Narrow Results

We describe variations in the structure and formation mechanism of alumina nanowires (ANWs) formed from porous anodic alumina (PAA) membranes, depending on the composition of the etching solution. Two types of ANWs were synthesized by etching PAA membranes in etching solutions containing H₃PO₄ or NaOH. Not only did the ANW formation mechanism vary, but also the morphological properties and the surface chemical composition of the ANWs varied with the etching solution used. These results suggest that the ANW surfaces may be optimized by the appropriate selection of etching solution. The optimization of ANWs may potentially advance, for example, water purification technological developments because ANWs have, in recent studies, provided more effective filtration performances than nanoporous alumina membrane filters.

In this paper, Nitinol, an equiatomic binary alloy of nickel and titanium, was surface modified for its potential biomedical applications by chemical and electrochemical etching. The main objective of the surface modification is to reduce the nickel content on the surface of Nitinol and simultaneously to a rough surface microstructure. As a result, better biocompatibility and better cell attachment would be achieved. The effect of the etching parameters was investigated, using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometry (EDX) and X-ray photoelectron spectrometry (XPS). The corrosion property of modified Nitinol surfaces was investigated by electrochemical work station. After etching, the Ni content in the surface layer has been reduced and the oxidation of Ti has been enhanced.

Alumina nanowires (ANWs) with high aspect ratios were synthesized by the chemical etching of porous alumina membranes (PAMs) in phosphoric acid solution. The morphology and structure of ANWs were analyzed by SEM and XRD, respectively. The results showed that the typical features of ANWs are around 35 nm in diameter and around 20 μm in length, the crystalline structure of the ANWs was amorphous, which was in accordance with that of the PAMs. Furthermore, the morphology of the PAMs was characterized by AFM and SEM in detail. On the basis of AFM and SEM observations, a possible formation mechanism of ANWs was discussed, and the inhomogeneous of the dissolution between the triple points and the side walls was considered to be the essential factor deciding the formation of ANWs.

Hierarchical alveolate structures in nano- to microscale were fabricated on both aluminum and stainless steel substrates via a chemical etching. On aluminum surfaces, sharp edged caves and plateaus were found. On stainless steel substrate, fine papillae stand on protuberances. These surfaces exhibit super-hydrophobic properties after the fluorination treatment, their water contact angles are 158° and 160°, respectively, with the contact angle hysteresis of about 5°. The roll off angle is about 5°. Ice melting behaviors on a plate of aluminum super-hydrophobic surface were compared with those on a hydrophilic one, their difference shows that the new feature of super-hydrophobic surface could be expected.

In the present study, a scalable-manufactured and environmental-friendly method was proposed to fabricate the superhydrophobic coating on titanium alloy. The hierarchical binary surface structures were obtained by hydrothermal treatment of titanium alloy with oxalic acid and sodium hydroxide solutions successively. The hierarchical structure surfaces after fluoroalkyl-silane modification possessed a maximum contact angle of 158.7^∘ and a sliding angle of 4.3^∘. The low contact angle hysteresis surface can lead to efficient self-cleaning performance, which was confirmed by the bounce and roll off of water droplet on the surface. Furthermore, the anticorrosion behaviors of the superhydrophobic coating in 3.5wt.% NaCl solution was evaluated by the electrochemical impedance spectroscopy (EIS). It was found that the superhydrophobic coating can maintain its superhydrophobic state (150^∘) within 48 h, thereby effectively preventing the corrosive medium from penetrating into the coating. This simple yet fast anti-corrosion/self-cleaning superhydrophobic coating manufacturing strategy will enlighten its potential application in the engineering fields.

In this paper, we report gold micro/nanostructures fabricated by a method called lithographically patterned nanostructure by chemical etching (LPNCE). In the LPNCE method, the photoresist layer, composed of pentaerythritol triacrylate (PETA, monomer) and isopropyl thioxanthone (ITX, photoinitiator), is dropped on gold film, and subsequently polymerized via two-photon absorption of 800 nm femtosecond laser. Micro/nanostructures are fabricated by the direct laser writing. The unpolymerized photoresist is washed by isopropanol, and the exposed gold is dissolved by KI₃ aqueous solution. Finally, polymers are removed by NaOH ethanol solution. Arbitrary 2D gold micro/nanostructures can be fabricated quickly by the direct laser writing and chemical etching method. The good electro-conductibility of these micro/nanostructures guarantees wide applications in micro-electronic devices, plasmonics and biosensors, etc.

Atomic force microscope (AFM) nanolithography was performed to create nanowire transistor pattern via local anodic oxidation process on surface of silicon-on-insulator (SOI) wafer. This nanoscale oxide pattern is used as a mask system for chemical etching to produce silicon nanowire transistor. The device with component structures of a silicon nanowire (SiNW) as channel with source, drain, and gate pads had been drawn at 9 V tip voltage, 6 μm/s writing speed with humidity 55.8–68.9%RH. The designed device was etched with tetramethylammonium hydroxide (TMAH) to remove uncovered silicon layer but oxide pattern remains. In order to obtain SiNW transistor, sample was etched using hydrogen fluoride (HF) to remove oxide layer. From the AFM and field emission scanning electron microscope (FESEM) observation found that the SiNW transistor with wire size of 92.65 nm in wire thickness, 90.83 nm wire width and 10.30 μm in length with contact pads size of about 5 μm × 5 μm has been successfully fabricated.

The control of ionic transportation inside the multi asymmetric conical nanopores in polyethylene terephthalate (PET) membrane was investigated. The conical nanopores were prepared by chemical etching in irradiated PET foil using etchant (9 M NaOH) and stopping solution (1 M NaCl $+$ 1 M HCOOH). The behavior of ionic current was recorded under stepping voltage $-$2V to $+$2V at different molar concentrations of potassium halides (KCl, KBr and KI) under symmetric bathing condition in electrochemical cell. It is found that the presence of multiple ionic species and the occurrence of counterion condensation of charge regulated polyelectrolyte play an effective role in ionic current rectification (ICR). The electrical conductance of conical nanopores may be estimated by measuring the ionic current rectification properties of track-etched nanopores. The charge transport properties vary with molar concentration and pH of electrolyte. Moreover, ICR may be used as a voltage gating phenomena with wide technological applications.

Hydrous hydrazine (N₂H${}_4\cdot {\mathrm{\text{H}}}_2$O) is considered to be one of the most promising chemicals for hydrogen storage, and the development of high-efficient and noble-metal-free catalysts is of key importance for N₂H${}_4\cdot {\mathrm{\text{H}}}_2$O decomposition to generate hydrogen. In this work, NiZnB nanoparticles (NiZnB NPs) synthesized by co-reduction method were further treated to remove the metal zinc by chemical etching with sodium hydroxide, and the resulting amorphous NiB nanocatalysts (NiB NCs) presented higher specific surface area and hydrogen selectivity than that of common NiB nanoparticles. Experimental results also indicate that heat-treatment of the NiZnB NPs can increase turnover frequency (TOF) but decrease hydrogen selectivity of the NiB NCs. NiB NCs derived from NiZnB NPs heated at 200${}^{\circ }$C show TOF and selectivity of 0.72h${}^{-1}$ and 98.1%, respectively. In addition, reusability of the resulting catalyst was also investigated.