[en] Phase selective synthesis is particularly valuable in revealing performance of photocatalyst existing as several polymorphic phases. In this work, we develop a general soft chemical route that used a TiO₂ (B) nanosheet as a precursor to synthesize TiO₂ nanostructures of desired phase. Benefiting from the structural similarity and ultrathin thickness feature, TiO₂ (B) nanosheet precursor can readily transform to pure phase of anatase, rutile and brookite as well as mixed phase of brookite/anatase. A possible dissolution-recrystallization mechanism is proposed for the phase transition of TiO₂ (B) nanosheets to other phases. Photocatalytic activity tests demonstrated that the brookite/anatase mixture had the highest activity in degrading acetaldehyde under UV light irradiation, due to the synergistic effect of high crystallinity, large surface area and mixed phase structure.

[en] The paper proposes a new piezoelectric smart structure with the integrated passive/active vibration-reduction performances, which is made of a series of periodic structural units. Every structural unit is made of two layers, one is an array of piezoelectric bimorphs (PBs) and one is an array of metal beams (MBs), both are connected as a whole by a metal plate. Analyses show that such a periodic smart structure possesses two aspects of vibration-reduction performance: one comes from its phonon crystal characteristics which can isolate those vibrations with the driving frequency inside the band gap(s). The other one comes from the electromechanical conversion of bent PBs, which is actively aimed at those vibrations with the driving frequency outside the band gap(s). By adjusting external inductance, the equivalent circuit of the proposed structure can be forced into parallel resonance such that most of the vibration energy is converted into electrical energy for dissipation by a resistance. Thus, an external circuit under the parallel resonance state is equivalent to a strong damping to the interrelated vibrating structure, which is just the action mechanism of the active vibration reduction performance of the proposed smart structure. (paper)

[en] Structural evolution of olefin during its heating process was observed with SAXS method at Beijing Synchrotron Radiation Facility. The mean square fluctuation of electron density increased from 468.5 nm^-2 at 22 degree C to 2416 nm^-2 at 100 degree C, while the electronic gyration radius decreased from 11.61 nm at 22 degree C to 11.16 nm at 100 degree C. Therefore, the olefin softens as a result of the increased thermal motion of the molecules, rather than the shrinking size of fundamental structural units of olefin. (authors)

[en] Phase-change materials (PCMs) that can reversibly transit between crystalline and amorphous phases have been widely used for data-storage and other functional devices. As PCMs scale down to nanoscale, the properties and transition procedures can vary, bringing both challenges and opportunities in scalability. This article describes the physical structures, properties and applications of nanoscale phase-change materials and devices. The limitations and performance of scaling properties in phase-change materials and the recent progress and challenges in phase-change devices are presented. At the end, some emerging applications related to phase-change materials are also introduced. (topical review)

[en] Highlights: • 1The EC unit removed 98.3% turbidity, 78.5% TOC and 56.5% Ca²⁺, respectively. • The optimum operating conditions were recommended as 318 A/m², 20 min for reaction time, and 4.4 for initial pH. • The operating cost under the proposed conditions was 0.80 US$/m³. Shale gas drilling wastewater is a challenging waste stream generated in gas industries. It is a mixture of different organic and inorganic compounds. Treatment of this complex wastewater relies on a suitable technology for the removal of small suspended particles and dissolved elements. This study employed electrocoagulation (EC) as an efficient method for shale gas drilling wastewater pretreatment. The optimum operating conditions for turbidity, TOC, and Ca²⁺ removal were determined using a response surface methodology (RSM). The chloride (Cl⁻) removal and residual iron of effluent in the EC process were also tested and evaluated. Based on the analysis of variance (ANOVA), the coefficient of determination (R²) was calculated and found to be above 0.86 for all the responses. The maximum removal efficiencies were found to be around 98.3%, 78.5%, and 56.5% for turbidity, TOC, and Ca²⁺ removal under the optimum conditions, respectively. In order to treat drilling wastewater by EC process both efficiently and economically, the following operating parameters are recommended: 318 A/m² for current density, 20 min for reaction time and 4.4 for initial pH. A total operation cost of 0.80 US$/m³ was estimated under these conditions.

[en] The synthesis of graphene (GR) from graphene oxide (GO) typically involves harmful chemical reducing agents that are undesirable for most practical applications. Here we report a green and facile synthesis method for the synthesis of GR that is soluble in water and organic solvents and that includes the additional benefit of adsorption of heavy metal ions. Acetylacetone, as both a reducing agent and a stabilizer, was used to prepare soluble GR from GO. Transmission electron microscopy and atomic force microscopy provide clear evidence for the formation of few-layer GR. The results from Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopy show that reduction of GO to GR has occurred. Raman spectroscopy and X-ray photoelectron spectroscopy also indicate the removal of oxygen-containing functional groups from GO, resulting in the formation of GR. The results of dispersion experiments show that GR can be highly dispersed in water and N,N-Dimethylformamide. The reaction mechanism for acetylacetone reduction of exfoliated GO was also proposed. This method is a facile and environmentally friendly approach to the synthesis of GR and opens up new possibilities for preparing GR and GR-based nanomaterials for large-scale applications. Of even greater interest is that inductively coupled plasma atomic emission spectroscopy suggests that synthesized GR may be applied in the absorption of Cd²⁺ and Co²⁺ due to the strong coordination capacity of acetylacetone on the surfaces and edges of GR and the large surface area of GR in aqueous solutions. The maximum adsorptions are 49.28 mg g⁻¹ for Cd²⁺, which is 4.5 times higher than that of carbon nanotubes, and 27.78 mg g⁻¹ for Co²⁺, which is 3.6 times higher than that of titania beans. (paper)

