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US2872307A - Thorium-carbon alloys - Google Patents

Thorium-carbon alloys Download PDF

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US2872307A
US2872307A US78477A US7847749A US2872307A US 2872307 A US2872307 A US 2872307A US 78477 A US78477 A US 78477A US 7847749 A US7847749 A US 7847749A US 2872307 A US2872307 A US 2872307A
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thorium
carbon
metal
alloys
alloy
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US78477A
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Harley A Wilhelm
Robert E Rundle
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    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C43/00Alloys containing radioactive materials

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  • This invention relatesto; alloys .Qf;thriurn and carbon;
  • An object of this-inventionq- is to provide, a thoriumcarbonl alloy having a selected low. carbon content and;
  • a further object of this invention is. to provide a new composition of matter,- .namely,. thorium, monocarbide ('IhC).
  • a further object' of this, invention is, to. provide a thorium-carbon alloy wherein. the. carbon presentas a solid solution in thorium metal. is present in the-form of the compound, thorium monocarbide.
  • compositions of matter 'comprisingthe subject matter of this invention possess properties which-. make them useful in processes involving; nuclear bombardment under conditions peculiar to thosefound in chain-reacting piles.
  • the particular carbon content found in these compositions of matter imparts, tothemthe.- properties of increased hardness and resistance to corrosion from contact with hot, aqueous: solutions.
  • carbon is incorporated into thorium metal to produce the compound, thorium monocarbide, and mixtures consisting of thorium metal and thorium. monocarbide.
  • the thorium alloyvcomprisinggthe subject matter'of this invention contains; a carbon: content between;v 0.1; and4.9%. by weight: carbon. Generally, theihardness, values increase directly; with; theincrease ingcarbon content, and those thorium-carbon alloys containing between 0.1 and 2% by weight carbon are preferred. Alloys containing 0.1 to 0.5% carbon are especially preferred.
  • the alloys or compositions of matter comprising this invention are prepared by heating thorium metal with carbon at a temperature above the melting point of thorium, for example, at 1800 to 2000 C. in an inert refractory crucible.
  • the reaction may be carried out in a vacuum or in the presence of an inert gas, such as argon and helium, to prevent thorium oxide formation.
  • the carbon of a graphite vessel reacts with thorium in suificient quantity to introduce less than 0.1% carbon which occurs as carbide in the metal both as grain boundary and intergranular inclusions.
  • pure thorium is heated for a prolonged period of time above its melting point in a graphite crucible whereby thorium and graphite react to produce the alloys.
  • the carbon 2 content of the alloy is. determined by the :.time ofheat ing thorium in the cruciblefor a: particular temperature; The amount of carbon thereby introduced may;be.varied between 0.1.and4;9% by weight.
  • Thorium-carbontale loys of this invention having low carboncontents maybe prepared byfusingthoriumwith an appropriate amount ofcarbon in a, crucibleof, a refractory. oxide, such as .thoria, usingan, atomic hydro.- gen arc.
  • the fused alloy is obtainedbyany. of'thefore going. methods, it maybe water-quenchedor furnacecooledin an inert atmosphere from the reaction temperature.
  • carbon is soluble in thorium metal as a solid solution of thorium monocarbide.
  • carbon is soluble in thorium to the extent of less than 0.12%.
  • solubility limit for carbon in thorium is between 0.32 and 0.44% carbon, while at 1100 C., between 0.44 and 0.74% by weight carbon is invention.
  • the lattice parameter for pure thorium metal is 5074:0002 A. at 20 C., which value increases directly with an increase in the percent carbon present in the sample andthe temperature at which the alloy is heated and subsequently water-quenched. Such data indicate that the presence of carbon expands the crystal lattice structure of metal and furnishes additional evidence for the solid solubility of carbon in thorium.
  • Example I A sample of thorium metal was fused in an atomic hydrogen arc in the presence of carbon. The resultant product was ground and polished and an average hardness of 53 on the Rockwell A scale was measured. X- ray data revealed the presence of three phases, namely, thorium metal, thorium dioxide, and thorium monocarbide. Chemical analysis of this product show 0.34% carbon and 90% thorium. Photomicrogr'aphs showed the presence of a dendritic monocarbide pattern.
  • thorium metal was fused in a graphite crucible and the resultant product was found to contain 1.2% carbon and 98.5% total thorium (84.8% free thorium as determined by hydrogen evolution).
  • the average hardness was 62.1 on the Rockwell A scale which was equivalent to approximately 100 on the Rockwell B scale.
  • Example III A thorium-zinc metal biscuit was heated in an induction furnace to a temperature of 1850 C. under high vacuum in a graphite crucible in order to distill off the zinc impurity. When the vapor pressure had dropped to a low value, purified argon was introduced to prevent surface oxidation of the metal while cooling it.
  • the resultant metal contained 99% free thorium, 99.7% total thoriumand 0.09% carbon.
  • Example IV The pure thorium metal used in'this experiment was prepared by thevacuum distillation of zinc from a zincthorium alloy as in Example III.
  • a thorium-carbon alloy consisting essentially of 0.1 to 0.5 by weight carbon and thorium.
  • a binary thorium-carbon alloy consisting of thorium and about 0.3% by weight carbon.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Carbon And Carbon Compounds (AREA)

