System, method, and apparatus for conversion bonding of precursor subcomponents into a unitary monolith
View Patent ↗A process for converting precursor objects into a unitary ceramic object produces, for example, a ceramic, optical scan mirror that is formed from at least two pieces. An optical section has at least one optical surface and at least one attachment surface, and a support section has at least one attachment surface and preferably has a mounting area. The optical and support sections are formed as separate pieces from a precursor material, such as graphite, such that a selected support section can receive any of a plurality of optical sections having different sizes, shapes, or orientations. To form the mirror, the attachment surfaces are placed adjacent each other, and then the sections are converted simultaneously to a ceramic material, such as silicon carbide, to form a monolithic scan mirror.
1. A method of forming a monolithic structure of a ceramic material, the method comprising:
(a) forming a first graphite component, the first component having at least one surface and at least one attachment surface;
(b) forming a second graphite component, the second component having at least one attachment surface;
(c) assembling the first component with the second component in a selected orientation, the attachment surface of the first component being adjacent and in direct contact with the attachment surface of the second component; and
(d) conversion bonding the first component and the second component, wherein the conversion bonding converts the graphite in both the first component and the second component into silicon carbide by substituting a plurality of silicon atoms for a portion of carbon atoms in the graphite, and the first component and the second component are bonded into a unitary object formed as a monolithic structure.
2. A method according to claim 1 , wherein step (d) comprises converting the first and second components from graphite crystal structure to a larger crystal silicon carbide structure, such that grains grow across an interface between the first and second components.
3. A method according to claim 1 , wherein step (c) comprises defining a seam between the first and second components, and step (d) comprises eliminating the seam.
4. A method according to claim 1 , wherein step (d) comprises changing the attachment surfaces into a continuous phase of converted silicon carbide that combines the previously separate first and second components.
5. A method according to claim 1 , wherein step (c) comprises forming an interference fit between the first and second components having a range of separation of 0.001 to 0.005 inches.
6. A method according to claim 1 , wherein step (d) comprises reducing a thermal mass of the unitary object as it is converted.
7. A method according to claim 1 , wherein step (d) comprises substituting silicon atoms for approximately half of the carbon atoms in the graphite.
8. A method of forming a monolithic structure, the method comprising
(a) providing a plurality of graphite components having selected shapes and sizes, each component having an attachment surface;
(b) providing a plurality of graphite support sections having selected shapes and sizes, each support section having an attachment surface;
(c) selecting one of the components and one of the support sections according to an end-user application;
(d) assembling the component and support section in a selected orientation to form an assembly, the attachment surfaces of the component and support section being in direct contact with each other in an interference fit and defining a seam therebetween; and then
(e) conversion bonding the component and support section, wherein the conversion bonding converts the graphite of the component and support section into a different material by substituting a portion of carbon atoms in the graphite with a plurality of different atoms, and the component and support section are bonded into a unitary object comprising a monolithic structure and the seam is eliminated.
9. A method according to claim 8 , wherein the different material is silicon carbide, and step (e) comprises substituting silicon atoms for approximately half of the carbon atoms in the graphite.
10. A method according to claim 8 , wherein step (e) comprises converting the component and support section from graphite crystal structure to a larger crystal silicon carbide structure, such that grains grow across the seam between the component and the support section.
11. A method according to claim 8 , wherein step (e) comprises changing the attachment surfaces into a continuous phase of converted silicon carbide that combines the previously separate component and support section into the monolithic structure.
12. A method according to claim 8 , wherein step (d) comprises forming the interference fit between the component and support section in a range of separation of 0.001 to 0.005 inches.
13. A method according to claim 8 , wherein step (e) comprises reducing a thermal mass of the unitary object as it is converted.
14. A method of forming a monolithic structure, the method comprising:
(a) providing first and second graphite components, each having an attachment surface;
(b) assembling the first and second components to form an assembly, the attachment surfaces of the first and second components being in contact with each other in an interference fit and defining a seam therebetween; and then
(c) conversion bonding the first and second components, wherein the conversion bonding converts the graphite of the first and second components into silicon carbide by substituting a plurality of silicon atoms for a portion of carbon atoms in the graphite, and grains grow across the seam to bond the first and second components into a unitary object comprising a monolithic structure and the seam is eliminated.
15. A method according to claim 14 , wherein step (c) comprises substituting silicon atoms for approximately half of the carbon atoms in the graphite such that the first and second components combine from graphite crystal structure to a larger crystal silicon carbide structure.
16. A method according to claim 14 , wherein step (c) comprises changing the attachment surfaces into a continuous phase of converted silicon carbide that combines the previously separate first and second components into the monolithic structure.
17. A method according to claim 14 , wherein step (b) comprises forming the interference fit between the first and second components in a range of separation of 0.001 to 0.005 inches.
18. A method according to claim 14 , wherein step (c) comprises reducing a thermal mass of the unitary object as it is converted from graphite to silicon carbide.