US2996763A - Diamond material - Google Patents

Description

Aug. 22, 196 R. H. WENTORF, JR

DIAMOND MATERIAL Filed Jan. 31, 1956 A, r w te m 1 5 Q vJ/ MM 2 k m H w m Ufliw W??? Pat o 2,996,763 e DIAMOND MATERIAL Robert H. Wentorf, In, Schenectady, N.Y., assignor to General Electric Company, a corporation of New York Filed Jan. 31, 1956, Ser. No. 562,585 5 Claims. (Cl. 18-'47 .5)

This invention relates to radioactive diamond material and to the preparation thereof. More particularly, this invention is concerned with diamonds containing a'surface coating of a radioactive metal and to thepreparation thereof.

As is well known in'the art, natural diamonds,particularly natural diamonds of the industrial variety, readily acquire and retain a charge of staticelectricitv; This generally occurs when natural industrialdiamoi'rds come into contact with each other or with some other surface. The static charge on industrialdiamonds, results in a number of problems in their use; Thus, when an at-.' tempt is being made to sort industrial diamonds, it is The term"radioactive metal is used in the present ap plication in its usual sense to refer to a metal which has the property of spontaneously emitting-alpha, beta, of gamma rays by the disintegration of the nuclei of the atoms of the metal. As is well knowmthe'radiation emitted by radioactive elements causes ionization'of thef medium surrounding the radioactive material or theme-I Thus, where the diamond material of the present inveri-- tion acquires a static charge, the radioactivity-of the sur face layer of the diamond material causes ionization of the air or other medium surrounding the diamond mate} rial and this ionized air or other material carries away the static charge from the surface of the diamond mater.

found that the static charge seriously interferes withthe segregation of the diamonds into various size groups and interferes with the moving of the diamonds from one location to another. In addition, when natural diamonds are appliedin uses such as in bearings or ingrinding tools, the charge on the surface of the diamond tends to attract dust or other undesirable particles of matter to the surface of the diamond. "When diamonds are used as bearing materials such asin time pieces and other delicate mechanisms; the dust or other particles attracted by the static charge on the surface causes abrasion of that the static charge on the diamond surfacecauses particles of dust and of metal to adhere to the surface of the diamond and interfere with proper and accurate s s- An object of the present invention is toprovide a'diamond material which does not retain a charge of static electricity for any substantial period of time;

Another object of the present invention is to synthesize diamond material of the type described from nondiamond carbon.

These and other objects of my invention are accomplished by providing a radioactive diamond material comprising a diamond having a radioactive metal in adherent relation to the surface thereof. This radioactive diamond material is'formed by a method which: comprises subiecting non-diamond carbon to apressure of at least 75,000 atmospheres, e.g. from 85,000. to 110,000, and

rial, rendering the diamond'material electrically neutral.

As can be seen from the description of the ionization of the medium surrounding the diamond materials of the present invention and the discharging of the static charge on the diamond material, the diamond material of the present invention is free from the problems associated with natural diamonds. Thus, since the diamonds of the present invention do not retain a static charge, they may be sorted without the difliculty caused by any static charge on the material. In-addition, when the diamonds of the, present invention are used as bearings, they will have no tendency to attract dust or other abrasive particles to their surface. Furthermore, when the diamond mate-j rial 'of the presenfinve'htion is employed as abrasive material in abrasive wheels, there is again no tendency for any static charge to accumulate on the diamonds and therefore there is no tendency for the grinding wheel to attract particles of metal which may interfere withthe. accurate use of the grinding wheel,

In the copendin'g application of H. T. Hall et al., Serial No. 488,116, filed February 14, 1955, now abandoned,

