Yishi Su

Enhanced Mechanical Properties of Graphene (Reduced Graphene Oxide)/Aluminum Composites with a Bioinspired Nanolaminated Structure

Bulk graphene (reduced graphene oxide)-reinforced Al matrix composites with a bioinspired nanolaminated microstructure were fabricated via a composite powder assembly approach. Compared with the unreinforced Al matrix, these composites were shown to possess significantly improved stiffness and tensile strength, and a similar or even slightly higher total elongation. These observations were interpreted by the facilitated load transfer between graphene and the Al matrix, and the extrinsic toughening effect as a result of the nanolaminated microstructure.

Uniform dispersion of graphene oxide in aluminum powder by direct electrostatic adsorption for fabrication of graphene/aluminum composites.

The excellent properties of graphene promote it as an ideal reinforcement in composites. However, dispersing graphene homogenously into metals is a key challenge that limits the development of high-performance graphene-reinforced metal matrix composites. Here, via simple electrostatic interaction between graphene oxide (GO) and Al flakes, uniform distribution of reduced graphene oxide (RGO) in an Al matrix is achieved. The adsorption process of GO on Al flakes is efficient, as it can be completed in minutes and proceeds spontaneously without any chemical agents. GO can be partially reduced by the electron interchange during the adsorption process and could be thoroughly reduced after subsequent thermal annealing. A densified RGO/Al composite can be obtained by hot pressing the RGO/Al composite powders. By employing the preceding fabrication process, a composite reinforced with only 0.3 wt.% of RGO shows an 18 and 17% increase in elastic modulus and hardness, respectively, over unreinforced Al, demonstrating RGO is a better reinforcement than most other reinforcements.

Ag/diatomite for highly efficient solar vapor generation under one-sun irradiation

Efficient solar vapor generation under normal one-sun illumination is widely expected to relieve water scarcity all over the world. Herein, we prepare a highly efficient solar vapor generator via the deposition of Ag nanoparticles on diatomite. Ag/diatomite combined with a filter paper, an airlaid paper and a polystyrene foam showed excellent vapor generation performance (the evaporation rate and efficiency (η) were ∼1.39 kg m−2 h−1 and ∼92.2%, respectively) under one-sun illumination at room temperature (25.0 °C). To the best of our knowledge, these values outperform most of the previously reported vapor generation performances and vapor generation efficiencies (if not all). Compared to the performance of Ag/SiO2 (η ≈ 66.2%) and commercial Ag nanoparticles (η ≈ 72.6%), the outstanding performance of Ag/diatomite was attributed to the synergy of the localized surface plasmon resonance (LSPR) effect of Ag nanoparticles and the confinement effect in micrometer size-diatomite. Considering the low cost (

Composite structural modeling and tensile mechanical behavior of graphene reinforced metal matrix composites

10 per ton) and large-scale availability of diatomite as well as the easy construction of the vapor generation configuration that we proposed, this study provides prospects for practical applications towards relieving water scarcity.

Size and Crystallographic Orientation Effects on the Mechanical Behavior of 4H-SiC Micro-/nano-pillars

Owing to its distinguished mechanical stiffness and strength, graphene has become an ideal reinforcing material in kinds of composite materials. In this work, the graphene (reduced graphene oxide) reinforced aluminum (Al) matrix composites were fabricated by flaky powder metallurgy. Tensile tests of pure Al matrix and graphene/Al composites with bioinspired layered structures are conducted. By means of an independently developed Python-based structural modeling program, three-dimensional microscopic structural models of graphene/Al composites can be established, in which the size, shape, orientation, location and content of graphene can be reconstructed in line with the actual graphene/Al composite structures. Elastoplastic mechanical properties, damaged materials behaviors, graphene-Al interfacial behaviors and reasonable boundary conditions are introduced and applied to perform the simulations. Based on the experimental and numerical tensile behaviors of graphene/ Al composites, the effects of graphene morphology, graphene-Al interface, composite configuration and failure behavior within the tensile mechanical deformations of graphene/ Al composites can be revealed and indicated, respectively. From the analysis above, a good understanding can be brought to light for the deformation mechanism of graphene/Al composites.摘要石墨烯具有优异的机械性能, 已成为众多复合材料中的理想增强体材料. 本研究采用片状粉末冶金方法制备了具有仿生叠层结构的石墨烯/铝基复合材料, 同时对纯铝基体与石墨烯/铝基复合材料进行了拉伸试验. 通过基于Python语言自主研发的复合材料结构建模程序, 可以有效建立石墨烯/铝基复合材料的三维复合结构模型, 并实现石墨烯尺寸、形貌、取向、位置与含量等可控重构分布. 通过引入组分材料力学性能、损伤行为、界面行为及边界条件等实现了石墨烯/铝基复合材料的拉伸行为模拟, 并揭示了石墨烯形貌、石墨烯/铝界面、复合构型与失效行为等复合因素的影响规律, 对理解石墨烯/铝基复合材料的变形机理提供了有力依据.

