[en] Graphical abstract: The bamboo-like nitrogen-doped carbon nanotubes provide abundant pores and conductive networks for facilitating the charge-transfer reaction and diffusion process in comparison with the carbon nanospheres for dye-sensitized solar cell. - Highlights: • N-doped carbon nanotubes are prepared by direct pyrolysis of Prussian blue analogue. • The pyrolysis temperature higher than 550 °C is required to obtain carbon nanotubes. • N-doped carbon spheres are obtained at a pyrolysis temperature of 500 °C. • Dye-sensitized solar cell with nanotube electrode shows a power efficiency of 7.48%. - Abstract: Nitrogen-doped carbon materials were prepared by direct pyrolysis of nanostructured Prussian blue analogue (metal hexacyanoferrates) without additional carbon sources and metal catalysts. The pyrolysis temperature played a crucial role in determining the structure of resultant carbon materials. Bamboo-like nitrogen-doped carbon nanotubes (NCNTs) could be formed at a pyrolysis temperature of 700 °C, while only the nitrogen-doped carbon spheres (NCNSs) were obtained at 500 °C. After removal of metal catalysts, the bamboo-like NCNTs exhibited superior electrocatalytic behavior towards I⁻/I₃⁻ than the hollow NCNSs, primarily due to their higher surface area and electrical conductivity in comparison with NCNSs. The photoelectron conversion efficiency of dye-sensitized solar cell (DSC) using NCNT counter electrode reached 7.48%, which was even better than that using Pt counter (7.12%) and much higher than that using NCNS counter (5.53%). The improved photovoltaic performance of DSC employing metal-free NCNT counter electrode was primarily attributed to the significantly reduced diffusion and charge-transfer resistances in porous NCNT catalyst layer in comparison with the compact NCNS electrode.

[en] Highlights: • Nickel hydroxide electrode with tailored nanocup architecture was fabricated. • Deposition time dominates the morphological evolution of catalyst layer. • Catalyst with nanocup arrays expedites the transport of ion, electron, and gas. • Cup-like pore arrays provide much more active sites for the electrolysis of urea. - Abstract: Nickel hydroxide electrode composed of cup-like pore arrays, which could act as an effective catalyst layer for electrolysis of urea, was formed on stainless steel foil by cathodic electrodeposition using a monolayer of polystyrene spheres as a template. The morphology of the catalyst layer could be controlled from nanocup to hollow sphere by tuning the deposition time. Electrolysis of urea was characterized by cyclic voltammetry and chronoamperometry in 1 M KOH electrolyte containing 0.33 M urea. The tailored catalyst layer with nanocup arrays expedited the transport of ion, electron, and gas. Moreover, cup-like pore arrays might lead to an increased surface area, and more active sites were exposed to electrolyte for the electrolysis of urea. Therefore, the nickel hydroxide electrode with nanocup architecture offered the benefit of much better electrocatalytic performance than the film electrode and hollow-sphere electrode during electrolysis of urea

[en] Highlights: • Electrochemical process can purify the urea-rich wastewater, producing hydrogen gas. • Carbon-encapsulated nickel iron nanoparticles (CE-NiFe) are prepared by pyrolysis. • An ultra-thin layer of CE-NiFe nanoparticles is attached to the 3D Ni foam. • CE-NiFe nanoparticles escalate both the urea electrolysis and hydrogen evolution. - Abstract: A cyanide-bridged bimetallic coordination polymer, nickel hexacyanoferrate, could be pyrolyzed to form carbon-encapsulated nickel-iron (CE-NiFe) nanoparticles. The formation of nitrogen-doped spherical carbon shell with ordered mesoporous structure prevented the structural damage of catalyst cores and allowed the migration and diffusion of electrolyte into the hollow carbon spheres. An ultra-thin layer of CE-NiFe nanoparticles could be tightly attached to the three-dimensional macroporous nickel foam (NF) by electrophoretic deposition. The CE-NiFe nanoparticles could lower the onset potential and increase the current density in anodic urea electrolysis and cathodic hydrogen production as compared with bare NF. Macroporous NF substrate was very useful for the urea electrolysis and hydrogen production, which allowed for fast transport of electron, electrolyte, and gas products. The superior electrocatalytic ability of CE-NiFe/NF electrode in urea oxidation and water reduction made it favorable for versatile applications such as water treatment, hydrogen generation, and fuel cells.

