Search results for " fisica"
showing 10 items of 4804 documents
Supercooled Water Confined in a Silica Xerogel: Temperature and Pressure Dependence of Boson Peak and of Mean Square Displacements
2013
A silica xerogel can be obtained from an alcoxide precursor (TMOS, tetramethylortosilcate) via the sol-gel method: TMOS hydrolysis and subsequent polycondensation yields a solid, disordered, porous SiO2 matrix (average pore dimensions ~20Å). Inside the pores water is trapped and the hydration level h=gr[H2O]/gr[SiO2] can be easily controlled. The presence and temperature dependence of the boson peak (BP) in xerogel confined supercooled water was studied with inelastic neutron scattering (spectrometer IN6 at ILL, Grenoble) in xerogel samples having h=0.4 and h=0.2. After careful subtraction of the contributions arising from the matrix and from quasi-elastic scattering, the BP contribution wa…
Stability of sol-gel silica glass for CPV and ultraviolet LED applications
2011
This paper concerns the characterization of silica glass obtained by a sol-gel technique as to its suitability in the terrestrial and space concentrated photovoltaic (CPV), and ultraviolet light emitting diode (UV LED) industrial sectors. The sol-gel material tested is produced by Evonik Industries and marketed under the brand name SAVOSIL™. The tests performed were aimed at determining the endurance of the material to radiation exposure and consist of exposure to gamma radiation and 355 nm UV laser light. In these tests the transmittance of the glass was measured before and after the exposure to the radiation to determine the effect of the radiation treatment. In the case of the test with …
Resonance Raman of oxygen dangling bonds in amorphous silicon dioxide
2017
We investigate the origin of a resonance Raman band induced by ionizing radiation in amorphous silicon dioxide (silica glass), which can be detected under ultraviolet laser excitation. A silica sample, rich of oxygen-excess related defects, was prepared by treating some length of a pure-silica-core multimode fiber in an O2 atmosphere (at high temperature and pressure) and by irradiating it with X-rays at 10 MGy(SiO2) dose. A micro-Raman study revealed a gaussian band peaking at 896 cm−1 with a full width at half maximum of 32 cm−1, which could be detected by exciting the sample with the 325-nm line of a HeCd laser. This spectral feature is absent in the Raman spectra performed with the 442-…
Comparison of gamma and beta-ray irradiation effects in sol-gel Ge-doped SiO2
2009
Effects of Excimer Laser Irradiation on the Morphological, Structural, and Electrical Properties of Aluminum-Implanted Silicon Carbide (4H-SiC)
2022
This paper reports on the effects of excimer laser irradiation on an aluminum (Al)-doped silicon carbide (4H-SiC) layer. Specifically, high-concentration (1 × 1020at/cm3) Al-implanted 4H-SiC samples were exposed to a few pulses of 308 nm laser radiation (pulse duration of 160 ns), with fluence varying from 1.0 to 2.8 J/cm2. As a starting point, the laser-induced modifications of the morphological, microstructural, and nanoelectrical properties of the exposed 4H-SiC surface were monitored by combining different techniques. From these investigations, an evolution of the surface morphology was observed that can be ascribed to a conversion during irradiation of the uppermost part of the 4H-SiC …
Amorphous silicon nanotubes
2017
In the following, the attention will be focused on the silicon nanotube (SiNTs) that is a highly desired form of silicon for its fundamental role in the miniaturization trend of the electronic devices. After a description of the properties and applications of SiNTs and their fabrication methods, the attention will be focused on chemical vapour deposition (CVD) template synthesis that is the most usual synthetic method for this material. Then, galvanic template synthesis will be described as a general method for the fabrication of different metals and oxides nanostructures, therefore the use of this technique for synthesizing SiNTs will be detailed. Characterization methods will be also desc…
Temperature-responsive hybrid nanomaterials based on modified halloysite nanotubes uploaded with silver nanoparticles
2022
New temperature-responsive hybrid nanomaterials based on modified halloysite nanotubes (HNTs) containing grafted polymer brushes with silver nanoparticles have been successfully fabricated. We used a three steps process including synthesis of the initiating coatings onto HNTs surface, fabrication of the POEGMA – poly(oligo(ethylene glycol)ethyl ether methacrylate) grafted brushes and synthesis of the silver nanoparticles (AgNPs). The synthesis and properties of hybrid nanomaterials were studied by FT-IR, TGA and DLS methods. It is shown that the introduction of AgNPs, formed from 0.005 M AgNO3 solution leads to a significant reduction of low critical solution temperature (LCST) of the polym…
Ricerca sulla simulazione del funzionamento in regime vario di forni continui per la cottura di ceramiche e porcellane
2005
Un modello realistico per visualizzazioni in didattica
2019
In this work, two applications for the visualization of the aggregation and the solubilization of structureless interacting particles are presented. The applications allow to demonstrate on a qualitative basis as well as by quantitatively monitoring the time evolution of the surface/volume ratio and of the fractions of aggregated particles, that, on the one hand, the growth of nanoaggregates implies a decrease of their surface/volume ratio and, on the other, that the formation of homogeneous mixtures is the result of favorable solute-solvent interactions as well as of temperature. It is suggested that, along with the use of suitable macroscopic examples, visualizations by the present applic…