1994, Durschang, Bernward R., Carl, Gunter, Rüssel, Christian, Marchetti, Kurt, Roeder, Erwin

Glass-ceramics with oriented crystals have been produced from a lithium disilicate glass system by extruding the nucleated glass below the crystallization temperature, and subsequent heat treatment to achieve high-crystalline glass-ceramics. The extruded glass was found to possess a small amount of ahgned, elongated lithium disilicate crystallites and anisotropic stresses. The resulting glassceramic shows a high orientation of the needle-shaped Li₂Si₂O₅ crystals with their c-axis parallel to the extrusion direction. The degree of crystallographic orientation was found to be decreased for samples with an additional heat treatment slightly above Tg, placed between the extrusion process and the crystallization. The crystal alignment of specimens extruded below crystallization temperature is significantly higher than the alignment o f extruded glass-ceramic.

1994, Rammo, Manfred, Roeder, Erwin

Continuous pull extrusion represents an important further development of the traditional extrusion process. It enables the manufacturing of arbitrary endless inner and outer profiles of glasses for common and special technical applications with a high trueness of shape and precision in a markedly more economical way than by the usual discontinuous extrusion method. This is achieved by a continuous supply of the glass into the equipment in connection with a considerable saving of the up to now unavoidable setting periods. The drawing process immediately following the extrusion procedure itself permits a defined cross-sectional diminishing of the extruded profiles and causes together with this a rectilinear straightening of the products.

1996, Eifler, Dietmer, Roeder, Erwin, Schlicker, Uwe, Wagner, Jochen

The joining technology of glasses and glass-ceramics with metal is growing in importance in view of the increased application possibilities of such Compound parts in the machinery and electronics industries. Α new method has recently gone into competition with the current production methods of these Compounds such as melting, soldering and glueing. This novel method is ultrasonic welding. So far this joining technology has only been applied in ultrasonic spot welding. However, it is n ow possible to manufacture Compounds with a shear strength of up to 50 MP a at low temperatures (< 400°C) in short periods of time (< 1.5 s). To extend the application of ultrasonic welding the Department of Materials Science at the University of Kaiserslautern (Germany) has constructed and put into Operation an ultrasonic roll seam welding machine for the continuous and intermittent joining of glass and glass-ceramics with metal. So far this device has, among other things, been used to join a borosilicate and a soda-lime-silica glass with several kinds of high alloyed steel, an aluminium alloy and the glass sealing alloy KOVAR (NiCo 29 17) with the addition of a thin intermediate layer of aluminium. By means of systematic studies of the parameters feed, welding force and amplitude, that significantly influence the welding process, an optimization of the Compound strength has been achieved.

1997, Habelitz, Stefan, Carl, Gunter, Rüssel, Christian, Marchetti, Kurt, Roeder, Erwin, Eifler, Dieter, Hergt, Rudolph

Glass-ceramics with oriented mica crystals have been produced by extruding a fluorophlogopite glass and subsequent therma treatment. During extrusion predominantly the intermediate phase norbergite (Mg₃F₂SiO₄) and besides small quantities of phlogo pite mica crystals (Na/KMg₃F₂Si₃AlO₁₀) crystallized. Heat treatments at temperatures around the maximum crystallization rat resulted in an oriented crystallization of phlogopite as proved by electron microscopy and XRD analysis. The plate-like crystals ar aligned with their basal planes parallel to the direction of extrusion. The degree of orientation was studied by X-ray pole figur measurements. The (003) planes show strong ring-fibre texture. The degree of orientation decreased if the crystallization was realize at lower temperatures and lower crystallization rates. The alignment mechanism is discussed.