resumo
The effects of K2O content on sintering and crystallization of glass powder compacts in the Li2O-K2O-Al2O3-SiO2 system were investigated. Glasses featuring SiO2/Li2O molar ratios of 2.69-3.13, far beyond the lithium disilicate (LD-Li2Si2O5) stoichiometry, were produced by conventional melt-quenching technique. The sintering and crystallization behaviour of glass powders was explored using hot stage microscopy (HSM), scanning electron microscopy (SEM), differential thermal (DTA) and X-ray diffraction (XRD) analyses. Increasing K2O content at the expense of SiO2 was shown to lower the temperature of maximum shrinkage, eventually resulting in early densification of the glass-powder compacts. Lithium metasilicate was the main crystalline phase formed upon heat treating the glass powders with higher amounts of K2O. In contrast, lithium disilicate predominantly crystallized from the compositions with lower K2O contents resulting in strong glass ceramics with high chemical and electrical resistance. The total content of K2O should be kept below 4.63 mol% for obtaining LD-based glass ceramics. (C) 2012 Elsevier Ltd. All rights reserved.
palavras-chave
LITHIUM DISILICATE GLASS; FIXED VISCOSITY POINTS; LI2O-SIO2 GLASSES; CERAMICS; CLAY; TEMPERATURE; NUCLEATION; KINETICS; BEHAVIOR; AL2O3
categoria
Materials Science
autores
Fernandes, HR; Tulyaganov, DU; Pascual, MJ; Kharton, VV; Yaremchenko, AA; Ferreira, JMF
nossos autores
Aleksey Yaremchenko
Investigador Principal
Hugo Alexandre Gonçalves da Rocha Fernandes
Investigador Júnior
José Maria da Fonte Ferreira
Professor(a) Jubilado(a)
Vladislav Kharton
Investigador Principal CovidadoGrupos
G3 - Materiais Eletroquímicos, Interfaces e Revestimentos
G5 - Materiais Biomiméticos, Biológicos e Vivos
agradecimentos
Financial support from CICECO, University of Aveiro, and from the FCT, Portugal (grant SFRH/BD/41307/2007 and project PTDC/CTM-CER/114209/2009) are gratefully acknowledged.