US2569225A - Method of forming uranium monocarbide - Google Patents

Description

Patented Sept. 25, 1951 METHOD OF FORMING URANIUM MONOCARBIDE James H. Carter, Blacksburg, Va., and Adrian H. Daane, Ames, Iowa, assignors to the United States of America as represented by the United States Atomic Energy Commission N Drawing. Application March 26, 1947, Serial No. 737,430

metal and carbon.

It is an object of this invention to provide an efiicient process for the preparation of uranium monocarbide.

Other objects and advantages of this invention will be readily apparent from the following del0 scription of preferred embodiments of our invention.

Broadly stated, it is well-known in the art that uranium and carbon may be heated in comminuted contact with each other at an elevated temperature for a sufficient time to form uramum-carbon compounds or alloys. These temperatures are in excess of the melting point of uranium; and the compound thus produced contains a composite mass of uranium dicarbide (U02) and uranium sesquicarbide (U 03).

In accordance with an embodiment of the present invention the existence of another specific uranium carbide, uranium monocarbide,

is established by metallographic examination of a mass produced by contactin uranium and carbon in stoichiometric proportions at a temperature less than the melting point of the uranium metal.

The solubility of carbon in solid uranium is less than in the liquid phase which occurs at a temperature in excess of 1125 C. The solubility of carbon in solid uranium has been experimentally determined. The solubility of carbon in the gamma phase, wherein the temperature of the solid metal is in excess of 770 C. is of the order of 0.05 percent (1 atom percent carbon). The uranium metal containing 0.05% carbon shows a substantial dissolution of the carbide when,

annealed approximately 96 hours at 1000 C. The 4 upper limit of the solubility of carbon in the betauranium within a temperature range of 660 C. to 770 C. is of the order of 0.03 percent (0.6 atom percent carbon) while in the alpha phase wherein the uranium metal is at a temperature less;

than 660 C. the solubility is not much greater than 0.01 percent (0.2 atom percent carbon).

In examining the metallographic crystal structure of the carbide formation in the uranium mass wherein the reaction temperature was kept below 1125 C. (melting point of uranium), a dendritic structure existed in the form of cubic faced-centered crystals (probably NaCl-structure), isomorphous with those of UN and U0.

According to observations, the carbon in uranium monocarbide can be replaced by Oxygen or nitrogen to give a slight decrease in the lattice constant (as low as 4.936 5. when U02 is found) and therefore the most reliable value of the lattice constant is the highest one obtained, primarily 4.951 A. The lattice constant of uranium monocarbide does not markedly depend upon the presence of an excess amount of uranium or carbon, thus indicating low solubility of both components in the carbide.

In examining the uranium carbon system, it shall be noted that evidence for the existence of a high temperature compound is somewhat slight, although Widmanstatten patterns of alloys between uranium sesquicarbide (U2C3) and uranium dicarbide (UCz) have been interpreted as indicating the existence of solid solutions of aUzCs and .pUCz. No carbides with more than two carbon atoms per uranium atom seem to exist although there is some X-ray evidence, however, for solubility of carbon'in the UCz lattice; particularly at temperature near the melting point (2375 C.) of the uranium dicarbide alloy.

The system diagram shows that where the stoichiometric proportions of carbon to uranium exceed 4.8% by weight of carbon there is a greater tendency to form the UCz structure and probably the U203 structure, depending on the temperature. When the stoichiometric percentage of carbon is reduced to less than 4.8% of carbon, the tendency of the reactive mass of uranium and carbon to form uranium monocarbide is enhanced; that is, at a temperature less than the melting point of the uranium metal (1125 C.).

A mode of preparing uranium monocarbide consists in mixing powdered uranium metal with powdered carbon in stoichiometric proportions wherein the carbon content is less than 4.8% of the composite mass content, then pressing the mixture into small blocks under high pressure, 20-50 tons p. s. i., for example, and then heating the pressed blocks in a temperature range less than the melting point of uranium, preferably at about 900-10009C. for about hours.

Another method of forming uranium monocarbide is to compositely mix comminuted uranium and carbon in stoichiometric proportions to form uranium monocarbide, and then pressing the mixture into small blocks under high pressures, about 50-100 tons p. s. i., for example, then heating the pressed blocks in a temperature range above the melting point of the uranium metal and less than the melting point of the uranium carbide produced, 2250 0., whereby a mixture of UCz and U203 is formed, and then quenching the composite mass to a temperature less than the melting point of the uranium metal at about 900 C. The carbon alloy thus formed will disproportionate into uranium dicarbide containing uranium monocarbide and carbon, independently 'of an excess "component in the melt.

In the foregoing process of producing uranium monocarbide, another embodiment consists "of heating uranium metal of high 'purity'content with carbon in a stoichiometric amount of: about 4.8 per cent at subatmospherio pressure at a temperature in excess of 1125 .C. and 'then quenching the uranium-monocarbide composition to a temperature of about 900 C.

