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Graphite, whose presence is harmful to the mechanical property, is one of the main reaction products between Ni-based alloy and SiC. This paper reports a method of eliminating graphite based on thermodynamic calculations. Different amounts of Si powders are added into the Inconel 625 powder filler to adjust the interfacial reactions during the brazing process. When the Si content in the liquid reaches the theoretically calculated value, the reactions between the Inconel 625 filler and SiC substrate are suppressed, and no graphite forms on the interface. The graphite-free SiC joints show good oxidation resistance. The joint's strength maintains at 25.7 MPa while that with graphite drastically drops to 5.5 MPa after 185 h oxidation in air. The reaction products and oxidation process of the SiC joints are also carefully analyzed in this paper.

In this work, we used the selective laser melting (SLM) fabricated Co-Cr alloy with prominent residual strain, extremely non-equilibrium microstructures, and low stacking fault energy as a precursor to fabricate materials with the optimal grain boundary character distribution. The grain boundary engineering (GBE) of the Co-Cr alloy was achieved by a simple heat treatment of the SLM-fabricated Co-Cr alloy. The obtained GBE Co-Cr alloy exhibited 81.47% of special grain boundaries (Σ3n n = 1, 2, 3)), while it substantially disrupted the connectivity of the random high-angle boundaries, successfully reducing the propensity of intergranular degradation. Slow strain rate tests (SSRTs) showed that the GBE Co-Cr alloy possessed lower stress corrosion cracking (SCC) susceptibility and higher ductility in the corrosive environment (0.9% NaCl solution) than in the air. The high fraction of special boundaries, coupled with the stress-induced martensitic transformation (SIMT) in the GBE Co-Cr alloy yielded these results, which unique and rarely simultaneously satisfied for common structural materials. The current “SLM induced GBE strategy” offers a novel approach towards customized GBE materials with high SCC resistance and ductility in the corrosive environment, shedding new light on developing high-performance structural materials.

Ni-based alloys are believed to be the most suitable brazing fillers for SiC ceramic application in a nuclear environment. However, graphite, which severely deteriorates the mechanical property of the joint, is inevitable when Ni reacts with SiC. In this paper, Different amounts of Zr powders are mixed with Inconel 625 powders to braze SiC at 1400 °C. When Zr addition reaches 40 wt%, the brazed seam confirms the absence of graphite. This research proves that Zr can avoid the graphite’s formation by suppressing Ni’s activity. The room-temperature shear strength of the joint with graphite’s absence is tested to be 81.97 MPa, which is almost three times higher than that of the joint with graphite. The interfacial reaction process and mechanism of the SiC joint are investigated and explained in this paper using thermodynamic calculations.

In this paper, the interfacial reaction is investigated by joining SiC ceramic with Inconel 625 superalloy interlayer at different temperatures. CALPHAD method is used based on a Ni-Cr-Si ternary thermodynamic database to analyze the reactions between the Inconel 625 superalloy and the SiC ceramic. It is found that when the liquid alloy reaches a specific composition, the reactions between them stop. An equilibrium is established between the liquid alloy and SiC during the joining process, regardless of the temperature change. Furthermore, thermodynamic predictions of the reaction products are proved right by EBSD and XRD analysis. This work demonstrates that CALPHAD is a suitable method for effectively investigating the complex reaction system and further promoting precise theoretical analysis.

To investigate the reaction mechanism of Ni/SiC system, 0.1 μm-thick pure nickel foil is used to join SiC ceramic at 1245 °C for different times. Interfacial melting is calculated to occur at 964 °C along the interface due to the low eutectic point of θ-Ni2Si and NiSi, a periodical layered structure, consisting alternating layers of silicides/silicides+graphite, is formed along the interface due to periodical detachment of graphite from SiC reaction interface during the reactions between Ni-Si liquid phase and SiC. The reaction products of Ni/SiC are successfully predicted by CALPHAD method, based on a home-made Ni-Si-C ternary database. The reaction processes between Ni and SiC and the morphology changes of the joined seam are discussed in detail in this paper. The average shear strengths of SiC joints held for 15 min, 30 min and 60 min are tested to be 16.53 MPa, 19.32 MPa and 29.43 MPa, respectively.

