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Oily wastewater discharge causes not only the pollution of environment but also the waste of resources. Existing technologies for wastewater remediation, such as membrane and particle methods, are variable and effective, but are difficult for achieving continuous and rapid oil–water separation. Here, with the synergy of turbo stirring, a strategy for emulsion separation is demonstrated based on the bio‐inspired cone array barrel. Under the centrifugal force, oil droplets in emulsion are thrown onto the cones arrayed on inner wall due to the Coriolis effect, captured by microstructures on cone surface and then penetrate out through the superhydrophobic pores, while only the remediated water remains. The separation technique maintains a high efficiency of above 99.5% for over 30 times of use, as well as for emulsions with variable ingredients. This structure‐dynamics synergistic separation strategy evolves the future technologies on water purification in industrial and daily processes. A new strategy for wastewater remediation is developed based on the synergy of turbo stirring and gradient structure. Under centrifugal force, the oil droplets in emulsion can continuously be captured on inner wall and then penetrate out from the cone array barrel, in which remediated water remains. Future technologies of water purification can be predicted based on this work.

The structural and phase state of the surface layers of technically pure titanium (VT1-0 alloy) implanted with aluminum ions in three states (submicrocrystalline, ultrafine-grained, and fine-grained) obtained by multiple uniaxial pressing (abc pressing) followed by multipass rolling in groove rolls at room temperature and subsequent annealing at 573, 673, and 773 K for 1 h, respectively, has been studied by transmission electron microscopy and energy dispersive X-ray spectroscopy on foils cut perpendicular to the machined sample surface. Ion implantation has been performed for 8 h and 20 min at an irradiation dose of 10 × 10 17 ions/cm 2 and a temperature of 623 K. It has been found that the implantation led to the formation of a gradient structure consisting of five layers. For each layer, the thickness, phase composition, and shape and arrangement of second-phase particles have been determined and the α-Ti grain size and the size, distribution density, and volume fractions of separated particles have been measured. It has been established that the implantation causes the formation of Ti 3 Al and TiAl 3 intermetallic phases. Ti 3 Al particles have a lamellar shape and are located inside parts of α-Ti grains, while TiAl 3 particles have a rounded shape and are arranged randomly.

HighlightsMicrowave absorber with nanoscale gradient structure was proposed for enhancing the electromagnetic absorption performance.Outstanding reflection loss value (−62.7 dB), broadband wave absorption (6.4 dB with only 2.1 mm thickness) in combination with flexible adjustment abilities were acquired, which is superior to other relative graded distribution structures.This strategy initiates a new method for designing and controlling wave absorber with excellent impedance matching property in practical applications.In the present paper, a microwave absorber with nanoscale gradient structure was proposed for enhancing the electromagnetic absorption performance. The inorganic–organic competitive coating strategy was employed, which can effectively adjust the thermodynamic and kinetic reactions of iron ions during the solvothermal process. As a result, Fe nanoparticles can be gradually decreased from the inner side to the surface across the hollow carbon shell. The results reveal that it offers an outstanding reflection loss value in combination with broadband wave absorption and flexible adjustment ability, which is superior to other relative graded distribution structures and satisfied with the requirements of lightweight equipment. In addition, this work elucidates the intrinsic microwave regulation mechanism of the multiscale hybrid electromagnetic wave absorber. The excellent impedance matching and moderate dielectric parameters are exhibited to be the dominative factors for the promotion of microwave absorption performance of the optimized materials. This strategy to prepare gradient-distributed microwave absorbing materials initiates a new way for designing and fabricating wave absorber with excellent impedance matching property in practical applications.