Correlation Between Interfacial Structure and Toughness in SiC-Al Bilayers

Single crystalline 4H-SiC micro-/nano-pillars of various sizes and different crystallographic orientations were fabricated and tested by uniaxial compression. The pillars with zero shear stress resolved on the basal slip system were found to fracture in a brittle manner without showing significant size dependence, while the pillars with non-zero resolved shear stress showed a “smaller is stronger” behavior and a jerky plastic flow. These observations were interpreted by homogeneous dislocation nucleation and dislocation glide on the basal plane.

Mechanical behavior in bending deformation of thermoplastic composite laminates with different stacking sequences

Reinforcement surface modification is often used to improve the mechanical properties of particle-reinforced metal matrix composites, however, the extent to which such modifications affect the interfacial properties is yet to be revealed. In this study, we fabricated SiC-Al composite bilayers where the SiC underwent different surface treatments before Al deposition. Four-point bending tests showed that the samples made from acid-pickled and thermally oxidized SiC possessed substantially higher interfacial toughness than their untreated counterpart, a presumption inferred from mechanical tests on bulk SiCp-Al composites but never justified quantitatively. These findings were rationalized by the different interfacial constituents and structure in these samples.

Regain strain-hardening in high-strength metals by nanofiller incorporation at grain boundaries

This work aims to numerically analyze the mechanical properties of thermoplastic composite laminates with the [0°/90°]4s, [±25°]s4 and [0°/±45°/90°]2s stacking sequences under three-point bending loading. Three-dimensional multilayer structural models of composite laminates are established and then orthotropic elastics, Hill yield criterion and isotropic hardening rule are applied on these structural models of composite laminates to conduct the bending mechanical deformation. Fine enough meshes and reasonable loads and boundary conditions can efficiently reduce the computing cost. Afterwards, three-dimensional fiber–matrix structural models with disordered fiber arrangements of 0°/90°, 25°/−25° and 0°/45° interlaminates at the free edges of composite laminates are also created, in which the boundary conditions are transferred step by step using a three-step structural submodeling. Once more, orthotropic elastics and isotropic hardening are applied on these fiber–matrix structural models. This work provides a good way to understand the bending mechanical behavior of thermoplastic composite laminates with different stacking sequences.

Orientation-Dependent Tensile Behavior of Nanolaminated Graphene-Al Composites: An In Situ Study

Grain refinement to the nano/ultrafine-grained regime can make metals several times stronger, but this process is usually accompanied by a dramatic loss of ductility. Such strength-ductility trade-off originates from a lack of strain-hardening capacity in tiny grains. Here, we present a strategy to regain the strain-hardening ability of high-strength metals by incorporation of extrinsic nanofillers at grain boundaries. We demonstrate that the dislocation storage ability in Cu grains can be considerably improved through this novel grain-boundary engineering approach, leading to a remarkably enhanced strain-hardening capacity and tensile ductility (uniform elongation). Experiments and large-scale atomistic simulations reveal that a key benefit of incorporated nanofillers is a reduction in the grain-boundary energy, enabling concurrent dislocation storage near the boundaries and in the Cu grain interior during straining. The strategy of grain-boundary engineering through nanofillers is easily controllable, generally applicable, and may open new avenues for producing nanostructured metals with extraordinary mechanical properties.

Grain boundary-assisted deformation in graphene–Al nanolaminated composite micro-pillars

We conducted in situ microtension experiments in a scanning electron microscope (SEM) to study the orientation-dependent mechanical behavior of nanolaminated graphene-Al composite. We found a transition from a weak-and-brittle behavior in the isostress composite configuration to a strong-yet-ductile tensile response in the composite under isostrain condition. This is explained by the excellent load-bearing capacity of the graphene nanosheets and a crack deflection mechanism rendered by the laminate structure. These in situ measurements enabled direct observation of the deformation procedure and the exact failure mode, which highlight the importance of microstructural control in tailoring the mechanical properties of advanced metal matrix composites (MMCs).