Search results for "Annealing"
showing 10 items of 434 documents
Effect of antisite defects on the magnetic properties of ZnFe2 O4
2013
Magnetic zinc ferrite (ZnFe2O4) nanopowders were synthesized using the sol–gel autocombustion method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements demonstrated that thermal decomposition of the 1-mm-thick xerogel layers in air formed monophasic spinel ferrite nanopowders with a particle size less than 30 nm. X-ray photoelectron spectroscopy (XPS) showed that the obtained reaction product contained antisite defects, with zinc ions occurring at the octahedral sites of the spinel structure. The concentration of antisite defects or inversion degree decreased when the relatively low annealing temperature was increased from 150 to 500 °C. Overall, the obtained ZnFe2…
'Cold' crystallization in nanostructurized 80GeSe2-20Ga2Se3 glass
2015
International audience; 'Cold' crystallization in 80GeSe 2-20Ga 2 Se 3 chalcogenide glass nanostructurized due to thermal annealing at 380°C for 10, 25, 50, 80, and 100 h are probed with X-ray diffraction, atomic force, and scanning electron microscopy, as well as positron annihilation spectroscopy performed in positron annihilation lifetime and Doppler broadening of annihilation line modes. It is shown that changes in defect-related component in the fit of experimental positron lifetime spectra for nanocrystallized glasses testify in favor of structural fragmentation of larger free-volume entities into smaller ones. Nanocrystallites of Ga 2 Se 3 and/or GeGa 4 Se 8 phases and prevalent GeSe…
Nanostructured metal/oxide coatings
2007
Al based nanocomposite coatings on Cu and glass substrates were obtained in the conditions of severe shear stresses by deformation scheme similar to that of friction. Structure, composition and micromechanical properties were investigated using AFM, XRD, SIMS, electron, optical microscopy and precision microindentation techniques. Coatings are characterized by the high microhardness and good adhesion to the substrates. This is determined by the formation of nanostructured Al-oxide composite stabilized by the presence of oxidized interlayers, which are barriers for the grain growth and intermetallic phase formation. The annealing in vacuum leads to the development of oxygen redistribution pr…
Growth and size distribution of Au nanoparticles in annealed Au/TiO2 thin films
2014
Abstract Nanocomposites consisting of noble metal nanoparticles (NPs) embedded in TiO2 thin films are of great interest for applications in optoelectronics, photocatalysis and solar-cells for which the plasmonic properties of the metal NPs play a major role. This work investigates the first stages of the formation of gold NPs by thermal annealing of Au-doped TiO2 thin films grown by magnetron sputtering. A low concentration of gold in the films is considered (5 at.%) in order to study the first stages of the formation of the NPs. Raman spectroscopy is used to follow the crystallization of TiO2 when increasing the annealing temperature. In addition, low-frequency Raman scattering (LFRS) is u…
In Situ Heating TEM Study of Onion-like WS2 and MoS2 Nanostructures Obtained via MOCVD
2007
We report on the in situ heating transmission electron microscopy (TEM) study of WS2 and MoS2 nanoparticles obtained from metal–organic chemical vapor deposition (MOCVD). The general behavior of MoS2 and WS2 is similar: Round, amorphous particles in the pristine sample transform to hollow, onion-like particles upon annealing. A second type of particle with straight layers exhibits only minor changes. A significant difference between both compounds could be demonstrated in their crystallization behavior. The results of the in situ heating experiments are compared to those obtained from an ex situ annealing process under Ar.
Influence of electrolyte temperature on the synthesis of iron oxide nanostructures by electrochemical anodization for water splitting
2018
[EN] Iron oxide nanostructures are an attractive option for being used as photocatalyst in photoelectrochemical applications such as water splitting for hydrogen production. Nanostructures can be obtained by different techniques, and electrochemical anodization is one of the simplest methods which allows high control of the obtained morphology by controlling its different operational parameters. In the present study, the influence of the electrolyte temperature during electrochemical anodization under stagnant and hydrodynamic conditions was evaluated. Temperature considerably affected the morphology of the obtained nanostructures and their photoelectrochemical behavior. Several techniques …
Synthesis and characterization of ZnO/ZnS/MoS2 core-shell nanowires
2017
The present research was supported by the Latvian National Research Program IMIS2 . Authors are grateful for Dr. Robert Kalendarev and Martins Zubkins for assistance in magnetron sputtering, Dr. Krisjanis Smits for TEM measurements, Dr. Roberts Zabels for AFM measurements and Reinis Ignatans for XRD measurements.
Structural and chemical analysis of annealed plasma-enhanced atomic layer deposition aluminum nitride films
2016
Plasma-enhanced atomic layer deposition was utilized to grow aluminum nitride (AlN) films on Si from trimethylaluminum and N2:H2 plasma at 200 °C. Thermal treatments were then applied on the films which caused changes in their chemical composition and nanostructure. These changes were observed to manifest in the refractive indices and densities of the films. The AlN films were identified to contain light element impurities, namely, H, C, and excess N due to nonideal precursor reactions. Oxygen contamination was also identified in the films. Many of the embedded impurities became volatile in the elevated annealing temperatures. Most notably, high amounts of H were observed to desorb from the…
Mechanical, degradation and drug-release behavior of nano-grained Fe-Ag composites for biomedical applications.
2018
Abstract An original fabrication route of high-strength bulk Fe-5Ag and Fe-10Ag nanocomposites with enhanced degradation rate is reported. Near fully dense materials with fine nanostructures and uniform distribution of Ag nanoparticles were obtained employing high energy attrition milling of Fe-Ag2O powder blends followed by cold sintering – high pressure consolidation at ambient temperature that allowed the retention of the nanoscale structure. Annealing in hydrogen flow at 550 °C resulted in enhanced ductility without coarsening the nanostructure. The strength in compression of Fe5Ag and Fe10Ag nanocomposites was several-fold higher than the values reported for similar composites with mic…
New process of silicon carbide purification intended for silicon passivation
2017
Abstract In this work, we report on a new, efficient and low cost process of silicon carbide (SiC) powder purification intended to be used in photovoltaic applications. This process consists on the preparation of porous silicon carbide layers followed by a photo-thermal annealing under oxygen atmosphere and chemical treatment. The effect of etching time on impurities removal efficiency was studied. Inductively coupled plasma atomic emission spectrometry (ICP-AES) results showed that the best result was achieved for an etching time of 10 min followed by gettering at 900 °C during 1 h. SiC purity is improved from 3N (99.9771%) to 4N (99.9946%). Silicon carbide thin films were deposited onto s…