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Refilled friction stir spot welding of aluminum alloy to galvanized and uncoated steel was conducted, and the microstructure and the corrosion behavior of joints were investigated. Al5FeSi phases distributed in TMAZ and broke during tool stirring in NZ, which induced the pitting corrosion in 3.5 wt% NaCl solution. The maximum corrosion depth of ST-Al/ST06 Z joint was up to 21.3 μm at the mixed layer, which was 2.8 μm deeper than that of ST-Al/ST16 joint at the interface between aluminum alloy and steel. Zn and Mg segregated at the grain boundaries of the mixed layer, resulting in serious intergranular corrosion. The corrosion current density of ST-Al/ST06 Z joint ((8.1 ± 0.2) × 10–6 A/cm−2) is higher than that of ST-Al/ST16 joint ((7.9 ± 0.4) × 10–6 A/cm−2) after immersion for 1 h in 3.5 wt% NaCl solution. The corrosion current densities of samples were minimum for 6 h immersion time, which was related to the passivation films and corrosion products formed on the joint surface.

Materials with a room-temperature phosphorescence (RTP) property have wide application fields. For practical applications, it is highly desirable that only a small amount of RTP phosphors was attac...

This paper introduces an analytical approach to optimize the textured bearing with cavitation to improve the load support. For this purpose, a grooved parallel slider bearing is analyzed based on the Reynolds equation and mass conservation equation, adopting the cavitation model used in the inlet suction mechanism. In order to clarify the effect of cavitation, the pressure distributions of the bearing in the three possible cases determined by whether cavitation occurs are analyzed and compared. It is found that the bearing obtains the largest load support in the case that the lowest pressure just reaches the cavitation pressure. Considering this condition, the analytical solutions of the optimal geometric parameters in the bearing with single groove are finally obtained. The results calculated by FLUENT are also consistent with the analytical solutions. The analytical solutions above are extended to the bearing with multiple grooves and reciprocating bearing. The results suggest that the bearing with only one flat wide groove and the bearing with larger textures under slower speed and higher inlet pressure have better load support.

Aluminum alloy and steel hybrid structures offer clear advantages in weight reduction and energy conservation for the automotive industry. This paper exhibits sound refilled friction stir spot welded joints between the aluminum alloy and ST16 steel sheets with the maximum tensile/shear and cross-tension fracture loads of 3745 N and 1073 N, respectively. All samples failed through the interface of aluminum alloy/steel joints during tensile/shear test and cross-tension test. The microstructure and fracture mode of the joints were studied with the scanning electron microscope, electro-probe microanalyzer and X-ray diffraction. For the joints where the sleeve had not plunged into the ST16 steel, the effect of the sleeve plunging depth and rotation speed on the tensile/shear fracture load cannot be identified, as an intermetallic compounds layer formed between Al and Fe, which was almost uniform across the interface. The mechanical performance of joints increased dramatically when the sleeve plunged into the ST16 steel because of metallurgical bonding and mechanical interlocking in the sleeve-affected zone. However, this process caused considerable wear to the tool and shortened its service life. The bonding mechanism was investigated by studying joints between the aluminum alloy and galvanized steel for the same welding parameters.

The isostructural and isoelectronic transition-metal-dichalcogenides 1T-TaS2 and 1T-TaSe2 are layered materials with intricate electronic structures. Combining the molecular beam epitaxy growth, scanning tunneling microscopy measurements and first-principles calculations, we prepare monolayer 1T-TaS2 and TaSe2 and explore their electronic structures at the atomic scale. Both two-dimensional (2D) compounds exhibit commensurate charge density wave phase at low temperature. The conductance mapping identifies the contributions from different Ta atoms to the local density of states with spatial and energy resolution. Both 1T-TaS2 and 1T-TaSe2 monolayer are shown to be insulators, while the former has a Mott gap and the latter is a regular band insulator.

An analytical approach is advantageous in providing a more generic in-depth understanding of the nature of the relationships among texture parameters. Considering the corresponding variation of film thickness, the effects of operating parameters on the optimal texture geometric parameters are clarified analytically, with a trial algorithm adopted to overcome the difficulty of direct analysis. The interaction and cooperation between the parameters are highlighted. The relationship between film thickness (or load support) and friction resistance is also analyzed, and series of pin-on-disk tests are performed to assess the results from the analytical approach. Three laser-etched rectangular textures with different sizes are tested for friction coefficients, under a range of applied loads and speeds. Both analytical and experimental results show that the optimal dimple breadth and depth decrease with the increase of load, and the optimal dimple depth increases with the increase of sliding speed.

Columnar jointed rock mass (CJRM) has a special joint structure formed during the cooling of lava. The self-oriented joint structure can induce mechanical anisotropy of the rock mass, whic...