, and assigned to the same assignee as the present invenpreferably about 95,000 atmospheres, at a temperature um, tantalum, manganese, and compounds of these metals which decompose to a metallic state under the conditions of thereaction. I 'My invention may be best understood 'by reference to the following detailed description take'n'in connection with the drawing in which: FIG. 1 is a front elevational view of a hydraulic press with ahigh temperature high pressure apparatus useful inthepractice ofthe present invention; FIG. 2 is an enlarged, exploded sectional view, of high temperature high pressure apparatus which is shown in FIG. 1; and FIG. '3 is an enlarged sectional view of the reaction vessel and associated parts which are shown in FIGS. 1

tion, there is described a method of making diamonds in which non-diamond carbon is subjected to a pressure of at least 75,000 atmospheres and preferably from 85,000 to 110,000 atmopheres, at a'temperature of from 1200 to 2000 C. in the presence of a catalyst which is a metal selected from the class consisting of group VIII; metals-of the periodic table, and chromium, sodium, tantalum, aluminum, manganese, and compounds of these metals which decompose to 'a metallic state under the conditions of the reaction. The process of the present in-I vention is carried out by the same method as' that described in the aforementioned Hall et al. application except that the reaction is carried out also in the presenceof a radioactive material.

The process of the present invention may be carried out many type of apparatus capable of producing the pressures requiredat the temperature required. However, I prefer to employ apparatus of the type described in the application of H. T. Hall, "SerialHNo- 488,050, filed February 14, 1955, nowabandoned, and assigned 1 to the same assignee as the present invention. The disof a hydraulic press.

of an annular member defining a substantially cylindrical reaction area, and two conical, piston-type members designed to fit into the substantially cylindrical portion of the annular member from either side of said annular member. A reaction vessel which fits into the annular member may be compressed by. the two piston members to reach the pressures requiredin the ractice of the present invention. The temperature required is obtained by any suitable means, such as, for example, by induction heating, by passing an electrical current ,thiough the reaction vessel, or by winding heating coils around the reaction vessel. j a

The apparatus of the aforementioned Hall application, Serial No. 488,050, is best described by reference to the accompanying drawing. In FIG. 1 of the drawing, a hydraulic press'comprises a base with a press bed 11 on which are mounted a plurality of vertical shafts 12 to support a carriage 13 with a hydraulic shaft 14. A pair of opposed, recessed pistons 15 and 16 on bed 11 and carriage 13 are recessed to partially position members 17 therein, each of which is provided with an electrical connection in the form of an annular conducting ring 18 with'a connector 19 to supply electric current from a source of power (not shown) through member 17 to the high pressure high temperaturereaction vessel which is described below. A layer of electrical insulation 20 is provided between at least one member 17 and its associated pistons 15 to prevent conduction of electrical current through the press. A pressure resisting member or belt .21 is positioned between opposed members 17 to provide a multi-staging pressure effect.

As is best shown in FIG. 2, each member 17 comp'rises a die 22 with surrounding binding rings 2'3 and 24. If desired, a soft steel safety ring 25 is located around binding ring 24. Conducting ring 18 is mounted around the periphery of safety ring 25 to conduct current through rings 25, 24 and 23 to die 22. Pressure resisting member 21, which is positioned between opposed" members 17, tapers inwardly towards its center to provide an aperture 26 in axial alignment 1Withopposed dies 22. Such a tapering effect produces greater strength in memberv 21 to resist pressure. Member 21 comprises an inner ring 27 surroundedby one or more binding rings 28, 29 and a soft steelsafety ring 30.

As is best shown in FIGS. 2 and-3', a-specimenholder 31, which is positioned in aperture 26 between dies 22',

washer of electrically insulating material is positioned around cylinder 33 between disks 32 to complete the assembly of specimen holder 31. If desired, specimen holder '31 may be in the form of a hollow'ca'sing which is 'in electrical contact with dies 22 but which is thermally insulated from inner ring 27. A washer 36 is positioned between each die 22 and its" associated disk 32v to provide a heat insulating core 37 with a surrounding outer conductive ring 38 in electrical contact with the die. A laminated conical gasket assembly 39 sur rounds each die 22 and comprises a pair of thermally and electrically insulating and pressure resisting conical washers 40 with a metallic washer 41- between adjacent washers 40. The outer pressure resisting, washer 40- is tapered inwardly to be engaged on-its exteriorsurface by the taperedsurface of inner ring 27 of member 21 and. on its interior surface by washer 35 .of-specimen' holder 31. While only a pair of washers-40 with a single separating washer 41 are illustrated in the drawing, it has been found that a plurality of alternate-washers further increases the size of specimen: holder 31, the permissible motion betweendies 2'2, and the pressure. Relatively high pressures are obtained wheninner washer 40 and metallic washer 41- are eliminated-and specimen holder 31 is shortened this corresponding thickness along the center line. However, pressures of the order of 40,000 to more than 100,000 atmospheres are produced when gasket'assembly 39 is employed through additional increases in both relative motion and compression. Ex-

amples of suitable materials from which core 37 and washers 35 and 40 may be catlinite.

