Journal of Nano Research Vol. 3

Abstract: The identification of features in the Local Density of States (LDOS) of carbon nanotubes (CNTs) obtained by Scanning Tunneling Spectroscopy (STS) is of great importance in order to understand their properties. In this work, Single- and Multi-Wall Carbon Nanotubes are compared with Multi-Wall CNTs filled with tin nanowires (Sn@CNTs) in order to investigate the effect on morphological and electronic properties of the CNTs metallic filling. The LDOS of CNTs, together with topology changes, is investigated by using spatially resolved STM/STS at room temperature and in air and compared to the LDOS of highly oriented pyrolitic graphite (HOPG). The LDOS of CNTs is dominated from different electronic states filling the C 2pσ-2pσ* band gap. The appearance of those states is linked to the diameter and the defects of the CNTs. In fact, Snnanowires encapsulation induces changes in the structure of the CNTs and the appearance of electronic states in the LDOS inside the band gap. A more extensive description of the samples is obtained depicting the morphological features and the vibrational structure on wider areas using Scanning Electron Microscopy (SEM) and Raman spectroscopy, respectively.

Abstract: Titanium Aluminide-based composites with Al2O3 reinforcement can be produced via reaction of Al with TiO2. These composites are considered as low-cost materials for high temperature applications. Addition of KClO4 to the TiO2/Al system was investigated in this research. On the basis of the results obtained, addition of KClO4 to the mixture of TiO2/Al and subsequent heating, results in titanium aluminide/alumina nanometric particle formation with dimensions of about 30 nm. Densification of this composite powder leads to production of a titanium aluminide-alumina nanocomposite body. Dimensions of the alumina phase are in the range of 100-150nm.

Abstract: The two dimensional nanoplates of WSe2 and MoSe2 are the result of solid-state thermal (750oC) reaction between micrometer-sized W or Mo with micro-size Se powder under inert atmosphere via carving phenomena in a closed reactor. This is a distinct top-down approach presented for the fabrication of inorganic nanoplates, where micron-sized metal particles having very high melting and boiling points are converted into a Se–M–Se sandwich structure employing a single-step, scalable, and environmentally- friendly chemical reaction under autogenic pressure at elevated temperature (RAPET). The mechanistic elucidation of the creation of WSe2/MoSe2 nanoplates is suggested on the basis of the crystal structure with the support of data obtained from compositional, structural, and morphological characterizations.

Abstract: A method of ac dielectrophoresis was applied to align and deposit metallic multi-wall carbon nanotubes between pre-fabricated metal (Au, Pd) electrodes with a micron scale separation. For improvement of nanotube contacts with electrodes, Ni and Pd electroless processes were developed, and significant reduction of 2 terminals resistances was demonstrated. Further, using electron and ion beam deposited Pt contacts in two different configurations (“Pt-on-CNT” and “CNT-on-Pt”), 4 terminals measurements have been performed to evaluate intrinsic nanotube resistances. The values between 90 and 130 kΩ/μm were obtained, while systematically lower values (30-70 kΩ/μm) were estimated using 2 terminals method. The 4 terminals method was applied to study the effect of ion irradiation on the electrical parameters of supported nanotubes.

Abstract: The instrumented indentation technique is being widely used for the determination of elasto-plastic properties of metallic materials by analyzing located atomic force microscopy (AFM) image area and loading-displacement data of indentation imprints after testing. This data analysis is highly dependent on the method followed for interpretation the loading and unloading curves. We have detailed the two common methods, the Oliver&Pharr method based on a power law and the energetic approach method based on finite elements, in order of understanding the nano-indentation unloading behavior to determine the closer hardness and Young’s modulus of metallic materials..

Abstract: X-ray tools are being powerful methods for qualitative and quantitative analyses of nanocrystalline materials This work is an overview of detailed X-ray investigations relative to microstructural studies applied for a refined binary Al-based alloys thin films system as samples deposited on glass substrates. Energy dispersive analysis of X-ray (EDAX), X-ray diffraction (XRD) and transmission electron microscopy (TEM) methods were used to determine the chemical composition, the microstructure parameters and the solubility of copper in aluminum.