Since the discovery of high temperature superconductivity in cuprates, Josephson junction based phase-sensitive experiments are believed and used to provide the most convincing evidence for determining the pairing symmetry. Regardless of different junction materials and geometries used, quantum tunneling involved in these experiments is essentially a nanoscale process, and thus, actual experimental results are extremely sensitive to atomic details of the junction structures. The situation has led to controversial results as to the nature of the pairing symmetry of cuprates: while in-plane junction experiments generally support $d$-wave pairing symmetry, those based on out-of-plane ($c$-axis) Josephson junctions between two rotated cuprate blocks favor $s$-wave pairing. In this work, we revisit the $c$-axis experiment by fabricating Josephson junctions with atomic-level control in their interface structure. We fabricate over 90 junctions of ultrathin Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ (BSCCO) flakes by state-of-the-art exfoliation technique and obtain atomically flat junction interfaces in the whole junction regions as characterized by high resolution transmission electron microscopy (TEM). Notably, the resultant uniform junctions at various twist angles all exhibit a single tunneling branch behavior, suggesting that only the first half a unit cell on both sides of the twisted flakes is involved in Josephson tunneling process. With such well-defined geometry/structure and the characteristic single tunneling branch, we repeatedly observe Josephson tunneling at a nominal twist angle of 45 degrees, which is against the expectation from a purely $d$-wave pairing scenario. Our results strongly favor the scenario of a persistent $s$-wave order parameter in the junction.

Purpose The shapes of surface textures have been designed to control the leakage of mechanical seals in recent years. The purpose of this paper is to demonstrate the influence of geometric properties of elliptical dimples on the leakage rate. Design/methodology/approach A new geometric feature point is expressed using an analytical solution to locate the high-pressure zones. Furthermore, a numerical model of the three-dimensional flow field for the mechanical seal with elliptical dimples is developed using ANSYS Fluent to demonstrate the influencing mechanism. Findings The location of the proposed geometric converging point coincides with the maximum pressure point under different orientation angles. An inward flow on the leakage section observed from the simulation results is responsible for decreasing the leakage rate. Originality/value The influencing mechanism of the elliptical dimple on the leakage rate is demonstrated, which can facilitate the design of surface textures.

Recently, intrinsically photoluminescent polymers (IPPs) without any conventional chromophores have aroused increasing attention and been extensively investigated. Simple and green synthetic method is definitely preferred for the production of such polymer. In this work, intrinsically photoluminescent hyperbranched polyethylenimine (IP-HPEI) was facilely prepared through directly heating the viscous neat HPEI under air. Since none of solvents, organic modifiers, purification and pressure vessel is required, it can be claimed that this is a simpler and greener method to prepare IPPs in comparison with other reports. Moreover, this simple technique favors the large scale preparation of IP-HPEIs. 1H NMR, FTIR, XPS, TGA and fluorescence characterizations supported that air oxidation led to the generation of luminogens in HPEIs and tertiary amine oxides were the real luminogens, not the oximes reported by others. At pH 6, IP-HPEI could be used as fluorescent sensor to selectively detect Cu2+ ions with an LOD value of 0.72 μM.

Iron selenide (FeSe) is an iron-based superconductor which shows unique properties, including strongly anisotropic superconducting gap, paramagnetism in undoped compound and extremely small Fermi pocket size. In this work, we demonstrate that the sizes of electron and hole pockets in FeSe monolayer become much smaller than those in bulk. The Fermi energy is in the order of a few meV and can be fine-tuned by the thickness of graphene layers underneath. Despite the low carrier density, the FeSe monolayers grown on trilayer or multi-layer graphene are superconducting. The superconducting gap size is sensitive to the Fermi energy of the hole band. Remarkably, the FeSe monolayer provides the opportunity to study the physics in the crossover regime where the Fermi energy and superconducting gap are comparable to each other.

The interaction between cracks, as well as their propagation, in single-crystal aluminum was simulated at the atomic scale by molecular dynamics method and modified embedded atom method. Further, the effects of the distance between two cracks and the difference of crack size on crack propagation and mechanical properties were comprehensively investigated. The results demonstrated that multi-crack propagation in aluminum is a quite complex process, which is accompanied by micro-crack growth, merging, stress shielding, and the crossing of slip bands. During crack propagation, there are interactions between cracks. Such interactions inhibit the phase transition, dislocation and slip bands at the crack tip, and also affect the direction of crack propagation. The intensity of the interaction between two cracks decreases with the increase of the distance between them and increases with increasing crack size. Moreover, the strength limit of aluminum decreases with the increase of the distance between cracks and the difference in their size.

Butt joining of Al-Mg-Si alloys with 6.0 mm in thickness was made with conventional rotational shoulder friction stir welding (RSFSW) and non-rotational shoulder friction stir welding (NRS-FSW) process, respectively, and the resultant mechanism of different shoulders affecting the microstructure and mechanical properties of joint was discussed. A new zone named “triangle zone” (TZ) in the RSFSWed joint was first clearly defined, while the shoulder and pin affected zone (SPAZ) did not exist in the NRS-FSWed joint. The distribution of average grain sizes in each zone of the joints (“M” shape) and the changes in the proportion of high angle grain boundaries (HAGBs) (“W” shape) are unified with the typical “W” shape distribution of microhardness in the joints. Compared to rotational shoulder, the non-rotational shoulder significantly reduced the width of softened area. In particular, the microstructure of the joints by NRS-FSW with triple facets on the pin surface is finer, denser and more homogeneous. The tensile strength coefficient of the joint welded by NRS-FSW and NRS-FSW with the pin of triple facets increased by 2.3% and 11.6%, respectively, compared to the joint welded by RSFSW. Accordingly, the fatigue performances increased by 1.72 times and 3.19 times, respectively.