In another embodiment of the present invention, it was found that uraniummono'c'ar'bide may be produced by heating uranium metal of high purity content with carbon in a stoichiometric amount of about 4.8 per cent by weight .in acar-bon dioxide atmosphere at a temperature between 900 C. and 1125 C.

:Numerous variations and modificationsin the preferred methods and examples described will be readily apparent andmay be made without departing from the spirit and scope of our inven- .tion as defined in the following claims.

This application is a continuation-in-part of .our co-pending application, Serial No. 549,282, filed August 12, 1944, now Patent No. 2,526,805.

The method of forming uranium monocarbide by heating uranium oxide andcarbon and the .product are the subject matter of Patent 'No. 2,448,479, .granted to Harley A. Wilhelm and .Adrian H. Daane on August 31, 1948.

What is claimed is:

1. The process of producing uranium monocarbide which comprises heating uranium metal in contact with carbon in approximately stoichi- .ometric amount at a temperature sufliciently high to react but below the melting point 'of uranium.

2. The processof producing uranium .imonocarbide-which comprises heating uraniummetal of high purity with carbon in a "stoichiometric ;amount of about 4.8% by weight in a carbon dioxide atmosphere at a'temperatureat between approximately 900C. and 1125 C.

3. A process of producing uranium monocarbide which comprises heating uranium in contact with carbon at a temperature in excess of the meltingpoint of uranium so 'as toform a uranium-carbon mass consisting essentially of uranium, U02 and U203 and then quenching and maintaining said mass at a temperature below the melting point of uranium but sufliciently high to form uranium monocarbide.

4. The process of producing uranium monocarbide which comprises heating uranium metal of high purity in contact with carbon at'a temperature in excess of the melting point of the .uranium metalso' as to form a uranium carbon alloy consisting essentially of uranium, Ucz'and UzCs, and then quenching and maintaining said alloy at a temperatureabove about'900 C.

amount of about 4.8% at a temperature in excess of the. melting point of uranium metal whereby --a mixture of uranium, UCz and U2C3 is obtained and then quenching and maintaining at a temperature "of about 900 C.

"I. The process of producing uranium monocarbide which comprises heating uranium metal of high purity with carbon in a stoichiometric amount of about 4.8% at sub-atmospheric -pressure at a temperature in excess of 1125 C. whereby a mixture of uranium, UCz and UzCa is obtained and then quenching and maintaining at a temperature of about 900 C.

8. A process for producing uranium monocarbide, comprising reacting a uraniumand carbon-containing mixture selected from the group consisting of a mixture of uranium plus carbon in about stoichiometric amounts and a mixture of uranium and U02 plus U203 in which the total uranium and the total carbon contents are present in approximately stoichiometric proportions by heating the mixture to a temperature sufficient to bring-about reaction but below the melting point of metallic uranium and maintaining said temperature for reaction and formation of uranium monocarbide.

9. A process for producing uranium monocarbide, comprising reacting a uraniumand carbon-containing mixture selected from the group consisting of a mixture of uranium plus carbon in which uranium is present in at least stoichiometric amounts and a mixture of uranium, UCz and U2C3 in which the total uranium is present in at-least stoichiometric proportions astonranium monocarbide by heating them-ixture to a temperature sufficient to bring about reaction but below the melting point of metallic uranium, and maintaining saidtempe-rature for reaction and formation of uranium monocarbide.

10. A process for producing uranium mono- .carbide, comprising reacting a mixture of uranium, UCz and U203 in which the total uranium is presentin at least stoichiometric proportions as to uraniummonocarbide by heating the mixture toa temperature suiiicient to bring'about reaction but below themelting point of metallic uranium and maintaining said temperature for reaction and'formation of uranium monocarbide.

JAMES H. CARTER. ADRIAN H. DAANE.

No references cited.

Claims (1)

1. 9. A PROCESS FOR PRODUCING URANIUM MONOCARBIDE, COMPRISING REACTING A URANIUM- AND CARBON-CONTAINING MIXTURE SELECTED FROM THE GROUP CONSISTING OF A MIXTURE OF URANIUM PLUS CARBON IN WHICH URANIUM IS PRESENT IN AT LEAST STOICHIOMETRIC AMOUNTS AND A MIXTURE OF URANIUM, UC2 AND U2C3 IN WHICH THE TOTAL URANIUM IS PRESENT IN AT LEAST STOICHIOMETRIC PROPORTIONS AS TO URANIUM MONOCARBIDE BY HEATING THE MIXTURE TO A TEMPERATURE SUFFICIENT TO BRING ABOUT REACTION BUT BELOW THE MELTING POINT OF METALLIC URANIUM, AND MAINTAINING SAID TEMPERATURE FOR REACTION AND FORMATION OF URANIUM MONOCARBIDE.