[en] Highlights: ► Ni doped nc-CrAlN/a-SiN_x nanocomposite is synthesized via magnetron sputtering. ► Microstructure evolution of Ni doped nc-CrAlN/a-SiN_x is revealed. ► Toughening effect of Ni on hard nc-CrAlN/a-SiN_x nanocomposite is investigated. - Abstract: To combat the brittleness of hard nc-CrAlN/a-SiN_x nanocomposite (nc-: nanocrystalline, a-: X-ray amorphous), different Ni content (from 0 to 39.8 at.%) is doped via magnetron sputtering. Glancing Angle X-ray Diffractometry, X-ray photoelectron spectroscopy, Field Emission Scanning Electron Microscopy and Transmission Electron Microscopy are employed to investigate the microstructural evolution. With increased Ni, the grain size decreases accompanied with morphology change, from dense glassy to coarse columns. With 4.2 at.% Ni, scratch toughness of nc-CrAlN/a-SiN_x hard nanocomposite (28 GPa) is improved by around 200% at expense of only 18% hardness.

[en] Controllable regulation of cell behavior is one of the most important factors conducive to the restoration of tissue functions. Recently, various strategies have been developed using physical or chemical cues. Although these techniques are effective, the high cost and complex fabrication procedures impede their application. In this study, we used a low cost and simple strategy to fabricate PVA/silk fibroin composite hydrogels using a cyclic freeze-thaw method. With the increase of freeze-thaw cycles, the pore size of hydrogels decreased, the elastic modulus increased, and the swelling rate decreased. Furthermore, we chose two shapes of model cells, a spindle using bone marrow mesenchymal stem cells and smooth muscle cells, and a round shape using BV2 microglial cells. PVA/silk fibroin composite hydrogels inhibited the adhesion and proliferation of stem cells and muscle cells and changed their cell shape from spindle to round, maintained the initial round shape of BV2 microglial cells, and promoted the proliferation of BV2 microglial cells. These results demonstrate that PVA/silk fibroin composite hydrogels can be used as a novel hydrogel system to regulate cell behavior. (paper)

[en] Highlights: • Asymmetricplasmonic structures with dual functionalities of water purification and pollution detection is formed by a self-assembly process. • The dark porousside of the APS can enable efficient solar steam generation (with energy transfer efficiency ~ 80%). • The shiny metallic side can enable sensitive chemicals detection (with detection limit down to ~ 10–12M). • This dual functional APS can enable on-site pollution detection and purification of water, with long time durable performance up to ~ 45 days. In the past decade, various rational designed plasmonic structures have demonstrated extraordinary functionalities from information, photothermal therapy to solar energy conversion. Recently, plasmon enhanced solar steam generation is attracting a lot of attention for its great potential in desalination, sterilization, etc. Here for the first time we demonstrate an asymmetric plasmonic structure (APS) formed by self-assembly of close packed silver nanoparticles into porous templates with dual functions, solar water purification and pollution detection. The dark porous side of the APS can enable efficient solar steam generation (with energy transfer efficiency ~ 80%) while the shiny metallic side can enable sensitive chemicals detection (with detection limit down to ~ 10^–12 M). Such impressive performance in solar thermal conversion and chemical sensing are stemmed from the broadband and efficient light absorption (solar absorptivity > 90%) as well as pronounced local field enhancement (maximal enhancement factor ~ 10⁹), respectively. As an example of functional integration, this dual functional APS can enable on-site pollution detection and purification of water: water sources contaminated with various kinds of common pollutants have been examined and purified. Both functions of detection and purification exhibit long time durable performance up to ~ 45 days, with < 20% decay in Raman intensity and < 10% decay in energy transfer efficiency, respectively.

[en] Vanadium nitride (VN) is easily oxidized to form vanadium oxides and becomes lubricious under stress. CrAlN is hard thus CrAlN/VN multilayer coatings render both hardness and lubricious properties attractive in dry machining of soft metals. This study investigates the effect of multi-layering on the coating's mechanical and tribological properties at room temperature. The CrAlN/VN multilayer coatings are deposited on cemented tungsten carbide and Si wafer (1 0 0) substrates in an in-line magnetron sputtering system. A period contains one layer of CrAlN plus one adjacent layer of VN. The period thickness varies roughly from 3 nm to 30 nm; the total number of the periods varies from 30 to 300. X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and electron probe micro-analyzer are employed to characterize the microstructures and chemistry. Nanoindentation and ball-on-disk wear test are used in mechanical and tribological studies. The CrAlN/VN multilayer coatings have good lubricant property with lowest coefficient of friction of 0.26. At the period thickness of 20 nm, the multilayer coatings obtained the best mechanical properties (hardness of 32.4 GPa, elastic modulus of 375 GPa, minimum wear rate of 1.1 × 10⁻⁷ mm³/Nm).