US1759454A - Uranium metal and product and process of making the same - Google Patents

Description

Patented May 20, 1930 UNITED STATES PATENT or'r cs JOHN ALLEN HEANY, on NEW HAVEN, connncrrcu'r, assxenoa; Bx MESNE ASSIGN- mrs, 'ro ABGTU'BUS name TUBE company, or NEWARK, NEW JERSEY, A coa- POBATION OF DELAWARE 'UIB-AIITUI METAL AND PRODUCT AND PROCESS OF MAKING- THE SAME .lo Drawing.

This invention relates to uranium metal alloys and the process for making the same. More specifically, the invention relates to uranium alloys suitable for use in thermionic tubes for radio reception or X-ray production.

Generally stated, the invention consists in a process of manufacturing a metal materlal,

the essential part of which is the element uranium. The uranium generally appears in the completed material as an alloy or as a very intimate mixtureof the metal with a refractory reinforcing element. The invention also involves the utilization of the material 1 as an electron emitting body for radio tubes, X-ray tubes, and the like.

Having consideration for the uses to which the newmetal may be applied, such as filaments for radio tubes, it is of interest to note that heretofore either the metal tungsten or tungsten combined in a suitable manner with thorium has been used to give the necessary electron emission for detection and amplification in radio reception. The disadvantage in the'use of tungsten has. been the necessity for a relativelyhigh-temperature in order to get the proper volume of electron emission.

The employment of the metal thorium as an alloy or mixture with tungsten or a coating of thorium oxide on the surface of tungsten filament has resulted in an electron emission of considerably higher value for the temperature used, and filaments of this type have largely replaced filaments of pure tungsten.

One of the objects of the present invention is to provide a filamentary body which may be used for radio tubes, for example, which has a higher rate of electron emission for a given temperature not only than pure tungsten, but

40 also than that from the thoriated filaments.

Another important object is to provide a filament ofhigh electron emission which possesses also a high melting point, so that danger of burning out in the process of manu- 5 facture and in use is largely eliminated, and

Application filed October 22, 1925. Serial No. 64,255.

so that further the filament may be operated at any temperature at which it gives maximum efliciency. Other objects relate to the Iprovision of means for providing a highly efc1ent detector and amplifying tube for radio receiving apparatus; the provision of an uranium alloy which is ductile so that it may be readily drawn to any desired size; the provision of an alloy which may be readily worked into sheet or tube form for use in a thermionic tube or as an externally heated ionizer; and other objects such as will appear on consideration of the following description of one method of producing the alloy.

A method of manufacturing the alloy which I have found satisfactory for the production of filaments for radio tubes will now be described, in which I employ molybdenum metal alloyed with uranium. Finely divided molybdenum metal is mixed with uranium oxide in such proportion ,as to produce approximately 2% by weight of the total mixture of uranium metal after reduction of the oxide. For example, to make a finished slug suitable for swaging and wire drawing eight inches long and nine-thirty-second inches square, I take about 56 grams of molybdenum metal and about 1 grams of uranium oxide. This mixture is placed in a jar or ball mill and thoroughly mixed by this mechanical 75 method for a period varying from one to several hours. This mixture is then pressed into slug form by means of a hydraulic press in which a very considerable and heavy pressure is employed. Should the percentage of ingredients and the pressure permit, the slug may be placed at once in the electric furnace for reduction, but where there is some fragility in the slug, I may. sinter the same at a bright red temperature and in a hydrogen at mosphereprior to the reducing operation.

With the slug properlycompacted and suf- I ficiently strong to permit handling, I insert the same in an electric furnace which usually takes the form of a chamber having electric period of 10 minutes, and in a subsequent period of 10 minutesthe amperage is increased from 300 amperes to 1150 amperes. In a further period of 10 minutes, the amperage is held approximately constant at 1150 amperes and thereafter for a period of 2 minutes, the current is gradually reduced to zero. temperatures involved in this heating may vary from room temperatures to a point ap- -proximately equal to the temperature 010- tained at 92% of the current required to cause fusion or melting of the slug; that is, to a point sufliciently high to cause reduction of the uranium oxide. The result of the process is a mixture or alloy of molybdenum wlth uranium, the mass being welded or fused together in one solid metallic unit which 1s capable of being mechanically worked.