Amygdaloidal basalt is a typical rock mass in the dam foundation of the Baihetan hydropower project in southwest China. With rising and drawdown of the reservoir water level, the permeability and creep deformation characteristics of the amygdaloidal basalt are much complicated in the long-term cyclic loading processes. A cyclic loading-unloading creep test on the amygdaloidal basalt was performed to evaluate its deformation and permeability behavior. The results showed that Poisson’s ratio and elastic modulus of the rock specimen varied significantly under different loading processes with a relatively large irreversible deformation. The permeability and strain rates of rock changed in two phases under lower deviatoric stresses, while there are three typical stages of strain growth with the final stress level of 121.8 MPa. For axial stress of 128 MPa, the creep deformation and creep rate in the axial direction are smaller than these in the lateral direction. Before the sample failure, the lateral deformation accelerates earlier than the axial deformation. The results also suggested that the permeability of the rock specimens decreases considerably during each loading process and then tends to be constant with time. No apparent change in steady permeability is observed with variation of stress. For 128 MPa axial stress, the permeability first decreases, then tends to be in a stable value, and at last increases during the sample failure.

Photoluminescent nanomaterials with a high quantum yield (QY) is preferred in many applications. Up to the present date, only a few organo-soluble Au-Ag bimetallic nanoclusters (NCs) have ever reported to exhibit a QY of more than 20%. Herein, ultrabright Au-Ag NCs with a maximum QY of ca. 23.6% were synthesized with the assistance of mercaptosuccinic acid (MSA) and poly(N-vinylimidazole) (PVIm) through a two-step green route, which was almost two-fold higher than the corresponding mono-metallic Au NCs. Moreover, the as-prepared Au-Ag NCs had similar high QY both in solution and in solid state, which widened its potential applications from solution to solid form. The existence of Au0, Ag+ and Ag0 in the formed Au-Ag NCs was demonstrated by XPS. DLS showed that the PVIm and MSA stabilized Au-Ag NCs were still nanogel, just like its Au NCs precursor. Synergistic fluorescence enhancement effect existed with the Ag/Au ratio in the range of 0.1–0.4. Au-Ag NCs emitted strongest when Ag/Au ratio was between 0.2 (Au-Ag0.2) and 0.3 (Au-Ag0.3). Au-Ag0.2 exhibited mainly phosphorescent emission falling in the far-red/near infrared region (centered at ca. 718 nm). The phosphorescent property was supported by the marked large Stokes shift (> 400 nm) and two microsecond magnitude long life times (τ1 = 0.30 μs and τ2 = 6.65 μs). The λem,max of Au-Ag NCs could be modulated to ca. 666 nm when keeping a higher Ag/Au ratio in the Au-Ag NCs, but a side effect of PL depression was accompanied. Compared with the corresponding mono-metallic Au NCs, besides the stronger emission, Au-Ag NCs still had the following characters: (1) more stable during the shelf-storage; (2) selective probing for cysteine having a limit of detection value of 2.5 μM.

Microstructure, mechanical properties and stress corrosion behavior of friction stir welded (FSWed) Al–Mg–Si alloy were investigated. The average grain sizes of shoulder-affected zone (SAZ), nugget zone (NZ), heat-affected zone (HAZ) and base material (BM) are 6.03, 4.80, 168.30 and 127.24 μm, respectively. The thermo-mechanically affected zone (TMAZ), which is generated on the edge position between HAZ and weld nugget zone, has a narrow width of 400 μm. The ultimate tensile strength (UTS) of FSWed joint is 232.20 MPa, about 91.04% with respect to that of base material of 255.06 MPa, and the joint fracture occurs at HAZ on advancing side (AS). The FSWed joint is more susceptive to stress corrosion cracking (SCC) than base material, and the SCC susceptibility increases with the rise in temperature. The residual UTS of FSWed joints in constant loaded tests at the load levels of 90, 105 and 120 MPa is 89.97%, 67.50% and 54.75% of the UST of FSWed joint in air, respectively. The increase of the load in constant loaded tests and four-point beam-bent tests accelerates the SCC of FSWed joints.

We report the growth and characterization of atomically thick NbS2, TaS2, and FeS films on a 6H-SiC(0001) substrate terminated with monolayer or bilayer epitaxial graphene. The crystal and electronic structures are studied by scanning tunneling microscopy and reflection high-energy electron diffraction. The NbS2 monolayer is solely in the 2H structure, while the TaS2 monolayer contains both 1T and 2H structures. Charge-density waves are observed in all phases. For the FeS films, the tetragonal structure coexists with the hexagonal one and no superconductivity is observed.

Atomistic simulations with interatomic potentials can provide insights into the cracking and failure of structural ferritic steels. Unfortunately, the evaluation of the simulation results often suffers from the uncertainties due to the quality and behavior of the employed interatomic potential. In this work, the molecular dynamics (MD) method has been used to simulate and to analyze the deformation and propagation of crack tips in α-iron. The influence of different types of potentials that we adopt on the crack propagation simulation is discussed. State of art M07, M20, and B20 potentials are considered. Overall, the microscopic deformation mechanism by the MD simulation with different types of potentials are similar, which dislocations are emitted from the crack tip, and twinning or martensite transformation happen. However, with a careful contradistinction, different mechanical responses are investigated. The relationship between the cracking mechanism and the intrinsic properties of α-iron, such as stacking fault energies, has also been discussed.