[en] Graphical abstract: Nickel cobaltite nanograss with bimodal pore size distribution is grown around the carbon nanotube-wrapped stainless steel wire mesh as a high capacitance and stable electrode for high-performance and flexible supercapacitors. - Highlights: • NiCo₂O₄ nanograss with bimodal pore size distribution is hydrothermally prepared. • Carbon nanotubes (CNTs) wrap around stainless steel (SS) wire mesh as a scaffold. • NiCo₂O₄ grown on CNT-wrapped SS mesh shows excellent capacitive performance. • Porous CNT layer allows for rapid transport of electron and electrolyte. - Abstract: Nickel cobaltite nanograss with bimodal pore size distribution (small and large mesopores) is grown on various electrode substrates by one-pot hydrothermal synthesis. The small pores (<5 nm) in the nanograss of individual nanorods contribute to large surface area, while the large pore channels (>20 nm) between nanorods offer fast transport paths for electrolyte. Carbon nanotubes (CNTs) with high electrical conductivity wrap around stainless steel (SS) wire mesh by electrophoresis as an electrode scaffold for supporting the nickel cobaltite nanograss. This unique electrode configuration turns out to have great benefits for the development of supercapacitors. The specific capacitance of nickel cobaltite grown around CNT-wrapped SS wire mesh reaches 1223 and 1070 F g⁻¹ at current densities of 1 and 50 A g⁻¹, respectively. CNT-wrapped SS wire mesh affords porous and conductive networks underneath the nanograss for rapid transport of electron and electrolyte. Flexible CNTs connect the nanorods to mitigate the contact resistance and the volume expansion during cycling test. Thus, this tailored electrode can significantly reduce the ohmic resistance, charge-transfer resistance, and diffusive impedance, leading to high specific capacitance, prominent rate performance, and good cycle-life stability.

[en] The classical solutions for straight disclinations in an infinite elastic solid have been obtained by integrating the results for disclination densities. In this paper, the equilibrium equations are solved directly for straight twist and wedge disclinations, subject to the boundary conditions of the defects and rigid body translations/rotations. For a twist or wedge disclination in an infinite solid, the current solutions, based on a core fixed at a point to remove rigid body motion, differ from the classical ones by the constant $-<!--\; ???\; -->\text{log }{r}_i$, where $r_i$ is the radius of the disclination core. For a wedge disclination in an infinitely long cylinder, additional terms of the form 1 / r in the radial displacement and $1/r^2$ in the stresses appear in the solutions. The dependence of the current and classical results on the Lamé constants highlights significant differences near the disclination line, which will impact studies of disclination relaxation such as crack nucleation and core amorphization. The energy of a singular wedge disclination in a cylinder without a core mostly underestimates that of a wedge disclination with a core.

[en] An effective method for preparing tungsten carbide coating on diamond surfaces was proposed to improve the interface bonding between diamond and copper. The WC coating was formed on the diamond surfaces with a reaction medium of WO_3 in mixed molten NaCl–KCl salts and the copper–diamond composites were obtained by vacuum pressure infiltration of WC-coated diamond particles with pure copper. The microstructure of interface bonding between diamond and copper was discussed. Thermal conductivity and thermal expansion behavior of the obtained copper–diamond composites were investigated. Results indicated that the thermal conductivity of as-fabricated composite reached 658 W m"− "1 K"− "1. Significant reduction in coefficient of thermal expansion of the composite compared with that of pure copper was obtained. - Highlights: • WC coating was successfully synthesized on diamond particles in molten salts. • WC coating obviously promoted the wettability of diamond and copper matrix. • WC coating greatly enhanced the thermal conductivity of Cu–diamond composite. • The composites are suitable candidates for heat sink applications

