The present invention relates to an agglomerate abrasive grain made up of a plurality of individual abrasive grains which are bonded into an inorganic or organic binder matrix, wherein, based on the total weight of the agglomerate abrasive grain, at least 8% by weight of the abrasive grains which are bonded into the matrix are fused alumina-based polycrystalline alumina abrasive grains with a percentage of more than 97% by weight of alpha-alumina, and wherein the polycrystalline alumina abrasive grains, in turn, are made up of a plurality of Al.sub.2O.sub.3 primary crystals with a crystal size of between 20 μm and 100 μm. The agglomerate abrasive grain has a closed macroporosity with a pore volume of between 5% by volume and 30% by volume, wherein the average pore diameter of the closed macropores is between 10 μm and 100 μm and their maximum pore diameter is in the range of approx. 120 μm.

The present invention relates to the use of closed-pore microspheres of expanded perlite as a filler for producing moldings for the foundry industry, to a composition for producing moldings for the foundry industry, comprising closed-pore microspheres of expanded perlite as a filler, and a binder, the binder being selected from the group consisting of water glass, phenol-formaldehyde resins, two-component systems comprising as reactants a polyisocyanate and a polyol component containing free hydroxyl groups (OH groups), and starch, and also to moldings for the foundry industry and to a process for producing a molding for the foundry industry.

A ceramic joined body includes a first aluminum oxide-based sintered body, a second aluminum oxide-based sintered body, an aluminum oxide-based joint layer located between the first aluminum oxide-based sintered body and the second aluminum oxide-based sintered body, and an aluminum oxide-based protrusion connected to the aluminum oxide-based joint layer, where the average diameter for closed pores of the aluminum oxide-based projection is 0.8 times or more and 1.5 times or less as large as the average diameter for closed pores for each of the first aluminum oxide-based sintered body and the second aluminum oxide-based sintered body.

A ceramic joined body includes a first aluminum oxide-based sintered body, a second aluminum oxide-based sintered body, an aluminum oxide-based joint layer located between the first aluminum oxide-based sintered body and the second aluminum oxide-based sintered body, and an aluminum oxide-based protrusion connected to the aluminum oxide-based joint layer, where the average diameter for closed pores of the aluminum oxide-based projection is 0.8 times or more and 1.5 times or less as large as the average diameter for closed pores for each of the first aluminum oxide-based sintered body and the second aluminum oxide-based sintered body.

Ceramic composite materials that are reinforced with carbide fibers can exhibit ultra-high temperature resistance. For example, such materials may exhibit very low creep at temperatures of up to 2700 F. (1480 C.). The present composites are specifically engineered to exhibit matched thermodynamically stable crystalline phases between the materials included within the composite. In other words, the reinforcing fibers, a debonding interface layer disposed over the reinforcing fibers, and the matrix material of the composite may all be of the same crystalline structural phase (all hexagonal), for increased compatibility and improved properties. Such composite materials may be used in numerous applications.

Ceramic composite materials that are reinforced with carbide fibers can exhibit ultra-high temperature resistance. For example, such materials may exhibit very low creep at temperatures of up to 2700 F. (1480 C.). The present composites are specifically engineered to exhibit matched thermodynamically stable crystalline phases between the materials included within the composite. In other words, the reinforcing fibers, a debonding interface layer disposed over the reinforcing fibers, and the matrix material of the composite may all be of the same crystalline structural phase (all hexagonal), for increased compatibility and improved properties. Such composite materials may be used in numerous applications.

A method includes forming a ceramic member that has a plurality of closed pores within a ceramic matrix. The forming includes compacting a ceramic powder to form intra-particle pores between particles of the ceramic powder, and sintering the compacted ceramic powder to cause diffusion of the ceramic powder and formation of the ceramic matrix. The diffusion does not fill the intra-particle pores and leaves the closed pores.

A method includes forming a ceramic member that has a plurality of closed pores within a ceramic matrix. The forming includes compacting a ceramic powder to form intra-particle pores between particles of the ceramic powder, and sintering the compacted ceramic powder to cause diffusion of the ceramic powder and formation of the ceramic matrix. The diffusion does not fill the intra-particle pores and leaves the closed pores.

A porous refractory cast material contains a closed refractory aggregate fraction having a minimum particle size and a maximum particle size; the ratio of maximum particle size to minimum particle size is 10:1 or less. This closed refractory aggregate fraction comprises all of the porous refractory cast material having a particle diameter greater than 0.1 mm. The porous refractory cast material also contains a binder phase containing refractory selected from calcium aluminate cement, alumina phosphate, hydratable alumina, colloidal silica and combinations thereof. Also disclosed is a metallurgical vessel with an interior lining incorporating the porous refractory cast material.

Object To provide a liquid contact member having high hydrophilicity and exhibiting high dirt removal efficiency by cleaning. Solution A liquid contact member includes a ceramic including a plurality of crystal grains and a grain boundary phase, and the concentration of silicon on a liquid contact surface of the ceramic is higher than that of silicon on a virtual internal surface parallel to the liquid contact surface.