' In the operation of the high temperature high pressure apparatus shown in FIGS. l-'3; each member 17 with associated conducting ring 18' and connector 19 is positioned partially Within the recesses of its associated pis-f ton in the press. Specimen 34 which is to be subjected to a high temperature high pressure environment is placed in reaction vessel 33 within washer 35 between disks 32 to complete the assembly of specimen holder '31. Pressure resisting member 21 is positioned between opposing'meinbers 17 to locate specimen holder 31 in aperture 26 betWCndisZZ.

Pressure" is applied to specimen 34 by shaft 14 of the press. At the same time electrical current is supplied from one electrical connector, such as upper connector 19 to upper conducting ring 13, rings 25, 24 and 23,- die 22, rim'38, and disk: 32 to' g'ene'rate heat and pressure sirnultaine'oiis ly in cylinder 33 of specimen holde'1" 3 1' The current path continues from cylinder 33 through lower disk' 32, v38, die 22, rings 23, 24 and 25, conducting'ring' 1'8, and connector 19 to the electrical source. Pressures in eiicess, of 95,000 atmospheres at tempera tures higher than 2000 Q. have been maintained in such apparatus for periods of hours.

The reaction vessel drcylinder 33, describedin- Hall application- Serial No. 488,050 referred to above,- may be formed of any of the" conventional materials of con; struction of of graphite. Where the reaction vessel is constructed of a; metal, it is convenient to employ'orie of the metals which acts as a catalyst in the present invention-. This vessel ne t er be filled with nondi'a'mo'nd carbon and a radioactive material and cam"; pressed so that the metal present in the vessel S l 1 as a catalyst" for thetra'nsformation to diamond. when the reaction chamber or vesselis formed of graphite, ig may be filledw'ith a mixture of the catalystmaterial the radioactive material and the compression of the; graphite vessel the catalyst and radioactive material at the pressures and temperatures required by the'present invention results in the transformation of the non diamond' carboii into the radioactive material of the present inventidn'. The reaction vessel or cham ber'may alsobe formed of a radioactive metal. Where this is-the case, the reaction vessel is filled with non-diamond -carb'o'naand catalyst material and compression ofthe reaction vesselat theproper pressure and temperature causes transformation of the non-diamond carbon into the radioactive material of the present invention.- Regardless of' the material-- of-- construction of the reaction vessel, the non-diamond carbon, the catalyst, and the radioactive material may be admixed inside the vessel; Thus, mixtures of powdered graphite, powdered catalyst; and powdered radioactive material may be employed-as a charge in' the reaction vessel and the compression: of the vessel and charge-at the required temperature effects transformation to radioactive diamond-material.

the preferred'embodiment of my invention, I employ a" reaction vessel 33 comprising a cylinder Qfgraphite having a' hollowed out-cylindrical center portion,--the aiiis ofthe center" portion being coaxial with the axis of the reaction yessel. Into this graphite reaction yes sel isplaced' cylinders'or disks of g'ra'phite, the catalyst, and' the radioactive material. v This reaction vessel is sealed at its endsby metallic disks'wh'ich may be'forriied of} any material or construction inert under ere-cams tiohsof the reaction'-orit may be formed of'a catalyst metal or a radioactiveniat erial. If desired, plugs of nail diamond carb'onor metal may be placed in the ends of the reaction vessel before sealing. This reaction vessel is then placed in the apparatus described in the above mentioned Hall application-Serial No. 488,050'and subject'ed to the elevated temperature and pressure re uired" to efiect the transformation to radioactive diamond ni'a made are pyrophyllite and curred.