Multi-material laser powder bed fusion (LPBF) additive manufacturing is a promising approach for integrating the functionality and mechanical performance of dissimilar materials into complex parts. This review offers a comprehensive overview of the recent advancements in multi-material LPBF, with a particular focus on compositionally heterogeneous/gradient parts and their fabrication methods and equipment, control of interfacial defects, innovative designs, and potential applications. It commences with the introduction of LPBF-processed compositionally heterogeneous/gradient structures with dissimilar material distributions, including Z-direction compositionally heterogeneous structures, compositionally gradient structures in the Z-direction and XY planes, and three-dimensional (3D) compositionally heterogeneous structures. Subsequently, various LPBF methods and equipment for fabricating compositionally heterogeneous/gradient structures have been presented. Furthermore, the interfacial defects and process control during LPBF for these types of compositionally heterogeneous/gradient structures are discussed. Additionally, innovative designs and potential applications of parts made from compositionally heterogeneous/gradient structures are illustrated. Finally, perspectives on the LPBF fabrication methods for compositionally heterogeneous/gradient structures are highlighted to provide guidance for future research. LPBF additive manufacturing of compositionally heterogeneous/gradient structures is reviewed. Powder delivery methods for compositionally heterogeneous/gradient parts are presented. Process control for compositionally heterogeneous/gradient parts is discussed. Potential applications of compositionally heterogeneous/gradient parts are highlighted.

Highlights The layered arrangement and gradient distribution of magnetic MXene are firstly combined to improve the electromagnetic wave (EMW) RL min and broaden effective absorption bandwidth. Absorption, reflection, and transmission (A–R–T) power coefficient analysis is firstly used to guide the gradient distribution, so as to realize EMW incidence at low-concentration surface, loss at middle concentration interlayer and reflection at high-concentration bottom. The layered gradient composite (LG5-10-15) achieves complete absorption coverage of X-band at thickness of 2.00-2.20 mm with RL min of -68.67 dB. The morphological distribution of absorbent in composites is equally important with absorbents for the overall electromagnetic properties, but it is often ignored. Herein, a comprehensive consideration including electromagnetic component regulation, layered arrangement structure, and gradient concentration distribution was used to optimize impedance matching and enhance electromagnetic loss. On the microscale, the incorporation of magnetic Ni nanoparticles into MXene nanosheets (Ni@MXene) endows suitable intrinsic permittivity and permeability. On the macroscale, the layered arrangement of Ni@MXene increases the effective interaction area with electromagnetic waves, inducing multiple reflection/scattering effects. On this basis, according to the analysis of absorption, reflection, and transmission (A–R–T) power coefficients of layered composites, the gradient concentration distribution was constructed to realize the impedance matching at low-concentration surface layer, electromagnetic loss at middle concentration interlayer and microwave reflection at high-concentration bottom layer. Consequently, the layered gradient composite (LG5-10–15) achieves complete absorption coverage of X-band at thickness of 2.00–2.20 mm with RL min of −68.67 dB at 9.85 GHz in 2.05 mm, which is 199.0%, 12.6%, and 50.6% higher than non-layered, layered and layered descending gradient composites, respectively. Therefore, this work confirms the importance of layered gradient structure in improving absorption performance and broadens the design of high-performance microwave absorption materials.

HighlightsThe bioinspired self-sensing actuated gradient hydrogel was developed by a wettability-based method via precipitation of MoO2 nanosheets.Self-sensing actuated gradient hydrogel combined ultrafast thermo-responsive actuation (21° s–1), exceptional photothermal efficiency (3.7 °C s–1) and high sensing properties (GF = 3.94).The first self-sensing remote interaction system based on gradient hydrogel actuators and robotic hands was constructed.The development of bioinspired gradient hydrogels with self-sensing actuated capabilities for remote interaction with soft-hard robots remains a challenging endeavor. Here, we propose a novel multifunctional self-sensing actuated gradient hydrogel that combines ultrafast actuation and high sensitivity for remote interaction with robotic hand. The gradient network structure, achieved through a wettability difference method involving the rapid precipitation of MoO2 nanosheets, introduces hydrophilic disparities between two sides within hydrogel. This distinctive approach bestows the hydrogel with ultrafast thermo-responsive actuation (21° s−1) and enhanced photothermal efficiency (increase by 3.7 °C s−1 under 808 nm near-infrared). Moreover, the local cross-linking of sodium alginate with Ca2+ endows the hydrogel with programmable deformability and information display capabilities. Additionally, the hydrogel exhibits high sensitivity (gauge factor 3.94 within a wide strain range of 600%), fast response times (140 ms) and good cycling stability. Leveraging these exceptional properties, we incorporate the hydrogel into various soft actuators, including soft gripper, artificial iris, and bioinspired jellyfish, as well as wearable electronics capable of precise human motion and physiological signal detection. Furthermore, through the synergistic combination of remarkable actuation and sensitivity, we realize a self-sensing touch bioinspired tongue. Notably, by employing quantitative analysis of actuation-sensing, we realize remote interaction between soft-hard robot via the Internet of Things. The multifunctional self-sensing actuated gradient hydrogel presented in this study provides a new insight for advanced somatosensory materials, self-feedback intelligent soft robots and human–machine interactions.