To apply the dental Co-Cr-Mo-W alloy restorations fabricated by selective laser melting to clinical use cases, it is necessary to perform a subsequent heat treatment (HT) after SLM processing. However, investigations regarding the effects of HT temperatures on microstructures and mechanical properties inherent in SLM-manufactured Co-Cr-Mo-W alloys are still insufficient. In this article, the microstructure variation during HT at different temperatures and its effect on mechanical properties were systematically investigated and discussed. The Co-Cr-Mo-W dental alloys fabricated by SLM were heat treated at 750 °C, 850 °C, 950 °C, 1050 °C, and 1150 °C for 1 hour and subsequently air cooled. Then, the microstructures were characterized and the mechanical properties evaluated. The results showed that, during HT, Co3(Mo, W)2Si intermetallic compounds with hcp crystal structures precipitated in specimen matrixes and at grain boundaries. With heat treatment temperatures increasing from 750 °C to 950 °C, the number of precipitates gradually increased, and the volume gradually grew. When the temperature increased to ≥ 1050 °C, the number of intermetallic compounds decreased. On the other hand, with increasing HT temperatures, the content of e-Co phases increased initially but then dropped, reaching a maximum of 97.5 pct at 950 °C and a minimum of 4.4 pct at 1150 °C. Furthermore, there is a coherent relationship between hcp phases (e-Co) and fcc phases (γ-Co), and the two lattice cells allow the relative orientation of {0001}e//{111}γ, 〈11-20〉e //〈110〉γ. Mechanical test results showed that, with increasing HT temperatures, the 0.2 pct yield strength (0.2 pctYS) and ultimate tensile strength (UTS) increased initially and then dropped, reaching a maximum value at 850 °C. Conversely, the ductility decreased initially and then rose, reaching a minimum at 850 °C and 950 °C. The mechanical properties depended primarily on the change of volume fractions of the e-Co in mixture as well as the size, morphology, and distribution of precipitates. Additionally, specimens heat-treated at 1050 °C for 1 hour were superior to as-SLM (AS) specimens in both strength and ductility.

The implementation of Terahertz (THz) modulation is critical for applications in high-speed wireless communications, security screening and so on. Therefore, it is particularly significant to obtain THz wave modulation devices with stable and flexible performance, easy manipulation of the modulation method, and multi-functionality. Here, we propose a flexible all-dielectric metamaterial by embedding zirconia (ZrO2) microspheres into a vanadium dioxide/polydimethylsiloxane (VO2/PDMS) composite, which can achieve thermal and mechanical tuning of THz wave transmission. When the temperature of the ZrO2/VO2/PDMS metamaterial increases, VO2 changes from the insulating phase to the metallic phase, and the 1st (at 0.304 THz) and 2nd (at 0.414 THz) order magnetic resonances exhibit the tunability of 20 GHz and 15 GHz, respectively. When stretched, the 1st and 2nd order magnetic resonances show the tunability of 12 GHz and 10 GHz, respectively. In the meantime, there are accompanying changes in transmittance at the resonances. The ZrO2/VO2/PDMS all-dielectric metamaterial presented in this work provides an alternative strategy for developing actively tunable, flexible, and versatile THz devices. In addition, it has the merits of simple preparation and low cost, promising large-area and rapid preparation of meta-arrays.

