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Negative Poisson's ratio (NPR) foams are usually prepared by the transformation of positive Poisson's ratio (PPR) foams with honeycomb cell structure, which face a challenge for restraining the increase in volume and Poisson's ratio once they are stimulated by high temperature. In addition, they cannot restore to its reentrant structure after large deformation. In this work, a novel method for preparing anisotropic NPR foam with excellent structural stability and shape recovery property is established by synergistically controlling hierarchical pore structures. The obtained NPR silicone rubber/polylactic acid (SR/PLA) composite foam has large-size holes (auxetic structure) with concave hexagonal shape and small-size honeycomb cells, which are generated by 3D printing technology and salt leaching method, respectively. The auxetic structure with the orientation characteristic is directly formed rather than transformed from the honeycomb cell structure. Therefore, the dimension and Poisson's ratio value of the NPR SR/PLA composite foam keep constant after high temperature heating treatment, meaning an excellent structural stability. Furthermore the excellent shape recovery property of the NPR SR/PLA composite foam endows it restore to the initial auxetic structure after large deformation to a large extent. It should be mentioned that the anisotropy of the NPR SR/PLA composite foam further will bring a broad application prospect in the field of human body cushioning materials, such as prosthetic lining sleeve. [Display omitted] • Anisotropic NPR SR/PLA composite foam was prepared by synergistically controlling hierarchical pore structures. • NPR SR/PLA composite foam has excellent structural stability and shape recovery property. • NPR SR/PLA composite foam shows both constant dimension and NPR after high temperature heating treatment. • This work overcomes the difficulty for deformation recovering of traditional NPR foams after large deformation. • Anisotropic NPR SR/PLA composite foam is promising as prosthetic lining sleeve. [ABSTRACT FROM AUTHOR]

In this work, separation performance of hierarchically porous membranes (HPMs) has been investigated with the combination of experiment and finite element simulation. From the blend of poly (vinylidene fluoride), poly (methyl methacrylate) and sodium chloride (i.e., PVDF/PMMA/NaCl), PVDF HPMs with cubic-large-pores connected through narrow nanopores have been fabricated successfully by etching NaCl and PMMA respectively. In the case of extremely high fill of NaCl, the inorganic fillers distribute all-over the specimen, yielding simultaneously internal and surface cubic-large-pores. Relative to the reference with only nanopores, the attained HPMs exhibit much higher permeability (up to ∼200 times) without any loss of selectivity. Such a significant improvement of separation performance can be attributed to the synergism effect between internal and surface cubic-large-pores. On one hand, the high content of isolated large pores in HPMs corresponds to shorter diffusion length and lower diffusion barrier for fluid; On the other hand, the existence of cubic-large-pores on membrane surface produces not only bigger pores and higher porosity on membrane surface, corresponding to convenient diffusion pathway, but also the enhanced hierarchical roughness including narrow nanopores and cubic-large-pores, providing additional driving force for water/oil separation. [Display omitted] • Simulation results clarify the synergism effect between internal and surface cubic-large-pores. • PVDF HPMs with both internal/surface cubic-large-pores and narrow nanopores have been fabricated successfully. • The attained PVDF HPMs exhibit higher flux without any loss of rejection ratio during separation. [ABSTRACT FROM AUTHOR]