Correction coil support (CCS) thermal shield (TS) is a key component in the ITER magnet that supports and serves to interrupt the heat from toroidal field case (TFC) to the correction coil superconductor. In this paper, a feasible fabrication design for the CCS TS is presented which is accomplished by 3 kinds of jointing processes (vacuum brazing, friction stir weld, and tungsten inert gas weld). The finite element analysis (FEM) is employed to speculate whether there is any interaction between different jointing processes. Based on the fabricating design, a prototype CCS TS is fabricated based on the fabricating design. Subsequently, the qualification test is carried out to characterize the property of the joints. The macro metallographic shows that the braze ratio of the as-brazed joint is 100%, and no crack or defect is observed in all the joints. The OM and EBSD results illustrate that the Ag-6%Cu eutectic phase penetrates along the crystal grain boundary of the copper. The dynamic re-crystallization behavior of friction stir weld (FSW) joint is demonstrated by EBSD observation. The tensile test shows that the shear strength of the SS/Cu joint is 205MPa, and the fracture strength of Cu/Cu FSW joint is 212MPa. The leakage rate of the CCS TS sealing with the 3MPa He is lower than 4×10−10 Pa*m3/s. Based on the above work, the fabrication plan is feasible and can be utilized in the manufacturing of ITER CCS TS.

GdTe3 is a layered antiferromagnetic (AFM) metal with charge density wave (CDW). We grew monolayer (ML) GdTe3 on graphene/6H-SiC(0001) substrates by molecular beam epitaxy. The electronic and magnetic structures are studied by scanning tunneling microscopy/spectroscopy, quasi-particle interference (QPI) and first-principles calculations. Strong evidence of CDW persisting at the two-dimensional (2D) limit is found. Band dispersions and partially gapped energy bands near the Fermi surface are revealed by the QPI patterns. By density functional theory +U calculations, AFM order with stripe pattern is found to be the magnetic ground state for ML GdTe3. These results provide fundamental understanding and pave the way for further investigation of GdTe3 at the 2D limit.

Ultra-thin topological insulators provide a platform of realizing many exotic phenomena such a Quantum spin Hall effect, Quantum anomalous Hall effect, etc. These effects or states are characterized by quantized transport behavior of edge states. Experimentally, although these states have been realized in various systems, the temperature for the edge states to be the dominating channel in transport is extremely low, contrary to the fact that the bulk gap is usually in the order of a few tens of milli-electron volts. There must be other in-gap conduction channels that won't freeze out till a much low temperature. Here we grow ultra-thin topological insulator Bi2Te3 and Sb2Te3 films by molecular beam epitaxy and investigate the structures of domain boundaries in these films. By scanning tunneling microscopy and spectroscopy we find that the domain boundaries with large rotation angles have pronounced in-gap bound states, through which one dimensional conduction channels are suggested to form as visualized by spatially resolved spectroscopy. Our work indicates the critical role played by domain boundaries in degrading the transport properties., 10 pages, 4 figures

A series of hyperbranched graft copolymers with hyperbranched polyethylenimine (HPEI) as core and hyperbranched polyglycerol (HPG) as shell (HPEI-g-HPG) were used as nanoreactors and stabilizers for the synthesis of CdS quantum dots (QDs). The preparation conditions were optimized to obtain CdS QDs with a stronger fluorescence. Stable CdS QDs could be prepared by using HPEI-g-HPGs or HPEI homopolymer, but not HPG homopolymer. The CdS QDs capped by HPEI-g-HPGs emitted stronger than those capped by HPEI. Moreover, the photoluminescence intensity increased pronouncedly with increasing the HPG shell content of HPEI-g-HPG stabilizer. The measurements of UV–vis spectroscopy, transmission electron microscopy and dynamic light scattering further verified the formation of CdS QDs. Compared with the CdS QDs capped by HPEI, those capped by HPEI-g-HPGs showed a better storing stability in solution at 4 °C. The as-prepared CdS QDs were only stable in the pH range of 7.0–9.0. It was found that increasing the HPG shell content of HPEI-g-HPG stabilizer could effectively raise the selectivity of the as-prepared CdS QDs towards Hg2+. As the ratiometric fluorescence sensors, CdS QDs capped by HPEI-g-HPGs were most sensitive to Hg2+ and the limit of detection was ca. 1.5 × 10−8 M.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have a range of unique physics properties and could be used in the development of electronics, photonics, spintronics and quantum computing devices. The mechanical exfoliation technique of micro-size TMD flakes has attracted particular interest due to its simplicity and cost effectiveness. However, for most applications, large area and high quality films are preferred. Furthermore, when the thickness of crystalline films is down to the 2D limit (monolayer), exotic properties can be expected due to the quantum confinement and symmetry breaking. In this paper, we have successfully prepared macro-size atomically flat monolayer NbSe2 films on bilayer graphene terminated surface of 6H-SiC(0001) substrates by molecular beam epitaxy (MBE) method. The films exhibit an onset superconducting critical transition temperature above 6 K, 2 times higher than that of mechanical exfoliated NbSe2 flakes. Simultaneously, the transport measurements at high magnetic fields reveal that the parallel characteristic field Bc// is at least 4.5 times higher than the paramagnetic limiting field, consistent with Zeeman-protected Ising superconductivity mechanism. Besides, by ultralow temperature electrical transport measurements, the monolayer NbSe2 film shows the signature of quantum Griffiths singularity when approaching the zero-temperature quantum critical point.