For high-dimensional closed quantum systems, this paper proposes a novel quantum Lyapunov control scheme based on the particle swarm optimization algorithm and achieves a high-probability population transfer of the system to a non-isolated target eigenstate in the LaSalle invariant set under usual smooth Lyapunov control laws. Via a quadratic Lyapunov function with unknown parameters, a control law with the unknown parameters is designed; based on the LaSalle invariance principle and the energy-level connectivity graph, the stability of the system is analyzed; by using the particle swarm optimization algorithm, a set of optimal parameters is obtained to achieve the control goal. In particular, we propose a path planning method based on the energy-level connectivity graph to determine the initial values of the unknown parameters, which is such that the optimization algorithm can efficiently and conveniently find a set of optimal solutions of the unknown parameters. Numerical simulation experiments on a five-level quantum system and a three-qubit system demonstrate that the proposed Lyapunov control scheme based on the particle swarm optimization algorithm has a good control effect.

Effect of Ti Content on the wetting behavior and chemical reaction in AgCuTi/SiO2 system are studied. The results show that small additions of Ti in AgCu braze alloys can decrease the final contact angle θF, but the Ti content increases from 2.0 wt % to 7.8 wt %, the contact angle θ changes little. The additions of Ti in AgCu can obviously increase the work of adhesion, as Ti content increase to 2.0 wt %, 4.0 wt % and 7.8 wt %, the increased work of adhesion is 1080 mJm−2 (ΔW1), 1083 mJm−2 (ΔW2) and 1083 mJm−2 (ΔW3), respectively. However，the little changes of the increased work of adhesion for enhancing Ti content in braze alloys are responsible for the tiny change of the final contact angle θF. The results also show that as the Ti content increases, the microstructures in the wetting drop zone change. As the Ti content increases to (4.0, 7.8) wt. %, Ti5Si3 compounds are formed in the wetting drop, which decrease the activity of Ti leading to the little change in spread rate.

Selective laser melting (SLM) technique, based on a layer-by-layer production, was used to produce biomedical Co-Cr devices specifically developed for dental restoration applications. However, information on the metal-ceramic bond strength of SLM-manufactured parts was limited. In this study, SLM-fabricated Co-Cr alloy specimens were subjected to subsequent heat treatments (holding at 1150 °C for 1 h). The alloy microstructures were characterized by scanning electron microscopy (SEM) coupled with energy-dispersive x-ray spectroscopy (EDX), x-ray diffractometer (XRD), and transmission electron microscopy, whereas the bond properties were evaluated by 3-point bend tests and coefficient of thermal expansion (CTE) tests, as compared to casting (CAST) alloys. Results showed that SLM specimens exhibited fine grains and homogeneously dispersed intermetallic compounds, and the resultant XRD analysis revealed a predominated face-centered cubic γ-Co phase (72 %). Student's t-test demonstrated that bond strengths of SLM specimens (45.80 ± 1.91 MPa) were significantly lower than that of CAST specimens (54.05 ± 6.77 MPa) (P 25MPa specified in ISO9693).

The forces exerted on teeth and prostheses during mastication are repeated and dynamic, resulting in fatigue damage to dental prostheses. Most fractures of dental restorations are fatigue failure. The 4-point bend fatigue behavior of Co-Cr-Mo-W alloys manufactured by investment casting (CAST) and selective laser melting (SLM) has received little attention.The purpose of this in vitro study was to evaluate the 4-point bend fatigue property of dental Co-Cr alloys and determine the relationship between microstructure and the 4-point bend fatigue property of Co-Cr alloys created by traditional casting and SLM. These can guide the use of Co-Cr alloy in dentistry.Co-Cr-Mo-W alloys were fabricated with a dimension of 45×2×2 mm by investment casting and SLM. The 3-point bend test measured the ultimate bend strength with 3 specimens in each group. The 4-point bend fatigue test evaluated the fatigue life under various stresses, with 6 specimens in each group. The specimens were mechanically ground, polished, and electrochemically etched. Scanning electron microscopy was used to identify the microstructures of both etched specimens and fracture surfaces. X-ray diffraction investigations were used to determine the phases. Significant differences in the bend strength were analyzed by using the independent samples t test (α=.05), and the fatigue test was analyzed with ANCOVA (α=.05).The mean ±standard deviation bend strength of SLM specimens was 1837 ±3 MPa, higher than the 1200 ±6 MPa for CAST specimens (P.05). The maximum bend stress of the SLM specimens without fatigue failure was 735 MPa, which was statistically higher than the 394 MPa for CAST specimens (P.05). The microstructure characteristics of the SLM alloy contributed to its excellent fatigue performance. In SLM alloy, the γ phase constituted the majority with some ε and Laves phases, while the cast alloy possessed higher ε and Laves phases. The grains of SLM alloy were equiaxed and fine, and the second phases were fine and dispersive. In contrast, the cast alloy possessed clear dendrites, and the second phases were sizable.The SLM dental Co-Cr-Mo-W alloy had statistically better 4-point bend fatigue properties than cast alloy, which was associated with an improved microstructure.

