Controllable sliding transfer of wafer‐size graphene

The innovative design of sliding transfer based on a liquid substrate can succinctly transfer high‐quality, wafer‐size, and contamination‐free graphene within a few seconds. Moreover, it can be extended to transfer other 2D materials. The efficient sliding transfer approach can obtain high‐quality and large‐area graphene for fundamental research and industrial applications

Minimum-Fuel Ascent of Hypersonic Vehicle considering Control Constraint Using the Improved Pigeon-Inspired Optimization Algorithm

Trajectory optimization problem for hypersonic vehicles has long been recognized as a difficult problem. This paper brings control constraints into the trajectory optimization to make the optimal trajectory meet the requirements of control performance. The strong nonlinear characteristic of the ascent phase aerodynamics makes the trajectory optimization problem difficult to be solved by the optimal control theory. A trajectory optimization algorithm based on the improved pigeon-inspired optimization (PIO) algorithm is proposed to solve the complex trajectory optimization problem under multiple constraints. To overcome the obstacle of premature convergence and deceptiveness, the evolutionary strategy of qubit in quantum evolutionary algorithm (QEA) is introduced into the PIO to maintain population diversity and judge the optimal solution. To handle constraints, the penalty function is used to construct the fitness function. The optimal ascent trajectory is obtained by utilizing the improved PIO algorithm. Then, the trajectory inverse algorithm is used to verify the feasibility of the optimal trajectory to ensure that a feasible optimal trajectory is obtained. The comparison results show that the proposed algorithm outperforms particle swarm optimization (PSO) and standard PIO on trajectory optimization. Meanwhile, the simulation result shows that the performance of the optimal ascent trajectory with control constraints is improved and the trajectory is feasible. Therefore, the method is potentially feasible for solving the ascent trajectory optimization problem under control constraint for hypersonic vehicles

Fluorination and electrical conductivity of BN nanotubes

Fluorination of BN nanotubes has been performed using a catalytic growth method, which leads to the appearance of markedly curved fluorine-doped BN sheets and converts originally insulating BN nanotubes to semiconductors, as confirmed by the comparative electron transport four-probe measurements on doped and undoped individual BN nanotubes

Multifunctional Freestanding Microprobes for Potential Biological Applications

Deep-level sensors for detecting the local temperatures of inner organs and tissues of an animal are rarely reported. In this paper, we present a method to fabricate multifunctional micro-probes with standard cleanroom procedures, using a piece of stainless-steel foil as the substrate. On each of the as-fabricated micro-probes, arrays of thermocouples made of Pd–Cr thin-film stripes with reliable thermal sensing functions were built, together with Pd electrode openings for detecting electrical signals. The as-fabricated sword-shaped freestanding microprobes with length up to 30 mm showed excellent mechanical strength and elastic properties when they were inserted into the brain and muscle tissues of live rats, as well as suitable electrochemical properties and, therefore, are promising for potential biological applications

Growth of Uniform Monolayer Graphene Using Iron-Group Metals via the Formation of an Antiperovskite Layer

It has been generally accepted that iron-group metals (iron, cobalt, nickel) consistently show the highest catalytic activity for the growth of carbon nanomaterials, including carbon nanotubes (CNTs) and graphene. However, it still remains a challenge for them to obtain uniform graphene, because of their high carbon solubility, which can be attributed to an uncontrollable precipitation in cooling process. The quality and uniformity of the graphene grown on low-cost iron-group metals determine whether graphene can be put into the mass productions or not. Here, we develop a novel strategy to form an antiperovskite layer using ambient-pressure chemical vapor deposition (APCVD), which, so far, is the only known way for iron-group metals to prepare uniform monolayer graphene with 100% surface coverage. Our strategy utilizes liquid metal (e.g., gallium) to assist iron-group metals to form an antiperovskite layer that is chemically stable throughout the high-temperature growth process and then to seal the passageway of carbon segregation from the metal bulk during cooling. With the advantage of forming antiperovskite structure, the uniform monolayer graphene can always be obtained under the variations of experimental conditions. Our strategy solves the problem about how to get uniform graphene film on high-solubility carbon substrate, to utilize the high catalytic activity of low-cost iron-group metals and to realize low-temperature growth by chemical vapor deposition

Iodine-Mediated Chemical Vapor Deposition Growth of Metastable Transition Metal Dichalcogenides

Iodine-Mediated Chemical Vapor Deposition Growth of Metastable Transition Metal Dichalcogenide

Isotropic Growth of Graphene toward Smoothing Stitching

The quality of graphene grown via chemical vapor deposition still has very great disparity with its theoretical property due to the inevitable formation of grain boundaries. The design of single-crystal substrate with an anisotropic twofold symmetry for the unidirectional alignment of graphene seeds would be a promising way for eliminating the grain boundaries at the wafer scale. However, such a delicate process will be easily terminated by the obstruction of defects or impurities. Here we investigated the isotropic growth behavior of graphene single crystals via melting the growth substrate to obtain an amorphous isotropic surface, which will not offer any specific grain orientation induction or preponderant growth rate toward a certain direction in the graphene growth process. The as-obtained graphene grains are isotropically round with mixed edges that exhibit high activity. The orientation of adjacent grains can be easily self-adjusted to smoothly match each other over a liquid catalyst with facile atom delocalization due to the low rotation steric hindrance of the isotropic grains, thus achieving the smoothing stitching of the adjacent graphene. Therefore, the adverse effects of grain boundaries will be eliminated and the excellent transport performance of graphene will be more guaranteed. What is more, such an isotropic growth mode can be extended to other types of layered nanomaterials such as hexagonal boron nitride and transition metal chalcogenides for obtaining large-size intrinsic film with low defect