Method for producing ceramic oxide compounds

• US 5,407,618 A
• Filed: 08/13/1990
• Issued: 04/18/1995
• Est. Priority Date: 08/13/1990
• Status: Expired due to Fees

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Stephenson, Ronald R.
• Primary Examiner(s): DERRINGTON, JAMES H
• Application Number:
  US07/566,557
• Time in Patent Office: 1,709 Days
• Field of Search: 264/65, 264/63, 264/61, 264/164, 264/211.11, 501/12
• US Class Current: 264/623
• CPC Class Codes: C04B 35/622 Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
• CPC Class Codes: C04B 35/624 Sol-gel processing

Abstract

A process is provided for preparing ceramics which can be produced into any predetermined shape by way of gel precursors.

Claims

1. A method for preparing a ceramic in a predetermined shape and form, comprising the steps of:

(a) providing a solution of polyhydroxy organic chelating agents and salts of metals contained in said ceramic of a predetermined composition, each of said salts being present in an amount necessary to provide the respective predetermined stoichiometric amount of a metal required in said ceramic;

the counterions of each metal ion, or the hydrolysis products of said counterions, in said solution of salts being decomposable;

(b) heating said solution to hydrolyze and polymerize said metal salts in said solution to a mixed-metal oxide precursor of said ceramic;

(c) adding organic acid and/or water to said precursor and heating to evaporate solvent and to form said precursor into a flexible, ductile, handleable gel;

(d) forming said gel into said predetermined shape and form;

(e) firing said formed gel in the presence of oxygen at a temperature and for a period of time sufficient to volatilize any remaining vapors and organic materials to form said ceramic.

2. A method according to claim 1 wherein said metal salts of said metals are selected from the group consisting of carbonates, nitrates, hydroxides, formates and acetates.

3. A method according to claim 1 wherein said metals are selected from the group consisting of lanthanum, strontium, chromium and manganese.

4. A method according to claim 1 further comprising the step of adding a sintering aid and/or glass former to said gel of step (c).

5. A method according to claim 4 wherein said glass former is selected from the group consisting of P₂ O₅, PbO and B₂ O₃.

6. A method according to claim 4 wherein said sintering aids are selected from the group consisting of silicon nitride and silicon carbide.

7. A method according to claim 1 wherein said gel in step (d) is extruded into discontinuous fibers.

8. A method according to claim 1 wherein said gel in step (d) is drawn into continuous fibers.

9. A method according to claim 1 wherein said step (e) of firing said heat-set gel is conducted at a temperature in the range of about 600°

-900°

C.

10. A method according to claim 9 wherein said step (e) of firing said gel is conducted at about 875°

C.

11. A method for preparing a flexible, ductile, handleable precursor of a lanthanum-strontium-chromium-manganese metal oxide, the oxide having the formula La_1-x Sr_x Cr_1-y Mn_y O₃, comprising the steps of:

(a) providing a solution of polyhydroxy organic chelating agents and salts of the lanthanum, strontium, chromium, and manganese metals contained in the metal oxide of a predetermined composition, each of said salts being present in an amount necessary to provide the respective predetermined stoichiometric amount of a metal required in the metal oxide;

the counterions of each metal ion, or the hydrolysis products of the counterions, in the solution of salts being decomposable;

(b) heating the solution to hydrolyze and polymerize the metal salts to form a polymerized product;

(c) adding organic acid and/or water to the polymerized product, and

(d) heating after adding the acid and/or water to evaporate the solvent and to form the flexible, ductile, handleable precursor.

12. A method according to claim 11 wherein said metal salts of said metals are selected from the group consisting of carbonates, nitrates, hydroxides, formates and acetates.

13. A method according to claim 11 further comprising the step of adding a sintering aid and/or glass former to said precursor formed in step (c).

14. A method according to claim 13 wherein said glass former is selected from the group consisting of P₂ O₅, PbO and B₂ O₃.

15. A method according to claim 13 wherein said sintering aids are selected from the group consisting of silicon nitride and silicon carbide.