Abstract: Two-dimensional in-plane interface structures of highly epitaxial perovskite (La,Ca)MnO3 (LCMO) and (Pb,Sr)TiO3 (PSTO) thin films on salt-rock type MgO substrate were studied using Transmission Electron Microscopy (TEM). Cross-section TEM studies revealed that both LCMO and PSTO films are good single crystal quality and have atomic sharp interface with respect to the MgO substrate with -6.4% and -6.2% lattice mismatch, respectively. Electron Diffraction Patterns (EDPs) of plan-view LCMO/MgO and PSTO/MgO interfaces exhibit double diffraction spots. An analytical approach was employed using double diffraction to study the two-dimensional in-plane interfaces of perovskite structure films on the salt-rock type substrate. The lattice mismatch near the interface regions was determined using EDPs of the plan-view interfaces and found to be -8.0% for LCMO/MgO and -7.14% for PSTO. Both latter values are larger than those obtained using cross-section TEM. Studies of the sharpness of double diffraction spots and plan-view high resolution (HR) TEM brought a conclusion that the PSTO film is well commensurate with the MgO substrate over large areas, whereas LCMO film is only locally commensurate with the substrate. These studies provide additional evidence to our previous observations that plan-view TEM of the interface is able to provide critical and valuable information that is lacking from the cross-section TEM analysis.

Abstract: Two biphasic BCP ceramic samples were synthesized by chemical precipitation and microwave curing of calcium deficient hydroxyapatite CDHA under the same pH value and temperature but varied in their initial Ca/P molar ratio. Precipitates were characterization after thermogravimetric analysis, fourier transform infrared spectroscopy, X-ray diffraction, atomic absorption spectroscopy and TEM. Hydroxyapatite (HA) contents were measured for the two biphasic calcium phosphate (BCP) ceramics by sintering the calcium-deficient apatites (CDHA). The results reveal two condensation mechanisms of HPO42- affecting the Ca/P molar ratio after calcination. The X-ray diffraction patterns of BCP powders show the in situ formation of -TCP in the BCP powder. The amount of -TCP phase increases as the initial Ca/P molar ratio decreases due to more calcium deficiency in CDHA structure. The influence of HPO42- incorporation on increasing -TCP phase content after calcination is evaluated. TEM micrographs proved the effect of microwave curing during the preparation process on reducing of particle size to nanoscale range and the destruction of CDHA to finer HA and -TCP particles upon calcination.

Abstract: In the past decades, porous materials have attracted great scientific and industrial interest due to their appealing structures and potential applications in separation, purification, catalysis, devices, and so forth. The developing community of ordered mesoporous materials has carried on this exploration of the mesoscopical territory, which promises their unique capacities related to large molecules and their transportation in confined space. Thus rational control and adjustment of pores have been continually focused during the synthesis of ordered mesoporous materials with diverse intrinsic properties. In this work, vitamin C encapsulated mesoporous silica was successfully synthesized with tetraethylorthosilicate (TEOS). TEOS was subjected to sol-gel process in the presence of cetyltrimethylammonium bromide (CTAB). The composition and size of mesoporous silica was controlled by fitting the molar ratio of starting materials. The mesoporous silica can be applied to the field of the cosmetics and bio-medicine as drug delivery.

Abstract: The CdS nanoparticles of different sizes are synthesized by a simple chemical method. Here, CdS nanoparticles are grown through the reaction of solution of different concentration of CdCl2 with H2S. X-ray diffraction pattern confirms nano nature of CdS and has been used to determine the size of particle. Optical absorption spectroscopy is used to measure the energy band gap of these nanomaterials by using Tauc relation. Energy band gap ranging between 3.12 eV to 2.47 eV have been obtained for the samples containing the nanoparticles in the range of 2.3 to 6.0 nm size. A correlation between the band gap and size of the nanoparticles is also established.