• Comprehensive summary of the synthesis of 3D nanosuperstructures (3DSs) made of graphene, BN, TMD, and MXene. • Systematic discussion on properties of 3DSs, and modulating approaches to meet the requirement of specific applications. • Introduction on the broadest scope of applications enabled by 3DSs: energy, sensing, environment, and tissue engineering. The recent search for advanced materials with desired properties for next-generation flexible energy and electronic devices has focused on the unique class of two-dimensional (2D) materials made of layered crystalline structures. In particular, intensive interest has been devoted to configuring 2D materials into three-dimensional (3D) nanoporous superstructures (3DSs), which can effectively prevent aggregative restacking and maximize the exposure of active nanoscale planar surfaces. Here, we survey the recent progress of 3DSs made of several important 2D materials, including graphene, boron nitride (BN), transition metal dichalcogenide (TMD), and transition metal carbide/carbonitride (MXene). The characteristics of the formed 3DSs, including density, porosity, electrochemical activity, electronic and surface properties, depend on respective synthesis approaches and conditions. The obtained 3DSs, exhibiting distinctive properties, have been exploited in an array of applications, including shielding electromagnetic, thermal, and acoustic energies; sensing chemical, optical, and mechanical signals; serving as 3D scaffolds of energy and environment devices; and supporting 3D growth of live cells and tissues. At the end, this comprehensive review is summarized with future outlooks, including the great potentials, challenges, and bottleneck issues in fabrication and large-scale implementation of 3DSs. [ABSTRACT FROM AUTHOR]

Abstract The fixation stage of cellular structure during polymer foaming process is difficult to control due to difficult removing of internal heat, especially for crystalline polymers such as polypropylene (PP). In order to control cellular structure in the fixation stage, we established an universal method by introducing water as an in-situ internal cooling agent during the foaming process of PP. Particularly, hydrophilic fillers were added into the high melt flow index polypropylene (HMI-PP) with poor foaming ability to study the effect of adsorbed water on the foaming process of PP/filler composites during sc-CO 2 batch foaming process. Compared to pure HMI-PP, HMI-PP/hydrophilic filler composites showed increased adsorption amount for water and melt viscosity. The water within the composites played a key role in the foaming process, which not only served as a physical foaming agent to increase the volume expansion ratio of PP composite foam, but also showed the function of rapid cooling foam proved by thermal imaging technology. As a result, the presence of some hydrophilic fillers within HMI-PP matrix significantly improved the foaming properties of HMI-PP, including preventing internal bubble collapse and significantly increasing the volume expansion ratio of the foam. The applicability of this method was validated using other PP materials besides HMI-PP, including high molecular weight PP (HMW-PP), high melt strength PP (HMS-PP). Graphical abstract Image Highlights • The presence of hydrophilic fillers enhanced adsorption amount of water in PP/filler composites. • Adsorbed water served as both in-situ cooling agent and foaming co-agent during CO 2 batch foaming process. • The in-situ cooling effect of adsorbed water in PP composites provides an efficient method to control cellular structure. [ABSTRACT FROM AUTHOR]

As one of the most prospective candidates for next-generation rechargeable batteries, lithium-sulfur (Li-S) batteries currently still encounter great challenges associated with the low conductivity, severe shuttle effects, and sluggish redox kinetics. Herein, a self-supported sulfur host is fabricated by an in-situ growth of MoO 2 /MoS 2 nano-sheets on a carbon cloth (CC). First, carbon cloth serves as a good template for the morphology-controlled synthesis of nanostructured materials, which not only alleviates the agglomeration of MoO 2 /MoS 2 , but also enhances the flexibility and mechanical strengthen of the hybrid architecture as a free-standing host. Second, the polysulfide-trapping ability can be greatly enhanced by both physical and chemical adsorption from the MoO 2 /MoS 2 -anchored carbon cloth. Moreover, the partially sulfurized MoO 2 /MoS 2 nano-sheets integrate the benefits of conductive MoO 2 and sulfiphilic MoS 2 , thus facilitating fast charge transfer and redox kinetics of polysulfide conversion. As a result, these attributes enable the host to hold a high sulfur loading (up to 7.6 mg cm−2), which exceeds most of the reported carbon cloth-related cathode work in the literature. Additionally, the Li-S cells can achieve a high peak capacity of 1350 mA h g−1, excellent rate capability (C/20 - 2C rate), impressive areal capacity (up to 6.3 mA h cm−2), and a high capacity retention of 85% after 100 cycles. Image, graphical abstract [ABSTRACT FROM AUTHOR]