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Silicon nitride is a ceramic material of great interest to advanced engine construction and mechanical engineering owing to an outstanding combination of favorable properties like high mechanical strength at high temperatures, corrosion and wear resistance, great hardness, and low density. The material is based on high-quality Si,N, powders, which are shaped and sintered to the ceramic component. This overview outlines the properties required for Si,N, powders suitable for advanced ceramics. Processes in commerical use and those under development for the production of high quality Si,N, powders are discussed as well as material manufacturing processes and material properties. By steadily improving powder quality, material properties, and the economy of powder and component production, chemistry and chemical technology play a major role in recent efforts to create a solid fundament for broad applications of silicon nitride ceramics."If one would surrender to geological phantasies, one could imagine that during the formation of our planet, when elements combined to the compounds making up its crust and mountain ranges, silicon reacted with nitrogen, and the still red-hot nitrogen-silicon, on contact with water, may have decomposed to silicic acid and ammonia. Thus, ammonia may have been formed originally and nitrogen thereby introduced into the forming organic compounds when living nature first started to appear."

Aufgrund der günstigen Eigenschaftskombination von Siliciumnitridkeramik ‐ hohe Festigkeit bei hohen Temperaturen, Korrosions‐ und Verschleißbeständigkeit, große Härte und geringe Dichte ‐ist dieser Werkstoff von großem Interesse für Hochleistungsanwendungen im Maschinen‐, Motoren‐ und Turbinenbau. Die Basis der Siliciumnitridkeramik bilden hochwertige Si3N4‐Pulver, die nach der Formgebung zum Fertigteil gesintert werden. Dieser Beitrag berichtet über die Anforderungen, die an keramikgeeignete Si3N4‐Pulver gestellt werden, die kommerziell betriebenen und sich in der Entwicklung befindenden Verfahren zur Pulver‐und Werkstoffherstellung sowie über die Werkstoffeigenschaften. Chemie und chemische Verfahrenstechnik spielen eine wichtige Rolle bei den Bestrebungen, durch stetige Verbesserung der Qualität von Pulver‐ und Werkstoffeigenschaften sowie der Wirtschaftlichkeit der Pulver‐und Bauteilherstellung die Grundlage für einen breiten Einsatz der Siliciumnitridkeramik zu schaffen.

Microstructural development during liquid-phase assisted densification of Si3N4 powder compacts is a function of powder properties, type and amount of additives as well as of processing conditions (time, temperature, pressure

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