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March 6, 1951 a 5, NEWTQN Eral 2,544,277 PREPARATION of URANIUM NITRIDE Filed June L2, 1945 Patented Mar

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March 6, 1951 a 5, NEWTQN Eral 2,544,277 PREPARATION of URANIUM NITRIDE Filed June L2, 1945 Patented Mar March 6, 1951 A_ 5, NEWTQN ErAL 2,544,277 PREPARATION OF URANIUM NITRIDE Filed June l2, 1945 Patented Mar. 6, 1951 2,544,277 UNITED STATES PATENT OFFICE 2,544,277 PREPARATION OF URANIUM NITRIDE Amos S. Newton and Oliver Johnson, Ames, Iowa, assignors to the United States of America as represented by the United States Atomic En ergy Commission Application June 12, 1945, Serial No. 599,067 y2 Claims. (Cl. 23-14.5) The invention relates to the preparation of a tion I8 and casing I9. Inlet tubes 9 and II uranium nitride. are attached to a source of ammonia, hydrogen, It is an object of the invention to provide a or other gaseous reactant to be used in the proc uranium nitride by the reaction of uranium either ess. Exhaust tube 8 leads to any suitable means in compound form or as a metal with ammonia for disposing of waste products exhausted dur or nitrogen. ing the process. The apparatus is formed of a It is a more speciñc object of the invention material which is resistant to the high tempera to provide a process for obtaining a pure product tures and corrosion resulting from the process. in which the uranium is prepared in reactable Heat resistant glass is suitable for this purpose. form in situ and subsequently reacted with am 10 The process may be carried out by preparing monia or nitrogen to form a uranium nitride. the uranium in reactable form in situ and then Further objects and advantages will appear reacting the uranium with ammonia to obtain from the following description and the drawing the desired uranium nitride. In such prepara referred to therein. tion of uranium, it is preferred that the uranium The drawing is a diagrammatic view in sec 15 be converted to uranium hydride by passing tion of an apparatus which may be used in car hydrogen over uranium metal at a temperature rying out the invention. _ of between 200° C. and 400° C. The uranium The invention resides in the preparation of a hydride is then reacted with ammonia in the uranium nitride by the reaction of uranium metal same apparatus. or uranium hydride with ammonia or nitrogen 20 In this embodiment of the invention, the preferably at relatively low temperatures, such uranium metal is cleaned with an acid, such as, as from 200° C. to 400° C. When uranium hy for example, GNHNOs, to remove surface irn dride is used it may be advantageous to prepare purities such as uranium oxides, uranium car such compound in situ, that is, in the same op bides, or the like, washed free of acid and then eration and apparatus in which the uranium 25 dried prior to reaction with ammonia. Where hydride is subsequently reacted with the am the uranium metal is not clean, the impurities monia or nitrogen to produce the desired remain in the reaction chamber and contaminate uranium nitride. the ñnal uranium nitride product. The clean The product provided by the invention has been uranium I, in the form of lumps, turnings, or shown by analyses on the basis of weight gain 30 the like, is placed in receptacle 2 and the dish in to have a formula corresponding approximate serted in reaction chamber 3. After assembling ly to UNM to UNms. which on calcinaticn at the apparatus, stopcock I2 is closed and stop about 140W C. loses nitrogen to the extent that cock I4 is opened. Hydrogen is then introduced the composition of the nitride becomes 13.3 grams into the reaction chamber through inlet tubes II of nitrogen per 238 grams of uranium instead of and ­I by opening stopcock I3. Sufficient hydro the expected 14.0 grams of nitrogen correspond gen is introduced into the system to complete ing to the molecular formula UN. 1y ñush out the reaction chamber. If desired, the A suitable apparatus for carrying out the in reaction chamber may be prepared by being vention is shown in the drawing in which urani evacuated through exhaust tube 8 with stopcocks um I is contained in a shallow receptacle 2 adapt 40 I2 and I3 closed and subsequently admitting ed to be inserted in reaction chamber 3. The hydrogen. reaction chamber is formed by reactor 4 which After the air in the reaction chamber has been may be of cylindrical form with one end 6 replaced by hydrogen, tube II is closed by stop terminating in inlet tube 1 and the other end 6 cock I3 and furnace I6 is placed into operation terminating in exhaust tube 8. Tubes 9 and II 45 to heat the uranium metal to a temperature of lead into inlet tube ‘I and, with exhaust tube 8, between 200° C. and 400° C. Preferably, the are provided with means for opening and clos temperature of the uranium is