Process for manufacturing a ceramic hollow body

Claim 2

A process for manufacturing a ceramic or ceramic oxide hollow body of a predetermined shape, comprising: providing a hollow mold core constructed from a material having a high thermal conductivity and thermal expansion coefficient as compared to said hollow body and having an outer wall surface non-adhering to said hollow body, said mold core having said predetermined shape and sufficient internal cooling to prevent damage to said core upon exposure to plasma temperatures; flame spraying non-aggregated, atomized particles selected from the group consisting of ceramic and ceramic oxide particles free of binding agents, through a hot plasma jet, on said mold core outer surface, to deposit a uniform coat of said particles on said outer surface while maintaining a predetermined temperature gradient across the wall of said mold core at the point of spraying; continuing internal cooling of said mold core and subjecting said coat of said particles to additional cooling action by a compressed gas jet to cause said particles to fuse into a hollow body layer; and separating said hollow body layer from said mold core.

Claim 3

The process of claim 1 wherein said hollow body layer has a thickness ranging between about 0.05 mm and 0.15 mm and the temperature gradient is less than 2° C./mm of the hollow body layer.

Claim 4

The process of claim 2 further comprising depositing successive coats of said particle on said mold core, cooling each of said coats until the ceramic layer has fused, removing loose unbound ceramic or ceramic oxide dust particles from each of said coats and performing said operation successively to form a hollow body having a thickness in excess of 5 mm.

Claim 5

The process of claim 3, wherein said uniform coats of said particles are formed by relative movement of said mold core and said plasma jet during said spraying.

Claim 6

The process of claim 4, wherein each of said particle coats is subjected to said compressed gas jet immediately prior to spraying another of said coats.

Claim 7

The process of claim 4, wherein said mold core is supported on a rotatable chuck attached to one end of a slidable carriage and wherein said uniform coats of said particles are deposited by simultaneously rotating said chuck and sliding said carriage in a direction parallel to the axis of said mold core, while spraying.

Claim 8

The process of claim 3, wherein said compressed gas jet is directed away from said plasma jet.

Claim 9

The process of claim 1, wherein said compressed gas is at a pressure greater than one atmosphere.

Claim 10

The process of claim 1, wherein said hollow mold core is made of metal.

Claim 11

The process of claim 9, wherein said metal is selected from the group consisting of copper, aluminum, an alloy of magnesium and aluminum, and an alloy of beryllium and aluminum.

Claim 12

The process of claim 9, wherein said mold core is an expanding mandrel having a longitudinal axis and wherein said hollow body is separated from said mold core by shrinking said mold core.

Claim 13

The process of claim 1, wherein said hollow mold core surface is made of a material selected from the group consisting of glass fibers, polytetrafluoroethylene and heat resistant textile tape.

Claim 14

The process of claim 1, wherein said compressed gas is selected from the group consisting of air, carbon dioxide and nitrogen.

Claim 15

A process for manufacturing a ceramic or ceramic oxide hollow body of a predetermined shape, comprising: providing an internally cooled hollow mold core constructed from a material having a high thermal conductivity and thermal expansion coefficient as compared to said hollow body, and having an outer wall surface non-adhering to said hollow body, said mold core having said predetermined shape; flame spraying non-aggregated atomized particles selected from the group consisting of ceramic and ceramic oxide particles free of binding agents on said mold core outer surface, through a hot plasma jet, to deposit a uniform coat of said particles on said outer surface, while maintaining a temperature gradient across said coated mold wall of less than about 2° C./mm of coated wall thickness; continuing internal cooling of said mold core and subjecting said coat of said particles to additional cooling action by a compressed gas jet to cause said particles to fuse into a hollow body layer having a thickness of between about 0.05 and 0.15 mm and to remove non-adhering ceramic or ceramic oxide particles; immediately after subjecting said coat to said cooling action of said compressed gas, spraying additional ceramic or ceramic oxide particle coats on said hollow body layer; repeating successive coatings of said particles and removal of non-adhering ceramic or ceramic oxide particles to form a hollow body having a wall thickness in excess of about 5 mm; and separating the hollow body from the mold core.

Claim 16

A process for manufacturing a ceramic or ceramic oxide hollow body of a predetermined shape, comprising: providing an internally cooled hollow mold core constructed from a material having a high thermal conductivity and thermal expansion coefficient as compared to said hollow body, and having an outer wall surface non-adhering to said hollow body, said mold core having said predetermined shape; flame spraying non-aggregated atomized particles selected from the group consisting of ceramic and ceramic oxide particles free of binding agents on said mold core outer surface, through a hot plasma jet, to deposit a uniform coat of said particles on said outer surface, while maintaining a temperature gradient across said coated mold wall of less than about 2° C./mm of coated wall thickness; continuing internal cooling of said mold core and subjecting said coat of said particles to additional cooling action by a compressed gas jet to cause said particles to fuse into a hollow body layer having a thickness of between about 0.05 and 0.15 mm and to remove non-adhering ceramic or ceramic oxide particles; immediately after subjecting said coat to said cooling action of said compressed gas, spraying additional ceramic or ceramic oxide particle coats on said hollow body layer; repeating successive coatings of said particles and removal of non-adhering ceramic or ceramic oxide particles to form a hollow body having a wall thickness in excess of about 5 mm; and separating the hollow body from the mold core.