Papers by Keyword: Nanotube

Abstract: Surface morphology and composition of anodized Ti-15Zr-4Nb-4Ta alloys with nanotube were examined by using X-ray diffractometry and analytical scanning electron microscopy. The Ti alloy consisted of α and β phases. Anodizing to form nanotube on the Ti alloy was carried out using electrolyte of 0.2 wt.% NH₄F and 2 Vol.% H₂O in ethylene glycol under different potential at from 30 to 60V. SEM observation showed that nanotubes were vertically aligned on surface of the Ti alloy. Inner diameter of these nanotubes varied from 45 to 127 nm with increasing applied potential to the specimen from 30 to 60 V. Surface of the Ti alloy with nanotube was ragged due to the difference in dissolution rate of the internal structure of α and β phases.

Abstract: Products formed in the discharge region of the DC arc between graphite electrodes in water were studied. Whereas one of them was grown on a cathode and kept whole, the other is arose by erosion of electrodes in powder form and sank or floated in the surrounding water. The structure of the products was studied by SEM and SEM EDX analysis. The whole parts grown on the cathode were made up three different components: (i) almost spherical tiny particulates; (ii) long and narrow linear parts; and (iii) macro particulates of gigantic size. We have identified the size distributions and the number densities for these component parts in the sample as well their mechanical features. The powder samples included bulk particulates of carbon sheets and linear structures, like a thread. The study shows that the long linear structures in the powder sample are formed by the scrolling of carbon layers whereas the ones deposited are formed by a growth mechanism

Abstract: Titanium dioxide nanotubes on titanium surface were prepared by electrolytic anodization in aqueous solution at constant voltages at room temperature for 2, 4 and 6 hours. Anodized titanium was heat treated in a furnace at 450 °C for 4 hours to convert amorphous structure to anatase and rutile crystalline structure. A scanning electron microscope was utilized for morphology investigation of the anodized titanium surfaces. For HF containing water media, porous surface on titanium was revealed after anodizing for 2 hours. Nanotubes (NT) were formed in this media at 4 and 6 hours anodizing time, the diameters of the tubes were approximately 70 to 100 nm. For HF/Na₂SO₄ aqueous solution, fine NTs, approximately 50 nm in diameter, were grown after 2 hours. However, the NTs obtained at anodizing time 4 and 6 hours were the same size, ranging from 100 to 120 nm. Anatase and rutile phases of TiO₂ were formed in the anodized samples after annealing at 450 °C for 4 hours. The anodized samples were tested for their abilities to degrade Rhodamine B, to demonstrate their application as a material for waste water treatment. The Rhodamine B was degraded up to 41% in annealed sample anodized by electrolyte contained HF.

Abstract: Nanotechnology as a multidisciplinary and scientific innovation plays an important role in numerous biomedical applications, such as molecular imaging, biomarkers and biosensors and also drug delivery. A wide range of studies have been conducted on using of nanoparticles for early diagnosis and targeted drug therapy of various diseases. In fact, the small size, customized surface, upgraded solubility, or multi-functionality of nanoparticles enabled them to interact with complex cellular functions in new ways which opened many doors and created new biomedical applications. These studies demonstrated that nanotechnology vehicles can formulate biological products effectively, and this nano-formulated products with a potent ability against different diseases, were represented to have better biocompatibility, bioaccessibility and efficacy, under in vitro and in vivo conditions.

Abstract: In this work, a novel and facile sequential cation-exchanging strategy was developed to synthesize phosphorus doped g-C₃N₄ nanotubes, and resulted nanotubes were composed of small nanorods with length of several hundred nanometers by oriented aggregation. As obtained products exhibit greatly enhanced photocatalytic hydrogen evolution with rate of 4.59 mmol h^-1 g^-1, which is 16 times higher than that of the bulk g-C₃N₄ under visible light irradiation. Mechanism investigation reveals that the superior photocatalytic property could be attributed to its improved visible light absorbance, well suppressed charges recombination and nanostructural construction.

