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Matéria (Rio de Janeiro)
versão On-line ISSN 1517-7076
YOSHIMURA, H.N.; GUEDES, S. e FREDECICCI, C.. Glass dielectric with high mechanical and thermomechanical reliability produced by two-step tempering (thermal tempering + ion exchange). Matéria (Rio J.) [online]. 2009, vol.14, n.2, pp.845-860. ISSN 1517-7076. http://dx.doi.org/10.1590/S1517-70762009000200007.
In this work, the possibility to enhance the mechanical and thermomechanical performance of glass dielectric by the two-step tempering, short-time ion exchange following thermal tempering, was investigated. The soda-lime silicate glass dielectrics were produced by pressing in an industrial plant, where the thermal tempering was conducted with quenching from 580ºC using forced air in a tempering fixture (tournettes) and the ion exchange was performed using a KNO3 bath at 450ºC for 30 min. The dielectric treated by the two-step tempering method showed, in relation to the conventional dielectric (thermal tempered), better performances in the thermal shock tests (heating, cooling and thermal cycling) and higher values of Weibull modulus, m, for breaking loadin compression and for breaking time in heating thermal shock, while the mechanical properties (breaking load in compression and absorbed energy in impact) remained high, at the levels achieved by the thermal tempering. The effects caused by the second stage (ion exchange) are discussed in terms of the formation of a residual stress profile which enhances the mechanical and thermomechanical reliability, as a consequence of simultaneous action of ion-stuffing and stress relaxation mechanisms during the ion exchange treatment.
Palavras-chave : Dielectric; glass; tempering; ion exchange; mechanical properties; thermal shock; Weibull analysis; reliability.