Abstract: Macroporous ceramics were produced using the droplets of an emulsion as the templates around which the ceramic is deposited through a sol-gel process. Subsequent aging, drying and calcination yields a ceramic with pores in the range of 0.1 to several micrometers which have been left behind by the droplets. The unique deformability of the droplets prevents cracking and pulverization during processing and allows one to obtain porosities in excess of 74%. By starting with a monodisperse emulsion (produced through a repeated fractionation procedure) pores with a uniform and controllable size have been obtained. Self-assembly of these droplets into a colloidal crystal leads to ceramics which contain ordered arrays of pores. A wide range of porosities is obtainable with the advantages of low-temperature sol-gel processing, with a high degree of control and low cost.

Abstract: Macroporous ceramics were produced using the droplets of an emulsion as the templates around which the ceramic is deposited through a sol-gel process. Subsequent aging, drying and calcination yields a ceramic with pores in the range of 0.1 to several micrometers which have been left behind by the droplets. The unique deformability of the droplets prevents cracking and pulverization during processing and allows one to obtain porosities in excess of 74%. By starting with a monodisperse emulsion (produced through a repeated fractionation procedure) pores with a uniform and controllable size have been obtained. Self-assembly of these droplets into a colloidal crystal leads to ceramics which contain ordered arrays of pores. A wide range of porosities is obtainable with the advantages of low-temperature sol-gel processing, with a high degree of control and low cost.

Abstract: Macroporous ceramics were produced using the droplets of an emulsion as the templates around which the ceramic is deposited through a sol-gel process. Subsequent aging, drying and calcination yields a ceramic with pores in the range of 0.1 to several micrometers which have been left behind by the droplets. The unique deformability of the droplets prevents cracking and pulverization during processing and allows one to obtain porosities in excess of 74%. By starting with a monodisperse emulsion (produced through a repeated fractionation procedure) pores with a uniform and controllable size have been obtained. Self-assembly of these droplets into a colloidal crystal leads to ceramics which contain ordered arrays of pores. A wide range of porosities is obtainable with the advantages of low-temperature sol-gel processing, with a high degree of control and low cost.

Abstract: A hybrid CMC laminate is comprised of alternating layers of dense ceramics and fiber reinforced CMCs. The strategy involves the use of strong and stiff ceramics in order to delay the onset of cracking within the CMC layers. To provide protection from mechanical abrasion, improve thermal conductivity and inhibit oxygen ingress into the CMC layer, ceramic layers are placed on the outer surfaces of laminate. The laminate is produced by stacking alternating layers of dense ceramic and binderless layers of fiber reinforced CMCs, and then hot-pressing them together. The volume fractions of the constituent layers and the fiber architecture can be readily varied through this process. Reinforcement architecture (unidirectional vs. crossply) and the relative volume fractions of the phases effects the tensile and flexural properties of the laminates.

Abstract: A hybrid CMC laminate is comprised of alternating layers of dense ceramics and fiber reinforced CMCs. The strategy involves the use of strong and stiff ceramics in order to delay the onset of cracking within the CMC layers. To provide protection from mechanical abrasion, improve thermal conductivity and inhibit oxygen ingress into the CMC layer, ceramic layers are placed on the outer surfaces of laminate. The laminate is produced by stacking alternating layers of dense ceramic and binderless layers of fiber reinforced CMCs, and then hot-pressing them together. The volume fractions of the constituent layers and the fiber architecture can be readily varied through this process. Reinforcement architecture (unidirectional vs. crossply) and the relative volume fractions of the phases effects the tensile and flexural properties of the laminates.

Abstract: A surface-strengthened composite ceramic material has a ceramic matrix and a refractory phase dispersed at least in and close to the surface of the matrix. The refractory phase includes beta-alumina particles in which larger cations producing a larger molar volume replace sufficient smaller cations in beta-alumina particles in and close to the surface of the composite ceramic material to cause compressive surface stresses which increase the surface strength of the composite ceramic material. The smaller cations are replaced by the larger cations after firing of the composite ceramic material.

Abstract: Improved Si.sub.3 N.sub.4 /ZrO.sub.2 composite ceramics are described, having low thermal conductivity and which are substantially free of surface spalling and material degradation. Such composites are produced by incorporating an additive, e.g. MgO, CaO or Y.sub.2 O.sub.3, preferably Y.sub.2 O.sub.3, in suitable molar proporations based on ZrO.sub.2, and sintering the mixture with Si.sub.3 N.sub.4. In a preferred embodiment a powder mixture of 70% Si.sub.3 N.sub.4 and 30% ZrO.sub.2, by volume, and containing 6.6 mole percent Y.sub.2 O.sub.3 based on ZrO.sub.2, is formed and is sintered to produce a composite ceramic. The Y.sub.2 O.sub.3 is preferably pre-reacted with the ZrO.sub.2 to form a solid solution. A sintering aid, preferably Al.sub.2 O.sub.3, e.g. in an amount of about 2 to about 4%, by weight of the total mixture, can be added to permit production of the Si.sub.3 N.sub.4 /ZrO.sub.2 composite by pressureless sintering.