Description

United States Patent 6) 2,872,397. THORIUM-CARBON'ALLOYS Harley A. Wilhelm and Robert E Rundle, Ames, Iowa,
This invention relatesto; alloys .Qf;thriurn and carbon;
and-more. particularly tothoriumycarbon alloyshaving a low carbon content.
An object of this-inventionq-is to provide, a thoriumcarbonl alloy having a selected low. carbon content and;
preferably a thorium-carbonalloy containing theper,- centage of carbon within those certain; limits-WhichgWilL impart to the cast alloy properties; superior to those.
found inpure thorium metal.
A further object of this invention; is. to provide a new composition of matter,- .namely,. thorium, monocarbide ('IhC).
A further object' of this, invention is, to. provide a thorium-carbon alloy wherein. the. carbon presentas a solid solution in thorium metal. is present in the-form of the compound, thorium monocarbide.
Other objects and advantages of this invention will.
be readily apparent from thefollowingdescription of the preferred embodiments of this invention.
The compositions of matter 'comprisingthe subject matter of this invention possess properties which-. make them useful in processes involving; nuclear bombardment under conditions peculiar to thosefound in chain-reacting piles. The particular carbon content found in these compositions of matter imparts, tothemthe.- properties of increased hardness and resistance to corrosion from contact with hot, aqueous: solutions.
In accordance withpthist invention, carbon is incorporated into thorium metal to produce the compound, thorium monocarbide, and mixtures consisting of thorium metal and thorium. monocarbide. Thewmonocarbide and mixtures of thorium metal with thorium monocarbide I possess greater hardnessgand resistance:tocorrosiomt thorium metal alone.
The thorium alloyvcomprisinggthe subject matter'of this invention contains; a carbon: content between;v 0.1; and4.9%. by weight: carbon. Generally, theihardness, values increase directly; with; theincrease ingcarbon content, and those thorium-carbon alloys containing between 0.1 and 2% by weight carbon are preferred. Alloys containing 0.1 to 0.5% carbon are especially preferred.
The alloys or compositions of matter comprising this invention are prepared by heating thorium metal with carbon at a temperature above the melting point of thorium, for example, at 1800 to 2000 C. in an inert refractory crucible. The reaction may be carried out in a vacuum or in the presence of an inert gas, such as argon and helium, to prevent thorium oxide formation.
When using a graphite vessel in the casting of thorium, the carbon of a graphite vessel reacts with thorium in suificient quantity to introduce less than 0.1% carbon which occurs as carbide in the metal both as grain boundary and intergranular inclusions. However, in a method of preparing the alloys of this invention pure thorium is heated for a prolonged period of time above its melting point in a graphite crucible whereby thorium and graphite react to produce the alloys. The carbon 2 content of the alloy is. determined by the :.time ofheat ing thorium in the cruciblefor a: particular temperature; The amount of carbon thereby introduced may;be.varied between 0.1.and4;9% by weight. Thorium-carbontale loys of this invention having low carboncontents, such as 0.1 to 2%, maybe prepared byfusingthoriumwith an appropriate amount ofcarbon in a, crucibleof, a refractory. oxide, such as .thoria, usingan, atomic hydro.- gen arc.
After the fused alloy is obtainedbyany. of'thefore going. methods, it maybe water-quenchedor furnacecooledin an inert atmosphere from the reaction temperature.