brought to ap ing the tubes such as stopcocks I2, I3, and I4. proximately 250° C. Stopcocks I3 and Id are Reactor 4 is surrounded by heating means such then opened and hydrogen introduced into the as a conventional resistance furnace I5 in which 50 reaction chamber 3 at substantially atmospheric resistance Wires I'I are placed inside of insula» pressure, the hydrogen reacting with the urani 2,544,277 3 4 um metal to form uranium hydride. While there hydride is prepared in situ from clean uranium is a tendency for the hydrogen to lower the metal. temperature of the uranium, the reaction is ex The uranium nitride may be obtained in ac othermic approximately 30,000 calories per mol cordance with the invention by directly reacting of uranium hydride being released to aid in main uranium metal with ammonia or nitrogen. The taining the temperature of the uranium. Pref uranium metal is cleaned with an acid, such as erably, an excess of between 20 per cent and 40 ' 6N HNOa to remove surface impurities. After per cent of hydrogen is used, the excess passing placing the metal in reaction chamber 3 with out of the reaction chamber through exhaust furnace I5 in operation, ammonia is passed tube 8. 10 through the reaction chamber with stopccck I3 If it is preferred not to use an excess of hydro closed and stopcock M open. As the tempera gen, the reaction may be carried out by introduc ture of the uranium increases to the most ing the hydrogen into the reaction chamber with favorable temperature for the reaction, that is, stop cock I4 closed. A slight hydrogen pressure between 200° C. to 400° C., the ammonia reacts from between one and three pounds is built up 15 with the uranium metal to form the uranium in the system and only an equivalent amount nitride. i As it is formed, the nitride tends to of hydrogen is used to form the uranium hydride. coat the uranium metal thereby retarding fur As the reaction proceeds, the uranium hydride ther reaction by preventing contact between the is formed as a powder on the uranium metal. If metal and the ammonia. The yield may be in uranium is in the form of a metallic mass, the 20 creased by agitating the uranium metal with uranium hydride tends to Slough off as it is suitable means to remove the formed nitride and formed thereby exposing additional metal for thereby expose a surface of fresh uranium metal the reaction. This continues until substantially to ammonia or nitrogen for further reaction and all of the uranium is converted to uranium formation of said nitride. hydride. In one specific example of the process, 9.35 After the uranium has been converted to grams of uranium hydride was placed in the uranium hydride, the hydrogen inlet is closed bottom of reaction chamber 3. The uranium by stopcock I3 and ammonia or nitrogen is ad hydride was heated for 2 hours and 15 minutes mitted through inlet tube 9 by opening stopcock at 250° C., and a substantial excess of ammonia I2. Preferably, a substantial excess of either oi’ ' was introduced into the reaction chamber dur these gases is used during the reaction to insure ing the heating. >Thereafter the furnace was conversion of all the uranium to the nitride. shut off, the apparatus cooled and disassembled, During the introduction of the ammonia or and approximately 9.9 grams of uranium nitride, nitrogen, it is preferred that stopcock I4 is open UNrss, were removed. On heating the product so that these gases will sweep out any hydrogen thus obtained at about 1400° C. for one hour a remaining in the reaction chamber or given off nitride having the composition UN was secured. by decomposition of the uranium hydride dur Uranium mononitride, formed by the process of ing the nitriding reaction. this invention, is a steel-gray powder which is The temperature of the uranium hydride and exceedingly fine and has a bulk density of 3.4 of the reaction chamber during the introduction 40 'g./cc. rl`he absolute density of the product, de of the ammonia or nitrogen and its reaction with termined by immersion in hexane is 11.3 g./cc. said hydride is maintained between 200° C. and The resistivity of the powder measured without 400° C. by resistance furnace I6. A major por compression is about 200 ohm-cm. compared tion of the uranium nitride is formed at a tem with 0.47 ohm-cm. for the hydride and 108 ohm perature between 250° C. and 300° C. A portion cm. for the oxides. The composition UN is suit of the uranium hydride may tend to decompose ably identi?ied by means of its distinctive crystal at this temperature into uranium metal and lattice which is shown by X-ray diffraction to hydrogen, with the liberated hydrogen being have a sodium chloride type structure and is a swept out of the reaction chamber by the arn-y 50 face-centered cubic phase containing 4 uranium monia.
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