Abstract:
A method for making essentially crack free large cross section ceramic articles by injection molding techiques comprises the use of from about 0.1 v/o to about 10 v/o fibers with the ceramic injection molding formulation followed by the injection molding, binder removal and densification steps to form an essentially crack free densified large cross section ceramic article. The fibers are softened prior to the onset of densification and incorporated into the ceramic intergranular phase. This process eliminates the component distortion during densification which would have occurred if the fibers remained in the component.
Abstract:
A method of producing crack free ceramic parts having large cross-sections is disclosed. An initial mixture of ceramic powder containing a binder and from 0.1 v/o to 10 v/o of whiskers or fibers which are made of carbon, graphite or high temperature melting or decomposition point organic polymers. The mixture is either injection molded or slip cast to form a shaped article. The shaped article is heated in a nitrogen atmosphere to a temperature of 450 DEG C and then in an atmosphere of air at a temperature of 450 DEG C to 600 DEG C to completely remove the binder. The resulting binderless shaped article is then heated at 800 DEG C for a period of time sufficient to completely remove the whiskers or fibers from the shaped articles. The article is then encapsulated in glass and hot isostatically pressed at a pressure of 30,000 psi to densify the article to approximately 99 % of theoritical. The resulting article has a complex geometry and a large cross-section but without detrimental cracks.
Abstract:
A method of producing crack free ceramic parts having large cross-sections is disclosed. An initial mixture of ceramic powder containing a binder and from 0.1 v/o to 10 v/o of whiskers or fibers which are made of carbon, graphite or high temperature melting or decomposition point organic polymers. The mixture is either injection molded or slip cast to form a shaped article. The shaped article is heated in a nitrogen atmosphere to a temperature of 450 °C and then in an atmosphere of air at a temperature of 450 °C to 600 °C to completely remove the binder. The resulting binderless shaped article is then heated at 800 °C for a period of time sufficient to completely remove the whiskers or fibers from the shaped articles. The article is then encapsulated in glass and hot isostatically pressed at a pressure of 30,000 psi to densify the article to approximately 99 % of theoritical. The resulting article has a complex geometry and a large cross-section but without detrimental cracks.
Abstract:
A method for making essentially crack free large cross section ceramic articles by injection molding techiques comprises the use of from about 0.1 v/o to about 10 v/o fibers with the ceramic injection molding formulation followed by the injection molding, binder removal and densification steps to form an essentially crack free densified large cross section ceramic article. The fibers are softened prior to the onset of densification and incorporated into the ceramic intergranular phase. This process eliminates the component distortion during densification which would have occurred if the fibers remained in the component.
Abstract:
Un procédé permet de produire des pièces en céramique exemptes de fissures ayant une grande section transversale. A cet effet, on moule par injection ou on coule en barbotine un mélange initial de poudre céramique de manière à façonner un article. Le mélange initial de poudre céramique contient un liant et entre 0,1 v/o et 10 v/o de barbes ou de fibres en carbone, en graphite ou en polymère organique à température de fusion ou de décomposition élevée. On chauffe l'article ainsi façonné dans une atmosphère d'azote jusqu'à une température égale à 450 °C, puis dans une atmosphère d'air à une température comprise entre 450 °C et 600 °C afin d'éliminer tout le liant. On chauffe ensuite l'article ainsi obtenu dépourvu de liant à 800 °C pendant une durée suffisante pour éliminer entièrement les barbes ou les fibres de l'article façonné. On renferme l'article dans du verre et on le comprime isostatiquement à chaud à une pression de 30.000 psi afin de condenser l'article jusqu'à environ 99 % de ses dimensions théoriques. L'article ainsi obtenu a une géométrie complexe et une large section transversale mais est dépourvu de fissures nuisibles.
Abstract:
Un procédé de production d'articles en céramique de grande section transversale essentiellement sans fissures, par des techniques de moulage par injection, consiste à utiliser de 0,1 v/o environ à 10 v/o de fibres avec la composition de moulage par injection de céramique suivie des étapes de moulage par injection, d'élimination du liant et de densification pour former un article en céramique de grande section, densifié et sans fissure. Les fibres sont assouplies avant le début de la densification et elles sont incorporées dans la phase intergranulaire céramique. Ce procédé élimine la distortion des composants pendant la densification qui se produirait si les fibres demeuraient dans le composant.