Search results for " NANO"

Effect of thermal annealing on the luminescence of defective ZnO nanoparticles synthesized by pulsed laser ablation in water

2016

This work concerns ZnO nanoparticles (NPs), with sizes of tens of nm, produced by ablation with a pulsed Nd:YAG laser of a Zn plate in H2O. TEM images evidence the formation of nanoparticles with sizes of tens of nm. Moreover, HRTEM images and Raman spectra show that the distance between the crystalline planes and the vibrational modes are consistent with ZnO nanocrystal in wurtzite structure. Their optical properties are characterized by two emission bands both excited above the energy gap (3.4 eV): the first at 3.3 eV is associated with excitons recombination, the second at 2.2 eV is proposed to originate from a singly ionized oxygen vacancy. The green emission is independent of water pH,…

Laser fluence, repetition rate and pulse duration effects on paint ablation

2006

Abstract The efficiency (mm3/(J pulse)) of laser ablation of paint was investigated with nanosecond pulsed Nd:YAG lasers (λ = 532 nm) as a function of the following laser beam parameters: pulse repetition rate (1–10,000 Hz), laser fluence (0.1–5 J/cm2) and pulse duration (5 ns and 100 ns). In our study, the best ablation efficiency (η ≅ 0.3 mm3/J) was obtained with the highest repetition rate (10 kHz) at the fluence F = 1.5 J/cm2. This ablation efficiency can be associated with heat accumulation at high repetition rate, which leads to the ablation threshold decrease. Despite the low thermal diffusivity and the low optical absorption of the paint (thermal confinement regime), the ablation th…

A library of monoalkenylsilsesquioxanes as potential comonomers for synthesis of hybrid materials

2018

In this paper we demonstrate a facile and efficient synthesis of monoalkenylsubstituted POSS compounds, i.e., R7(Si8O12)-alkenyl and R7(Si8O12)(OSiMe2)-alkenyl with a functional alkenyl group of chain length (from vinyl to dec-9-enyl, with or without additional –OSiMe2– spacer between the silsesquioxane core and alkenyl moiety) and with five types of inert groups (Et, iBu, iOc, Cy, Ph) at the POSS core. These compounds constitute a library of monosubstituted POSS systems, including thorough spectroscopic and thermal characteristics. These findings could be especially useful for material chemists applying the compounds as modifiers or comonomers for copolymerization reaction, e.g., with olef…

Thermal and thermo-oxidative stability and kinetics of decomposition of PHBV/sisal composites

2017

The decomposition behaviours of composites made of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and sisal were assessed in terms of thermal stability and decomposition kinetics, under inert and oxidative conditions, by means of multi-rate linear non-isothermal thermogravimetric experiments. A statistical design of experiments was applied to study the influence of the addition of sisal (0-10-20-30%wt), the presence coupling agent (Yes/No) and the applied conditions of work (inert or oxidative). An improvement of the thermal and thermo-oxidative stability of PHBV with the addition of sisal was observed for all cases. An accurate methodology based on iso-conversional methods was applied…

Applications and non-idealities of submicron Al–AlOx–Nb tunnel junctions

2016

We have developed a technique to fabricate sub-micron, 0.6µm×0.6µm Al-AlOx-Nb tunnel junctions using a standard e-beam resist, angle evaporation and double oxidation of the tunneling barrier, resulting in high quality niobium, as determined by the the high measured values of the critical temperature TC ∼ 7.5 K and the gap ∆ ∼ 1.3 meV. The devices show great promise for local nanoscale thermometry in the temperature range 1 - 7.5 K. Electrical characterization of the junctions was performed at sub-Kelvin temperatures both with and without an external magnetic field, which was used to suppress superconductivity in Al and thus bring the junction into a normal-metal-insulator-superconductor (NI…

Environmental Effects on Mechanical, Thermophysical and Electrical Properties of Epoxy Resin Filled with Carbon Nanofillers

2019

The aim of this work was to establish the effect of environmental factors (moisture and temperature) on some mechanical, electrical and thermal properties of epoxy-based composites filled with carbon nanofillers: nanotubes (CNT), nanofibers (CNF) and hybrid nanofiller (nanotubes/nanofibers in the ratio 1:1) and to reveal the most environmentally stable NC. First, the nanocomposites (NC) containing different nanofiller contents were prepared to evaluate electrical percolation threshold and to choose NC at certain electrical conductivity for further characterization of the physical properties in initial state and during/after environmental ageing. The environmental ageing consisted of water a…

Thin film conductivity measurements of carbon nanotube hemicellulose complex

2014

Työssä mitattiin hiilinanoputkista ja hemiselluloosasta koostuvan läpinäkyvän ohutkalvon sähkönjohtavuutta. Materiaali on Nemcel Oy:n kehittämä. Valmistimme useita näytteitä erilaisia mittauksia varten ja testataksemme eri valmistusmenetelmiä. Valmistetun ohutkalvon merkittävimmät ominaisuudet ovat läpinäkyvyys ja hyvä sähkönjohtavuus. Valmistetut kalvot olivat pääasiassa läpinäkyviä, mikä edellytti kalvon ohuutta. Itse materiaali toimitettiin vesiliuoksena, jossa oli 1:1 hiilinanoputkia ja hemiselluloosaa. Kalvot valmistettiin joko spinnaamalla tai kuivattamalla yksittäisiä pisaroita pinnalle. Näytteet valmistettiin pintaoksidioidulle piille, johon oli tehty kultaelektrodit. Kalvoa kuvatti…

Carbon nanotube derivatives for electro-optical active bulk heterojunctions

2012

Oxidation-responsive and "clickable" poly(ethylene glycol) via copolymerization of 2-(methylthio)ethyl glycidyl ether

2016

Poly(ethylene glycol) (PEG) is a widely used biocompatible polymer. We describe a novel epoxide monomer with methyl-thioether moiety, 2-(methylthio)ethyl glycidyl ether (MTEGE), which enables the synthesis of well-defined thioether-functional poly(ethylene glycol). Random and block mPEG-b-PMTEGE copolymers (Mw/Mn = 1.05-1.17) were obtained via anionic ring opening polymerization (AROP) with molecular weights ranging from 5 600 to 12 000 g·mol-1. The statistical copolymerization of MTEGE with ethylene oxide results in a random microstructure (rEO = 0.92 ± 0.02 and rMTEG E = 1.06 ± 0.02), which was confirmed by in situ 1H NMR kinetic studies. The random copolymers are thermorespon…

Progress in HAXPES performance combining full-field k-imaging with time-of-flight recording

2019

Journal of synchrotron radiation 26(6), 1996-2012 (2019). doi:10.1107/S1600577519012773