On the sinterability of crystallizing glass powders

Author(s)

Prado, Miguel Oscar ^[1] ; Ferreira Nascimento, Marcio Luis ^[2] ; Zanotto, Edgar Dutra ^[2]

Affiliation

^[1] Ctr Atom Bariloche, Comis Nacl Energia Atom, CONICET, San Carlos De Bariloche, Rio Negro - Argentina

^[2] Univ Fed Sao Carlos, Lab Mat Vitreos, BR-13565905 Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: Journal of Non-Crystalline Solids; v. 354, n. 40-41, p. 4589-4597, OCT 15 2008.
• Web of Science Citations: 28

Abstract

We define an adimensional parameter, S, that is capable of predicting if a glass powder compact can be fully densified by viscous flow sintering or if concurrent surface crystallization will hinder densification. The proposed sinterability parameter is S(T) = gamma/left perpendicular root N-s.U(T).n(T).rright perpendicular, where gamma is the glass-vapor surface energy, N-s the density of nucleation sites on the glass surface, U(T) the crystal growth rate, n(T) the viscosity, and r the average particle radius. For high temperatures, T >= 0.85T(m), where T-m is the melting point of the crystal phase, an approximate expression can be used: S-ht(T) = 2 pi.gamma.N-A.T-m(2).(3)root V-m(2)/{[}10 root N-s.r.Delta H-m.Delta T-2], where V, is the molar volume, N-A is Avogadro's number, Delta H-m is the melting enthalpy of the crystal phase, and Delta T = T-m - T is the undercooling. This expression avoids the (time consuming) measurement of U(T) and n(T). Predictions can be made by S or S-hT thus avoiding the need of any sintering experiment. For a given glass-forming composition the physical properties are fixed, but higher temperatures and smaller particle sizes increase S and privilege sintering over surface crystallization. We demonstrate that the condition to successfully densify any glass powder at a given temperature is S > 50. This new parameter is a very useful aid for the development of sintered glasses and glass-ceramics. (c) 2008 Elsevier B.V. All rights reserved (AU)

• FAPESP's process: 07/08179-9 - Kinetic processes in glasses and glass ceramics
• Grantee: Edgar Dutra Zanotto
• Support Opportunities: Research Projects - Thematic Grants