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Numerical investigations of pore characteristics in platelet particles with various macroscopic structures were performed for fundamental understanding of transport properties in clay layers composed of montmorillonite particles. The effect of macroscopic structures of particles on the geometric characteristics of pore networks was examined, particularly focusing on the tortuosity which represents the sinuosity of voids. Monte Carlo simulations of platelet particles under various initial configurations were performed to obtain metastable structures with internal differences. A random walk analysis was performed in extracted macropores of platelet structures. The tortuosity of pore network in variously structured platelet particles was evaluated from the results of the random walk analysis. The numerical results showed that the macrostructures of particles form complicated pore networks, which significantly influence the tortuosity. The "diffusional" tortuosity obtained from the random walk analyses was compared with the existing "geometrical" tortuosity model. It was found that configurational characteristics of platelets, such as size and orientation angle of particle clusters, were vital to estimate the tortuosity. The obtained tortuosity was also compared with the experimental results of the diffusion coefficient in clay layers obtained from previous studies. The results suggested that a complicated density dependence of diffusivity in clay arises from the diversity of macroscopic particle structures. [ABSTRACT FROM AUTHOR]

By using superaligned carbon nanotube (SACNT) macrostructures as reinforcements, the one-step homoepitaxial growth of SACNT/graphite composites was achieved with a home-built experimental setup at temperatures as high as 2600 °C. Compared with traditional furnace heating method, this approach offers the advantages of increased convenience, high throughput and energy efficiency. This high-temperature homoepitaxy strategy was applied to three kinds of structures: SACNT yarn, SACNT film, and SACNT array. Because of the high temperature which exceeded 1800 °C, the samples after high-temperature homoepitaxy showed increased G/D peak area ratios in the Raman spectra, enhanced mechanical properties and improved thermal properties, all of which can meet the requirements of various applications. Image 1 • Three kinds of superaligned carbon nanotube (SACNT) structures are used for macroscopic continuity and manipulation. • The SACNT/graphite composite has been fabricated in a home-built experimental setup by self-heating up to 2600℃. • One-step fulfilment of both carbon deposition and simultaneous graphitization leads to convenience and energy efficiency. • Samples after high-temperature homoepitaxy exhibit increased G/D ratio in Raman spectra and superior material performance. [ABSTRACT FROM AUTHOR]

Abstract Since their discovery in 2011, transition metal carbides or nitrides (MXenes) have attracted a wide range of attention due to their unique properties and promise for use in a variety of applications. However, the low accessible surface area and poor processability of MXene nanosheets caused by their restacking have severely hindered their practical use, and this is expected to be solved by integrating them into macroscopic assemblies. Here, recent progress in the construction of MXene assemblies from 2D to 3D at the macro and/or microlevel is summarized. The mechanisms of their assembly are also discussed to better understand the relationship between performance and assembled structure. The possible uses of MXene assemblies in energy conversion and storage, electromagnetic interference shielding and absorption, and other applications are summarized.

Since their discovery in 2011, transition metal carbides or nitrides (MXenes) have attracted a wide range of attention due to their unique properties and promise for use in a variety of applications. However, the low accessible surface area and poor processability of MXene nanosheets caused by their restacking have severely hindered their practical use, and this is expected to be solved by integrating them into macroscopic assemblies. Here, recent progress in the construction of MXene assemblies from 2D to 3D at the macro and/or microlevel is summarized. The mechanisms of their assembly are also discussed to better understand the relationship between performance and assembled structure. The possible uses of MXene assemblies in energy conversion and storage, electromagnetic interference shielding and absorption, and other applications are summarized. [ABSTRACT FROM AUTHOR]

Abstract: A new conceptual method termed as suspension 3D printing is demonstrated using self‐healing hydrogel support to create macroscopic structures of liquid metal that exhibits properties indicative of a nonprintable object. The relationships between the process parameters, supporting gel concentration, and the deposited microdroplet geometry are clarified. The smaller nozzle inner diameter, lower flow rate, and higher printing speed will lead to a smaller droplets size. The gel concentration plays a significant role on patterning the droplets space. The results presented can be applied to design the target feature and further optimize the input parameters. Besides, this paper also illustrates the capability and potential application of the method in constructing 3D macrostructures and stereo electronic systems using these liquid metal droplets. Based on this strategy, it is possible to print liquid metal into sophisticated multidimensional and shape transformable functional structures ignoring the effects of fluid instability, gravity, and surface tension. Furthermore, this work can help remove the limits of materials and technical barriers to enable a wide variety of materials to be printed into arbitrary shapes. It is expected that further practices of the methodology will facilitate the advancements in multiscale droplets generation, flexible electronics, encapsulation technologies, biology and medicine, etc. [ABSTRACT FROM AUTHOR]

Hollow carbon spheres (HCSs) represent a special class of functional materials, to which intense interest has been paid in the fields of materials science and chemistry. A major problem with these materials is the lack of sufficient particle engineering and mechanical strength for practical applications and the difficulty of up-scaling. Herein, we report a general, template-free, phase-separation approach, in which the liquid-liquid phase-inversion process and a gas-foaming process are coupled for the first time, for fast and continuous processing of uniform HCSs. The obtained HCSs have particle sizes on the millimeter scale, and a hierarchical structure with an interpenetrating, open-porous, carbon shell and huge external voids, therefore permitting rapid transport of molecules into, throughout, and out of the hollow structure. By evenly dispersing the CNTs in the precursor solution, CNT-reinforced HCSs can be achieved with significantly enhanced mechanical strength, hydrophobicity, and electronic and thermal properties. The resulting CNT-reinforced HCSs offer a viable route to remove the engine oil from water in a fixed-bed system. Moreover, these floatable HCSs can receive and convert sunlight to heat at the water-air interface, resulting in a great enhancement in solar evaporation rate compared to conventional bulk heating schemes. [ABSTRACT FROM AUTHOR]

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