Search results for "Glass"

The interplay between structure and ionic motions in glasses

2003

We present research examples that demonstrate how molecular dynamics simulations of real materials have reached a high level of sophistication. For simplicity, we focus on examples taken from our own research-although many other groups have done similarly valuable work on other systems and problems.

Defects in glasses

1995

Abstract The absence of long range order in the glass structure allows to define only point defects in these materials. They are: 1) intrinsic defects—atomic size local deviation from short range order; 2) impurity defects—isolated impurity atoms or ions in the glass network; 3) intrinsic impurity defects—complexes consisting of the impurity atoms chemically bonded to one of the intrinsic defect atoms. The latter defects are characteristic for the doped glasses. Presence of point defects in glasses introduces new spectroscopic properties of these solid materials. Defect generation, interaction and recombination reactions resulting from the external influence causes the glass spectroscopic p…

Reactivity of SiCl and SiF groups in SiO2 glass with mobile interstitial O2 and H2O molecules

2007

Reactions of common network-bound halogens in synthetic SiO2 glass, SiCl and SiF groups, with interstitial O2 and H2O molecules incorporated by thermally annealing were studied. It was found that the chemical properties are distinctly different between SiCl and SiF groups. SiCl groups react with interstitial O2 and H2O to form interstitial Cl2 and HCl, respectively. In contrast, formation of interstitial F2 and HF due to the reaction of SiF groups with interstitial O2 and H2O is not observed. The reactivity of SiCl and SiF groups is in accord with the properties and thermodynamic data of their respective analogous compounds, SiCl4 and SiF4.

Theories of the Structural Glass Transition

2005

Ni-containing spinel aluminates glass-ceramic materials obtained from cordieritic bulk glasses

2003

Monolithic glasses with compositions 2MO � 2Al2O3 � 5SiO2, being M ¼ Ni and equimolar mixtures of Ni and Mg, were prepared at 1650 C by melting mixtures of raw materials. The crystallization of monoliths was produced by heattreatment at several temperatures up to 1200 C. The crystallization sequence was followed by differential thermal analysis (DTA), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) and diffuse reflectance spectroscopies. Surprisingly, the only crystalline phase formed after heating up to 1100 C was a nickel-containing aluminate spinel for both compositions. The microstructural characterization indicated t…

Effect of some additives on the development of spinel-based glass-ceramic glazes for floor-tiles

2005

Abstract The feasibility of developing spinel-based glass-ceramic glazes from a glass with composition in the system ZnO–MgO–B 2 O 3 –Al 2 O 3 –SiO 2 was examined. To do it additional fluxes and/or nucleants were added to a parent glass before melting. Pressed pellets of powdered glasses were submitted to standard thermal treatments up to 1200 °C. The crystallization path and the microstructural development at several temperatures were followed by several experimental techniques. The results showed that additions of TiO 2 as nucleant or additional B 2 O 3 as flux to the chosen glass favored the crystallization of cordierite or mullite as main crystalline phase. Glasses which also contained …

Phase transformation in a glass-ceramic observed by laser spectroscopy

1988

The influence of thermal treatment on a (Li2O∶Al2O3∶ SiO2) glass ceramic is studied by laser spectroscopy. At temperatures above 800 °C a fluorescence of Cr3+ ions around 693 nm appears which indicates the growth of crystallites where the Cr3+ ions occupy sites similar to those in Al2O3.

Involucri traslucidi in vetromattone

2010

Glassblock and Architecture. Evoluzione del Vetromattone e Recenti Applicazioni

2010

Il vetromattone è stato impiegato, sin dalle origini, per la risoluzione di problemi connessi alla necessità di aumentare l'apporto di luce naturale all'interno di ambienti confinati contribuendo, in tal modo, anche alla riduzione dei consumi energetici (elettrici, in particolare). La sua applicazione assolveva già in nuce, quindi, ad alcuni dei principi derivati dal più moderno concetto di “sostenibilità” applicato al settore edilizio, anche se solo oggi le ricerche condotte in ambito scientifico e produttivo mirano a tener conto sensibilmente delle problematiche ad esso connesse, soprattutto in rapporto alla produzione e messa in opera del vetromattone. Il libro trae spunto dal convegno i…

Bond characterization of monolithic and layered glass panels and ultrasonic tests to control glued surfaces

2019

Abstract An experimental investigation is presented regarding the compressive and shear strength of monolithic and PVB laminated glass elements connected by acrylic glue. Ultrasonic tests were also used to control the efficiency of glued surfaces of glass panels. Twenty-four triplets composed of three float glass elements glued with acrylic adhesive were prepared to perform bond tests. Of these twelve triplets were made with monolithic glass elements with a nominal thickness of 20 mm, while twelve were made with layered glass elements 20 mm thick. Three single elements of monolithic glass and three of layered glass were tested for compressive strength. Ultrasonic tests were performed on a s…