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Marangoni self‐propulsion refers to motion of liquid or solid driven by a surface tension gradient, and has applications in soft robots/devices, cargo delivery, self‐assembly etc. However, two problems remain to be addressed for motion control (e.g., ON–OFF) with conventional surfactants as Marangoni fuel: (1) limited motion lifetime due to saturated interfacial adsorption of surfactants; (2) in‐ situ motion stop is difficult once Marangoni flows are triggered. Instead of covalent surfactants, supra‐amphiphiles with hydrophilic and hydrophobic parts linked noncovalently, hold promise to solve these problems owing to its dynamic and reversible surface activity responsively. Here, we propose a new concept of 'supra‐amphiphile fuel and switch' based on the facile synthesis of disodium‐4‐azobenzene‐amino‐1,3‐benzenedisulfonate (DABS) linked by a Schiff base, which has amphiphilicity for self‐propulsion, hydrolyzes timely to avoid saturated adsorption, and provides pH‐responsive control over ON‐OFF motion. The self‐propulsion lifetime is extended by 50‐fold with DABS and motion control is achieved. The mechanism is revealed with coupled interface chemistry involving two competitive processes of interfacial adsorption and hydrolysis of DABS based on both experiments and simulation. The concept of 'supra‐amphiphile fuel and switch' provides an active solution to prolong and control Marangoni self‐propulsive devices for the advance of intelligent material systems. [ABSTRACT FROM AUTHOR]

Laser shock treatment is a kind of advanced surface strengthening technology for metallic materials, and its remarkable strengthening effect has been verified and universally accepted in many different metallic materials. In order to prevent the influence of laser shock on the shape size of precision parts or make use of the technology to introduce plastic deformation of metallic materials, it is necessary to study the deformation criterion of materials under laser shock. In this paper, the deformation law of different materials treated by laser shock is analyzed, and the limitation of laser shock in deformation phenomenon is explained based on the deformation mechanism of stress gradient and impact bending, the necessity of basic research on material deformation caused by laser shock is proposed. The effect of many factors such as laser parameters and impact modes, constraint modes on the laser shock-induced deformation is summarized, and it is proved that the adjustment and optimization of multiple parameters play an important role in controlling laser shock-induced deformation degree. Moreover, the advantages of numerical simulation method in the study of laser shock-induced deformation are analyzed in this paper, and at the same time,the urgency of establishing a material constitutive model adapting to high strain rate deformation and perfecting the simulation of laser plasma formation process is put forward. The development of laser shock deformation law in advanced manufacturing industry is prospected through the introduction of the sizing technology of laser shock, and the research directions of the deformation calibration based on laser shock and the on-line monitoring of deformation degree are presented.

The property of the surface layer of twice hole expansion Ti1023 alloy was analyzed by TEM, X-ray and roughness tester, and the strengthen mechanism of the bushing hole expansion was discussed. The results indicate that the roughness(Ra1.722→0.349 μm), hardness(Hv32→38) and residual stress distribution of the hole are improved by twice hole expansion techniques,and the fretting wear fatigue(fatigue limits 385→619MPa) of Ti1023 alloy is improved.

Self‐assembly of μm‐to‐mm components is important for achieving all‐scale ordering with requirements of extra energy for motion and interaction of components. Marangoni flows caused by surfactants on water provide appropriate energy but have limited lifetimes because of the inevitable interfacial aggregation and difficult decomposition of aggregated covalent surfactants that inactivate Marangoni effects. Here we have synthesized a supra‐amphiphile Marangoni "fuel"—sodium‐4‐(benzylideneamino) benzenesulfonate (SBBS)—that can be hydrolyzed in a timely manner to a species without surface activity to extend the motion time by 10‐fold. The motion was optimized at pH=2 by a fine equilibrium between the releasing and removal of interfacial SBBS, leading to the self‐assembly of millimeter‐scaled ordered dimers. The underlying mechanism was interpreted by motion analyses and simulation. This strategy provides an active solution to self‐assembly at the μm‐to‐mm scale, as well as interactive ideas between miniaturized chemical robots. [ABSTRACT FROM AUTHOR]

