1,721,063 research outputs found
La modellazione a calcolatore nella scienza dei materiali
No full textTecniche di modellazione a calcolatore nella scienza dei material
La modellazione quale strumento per la previsione del comportamento e delle funzionalità
No full textSimulazioni computazionali per lo studio di materiali di interesse applicativo
No full textdescrizione di tecniche di modeling per materiali di interesse applicativ
Short range order characterization of materials belonging to the CaO-MgO-Al2O3-SiO2 system: a molecular dynamic study
No full textcharacterization of glasses belonging to the CaO-MgO-Al2O3-SiO2 system by MD simulation
What Can We Learn From Molecular Dynamics Simulations of Glasses Belonging to the Na2O-Al2O3-SiO2 system?
No full textAlumino silicate glasses (NAS) represent an interesting class of materials especially in virtue of their final physical and chemical properties. Several model have been proposed to interpret the macroscopical behavior of this ternary system and in the last year computer simulations have been also largely used as useful complementary tool for the NAS glass structure characterization.In this work we present the comparison between experimental and theoretical data obtained for a large range of composition (R= Al/Na from 0.0064 up to 2) of alumina containing glasses
Structural characterization of erbium containing glasses by using molecular dynamics simulations
No full textErbium containing glasses cover an important role in optical communications such as optical amplifiers. It is well know that the concentration of erbium into the glass influences the optical response of the material, therefore in the last years particular attention was devoted to the analysis and characterization of the erbium local distribution in the glass network. The presence of high erbium concentration in the glass is correlated to the formation of Er3+ based clusters and this inhomogeneous distribution of the rare earth ions induces changes in the energy transfer between neighbouring ions leading to the concentration quenching of luminescence, experimentally observed for this class of optical materials. In this communication, the structural evolution occurring in the erbium sites, its modifier role and the changes induced by the alumina addition in the glasses have been extensively studied by using molecular dynamics technique. The effect of alumina on the clustering effect, typical of the glasses containing high erbium concentration, was defined for three main systems characterized by the presence of increased percentage of erbium oxide in the glass formulation
Microstructure-based modelling and experimental investigation of crack propagation in glass-alumina functionally graded materials
No full textThe aim of the present work was the determination of the fracture mechanisms in glass-alumina functionally graded materials (FGMs). The investigation was performed by means of a combined approach based on microscale computational simulations, which provided for an accurate modelling of the actual FGM microstructure, and experimental analysis. The numerical results proved that microstructural defects, such as pores, deeply influenced the damage evolution. On the contrary, the minimization of the mismatch in the coefficients of thermal expansion of the ingredient materials allowed to obtain low thermal residual stresses, which did not relevantly affect the crack propagation. In order to support the numerical model, microindentation tests were performed on the cross-section of FGM specimens and the experimentally observed crack paths were compared to the computationally predicted ones. (c) 2005 Elsevier Ltd. All rights reserved
Local and medium range structure of erbium containing glasses: a molecular dynamics study
No full textErbium containing glasses cover an important role in optical communications and laser technology. The local environment of the ionsconstituting the three dimensional network exerts a strong influence on the chemical and physical properties of the glasses. In particularthe network modifier cations strongly influence the short and intermediate range order of the glass structure. The structural modificationsinduced by the alumina addition in the glass matrix, as a function of the erbium oxide concentration, have been studied using moleculardynamics (MD) simulations. While at low Er2O3 concentration the network former action of the Al3+ leads to a more polymerized glassnetwork, at higher Er2O3 content the influence of the alumina on the erbium local structure is limited. Further investigation points outmicro-heterogeneity in the Na+ and Ca2+ distribution as a function of the alumina concentration
On a solar reflective ceramic based glaze for asphalt shingle
No full textSolar reflective materials are one of the most effective solutions to counteract Urban Heat Island effect. Among them, asphalt shingles are one of the most widely used products. To improve solar reflectance of these surfaces usually both polymeric paint on the final product or ceramic glazes applied directly on the granules surface through rotary kiln are used. In this study the Design of Experiment approach is applied to an industrial formulation for ceramic glaze for asphalt shingles in order to find the optimal combination between pigment (Rutile and Talc), liquid phase (Sodium Silicate and Water) and heat treatment (700 °C â1100 °C). On the most significant samples, moreover, XRD and ESEM characterization has been performed in order to better understand the behaviour of the studied system. Interesting values in Solar reflectance were obtained, reaching Ïsol=0.882 creating a good solar reflective product ready to be applied, through rotary kiln, on mineral granules for asphalt shingles
Investigation of the mechanical properties of Mo-reinforced glass-matrix composites
No full textOne approach for reducing the inherent brittleness and flaw sensitivity of glass is to fabricate a composite material by incorporating particles or fibers in the glass matrix. In order to fully understand the toughening mechanisms in composites, it is useful to develop predictive models able to describe the mechanical behavior and its dependence on microstructure. To this aim, numerical models can be used in order to assess the effect of the glass-matrix composite microstructure on the effective macroscopic mechanical and fracture properties. An innovative microstructure-based finite element code is used to describe the mechanical performance of glass matrix composites. This code is able to convert digitized images of the material microstructure into a finite element grid, so that all microstructural details such as inclusion size, morphology and volume fraction can be incorporated in the model. In this study, a borosilicate glass matrix composite reinforced with molybdenum particles is characterized using the aforementioned microstructure-based FEM approach in terms of residual stresses and elastic properties
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