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Carbonaceous materials are considered strong candidates as anode materials for sodium‐ion batteries (SIBs), which are expected to play an indispensable role in the carbon‐neutral era. Herein, novel braided porous carbon fibres (BPCFs) are prepared using the chemical vapour deposition (CVD) method. The BPCFs possess interwoven porous structures and abundant vacancies. The growth mechanism of the BPCFs can be attributed to the polycrystalline transformation of the nanoporous copper catalyst in the early stage of CVD process. Density functional theory calculations suggest that the Na+ adsorption energies of the mono‐vacancy edges of the BPCFs (−1.22 and −1.09 eV) are lower than that of an ideal graphene layer (−0.68 eV), clarifying in detail the adsorption‐dominated sodium storage mechanism. Hence, the BPCFs as an anode material present an outstanding discharge capacity of 401 mAh g−1 at 0.1 A g−1 after 500 cycles. Remarkably, this BPCFs anode, under high‐mass‐loading of 5 mg cm−2, shows excellent long‐term cycling ability with a reversible capacity of 201 mAh g−1 at 10 A g−1 over 1000 cycles. This study provided a novel strategy for the development of high‐performance carbonaceous materials for SIBs. [ABSTRACT FROM AUTHOR]

Hierarchical hollow CoP and carbon composites were obtained through a facile synthetic method, where carbonization and phosphorization of the precursor were completed within one single step. The composites are composed of hollow CoP@C spheres, which are further made up of CoP nanoparticles with a thin outer carbon layer. Electrochemical performances of the prepared CoP@C composites as anodes for sodium and potassium storage were evaluated and compared. In situ TEM, in situ synchrotron XRD, and DFT calculations were conducted to study the structural evolution and the interaction between Na/K and CoP during cycling processes. Benefiting from the synergistic effect of conductive carbon layer and hierarchical hollow structure, the as‐prepared CoP@C composites demonstrate superior sodium and potassium storage capability as anode materials for rechargeable batteries. [ABSTRACT FROM AUTHOR]

Hierarchical hollow CoP and carbon composites were obtained through a facile synthetic method, where carbonization and phosphorization of the precursor were completed within one single step. The composites are composed of hollow CoP@C spheres, which are further made up of CoP nanoparticles with a thin outer carbon layer. Electrochemical performances of the prepared CoP@C composites as anodes for sodium and potassium storage were evaluated and compared. In situ TEM, in situ synchrotron XRD, and DFT calculations were conducted to study the structural evolution and the interaction between Na/K and CoP during cycling processes. Benefiting from the synergistic effect of conductive carbon layer and hierarchical hollow structure, the as‐prepared CoP@C composites demonstrate superior sodium and potassium storage capability as anode materials for rechargeable batteries. [ABSTRACT FROM AUTHOR]

The microstructure and defects of as-grown and annealed ZnO/Si thin films were investigated by high-resolution transmission electron microscopy (HRTEM). The cross-sectional bright-field TEM images showed that the ZnO thin films consisted of columnar grains. The selected-area electron diffraction pattern showed that the ZnO/Si thin film were c-axis oriented and the deviation angle along the ZnO (0001) direction with respect to the growth direction was no more than 5°. The grain boundaries can be classified into three types: low-angle boundaries, boundaries near a 30 deg angle with (1010) facet structures and large-angle boundaries. In addition to grain boundary, the as-grown and annealing processing defects were also investigated by HRTEM. The crystal quality of the ZnO/Si thin films can be improved by annealing at 600 °C. However, at too high an annealing temperature of 800 °C, the newly produced processing defects such as three layer stacking fault and double stacking fault were formed. The research was useful for us to find optimal growth conditions to improve ZnO/Si thin film quality. [ABSTRACT FROM AUTHOR]

For the accuracy of experimental results, preparing a high quality polished surface and cross-section of the materials for further analysis using electron back-scattered diffraction (EBSD), electron probe microanalysis (EPMA), and scanning probe microscopy (SPM) is extremely important. Broad ion beam (BIB) polishing, a method based on the principle of ion bombardment, has irreplaceable advantages. It makes up for the drawbacks and limitations of traditional polishing methods such as mechanical polishing, electrochemical polishing, and chemical polishing. The ions will not leave the bombardment area during polishing, which makes the BIB method suitable for porous materials. The energy of the ion beam can be adjusted according to the sample to reduce the deformation and strain of the polishing area, especially for fragile, soft, and hard materials. The conditions that need to be controlled during BIB polishing are simple. This paper demonstrated the unique advantages of BIB polishing technology in porous, layered and powder materials characterization through some typical application examples, and guided more researchers to understand and utilize BIB polishing technology in the development of new applications. [ABSTRACT FROM AUTHOR]