We have discovered that castalloys ofjthorium, C0117 taining between 0.1' and 0.5 by weig'htcarbon are moretained in a 400-cc. beaker which was then covered with a Petri dish and heated in an autoclave by steam.atl-178= C. under apressure of125 lbs per square inch. At cer.-* min intervals, the specimens were removed from. the water, dried 'with acetone, weighed; and placed'back'irr the waterin, the autoclave for: continued 1 treatment: Table I summarizes thevextent of corrosion observed in a thorium alloy containing 0.3% carbon and in pure thorium metal.
' TABLET" Total Wt. Change mgJcmfi/hr.
Time in Test, hrs. v
Purellh The1data indicate that. the.loss in::weight; dueatoucorrosion of: purethorium is much, greaterythan'. the- IOSSTJOf V the thorium: alloy;
When alloys: of;- the.- present. inventionr ar,ewater: quenched. from" elevated temperatures; 6; g 1 C., the ;hardness.: of the alley: is determined: byvthe: carbon content. By increasing the carbon content the hardness of the alloy increases. However, it was found that by subsequent annealing of these water-quenched alloys at elevated temperatures, such as 700, 800, 900, and 1000 C., for six hours and followed by furnace-cooling, the alloys containing greater than 0.5% carbon lost substantial amounts of their hardness. In all cases these alloys still had hardness values greater than alloys containing' less than 0.5% carbon. The latter alloys exhibited substantially no change in hardness when subjected to this annealing treatment and they are accordingly alloys of relatively permanent hardness.
Apparently, carbon is soluble in thorium metal as a solid solution of thorium monocarbide. At 900 C., carbon is soluble in thorium to the extent of less than 0.12%. At 1000' C. the solubility limit for carbon in thorium is between 0.32 and 0.44% carbon, while at 1100 C., between 0.44 and 0.74% by weight carbon is invention.
soluble in thorium metal. These valuues expressed in percent by weight of thorium monocarbide would be:
At 900 C. 2.44% ThC At 1000 C. from 6.5 to 829% ThC At 1100 C. from 8.9 to 15% ThC carbide phase is identified by a face-centered cubic NaCltype structure having a lattice parameter a =5.29 A. Determinations of lattice parameter were determined by obtaining aback reflection pattern from ,a polished surface of the alloy sample. The lattice parameter for pure thorium metal is 5074:0002 A. at 20 C., which value increases directly with an increase in the percent carbon present in the sample andthe temperature at which the alloy is heated and subsequently water-quenched. Such data indicate that the presence of carbon expands the crystal lattice structure of metal and furnishes additional evidence for the solid solubility of carbon in thorium.
Example I A sample of thorium metal was fused in an atomic hydrogen arc in the presence of carbon. The resultant product was ground and polished and an average hardness of 53 on the Rockwell A scale was measured. X- ray data revealed the presence of three phases, namely, thorium metal, thorium dioxide, and thorium monocarbide. Chemical analysis of this product show 0.34% carbon and 90% thorium. Photomicrogr'aphs showed the presence of a dendritic monocarbide pattern.
Example ,11 j
A sample of thorium metal was fused in a graphite crucible and the resultant product was found to contain 1.2% carbon and 98.5% total thorium (84.8% free thorium as determined by hydrogen evolution). The X-ray diffraction pattern showed a lattice parameter for thorium a =5.094 A. and the thorium monocarbide lattice parameter 5.28 A., the monocarbide phase being a face-centered NaCl-type structure. The average hardness was 62.1 on the Rockwell A scale which was equivalent to approximately 100 on the Rockwell B scale. Examination of the microstructure showed carbide in the grain boundaries and some distribution of carbide throughout the crystal planes- Example III A thorium-zinc metal biscuit was heated in an induction furnace to a temperature of 1850 C. under high vacuum in a graphite crucible in order to distill off the zinc impurity. When the vapor pressure had dropped to a low value, purified argon was introduced to prevent surface oxidation of the metal while cooling it.
