DELAYED FAILURE HYDROGEN EMBRITTLEMENT OF ZIRCONIUM. Summary Report, September 15, 1961 to September 14, 1962

Abstract

-ii -

Kinetics of isothermal phase transformations in a dental porcelain

“…component no. 2 of the Weinstein et al patent [1]). They are large (20-50 ~tm), and they are outlined by small (about 1 gm) leucite crystals.…”

“…Porcelain-fused-to-metal (PFM) is a widely used dental restoration in which several layers of porcelain are successively applied and fired in vacuum onto a metal framework which has been previously modelled and cast according to the anatomical conditions [1,2]. Porcelains for PFM restorations are very different in composition and structure from the traditional or tri-axial porcelains (that is, those made by the blending and the firing of clay, quartz and potassium feldspar) [3].…”

“…The softening behaviour and the opacity of the porcelain, are also determined by the amount of leucite [3]. The suitable quantity of leucite in the porcelain (20-30 vol % [3]) is achieved by ~ome of the following procedures: (a) a controlled crystallization of the starting glass by means of an annealing treatment [4]; (b) the addition of powdered synthetic leucite to a powdered glass [14]; (c) the blending of two (or more) distinct glassy frits, one of them being a glass (low-fusion/low-contraction frit), and the other being a crystallized glass obtained by incongruent (peritectic) melting of potassium feldspar to leucite plus liquid, that becomes leucite plus glass upon cooling (high-fusion/high-contraction frit) [1,2].…”

“…These are reconstructive (also termed nucleation and growth) transformations that occur above about 800°C [2,5]. They are sluggish and irreversible.…”

“…In addition, the The commercial dental porcelain selected for this 850 study was Ceramco dentin body (Ceramco, Inc., New 850 York 11101, USA). According to [36], it is based upon 850 the Weinstein et al patents [1,2]. The starting powder 900 900 was characterized by emission spectroscopy (semi-900 quantitative analysis) and X-ray diffraction (XRD) in a 900 previous work [8].…”