Optically active and inactive hyperbranched polymers with specific thermoresponsive behaviours in water were reported. Through two steps hyperbranched polyethylenimine (HPEI) polymers terminated with different amount of D-phenylalanine (D-Phe), L-phenylalanine (L-Phe) or DL-phenylalanine (DL-Phe) were prepared and characterized. The analyses on the solution properties by turbidimetry, dynamic light scattering, fluorescence probe and 1H-NMR demonstrated that all the polymers exhibited specific thermoresponsive behaviours in water, including: (1) In the dilute polymer concentration region, increasing the polymer concentration led to the increase of phase transition temperature; (2) The optically inactive thermoresponsive hyperbranched polymers showed a higher cloud-point temperature (T cp) than their corresponding optically active ones in a relatively higher polymer concentration; (3) At the same polymer concentration the hydrophobic groups of the optically inactive HPEI-DL-Phe formed more perfect hydrophobic domain than those of the optically active HPEI-L-Phe and HPEI-D-Phe.

Al2O3-Fe based metal ceramic is a functional ceramic material prepared by high temperature sintering with Al2O3 as the main component, plus iron powder (binder phase) and other additives. In this paper, the composition design of Al2O3-Fe based metal ceramic was made, and the performance of the material was tested and studied. The change of the content of iron powder also has a great influence on the compressive strength and bending strength of the Al2O3 metal ceramic. Experiments also show that the Al2O3-Fe-based cermet has good corrosion resistance. Finally, the following conclusions were obtained through the comprehensive analysis: the best test formula is No.4 sample, and its compressive strength is 79.79MPa, bending strength is 15.90 MPa, corrosion resistance rate is 0.028 g/dm2·h.

Static three-point bending test of the laser welded Web-core steel sandwich panel was performed. The deformation and failure of the sandwich panel with narrow weld width T-Joints were investigated. The results indicate that the deformation undertakes the following three stages: elastic deformation, plasticity deformation and T-joints cracking. The initial yield load is 25 kN, The maximum bending load is 54 kN. The high strength rate characteristic not be fully reflected. The finite simulation result shows the whole structure has no chance to reach the designed maximum value when the T-joints formed plasticity rings. Then the plastic region was developing till the weld cracked. We considered that the T-joint’s cracking is a new failure mode for the web-core steel sandwich panel. Thus, the laser welded T-joints with narrow weld width are the weakest location for the total structure. It is very necessary to consider the T-joint’s geometrical and mechanical properties for the total structural design.

Molecular beam epitaxy (MBE) is a powerful technique to grow high quality thin films with atomic precision, and multiprobe scanning tunneling potentiometry (STP) is an ideal tool to probe electronic transportation in nanometer scale. We combine the two advanced techniques together and successfully construct a unique system of MBE, STP, and four-probe in situ transport measurement. Excellent functions of this system have been demonstrated by experiments on several materials under ultrahigh vacuum conditions. The system provides an ideal platform for in situ study of electronic transport properties of various thin films, such as two-dimensional superconductors and topological insulators.

SnTe hosts ferroelectricity that competes with its weak nontrivial band topology: in the high-symmetry rocksalt structure - in which its intrinsic electric dipole is quenched - this material develops metallic surface bands, but in its rhombic ground-state configuration - which hosts a nonzero spontaneous electric dipole - the crystalline symmetry is lowered, and the presence of surface electronic bands is not guaranteed. Here, the type of ferroelectric coupling and the atomistic and electronic structure of SnTe films ranging from 2 to 40 atomic layers (ALs) are examined on freestanding samples, to which atomic layers were gradually added. Four-AL SnTe films are antiferroelectrically coupled, while thicker freestanding SnTe films are ferroelectrically coupled. The electronic band gap reduces its magnitude in going from 2 to 40 ALs, but it does not close due to the rhombic nature of the structure. These results bridge the structure of SnTe films from the monolayer to the bulk.

The corrosion damage is easy to be formed on the surface of a metal structure in the corrosion environment, then the structural mechanical properties are degraded. For this purpose, the cellular automata method was adopted to simulate the uniform corrosion damage behavior of aluminium alloy in this paper. The uniform corrosion of aluminium alloy surfaces is simulated in complex corrosive environments and different concentration of corrosion solution. The forming processes of corrosion and the changed rules under different concentration of corrosion solution c and ambient temperature T are all obtained. It was shown that with the increasing concentration of corrosion c and the ambient temperature T, the number of corrosion cells increased, and the number of corrosion cells presents an approximate power function of etching time t.

Study of two-dimensional (2D) magnetic materials is important for both fundamental research and application. Here we report molecular beam epitaxy growth of iodides, candidates for exhibiting 2D magnetism. Decomposition of CrI3 is utilized to produce stable gaseous I2 flux. Growth of MnI2, GdI3, and CrI2 down to monolayer is successful achieved by co-depositing I2 and corresponding metal atoms. The thin films of the three materials are characterized by scanning tunneling microscope and found to be insulators with bandgaps of 4.4 eV, 0.6 eV, and 3.0 eV, respectively. The film growth paves the way for further study of magnetic properties at the 2D limit.