sesame ferial.- Alternatively, insteadof employing a-reaction vessel, a cylinder of carbonaceous material, such as graphite, maybe sandwiched between two disks, each formed of a radioactive metal, this sandwich in turn being sandwiched between two other disks formed ofa metal which acts as a catalyst for the transformation. The sandwich is then placed in the high pressure apparatus and-subjected tothe conditions required to cause the transformation to radioactive diamond material. As a furtheralternative, a metallic reaction vessel may be filled with carbonaceous material in powder or solid form and the catalyst and radioactive material for the reaction may be supphed by'admixing it with the powderedcarbon or by forming end disks of either of these materials to seal the reaction vessel. This assembly is then subjected to the pressures and temperatures required. A reaction vessel may also be formed by compressing a mixture of nondiamond car-hon, catalyst, and radioactive material until a cylinder is formed which fits into the substantially cylindrical aperture described in the abovementioned Hall apparatus. Again, this latter apparatus may be employed in the usual manner at elevated -tem-' peratures and pressuresto effect the transformation to radioactive diamond materials 4 v p carrying out the-process of the present-invention, thetemperature in the reaction vessel may be measuredby. a thermocouple located adjacent the reaction-vessel previously mentioned. In carrying out this process, the timeof reaction required to convert the reaction mixture into radioactive diamond material may vary from a few seconds up to several minutesor more depending on the particular charge to. theireaction vesseL. However, regardless ..of. the .chargeto the-reaction vessel, 1 have found thattheradioactive diamond material of the pres ent invention isformed within two to five minutes. In stead of observing the time which the reaction vessel is maintainedfat. the reaction temperature, I may alternatively observe the progress of the reaction by the method described in the application of H. T. Hall, Serial No. 530,935, filed August 29, 1955, now'U.S. Patent 2,947,- 608, issued August 2, 11960, and assigned to the same assignee, asthe present invention. 'This Hall applica-' Inpreparing' the-radioactive diamond material of'the present invention, the proportions of the three ingredients employed are not critical, and I have found that suitable radioactive diamond material has been formed regardless of the relative concentrations of the non-diamond carbon, the catalyst, and the radioactive metal. However, in the preferred embodiment of this invention, it is preferred to havethe ingredients present in the proportions of -about six parts by volume of nondiamond carbon, six parts by volume of catalyst, and one part by volume of the radio'- active metal. Regardless of the proportions of ingredicuts and the physical location of the various ingredients in the reaction vessel, it has been found that the resulting product comprises diamond having in adherent relation to tion is hereby incorporated by. referenceinto the present application. By the process of this Hall application, the mixture of non-diamond carbon, catalyst, and radioactive material, is first subjected to a pressure of at least 75,000 atmospheres and subsequently sufficient heat is appliedto the mixture for sufficient time to cause an inflection in the electrical resistance of the mixture. 'When the inflection in'the electrical resistance. of the mixture occurs, the transformation of the mixture to the radio active diamond material ofthe present invention has 00- The radioactive materials which may be employed the practice of the present invention, include all of the naturally occurring radioact ive metals such as uranium, thorium, bismuth, rhenuium, lutecium, samarium, indiilm, rubidium and potassium. Also included within the radioactive metals employed in the practice-of the pres? ent invention may be mentioned the decay products of naturally radioactive materials as well as all of the well known radioactive isotopes of metals. Included within these latter two groups of radioactive materials may be mentioned, for example, the radioactive isotopes of protactinium, actiniurn, neptunium, plutonium, radium, francium, radon, cobalt, etc.

In addition to theradioactive isotopes specifically mentionedabove, it should be understood that otherartificial metallic isotopes are also included'within the scope of the present invention. As an illustration of other isotopes within the scope of the present invention, reference is made to all of those radioactive isotopes of metals listed in appendix 6 at page 464 of Nuclear Radiation Physics" by Lapp and Andrews, Prentice-Hall Inc., New York (1948).

the surface thereof a radioactive metal.