Friction stir processing (FSP) has attracted much attention in the last decade and contributed significantly to the creation of functionally graded materials with both gradient structure and gradient mechanical properties. Subsurface gradient structures are formed in FSPed metallic materials due to ultrafine grained structure formation, surface modification and hardening with various reinforcing particles, fabrication of hybrid and in situ surfaces. This paper is a review of the latest achievements in FSP of non-ferrous metal alloys (aluminum, copper, titanium, and magnesium alloys). It describes the general formation mechanisms of subsurface gradient structures in metal alloys processed by FSP under various conditions. A summary of experimental data is given for the microstructure, mechanical, and tribological properties of non-ferrous metal alloys.

We consider systems of reaction–diffusion equations as gradient systems with respect to an entropy functional and a dissipation metric given in terms of a so-called Onsager operator, which is a sum of a diffusion part of Wasserstein type and a reaction part. We provide methods for establishing geodesic λ-convexity of the entropy functional by purely differential methods, thus circumventing arguments from mass transportation. Finally, several examples, including a drift–diffusion system, provide a survey on the applicability of the theory.

With the widespread application of communication equipment with electromagnetic signal transmission to cause electromagnetic radiation pollution, there is an urgent need for high-performance electromagnetic shielding materials. Here, an ultrathin, flexible, alternating multilayered, and conductive gradient-structured cellulose nanofiber–MXene/silver nanowire (CNF-MXene/AgNW) nanocomposite paper with high mechanical strength, strong electromagnetic interference (EMI) shielding, and outstanding thermal management was constructed via the alternating vacuum filtration (AVF) process. The extensive hydrogen bonding interactions between MXene, CNF, and AgNW enhance the interfacial adhesion and conductive synergy between layers, resulting in excellent tensile strength of 194.3 MPa and fracture strain of 7.62% of nanocomposite paper. The alternating conductive gradient structure of the nanocomposite paper greatly increases the interlayer multiple reflections and absorption of electromagnetic waves, resulting in a high conductivity of 3237.35 S cm−1 and excellent electromagnetic shielding efficiency of 65.4 dB for the nanocomposite paper. Under an external low voltage of 3 V, the surface temperature of the nanocomposite paper reaches 107.2 ℃ within 10 s and can be stable for a long time. These results indicate that CNF-MXene/AgNW nanocomposite paper with a conductive gradient structure has potential applications in the fields of aerospace, communication engineering, and wearable devices.

Magnesium alloys that are low density and have a high specific strength are widely utilized as lightweight structural materials. Due to their hexagonal close-packed crystal structure, plastic deformation in magnesium alloys is strongly limited in dislocation slip and mainly accommodated by deformation twinning, which results in distinct mechanical anisotropy and tension–compression asymmetry. This paper, centered on mechanism competition and microstructure regulation, systematically reviews the recent progress in the compressive mechanical responses of magnesium alloys. Key results reveal the cooperative and competitive mechanisms between slip and twinning, the significant controlling effects of temperature and strain rate on deformation behavior, and the effective design strategies of gradient and heterogeneous structures that achieve superior strength–ductility synergy. This review provides essential theoretical support for the development and performance optimization of high-performance magnesium alloys.