Claims
- 1. A process for producing ferromagnetic chromium dioxide comprising:
- (a) adding chromium trioxide in water to form a slurry containing approximately 2.5 to 5 parts of chromium trioxide per part of water by weight;
- (b) adding to said slurry approximately 0.2 to 0.5 equivalents of an organic reducing agent per equivalent of chromium trioxide, said organic reducin agent, having a carbon backbone of at least C6 and maintaining the temperature below approximately 90.degree. C. while agitating the slurry until 30% to 80% of the organic reducing agent reacts with and reduces Cr.sup.+6 in the chromium trioxide to form a paste containing mixed intermediate chromium valences that are soluble therein;
- (c) heating the paste to a temperature above approximately 110.degree. C. but below a temperature at which chromium dioxide begins to form, at which temperature the remaining reducing agent from step (b) reacts with Cr.sup.+6 in the chromium trioxide and the mixed intermediate valences produced in (b): and
- (d) further heating the paste to a temperature of approximately 300.degree. C. to 400.degree. C. under a pressure of approximately 300 to 400 atmospheres to form ferromagnetic chromium dioxide.
- 2. The process of claim 1 wherein the weight ratio of chromium trioxide to water forming said slurry is in the range of 3.0-3.6 to 1. by weight.
- 3. The process of claim 1 wherein the organic reducing agent has a C6 to C12 backbone and a polar group selected from the group consisting of ketone, alcohol, acid, and amine.
- 4. The process of claim 3 wherein the reducing agent also functions as an antifoaming agent.
- 5. The process of claim 3 wherein the reducing agent is selected from the group consisting of 1-octanol, 2 -octanol, decanol, dodecanol, cyclohexanone, dodecylamine, octanoic acid and oleic acid.
- 6. The process of claim 5 wherein said reducing agent is added in the ratio of 0.25 to 0.4 equivalents per equivalent of CrO.sub.3 .
- 7. The process of claim 6 wherein the temperature of said slurry of step (b) is maintained in the range of 50.degree. to 80.degree. C. during the formation of paste.
- 8. The process of claim 7 wherein the reducing agent is octanol.
- 9. The process of claim 1 wherein ferromagnetic chromium dioxide with a desired aspect ratio in the range of 6 to 12 is obtained.
- 10. The process of claim 9 wherein the reducing agent is octanol.
- 11. A process for producing ferromagnetic chromium dioxide comprising:
- (a) adding chromium trioxide in water to form a slurry containing approximately 2.5 to 5 parts of chromium trioxide per part of water by weight:
- (b) adding to said slurry approximately 0.2 to 0.5 equivalents of organic reducing agent per equivalent of chromium trioxide, of which reducing agent
- (i) up to 40% is a C.sub.2 to C.sub.5 primary organic acid, and
- (ii) the remainder has a carbon backbone of at least C.sub.6 and maintaining the temperature below approximately 90.degree. C. while agitating the slurry until 30% to 80% of the organic reducing agent reacts with and reduces Cr.sup.+6 in the chromium trioxide to form a paste containing mixed intermediate chromium valences that are soluble therein;
- (c) heating the paste to a temperature above approximately 110.degree. C. but below a temperature at which chromium dioxide begins to form, at which temperature the remaining reducing agent from step (b) reacts with Cr.sup.+6 in the chromium trioxide and the mixed intermediate valences produced in (b); and
- (d) further heating the paste to a temperature of approximately 300.degree. C. to 400.degree. C. under a pressure of approximately 300 to 400 atmospheres to form ferromagnetic chromium dioxide.
- 12. The process of claim 11 wherein the primary organic acid is acetic acid.
- 13. The process of claim 12 wherein acetic acid provides approximately 10 to 25% of the combined reducing equivalents.
- 14. The process of claim 13 wherein the organic reducing agent having a carbon backbone of at least C6 is octanol.
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. patent application Ser. No. 845.733 filed Mar. 28, 1986 now abandoned.
US Referenced Citations (6)
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
845733 |
Mar 1986 |
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