New oxyfluoride glasses based on the system ZrO2-Pr2O3-ZrF4-BaF2 were obtained, and the glass forming ability of this system was evaluated. The effects of glass composition on both thermal
stability and the crystalline phases formed upon heat treatment were determined by the DSC and XRD methods, respectively.
The composition with higher thermal stability and better glass forming ability contained 2 mol% of oxides.
Authors:J. Delben, A. Delben, K. Miazato, S. Oliveira, and Y. Messaddeq
New fluorindate glass compositions have been investigated in order to improve optical transmission as well as thermal properties.
Chloride inclusion extends transmission of a fluoride matrix to longer wavelength in infrared region. In the present work
thermal parameters of an IZnBS composition, based on InF3, ZnF2, BaF2 and SrF2, with various amounts of alkaline chlorides were investigated by differential scanning calorimetry. The chloride presence
decreased all characteristic temperatures and increased both thermal stability and glass forming ability up to 10% of MCl
content, where M=Li, Na, K and Rb. The presence of NaCl promoted glass phase separation. For samples containing same concentration of NaCl,
this effect is accentuated for increasing the contents of SrF2.
Authors:J Delben, D Chaves, P Candelorio, and A Delben
New glasses have been synthesized in the system ZrF46BaF26PrF3. Glasses were prepared by conventional fusion method and the
vitreous domain was established. For vitreous samples the thermal stability
parameters were determined, so that the best compositions could be selected
according to a compromise between high glass forming ability and thermal stability
Authors:A. Delben, F. Menezes, J. Delben, M. Coelho, and R. Ribeiro
Waste compromises environmental preservation as well human health in
many countries. Recycling is an alternative that sometimes represents the
only economical activity for a significant population in the big cities. Almost
3% of waste materials in Brazil are vitreous. Ceramic production adding waste
glass is possible with advantages of costs reduction associated to decrease
on firing temperatures and to the raw material itself. At present paper up
to 80 mass% of waste glass was added to clay. The sintering temperature decreased
linearly and the shrinkage increased with glass content, an effect more pronounced
for high glass amount.
Authors:P. Melnikov, R. Rolim, A. Delben, J. Delben, A. Souza, and A. Job
Xerogels were prepared from zirconium, barium, aluminum, lanthanum and lithium acetates, corresponding to a Li containing ZBLA composition. The study of their thermal properties (DSC, TG/DTG, FT-IR) showed that they might be used as chemically stable precursors in the preparation of fluoride glasses. Hydrofluoric acid in solution was chosen as a mild fluorinating agent. This newly proposed technique of fluorinating allowed to obtain high quality ZBLALi glass which presents the advantage of higher thermal stability and homogeneity in comparison with the glass obtained using individual commercial fluorides.
Authors:J. Delben, P. Candelorio, F. de Oliveira, T. Spontoni, Angela Delben, M. Coelho, and L. Andrade
Petroleum natural gas (PNG) reserves will last even when the oil reserves are exhausted, requiring the development of technologies
for PNG storage. Activated charcoal is the best material for such a purpose. Under vacuum samples of aroeira (Astronium Urundeuva)
underwent pyrolysis in diverse conditions. The samples were characterized by thermal analysis, scanning electronic microscopy
and infrared spectroscopy. When the pyrolysis temperature increased, mechanical anisotropy resistance tended to disappear.
The pyrolysis became complete only at high temperatures and using a long time of treatment.