This paper reports the synthesis and characterization of the ZrO2:Co nanosystem, by incorporation of Co nanoparticles (CoNP) into tetragonal and monoclinic zirconia. ZrO2 was synthesized by a sol-gel process, while cobalt nanoparticles were obtained through a colloidal method by chemical reduction of a metal precursor. CoNP were incorporated by two different approaches: during the synthesis of the ZrO2 and by classical impregnation of CoNP on zirconium oxide. The size of Cobalt nanoparticles was controlled through the concentration of reducing agent (NaBH4) and passivanting agent (1-dodecanethiol). According to SEM and TEM analysis, the diameter of the zirconium oxide particles depends on the CoNP concentration added; the particle size for pure zirconia treated at 500°C is 200 nm and 180 nm for ZrO2:Co. X-Ray diffraction showed presence of the tetragonal and monoclinic zirconia, but the abundance of each one depends on the Co nanoparticles and thermally treatment.

Grain boundaries are the dominating type of defect in nanocrystalline materials. Understanding their properties is crucial to the comprehension of nanocrystalline materials behavior. A facile thermodynamic model for alloy grain boundaries is developed. The macroscopic analysis is based on established descriptions of metallic solutions and the universal equation of state at negative pressure, using mainly parameters obtainable from measurements on macroscopic samples. The free energy of atoms in grain boundaries is derived as a function of excess volume, composition, and temperature. Interfacial enrichment is computed using equilibrium conditions between bulk phase and grain boundaries. The excess volume of symmetric ‘100’ tilt grain boundaries in Cu as a common system is obtained by atomistic computer simulation. In a general case the predictions of the proposed model are compared to experimental grain boundary segregation data, yielding a good match. The near-equilibrium solubility of Ag in nanocrystalline Cu and of Cu in nanocrystalline Fe is calculated.

By using the citrate reduction procedure we have synthesized Ag nanoparticles, applying several conditions of preparation, being after characterized by UV-visible spectrophotometry. Following a logical sequence, the starting experiment was realized varying the reaction time, after that it was varied the concentration of the reductor agent, and finally it was varied the volume of the reductor agent. According to this methodology, TEM measurements show that firstly we have nanostructures with different shape and size, whereas in the last part of the experiment we have Ag nanoparticles with homogeneous shape and size.

An efficient synthetic route for the synthesis of carcerands derived from tetramethylchlorocavitands and its tetraesters derivative were synthesized. A large-scale preparation was achieved in good yield. These carcerands are in bridging unit between oxygen atoms, i.e. contains a 3,5 dihydroxybencyl alcohol units. 1H, and 13C NMR in solution, FTIR, UV-vis spectroscopy, MS-FAB+ spectrometry and elemental analysis confirmed the structure of this carcerands.

A reactive molecular dynamics simulation study on the structure, energetics, and chemistry of alkanethiolated gold cluster is presented. Through very recent reactive molecular dynamics force-fields developed by Järvi et al. [1], chemical reactions of alkanedithiolates and star-like shape gold nanoparticles are studied throughout octanedithiolates and stellated cuboctahedral gold clusters models [2] at room temperature. Structure, energetics, reactants, and some products of the reactions are preliminarily analyzed up to 25 ps. In general, preliminary results of this work are in agreement with those reported in the review by Love et al. [3].

In the present work, a comparison study of the NiMo hydrodesulfurization (HDS) catalysts supported on different nanostructured supports of MCM-41 and SBA-15-types and the same ones modified by TiO2 grafting was undertaken. The aim of this study was to inquire on the effect of the characteristics of the primary silica supports on the activity and selectivity of the NiMo catalysts modified with titania in deep HDS. Supports and catalysts were characterized by nitrogen physisorption, small-angle and powder XRD, TPR, UV-vis DRS, and HRTEM, and tested in the simultaneous HDS of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). It was found that titania grafting on all silica supports resulted in a slight decrease of BET surface area and total pore volume. However, the characteristic p6mm hexagonal pore arrangement of the used nanostructured silica materials was not affected. Powder X-ray diffraction pointed out a good dispersion of Mo and Ni oxide species in all prepared catalysts. TPR characterization of the NiMo catalysts revealed some increase in the metal-support interaction after titania grafting on the silica surface. Further DRS characterization indicated that the best dispersion of Mo oxide species was obtained on the TiSBA-15 support. Titania addition to the silica supports also produced an increase in the dispersion of the sulfided NiMo phase, which was more marked for SBA-15 support than for the MCM-41 (HRTEM). The most active NiMo/Ti-SBA-15 catalyst resulted to be significantly more active (∼40 %) than the conventional NiMo/γ-Al2O3 catalyst in HDS of 4,6-DMDBT.