[en] In this paper, the entanglement of two moving atoms induced by a single-mode field via a three-photon process is investigated. It is shown that the entanglement is dependent on the category of the field, the average photon number N, the number p of half-wave lengths of the field mode and the atomic initial state. Also, the sudden death and the sudden birth of the entanglement are detected in this model and the results show that the existence of the sudden death and the sudden birth depends on the parameter and the category of the mode field. In addition, the three-photon process is a higher order nonlinear process. (general)

[en] Isotopic separation was observed during ablation of standard copper samples by a nanosecond Nd-YAG laser and a femtosecond Ti:sapphire laser at 266 nm. A time-of-flight mass spectrometer, orthogonal to the direction of the laser plume, was used to measure the isotopic composition of the plasma. A voltage was applied to the pulser at different delay times after the laser was ired in order to obtain a temporal profile as the plume expanded. The fraction of ⁶³Cu in the plasma detected by the mass spectrometer reaches a maximum of 0.83 at 6 US and 3 μs after the laser is fired for the nanosecond and femtosecond lasers respectively, before falling back to the natural abundance ratio of 0.69. As reported in the literature, the ion peaks are centered at two different delay times, representing fast and slow ion energy distributions. A mechanism based on the electric ield interactions between the electrons and ions is proposed to explain the separation of isotopes in the plume.

[en] Pillar-like mesoporous carbon doped with oxygen and sulfur heteroatoms was obtained through thermal pyrolysis of a zinc-based metal-organic framework, Zn-BTC (BTC = 1,3,5-benzenetricarboxylic acid), followed by acid treatment and sulfurization. The pillar morphology remained after acid etching and sulfur doping, while the content of disordered carbon and the structural defects were significantly increased, resulting in an increase in the electroactive sites for catalyzing the iodide/triiodide ions. In addition, the incorporation of sulfur heteroatoms into carbon frameworks could cause the reduction of oxygen-doped carbon pillars, improving the apparent electrocatalytic activity. The cyclic voltammetry and electrochemical impedance spectroscopy showed that the oxygen and sulfur dual-doped (OS-doped) carbon electrode has better electrocatalytic performance than the single oxygen doped (O-doped) carbon electrode, probably owing to the sulfur doping in carbon matrix that offered abundant electroactive site for boosting the iodide/triiodide redox shuttle. Dye-sensitized solar cell employing OS-doped carbon exhibited power conversion efficiency of 10.2%, greater than that using Pt (9.4%), O-doped carbon (8.0%), and ZnO-doped carbon (7.7%).

[en] Highlights: •Mo₂C layers were successfully synthesized on diamond particles in molten salts. •Mo₂C layers obviously promoted the wettability of diamond and copper matrix. •Mo₂C layers greatly enhanced the thermal conductivity of Cu-diamond composites. •The obtained composite is suitable for electronic packaging materials. -- Abstract: Molybdenum carbide (Mo₂C) coated diamond particles were prepared by molten salts method and the copper–diamond composites were obtained by vacuum pressure infiltration of Mo₂C-coated diamond particles with pure copper. The formation mechanism of the Mo₂C layers was investigated, and the microstructure, thermal conductivity and thermal expansion behavior of the obtained copper–diamond composites were studied. The coated layers were formed by using a reaction medium of MoO₃ in mixed molten salts, and the formation mechanism of the Mo₂C layers on diamond particles was investigated. The result indicates that the formation of Mo₂C layers occurred in two steps, that is, the reduction of MoO₃ to MoO₂ and the reduction of MoO₂ to Mo₂C. The wettability between diamond particles and copper was effectively improved, and the relative density of the copper–diamond composites achieved 99.5%. The thermal conductivity reached 596 W m⁻¹ K⁻¹, and the coefficient of thermal expansion was 7.15 × 10⁻⁶ K⁻¹ of the composites with 60 vol.% Mo₂C-coated diamond. This composite is expected to be suitable for electronic packaging applications