Abstract:
The disclosure concerns self-supporting ceramic structures, including ceramic composite structures embedding a filler, and methods of making them. The ceramic structures comprise a polycrystlline material made by oxidation of a body of molten parent metal with an oxidant. The polycrystalline material has a first region substrate surmounted by a terminal region stratum which is integral with the first region. The terminal region stratum which is harder and of denser, finer crystalline structure than the first region substrate and is formed in a reaction stage subsequent to the reaction stage in which the first region of polycrystalline material is formed. Growth of the first stage is attained by by attenuating or interrupting the transport of molten parent metal to the first region under conditions which nonetheless leave or maintain therein enough oxidizable molten parent metal to form the polycrystalline material of the terminal region.
Abstract:
A method is provided for producing a self-supporting ceramic body comprising a polycrystalline material comprised of the oxidation reaction product of a parent metal (10) and having therein one or more channels which inversely replicate the geometry of a configured fugitive metal (6). The method includes providing an assembly of the configured fugitive metal (6) and the parent metal (10), optionally including a bed of permeable filler (4), and heating the assembly to form a body of molten parent metal. The molten parent metal is oxidized under selected conditions to grow the polycrystalline material to engulf the configured fugitive metal (6) (and to infiltrate the filler (4), if the filler (4) is present) and to cause the fugitive metal (6) to disperse into the engulfing polycrystalline material thereby leaving behind as the one or more channels the space formerly occupied by the configured fugitive metal (6). The method provides self-supporting ceramic bodies having therein one or more channels inversely replicating the shape of the configured fugitive metal (6).
Abstract:
The disclosure concerns self-supporting ceramic structures, including ceramic composite structures embedding a filler, and methods of making them. The ceramic structures comprise a polycrystlline material made by oxidation of a body of molten parent metal with an oxidant. The polycrystalline material has a first region substrate surmounted by a terminal region stratum which is integral with the first region. The terminal region stratum which is harder and of denser, finer crystalline structure than the first region substrate and is formed in a reaction stage subsequent to the reaction stage in which the first region of polycrystalline material is formed. Growth of the first stage is attained by by attenuating or interrupting the transport of molten parent metal to the first region under conditions which nonetheless leave or maintain therein enough oxidizable molten parent metal to form the polycrystalline material of the terminal region.
Abstract:
A method is provided for producing a self-supporting ceramic body comprising a polycrystalline material comprised of the oxidation reaction product of a parent metal (10) and having therein one or more channels which inversely replicate the geometry of a configured fugitive metal (6). The method includes providing an assembly of the configured fugitive metal (6) and the parent metal (10), optionally including a bed of permeable filler (4), and heating the assembly to form a body of molten parent metal. The molten parent metal is oxidized under selected conditions to grow the polycrystalline material to engulf the configured fugitive metal (6) (and to infiltrate the filler (4), if the filler (4) is present) and to cause the fugitive metal (6) to disperse into the engulfing polycrystalline material thereby leaving behind as the one or more channels the space formerly occupied by the configured fugitive metal (6). The method provides self-supporting ceramic bodies having therein one or more channels inversely replicating the shape of the configured fugitive metal (6).
Abstract:
A method of producing self-supporting ceramic bodies (10) having a modified metal-containing component includes first providing a self-supporting ceramic body (10) comprising (i) a polycrystalline oxidation reaction product (12) formed upon oxidation of a molten parent metal precursor with an oxidant, and (ii) an interconnected metal-containing component (14) at least partially accessible from one or more surfaces (15) of said ceramic body (10). The surface or surfaces (15) of the ceramic body (10) is contacted with a quantity of foreign metal different from said interconnected metal-containing component (14) at a temperature and for a time sufficient to allow for interdiffusion, whereby at least a portion of said metal-containing component (14) is displaced by said foreign metal. The resulting ceramic body, having an altered metal-containing component, exhibits modified or improved properties.
Abstract:
A method of producing self-supporting ceramic bodies (10) having a modified metal-containing component includes first providing a self-supporting ceramic body (10) comprising (i) a polycrystalline oxidation reaction product (12) formed upon oxidation of a molten parent metal precursor with an oxidant, and (ii) an interconnected metal-containing component (14) at least partially accessible from one or more surfaces (15) of said ceramic body (10). The surface or surfaces (15) of the ceramic body (10) is contacted with a quantity of foreign metal different from said interconnected metal-containing component (14) at a temperature and for a time sufficient to allow for interdiffusion, whereby at least a portion of said metal-containing component (14) is displaced by said foreign metal. The resulting ceramic body, having an altered metal-containing component, exhibits modified or improved properties.