Multiwalled carbon nanotube (MWCNT)/Nylon-6 nanohybrids were prepared by in situ polymerization under microwave irradiation. The effect of time and power of irradiation on the surface conductivity of the nanohybrid was studied. It was observed that the resistivity increases with irradiation time at low microwave power (200W). On the other hand, at high power (600W) an opposite behavior was observed. And at intermediate power (400W) the resistivity was independent of the irradiation time. Resistivity values range from 102 to 101 Ω/sq. This behavior was associated with the polymer nanocoating covering the surface of the carbon nanotubes.

In this work we present the bases to perform investigation on the effects on the morphology and size of nanostructures of silver, owed to the modification of synthesis factors in a polyol process such as temperature, concentration, time of reaction, injection speed and time of injection. It is claimed that control over Ag nanostructures shape could be improved and significant information about the synthesis process can be obtained. The design of experiments was done aimed to obtain useful information about how to yield as much as possible specific structures of interest.

Silver triangular nanoprisms (TNP’s) were transformed into silver nanodisks (NDK’s) by addition of halide ion solution (chloride, bromide and iodide). The shape transformation of the TNP’s is due to the selective etching effect of halide ions at their vertices. TNP’s were synthesized via a photoinduced growth process, and then different concentrations of potassium halide solutions were added into the TNP’s colloids under vigorous stirring. Images of the obtained nanoparticles were recorded by scanning electron microscopy (SEM). The shifts of the in-plane dipole plasmon resonance band allow us to identify the differences among the three halides. These differences might be due to the distinct sizes of halides, and the solubility product constant values of each silver halide. We found that the etching ability of the halides, at a concentration of 1.0 mM, to truncate the vertices of TNP’s is in the order of Br- > Cl- > I-. In contrast, at a concentration of 0.01 mM, the order of the etching ability is Br- > I- > Cl-.

In this work, the effect of structural characteristics of organomodified clays on the dispersion degree, mechanical and rheological properties of the nanocomposites PP-EP/EVA/nanoclay has been studied. The studied effects were: degree of chemical modification of the clay, length of substitute groups on the surfactant, and the steric effect caused by surfactant structure. The characterization techniques used were Wide Angle X-ray Diffraction (WAXD), Scanning Transmission Electron Microscopy (STEM), Dynamic Mechanical Analysis (DMA), Tensile Test and Capillary Rheometry. Cloisite 6A, 15A and 20A were used to evaluate the first effect. Better intercalation-exfoliation and mechanical properties were obtained when the clay with lower content of surfactant was used (C20A), these results were attributed to a higher saturation of the system. In order to study the second effect, Cloisite 20A and Cloisite 25A were employed. It was found that the bigger initial intergallery space between these nanoclay’s caused by the longer chains in Cloisite 20A, allows the formation of a structure with better intercalated-exfoliated structure. This was confirmed with the observed increase in mechanical properties. Finally, the third effect was studied with Cloisite 10A and 15A. It was clearly seen that only with Cloisite 15A was possible to obtain an intercalated-exfoliated structure. This was attributed to a major steric effect when using C10A than with 15A.

In this work, we use the T-matrix method to study the tunneling of Dirac electrons through graphene multilayers. A graphene sheet is deposited on top of slabs of SiO2-SiC substrates, of which we applied a Gaussian distribution in the size width of the SiC substrate. We calculate the transmittance as a function of energy for different incident angles and different number of layers of the Gaussian distribution. We obtain different stop-band regions. These regions are wider when the width of the barrier is increased. Furthermore, it is possible to tune the width and the position of stop-band with the angle of incidence, the σ value of the Gaussian distribution, and the difference between the maximum-minimum sizes of the barrier.

A top-down approach using classical thermodynamics is presented in this paper to deduce size and shape dependencies of different material properties. Particular attention is focused on the thermal expansion coefficient. The theory developed here can also be used to deduce information on surface energies.

The fracture behavior of polypropylene (PP) and its composites was studied as a function of concentration of multiwall carbon nanotubes (MWCNT) and modified montmorillonite (m-MMT). SAXS and WAXS (Small/Wide Angle X-ray Scattering) techniques were used to monitor the morphological changes (i.e. nanocomposite structure and crystalline morphology) caused by various nanoparticle concentrations and polymer uniaxial stretching deformation. The effect of nanoparticle nature was also investigated. The mechanical analysis shows a great effect of nanoclay concentration on the PP deformation, while uniaxial stretching of the PP/MWCNT nanocomposites was less affected by carbon nanotubes concentration. The SAXS and WAXS analysis of stretched samples indicated that the pure polypropylene and nanocomposites with low nanoparticles concentrations (1 wt/wt%) developed a fracture governed by shear yielding mechanism, while PP nanocomposites with higher concentrations of carbon nanotubes and nanoclay showed a crazing and microcraking fracture mechanism. On the other hand, different chemical nature of MWCNT and m-MMT did not affect the fracture mechanism of polypropylene at low nanoparticles concentrations.

