31.5 to 34.5 μm gradually with PA12 content increasing from 10 to 25 wt%. Finally, low thermal conductivity of 0.06 W/(m·K) was obtained, which probably resulted from the high porosity and the special pore structures of the SLS-formed ceramic foams. The understanding of the unique pore structures and microstructures will help the pore control and strength improvement of SLS-formed ceramic foams using the ceramic hollow spheres.

The low cycle fatigue (LCF) properties of Ti-6Al-4V parts fabricated by high-power laser directed energy deposition were investigated. The results show that the parts after solution treatment and aging exhibit superior LCF lives to those of other reported AM Ti-6Al-4V parts, as well as are comparable to those of the wrought counterparts at intermediate strain amplitudes (from 0.8% to 1.1%). Cyclic softening behaviors were found at various strain amplitudes (from 0.65% to 1.7%). In addition, a microstructure-based multistage fatigue model was used to predict their LCF lives and shows good agreement with the experimental data.

In-situ ductile dendrite reinforcement is the most effective method to improve the plasticity of bulk metallic glasses. In this study, an in-situ beta phase reinforced Ti/Zr-based bulk metallic glass matrix composite (BMGC), (Ti0.65Zr0.35)90Cu10, was deposited via selective laser melting. Its microstructural characteristics and indentation deformation behaviors were investigated. There were fine and coarse microstructures in the BMGC, due to the existence of heat-affected zone, and they were finer than the microstructures of the BMGCs prepared using traditional technologies; the amorphous and beta phases could be coordinately deformed during the indentation process.