Structural deterioration and low conductivity are key factors that give rise to severe capacity fading of transition metal oxides as anodes for lithium-ion batteries (LIBs). An effective way to overcome this challenge is to construct nanosized metal oxide heterostructures integrated with a 3D nanoarchitectured metal matrix to buffer volume variation, reinforce structural stability and improve electronic conductivity. Herein, a facile and effective underpotential oxidation (UPO) assisted dealloying protocol has been developed successfully to synthesize freestanding monolithic 3D nanoporous copper@1D cuprous oxide nanowire network (3D NPC@1D Cu2O NWN) heterostructures. Based on their dealloying behavior, the evolution law can be well established, sequentially described as “dealloying of (Mn, Cu) accompanying Cu2O NW germination”, “growth of Cu2O NWs accompanying (Mn, Cu) re-dealloying” and “Cu2O NWN coarsening”. Compared to other CuxO-based electrode materials with different structural designs reported in the literature, the unique nanocomposites as an anode for LIBs exhibit far superior Li storage performance including an ultrahigh initial reversible capacity of 2.71 mA h cm−2, good cycling stability with 60.2% capacity retention after 150 cycles (just 0.007 mA h per cm2 per cycle for capacity fading), and excellent rate capability with reversible capacity as high as 1.64 mA h cm−2 after 55 high-rate cycles. This mainly originates from effectively accommodating huge volume changes during charge/discharge processes, providing abundant reaction active sites, shortening electron/ion transport paths, and building a reliable 3D/1D composite nano-configuration without additional binders and conductive agents, indicative of a considerably promising anode candidate for high-performance LIBs.

Vacuum brazing of FeCrMo damping alloy is carried out by using Mn Ni Cu Cr Co brazing filler at 1080 °C for different times (5, 15, 30, 60, and 120 min). The results reveal that the joint's interfacial microstructure brazed for 15 min consists of three zones: the FeCrMo substrate, Fe solid solution layer, and a brazing seam consisting of a (Mn, Ni) solid solution. Kirkendall vacancies are observed in the brazing seam when the joint is brazed for 120 min, due to the fact that Fe diffuses more quickly than Ni, Cu, and Mn. The specimen manifests the most optimal damping capacity when brazed for 60 min, and its lap-shear strength still reaches 426.7 MPa. The detailed mechanisms behind the formation of different phases across the brazed joint and their correlations with joint strength and damping capacity are also discussed.

In this paper, novel three dimensional hierarchical porous Sn-Ni (3D-HP Sn-Ni) alloys were investigated as a promising anode for high-performance Li ion batteries (LIBs), which was fabricated by pulse electrodeposition of mesoporous Sn-Ni alloy made of ultrafine nanoparticles on the 3D nanoporous copper substrate from chemical dealloying of as-cast Al55Cu45 (at.%) alloy slices in the HCl solution. The results show that the as-obtained 3D-HP Sn-Ni alloys are typically characteristic of open, bicontinuous, interpenetrating bimodal pore size distribution comprising large-sized (hundreds of nm) ligament-channel network architecture with highly porous channel walls (several nm). Compared to the two dimensional nanoporous Sn-Ni (2D-NP Sn-Ni) thin films, the 3D-HP Sn-Ni alloys as anode for LIBs show superior cycling stability with reversible specific capacity of 0.25 mAh cm−2 and coulombic efficiency of more than 95% up to 200 cycles. Moreover, the reversible capacity as high as 0.22 mAh cm−2 can be achieved even after a series of high-rate charge–discharge cyclings. The satisfactory electrochemical properties can be mainly ascribed to the unique 3D hierarchical porous structure, large contact surface area between active material and electrolyte, as well as good buffer effect of inactive component, which is greatly beneficial to alleviate the huge volume variation, enhance the loading mass of active material, shorten the Li+ migration distance and improve the electron conductivity. We believe that this present work can provide a promising anode candidate towards practical application of high-performance LIBs.