In this work, a comparative study of thermally reduced graphite oxide (rGO) materials prepared by thermal exfoliation and reduction of graphite oxide (GO) at the temperature of 300 °C and 600 °C under different atmospheres (air, N2, Ar, vacuum and H2) was investigated through kinds of characterizations. The evaluation of chemical structure and quality of the rGOs by these various atmospheres is of high importance and is attempted side‐by‐side for the first time in this paper. The order of C/O ratio of rGOs obtained at 600 °C is that HH‐rGO>HV‐rGO>HAr‐rGO≈HN‐rGO>HA‐rGO, whereas the effect of atmospheres on the rGOs obtained at 300 °C is not obvious. HH‐rGO possesses better restoration of π‐conjugated structure and the increased average size of sp2 carbon domains compared with other rGOs. rGOs with higher reduction degree result in the aggregation of rGO nanosheets and closer to graphite structure. TGA results proved the order of thermal stability is that HH‐rGO>HV‐rGO>HAr‐rGO≈HN‐rGO>HA‐rGO. Additionally, HH‐rGO could be easily exfoliated to few‐layer nanosheets compared with others according to the AFM measurement. We believe that the findings will deepen our understanding of graphene obtained via thermal exfoliation and reduction method. In this work, the effect of atmospheres and temperature on the chemical structure and quality of the rGOs was investigated. The order of C/O ratio and the order of thermal stability of rGOs were obtained through XPS and TGA results, respectively. The defect level of of rGOs (300 °C) under different atmospheres is similar. The ID/IG value for HH‐rGO (0.90) obviously decreased. Additionally, HH‐rGO could be easily exfoliated to few‐layer nanosheets compared with others according to the AFM measurements. [ABSTRACT FROM AUTHOR]

Presents a study on the calculation of the critical layer thickness strain in Si1-xGe/Si strained-layer heterostructures. Heterostuctures and superlattices of Si1-Gex/Si; Theoretical model and calculation used to carry out the study; How the critical layer thickness is reduced.

Pure-Ge/Si short-period superlattice (SPS) samples consisting of 1.5-monolayer Ge and a 1.4- to 3.8-nm-thick Si layer grown by gas source molecular beam epitaxy (GS-MBE) were studied by double-crystal x-ray diffraction. For SPS with a Si layer less than 2.4 nm, the satellite peak caused by the SPS structure in the rocking curve is quite broad, and no fine structure is found, indicating that there exists dislocation and waviness epilayers in the SPS. For SPS with a thick Si layer, the rocking curve is sharp and fine interference structures exist, indicating smooth epilayers in the SPS. It is found that both broad and sharp peaks exist but without fine structure in the rocking curves for SPS samples with a Si layer thickness ( L) in the range of 2.1-2.9 nm, which is the range in which an abnormal photoluminescence band appears in photoluminescence spectra. This result strongly supports H. Sunamura's suggestion that the abnormal photoluminescence band is caused by waviness formation of the epilayer due to vertical correlation of thickness fluctuations by the local strain field. [ABSTRACT FROM AUTHOR]

How a heavily charged metal nanocrystal, and further a dual-nanocrystals system behavior with continuous electron charging? This refers to the electric dynamics in charged particles as well as the crystal growth for real metal particles, but it is still opening in experimental observations and interpretations. To this end, we performed an in-situ electron-beam irradiation study using transmission electron microscopy (TEM) on the Au nanocrystals that freely stand on the nitride boron nanotube (BNNT). Au nanocrystalline particles with sizes of 2–4 nm were prepared by a well-controlled sputtering method to stand on the BNNT surface without chemical bonding interactions. Au nanoparticles presented the surface atomic disorder, diffusion phenomena with continuous electron-beam irradiation, and further, the long-range motion that contains mainly the three stages: charging, activation, and adjacence, which are followed by final crystal growth. Firstly, the growth process undergoes the lattice diffusion and subsequently the surface-dominated diffusion mechanism. These abnormal phenomena and observations, which are fundamentally distinct from classic cases and previous reports, are mainly due to the overcharging of Au nanoparticle that produces a surface activation state in terms of high-energy plasma. This work therefore brings about new observations for both a single and dual-nanocrystals system, as well as new insights in understanding the resulting dynamics behaviors. [ABSTRACT FROM AUTHOR]