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Nb14W3O44, a promising electrode material of lithium-ion batteries/capacitors, was prepared using a solid-state method. Its geometrical structure, phase diagram, and thermal expansion properties were all thoroughly investigated. The material has a tetragonal structure and an intriguing linear negative thermal expansion (NTE) property with an impressive coefficient of thermal expansion (−4.27 × 10−6 K−1, 300–433 K). The NTE phenomenon can be attributed to the vibrations of the bridge-site atoms, which caused the coupling rotation of the rigid unit models. The lattice distortion, and pores could also affect the thermal expansion performance in the bulk materials.

From the perspective of treating wastes with wastes, bamboo sawdust was integrated with a hydroxyapatite (HAP) precursor to create engineered nano-HAP/micro-biochar composites (HBCs) by optimizing the co-precipitated precursor contents and co-pyrolysis temperature (300, 450, 600 °C). The physicochemical properties of HBCs, including morphologies, porosities, component ratios, crystalline structures, surface elemental chemical states, surface functional groups, and zeta potentials as a function of carbonization temperatures and components of precursors, were studied. Biochar matrix as an efficient carrier with enhanced specific surface area to prevent HAP from aggregation was desired. The sorption behavior of heavy metal (Cu(II), Cd(II), and Pb(II)) and pharmaceuticals (carbamazepine and tetracycline) on HBCs were analyzed given various geochemical conditions, including contact time, pH value, ionic strength, inferencing cations and anions, coexisting humic acid, and ambient temperature. HBCs could capture these pollutants efficiently from both simulated wastewaters and real waters. Combined with spectroscopic techniques, proper multiple dominant sorption mechanisms for each sorbate were elucidated separately. HBCs presented excellent reusability for the removal of these pollutants through six recycles, except for tetracycline. The results of this study provide meaningful insight into the proper integration of biochar–mineral composites for the management of aquatic heavy metals and pharmaceuticals.

Mg2Si/Si nanocomposites, consisting of Si nanosheet bundles and Mg2Si deposits formed on the Si nanosheet bundles, were formed by the thermal annealing of CaSi2 powders in MgCl2 vapor. Mg atoms are deposited on the Si nanosheet bundles, and the surface of the nanosheets were partially transformed into the Mg2Si phase during the thermal treatment. The Mg2Si/Si composites were also synthesized on Si(111) substrates. The structural and photoluminescence (PL) properties of the composites were characterized. The Mg2Si deposits were inhomogeneously distributed on the Si nanosheets. Furthermore, the Si-based nanosheets consisted of disordered thinner Si layers, and a disordered superlattice-like layered structural model is shown. The PL emissions in the visible region were clearly observed, and the temperature and the excitation intensity dependences of the emissions were characterized. It was found that the structural modification of the Si nanosheet bundles to form the composites with Mg2Si deposits affected the emission property of the Si nanosheets. The luminescence mechanism of the composite was discussed. [ABSTRACT FROM AUTHOR]

Si-based nanosheet bundles were synthesized by the extraction of Ca atoms from CaSi2 microwalls grown on Si substrates by inositol hexakisphosphate solution or thermal treatment in FeCl2 vapor. The structural and photoluminescence properties of the Si-based nanosheet bundles were examined. The photoluminescence emissions in the visible region were clearly observed, and the temperature and excitation intensity dependences of the emissions were characterized. The observed Si-based nanosheets consist of thin Si layers, and a superlattice-like layered structural model is proposed to describe the Si-based nanosheet bundle structures and their photoluminescence property. The photoluminescence property of the nanosheets significantly depends on their treatment process. The luminescence mechanism of the nanosheets was discussed. [ABSTRACT FROM AUTHOR]

The flowerlike Si nanostructures rooted on Si(111) substrates were synthesized using MnCl2 and Si sources by chemical vapor deposition (CVD). These nanostructures consist of thin Si(111) sheets with a thickness of about 100 nm or less. Their structural properties were clarified in detail by transmission electron microscopy (TEM). Their photoluminescence (PL) measurements revealed that the band edge emission of Si clearly appeared, and dislocation-related emissions were hardly observed. PL spectra showed a thermally stimulated emission with an activation energy of 19 meV in the temperature range between 100 and 200 K. These results suggest that exciton and/or carrier trap centers exist inside the flowerlike Si nanostructures. It is expected that the nanostructures can be used for the improvement of energy devices. [ABSTRACT FROM AUTHOR]

Crystalline Si-based nanosheets were successfully synthesized from CaSi2 by a simple soft chemical synthetic method in solution. By immersing CaSi2 powder or CaSi2/Si substrates in an inositol hexakisphosphate (IP6) solution, Ca atoms were extracted from the CaSi2 particles, then Si-based nanosheets were formed. The morphological, structural and optical properties of the Si-based nanosheets were investigated. It is noted that the thin Si-based nanosheets stacked with a void space formed bundle structures, and the nanosheets were easily exfoliated from the bundles to expose the surfaces corresponding to the Si{111} planes. Meanwhile, the surface of the Si nanosheets might be terminated by O, H, or OH bonds. The Si-based nanosheet bundles were then formed and directly rooted to the Si(111) substrates, and had a remarkably highly symmetrical morphology. This study demonstrated a simple method for preparing Si-based nanosheets, and electro- and photo-chemical applications would possibly be expected, such as in lithium ion batteries. [ABSTRACT FROM AUTHOR]