Coated paperboard not only has the advantages of traditional paper such as low density and cleanliness, but also overcomes its disadvantages such as poor barrier performance and sensitivity to moisture. It is more and more widely used in forming packaging containers. The current research on mechanical performance and inelastic deformation of paperboard mainly focus on its physical properties and simplified single-blank forming, but the studies on the forming limit diagram (FLD) of paperboard are relatively rare. In this paper, Nakajima tests have been carried out to determine the FLD curves of the polyethylene-coated paperboard blank along the machine direction, cross direction, and diagonal direction. A laminated stamping method for multi-blank is proposed and investigated by experiment and numerical simulation. Up to 5 blanks can be overlapped and stamped in a single punch stroke, and 5 bowl-shaped packaging containers can be formed simultaneously. Compared with the single-blank stamping process, the production efficiency can be greatly improved, but the flange area of the forming parts is easier to wrinkle. However, the wrinkling risk can still be controlled by optimizing the process parameters, such as friction factor and blank holder gap. [ABSTRACT FROM AUTHOR]

The effect of volume energy density and deposition energy density on the roughness, porosity, density and hardness of laser beam powder bed fusion (LBPBF) GTD222 Ni-based superalloy was systematically studied. The results showed that the roughness and porosity of the alloy decreased with the increase of the two laser energy densities, while the density and hardness increased. When the volume energy density and the deposition energy density exceeded a threshold value, the density and hardness reached the maximum value and almost remained constant. The volume energy density could be used to estimate the laser conditions for obtaining high-density LBPBF GTD222 alloy more accurately than the deposition energy density. The process parameters for the transformation of the alloy from porous to dense were determined based on the volume energy density. This study provides guidance for the optimization of the process parameters of LBPBF GTD222 alloy. [ABSTRACT FROM AUTHOR]

The stress effect generated by a high-energy short-pulse laser is utilized to achieve performance enhancement or precise shaping of metal material components in laser shock technology. A method of marking metal materials using laser shock technology is introduced in this paper. The physical principle is the effect of thickness of absorbing layers on the intensity of a laser-induced shockwave, which results in forming the mark with a certain shape using local surface plastic deformation. The marking method based on the principle of laser shock overcomes the deficiency of traditional marking methods that causes serious damage to the surface of the metal material and leads to a decrease in service performance. Laser shock marking(LSM) allows the surface of the metal material to form a predetermined mark, which also improves the service performance accordingly. [ABSTRACT FROM AUTHOR]

Abstract White light interference (WLI) data of different metal materials subjected to laser shock show two surface topography characteristics: laser shock-generated circle indentions with flat bottom or circular arc bottom. The difference of surface topographies is mainly related to the mechanical properties of metal materials. Hard metal materials acquire indentions with flat bottom while indentions with circular arc bottom are obtained by soft metal materials, and the two different indention appearance features result in the differences of surface quality. The identification of the different indention topography types can serve as a selecting basis of overlapping rate. Graphical abstract [ABSTRACT FROM AUTHOR]

A striking phenomenon is found that local plastic deformations, with an opposite direction to the external force, applied on metallic target surface under a given laser shock condition. Laser shock treatment is carried out on a number of metallic materials, and the surface topographies after laser shock treatment are observed via White Light Interferometer (WLI) measurement. The results show that many surface relief structures with irregular shapes and random distributions appear on target surfaces under the action of invisible shock waves. It personifies the real plastic flow behavior of metallic materials suffer to pressure waves, and the local reverse deformation. [ABSTRACT FROM AUTHOR]

Scheelite (CaWO4)-type microphosphors were synthesized by the precipitation method assisted with cetyltrimethyl ammonium bromide (CTAB). All compounds crystallized in the tetragonal structure with space group (No. 88). FE-SEM micrographs illustrate the spherical-like morphologies and rough surface. PL spectra indicate the broad emission peak maximum at 613 nm under UV excitation. Luminescence decay curves monitored by transition ( nm) of Eu in doped CaWO4 are presented, the curves exhibit a single-exponential feature and the lifetime for doped CaWO4 is 0.61 ms. [ABSTRACT FROM AUTHOR]

