Synthesis and characterization of Nb2O5@C core-shell nanorods and Nb2O5nanorods by reacting Nb(OEt)5via RAPET (reaction under autogenic pressure at elevated temperatures) technique

The reaction of pentaethoxy niobate, Nb(OEt)5, at elevated temperature (800 °C) under autogenic pressure provides a chemical route to niobium oxide nanorods coated with amorphous carbon. This synthetic approach yielded nanocrystalline particles of Nb2O5@C. As prepared Nb2O5@C core-shell nanorods is annealed under air at 500 °C for 3 h (removing the carbon coating) results in neat Nb2O5nanorods. According to the TEM measurements, the Nb2O5crystals exhibit particle sizes between 25 nm and 100 nm, and the Nb2O5crystals display rod-like shapes without any indication of an amorphous character. The optical band gap of the Nb2O5nanorods was determined by diffuse reflectance spectroscopy (DRS) and was found to be 3.8 eV

Limits on the production of scalar leptoquarks from Z (0) decays at LEP

A search has been made for pairs and for single production of scalar leptoquarks of the first and second generations using a data sample of 392000 Z0 decays from the DELPHI detector at LEP 1. No signal was found and limits on the leptoquark mass, production cross section and branching ratio were set. A mass limit at 95% confidence level of 45.5 GeV/c2 was obtained for leptoquark pair production. The search for the production of a single leptoquark probed the mass region above this limit and its results exclude first and second generation leptoquarks D0 with masses below 65 GeV/c2 and 73 GeV/c2 respectively, at 95% confidence level, assuming that the D0lq Yukawa coupling alpha(lambda) is equal to the electromagnetic one. An upper limit is also given on the coupling alpha(lambda) as a function of the leptoquark mass m(D0)

Search for jet extinction in the inclusive jet-pT spectrum from proton-proton collisions at s=8 TeV

Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published articles title, journal citation, and DOI.The first search at the LHC for the extinction of QCD jet production is presented, using data collected with the CMS detector corresponding to an integrated luminosity of 10.7  fb−1 of proton-proton collisions at a center-of-mass energy of 8 TeV. The extinction model studied in this analysis is motivated by the search for signatures of strong gravity at the TeV scale (terascale gravity) and assumes the existence of string couplings in the strong-coupling limit. In this limit, the string model predicts the suppression of all high-transverse-momentum standard model processes, including jet production, beyond a certain energy scale. To test this prediction, the measured transverse-momentum spectrum is compared to the theoretical prediction of the standard model. No significant deficit of events is found at high transverse momentum. A 95% confidence level lower limit of 3.3 TeV is set on the extinction mass scale

Searches for electroweak neutralino and chargino production in channels with Higgs, Z, and W bosons in pp collisions at 8 TeV

Searches for supersymmetry (SUSY) are presented based on the electroweak pair production of neutralinos and charginos, leading to decay channels with Higgs, Z, and W bosons and undetected lightest SUSY particles (LSPs). The data sample corresponds to an integrated luminosity of about 19.5 fb(-1) of proton-proton collisions at a center-of-mass energy of 8 TeV collected in 2012 with the CMS detector at the LHC. The main emphasis is neutralino pair production in which each neutralino decays either to a Higgs boson (h) and an LSP or to a Z boson and an LSP, leading to hh, hZ, and ZZ states with missing transverse energy (E-T(miss)). A second aspect is chargino-neutralino pair production, leading to hW states with E-T(miss). The decays of a Higgs boson to a bottom-quark pair, to a photon pair, and to final states with leptons are considered in conjunction with hadronic and leptonic decay modes of the Z and W bosons. No evidence is found for supersymmetric particles, and 95% confidence level upper limits are evaluated for the respective pair production cross sections and for neutralino and chargino mass values

Optimization of sintering on the structural, electrical and dielectric properties of SnO2 coated CuFe2O4 nanoparticles

An ever first attempt to synthesize nanocomposites of SnO2 coated CuFe2O4 has been made using urea–nitrate combustion method. Effect of various concentrations of SnO2 (1, 5, 10 and 20 wt.%) at three different sintering temperatures viz., 800, 1000 and 1100 ◦C for optimizing the compound formation has been studied individually. The synthesized materials were characterized by XRD, TEM, HRTEM, SAED, SEM, FT-IR, UV–vis, electrical conductivity and impedance spectra measurements. The XRD spectra reveal that 1100 ◦C-sintered sample is of ultra pure and well-defined crystalline nature irrespective of the concentration of SnO2. The grain size of the materials has been found to get increased as a function of sintering temperature and the extent of SnO2 substitution. The TEM and HRTEM figures evidence the nanocrystalline nature of the product. SAED pattern confirms the presence of single phase and polycrystalline of the final product. The band gap values were calculated from UV–vis spectra, which confirm the lowest band gap value for the 5 wt.% SnO2 added sample. The solid-state impedance and the electrical properties of the materials are in favour of the grain and grain boundary effect and the normal behavior of spinel compounds, respectively

Synthesis of Nanocrystalline Zirconium Titanate and its Dielectric Properties

The thermal decomposition of a ZrTi2[(OC2H4)2NH]3(OC3H7)6 precursor by the RAPET (reaction under autogenic pressure at elevated temperature) method provided the formation of crystalline zirconium titanate nanoparticles. These as-prepared nanoparticles are embedded in a carbon shell, which can be removed completely by calcination at 500 °C under air for 3 h, resulting in pure white crystalline nanoparticles. At a reaction temperature of 700 °C, the nanoparticles are mainly ZrTi2O6 (srilankite), whereas at 800 °C, the product is predominately Zr5Ti7O24. The structural, morphological, compositional, magnetic, and AC electrical properties are measured for the as-prepared ZrTi2O6 embedded in carbon (ZTEC), as well as the crystalline ZrTi2O6 nanoparticles (ZTN) obtained after sintering. The reaction mechanism is based on the decomposition products containing pyrrol and pyrazine. The presence of these compounds provides an understanding of the decomposition of the diethanolamine ligands and the formation of the nanoparticles in general

Mesoporous anataseTiO2 Nanorods as thermally robust anode materials for Li-Ion batteries: detailed insight into the formation mechanism.

International audienceUniformly mesoporous and thermally robust anatase nanorods were produced with quantitative yield by a simple and efficient one-step approach. The mechanism of this process was revealed by insertion of Eu3+ cations from the reaction medium as luminescent probes. The obtained structure displays an unusually high porosity, an active surface area of about 300 m2g−1 and a specific capacity of 167 mA h g−1 at a C/3 rate, making it attractive as an anode electrode for Li-ion batteries. An additional attractive feature is its remarkable thermal stability; heating to 400 °C results in a decrease in the active surface area to a still relatively high value of 110 m2 g−1 with conservation of open mesoporosity. Thermal treatment at 800 °C or higher, however, causes transformation into a non-porous rutile monolith, as commonly observed with nanoscale titania