US1467398A - Process of coating - Google Patents

Description

Patented Sept. 11, 1923..

EABZLE E. SCHUMACHER, OF EAST ORANGE, NEW JERSEY, ASSIGNOR '.l0 WESTERN ELECTRIC COMPANY, INCORPORATED, 013 NEW YORK, N. Y., A CORPORATION OF" \NEW xoax.

PROCESS OF COATING .80 Drawing.

To all whom it may concern:

Be itknown. that I, EARLE E. SCHU- tain new and useful Improvements in Processes. of Coatingyof which the following is a full, clear, concise, and exact description.

i This invention relates to electron dlscharge devices and pertains especially to the manufacture of thermionic cathodes therefor.

The object of this invention is'a processv of coating alkaline earthoxides on a core of oxidi'zable metal. P

This invention pr' vides for a coating of base metal cores wih thermionic material without an appreciable oxidation of the core.

The process of coating comprises the preparation of a'molten bath of an alkaline earth compound or a mixture of alkaline earth compounds at a moderate temperature, and

the dipping of the material to an instant in this bath. The coatin is thus applied to the core in the absence 0 air and the oxidation of the surface of the core is prevented. .WVhen the coating is heated it breaks down into the alkaline earth oxides which are highly active thermionically.

In the preferred form of the invention a bath-of molten barium hydroxide or a mixture of barium hydroxide with strontium or a calcium hydroxide is prepared by mixing one or more of these substances in'suitable quan- .tities in a vesseland heating the same to a temperature from about/450 to 750, degrees centigrade. At this term erature the substances have become melte in their water of crystallization and the material to be coated 40 is then merely dipped into this bath whereupon a firmly adherent coating is formed on the surface of the metal. It is found that,

by this particular process, base metals may be coated with a firm coating in the absence of air without the necessity of any electrolyt ic action.

In this method of dipping the filament in a bath of -molten hydroxide, it is probable that a very. small and negligible amount of the stable-compounds above mentioned are formed; yet, since the filament isnot heated in the air, there is a large excess of uncombined alkaline earth oxides present in the e coated for Application filed niarch 19, 1920. Serial No. 367,086.

coat and it'is to these uncombined oxides that the filament owes its activity.

A small amonnt'of oxidation of the'core is desirable in a 'di-pping process in that it imparts a rou h surface to the metal to which the-alk: in'e earth oxides will adhere more firmly. This partial oxidation may be brought about by either of two'methods: the

filament may be oxidized by a previous heating in the air or, the bath may be heated up to a temperature sufliciently high such as 600cent1grade so that it becomes an oxi- 5 dizing 'medium in itself due to the formationof a certain amount of barium eroxide.

By the above process thermionically active filaments havc'been made of cores of iron, tungsten, molybdenum, carbon and alloys of chromium or tantalum with various combi' nations of the other metals.

What isclaimed isz r 1.-A process of coating which com rises dipping a base metal core to be coate in a molten bath of alkaline earth hydroxide.

* 2. A process of coating which comprises heating a quantity of alkaline earth hydroxide in a ,vessel to a temperature where it be comes melted in its water of crystallization so and then dipping the material to be coated in the bath.

. 3. A process of coating which comprises heating abath of barium hydroxide to a temperature from about, 450 to 750 centi- 85.

rade and then dipping a base metal core 1nto the bath.

4. .A process of coating which comprises. heating a mixture ofalkaline earth hydroxides to a temperature from about 450,to 750 centigrade and then dipping a base metal core into the bath.

5. A process of coating which comprises dipping an electrode to be coated in a molten bath of alkaline earth hydroxide. I 6. Aprocess of coating which comprises dipping a filament to be coated in a molten bath of alkaline earth hydroxide.

7. 'A process of coatin which comprises heating an alkaline eart hydroxide to a we term erature from about 450 to 750 centi gra e and then dipping a base metal electrode therein.

In witness whereof, I hereunto subscribe myname this 10th day of March, A. D. 1920.

EARLE'E. SGHUMACI-IER.