CaWO4 crystals were prepared by hydrothermal method assisting with phenol-formaldehyde polymer. The morphology can be controlled by polymer, and X-ray diffraction patterns results present a scheelite-type tetragonal structure, characteristic infrared active modes for O-W-O in the range from 500 cm to 4000 cm by Fourier transform infrared spectroscopic techniques. Raman results indicate that the crystals possess seven Raman active modes in the range from 100 cm to 1000 cm. A scanning electron microscopy study reveals that the particles exhibit uniform morphology. Luminescent properties were investigated by photoluminescence measurements, multicolor phosphors were obtained when Ca was substituted partly by lanthanide ions. [ABSTRACT FROM AUTHOR]

A series of ruthenium gallium stannides have been prepared with stoichiometry RuGavSnw, where 8+3v+4w=14 and 0

Residual stress in structural components is crucial as it affects both service performance and safety. To investigate the evolution of residual stress in a laser-peen-formed panel, this study adopted two plate samples of thickness 3 and 9 mm instead of the conventional Almen strip. The two plates were peened with an identical energy density of 10.99 GW/cm2. The residual stress across the entire section was determined using a slitting method, and near-surface stress was then verified by X-ray diffraction. Furthermore, cross-sectional variation in hardness and microstructure were characterized to understand the residual stress evolution. The experimental results showed that different thicknesses resulted in distinct spatial distributions of residual stress. The 3-mm plate demonstrated a shallow (0.5 mm) and lower compressive stress magnitude (−270 MPa) compared with a deeper (1 mm) and higher compressive stress (−490 MPa) in the 9-mm plate. Further analysis revealed that the deformation compatibility during the forming process inevitably leads to a stress compensation effect on the peened side. The decrease in the depth and magnitude of the compressive residual stress in the thin plate was mainly attributed to low stiffness and large deflection. [ABSTRACT FROM AUTHOR]

Residual stress is a ubiquitous phenomenon in laser powder bed fusion (LPBF) metal parts due to high temperature gradients and uneven heating during building processes. Subsequent stress-relief (SR) heat treatment is usually conducted to reduce the geometrical distortion and microscopic cracks induced by residual stress after the LPBF process. Using electron microscopy, X-ray diffraction, and stress-rupture tests, the experimental results revealed that the stress-rupture life of a nickel-based superalloy, IN625 alloy, subjected to SR treatment at 870°C and 980°C is inferior to that of the as-built (AB) alloy. The fundamental cause for this phenomenon is that more δ phase precipitates in the grains of the AB alloy during the stress-rupture test at 750°C/230 MPa, resulting in an increased dispersion hardening effect and a decreased ductility. Furthermore, the Laves and δ phases along grain boundaries in the SR treated alloys are more likely to coarsen, which is the second reason for the decreased stress-rupture life of the SR treated alloys. [ABSTRACT FROM AUTHOR]

• The round end rectangular joint is fabricated by incremental laser shock clinching. • The multi-pass forming strategy can greatly improve the formability and surface quality. • Most material flows along the transverse direction, meanwhile flows slightly towards the laser spot moving direction. • The mechanical properties of the joints are related to the load directions and clamping ways. A novel method to make a round end rectangular joint whose total length is much larger than the diameter of the laser spot, named as incremental laser shock clinching, was proposed in this paper. Experimental and numerical investigation was conducted to verify the feasibility for joining three sheets of copper/aluminum/stainless steel. The transverse section and the appearance of the joint were explored to determine the spacer height and the forming strategy. The shape evolution of interlock was discussed by observing sectional images. To describe the material flow characteristics in the forming process, a series of typical points were traced. The mechanical properties of the joints relating to the load directions and clamping ways were studied by tensile shear tests. The results show that fine joints with smooth surface morphology and uniform thickness can be obtained under the larger spacer height and multi-pass forming strategy. Simulated results agree well with the experimental results, which implies that the finite element model can be effectively used to analyze the process. During deformation, most material flows along the transverse direction to form undercuts, meanwhile flows slightly towards the laser spot moving direction. What's more, the maximum load in the perpendicular shear test is larger than that in the parallel shear test. Two failure modes are observed when the copper foil and pre-slotted sheet are clamped on one side and only one failure mode is found when the copper foil is clamped alone. [ABSTRACT FROM AUTHOR]