The wetting characteristics of braze alloys (AgCu eutectic and AgCu eutectic −2 wt% Ti) on SiO2 substrate are observed and the results show that small percentage additions of Ti into the AgCu eutectic alloy leads to a dramatic decrease in the steady contact angle. The interfacial microstructures are responsible for the steady contact angle decreasing of different braze alloys on the SiO2 substrate. The aim of this work is to investigate the interfacial microstructures formation mechanism between SiO2 substrate and AgCuTi braze alloys. Scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectroscopy (EDS) and high-resolution transmission electron microscopy (HRTEM) were employed to analyze the interfacial microstructures. The results show that the molten AgCuTi alloy infiltrates into the SiO2 side, resulting in the formation of SiO2/Ti2O/(Ti4Cu2O+AgCu)/AgCu/(AgCu+Ti5Si3) structures. The Ti atoms in the molten braze alloy firstly accumulated along the surface of SiO2 and then reacted with SiO2 to form the Ti2O layer, at the same time, Si liberated from thermal degradation of SiO2 dissolved into the molten AgCuTi solution and reacted with Ti to form Ti5Si3 compounds. Ti-Cu rich in the molten AgCuTi would react with Ti2O at the interface to form the Ti4Cu2O M6X compounds. Both the experiment results and the theoretical thermodynamics analysis support the proposed viewpoint of interfacial microstructures formation mechanism between the SiO2 substrate and AgCuTi braze alloys.

Limited information is available regarding the microstructures and mechanical properties of Co-Cr dental alloys prepared using conventional casting (CAST), computer numerical control (CNC) milling, and selective laser melting (SLM).The purpose of this in vitro study was to evaluate the mechanical properties and microstructures of Co-Cr dental alloys fabricated using conventional casting, computer numerical control milling, and selective laser melting and to estimate the potential of applying the SLM technique in prosthetic dentistry.Each group (n=6) of 50-mm-long Co-Cr alloy, dumbbell-shaped specimens was fabricated using the CAST, CNC, and SLM techniques. For each technique, the corresponding commercial alloy material was used. The mechanical properties were evaluated using a tensile test according to International Organization for Standardization (ISO) standard 6892, including 0.2% yield strength, ultimate tensile strength, elongation, and fracture analysis. The microstructures of the specimens were evaluated by using metallurgical microscopy, X-ray diffraction (XRD), and scanning electron microscopy. The Tukey honest significant difference test (α=.05) was used to statistically analyze the 0.2% yield strength, ultimate tensile strength, and microhardness values.The microstructures of the SLM specimens exhibited homogeneously distributed fine grains, dispersed second-phase particles, and few defects, and the XRD results showed the α-Co phase predominated, with minimal ε-Co phase and no harmful needle σ phase in the SLM group. The mean ±standard deviation of the 0.2% yield strength of the SLM specimens was 790 ±11 MPa, and the ultimate tensile strength was 1072 ±18 MPa. These values exceeded those of the CAST and CNC specimens by approximately 50% (P.05). The SLM group showed the highest microhardness (475.3 ±10.2 HV10), followed by the CNC (325.2 ±17.8 HV10) and CAST group (323.7 ±27.2 HV10). Additionally, the ductility and toughness of the SLM specimens were also better than those of the other 2 groups. No significant differences were found in the mechanical performance between the CNC and CAST specimens (P.05).The microstructures and mechanical properties of Co-Cr dental alloys were dependent on the fabrication techniques. The SLM specimens exhibited better microstructures and mechanical properties than those fabricated with CNC or CAST.