Dilation and breakage energy dissipation of four different granular soils are investigated by using an energy balance equation. Due to particle breakage, the dilation curve does not necessarily pass through the origin of coordinates. Breakage energy dissipation is found to increase significantly at the initial loading stage and then gradually become stabilised. The incremental dissipation ratio between breakage energy and plastic work exhibits almost independence of the confining pressure. Accordingly, a plastic flow rule considering the effect of particle breakage is suggested. The critical state friction angle is found to be a combination of the basic friction between particles and the friction contributed by particle breakage.

Stable ferroelectricity with high transition temperature in nanostructures is needed for miniaturizing ferroelectric devices. Here, we report the discovery of the stable in-plane spontaneous polarization in atomic-thick tin telluride (SnTe), down to a 1-unit cell (UC) limit. The ferroelectric transition temperature Tcof 1-UC SnTe film is greatly enhanced from the bulk value of 98 kelvin and reaches as high as 270 kelvin. Moreover, 2- to 4-UC SnTe films show robust ferroelectricity at room temperature.The interplay between semiconducting properties and ferroelectricity in this two-dimensional material may enable a wide range of applications in nonvolatile high-density memories, nanosensors, and electronics., United States. Department of Energy (Award DE-SC0010526)

The evolution of the quantum anomalous Hall effect with the thickness of Cr-doped (Bi,Sb)2 Te3 magnetic topological insulator films is studied, revealing how the effect is caused by the interplay of the surface states, band-bending, and ferromagnetic exchange energy. Homogeneity in ferromagnetism is found to be the key to high-temperature quantum anomalous Hall material.

The main purpose of this work is to investigate the fracture mechanical properties of aeronautical polymethyl methacrylate, which has been treated with directional tensile technology. Because of the special processing of directional polymethyl methacrylate, the molecular chain structures are different in different directions. The mechanical properties depend on the specific molecular chain structures. We use extended digital image correlation to measure the displacement field near the tip of the crack when the cracks grow in different directions in directional polymethyl methacrylate. We then tested the critical load for different specimens and analyzed the fracture morphology of the different specimens. Thanks to the experimental results, a molecular chain model of directional polymethyl methacrylate could be established. The analysis results using the molecular chain model are consistent with the experiments, which confirms the reliability of the molecular chain model.

Stable dispersions of polyaniline nanoparticles (PANI-NPs) were obtained from an oxidation polymerization of anilines in water with thermoresponsive poly(vinyl alcohol) (PVA) conjugated with 2-isobutyramidopropanoate moieties (PVA-AI) as the dispersing agent. UV–vis spectra, transmission electron microscopy, and dynamic light scattering (DLS) verified the formation of PANI-NPs. Compared with the PANI-NPs stabilized by PVA, PVA-AI was better at homogeneously dispersing PANI-NPs in water. Temperature-dependent UV–vis and DLS measurements demonstrated that the PANI-NP/PVA-AI composites were thermoresponsive in water. This was also evident from the turbid aqueous solutions at temperatures above the cloud point temperature ( T cp ). The T cp could be modulated by employing PVA-AI with different T cp or adding inorganic salts. Varying the pH below 5 had almost no influence on the T cp ; however, raising the pH above 5 lowered the T cp . Cyclic voltammetry analysis demonstrated that the PANI-NP/PVA-AI composites were electroactive and their redox process was repeatable. The T cp values of the composites in oxidation and reduction states were similar. Such thermoresponsive PANI-NP/PVA-AI composites were used as functional additives to improve the anticorrosive performance of waterborne epoxide coating films. After 460 h of harsh salt-spray corrosion, corrosion evaluation around the scribe, adhesion tests, potentiodynamic polarization measurement, electrochemical impedance spectroscopy measurement, and scanning electron microscope observation demonstrated that the anticorrosion performance of the epoxide coating containing thermoresponsive PANI-NP/PVA-AI was better than those with pure epoxide coating or epoxide coating containing PANI-NP/PVA without thermoresponsive properties.

Layered material indium selenide (In x Se y ) is a promising candidate for building next-generation electronic and photonic devices. We report a zirconium aided MBE growth of this van der Waals material. When co-depositing zirconium and selenium onto an indium phosphide substrate with a substrate temperature of 400°C at a constant zirconium flux rate of 0.01 ML/min, the polymorphic In x Se y layer emerges on top of the insulating ZrSe2 layer. Different archetypes, such as InSe, α-In2Se3 and β-In2Se3, are found in the In x Se y layers. A negative magnetoresistance of 40% at 2K under 9T magnetic field is observed. Such an In x Se y /ZrSe2 heterostructure with good lattice-matching may serve as a candidate for device applications.

The microstructures and mechanical properties of friction stir welded (FSW) Al&ndash, Zn&ndash, Mg alloy plate under different travel speeds were investigated. Both the average grain sizes (AGSs) of the shoulder affected zone (SAZ), nugget zone (NZ), and the widths of thermo-mechanically affected zone (TMAZ) decreased with the increase of travel speed. Moreover, the AGSs of NZ are always about 60% of that of SAZ at different travel speeds. The fractions of high-angle grain boundaries (HAGBs) in the FSW joints reduce with the distance away from the stir zone (SZ). Furthermore, the initial &eta, &rsquo, strengthening precipitates in NZ and TMAZ dissolve and GP zones form during subsequent natural aging, so that the hardness is similar in the two zones. The precipitate evolution in the heat-affected zone (HAZ) at hardness minima are affected by travel speeds, which induce the hardness minima and ultimate tensile strength (UTS) of FSW joints and increase with the increase of travel speed, and a fracture tends to occur at hardness minima location of HAZ during tensile testing.

