Papers by Keyword: Nanotube

Abstract: One-dimensional Fe, Co, Ni nanotube arrays ware fabricated successfully by the electrochemical deposit in porous anodic alumina oxide (AAO) templates. The microstructure of nanotubes were observed by scanning (SEM) and transmission electron microscopes (TEM) respectively. The obtained Fe, Co, Ni nanotubes are arranged orderly. The magnetic property of nanotubes was measured and analyzed. The results show that the residual magnetization of Ni nanotubes is the biggest, and that of Fe nanotubes is the smallest. It is easy to be magnetized along the axial direction.

Abstract: Through-hole TiO2 nanotube arrays were successfully prepared by using mechanical coupling Ti/Ti foils as anode. By continuously anodization, one Ti foil was thoroughly fabricated into TiO2 nanotube arrays, and the bottom barrier of TiO2 nanotube arrays was extended to the other Ti foil layer. The physical gap between two Ti foils allowed the TiO2 nanotube arrays to be easily separated from the barrier layer. Thus the through-hole TiO2 nanotube arrays were obtained. The method is simple but effective to thoroughly remove the bottom barrier layer and obtain through-hole TiO2 nanotube arrays without any complicated processes.

Abstract: The calculation of generalized stacking fault energy for covalent materials exists several relaxation methods. And the modification factor of the restoring force should be different for different relaxation. In order to study the impact of generalized stacking fault energy on the mechanical properties of dislocations, the dislocation energy, Peierls barrier and Peierls stress of shuffle dislocation in zigzag single-walled carbon nanotube (SWCNT) under different modification factors are studied by the improved Peierls-Nabarro (P-N) theory. It is found that the misfit energies decreased, and the strain and total energies increased with increasing of the modification factor Δ. With the modification factor Δ of the restoring force changes from -0.2 to 0.5, the dislocation energy changes from 17.4eV to 19.3eV. The Peierls barriers E_p and σ_p Peierls stresses increased first and then decreased and the results are not as same as we thought. The impact of generalized stacking fault energy on mechanical properties of dislocations is not so simple as we thought and need to be further studied.

Abstract: This study used porous alumina membranes with nanopores as nanopore channels and successfully constructed a single-stage/multistage nanotube electroosmotic micropump. The characteristics of electroosmotic nanotubes pump constructed using porous alumina membranes with varying pore sizes and at different stages were also analyzed. During the experiments, applying a multistage nanotube electroosmotic micropump with the same pore size at the two stages yielded a superior performance curve compared to that of the single-stage nanotube electroosmotic micropump. The flow volume and pressure difference of the pump increased rapidly with the input voltage. Thus, the flow volume of multistage nanotube electroosmotic micropump with the same pore size can be increased more than twice that of single-stage pumps. With a high input voltage, the multistage micropump showed a significant, approximately 4-fold increase.

Abstract: This paper gives an overall review of TiO₂ nanotube arrays synthesized on titanium and its alloys substrates by anodization. The highly ordered nanotubes are fabricated by electrochemical anodization in electrolyte containing fluoride ion. During the anodization process, the electrochemical conditions such as the electrolyte, applied voltage, anodization time, temperature and alloy substrates are analyzed in detail. Anodization of titanium alloy is a simple and effect method to dope element into TiO₂ nanotube which shows much higher improvement in photocatalytic and solar energy conversion than pure TiO2 nanotube arrays. In addition, we review the forming mechanism and modification. Furthermore, TiO₂ nanotube arrays have great application for dye-sensitized solar cells, water splitting and biomedical and other aspects.

Abstract: A vertically aligned bioactivity titania nanotube arrays was fabricated on the surface of titanium substrate by anodization. The nanotubes were then treated with optical deposition of silver to make them antibacterial, and to inhibition growth of bacterial in the antibacterial test in vitro. It is shown that the present of silver particle inhibition the growth staphylococcus aureus. Such bioactivity titania nanotube arrays and associated hollow tube structure can be useful as a well-adhered antibacterial bioactive surface layer on titanium implant metals for orthopaedic and dental implants.

Abstract: Among nonomaterial with different geometric shapes, nanotubes and nanowires received special attentions with increasing applications in electronic industry and nanorobotic due to their unique properties. Therefore, in order to study the fundamental properties of nanotubes/wires, in this paper we will focus on modeling the melting of different crystal surface of metallic materials. Although there are different models in literature based on change of cohesion energy or coordination number at nanoscale, here we present a generalized thermodynamics model which considers layer by layer melting of nanotubes/wires. This model considered the surface energy of solid-gas, liquid-gas and solid-liquid along with the effect of fcc, bcc and hcp crystallography of different metals and their different surface crystal plane orientations. During the analytical simulation of surface melting, different run have been performed for variable size of tubes/wires in order to involve the size effect at nanoscale. Calculation results of model will be presented for some metallic systems such as: Ni, Pb, Fe and Zn. Results of our calculations show good agreement with experimental results and other theoretical predictions in literatures. Our model provides a powerful tool to analysis melting phenomena of metallic nanotubes/wires at different crystal structures and surface plane orientations for various sizes at nanoscale.

Abstract: TiO₂ nanotube arrays were fabricated through anodization in the glycol electrolyte system. The new composite structures of the bottom nanotube and the upper nanowire with a length of 15 um to 20 um were prepared. The influence of the water contents in the electrolyte with respect to the composite structure was studied through two-step anodization. The results show that the composite structure can be obtained based on the moderate etching rate of the electrolyte and the selective etching of the nanotube when the glycol system electrolyte contains 0.4wt% NH₄F and 2 vol% H₂O.

Abstract: The α-Fe₂O₃ nanotubes were prepared by the eletrospinning and calcination process. The as-prepared α-Fe₂O₃ nanotubes were characterized by XRD, SEM and BET. The XRD patterns show that the nanotubes with a pure hematite phase (α-Fe₂O₃) are obtained after calcination at 550 oC. The SEM morphologies and BET measurement demonstrate the nanotubes have an average diameter of 200-300 nm and a specific surface area of 15.1 m2/g. Their adsorption of methyl blue was studied with ultraviolet spectrophotometer (UV) to measure the concentration of methyl blue in aqueous solution, and the adsorption kinetics is basically in agreement with the pseudo-second-order kinetic model in the methyl blue concentration range of 100-300 mg/L.

Abstract: The palladium nanotube was synthesized by template wetting and annealing process. And the activation energy for formation of the palladium metal from palladium acetate was evaluated. The activation energy was evaluated by Friedman method and the values were in the ranges between 65 and 98 kJ/mol. The diameters and lengths of synthesized palladium nanotubes ranged from 130 to 190 nm and from 2 to 3 μm, respectively. The palladium nanotubes can be successfully fabricated by the template wetting process, and the crystalline structure is confirmed by XRD. From DSC results the thermal decomposition of precursor containing palladium acetate/PLLA occurred at 248°C, which corresponds to the precipitation of palladium metal.