Abstract: In this work, we have investigated the adsorption behavior of the CN radicals on electronic properties of BC₂N nanotube (BC₂NNT) by means of the B3LYP hybrid density functional method using 6-31G(d) basis set. The results show that CN radicals can be chemically adsorbed on the nanotube. Based on the energy analysis, the most stable position of CN radical on the nanotube is C1 site. Also, the C-side complexes are more stable than the N-side complexes. We investigated the effects of CN radicals adsorption on the electronic properties of the BC₂N nanotube. According to our calculations, band gap energy of the BC₂NNT decreases with increasing the number of CN radicals. It is predicted that the conductivity and reactivity of nanotube increase by increasing the number of CN radicals. Based on the NBO analysis, in all complexes charge transfer occurs from nanotube to CN radical. The AIM results show that, the Xtube…YCN interaction has covalent nature. Generally, The BC₂N nanotube can be used to as sensor for nanodevice applications.

Abstract: In this work, an improved technique for chirality assignment of single wall carbon nanotubes (SWCNT) is proposed which work for both isolated and bundles SWCNTs. The technique exploits the (2n+m) family pattern both in optical transitions vs diameter plot and Raman G-mode frequency vs diameter plot of SWCNTs. Using two different plots can give accurate value of the family of unknown SWCNTs that can be used to find chiral index (n, m) of unknown SWCNT unambiguously in most of the cases. Unlike existing methods, graphical comparison or pattern recognition with an existing Kataura plot is not required here. Chirality of 13 SWCNTs are assigned here using this technique. Validity of assigned chirality is cross checked from previous experimental reports. The technique is especially useful for determining chirality of isolated SWCNT.

Abstract: In this work, effect of chirality on gas adsorption property of semiconducting single-wall carbon nanotubes (SWCNTs) is reported for the first time. First principles simulation of the interaction of three different chirality SWCNTs with different gas molecules is performed maintaining equilibrium tube–molecule distance. Results are obtained employing density functional theory, using the Atomistic toolkit simulation package (ATK-DFT). Nanotube density of states is observed to vary significantly due to interaction with different types of gases as well as for same gas if chirality of SWCNTs varies. The most significant finding is, the change in DOS near Fermi level is highest in mod 2 type semiconducting SWCNT for different gas molecules irrespective of donor or acceptor. Thus, proper selection of chirality of SWCNT is important to make nanotube based gas sensor and mod 2 types semiconducting SWCNTs should get preference over mod 1 type as a sensing element so as to get better sensitivity.

Abstract: Pure and F doped TiO₂ nanotubes was synthesized using simple hydrothermal method. The hydrothermal was conducted using teflon-liner autoclave and maintained at 150oC for 24 hours. The characterization of synthesised product was carried out using x-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive of x-ray spectroscopy (EDX) and ultra violet – visible light diffuse reflectance spectroscopy (UV-Vis DRS) for band gap measurements. XRD patterns indicated that anatase TiO₂ phase was remained after F doping suggested that fluorine was highly dispersed into TiO₂ by substituted with O in the TiO₂ lattice to formed TiO_2-xF_x solid solution. Morphology investigation using TEM found out small diameter of nanotubes structure within 8 – 10 nm of pure and F doped TiO₂ nanotubes. The band gap energy (E_g) of both nanotubes samples were almost similar proposing that F doping does not modify the band gap energy.

Abstract: We carried out the atomistic structural instability (ASI) analysis with an empirical interatomic potential for carbon nanotubes (CNTs) under axial compression with the aim to reveal the mechanism of buckling. We investigated how ‘latent’ instability modes develop until one of them is activated at the structural instability. For pristine single-walled carbon nanotubes (SWCNTs), Euler-type buckling was found in relatively thin nanotubes, while buckling modes corresponding to change in the cross-sectional shape (radial buckling) were found in thick nanotubes. The crossover between the Euler-type buckling and radial buckling modes was clearly seen in the ASI analysis. While the reduction of Hessian eigenvalues in the pristine nanotubes and nanotubes with a vacancy is nearly linear until instability, rapid decrease of eigenvalues just before instability was found in models with Stone-Wales defects. This is due to localization of instability mode vectors around the defects that tends to arise before structural instability.