2D SnTe films with a thickness of as little as 2 atomic layers (ALs) have recently been shown to be ferroelectric with in-plane polarization. Remarkably, they exhibit transition temperatures (Tc ) much higher than that of bulk SnTe. Here, combining molecular beam epitaxy, variable temperature scanning tunneling microscopy, and ab initio calculations, the underlying mechanism of the Tc enhancement is unveiled, which relies on the formation of γ-SnTe, a van der Waals orthorhombic phase with antipolar inter-layer coupling in few-AL thick SnTe films. In this phase, 4n - 2 AL (n = 1, 2, 3…) thick films are found to possess finite in-plane polarization (space group Pmn21), while 4n AL thick films have zero total polarization (space group Pnma). Above 8 AL, the γ-SnTe phase becomes metastable, and can convert irreversibly to the bulk rock salt phase as the temperature is increased. This finding unambiguously bridges experiments on ultrathin SnTe films with predictions of robust ferroelectricity in GeS-type monochalcogenide monolayers. The observed high transition temperature, together with the strong spin-orbit coupling and van der Waals structure, underlines the potential of atomically thin γ-SnTe films for the development of novel spontaneous polarization-based devices.

In this paper, the microstructure of friction stir welded between the Al–Li–Cu alloy and the Al–Zn–Mg–Cu alloy was studied using optical microscope(OM), electronic backscattered diffraction (EBSD), SEM, and TEM. The hardness profile revealed that the range of heat affect zone for the Al–Zn–Mg–Cu alloy was slightly wider than the Al–Li–Cu alloy when they suffered from the thermal transient. Additionally, the characterization of precipitates inside the different zones was obviously different, which corresponded to the microhardness distribution profile. At the periphery of the kissing line, the Al–Li–Cu and the Al–Zn–Mg–Cu alloys mutually diffused during the weld process. The magnesium element in the Al–Zn–Mg–Cu alloy diffused into the Al–Li–Cu alloy. But the copper and zinc had no change because of the low diffusion coefficient in aluminum. The heat affected zone of the Al–Zn–Mg–Cu alloy showed a higher corrosion susceptibility immersed into the corrosion environment, and the Al–Li–Cu alloy did not show severe corrosion.

A photocatalytic active CdS-TiO2 heterostructure composite was prepared by hydrothermal method and its morphology and properties were characterized. Results indicate that the CdS nanoparticles deposited on the surface of a TiO2 nanoparticles, which was in anatase phase. The particle scale of both of the components reached approximately 15 nm. In comparison to pure TiO2 (410 nm), the light absorption edge of the heterostructure composite was 550 nm, which could extend the light response from UV to the visible region. Under visible light irradiation, the degradation efficiency of tetracycline hydrochloride by the CdS-TiO2 composite achieved 87.06%, significantly enhancing photocatalytic activity than the as-prepared pure TiO2 and commercial TiO2 (Degussa P25). This character is attributed to the synergetic effect of these two components in the absorption of visible light.

Z. Wang, J. Wang, Y. Zang, Dr. T. Jiang, Y. Gong, Prof. C.-L. Song, Prof. S.-H. Ji, Prof. L.-L. Wang, Prof. K. He, Prof. W. Duan, Prof. X. Ma, Prof. X. Chen, Prof. Q.-K. Xue State Key Laboratory of Low-Dimensional Quantum Physics Department of Physics Tsinghua University Beijing 100084 , China E-mail: kehe@tsinghua.edu.cn; qkxue@tsinghua.edu.cn Q. Zhang, J.-A. Shi, Prof. L. Gu Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 , China Dr. T. Jiang College of Opto-Electronic Science and Engineering National University of Defense Technology Changsha , Hunan 410073 , China Prof. S.-H. Ji, Prof. L.-L. Wang, Prof. L. Gu, Prof. K. He, Prof. W. Duan, Prof. X. Ma, Prof. X. Chen, Prof. Q.-K. Xue Collaborative Innovation Center of Quantum Matter Beijing 100084 , P. R. China

We experimentally demonstrate a 160-Gb/s Ethernet packet switch using an 8.6-mm-long silicon nanowire for optical burst switching, based on cross phase modulation in silicon. One of the four packets at the bit rate of 160 Gb/s is switched by an optical control signal using a silicon based $1\times 1$ all-optical packet switch. Error free performance (BER < 1E-9) is achieved for the switched packet. The use of optical burst switching protocols could eliminate the need for optical buffering in silicon packet switch based optical burst switching, which might be desirable for high-speed interconnects within a short-reach and small-scale network, such as board-to-board interconnects, chip-to-chip interconnects, and on-chip interconnects.

Three-dimensional (3D) Dirac cones are predicted to reside in semimetals A3Bi (A = Na, K). By using molecular beam epitaxy (MBE) and scanning tunneling microscopy (STM), we have successfully established the growth conditions for Na3Bi thin films on Si(1 1 1)-7 × 7, and determined that the lattice of Na3Bi is rotated by 30 degree with respect to that of Si(1 1 1)-7 × 7. The Na3Bi/Si(1 1 1)-7 × 7 thin film was further used as the substrate for the growth of K3Bi. The 3D Dirac-cone-like electronic band structures of Na3Bi and K3Bi have been clearly revealed by angle resolved photoelectron spectroscopy (ARPES).

