Glass-ceramics machinability

Fig. 3. Replica electron micrograph showing "house-of-cards" microstmcture in a machinable fluormica glass-ceramic (white bar = 10 fiva).

Phospha.tes. Many phosphates cl aim unique material advantages over siUcates that make them worth the higher material costs for certain apphcations. Glass-ceramics containing the calcium orthophosphate apatite, for example, have demonstrated good biocompatibiUty and, in some cases even bioactivity (the abiUty to bond with bone) (25). Recent combinations of fluorapatite with phlogopite mica provide bioactivity as well as machinability and show promise as surgical implants (26). 

W. Holand, W. Vogel, K. Nauman, J. Gummel, Interface reactions between machinable bioactive glass-ceramics and bone, J. Biomed. Mater. Res. 19 (1985) 303-312. 

Cere Vita Mark It Machinable glass ceramic Vita Zahnfabrik, Bad Sackingen, Germany... 

Hochberg and Bosse of E. I. DuPont de Nemours, with the "Sand Grinder" patent (6) took the idea of using small spherical media in the form of Ottawa silica sand with an average diameter of. 7 mm to a practical machine. Later glass, ceramic and steel media materials would become available and sand grinders would evolve into bead mills, shot mills, and small media mills. (Figure )... 

An important advantage of ULE (Coming) is the possibility to fabricate lightweight blanks because of the low density of 2.21 g.cm 3 of the glass itself (glass ceramics have values between 2.5 and 2,6 g.cm"3) and because of using special machined and fused core structures and bonding techniques [67]. 

The E-design stack, shown in Fig. lA, consists of a relatively thick metallic interconnect with machined gas channels on both sides and a metallic picture frame for the cell, brazed to the interconnect by a metal solder. Sealing is obtained by glass ceramic sealants applied to the planar cell and frame surfaces using an automated dispenser. A fine Ni-mesh is spot-welded to the fuel side of the interconnect in order to improve the electrical contact between interconnect and anode substrate. On the air side usually a lanthanum cobaltite (LC) contact layer is sprayed onto the ribs of the interconnect. 

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