Numerous studies confirm that three dimensional porous Cu–Sn (3DP Cu–Sn) anode possesses good application prospect in light of its desirable electrochemical performance on lithium ion half cells, but there are a few related systematic researches on lithium ion full cells until now, which is indispensable before its commercialization. Herein, the effects of galvanostatic charge-discharge voltage range on the cycling stability of 3DP Cu–Sn anode for lithium ion full cells are investigated systematically. The results show that the suitable charge-discharge voltage range plays a key role in improving the reversible capacity and cycling stability of the 3DP Cu–Sn||LiCoO2 full cell, which is closely related to maintaining the electrode structure stable by controlling the amount of Li+ extracted and inserted. Especially, in the voltage range of 1.2–3.9 ​V, the full cell exhibits remarkably improved electrochemical properties with the high initial reversible capacity of 2.71 ​mAh cm−2 and 71.95% capacity retention upon 80 cycles. We believe that this work can provide a significant reference for the practical application of porous Sn-based anodes.

Sapphire was metallized by magnetron sputtering Ti-Cu bilayer films on the surface and was brazed to Kovar alloy (Fe-Ni-Co) using Ag-Cu eutectic alloy. The microstructures of these joints were investigated. The correlation between the Al2O3/Kovar joining strength and the microstructures of the braze joints was discussed. The results show that Ni atoms in Kovar alloy diffused towards the Ti-Cu metallizaton layer and remained as (Ni, Cu) solution during the solidification process. The metallization layer became thicker and evolved into a reaction layer which consisted of (Ni, Cu) solution, Cu-Ti-O and TiO. This reaction layer in the joint played an important role in relieving residual stress. Thus the maximal tensile strength of 72.6 ± 4.4 MPa was achieved. However, as the holding time was further prolonged, Ni atoms diffused through the (Ni, Cu) solid solution into the reaction layer resulting in formation of Ni3Ti intermetallic compounds and transformation of TiO to Ti2O3, which leads to the joint strength decreasing.

In this report, a simple and effective low-temperature synthesis route has been proposed to smoothly achieve monodisperse tin nanoparticles upon monolithic 3D nanoporous copper (3D-NPC@MTNPs) from chemical dealloying of as-cast Al–45 at% Cu alloy sheets in HCl solution; they exhibit superior Li storage properties and ultralong cycle life as the anode for lithium ion batteries (LIBs). The results show that the 3D-NPC@MTNPs composite can be fabricated on a large scale by electroless plating of Sn on a uniform NPC matrix with a pore size of ca. 200 nm in an acidic plating bath below room temperature. Compared to two dimensional copper foil supported tin thin films (2D-CF@TTFs), the 3D-NPC@MTNPs electrode displays a markedly higher first reversible capacity of 0.485 mA h cm−2 as well as superior cycling stability with 52.4% capacity retention and over 96.7% coulombic efficiency after 500 cycles. This can be largely ascribed to the synergistic effect between the favorable monodispersity of Sn nanoparticles with ultrafine particle size and single crystal nature and the unique 3D nanoporous electrode architecture with a large specific surface area and a good mass transfer channel, which facilitates the accommodation of mechanical strain, improvement of structural stability, enhancement of bonding force, and acceleration of mass transfer, which are indicative of a quite promising candidate as a high-performance anode for LIBs.

Dynamic tracking of nanoparticles in cells faces a big challenge due to fluorescence quenching. Here, the pH-switchable probe spiropyran (SP) was introduced into poly(ethylene glycol) (PEG) via atom transfer radical polymerization (ATRP) to construct expected "off-on" fluorescent nanoparticles. Strong red fluorescence was emitted to efficiently track nanoparticles in cells due to the isomerization of spiropyran to merocyanine in the endosome or lysosome.