Subsequent to the reduction process, the slug is swaged by one of the usual hot swaging processes, The usual method employed is to heat the slug in an electric furnace consisting of a tube of alundum or porcelain surrounded by a heating coil and a heat insulating cover of magnesite, silica or other suitable material held by a suitable shell of asbestos. fibre brick. sheet iron, or the like. An inert gas, such as hydrogen, is passed through the furnace and the slug is alternate- 1y heated in this furnace and forced through the dies of a swaging machine, thus bringing about a gradual .reduction in the diameter of the material until fine wire filamentary elements are obtained. Heating and swaging employed in the treatment of the prepared slug will vary in accordance with the requirements of the .specific mixture employed.

The process as above described is limited to the mixture of molybdenum and the uranium oxide. Obviously, a similar process may be employed .where' tungsten or oxides other than uranium, or where other compounds of uranium, are used. Also, I have found that the percentage of uranium in the alloy to produce a material satisfactoryfor thermionic tubes, is not critical, but values varying from 2 to 10% give very good results.

Where an alloy made of molybdenum and uranium is employed for the filaments of radio tubes, exceptionally good results are obtained inasmuch as the high electron emission of alloys and compounds containing The necessities of a high vacuum for radio tubes makes the use of this alloy exceedingly advantageous, inasmuch as the addition of mo lybdenum as the principal constituent partv of the alloy with its relatively high melting point temperature makes possible the high temperatures necessary for flashing, bombarding and other processes incident to the construction of radio tubes. Moreover, the high melting point of molybdenum is a safe guard against destruction of the filament during use, arising from accidental impression on the filament circuit of an over-voltage.

Another important advantage in the use of molybdenum with uranium is that molybdenum is a highly ductile metal and is capable of easy adaptation to manufacturingprom esses, such as the formation of small coils of wire of exceedingly small diameter.

While I have described the invention as applied particularly to use in radio tubes, it is possibly of valuable use in X-ray tubes and other devices wherein a high electron emission is desired. The relatively higher emissive properties of uranium over thorium, for example in conjunction with the relatively higheruranium weight serves to make the alloy metal exceedingly advantageous for such uses, especially where combined with a refractory supporting metal which will permit usual manufacturing operation without diminishing the value of the properties of the uranium metal itself.

Moreover, while I have described the process and product as pertaining specifically to the alloy, it is apparent that by a constant repetition of the reducing step with added quantities of the oxide, approximately pure uranium may be produced which may be used as filaments for radio tubes and similar uses. Such filaments may be of pure urani-' um or of tungsten or molybdenum coated with uranium.

Modifications and uses of the invention other than those specified, may be made by those skilled in the art, but the disclosure should be understood as illustrative rather than definitive, as indicated in the claims hereunto appended.

Having thus described my invention, what I claim is: I 1. An alloy of uranium and molybdenum, theuranium not exceeding 5% of the constituents of the alloy.

2. A material having high electron emissivity, said material being formed of an alloy of molybdenum and uranium, the uranium forming approximately 3% of the alloy.

3. The process of making an alloy of ura'nium and another metal, which consists in mixing the uranium in the form of an oxide with the constituent alloy metal, both substances o cooling said heated slug, the heating bein in powdered form; pressing the mixture 1n the form of a solid slug adapted to be positioned between the electrodes of an electric power source; heating the slug from room temperatures to a temperature suflicient to cause reduction of the oxide during a time interval approximating 20 minutes; holding said maximum temperature for a period a proximating 10 minutes; and subsequent y of the slug taking place in an atmosphere 0 hydro:

en. In testimony whereof, I aflix my signature.

JOHN ALLEN HEANY.