pended claims.
The resultant metal contained 99% free thorium, 99.7% total thoriumand 0.09% carbon.
A sample of this thorium metal, weighing 196.5 g., was heated in a beryllium oxide crucible with 0.492 g. of carbon to a temperature of 18 50 C. for fifteen minutes and subsequently water-quenched from this temperature. The average hardness value of the resultant thorium-carbon alloy was 93.9 on the Rockwell B scale. Chemical analysis showed 0.36% carbon. The X-ray diffraction pattern for the starting material showed a lattice parameter a =5.0835:0.0004 A., while the lattice parameter for the thorium-carbon product alloy was a =5.0887i0.0005 A.
Example IV The pure thorium metal used in'this experiment was prepared by thevacuum distillation of zinc from a zincthorium alloy as in Example III.
One hundred sixty-eight grams of the dezinced thorium metal containing 0.04% carbon was heated with 0.88 g. of carbon in a graphite crucible lined with beryllia to a temperatureof 2000 C. The temperature was lowered by passing argon into the system and at 1850 C. the carbon crucible containing the sample was quenched in water. Average hardness values on the Rockwell B scale measured 92.4 and the product contained 0.59% by weight carbon. The lattice parameter of the starting material which contained 0.04% carbon is equal to a =5.0794i0.0006 A., while the product lattice parameter was a =5.094i-0.0006 A.
The foregoing description presents the preferred embodiments of this invention 'in which are disclosed new and useful compositions of matter. Many alterations and changes, which will be apparent to those skilled in the art, may be made therein without departing from the spirit and scope of this invention as set forth in the ap- What is claimed is:
' 1. A thorium-carbon alloy consisting essentially of 0.1 to 0.5 by weight carbon and thorium.
2. A binary thorium-carbon alloy consisting of thorium and about 0.3% by weight carbon.
References Cited in the file of this patent FOREIGN PATENTS Great Britain JainS, 1942 OTHER REFERENCES Troost: Comptes- Rendus, vol. 116, pp. 1229-1230- Moissan et al.: Annales de Chimie et du Physlque,
' Series 7, vol. '12, p. 432 (1897).
Mellor: Inorganic and Theoretical Chemistry, vol. 7, p. 210 (1927), publ. by Longmans, Green & Co., London.

Claims (1)

1. A THORIUM-CARBON ALLOY CONSISTING ESSENTIALLY OF 0.1 TO 0.5% BY WEIGHT CARBON AND THORIUM.
US78477A 1949-02-25 1949-02-25 Thorium-carbon alloys Expired - Lifetime US2872307A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3044847A (en) * 1960-04-11 1962-07-17 David T Peterson Self-moderating fertile compounds
US3163609A (en) * 1961-03-16 1964-12-29 Minnesota Mining & Mfg Crystalline spherules

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB542410A (en) * 1939-02-14 1942-01-08 Alloys Ltd Improvements in method of production of powdered alloys or carbides

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB542410A (en) * 1939-02-14 1942-01-08 Alloys Ltd Improvements in method of production of powdered alloys or carbides

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3044847A (en) * 1960-04-11 1962-07-17 David T Peterson Self-moderating fertile compounds
US3163609A (en) * 1961-03-16 1964-12-29 Minnesota Mining & Mfg Crystalline spherules

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