The thickness'of the radioactive layer on the outside of the diamond varies to a minor extent with the proportions of ingredients employed in the reaction. However, regardless ofthe proportions employed, I have found that the thickness of the radioactive metal layer lies within the range of about 0.5 to 5.0 microns. The relative weight of the diamond to the radioactive layer is dependent upon a number of factors, including the density ofztheradioactive' material, the concentration of the .reactants employed in forming thediamond material, and the size and shape ofv the diamonds. Because of these variables, it is impossible to specify an exact ratio of the weight of the carbon in the diamond. to the weight of the radioactive metal. However, I have obtained satisfactoryproducts where theratio of the weight of diamondto the weight of. radioactive metal toj: 20.- l, H The type and intensity of radiation emitted from the radioactive diamondrnaterial of the present invention is, of course, dependent upon the type of radioactive material employed. ...-Thus,. where the radioactive material em ployed "is thorium," th'e'"radiation from the radioactive diamond'mate'ria'l is that well known radiation emitted by thorium; Similarly; where the radioactive material is a material other than thorium, the radioactivity is that characteristic of-that other radioactive material. The half life of theradi'ation from the radioactive diamond materials is also dependent on the radioactive metal employed and is the sameas the half life of the radioactivity commonly observed from saidradioactive metal. J Since the radioactive materials of the present invention are similar to other radioactive materials, some degree'of care is necessary in handling the products of the present invention. The degree of care required in handling the radioactivediamo'ndmaterials is similar to that degree required in handling the radioactive metals themselves.

The followingfexamples are illustrative of the practice of myinvention and are not intended for purposes of limitation."- 'In the following-examples, the-reaction vessel consisted 'ofa cylindrical graphite member having a cylindrical aperture therethrough, the axis ofthe aperture being coaxial with that of the cylinder. The walls of the cylindrical-graphite member were approximately one-sixth as ithick as its diameter and the length of the cylinder was .approximately three-fifths the times of its outside diameter.

varied from about 10 Example 1 Into the reaction vessel described were placed two jn'ickel cylinders to act as a catalyst for the reaction, two thorium disks as the'radioactive metal, and one graphite cylinder which was to be converted to diamond. These reactants were assembled in the reaction vessel in the 'following order: a nickel cylinder, a thorium disk, the carbon cylinder, the second thorium disk, and the second nickel cylinder. The diameters of each of these rods'were substantially equal to the internal diameter of the reaction vessel and the length of each rod was selected so that there was present in the reaction vessel about 12 parts by 'volume of carbon, 12 parts by volume of nickel, and one 7 can b vo me f h r u e ac ion vesse h sealed a e d t a an a um ish an sub ected to a measur of abou 95,000 a m sphe es at tem erature of about 1500 C. for about six minutes. At the end of time the reaction vessel was allowed to cool, the pres: sure was released, and the radioactive diamond material w s parat m h ma x in hic it w orm d by solution of the matrix in fuming red nitric acid, From a measurement of the radioactivity of the diamond material, it was determined that the thorium content of the radioactive diamond material was approximately 5 per: cent by weight based on the total weight of the diamond material. This is equivalent to about 2.5 thorium atoms perthousand carbon atoms and represents a film about 0.75 micron thick of thorium on the surface ofthe dia-. mond. The fact that the thorium was present as a surface layer on the diamond was established by boiling the radioactive diamond material just described in aqua regia for 24 hours, after which time the diamond material exhibited no further radioactivity despite the fact that the appearance of the diamond material was unchanged.

Example 2 The procedure of Example 1 was repeated except that the ratio of the volume of the various reactants was as follows: 6 parts by volume of carbon, 6 parts by volume of nickel, and one part by volume of thorium. After the reaction vessel had been exposed to a pressure of about 95,000 atmospheres at a temperature of about i500 C. for five minutes, the resulting radioactive diamond material was isolated and found to have a radioactivity corresponding to 10 percent thorium by weight, which is equivalent to 5 thorium atoms per thousand atoms and represents a film of thorium about 1.5 microns hio Al h u h th c s n t e radioacti e mate ials which m be mp in th P act ce o the P esent i v n oh ha e deso boo onl ms? of p metals, it shoul b u r o h com ounds of those thetah h h d m ose und r he cond t ons of the react on m a b m l o us com ounds 9! a a st and of the radioactive metal which decompose into pure metal under the conditions of the reaction include, for example, the carbides, sulfides, carbonyls, cyanides, fer.- rotungstates, ferritungstates, oxides, nitrides, nitrates, hydrides, chlorides, molybdates, arsenates, acetates, oxalates, carbonates, borates, chromates, phosphates, phosphides, permanganates, silicates, sulfates, tungstates, etc. Speoifio mp of decomposable c m ounds sab e a oatalys i th P s n n i n ho'lhd ferrou sh fi i on oa h y p d u h ori o c romium a b de,

