Enhanced Catalytic Activity of Carbon Nanotubes for the Oxidation of Cyclohexane by Filling with Fe, Ni, and FeNi alloy Nanowires

Fe-, Ni-, and alloyed FeNi-filled carbon nanotubes (Fe@CNT, Ni@CNT, and FeNi@CNT) were prepared by a general strategy using a mixture of xylene and dichlorobenzene as carbon source, and ferrocene, nickelocene, and their mixture as catalysts. By tailoring the composition of the carbon precursor, the filling ratio and the wall thickness of metal@CNT could be controlled. For the catalytic oxidation of cyclohexane in liquid phase with molecular oxygen as oxidant, the highest activity was obtained over Fe@CNT synthesized from pure dichlorobenzene. However, Ni filling did not improve the activity of CNTs. The effects of metal filling, wall thickness, and defects on catalytic activity were investigated to determine the structure-activity relationship of the filled CNTs. The enhanced catalytic performance can be attributed to a combined contribution of thin walls of CNTs and confined electron-donating metals, which are favourable to electron transfer on the surfaces of CNTs. The modification of the electronic structure of CNTs upon Fe and Ni fillers insertion was elucidated through density functional theory calculations

Controlled growth of epitaxial wurtzite BeMgZnO alloy films and two microscopic origins of Be-Mg mutual stabilizing mechanism

A narrow growth window for high quality BeMgZnO quaternary alloy films was discovered. The key for this growth window is to keep the Be/Mg atomic ratio low. Here we examine this growth window in more detail and specify the optimum Be/Mg ratio, which is between 0.2 and 0.4. Within this region, the doping level and band-gap can be tuned in a wide range with constant crystal quality, which is certainly favorable to ZnO-based bandgap engineering. More importantly, we discuss the microscopic origins of this growth window to unveil the Be-Mg mutual stabilization mechanism. Our semi-quantitative analysis demonstrates that lattice mismatch compensation between Mg2+ and Be2+ and the strong fourfold coordination preference of Be2+ are two major origins. We have clarified that the upper limit of the growth window is determined by the lattice mismatch and the lower limit is determined by the coordination number (CN) preference, which use the new criterion parameter delta to take both ionic and covalent bond into account under the frame of Pauling's Rules. We believe that Mg can alleviate the serious lattice mismatch due to Be incorporation and Be can reversely relieve the ionic CN6 anxiety due to Mg incorporation. That is the way they stabilize each other and come to a balance. Our research provides a better insight into the stability of BeMgZnO alloys and a very meaningful way to design and engineer this quaternary alloys. (C) 2015 Elsevier B.V. All rights reserved

Growth of vertically aligned ZnO nanowire arrays on ZnO single crystals

Vertically aligned ZnO nanowire arrays were grown on ZnO single crystals using a chemical vapor deposition method. Nucleation sites were defined by patterning Au nanodot catalysts fabricated through anodized aluminum oxide (AAO) templates. Morphology and structure characterizations showed that the as-grown nanowires had the single-crystal hexagonal wurtzite structure with a <0001 > growth direction. By changing the pore distance of AAO, the density of nanowires could be well controlled. A sharp peak in the UV region and a weak broad peak in the visible region were shown in the room temperature photoluminescence spectra, suggesting the high-quality ZnO nanowire arrays were obtained. (C) 2015 Elsevier B.V. All rights reserved

Magnetic and Highly Recyclable Macroporous Carbon Nanotubes for Spilled Oil Sorption and Separation

Development of sorbent materials with high selectivity and sorption capacity, easy collection and recyclability is demanding for spilled oil recovery. Although many sorption materials have been proposed, a systematic study on how they can be reused and possible performance degradation during regeneration remains absent. Here we report magnetic carbon nanotube sponges (Me-CNT sponge), which are porous structures consisting of interconnected CNTs with rich Fe encapsulation. The Me-CNT sponges show high mass sorption capacity for diesel oil reached 56 g/g, corresponding to a volume sorption capacity of 99%. The sponges are mechanically strong and oil can be squeezed out by compression. They can be recycled using through reclamation by magnetic force and desorption by simple heat treatment. The Me-CNT sponges maintain original structure, high capacity, and selectivity after 1000 sorption and reclamation cycles. Our results suggest that practical application of CNT macrostructures in the field of spilled oil recovery is feasible

Engineering superlyophobic surfaces on curable materials based on facile and inexpensive microfabrication

This paper proposes a facile, versatile, and low-cost approach for batch production of engineered superlyophobic surfaces (SLSs, simultaneously superhydrophobic and superoleophobic) on various curable materials. Based on the soft replication using poly(dimethylsiloxane) (PDMS) as the intermediate mold, T-shaped overhang microstructures on Si and dual-resist masters have been transferred to curable materials including poly(methyl methacrylate) (PMMA), PDMS and glass resin. The as-fabricated polymer SLS replicas exhibit high structure fidelity, comparable nonwettability and excellent reproducibility for both water and oil during the 10 × 10 replication and possess new features such as tunable transparency. The proposed microfabrication approach for SLSs decouples the material and process dependence, greatly dilutes the fabrication cost and enables high-performance SLSs on a wide range of materials, which may initialize the broad applications of engineered SLSs for various low-contamination, low-adhesion and self-cleaning requirements in academy, industry and daily life. © 2014 the Partner Organisations

3D Printing Technologies for Flexible Tactile Sensors toward Wearable Electronics and Electronic Skin

3D printing has attracted a lot of attention in recent years. Over the past three decades, various 3D printing technologies have been developed including photopolymerization-based, materials extrusion-based, sheet lamination-based, binder jetting-based, power bed fusion-based and direct energy deposition-based processes. 3D printing offers unparalleled flexibility and simplicity in the fabrication of highly complex 3D objects. Tactile sensors that emulate human tactile perceptions are used to translate mechanical signals such as force, pressure, strain, shear, torsion, bend, vibration, etc. into electrical signals and play a crucial role toward the realization of wearable electronics and electronic skin. To date, many types of 3D printing technologies have been applied in the manufacturing of various types of tactile sensors including piezoresistive, capacitive and piezoelectric sensors. This review attempts to summarize the current state-of-the-art 3D printing technologies and their applications in tactile sensors for wearable electronics and electronic skin. The applications are categorized into five aspects: 3D-printed molds for microstructuring substrate, electrodes and sensing element; 3D-printed flexible sensor substrate and sensor body for tactile sensors; 3D-printed sensing element; 3D-printed flexible and stretchable electrodes for tactile sensors; and fully 3D-printed tactile sensors. Latest advances in the fabrication of tactile sensors by 3D printing are reviewed and the advantages and limitations of various 3D printing technologies and printable materials are discussed. Finally, future development of 3D-printed tactile sensors is discussed

The modulation of grain boundary barrier in ZnMgO/ZnO heterostructure by surface polar liquid

Modulation of grain boundary barrier in ZnO layer by polar liquid, was investigated in ZnMgO/ZnO heterostructures grown by plasma- assisted molecular beam epitaxy. Traditionally, surface adsorbates can only affect the surface atoms or surface electronic states. However, it was found that the electronic conduction property of ZnO far from the surface could be tailored obviously by the polar liquid adsorbed on the ZnMgO surface. Physically, this phenomenon is supposed to be caused by the electrostatical couple between the liquid polarity and the grain boundary barrier in the ZnO layer through crystal polarization field