Super absorbent polymer (SAP) and fluff pulp were used as absorbing materials, and the different SAP mass ratio and fluff pulp were applied to paper diaper absorption core layer. Then, the influence of different SAP/fluff pulp in composite core layer on the paper diapers normal saline absorption rate and topsheet run-off were studied. Results showed that SAP has a significant effect on normal saline absorbency respect to fluff pulp. When the normal saline volume increased, the paper diapers absorption rate about normal saline decreased, while the topsheet run-off increased. When the SAP mass ratio to fluff pulp was 0.5:0.5, the liquid absorbency rate was 35.23 g/g, the paper diaper average absorption rate was 3.96 mL/s, and the biggest topsheet run-off was 13.25 g.

Silver nanoclusters (AgNCs) functionalized with hyperbranched polyethylenimines with a certain number of trimethylacetamide groups (PEI–TMA) were prepared through three steps. The influence of the preparation conditions, including the pH value in the mixture of PEI–TMA and Ag+ and the Ag+/PEI–TMA feed ratio, on the photoluminescence properties of the obtained nanocomposite of AgNCs and PEI–TMA (AgNC–PEI–TMA) was studied. The obtained AgNC–PEI–TMA nanocomposite was characterized by transmission electron microscopy, dynamic light scattering and zeta potential measurements, verifying the formation of the nanocomposite. AgNC–PEI–TMA in water was not only thermoresponsive, but also responded to other stimuli, including pH, inorganic salts, and loaded organic guest. The cloud point temperature (Tcp) of aqueous solutions of AgNC–PEI–TMA could be modulated through changing the pH, and varying the type and concentration of the inorganic salts and the loaded organic guest. The obtained AgNC–PEI–TMA nanocomposite was photoluminescent, and its maximum emission wavelength was not influenced by outside stimuli. Its emission intensity was influenced negligibly by pH, traditional salting-out anions (Cl− and SO42−), and the relatively polar aspirin guest. However, the traditional salting-in I− anion could quench its fluorescence a little.

The PP/PE composite fibers were prepared by melt extrusion, using polypropylene (PP) and polyethylene (PE) as raw materials and ethylene-octene block copolymers (OBC), titanium dioxide, antioxidants as additives. 3D stereoscopic embossed polyolefin nonwovens with "cross" pits and "O" type relief structure applied to topsheet of diapers were produced through air bonding process and 3D stereoscopic pressure rollers, respectively. The effect of structure of 3D stereoscopic embossed polyolefin nonwovens on the topsheet run-off and the rewet of diapers were studied by means of a set of permeability test. Comparing with the diapers using hot air nonwoven fabric as topsheet, the results of the diapers using 3D stereoscopic embossed polyolefin nonwovens as topsheet showed that the topsheet run-off decreased by 72.0%, as well as the first and second rewet reduced by 40.4% and 57.5%, respectively.

We report the successful growth of tetragonal FeS film with one or two unit-cell (UC) thickness on SrTiO3(001) substrate by molecular beam epitaxy. Large lattice constant mismatch with the substrate leads to high density of defects in single UC FeS, while it has been significantly reduced in double UC thick film due to the lattice relaxation. The scanning tunneling spectra on the surface of FeS thin film reveal the electronic doping effect of single UC FeS from the substrate. In addition, at the Fermi level, the energy gaps of approximate 1.5 meV are observed in films of both thicknesses at 4.6 K and below. The absence of coherence peaks of gap spectra may be related to the preformed Cooper-pairs without phase coherence., 11 pages, 4 figures

A monomer, 2-(isobutyramido)-3-methylbutyl methacrylate (IMMA) was synthesized through a two-step reaction. When a few of IMMA (less than 4 mol%) was copolymerized with N -vinylimidazole (VIm) under free radical polymerization condition, water-soluble P(VIm- co -IMMA) copolymers were obtained. Their structural information was verified and interpreted from 1 H NMR, FTIR and GPC. Kinetic analyses from 1 H NMR demonstrated that one-batch addition of IMMA into the polymerization system led to an inhomogeneous distribution of IMMA units in the copolymers, whereas homogeneous distribution of IMMA units in the copolymers could be obtained through the portion-wise addition of IMMA monomer. The thermal properties of such copolymers were measured by DSC. Compared with PVIm homopolymer, the few IMMA units in the P(VIm- co -IMMA) copolymer had little influence on the T g values. The obtained P(VIm- co -IMMA) copolymers were thermoresponsive in water, and their phase transition temperatures could be efficiently raised through reducing the IMMA content in the copolymers, raising the addition times of IMMA monomers or lowering the pH of media. Dynamic light scattering analysis showed that unlike the traditional thermoresponsive linear polymers, obvious size shrinkage around the phase transition temperature could not be observed in such P(VIm- co -IMMA) copolymers. Such copolymers could be used as smart organocatalysts in the hydrolysis of p -nitrophenyl acetate. Below the phase transition temperature the reaction rate followed the Arrhenius law, but above the phase transition temperature the reaction rate increased much slower than the prediction from the Arrhenius law. Moreover, the catalytic transition temperature could be tuned through utilizing the P(VIm- co -IMMA) copolymers with different phase transition temperature. The mechanism was discussed accordingly.