u t hstand s rsno r hi h oad at! whore tho u t Whioh ou d e s o hs! a with. wood l a i o d m n n s ot e ooths not 'Ihus, the radioactive diamond materials of the present vention are particularly suitable as jewels for use clocks, timers, and the like where dust might interfere t the a c ac the d ce What I claim as new and desire to secure by. Letters Patent of the United States is:

l. The method of synthetically making a radioactive diamond having a radioactivity only on the surface layer. thereof, which comprises (1) combining nonrdiamond carbon with a radioactive mctal and at least one metal diamond having a radioactivity only on the surface layer 8 thereof, which comprises (1) combining non-diamond carbon with thorium and at least one metal catalyst SQ? lected from the class consisting of group VIII metals of the periodic table and chromium, tantalum, manganese, and compounds of these metals which decompose to the metallic state under the following conditions of reaction, (2) subjecting such non-diamond carbon, thorium, and

I metal catalyst to a pressure of at least about 75,000

tantalum hydride, sodium fluoride, nickel permanganate,

cobal acetate, n k l lfa e o c- E 5 I. P. o rad ac i o c mp nd which ma be empl ed inclu o exam e u n m u id s h um ca bi e radium sulfates, etc.

- Although the above examples have described the reaction of the present invention only at a pressure of 95,000 atmospheres and a temperature of about 1500" C., it should be understood that any pressure inexcess of 75,000 atmospheresis satisfactory for the practice of invention. My preferred pressure range ii s from about 80,000 to 110,000 atmospheres. fiimila rly, my temperature range may vary from 1200 to 2000 Q, and preferably from about 1400 C. to 1800 Q. I

, e ra t m nd m te ia o e Pre en i ve t o is e u f l of ho e uses to wh h'd oh d n ommon out n a di on. rad ctive st ens material is particularly useful as the abrasive medium in an abrasive wheel. In addition, the radioactive diamond material of the present invention is particularly suitable o us s a h n u f e in a p cation Where th 7s atmospheres at a temperature of from about 1200 to 2000 6., and (3) recovering the formed radioactive diamond having radioactivity only on its surface layer.

3. The method of synthetically making radioactive diamond having a radioactivity only on the surface layer thereof, which comprises (1) combining non-diamond cafbon with a radioactive metal and nickel, (2) subjecting the said non-diamond carbon, radioactive metal, and nickel to a pressure of at least about 75,000 atmospheres at a temperature of from about 1200- to 2000 C., and (EU recovering the formed radioactive diamond having a radioactivity only on its surface layerl 4. The method of synthetically making radioactive dia' mond having a radioactivity only on the its surface layer thereof, which comprises (1) combining non-diamond carbon with thorium and nickel, (2 subjecting the combined non-diamond carbon, thorium, and nickel to a pressure of at least about 75,000 atmospheres, at a temperature of from about l200 to 2000 CL, and (3) isolating the radioactive diamond so formed having a radioactivity only on its surface layer. I 0' 5. The method of synthetically making radioactive diamond having a radioactivity only on the surface layer thereof, which comprises (1) combining non-diamond carbon with thorium and nickel, (2) subjecting this afore said non-diamond carbon, thorium and nickelto a pres sure of about 95,000 atmospheres at a temperatureof about 1500 C., and (3) thereafter recovering the radio; active diamond material so formed a radioacti vity o l o it surface la er- 4 (Other references on following page) UNITED STATES PATENTS Robbins June 7, 1930 Krusell Dec. 19, 1933 Ferris Apr. 6, 1943 Fruth Apr. 22, 1952 McKay May 11, 1954 Carlen Apr. 17, 1956 Hall Aug. 2, 1960 FOREIGN PATENTS Great Britain Aug. 9, 1917 Great Britain July 21, 1932 France Mar. 5, 1952 10 OTHER REFERENCES Neuhaus: Angew Chem, v01. 66, pp. 525-536, Sept.

Bradford: Radioisotopes in Industry, pp. 24, 84, 279,

5 Reinhold Publishing 00., New York City, 1953.

Kress: Chemie Ingenieur Technik, v01. 28, No. 3, pp. 141-152, March 1956.

Gunter et al.: Zanorg. Allgem. Chem, vol. 250,

0 pages 357-372 (1945).

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