We have synthesized core-shell 1D nanostructures by the Vapor-Liquid-Solid (VLS) mechanism. Gold (Au) was used as a catalyst and tin oxide (SnO) powder as a precursor; the growth temperature was of 600 °C. These structures were characterized by XRD, SEM, TEM, EDS, and PL. The nanowires have an average diameter of 20 nm and their lengths are of tens of micrometers; the core is tin dioxide (SnO2) with the tetragonal rutile structure and it has an average diameter of 12 nm; the shell is amorphous Sn of 8 nm average thickness. Photoluminescence measurements show a broad band in the 400-800 nm range. On the same growth process, SnO2 nanoparticles and a mixture of SnO2 rods and wires were also obtained, at 400 °C and 800 °C, respectively.

Iron oxide (Fe2O3, 20-40 nm), aluminum oxide (Al2O3, 50 nm) and silicon oxide (SiO2, 20-60 nm) nanoparticles were mixed in different concentrations (1 to 5 wt %) in a magnesium oxide matrix to develop new refractory matrixes as candidates in the lining of secondary ladle metallurgy. To avoid agglomeration of nanoparticles in the magnesium oxide (MgO) matrix, it was carried out a dispersion method of nanoparticles with different dispersants. After that, the powder mixture was sintered at a temperature of 1300 and 1500 °C for 4 hours. The refractory samples obtained were studied using X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-ray spectrometer (SEM-with EDX) and also measured their density and porosity. The results showed that the samples sintered at 1500 °C with 5 wt % of Fe2O3 reached the highest density and presented the MgFe2O4 spinel-type phase. With the addition of Al2O3-nanoparticles in the MgO matrix, there were the formation of MgAl2O4 spinel phase and in the case of SiO2-nanoparticles addition it was observed the formation of Mg2SiO4 forsterite phase. It is well known that with the increase in spinel phase in the matrix, there is a significant help to retain quantities of ions of iron and nickel due to the dissolution of the slag into the refractory material extending their lining life.

Zirconia nanopowders doped with different concentrations of Eu were prepared by the solgel method followed by a thermal treatment at 500°C. Morphological and crystallographic characteristics were studied by scanning electron microscopy, X-Ray diffraction and UV spectroscopoy. Results showed a modification of the size of nanopowder particles when the concentration of Eu is increased from 0.0 to 4.0 wt%. Also, at lower concentration of Eu the tetragonal ZrO2 is the most abundant phase while high concentrations of Eu lead to the formation of the monoclinic phase. The UV spectroscopy of ZrO2 samples shows two main absorption peaks at 228 and 214 nm. The novel characteristics of the ZrO2 nanopowders doped with Eu allow us to propose them for use as solar UV radiation detectors.

In the present work an alternative nanoparticle synthesis technique was developed, where the nanoparticles nucleate and grow inside the pores of the nanostructured porous silicon (NPS). Employing green method for the nanoparticle synthesis, yeast extract is used as a reducing agent. The porous layers were prepared by electrochemical etching of Boron-doped (100) Si substrate (0.01-0.02Ohm·cm). The NPS support was immersed into the reactive colloid for different times, then withdrawn, cleaned and dried. SEM and XRD measurements were carried out to characterize the NPS substrate and the immobilized catalyst nanoparticles. EDX mapping shows a homogeneous deposition of nanoparticles on the porous support. The average particle size, calculated from XRD diffractograms (using the Scherrer`s formula), was found between 6 to 10 nm. This method provides a good incorporation and distribution of nanoparticles, also an alternative environment-friendly technique to develop catalytic devices fabricated on silicon substrate with an additional advantage of being integrated with the silicon based microelectronic circuits.

We present the propagation properties of Dirac-electrons in multilayered Period-Doubling (MPDGS) and Silver-Mean (MSMGS) graphene structures. The multilayered graphene structures are built arranging breaking and non-breaking symmetry substrates such as SiC and SiO2 following a given quasirregular substitution rule locating on them a graphene sheet. We have implemented the Transfer Matrix technique to calculate the transmittance of these multilayered graphene structures. This technique allows us to analyze readily the main differences of the transmission properties between MPDGS and MSMGS.

We present a new type of device to separate biochemical compounds wherein carbon nanotubes (CNTs) are integrated as chromatographic stationary phase. The CNTs were directly grown on the bottom of microfluidic channels on Si/SiO2 substrate by chemical vapor deposition (CVD). Acetylene was used as carbon source and Ni was employed as catalyst. For electrokinetic separations, higher electrical field strength is usually required; therefore, the CNTs were constructed in pillar-array-form by patterning Ni catalyst layer. Electrical field strength of 2.0 kV/cm has been realized, which is more than one order of magnitude higher than the one reported so far. The microfluidic chips integrated with CNTs were successfully used to separate a compound containing two Coumarin dyes, 240 mM C460 and 270 mM C480.